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11-15-2023 Agenda
HEARING EXAMINER AGENDA November 15, 2023 5:30 P.M. City Council Chambers 25 West Main Street I.PUBLIC PARTICIPATION Public Participation Information The City of Auburn Hearing Examiner Meeting scheduled for Wednesday, November 15, 2023, at 5:30 p.m. will be held in person and virtually. To attend the meeting virtually, please click one of the below links, or call into the meeting at the phone number listed below: Join Zoom Meeting https://us06web.zoom.us/j/86362123426 Meeting ID: 863 6212 3426 One tap mobile +12532050468,,86362123426# US +12532158782,,86362123426# US (Tacoma) Dial by your location •+1 253 205 0468 US •+1 253 215 8782 US (Tacoma) •877 853 5257 US Toll-free •888 475 4499 US Toll-free Meeting ID: 863 6212 3426 Find your local number: https://us06web.zoom.us/u/kxxwTQbLd CASE NO: CAO23-0010 APPLICANT/ PROPERTY OWNER: Allison Rothstein, Director of Land Entitlement and Development Mainvue Homes WA LLC 121 – 3rd Avenue Kirkland, WA 98033 AGENT: Thomas A. Barghausen, P.E. President Barghausen Consulting Engineers, Inc. 18215 – 72nd Avenue South Kent, WA 98032 REQUEST: Request for a Critical Areas Reasonable Use Exception pursuant to ACC 16.10.150 and ACC 16.10.080(G)(d) for Class IV Landslide hazard area within a previously approved preliminary Plat of Diamond Valley Estates(PLT14-0006) The plat consists of four parcels totaling approximately 79.45 acres and proposed for approximately 200 single family residential lots and ten tracts and associated clearing, grading, and construction of stormwater facilities, public streets, utilities, and landscaping. 1 of 350 Hearing Examiner Appeal Hearing Agenda November 15, 2023 5:30 p.m. ________________________________________________________________________________ 2 The project site contains wetlands, streams, and geologic hazard areas. The preliminary plat was approved under previous version of R-5, Residential Five Dwelling Units to the acre zoning standards. PROJECT LOCATION: The north and south sides of Evergreen Way SE between Quincy and Udall Ave SE. , within the SW ¼ of Section 32, T 21 N, R 5E, W.M. PROPOSED LOCATION: The project site is located on the north and south sides of Evergreen Way SE, between Quincy and Udall Ave SE, within the SW ¼ of Section 32-21-05 W.M. PARCEL NO(S): King County Parcel Nos.: 322105-9010, 322105-9011, 322105-9030 and 322105-9037 2 of 350 Reasonable Use Exception for the Preliminary Plat Of Diamond Valley Estates (Formerly, Park Ridge) CAO23-0010 I.GENERAL INFORMATION: Application Date:September 26, 2023 Applicant(s)/Allison Rothstein, Director of Land Entitlement and Development Property Owner(s):MainVue Homes WA LLC 121 - 3rd Ave Kirkland, WA 98033 Agent: Thomas A. Barghausen, P.E. President Barghausen Consulting Engineers Inc. 18215 72nd Avenue South Kent, WA 98032 Project Description: Request for a Critical Areas Reasonable Use Exception (RUE) pursuant to ACC 16.10.150 and ACC 16.10.080(G)(d) for Class IV Landslide hazard area within a previously approved preliminary Plat of Diamond Valley Estates (PLT14-0006). The plat consists of four parcels totaling approx. 79.45 acres and proposed for approx. 200 single-family residential lots and ten tracts and associated clearing, grading and construction of stormwater facilities, public streets, utilities, and landscaping. The project site contains wetlands, streams, and geologic hazard areas. The preliminary plat was approved under previous version of R-5, Residential Five Dwelling Units to the acre zoning standards. Location: The north and south sides of Evergreen Way SE between Quincy and Udall Ave SE. , within the SW 1/4 of Section 32, T 21 N, R 5E, WM, King Co. Parcel Nos. 322105-9010, 322105-9011, 322105-9030 and 322105-9037 Proposed Location: The project site is located on the north and south sides of Evergreen Way SE, between Quincy and Udall AV SE, within the SW ¼ of Section 32-21-05, W.M. Parcel Numbers: King County Assessor’s Parcel No's: 322105-9010, -9011, -9030 & - 9037 3 of 350 EXHIBIT 1 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 2 Subject Property and Adjacent Property Land Use designation, Zoning Classification, and Current Use: Comprehensive Plan Map Designation Zoning Classification Current Land Use Site Single-Family Residential / Vacant R-5 Residential (5 du/ac) Vacant except for developed right-of- way of Evergreen Way SE North Single-Family Residential R-5 Residential (5 du/ac)Vacant South Unincorporated Pierce County City of Auburn – Potential Annexation Area Unincorporated Pierce County - Moderate Density Single Family Residential Zone Single-family residential / Vacant Moderate Density Single Family Residential (MSF) Single Family Residential West Single-Family Residential R-7 Residential (7 du/ac)Single-family residential East Single-Family Residential R-5 Residential (5 du/ac) and Planned Unit Development (under former code section, now repealed) Single-family residential List of Exhibits Exhibit 1 - Staff Report Exhibit 2 - Vicinity Map Exhibit 3 - Completed Application form Exhibit 4 – Excerpt of Final Environmental Impact Statement (FEIS) for Kersey III, pages i through vii, Preliminary Plat, City of Auburn, February 11, 2005. (A full copy of the Final Environmental Impact Statement (FEIS) for Kersey III Preliminary Plats dated February 11, 2005 is avaible upon request.) Exhibit 5 - Written Statement / Reasonable Use Justification Narrative, Barghausen Consulting Engineers, Inc., September 25, 2023. Exhibit 6 - “Steep Slope Areas Exhibit”, Barghausen Consulting Engineers, Inc., September 1, 2023, (Referred to as Exhibit 1 in the Applicant’s Justification Narrative) Exhibit 7 - “Geotechnical Engineering and Geomorphology Services for Diamond Valley Estates ,” study GeoEngineers April 21, 2016, (Referred to as Exhibit 2 in the Applicant’s Justification Narrative) Exhibit 8 - “Geotechnical Evaluation – Reasonable Use Exception, Proposed Diamond Valley Estates, 18XX Evergreen Way SE”, Earth Solutions Northwest (ESNW) September 15, 2023, (Referred to as Exhibit 3 in the Applicant’s Justification Narrative) Exhibit 9. - “RUE Grading Exhibit for Diamond Valley Estates”, Barghausen Consulting Engineers Inc., September 12, 2023, (Referred to as Exhibit 4 in the Applicant’s Justification Narrative) Exhibit 10 - “Diamond Valley Estates Conceptual Grading Plan” APEX Engineering PLLC for PLT14-0006, July 11, 2016, (Referred to as Exhibit 5 in the Applicant’s Justification Narrative) Exhibit 11 - “Staff Report for the Preliminary Plat of Diamond Valley Estates —PLT14-0006”, Pages 25-32, City of Auburn, January 12, 2017, (Referred to as Exhibit 6 in the Applicant’s Justification Narrative) Exhibit 12 - “Hearing Examiner Final Decision on Preliminary Plat of Diamond Valley Estates, Findings of Fact, 4 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 3 Conclusions of Law” February 8, 2017, (Referred to as Exhibit 7 in the Applicant’s Justification Narrative) Exhibit 13 – “Final Plat of Forest Glen” King County Recording Number 20200309000474, Volume 291, Page 9. (City of Auburn File No. PLT19-0008) Exhibit 14 – “Memorandum to City – Diamond Valley Estates Preliminary Plat – Revised Preliminary Plat – Revised Preliminary Design for Minor Adjustment”, Keith Goldsmith, Goldsmith Engineering, November 30, 2022 Exhibit 15 – “Drawing Comparison of Original Prel. Plat & Proposed Minor Amendment Property Lines, Diamond Valley Estates”, Goldsmith Engineering, October 2022 Exhibit 16 – Cover Letter Transmitting Application, Thomas Barghausen to City, September 26, 2023 Exhibit 17 - Notice of Public Hearing & Affidavits of mailing, posting, and publication 5 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 4 Map showing adjacent zoning designations: II.SEPA STATUS: A Determination of Significance (DS) was issued for the Project as part of a previous larger development proposal involving multiple property owners. A Draft Environmental Impact Statement was issued by the City of Auburn on July 1, 2004 (File No. SEP00-0004). After observance of a 45-day public comment period, a Final Environmental Impact Statement was issued on February 11, 2005. The document was titled: “Final Environmental Impact Statement for the Kersey III Preliminary Plat”. The proposed Action evaluated in the Environmental Impact Statement involves the development of a low-density preliminary plat of 481 dwelling units or a higher density 700 dwelling unit development on an approximately 170-acre site located in the southerly portion of the City of Auburn. The 700-unit alternative would be developed under the city’s Planned Unit Development (PUD) regulations, while a portion of the 481-unit alternative would require PUD approval. The project consisted of seven (7) undeveloped forested parcels. The project will be governed by, among other regulations, the City of Auburn zoning and subdivision ordinances. Open space and sensitive areas would be provided or protected as required by the City of Auburn sensitive area regulations of the time. Certain portions of the site will not be developed due to steep slopes, wetland and power line corridors. The project’s proposed construction will consist of three (3) divisions and six (6) phases (2 divisions for each phase). The proposal includes approximately 620,000 cubic yards of earthwork, which is expected to remain on the development site. The proposal will require the on-site and off-site installation of new public facilities to serve the development, to include water, storm sewer and sanitary sewer lines. On-site storm facilities include wet ponds for detention and water quality treatment. The proposal also requires the dedication of land for use as a public park. 6 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 5 The proposal requires the dedication and construction of approximately four (4) miles of new public rights of way to serve the development and provide internal circulation. The improvements include internal streets and a new arterial connection from the existing terminus of Evergreen Way SE (off- site to the west) east across the site to Kersey Way SE. A public meeting on the environmental impact statement process was held on July 28, 2004 from 4:00 to 8:00 pm at the Lakeland Community Center. The current proposal is approximately a third of the originally contemplated development and generally remains within the scoped amount and configuration of development anticipated. The current property owner proposes some changes such as converting what were previously proposed as open stormwater ponds to underground stormwater vaults and reducing the length of time and extent of grading. The project changes generally reduce the extent of impacts. III. FINDINGS OF FACT: General/Background/history 1. An Environmental Impact Statement was required for the Kersey Ill preliminary plats proposal, originally proposed in 2000. The Draft and Final EIS addressed the subject property, plus the adjoining two properties to the east that are now developed. Two total development potentials for this area were analyzed in the EIS documents; one for 481 total dwelling units, the other for 700 dwelling units covering all properties. As noted, the current proposal involves 200 dwelling units (lots) for approximately one third of the area addressed in the EIS. The other two-thirds were developed with approximately 373 dwelling units. The Draft EIS was issued on July 1, 2004, with the Final EIS being issued on February 11, 2005. There were no appeals. A public meeting on the environmental impact statement process was held on July 28, 2004 from 4:00 to 8:00 pm at the Lakeland Community Center. The first two eastern divisions or subdivisions of the project evaluated in the EIS submitted applications and proceeded through the city approval process and were rezoned to Planned Unit Development (PUD) and each received preliminary and final plat approvals, construction completed, and homes were subsequently constructed. The subject property as the third division (Kersey III, Division 3) located to the west did not submit applications to the City and was not rezoned to PUD prior to the City’s repealing this former code section (ACC 18.69, Planned Unit Developments). So, an application to rezone to 7 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 6 PUD was not filed prior to the city’s adoption of Ordinance No. 5991 (April 17, 2006) repealing this former code section and eliminating the PUD code provisions (ACC 18.69). 2.For this earlier two divisions of this larger project, the applicants, Wayne Jones of Lakeridge Development and Joyce & Peter Bowles, requested a change in zoning to the Planned Unit Development (PUD), approval of a Planned Unit Development (PUD), and preliminary plat approval for Kersey Ill, Division 1 & 2. Kersey Ill Division 1 was a 169-lot single-family residential subdivision of a 50.85-acre site located west of Kersey Way at approx. 53rd St. SE. Kersey Ill Division 2, was a proposed 204 lot single-family residential subdivision located on an adjacent 38.46-acre parcel abutting the western boundary of Division 1. Although owned separately, the two projects were processed concurrently and agreed to share common open space and recreational amenities. Division 1 lot sizes average 5,032 sq. ft. in size, with an average lot width of 50 ft. The smallest lot was proposed to be 3,985 sq. ft. in area. The overall project density is 3.32 dwelling units per acre. Since the project is proposed as a PUD, smaller lot sizes than typical zoning standards are allowed. The minimum standards for lots within a single-family density PUD are contained in ACC 18.69.070 (subsequently repealed). The Division 2 lot size averages 5,127 sq. ft. in area, with an average lot width of 40 ft. The smallest lot was proposed as 3,999 sq. ft. in area. Overall project density is 5.30 dwelling units per acre. Collectively, the two projects consist of 373 dwelling units at an overall density of 4.17 units per acre. Temporary cul-de-sacs and utility services would need to be provided to ensure that each phase can stand-alone pursuant to Auburn City Code (ACC) Section 18.69.110. 3.Recommended mitigation measures are included beginning on Page 9 of the Final EIS. Per the mitigation measures of the Kersey Ill Final EIS, no homes may be constructed until Evergreen Way SE is extended from its current eastern terminus within Lakeland Hills east to Kersey Way at 53rd ST. SE. The Applicants entered into an agreement with each other and the owner of property to the west (the future Kersey Ill, Division 3) regarding the construction of Evergreen Way SE. A traffic signal will be installed at the 53rd ST. SE intersection and the 53rd ST. SE approach will need to be reconfigured to eliminate the current angular intersection. The EIS recommended development of this area will also require the construction of a temporary sewage pump station to the north along Kersey Way SE. The exact location of this pump station was not known at this time, as other property owners to the north are also discussing development plans. However, it will likely be located in the vicinity of 49th St. SE and Kersey Way SE. The station will be required to be appropriately sized to serve not only filed and proposed applications, but also to serve the entire drainage basin. When sanitary sewer lines are extended northward along Kersey Way to Oravetz Rd. SE at some point in the future, the pump station will be abandoned. The EIS recommended City of Auburn water service will be provided by connecting to existing water lines within the Lakeland Hills development. Numerous off-site improvements will need to be made to the water system, including the construction of a booster pump station at the Terrace View along the East Valley Highway (a.k.a. A ST SW). The western 300 feet of the Division 1 site is encumbered by the Bonneville Power Administration's (BPA’s) electrical transmission lines and easements. This area will be partially developed as an active and passive open space amenity, including a linear trail and open natural areas. Separate active recreational facilities will be provided directly adjacent to this area, but not within the power line easement. Active amenities will include a sport court and playground equipment. Internal pathways and one public road crossing will provide access to these facilities. The open space and amenities will benefit residents of both Divisions. 8 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 7 4. On October 6, 2008 the City Council adopted Ordinance No. 6187 repealing the City’s code provisions for development agreements. Consistent with the city’s practice and law, the Ordinance became effective five days after publication or on October 14, 2008. 5. On October 13, 2008, the then Applicant, Jeff Mann of Apex Engineering PLLC on behalf of Todd Duty agent for Property Owner, Betty Frye, filed an application (File No. MIS08-0017) for a Development Agreement under the city’s code provisions for development agreements (ACC 14.21) before this code section was repealed by Ordinance No. 6187 on October 14, 2008 (The effective date). The development agreement proposal was for subdivision of approximately 81 acres into 256 lots; mostly for detached single family homes and approximately 40 townhomes. While the project was considered vested to the process under the city code section for a negotiated development agreement, the latest Applicant has chosen to submit a preliminary plat application and pursue platting under the standards in effect. 6. A Notice of Application (NOA) for the development proposal was issued November 24, 2008. The notices were posted at the Site, mailed to adjacent property owners according to County Tax Assessor records a minimum of 300 feet of the Site, and published in The Seattle Times, newspaper. 7. Up through 2010 the City staff reviewed several resubmittals for the purpose of sufficient information for the City Council’s consideration and to serve as a basis for a staff recommendation on the development agreement. In 2012, the City granted several extensions for resubmittal of information for application processing, under ACC 14.06.010.G. 8. The King County Tax Assessor website records show the property was purchased by JDH Investment Group, Applicant, on May 31, 2013. Information/Description of Preliminary Plat Proposal 9. On April 21, 2014 a Preliminary Plat Application (File No PLT14-0006) was filed by James E. Kirkebo III (“Tres”) of Apex Engineering, PLLC on behalf of Blake Haddock of JDH Investment Group Corporation for the subdivision of an approximately 79.45 acres (“Site”) into approx. 202 single-family residential lots and eleven (11) tracts under the R5, Residential five dwelling units per acre zoning standard. 10. The City’s plat submittal requirements specify that Applicant must identify any plat phasing that is proposed. No such phasing was identified with the application. As a result, the City has not considered nor evaluated any phasing of the construction or final platting to consider how each phase could function independently for preliminary plat conditions. As a result, no phasing is allowed based on the current proposal. Any change to include phasing would likely require the specific preparation of civil plans based on the phasing and may require a major adjustment of an approved preliminary plat (ACC 17.10.100.B) to ensure that preliminary plat conditions are re-reviewed for coordination with any phasing. 11. The Applicant has not proposed a gated community. 12. On April 27, 2016, an Application for a modification of plat standards (deviation) pursuant to ACC Chapter 17.18 (Modification of Standards and Specifications) was submitted for relief from City Engineering Design Standards (manual) for the following issues: Deviation Request #1: Allow four horizontal curves that are less than the minimum radius of 333 feet for a “local residential” classified street. Deviation Request #2: Allow the use of walls on more than three sides in the storm ponds and not require 25% of the pond perimeter to be a vegetated soil slope not steeper than 3:1. 9 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 8 13.On May 5, 2016 a Variance Application was submitted for a variance from the city’s critical area requirements that prohibit alteration of Class IV landslide hazard areas (ACC 16.10.100(E)(2). The plat proposes grading and alteration of Class IV landside hazard area within the southwest corner of the Plat for Tract A, (Open Space) and the adjacent Lots 7 and 8 and grading and alteration of Class IV Landslide Hazard Areas near the south-central portion for “Road F” Lots 71 through 73 and “Tract I” a storm drainage tract. The location of these Class IV Land Hazard Areas (slopes 40% or greater) is shown on “Critical Slope Exhibit”, Sheet 26 of Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016. With this reasonable use exception application, the proposal has been modified to avoid affecting the Class IV landslide area at the southwest corner of the site and shown affecting Tract A and adjacent Lots 7 and 8. Also, the Class IV Landslide Hazard Areas near the south- central portion for “Road F” Lots 71 through 73 and “Tract I” a storm drainage tract has been adjusted slightly in located in response to additional geotechnical evaluation and changed to affect Lots 69-70, and Tracts G and I (storm drainage tracts). 14.The Application was revised and resubmitted on July 14, 2016 in response to City comments. The project was changed to include 200 lots and ten tracts, among other revisions. 15.Also, on July 14, 2016 the application was modified to include a letter request for a modification of plat standards for relief from the minimum density standard of the zoning code was requested. The application also revised to include an additional modification of the plat standards for relief from the Engineering Design Standard as follows: Deviation Request #3: Allow a modified street section for a portion of Road B and Road C northerly of the intersection of Road F. The intent of the modified street section design is to allow ingress/egress of emergency vehicles and non-emergency vehicles without interference from each other. 16.The Site is roughly rectangular in shape; the longer axis is aligned north-south measuring approximately 2,698.94 feet by approximately 1,328.7 feet east-west. The long narrow shape and change in topography across the site complicate development. 17.The project site is located on the north and south sides of Evergreen Way SE, between Quincy and Udall AV SE, within the SW ¼ of Section 32-21-05, W.M. The property is identified by 4 King County Assessor’s Parcel No's: 322105-9010, -9011, -9030 & -9037. 18.A description of the current site conditions is found in the: Wetland Assessment, Diamond Valley Estates Auburn WA, Raedeke Associates Inc. April 8, 2014, as follows: “3.1 GENERAL PROPERTY DESCRIPTION The Diamond Valley Estates project site is located within the Bowman Creek basin on the north slope of the Lake Tapps plateau, south of the White River. The site consists of a series of north to south oriented ridges and ravines that slope down to the north towards Kersey Way (Figure 2). Elevations of the overall site range from approximately 220 feet above sea level at the northeastern corner of the property to about 570 feet above sea level at the southwest property corner. The site consists of moderately to steeply sloping terrain.” “At the time of our 2013 site investigation, the property was undeveloped and dominated by deciduous, mixed and coniferous forests. In addition to the forested areas, a small area of pasture is located in the north-central portion of the site.” “The majority of the property appears to have been logged during the 1930's to 1940's based on the 18-inch to 24-inch diameter at breast height of the majority of 10 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 9 the coniferous trees on the site. Several areas within the northeastern portion of the site appear to have been logged more recently due to the relatively smaller diameters of trees found growing in these areas. Several old logging roads and trails extend through the property.” 19. The Site is currently mainly vacant forested hillside generally sloping to the NE. The southern portion of the Site contained an east-west segment of Evergreen Way SE and associated temporary stormwater pond for the road. The construction of Evergreen Way SE was required as prerequisite to any development of any of the Kersey III Preliminary Plats project, as identified in the EIS documents. This constructed roadway was completed and dedicated to the City in 2009. 20. The Comprehensive Land Use designation for the Property is “Single-Family Residential”. The Site is also part of the Lakeland Hills Special Planning Area, adopted by Resolution No. 1851 in April 1988 as a sub-area or neighborhood plan of the City’s Comprehensive Plan. The Plan was developed after preparation of a Draft and Final EIS in 1981. An excerpt from the Plan provides: “The Lakeland Hills Plan applies the policy guidance contained in the comprehensive plan to the area known as Lakeland Hills. Plan policies are discussed as they relate to three main subject areas: land use; natural environment, parks and open space; and facilities. This Plan is consistent with and implements the key mitigation measures related to land use described in the Environmental Impact Statement prepared for the Lakeland Hills development. “ 21. The Site is zoned R-5 Residential, Five (5) Dwelling Units per Acre (ACC 18.07). The stated purpose of the R-5, Residential zone is: “. . .to create a living environment of optimum standards for single-family dwellings. It is further intended to achieve development densities of four to five dwelling units per net acre. This zone will provide for the development of single-family detached dwellings and for such accessory uses as are related, incidental and not detrimental to the single-family residential environment.” 22. The site is approximately 79.44 acres, or 3,460,427 square feet (SF) as specified by the application materials and King County Assessor’s website data. Auburn City Code (ACC) 18.02.065 guides the density calculations for development. The City regulations that were in effect provide for a minimum and base (maximum) density for the R-5 Residential zone of 4 and 5 dwelling units per net acre, respectively. As depicted on Sheet 1 of the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 19, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016. The gross acreage less deductions yield a “net acreage” of 2,801,098 sq. ft. (or 64.30 acres). This “net acreage” yields a base (maximum) density of 322 dwelling units for the Site. This net acreage also yields a minimum density of 238 dwelling units. The Project proposes approximately 200 dwelling units (lots); a 16% reduction and which is less than the minimum number of dwelling units allowed by code and a variance to the minimum density standards was requested and approved for the project at the time of the preliminary plat. 23. Per ACC 12.64A, “Required Public Improvements”, the following public right-of-way (ROW) dedication and construction of public right-of-way improvements are required for the subdivision: • Dedication of ROW and construction of improvements for Road B to a “boulevard- modified” Residential Collector standard between Evergreen Way SE and G ST SE based on standards specified in the City of Auburn Engineering Design Standards. A modification of plat standards (deviation) is requested to the modified boulevard section in order to provide a wider divided access as an alternative to providing a second access. 11 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 10 • Dedication of ROW and construction of improvements for Road B to a modified “Residential Collector” standard between Evergreen Way SE and the intersection of Roads B, C and F based on standards specified in the City of Auburn Engineering Design Standards. A modification of plat standards (deviation) is required. • Dedication of ROW and construction of improvements for Road B to a modified “Local Residential” standard between the intersection of Roads B, C and F and the northern property line based on standards specified in the City of Auburn Engineering Design Standards. A modification of plat standards (deviation) is required. • Dedication of ROW and construction of improvements for Road C to a modified “Local Residential” standard between intersection of Roads B, C and F and the northern property line based on standards specified in the City of Auburn Engineering Design Standards. A modification of plat standards (deviation) is required. • Dedication of ROW and construction of improvements for Road E to the “Local Residential” standard specified in the City of Auburn Engineering Design Standards. • Dedication of ROW and construction of improvements for Road F to the “Local Residential” standard specified in the City of Auburn Engineering Design Standards. • Dedication of ROW and construction of improvements for Road G to the “Local Residential” standard specified in the City of Auburn Engineering Design Standards. • (There is no listed Road A or Road D). Originally Proposed Roads: • ROAD B = 2,871+/- LF. 50' / VARIABLE WIDTH R/W, 171,246+/- SF. • ROAD C = 1,379+/- LF. 50' / VARIABLE WIDTH R/W, 87,435+/- SF. • ROAD E = 480+/- LF. 50' R/W, 28,449+/- SF. • ROAD F = 975+/- LF. 50' / VARIABLE WIDTH R/W, 54,406+/- SF. • ROAD G = 883+/- LF. 50' R/W, 53,345+/-. SF. 24. The extension of “Road F” at the location proposed at the east boundary of the Site is necessary to provide secondary access for the adjacent approved plat of the Forest Glen, City File No. PLT6-0008 (preliminary plat) & PLT19-0008 (final plat). The final plat of Forest Glen was recorded in October of 2020 under recording number 20200309000474 and has been fully completed and homes built (Exhibit 13). 25. “Road B” is proposed ending in a temporary cul-de-sac at the midpoint of the north boundary of the Site since it is foreseeable to be extended in the future to serve future off-site development to the north. There are no active proposals or applications for off-site development to the north. 26. “Road C” is not depicted as extending to the north boundary of the Site and having a temporary cul-de-sac since grades in this vicinity and off-site to the north appear to preclude off-site future extension and connection of this public roadway. There are no active proposals or applications for off-site development to the north. 27. The plat proposes use of shared driveways between adjacent lots at selected locations within the plat. Shared driveways are needed to address corner lots and where individual driveways would be located too close to street intersections and where a center median in Road C limits driveway locations. The shared driveways are shown on Sheet 20, “Conceptual Grading Plan”, of the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016. Further changes may be identified during civil plan review process. 28. Water service to serve the plat will be provided by the City of Auburn. Connections will be required to constructed to the existing 12-inch water lines in Evergreen Way SE with main line extensions within the rights-of-way and easements in the plat. 29. The water system shall be designed to meet City of Auburn Design Standards (Chapter 7 – Water Facilities) and the City’s 2015 Comprehensive Water Plan (Chapter 3 - Policies and 12 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 11 Criteria). For each pressure zone, the distribution system pressures shall be 35 pounds per sq. inch (psi) minimum and 80 psi maximum. 30. Due to considerable elevation changes across the site, the site will require separation into three water pressure zones regulated by pressure reducing stations to be designed and constructed. 31. Sanitary sewer service to serve the plat will be provided by the City of Auburn. Sewer connection will be required to be constructed from the terminus of the sewer line existing near the NE corner of the site that was previously constructed with the earlier divisions of the Kersey III, Preliminary Plats. The construction of public main extensions will be required northward along the north property boundary of the plat to Road B and within the right-of-way through the plat. Where the public mains are not coincident with street rights-of-way, publicly dedicated tracts or easements are required to city standards. 32. Fire hydrants and mains capable of providing the required fire flow shall be provided per City of Auburn Engineering Design Standards and the International Fire Code (IFC). Fire hydrant locations shall be approved by the Fire Marshal. 33. The requirements of ACC 13.48 Storm Drainage Utility, ACC 15.74 Land Clearing, Filling, and Grading, and the City’s Surface Water Management Manual (SWMM) are applicable to the Site and Project. Under state regulations, the project cannot be vested to former state-compliant stormwater standards and will be required to meet current state-compliant standards. 34. Traffic, fire, park, and school impacts are mitigated through the payment of impact fees in effect at the time of Building Permit issuance for each lot or deferred per ACC 19.02.070(E) (School Impact fees); 19.04.040(H) (Transportation Impact Fees); 19.06.040(F) (Fire Impact Fees); and 19.08.030(G) (Parks Impact Fees). 35. The plat originally proposed ten proposed tracts totaling approximately 30 acres as depicted on Sheet 1 of the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 19, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016, as follows: • TRACT "A” = 85,844+/- SF. OPEN SPACE, TO HOME OWNER'S ASSOCIATION (H.O.A.) • TRACT “B” = 3,226+/- SF. OPEN SPACE / UTILITY TRACT, TO CITY OF AUBURN • TRACT "C" = 1,182+/- SF. SHARED ACCESS FACILITY, LOTS 24 & 25, TO LOTS 24 & 25 • TRACT "D" = 3,800+/- SF. SHARED ACCESS FACILITY, LOTS 27 - 29, TO LOTS 27 - 29 • TRACT "E" = 109,371+/- SF, OPEN SPACE, TO H.O.A. • TRACT "F" = 4,481+/- SF. OPEN SPACE / UTILITY TRACT, TO CITY OF AUBURN • TRACT "G" = 255,551+/- SF. OPEN SPACE, TO H.O.A. • TRACT "H" = 5,170+/- SF. OPEN SPACE, TO H.O.A. • TRACT "I" = 834,497+/- SF. OPEN SPACE, WETLANDS, STREAMS, BUFFERS ▪ WETLANDS = 28,220+/- SF. TO H.O.A. ▪ STREAMS = 8,391+/- SF. TO H.O.A. ▪ WETLAND AND STREAM BUFFERS = 207,650+/- SF. TO H.O.A. ▪ STORM FACILITY/OPEN SPACE = 590,236+/- SF.TO CITY OF AUBURN (STORM FACILITIES TO BE IN TRACTS DEDICATED TO THE CITY, TRACT LIMITS TO BE FINALIZED DURING FAC PROCESS) • TRACT “J” = 3,175+/- SF. SHARED ACCESS FACILITY, LOTS 157 & 158, AND UTILITY TRACT, TO LOTS 157 & 158 The tracts are anticipated to be further clarified in purpose, provisions, and adjusted in location through the civil plan review process. Information/Description of Critical Areas 36. Critical areas on the Site and in the vicinity of the Site include geologic hazard areas, wildlife habitat areas, wetlands, and streams. Initial information on these is found in the Kersey II Preliminary Plat Draft Environmental Impact Statement July 2004, City of Auburn. More site- 13 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 12 specific information related to the proposal includes a preliminary geotechnical report and a wetland report (including streams) prepared to accompany the preliminary plat application. 37. Information on the site’s streams is found in the: Wetland Assessment, Diamond Valley Estates Auburn WA, Raedeke Associates Inc. It identifies the site contains two streams; Streams A and B. Both streams flow northward to the NE corner of the Site. The streams join off-site to the east to become Stream AB within a steeply sided ravine that is partly within the northeast corner of the project site. Stream AB flows northwesterly to re-enter the property briefly before leaving the property again at the north boundary. Stream AB flows northward from the project site for approximately 1,200 feet to the south side of Kersey Way SE. Stream AB passes beneath Kersey Way SE through a concrete pipe and flows approximately 100 feet further to the north before reaching Bowman Creek. Water was present within Streams A, B, and AB at the time of Raedeke’ s May 2002 site investigations; however, water was not present within any on-site portion of the stream channels during their September 2002 or July/August 2013 site investigations. This could be attributable to the late season investigation. 38. Information on the site’s wetlands is found in the: The Wetland Assessment, Diamond Valley Estates Auburn WA, Raedeke Associates Inc. April 8, 2014. It identifies the site contains approximately 0.7 acres (30,420 square feet) of wetlands based on current site conditions. Six wetlands occur within the project site (Wetlands A, B, C, and D, and Wetlands 1 and 2). Three of the identified wetlands (Wetlands A, 1, and 2) are associated with Stream A within the eastern portion of the property. One of the wetlands (Wetland D) is hydrologically isolated within a closed depression in the central portion of the project site. Two of the wetlands are on slopes (Wetlands B and C) within the northeast portion of the site. Wetland C is also isolated with no surface connection to on-site streams. Several areas adjacent to existing wetlands that had been previously delineated as potential wetland extensions and described in the EIS documents no longer met criteria to be determined wetland based on guidance provided by the regional supplement to the U.S. Army Corps of Engineers (COE) wetland delineation manual for the Western Mountains, Valleys, and Coast Region (COE 2010). This guidance was not available at the time of the original delineations in 2000 by DBM Engineers Inc. (DBM) and boundary verifications by Raedeke Associates, Inc. in 2002 and was used to determine that several areas abutting Wetland A and Wetland B and within the Stream A channel just upstream and downstream of Wetland A were not wetland because they no longer met hydric soil criteria. One new wetland area was delineated (Wetland 2) since the preparation of the EIS documents. This area is within the Stream A channel, approximately 80 feet downstream from Wetland A. The area had not been delineated at the time of the 2000 DBM investigation or during the 2002 boundary verification by Raedeke Associates, Inc. Although at that time the area had hydric soils and evidence of seasonal inundation, it was not vegetated and thus, did not meet criteria for dominance by hydrophytic vegetation as is required to be determined wetland by the COE wetland delineation manual (Environmental Laboratory 1987). At the time of our current investigation, the area was dominated by yellow skunk cabbage (Lysichiton americanus, OBL) and therefore met criteria for dominance by hydrophytes. Tables 1 and 2 provides a summary of all wetlands and streams that were delineated or investigated within the site, including their size, vegetation cover class, likely Washington Dept. of Ecology (DOE) ratings, and corresponding buffer widths that likely would be required per City of Auburn (2014) code. Wetland delineation data forms for the wetland and upland area are found in Appendix A of the Wetland Report. Table 1. Wetland Ratings per revised WDOE (Hruby 2004, WDOE 2008b) ratings form and corresponding City of Auburn (2014) buffer standards: 14 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 13 Table 2. Stream Classifications and corresponding City Auburn (2014) buffer standards: Stream Class Minimum Buffer (ft.) Stream A III 25-50 Stream B III 25-50 39. The Wetland Assessment, Diamond Valley Estates Auburn WA, Raedeke Associates Inc. April 8, 2014, identifies that alteration of site wetlands could be subject to jurisdiction of the Army Corps of Engineers (COE) and the Washington Dept. of Ecology (WDOE) and alteration of the site streams (including changes in flow) is subject to the jurisdiction of the Washington Dept. of Fish and Wildlife. 40. The current property owner and developer has indicated as part of their application submittal for a preliminary plat extension, that recent site investigation has been conducted by a different biological consultant to confirm the location, boundaries, and classification of wetlands and streams. This document has not been provided to the city, but it is anticipated to be provided with the future application for civil plan review process. Any variations would have to be evaluated by the city and could necessitate a plat alteration. 41. The Site slopes and geologic hazards areas were evaluated in the report: A Geotechnical Engineering Services and Geomorphology Services, Diamond Valley Estates Development, Auburn WA, GeoEngineers, April 18, 2014., Rev. November 16, 2015, Rev. April 21, 2016. At Page1, the Report describes the relationship of site conditions to project construction as follows: “Existing features at the site include locally steep, forested ravine slopes with a small stream and a series of associated wetlands occupying the lower areas of the parcel. We understand the plat concept in its present form includes 200 single- family lots. These lots are laid out on three primary tiers of land that will be significantly re-graded from the existing topography. The subdivision concept includes a stormwater drainage system with two detention ponds (Pond 1 and Pond 2) situated near the toes of steep slopes. The two ponds will be partially cut into the slopes, with retaining walls constructed along their uphill boundaries and retaining walls and fill berms constructed along their downslope boundaries. We understand that the current conceptual configuration of Pond 1 includes a cut made into a northwest facing native slope with a buttress wall at the toe of the cut, transitioning to a fill berm with an inboard retaining wall on the downslope boundary of the pond. We understand that the proposed pond bottom elevation will lie at Elevation 315 feet (NAVD 1988 datum), with the top-of-pond berm elevation at Elevation 330 feet. The top of the retaining walls will also be at Elevation 330 feet.” Cowardin Classification HGM Classification WDOE Rating Total Function Score Habitat Function Score Wetland Buffer (ft.) Wetland 1 PFO Riverine III 33 16 25-50 Wetland 2 PEM Riverine IV 22 16 25-30 Wetland A PFO Riverine III 48 20 25-50 Wetland B PEM/PFO Slope III 34 21 25-50 Wetland C PFO Slope III 37 18 25-50 Wetland D PEM/PSS Depressional 11 53 17 50-100 15 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 14 “We also understand that the current conceptual configuration of Pond 2 includes a cut made into an east facing native slope with a buttress wall at the toe of the cut, transitioning to a fill berm on the downslope boundary of the pond. A retaining wall will also be constructed on the inboard side of the berm. We understand that the proposed pond bottom will be at Elevation 285 feet, with the top-of-pond berm and top of wall elevations both at Elevation 300 feet.” “We understand that both ponds are intended to be used for stormwater detention, and neither pond will have graded slopes, inboard or outboard, steeper than 2H:1V (horizontal to vertical). According to the City, the ponds are to be lined.” “Several new roadways will be constructed for the development, including Road F which will be located in the south half of the development. Road F will cross the broad ravine bottom that extends south to north through the site, and will also cross an existing steep slope area that is inclined at 40 percent or steeper. A fill embankment with an approximate height up to about 40 feet will support the roadway where it crosses the ravine bottom. Fill slope inclinations for the embankment will be at 2H:1V. Cuts will be made uphill of the roadway within the steep slope area; these cuts will be up to about 35 feet in height and will also be inclined at 2H:1V. Much of this grading is intended to create level lots for houses. An existing steep slope inclined at approximately 2H:1V will remain and extend from a segment of Road F down to near the south end of Pond 1. A steep slope area has also been identified within Lots 7 and 8 near the southwest corner of the development. We understand that grading on and near these lots will also result in finished cut slopes of 2H:1V.” 42. With the exception of Evergreen Way SE, the majority of the existing site is undeveloped and mainly forested and contains wetlands in the northeast, lower portion of the site. There is approximately 150 feet of fall in elevation from the north to the south and approximately 201 feet of fall in elevation from the west to the east. The Site’s topography is shown on the “Critical Slope Exhibit”, Sheet 26 of 26 as part of the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016. According to this document the site consists of slopes in the following ranges: • approximately a third of the site is slopes between 15 - 25 percent; • approximately quarter of the site consists of slopes between 25 - 40 percent and • approximately eight percent of the site consists of slopes greater than 40 percent slopes. All areas with slopes 40 percent or greater are classified as Class IV/Very High Landslide Hazard Areas (ACC 16.10.080). For accuracy, some of the 40 percent slopes occurring on-site were the result of grading for construction of Evergreen Way SE and these resultant roadway side slopes are shown paralleling both sides of the roadway on this Exhibit. The construction of public facilities (such as roads) within a critical area are governed by a different approval process, criteria and decision by the Hearing Examiner under ACC 16.10.170 (Special exception for public agencies and utilities). Due to the substantial grade change across the site and slope to the northeast, and the presence of two stream courses and wetlands there are unique physical conditions consisting of exceptional topographical or other physical conditions peculiar to and inherent in the particular lot; and that, as a result of such unique physical conditions, practical difficulties and hardships arise in complying with provisions of this title. City staff have requested several project revisions of the Applicant to carefully evaluate, at least a conceptual level, the 16 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 15 preliminary plat’s consistency with city standards for maximum road grade, for water pressure zones, and impoundment for stormwater pond side slopes, among the other elements that are made more complicated by steep slopes. 43. Based on the geologic, geomorphic, hydrogeologic and geotechnical engineering characteristics investigated, the Report: A Geotechnical Engineering Services and Geomorphology Services, Diamond Valley Estates Development, Auburn WA, GeoEngineers, April 18, 2014., Rev. April 21, 2016, contains numerous recommendations for construction on Pages 33 through 46. The recommendations address such subjects as: • Earthwork, clearing & site preparation, subgrade preparation & structural fill, temporary cut slopes, permanent cut and fill slopes, Utility trenches, sanitary sewer main construction, & sedimentation and erosion control • Foundation design, foundation settlement, lateral resistance, & footing drains • Below grade wall and retaining walls design parameters, back drainage, wall design construction considerations • floor slab support, seismicity, ground shaking, liquefaction potential, ground rupture • pavement recommendations and subgrade preparation, asphalt concrete pavement, drainage considerations • Grading considerations, benching, & terracing • Proposed development of storm ponds • Proposed development on slopes exceeding 40 percent • Downstream drainage mitigation 44. To support the current Reasonable Use Exception (RUE) application, the current owner/ applicant provided a more recent geotechnical document: Geotechnical Evaluation - Reasonable Use Exception, Proposed Diamond Valley Estates 18XX Evergreen Way SE, Earth Solutions NW LLC, September 15, 2023. The evaluation letter and attachments are based on targeted test pit explorations conducted in August 2023 in the vicinity of the previously identified Class IV landslide hazard areas. The report then compares the results to the definitions and classifications within the city critical area regulations and to the proposed revised grading plan for the site. Based on this, the letter report indicates: “In general, site layout designs appear to have successfully incorporated buffer distances from the identified hazard areas. An exception occurs in the vicinity of Lot 70 and the adjacent portion of Road F, Tract G, and Tract I, where an isolated slope feature that meets the definition of a Class IV landslide hazard area is present. Based on our observations and review, this sloping feature only meets the AMC Class IV landslide designation on the basis of slope gradients (40 percent or greater).” “We understand the project has elected to pursue a RUE to allow for alteration of this slope feature and development of the proposed lots and access roadways as currently proposed. As such, the intent of this letter is to evaluate, from a geotechnical standpoint, the feasibility of the currently proposed modifications to the area.” “Based on our review of the referenced grading plans, the area of focus will be subject to a combination of cut and fill activities. Within the boundaries of Lot 70, grade cuts of about 25 feet will be employed in conjunction with grade fills of about five feet. Within Road F, Tract G, and Tract I, grades fill of up to about 30 feet will be utilized. Similar grade alterations are also proposed in the immediately surrounding areas. Adjacent grade changes will be accommodated using gravity-style rockeries and/or 2H:1V permanent (engineered) slopes.” “As demonstrated in the previous section, retaining this area would not be beneficial for overall global stability in the post-construction condition, especially when considering loading from the design-level earthquake. Alteration of the area as 17 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 16 proposed will allow the slope to be re-graded in an engineered manner and in accordance with local standards of practice. Structural fill placed that is placed along the slope will be keyed into the slope and compacted to the target relative density. Grade changes would be accommodated using permanent (engineered) fill slopes, retaining walls, rockeries, or some combination thereof.” “Furthermore, there is an opportunity to improve the long-term drainage characteristics within the area of focus if earthwork and grading activities are permitted to incur; such drainage improvements may include the use of interceptor drains, curtain drains, or similar designs. Construction of these elements will allow for more control of subsurface groundwater flows, which in turn will improve post-construction slope stability.” 45. It is possible that further geotechnical analysis of the site could be required during civil plan review or-- as a result of plat redesign and may result the loss of and/or reconfiguration of certain lots. All lots must accommodate reasonable site development and meet the requirements for maximum driveway grades and stormwater management and seek to avoid requiring variances/deviations in the future. 46. The Site is not located in the regulatory floodplain or special flood hazard areas per Federal Emergency Management Agency (FEMA) maps. 47. The Site is located partially in Groundwater Protection Zone 3 and partially in Groundwater Protection Zone 4 and the Project shall implement best management practices for water resource protection during construction, as required by City critical areas regulations. 48. The Site is not located within any shoreline designation. Information on/Description of Preliminary Plat Approval and its Continuation 49. Due to the length of time and numerous project changes leading up to the preliminary plat hearing, a combined Notice of Application and Notice of Hearing was issued on January 10, 2017. The Notice of Public Hearing was issued a minimum of 10 days prior to the public hearing date as required by ACC 18.70.040. The notice was posted at the Site, mailed to adjacent property owners within at least 300 feet of the Site, and published in The Seattle Times, newspaper. 50. The preliminary plat hearing was conducted on January 25, 2017 at 5:30 pm in the City of Auburn Council Chambers. On February 8, 2017, the Hearing Examiner issued a written decision on the preliminary plat (PLT14-0006), the critical areas variance for a Class IV landslide hazard area, a variance to the applicable minimum four dwelling units per acre density requirement to 3.35 dwelling units per acre and the three deviations for street and stormwater engineering standards. The ‘Finding of Fact’ No. 2, Page 5, incorrectly notes the hearing as having been held on June 25, 2017. The Critical areas variance was denied; all other requests were approved (“Exhibit 12’). 51. Condition No. 41 of the written prel. plat decision (“Exhibit 12”) states: “41. For each the critical area variances requested by the Applicant, the application shall either revise the proposal to remove the requested encroachment or acquire approval of a reasonable use exception pursuant to ACC 16.10.150.” 52. The written hearing examiner decision cites the following substantive ‘Conclusion of Law’ on Page 13, as the reason for denial of the critical area variance (at two locations). “3. Applicability of Variance to Class IV Landslide Hazards. Variance requests may not be made for alterations to Class IV Landslide Hazard areas. It is recognized that ACC 18 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 17 16.10.160 generally authorizes variances in addition to reasonable use requests to the requirements of Chapter 16.10 ACC (also known as the City’s Critical Areas Ordinance). However, ACC 16.10.100(E)(2)(a) provides that for Class IV Landslide Hazard Areas, “[a]lteration shall be prohibited subject to the reasonable use provisions of this chapter.” Similar provisions limit alteration to the reasonable use process for Category I wetlands, ACC 16.10.100(A)(1), and Critical Habitat, ACC 16.10.100(C)(1). Class IV Landslide Hazard Areas, Class I Wetlands and Critical Habitat are the most sensitive of the City’s protected critical areas. No such similar limitations are called out for Class I-III geologically hazardous areas, Class II-IV wetlands or secondary or tertiary habitat. It’s fairly clear that the City Council intended to set a higher bar for modification of the regulations of the City’s most sensitive critical areas.” “This interpretation is supported by the rule of statutory construction that ordinances must be construed in a manner that all the language used is given effect, with no portion rendered meaningless or superfluous. See Rapid Settlements, Ltd. V. Symetra Life Ins. Co., 134 Wn. App. 329, 332 (2006). If ACC 16.10.100(E)(2)(a) is intended to still allow alteration through variance application, there would be no need for it and it would be rendered meaningless. This is because the less sensitive critical areas, i.e. the aforementioned Class I-III geologically hazardous areas, Class II-IV wetlands and secondary or tertiary habitat, make no mention of what alteration process (reasonable use or variance) applies to them. They don’t need to because ACC 16.10.150 (Reasonable Use Process) and ACC 16.10.160 (Variance Process) by their own terms apply to all critical area requirements. If the City Council wanted the more sensitive critical areas to also be subject to both the variance and reasonable use process, the Council similarly didn’t need to make any reference to what modification process applied to them. The only2 contrary interpretation, if any meaning is to be given to ACC 16.10.100(E)(2)(a), is that only the most sensitive critical area regulations are subject to both variance and reasonable use review and the less sensitive critical areas don’t qualify for any alteration. That, of course, would be nonsensical. Class IV Landslide Hazard Areas, Class I wetlands and Critical Habitat are all highly sensitive critical areas. To afford maximum protection while still recognizing constitutionally protected property rights, the Council only intended to allow alteration through the reasonable use process.” ------------------------------------------------------- 2 “There is the added argument to be made that the Class IV Landslide Hazard ACC 16.10.100(E)(2)(a) provision references reasonable use and that reasonable use, in turn, provides at ACC 16.10.150(F) that the applicant should apply for a variance except when application of the critical area regulations would deny all reasonable use. However, if the ACC 16.10.100(E)(2)(a) reference to “reasonable use” is intended to fold in the ACC 16.10.150(F) “reasonable use” reference to variance review, there was no need for ACC 16.10.100(E)(2)(a) to begin with since both the variance and reasonable use provisions would apply in its absence. The only way to logically construe ACC 16.10.100(E)(2)(a) is that it limits modifications to those authorized by reasonable use review, not variance review.” 53. The Hearing Examiner decision was not appealed and no further applications in pursuit of the proposal were submitted to the city for several years. According to ACC 17.10.110, a preliminary plat approved after January 1, 2015, shall be valid for a period of five (5) years. The Diamond Valley Estates subdivision received approval on February 8, 2017, and therefore expires on February 8, 2022. 54. On January 7, 2022, the City of Auburn received an application request for an extension of time from the date of approval of the preliminary plat to apply for a final plat. After staff reviewed the application and determined that the request met the required ‘Findings of Fact’ and ‘Conclusions of Law’, the request was approved on February 4. 2022. Pursuant to “ACC 17.10.110 ‘(Preliminary Plat) Time limitations’, the city may grant up to 3, one-year extensions. 19 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 18 55. On September 26, 2022 the City received a letter from attorney, Michael A. Spence of Helsell Fetterman indicating: “On September 12, 2019, Court Commissioner Henry Judson signed an Order Appointing General Receiver under King County Superior Court Cause No. 19-2- 23961-1SEA. Under this order, the above referenced property was placed under the “sole and exclusive possession and control” of Elliott Bay Asset Solutions. At that moment, JDH Investment Group, LLC lost control of the property.” “The Order Appointing also enjoined JDH Investment Group from “interfering with the Receiver’s exclusive possession, control, management, maintenance, repair, alteration, improvement, marketing, listing and/or selling of the property.” “For all practical purposes, the City of Auburn should consider Elliott Bay Asset Solutions, LLC as the owner of the property and Pulte Homes as the party with a valid and binding Purchase and Sale Agreement permitting them to perform due diligence and granting them the right to purchase the property. We would appreciate it if the City of Auburn would treat the parties consistent with the City of Auburn’s standard policies and procedures.” 56. On January 3, 2023 the City received an application for a second preliminary plat extension pursuant to ACC 17.10.110, ‘(Preliminary Plat) Time limitation’. After reviewing the application and determining that the request met the required ‘Findings of Fact’ and ‘Conclusions of Law’, the requested second extension was approved on February 6, 2023. I. CONCLUSIONS – CRITICAL AREA REASONABLE USE EXCEPTION: 1. On September 26, 2023 a critical area reasonable use exception application (File No CAO23- 0010) was filed by Thomas Barghausen (agent), President of Barghausen Consulting Engineers Inc. on behalf of Allison Rothstein (Applicant/Property owner), Director of Land Entitlement and Development, MainVue Homes WA LLC related to the subdivision of the approximately 79.45 acres (“Site”) into approx. approx. 200 single-family residential lots and ten tracts under the R5, Residential five dwelling units per acre zoning standard. 2. More specifically, the application requests the reasonable use exception (RUE) from the city’s critical area requirements that prohibit alteration of Class IV landslide hazard areas (ACC 16.10.100(E)(2)). The plat proposes grading and alteration of a Class IV landside hazard area within one specific geographic area of the site; near the south-central portion of the plat for “Road F”, Lots 69 and 70 and within “Tract G” and “Tract I”, storm drainage tracts. The plat has been revised to avoid the alteration of another Class IV Landslide hazard area in the southwest corner of the Plat for Tract A, (Open Space) and the adjacent Lots 7 and 8; that was part of the previous critical area variance request at the time of preliminary plat approval. 3. More specifically, the Applicant’s justification narrative (“Exhibit 5”) provided with the application (Page 1), states: “The proposed alteration will encompass the entirety of this specific isolated Class IV Landslide Hazard area, (hereafter referred to as the “LHA-Road F”), totaling approximately 18,800 square feet as shown on the attached Exhibit 4 titled “RUE Grading Exhibit for Diamond Valley Estates” prepared by Barghausen Consulting Engineers Inc. dated September 12, 2023. The alteration will include clearing and grading as necessary to construct a public road connection (Road F) to an existing stub road for 54th Street SE within the adjoining plat of Forest Glen.” 4. The City’s critical areas regulations provide the following general and specific purpose statement at ACC 16.10.010(B): 20 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 19 “B. The city finds that these critical areas perform a variety of valuable and beneficial biological and physical functions that benefit the city and its residents. Alteration of certain critical areas may also pose a threat to public safety or to public and private property or the environment. The city therefore finds that identification, regulation and protection of critical areas are necessary to protect the public health, safety and general welfare. The city further finds that the functions of critical areas and the purpose of these regulations include the following: . . . 5. Geologic Hazard Areas. Geologic hazard areas include lands or areas characterized by geologic, hydrologic and topographic conditions that render them susceptible to varying degrees of risk of landslides, erosion, seismic or volcanic activity. The primary goals of regulating geologic hazards are to avoid and minimize potential impacts to life and property by regulating and/or limiting land uses where necessary, and to conduct appropriate levels of analysis and ensure sound engineering and construction practices to address identified hazards.” 5. The City’s critical areas regulations at ACC 16.10.080 (Classification and rating of critical areas) provides the following system of classifications applicable to landslide hazard areas: “G. Geologic Hazard Classifications. Geologic hazard areas shall be classified according to the criteria in this section: . . . 2. Landslide Hazard Areas. Landslide hazard areas are classified as Class I, Class II, Class III, or Class IV as follows: a. Class I/Low Hazard. Areas with slopes of 15 percent or less. b. Class II/Moderate Hazard. Areas with slopes of between 15 percent and 40 percent and that are underlain by soils that consist largely of sand, gravel, or glacial till. c. Class III/High Hazard. Areas with slopes between 15 percent and 40 percent that are underlain by soils consisting largely of silt and clay. d. Class IV/Very High Hazard. Areas with slopes steeper than 15 percent with mappable zones of emergent water (e.g., springs or ground water seepage), areas of known (mappable) landslide deposits regardless of slope, and all areas with slopes 40 percent or greater.” 6. Class IV, Very High Landslide Hazard is the highest, most sensitive category. To avoid and minimize potential impacts to life and property from identified landslide hazards, the city’s critical area regulations provide certain specific standards based on the degree of susceptibility; the critical areas code prohibits the alteration of Class IV – Very High Hazard Landslide Hazard areas. Specifically, ACC 16.10.100, ‘Alteration or development of critical areas – Standards and criteria’ says. “ACC 16.10.100 Alteration or development of critical areas – Standards and criteria Alteration of specific critical areas and/or their buffers may be allowed by the director subject to the criteria of this section. Alteration shall implement the mitigation standards as identified in ACC 16.10.110, and the performance standards of ACC 16.10.120 and the monitoring requirements of ACC 16.10.130.” “E. Geologic Hazard Areas.” “1. General Standards. The city may approve, condition or deny proposals for the alteration of geologic hazard areas, as appropriate, based on the degree to which the 21 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 20 significant risks posed by critical hazard areas to public and private property and to public health and safety can be mitigated. The objective of mitigation measures shall be to render a site containing a critical geologic hazard as safe as one not containing such hazard or one characterized by a low hazard. In appropriate cases, conditions may include limitations of proposed uses, modification of density, alteration of site layout and other appropriate changes to the proposal. Where potential impacts cannot be effectively mitigated or where the risk to public health, safety and welfare, public or private property, or important natural resources is significant notwithstanding mitigation, the proposal shall be denied.” “2. Specific Standards. a. Class IV Landslide Hazard Areas. Alteration shall be prohibited subject to the reasonable use provisions of this chapter.” (Emphasis added) 7. The city’s critical area regulations provide the following reasonable use provision process and criteria for relief from standards. “A. The standards and requirements of these regulations are not intended, and shall not be construed or applied in a manner, to deny all reasonable use of private property. If an applicant demonstrates to the satisfaction of the hearing examiner that strict application of these standards would deny all reasonable economic use of a property, development may be permitted subject to appropriate conditions. B. Applications for a reasonable use exception shall be processed as a Type III decision, pursuant to ACC 14.03.030 and Chapter 2.46 ACC. C. An applicant for relief from strict application of these standards shall demonstrate that all of the following criteria are met: 1. No reasonable use with less impact on the critical area and its buffer is possible. There is no feasible and reasonable on-site alternative to the activities proposed, considering possible changes in site layout, reductions in density and similar factors, that would allow a reasonable and economically viable use with fewer adverse impacts; 2. The proposed activities, as conditioned, will result in the minimum possible impacts to affected critical areas; 3. All reasonable mitigation measures have been implemented or assured; 4. The inability to derive reasonable use is not the result of the applicant’s actions or that of a previous property owner, such as by segregating or dividing the property and creating an undevelopable condition; and 5. The applicant shall demonstrate that the use would not cause a hazard to life, health, or property. D. Any alteration of a critical area approved under this section shall be subject to appropriate conditions and will require mitigation construction authorized by an approved mitigation plan. E. The burden of proof shall be on the applicant to provide evidence in support of the application and to provide sufficient information on which any decision has to be made. 22 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 21 F.Approval of a reasonable use exception shall not eliminate the need for any other permit or approval otherwise required for a proposal by applicable city codes. G.Except when application of this title would deny all reasonable use of a site, an applicant who seeks an exception from the regulations of the title shall pursue a variance as provided in ACC 16.10.160. (Ord. 6733 § 3 (Exh. B), 2019; Ord. 6442 § 13, 2012; Ord. 5894 § 1, 2005.)” 8.The city’s critical area regulations at ACC 16.10.020 provide the following definition for “reasonable use”: “Reasonable use” means a legal concept articulated by federal and state courts in regulatory taking cases.” 9.Following is a staff analysis of the critical area regulation reasonable use exception application’s compliance with each criterion. The criteria are lettered, in bold font and listed below in italics, followed by the Applicant’s response as provided within their application submittal and then followed by a staff analysis. A.(1.) No reasonable use with less impact on the critical area and its buffer is possible. There is no feasible and reasonable on-site alternative to the activities proposed, considering possible changes in site layout, reductions in density and similar factors, that would allow a reasonable and economically viable use with fewer adverse impacts. Applicant’s Response: “Response: The City defines “reasonable use” to mean “a legal concept articulated by federal and state courts in regulatory taking cases.” The leading federal case is the Supreme Court’s decision in Penn Central Transportation Co. v. City of New York (1978). Penn Central emphasizes that regulatory takings should not result in complete deprivation of all economic use of the property, and that a “reasonable use” extends beyond the minimum economically viable use.” “In Penn Central, the applicant sought to build a skyscraper above the Grand Central Terminal in New York City, but the city’s Landmarks Preservation Commission denied its request. Penn Cent. Transp. Co. v. City of New York, 438 U.S. 104, 104, 98 S. Ct. 2646, 2649, 57 L. Ed. 2d 631 (1978). The Supreme Court’s decision in Penn Central established a multifactor test for analyzing regulatory takings, including the economic impact of the regulation on the applicant, particularly the extent to which the regulation has interfered with distinct investment-backed expectations, as well as the character of the governmental action. Id.” “In a recent Washington State Supreme Court decision, Yim v. City of Seattle, the plaintiffs challenged Seattle’s FIT (First-In-Time) rule, arguing that it violated the Takings Clause of the Washington State Constitution. Chong Yim v. City of Seattle, 194 Wn.2d 651, 656, 451 P.3d 675, 681 (2019). The FIT rule requires property owners to follow specific procedures when selecting residential tenants, prioritizing the first qualified applicant meeting screening criteria. Id.” “The State Court held that the current federal definition of regulatory takings was adopted in Washington and that a finding of per se regulatory taking is appropriate for only two narrow categories of regulations, namely regulations that require an owner to suffer permanent physical invasion of her property and regulations that completely deprive an owner of all economically beneficial use of her property. Id.” 23 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 22 “The Court held that when an alleged regulatory taking does not fit into either of those categories, it must be considered on (a) case-by-case basis in accordance with the Penn Central factors. As described below, application of the Penn Central factors demonstrates that this Reasonable Use Exception should be approved, so as to allow the alteration of LHA- Road F.” “Diamond Valley Estates encompasses 80 acres of land zoned R-5. The property could be potentially developed at a maximum of 5 units/acre for a total of 400 Lots, but the critical areas and relatively steep slopes throughout the site severely limited the potential Lot yield.” “During the design process the applicant determined it was impossible to meet even the minimum lot yield required by code of 238 lots, thereby requiring a zoning (density) variance.” “The approved preliminary plat prepared by APEX with 200 lots was exhaustively reviewed by city staff for over 2 years prior to approval in 2017. The final layout showing the proposed alignment of Road F through LHA-Road F was determined to be the best option to reach the most reasonably economical use of the site. Any other design that would have avoided altering LHA-Road F would result in the loss of additional lots.” “The Penn Central factors require evaluation of: first, the economic impact of the regulation on the property; second, the extent to which the regulation interferes with distinct investment-backed expectations; and third, the character of the government action and whether it advances a legitimate public interest. Penn Cent. at 123.” “In this situation, all three factors of the Penn Central test are met. The City’s regulations prohibit any alteration of a Class IV Landslide Hazard area. The economic impact of the regulation on Diamond Valley Estates results in even fewer new home lots on land that is already being developed at a density lower than the City’s minimum density. By removing this geotechnical hazard through the construction of a public road, the property’s economic value is likely to increase as additional lots can be developed, reaching closer to the City’s planned minimum density.” “Prohibiting alteration of LHA-Road F significantly interferes with investment-backed expectations. The location and shape of LHA-Road F conflicts with the most feasible location for a public road connecting the City’s road network to the neighboring subdivision to the east.” “In fact, that neighboring subdivision was designed, approved, and constructed with a road stub in a location that effectively mandates the alteration of LHA-Road F in order to construct an acceptable road connection into the Diamond Valley Estates property.” “Thus, any developer of the Diamond Valley Estates property would reasonably assume that approvals could be obtained for the alteration of LHA-Road F so as to build the connecting roadway. The City Staff’s prior recommendation to approve a critical area variance allowing alteration of LHA-Road F also set an expectation that alteration would be permitted to enable reasonable development of the subject property.” “Finally, the character of the City’s regulation is the broad protection of all areas with slopes 40 percent or greater, regardless of whether or not soil and groundwater conditions exhibit the characteristics associated with potential landslide prone areas. Generally speaking, such areas are protected in order to minimize risks of erosion along with potential landslides.” 24 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 23 “However, in this case technical experts have demonstrated that LHA-Road F can be altered through regrading of the area without risk of erosion or landslide and, therefore, without harm to the common good, there is no reason to permanently protect the slope. These factors collectively support the argument that a City prohibition on removal of this specific Class IV Landslide Hazard area (LHA-Road F) constitutes a taking under the Penn Central test. Thus, no reasonable use with less impact on the critical area and buffer exists.” Staff Analysis: As the applicant’s statement above indicates, the City’s regulations prohibit any alteration of a Class IV Landslide Hazard area (ACC 16.10.100(E)(2)(a)). The effect of this prohibition results in an economic impact on the developer of Diamond Valley Estates plat and on the city by resulting in even fewer new residential lots on land that is already proposed for development at a density lower than the City’s minimum density. A variance from this minimum density was previously approved at the time of preliminary plat approval. The purpose of the City’s minimum density is to ensure efficient use of land and assist the city in achieving Comprehensive Plan housing goals of accommodating increased population required by the State Growth Management Act (GMA). By removing this geotechnical hazard through allowing alteration and the construction of a public road, the property’s economic value is likely to increase as additional lots can be developed, reaching closer to the City’s planned minimum residential density. While the purpose statement of the city’s code reasonable use provisions (ACC 16.10.150) say that it seeks to avoid denying “all reasonable use”, it contains the apparently contrasting terms of “all” and “reasonable”. While the prohibition on alteration of the Class IV landslide area does not deny “all” use of the property, it does deny what can be considered a “reasonable” use of the property. The subject property has numerous constraints described above and including an isolated approximately 18,800 square feet class IV landslide hazard area in the south-central portion of the site as shown on the Exhibit titled “RUE Grading Exhibit for Diamond Valley Estates” prepared by Barghausen Consulting Engineers Inc., September 12, 2023. Avoiding alteration of this critical area conflicts with the ability to connect roadways necessary for second vehicle access and emergency vehicle access based on city standards for road length and the number of dwelling units. This plat and the adjacent plat of Forest Glen to the east have been evaluated by city staff and professional engineers, including geotechnical engineers, as part of various land use reviews and approvals and civil plan reviews and approvals in reliance upon the ability to connect the roadway (Road F or 54th ST SE) that is in the best interests of public safety. The preliminary plat was the subject of a critical area variance application request at the time of preliminary plat approval and the variance request was denied. The city code provides that “except when application of this title would deny all reasonable use of a site, an applicant who seeks an exception from the regulations of the title shall pursue a variance as provided in ACC 16.10.160.” so the plat developer has exhausted other options, and the reasonable use exception is the only remaining option (ACC 16.10.150(G)) that allows connection of Roadway F to 54th ST SE. Staff finds the request meets the criterion. B. (2.) The proposed activities, as conditioned, will result in the minimum possible impacts to affected critical areas; Applicant’s Response: “Response: The design for the connection of Road F within Diamond Valley Estates to the stub for 54th Street SE is based on the most feasible horizontal and vertical alignment considering the nearby wetlands and stream corridor, topographic conditions, and the existing 25 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 24 geometry of the road stub. The location of LHA-Road F makes it infeasible to circumvent the area with a public road connection that complies with all applicable city road standards. This was first determined when APEX was working with the city on the initial plat application and was subsequently reconfirmed when the most recent plat extension materials from Goldsmith were reviewed by the city in late 2022.” Staff Analysis: The proposal has been revised to avoid one of the two Class IV landslide areas that were the subject of the previous critical areas variance application. It avoids the area at the southwest corner of the site. The proposal does not minimize impacts to the other specific Class IV landslide hazard area, since the proposed alteration removes the entirety of this specific isolated Class IV Landslide Hazard area, totaling approximately 18,800 square feet as shown on the Exhibit titled: “RUE Grading Exhibit for Diamond Valley Estates” prepared by Barghausen Consulting Engineers Inc., September 12, 2023. However, the proposal will maintain consistency with the previously approved preliminary plat configuration and avoids reconfiguration of the plat that could adversely affect other types of on-site critical areas, such as streams and wetlands located downslope of Road F. The narrative justification provided by Barghausen Engineers refer to a conceptual redesign of the preliminary plat layout by Goldsmith Engineering that was informally submitted to the city in November of 2022 at the time of the first request for an extension of the preliminary plat. At that time Goldsmith Engineering informally submitted a conceptual and very preliminary re-configuration of the preliminary plat that sought to shift Road F to go around and avoid the specific class IV landslide hazard area for the purpose of exploring discussions with the city about feasibility of a preliminary plat alteration (An application process for a revision of the approved preliminary plat). The city commented that the increased curvature of road with a 175- foot curve radius does not meet the city standard of a 333-foot curve radius in accordance City engineering standards. Staff finds the request meets the criterion. C.(3.) All reasonable mitigation measures have been implemented or assured; Applicant’s Response: “Response: The proposed alteration will completely eliminate the Class IV Landslide Hazard Area (LHA-Road F) by regrading it in accordance with recommendations of a Geotechnical Engineer as well as the city of Auburn Public Works standards. Upon completion of the plat improvements, LHA-Road F will subsequently become a public roadway along with portions of an open space tract and several residential lots as generally depicted on the approved preliminary plat. These improvements will encompass all required mitigation measures as required by the city as shown on the approved FAC (public facility) construction plans for the plat.” Staff Analysis: Preliminary plat will be required to observe the 41 conditions that were identified in the previous preliminary plat written decision (PLT14-0006) by the Hearing Examiner dated February 8, 2017 and any conditions arising from city’s approval of preliminary plat time extensions or plat alterations. Many of these 41 established preliminary plat conditions originated as mitigation measures identified in the previously prepared Environmental Impact Statement (EIS) of which this site was a part. Contrary to the applicant’s statement, there have not been any mitigation measures or conditions associated with “approved FAC (public facility) construction plans for the plat” because application for civil plans has not yet been made. However, the project 26 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 25 will also be required to observe the applicable Public Works Department engineering design standards when this future submittal occurs. Staff finds the request meets the criterion or adherence will be assured through subsequent civil plan review and final platting processes. D.(4.) The inability to derive reasonable use is not the result of the applicant’s actions or that of a previous property owner, such as by segregating or dividing the property and creating an undevelopable condition; and Applicant’s Response: “Response: The City of Auburn approved the plat of Forest Glen to the east of Diamond Valley Estates, along with the associated stub connection for 54th Street SE. This created the need to extend 54th Street SE into and through the plat of Diamond Valley Estates and fixed the location of the connection as well as its horizontal and vertical alignment.” “Diamond Valley Estates is an undeveloped parcel of land with relatively steep slopes throughout the site ranging from 15-40%+, along with wetlands and a stream corridor and associated buffers.” “It is the combination of these factors, including the location of LHA-Road F in proximity to the existing off-site 54th Street SE Road stub and nearby wetland/stream corridor that necessitated the horizontal and vertical alignment of Road F as shown on the approved preliminary plat by APEX for PLT14-0006.” “Neither the applicant nor the prior owner created the above conditions, so this criterion has been met.” Staff Analysis: The isolated Class IV Landslide Hazard area, totaling approximately 18,800 square feet as shown in the southcentral portion of the site in the exhibit titled “RUE Grading Exhibit for Diamond Valley Estates” prepared by Barghausen Consulting Engineers Inc. dated September 12, 2023, appears to be naturally occurring in origin and does not appear to be the result of the applicant’s actions or that of previous property owners. The previous Wetland Assessment, Diamond Valley Estates Auburn WA, Raedeke Associates Inc. April 8, 2014 characterizes the majority of the site as undisturbed since the 1930-40’s based on observed on-site tree size. Staff finds the request meets the criterion. E.(5.) The applicant shall demonstrate that the use would not cause a hazard to life, health, or property. Applicant’s Analysis: “Response: There is ample evidence in the record for PLT14-0006 and VAR16-0001 that the proposed alteration will not cause a hazard to life, health, or property”. “The geotechnical reports and slope stability analysis prepared by GeoResources and ESNW per attached Exhibits 2 and 3 both conclude that the proposed alteration will not create any adverse impacts or adversely impact life, health, or safety. The area being altered does not exhibit the characteristics typically associated with landslide hazards and is only given this designation because the slope inclination exceeds 40%.” “City of Auburn Public Works staff agreed with GeoResources’ conclusions that the alteration would not cause adverse impacts to life, health, or safety during their review of VAR16-0001 27 of 350 CAO23-0010, RUE for Prel. Plat of Diamond Valley Estates October 23, 2023 Page 26 and the most recent study by ESNW that focused specifically on LHA-Road F reconfirmed these conclusions. Based on all of the above, this criterion has been met.” Staff Analysis: As indicated above, the current owner/ applicant provided a more recent geotechnical investigation: Geotechnical Evaluation - Reasonable Use Exception, Proposed Diamond Valley Estates 18XX Evergreen Way SE, Earth Solutions NW LLC, September 15, 2023. The evaluation letter, based on test pit explorations conducted in August 2023 in the vicinity of the previously identified the Class IV landslide hazard area, and in comparison, to a revised grading reveals the proposed construction can render the vicinity as safe as one not containing a hazard or one characterized by a low hazard—a goal of the city’s critical area regulations. The report says: “Based on our review of the referenced grading plans, the area of focus will be subject to a combination of cut and fill activities. Within the boundaries of Lot 70, grade cuts of about 25 feet will be employed in conjunction with grade fills of about five feet. Within Road F, Tract G, and Tract I, grades fill of up to about 30 feet will be utilized. Similar grade alterations are also proposed in the immediately surrounding areas. Adjacent grade changes will be accommodated using gravity-style rockeries and/or 2H:1V permanent (engineered) slopes.” “As demonstrated in the previous section, retaining this area would not be beneficial for overall global stability in the post-construction condition, especially when considering loading from the design-level earthquake. Alteration of the area as proposed will allow the slope to be re-graded in an engineered manner and in accordance with local standards of practice. Structural fill placed that is placed along the slope will be keyed into the slope and compacted to the target relative density. Grade changes would be accommodated using permanent (engineered) fill slopes, retaining walls, rockeries, or some combination thereof.” “Furthermore, there is an opportunity to improve the long-term drainage characteristics within the area of focus if earthwork and grading activities are permitted to incur; such drainage improvements may include the use of interceptor drains, curtain drains, or similar designs. Construction of these elements will allow for more control of subsurface groundwater flows, which in turn will improve post-construction slope stability.” Staff finds the request meets the criterion. II.STAFF RECOMMENDATION - CRITICAL AREA REASONABLE USE EXCEPTION (File No. CAO23-0010): 1.Staff recommends approval of the Reasonable Use Exception from the city’s critical area requirements that prohibit alteration of Class IV landslide hazard areas (ACC 16.10.100(E)(2)) for the proposed grading and alteration of an approximately 18,800 square foot Class IV landside hazard area near the south-central portion of the site for “Road F” (54th S SE), Lots 69 and 70, and within “Tract G” and “Tract I”, storm drainage tracts. Staff respectfully reserves the right to supplement the record of the case to respond to matters and information raised subsequent to the writing of this report. 28 of 350 Vicinty Map NORTH 29 of 350 EXHIBIT 2 Page 1 of 2 CITY OF AUBURN Land Use Application #1376876 - Diamond Valley Estates RUE 30 of 350 EXHIBIT 3 Project Contact Company Name:Barghausen Consulting Engineers Name:Tom Barghausen Email:tbarghausen@barghausen.com Address:18215 72nd Ave S Phone #:(425) 251-6222 Kent WA 98032 Project Type Activity Type Scope of Work New None Critical Areas Review Project Name:Diamond Valley Estates RUE Description of Work:Steep Slope Reasonable Use Exception for the Plat of Diamond Valley Estates Project Details Development Type Reasonable Use Page 2 of 2 CITY OF AUBURN Land Use Application #1376876 - Diamond Valley Estates RUE 31 of 350 FINAL ENVIRONMENTAL IMPACT STATEMENT (FEIS) for KERSEY III PRELIMINARY PLAT City of Auburn, WA Department of Planning and Community Development The intent and purpose of this Draft EIS is to satisfy the requirements of the State Environmental Policy Act (SEPA), RCW 43.21, and Auburn City Code 16.06, including the requirement to inform citizens and government agencies of a determination pursuant to SEPA. This document is not an authorization for an action, nor does it constitute a decision or recommendation for an action; in its final form, it will accompany recommended action and will be considered in making the final decision on the proposal. DATE OF ISSUE: February 11, 2005 Paul Krauss, AICP Director & SEPA Responsible Official Planning & Community Development 32 of 350 EXHIBIT 4 TO: Recipients of the Final Environmental Impact Statement SUBJECT: Final Environmental Impact Statement- Kersey III Preliminary Plat Date: February 11, 2005 This Final Environmental Impact Statement (DEIS) has been prepared under the direction of the City of Auburn Planning and Community Development Department to evaluate the impacts of the proposed Kersey III Preliminary Plat. The DEIS considers potential impacts and mitigation measures for two land use alternatives for the 170 acre site: the subdivision and use of the Planned Unit Development (PUD) criteria to create 403 lots to support 481 dwelling units, and the subdivision and use of the Planned Unit Development (PUD) criteria to create 628 lots to support 700 dwelling units. A No Action alternative is also analyzed. The project site is located generally west of Kersey Way right-of-way from 49th Street SE (if extended) at its northern limits to the King County line at its southern limits. The project site is located adjacent to and east of the existing Lakeland Hills Divisions 8, 9 and 10. Elements of the environment addressed in the DEIS include surface water, ground water, air quality, earth, traffic and transportation, archaeological/cultural resources and land use. 33 of 350 FACT SHEET Proposed Action The Proposed Action will involve the development of a low-density preliminary plat of 481 dwelling units or a higher density 700 dwelling unit development on a 170-acre parcel located in the southerly portion of the City of Auburn. The 700-unit alternative would be developed under the city’s PUD regulations, while a portion of the 481-unit alternative would require PUD approval. The project consists of seven (7) undeveloped forested parcels. The project will be governed by, among other regulations, the City of Auburn zoning and subdivision ordinances. Open space and sensitive areas would be provided or protected as required by the City of Auburn sensitive area regulations. Certain portions of the site will not be developed due to steep slopes, wetland and power line corridors. The project’s proposed construction will consist of three (3) divisions and six (6) phases. The proposal includes approximately 620,000 cubic yards of earthwork, which is expected to remain on the development site. The proposal will require the on-site and off-site installation of new public facilities to serve the development, to include water, storm sewer and sanitary sewer lines. Onsite storm facilities include wet ponds for detention and water quality treatment. The proposal also requires the dedication of land for use as a public park. The proposal requires the dedication and construction of approximately four (4) miles of new public rights of way to serve the development and provide internal circulation. The improvements include internal streets and a new arterial connection from Evergreen Way SE to Kersey Way. Proponent Dana Mower of DBM Consulting Engineers Representing: Wayne Jones, Lakeridge Development, Inc. Clarence Wright, 6-W, Inc. Todd Duty Lead Agency City of Auburn Department of Planning and Community Development 25 West Main Street Auburn, Washington 98001 Responsible Official: Paul Krauss, AICP, Director Department of Planning and Community Development Contact Persons: Steve Pilcher, AICP Development Services Coordinator (253) 931-3090 spilcher@auburnwa.gov i 34 of 350 Duane Huskey, P.E. Utilities Engineering (253) 804-5062 dhuskey@auburnwa.gov Licenses and Permits City of Auburn: Draft and Final EIS Approvals Preliminary Plat Approval Final Plat Approval Planned Unit Development Approval Grading Permit Land Clearing Permit Facility Extension Permit Building Permits Storm, Sewer and Water Meter Permits Shorelines Substantial Development permit for offsite improvements (potentially) Puget Sound Clean Air Agency (PSCAA): Notice of Construction Notice of Completion State of Washington: General Permit to Discharge Stormwater Hydraulic Project Approvals Electrical Permits Authors and Principal Author: Principal Contributors Apex Engineering Geotechnical Studies: GeoEngineers Air Quality Studies: McCulley, Frick & Gillman Wildlife Habitat/Streams Air Quality Studies: Raedeke Associates, Inc. Traffic Studies: Transportation Solutions, Inc. Archaeological Studies: Larson Anthropological Archaeological Services Limited Date of DEIS Issue Draft EIS: July 1, 2004 Location of the EIS Department of Planning and Community Development and Other Environmental 25 West Main Street Auburn, WA and the Auburn Branch of the Information King County Library 1102 Auburn Way South Approximate Date of Final City Council consideration of the preliminary plat application is ii 35 of 350 Action anticipated no sooner than April 2005. A separate notice announcing the specific date and time of the public hearing will be provided. Final EIS February 11, 2005 FEIS Availability Copies of the FEIS are available, for a fee (to cover the copying charges) at the City of Auburn Department of Planning and Community Development, 25 West Main Street, Auburn Washington. iii 36 of 350 TABLE OF CONTENTS Fact Sheet ___________________________________________________________________________i Table of Contents ____________________________________________________________________iv List of Figures_______________________________________________________________________vi List of Tables ______________________________________________________________________ vii Chapter 1.0 Summary______________________________________________________________ 1 1.1 Introduction____________________________________________________________ 2 1.2 Objectives of the Proposal ________________________________________________ 2 1.3 Project Location ________________________________________________________ 2 1.4 Project Alternatives Description____________________________________________ 2 1.4.1 Alternative 481 – Partial PUD Preliminary Plat _________________________ 2 1.4.2 Alternative 700 – Complete PUD Preliminary Plat_______________________ 5 1.4.3 No Action Alternative _____________________________________________ 5 1.5 Summary of Impacts and Mitigation Measures for the Alternatives ________________ 7 Chapter 2.0 Description of Alternatives_______________________________________________ 20 2.1 Introduction___________________________________________________________ 21 2.2 Alternative 481 – Partial PUD Preliminary Plat_______________________________ 21 2.3 Alternative 700 – Complete PUD Preliminary Plat ____________________________ 21 2.4 No Action Alternative___________________________________________________ 21 2.5 Utilities, Road and Storm Alternatives______________________________________ 21 Chapter 3.0 Responses to Comments_________________________________________________ 27 Icon Materials ______________________________________________________________ 28 Lake Tapps Heights Maintenance Association ______________________________________ 31 Sheryl Mansell ______________________________________________________________ 33 Jerry Bates __________________________________________________________________ 35 Jonie Brook _________________________________________________________________ 37 Patrice Murphy ______________________________________________________________ 39 Mike Bykonen _______________________________________________________________ 42 Office of Archaeology and Historic Preservation (OAHP) _____________________________ 47 Robert J. Murrey _____________________________________________________________ 49 Bruce and Janet Koch _________________________________________________________ 51 Bruce and Lisa Atkins _________________________________________________________ 54 Todd and Tim Covey__________________________________________________________ 57 Harold and Duanna Richards____________________________________________________ 60 Stu Collins __________________________________________________________________ 62 Perry and Trina Peters _________________________________________________________ 64 Glen L. Wood _______________________________________________________________ 68 Mickey Fassbind _____________________________________________________________ 70 Margaret and Gary Staples______________________________________________________ 72 Margaret Staples _____________________________________________________________ 74 Frank and Nancy Peterson______________________________________________________ 76 William K. Rerrick____________________________________________________________ 79 Bridget Ave. S.E. Residents, et. al. _______________________________________________ 81 La Pianta LLC _______________________________________________________________ 84 iv 37 of 350 Roger Gillette________________________________________________________________ 88 Roger Gillette _______________________________________________________________ 90 Linda Howard _______________________________________________________________ 92 S.I. and D. Cocké_____________________________________________________________ 94 Mr. & Mrs. John Shoemaker ____________________________________________________ 96 Heidi Shoemaker _____________________________________________________________ 98 Mr. & Mrs. John Shoemaker ___________________________________________________ 100 Mark and Dee Lunde _________________________________________________________ 102 Mark and Dee Lunde _________________________________________________________ 104 Lois Davis _________________________________________________________________ 106 Brad J. Mosler ______________________________________________________________ 109 Randall Hoffert _____________________________________________________________ 111 David T. Nehren ____________________________________________________________ 113 William Hedrick ____________________________________________________________ 115 Kathy Holch________________________________________________________________ 119 Muckleshoot Indian Tribe Fisheries Division ______________________________________ 121 Tara and Chris Schaefer_______________________________________________________ 126 VOLUME I Appendix A Kersey III Traffic Impact Analysis (TIA) Addendum for the Final Environmental Impact Statement dated January 11, 2005, by T.S.I., Inc. v 38 of 350 LIST OF FIGURES FIGURE PAGE Figure 1 Regional Map and Project Vicinity Map________________________________________3 Figure 2 Alternative 481 – Site Plan __________________________________________________4 Figure 3 Alternative 700 – Site Plan________________________________________________ 6 Figure 4 Stormwater Discharge Points _____________________________________________ 25 vi 39 of 350 LIST OF TABLES TABLE PAGE Table 1 – Summary of Impacts and Mitigation Measures ________________________________________9 vii 40 of 350 CHAPTER 1.0 SUMMARY 1 41 of 350 1.0 SUMMARY 1.1 INTRODUCTION This chapter briefly describes the alternatives considered and provides a summary of the impacts and proposed mitigation measures that would occur under the alternatives. A more detailed discussion of the alternatives is provided in Chapter 3 of this DEIS and in the Technical Appendices. 1.2 OBJECTIVES OF THE PROPOSAL The objectives of this proposal are as follows: x Provide for single-family housing opportunities in the City of Auburn, x Fill the market need for single-family housing and, x Complete the project while mitigating minimal environmental impacts. 1.3 PROJECT LOCATION The Kersey III project is located within the City of Auburn in the southeasterly portion of the City, immediately north of the King County line and east of the Lakeland Hills Planned Community as shown in Figure 1. The project is located between the terminus of Evergreen Way for the Lakeland Hills development and Kersey Way at the intersection of 53 rd Street SE, also shown in Figure 1. The project is located in the Southwest and Southwest Quarter of Section 32, Township 21 North, Range 05 East, W. M., adjacent to and east of the existing Lakeland Hills Divisions 8, 9, and 10. Generally, the site is located west of the Kersey Way right-of-way from 49 th Street SE (if extended) to the King County/Pierce County line. The project area includes approximately 1,950 feet of frontage on Kersey Way proximate to its intersection with 53rd Street SE. 1.4 PROJECT ALTERNATIVES DESCRIPTION 1.4.1 ALTERNATIVE 481 – PARTIAL PUD PRELIMINARY PLAT This alternative assumes that 481 dwelling units will be constructed on the approximately 170-acre project area utilizing the PUD ordinance on a portion of the site in order to accommodate 409 single family lots and 18 lots to accommodate 72 multiple family dwelling units in four-plexes, as shown in Figure 2. Open space and sensitive areas would be protected as directed by City of Auburn policies and applicable regulations. Under the proposal, approximately 31.4 acres of the site, including wetland and buffers and steep slopes, would be set aside as natural open space, 7.0 acres of land would be designated for dedication as a public park and 11.1 acres would be retained within the existing powerline corridor. 2 42 of 350 43 of 350 44 of 350 The project would consist of three (3) divisions developed in six (6) phases each. The proposal will require on-site installation of new public facilities to serve the development to include water, stormwater and sanitary sewer lines. Two stormwater detention and treatment facilities would be constructed totaling approximately 15.0 acres. The proposal requires the dedication and construction of approximately four (4) miles of new public right of ways to access the development and provide internal circulation. These roads include internal streets and a new arterial connection from Evergreen Way SE to Kersey Way. Off-site improvements include the extension of water lines in Kersey Way to the White River or additional connection to the existing East Valley Highway main. Either water system will require an additional booster station. Off-site sanitary sewer could include either the extension of sewer on Kersey Way to an existing pump station in Oravetz Road or a partial extension on Kersey Way with a pump station extending to existing gravity sewer in Evergreen Way in Lakeland. Off-site stormwater facility improvements include the modification of an existing erosion problem along Kersey Way. 1.4.2 ALTERNATIVE 700 – COMPLETE PUD PRELIMINARY PLAT This alternative assumes that up to 700 dwelling units will be constructed on the approximately 170-acre project area utilizing the PUD ordinance over the entire site in order to accommodate up to 628 single family lots and up to 18 lots to accommodate 72 multiple family dwelling units in four-plexes, as shown in Figure 3. The project will require the application of City of Auburn zoning and subdivision ordinances. Open space and sensitive areas would be protected as directed the City of Auburn policies and applicable regulations. Under this proposal, approximately 31.4 acres of the site, including wetland and buffers and steep slopes would be set aside as native open space, 10.6 acres of land would be designated for dedication as a public park and 11.1 acres would be retained within the existing powerline corridor. Off-site improvements include the extension of water lines in Kersey Way to the White River or additional connection to the existing East Valley Highway main. Either water system will require an additional booster station. Off-site sanitary sewer could include either the extension of sewer on Kersey Way to an existing pump station in Oravetz Road or a partial extension on Kersey Way with a pump station extending to existing gravity sewer in Evergreen Way in Lakeland. Off-site stormwater facility improvements include the modification of an existing erosion problem along Kersey Way. The project would consist of three (3) divisions developed in six (6) phases each. The proposal will require on-site and off-site installation of new public facilities to serve the development to include water, stormwater and sanitary sewer lines. Two stormwater detention and treatment facilities would be constructed, totaling approximately 15.0 acres. The proposal requires the dedication and construction of approximately four (4) miles of new public right of ways to access the development and provide internal circulation. These roads include internal streets and a new arterial connection from Evergreen Way SE to Kersey Way. 1.4.3 NO ACTION ALTERNATIVE The No Action Alternative would allow development of the 170-acre Kersey III site under existing zoning regulations and comprehensive plan. The site is currently zoned R-1, allowing 8,000 square-foot minimum lots. The No Action Alternative would allow for the subdivision of each of the parcels that make up the Kersey III project. The No Action Alternative assumes that public utilities and the extension of Evergreen Way SE to Kersey Way will not be completed because of a lack of coordination and that a lower density would result based on the utilization of on-site wells and drainfield systems. For purposes 5 45 of 350 of the No Action Alternative, it is assumed that a 5-acre minimum lot size (pursuant to King County Code 12.32.010, related to water service requirement) is required to provide for on-site wells. The No Action Alternative would then yield no more than 34 lots. The No Action Alternative did not consider the location of the 34 lots related to access to the public right-of-way and the City’s regulatory limits on the length of dead-ends and single access points. The application of these additional standards would likely further limit the number of lots constructed under the No Action Alternative, but for purposes of the evaluation, the yield is projected at 34 lots, the number capable of meeting the area requirement for individual wells. This is not consistent with the zoning and Comprehensive Planning policies. 6 46 of 350 47 of 350 1.5 SUMMARY OF IMPACTS AND MITIGATION MEASURES FOR THE ALTERNATIVES The following is a summary of the impacts, mitigation measures, and unavoidable adverse impacts for the three alternatives. A more complete description of the impacts and mitigation measures is provided in Chapter 3. 8 48 of 350 Table 1 – Summary of Impacts and Mitigation Measures for Alternatives EARTH RESOURCES Impacts Potential Mitigation Measures Topography Applicable to: No Action Alternative Alternative 481 Alternative 700 Note: Alternative 700 will have less impervious area and more open space resulting in less grading and modification to topography. The No Action Alternative is assumed to have smaller topographic impacts due to the smaller number of anticipated building lots and less secondary roads and cul-de-sacs. Cut slopes on the order of 25 feet and fills on the order of 20 feet for the main roadway. Modification to existing topography for transitions between main roadway, secondary roads, building lots and connections to Evergreen Way and Kersey Way. Approximately 451,800 cubic yards will be graded for the main road, internal roads, lot grading and detention ponds. Cuts to range from 5 to 15 feet can typically be held in place using conventional gravity retaining walls or by grading the slopes 2:1 or flatter. Cuts in excess of 15 feet that cannot be sloped back could require tiebacks, soil nail or similar engineered walls. Fills compacted and placed to support the new roadways and homes should be designed to accommodate the type of fill material used and the underlying soil conditions. Permanent fill slopes will generally be inclined at 2:1 or flatter. Retaining walls can be used to limit the lateral extent of the fills. Potential retaining wall options for fill applications include concrete cantilever walls, concrete masonry unit (CMU) block walls, mechanically stabilized earth (MSE) walls and soldier pile walls. Soils and Geography Applicable to: No Action Alternative Alternative 481 Alternative 700 Settlement due to placing new loads (structures or fill embankments) over potentially compressible materials such as forest duff and undocumented existing fill. Earthwork constraints associated with excavating, hauling, placing and compacting moisture sensitive soils such as the native ice contact and glacial till materials. Excessive infiltration of stormwater into the soils below detention ponds if relatively free draining materials such as advanced outwash are exposed in the pond bottoms. Proper site preparation techniques that include removal of all surficial organic materials (vegetation, forest duff, topsoil and large roots) from below proposed infrastructure and new fill locations. Unless subsequent exploration and testing indicates portions of the existing fill meet structural fill specifications, all fill should be removed from below proposed infrastructure and new fill embankment locations. Use of ground improvement techniques such as deep dynamic compaction or compaction grouting to enhance the in situ condition of existing fill. Mitigate onsite moisture sensitive soils by limiting earthwork activities to the dry season, typically considered to extend from June through October. 9 49 of 350 Table 1 – Summary of Impacts and Mitigation Measures for Alternatives EARTH RESOURCES Impacts Potential Mitigation Measures Soils and Geography Use add mixtures such as lime or cement can be used to improve the workability of onsite moisture sensitive soils during wet weather conditions. Line ponds with relatively impermeable materials if advance outwash deposits are exposed during construction. Liners could consist of natural soil liners or geosynthetic membranes. Onsite ice contact and glacial till soils may be suitable for use for natural soil liners if the use of onsite soils is desired. Geologic Hazards Chapter 3.1.3 Applicable to: No Action Alternative Alternative 481 Alternative 700 Erosion, Grading and Vibrations Erosion could lead to silt laden runoff being transported offsite, resulting in a water quality degradation of local surface water. If unmitigated, the sediment budget analysis indicates that soil loss rates could be as high as 2,000 tons per year during construction of Alternative 700. Excavation soils to be used as fill will need to be stockpiled and unsuitable or excess materials would need to be removed from the site. Heavy trucks would be required to transport fill and waste materials, which could have impacts on noise and air quality due to dust and could damage pavement along haul routes. Excavation, compaction and construction vehicles and equipment may result in vibrations that could damage nearby structures or disturb nearby residents or wildlife. Vibration impacts from earthwork are anticipated to be moderate to low. An erosion and sediment control plan (ESCP) shall be implemented for the interception and treatment of potential silt laden runoff that could occur during clearing, grading, construction of infrastructure, and site stabilization. The ESCP should provide measures to ensure that no silt-laden runoff leaves the construction site. Measures identified in the City of Auburn Design Manual and Storm Drainage Manual to mitigate short-term impacts to earth environment during construction are proposed. Following construction, the side slopes of embankments and cut slopes shall be protected against erosion by re-vegetation (i.e. hydroseeded). Vibration mitigation should include a pre- condition survey of areas within 100 feet of construction activity and a vibration- monitoring program. Design, construct and maintain features that limit uncontrolled surface water and ground water flow in landslide hazard areas. 10 50 of 350 Table 1 – Summary of Impacts and Mitigation Measures for Alternatives EARTH RESOURCES Impacts Potential Mitigation Measures Geologic Hazards Applicable to: No Action Alternative Alternative 481 Alternative 700 Steep Slopes and Landslides Potential for landslide of existing steep landslide prone slopes. The conceptual design suggests that new infrastructure will not traverse or be built over landslide hazard areas; however, some roads and perhaps the northwest stormwater detention pond might be built adjacent to landslide hazard areas. Steep slopes and landslides Mitigation for construction in landslide hazard areas or adjacent to landslide areas includes the use of retaining structures and enhanced drainage and/or setbacks to limit the potential impacts of landslide hazards on the proposed development and vice versa. Design, construct and maintain features that limit uncontrolled surface water or groundwater flow and steep slope and landslide areas. In pond areas, it may be necessary to line the ponds. New permanent cut and fill slopes should be designed and constructed using accepted standards of practice. 11 51 of 350 Table 1 – Summary of Impacts and Mitigation Measures for Alternatives WATER RESOURCES Impacts Potential Mitigation Measures Surface Water Applicable to: No Action Alternative Alternative 481 Alternative 700 Creation of approximately 60 acres of impervious surfaces without mitigation would cause a net increase in surface water runoff. Increases in surface water runoff have the potential to increase onsite erosion and increase the rate of offsite stream channel erosion. Unmitigated increases in stormwater flow volumes would likely cause accelerated erosion along portions of the stream banks of Bowman Creek and unnamed tributary 0043, impacting Kersey Way. Potential reduction in volume of sediment exiting the project site downstream of proposed stormwater detention ponds. The reduction in sediment could also accelerate erosion downstream of the culvert by Kersey Way. Surface water discharge from proposed stormwater detention ponds will be designed to match 50 percent of the existing peak flow rate for the two year event under existing conditions and match the 100 percent peak flow rate for the 10- year, 25-year and 100-year storm events under existing conditions. Restricted discharge rates will reduce the potential for increased storm channel erosion. Partial infiltration of stormwater on individual home sites will also help to mitigate reductions in shallow water flow. Supplemental evaluation of stream channel conditions along Bowman Creek in the vicinity of the outlet of the culvert beneath Kersey Way that has an existing erosional feature. Mitigation for the existing condition could consist of a properly designed and constructed energy dissipater and stream channel and bank protection. Groundwater Applicable to: No Action Alternative Alternative 481 Alternative 700 The creation of impervious surfaces would cause a net reduction in groundwater recharge and shallow groundwater flow. Potential reduction of groundwater recharge to regional aquifers is not considered to be significant because of the relatively small area of the site. A reduction in shallow groundwater flow, however, could adversely affect nearby wetlands. Potential impacts on groundwater due to surface spills of fuels, lubricants and other chemicals used during construction. Potential diversion of groundwater along the sewer system with groundwater following the backfill materials. Direct roof runoff water from selected areas to infiltration and dispersion trenches on the upslope ends of wetlands in order to restore average annual shallow groundwater flows to onsite wetlands. Define and implement groundwater quality protection measures such as best management practices, spill prevention plans and monitoring of any stormwater discharge to groundwater. Due to the limitations of onsite soils, it is not proposed that any stormwater would be discharged to groundwater. Infiltration of runoff from approximately 3.44 acres of impervious surfaces from Alternative 481 could restore average annual shallow groundwater flow rates to onsite wetlands Install backfill seepage barrier with the sewer line connection at defined intervals. 12 52 of 350 Table 1 – Summary of Impacts and Mitigation Measures for Alternatives WILDLIFE AND HABITAT Impacts Potential Mitigation Measures Applicable to: Alternative 481 Alternative 700 Note: The No Action Alternative is not anticipated to impact wildlife and habitat because of the smaller number and anticipated density of potential anticipated building lots. Clearing and grading activities will impact movement patterns of some wildlife species between habitats on and off site. State monitored or candidate species would continue to find some habitat onsite, but use of the site would be reduced and fewer individuals would be able to use the retained habitats. Development of the site would increase the degree of fragmentation of existing natural habitats onsite. The artificial edge is created between the edges of native forest habitat and development areas would likely increase the spread of invasive or weedy plant species. Open space or park areas would convert natural areas to more open managed habitat of lesser value to wildlife. Reduction of hydrology to wetlands would potentially reduce available breeding and foraged habitat. The creation of impervious surface, which will likely cause an increase in stormwater flow volumes leaving the site and causing potential downstream channel and bank erosion. Wetlands would be encompassed in open space tracts that would greatly exceed wetland buffer requirements. Hydrologic changes to wetlands have the potential to affect vegetated communities and wildlife. Measurements of hydrologic conditions in wetlands after development would provide information necessary to confirm the maintenance and preservation of vegetative and wildlife habitats. Implementation of enhanced open space designs and avoidance of all 40% slopes and landslide areas (except for arterial roads) and use of low impact development techniques as part of the PUD design would further reduce impacts to wildlife and habitat. 13 53 of 350 Table 1 – Summary of Impacts and Mitigation Measures for Alternatives WILDLIFE AND HABITAT Impacts Potential Mitigation Measures Applicable to: Alternative 481 Alternative 700 Note: The No Action Alternative is not anticipated to impact wetlands and streams because of the smaller number and anticipated density of potential anticipated building lots. Unavoidable Significant Adverse Impacts Loss of the existing vegetation and soils and replacement by urban areas that include impervious surfaces. Retained native habitats would be fragmented and/or isolated from other native habitats, thus reducing the value to wildlife. An increase in the disturbance of the patches of native habitats retained onsite as a result of increased human activity. Impacts to wildlife include direct loss and alteration of existing native habitat and increased levels of human activity. Short-term disturbance associated with clearing and grading that would kill burrowing mammals, nesting birds and amphibians and displace the more mobile wildlife. Local populations of most native species would be reduced and cause a number of changes in the species’ common position because of the urban level of development. Animals that are least tolerant of human disturbance such as ground- and shrub- nesting birds, small, ground-dwelling mammals, carnivores and amphibians would be most affected by the proposed development. 14 54 of 350 Table 1 – Summary of Impacts and Mitigation Measures for Alternatives WETLANDS AND STREAMS Impacts Potential Mitigation Measures Applicable to: Alternative 481 Alternative 700 Note: The No Action Alternative is not anticipated to impact wildlife and habitat because of the smaller number and anticipated density of potential anticipated building lots. Indirect impacts could result from construction activity affecting surface and near surface flows with potential impacts to the hydrology of the onsite wetlands. Reducing water flows to wetland areas could impact the wetlands and their associated plant and animal communities. The creation of impervious surfaces would likely cause a net reduction in groundwater recharge and shallow water interflow to the wetlands and streams. Native growth open space encompassing the wetlands and their total buffers would total essentially the same acreage as Alternative 700. Sediment transport deposition, particularly during construction, can adversely impact plant and animal communities of the wetlands by affecting water quality (increased turbidity, suspended and settleable solids, temperature, pollutants), which could adversely affect the suitability for wildlife habitat. Increases in sediment deposition could occur during construction which could adversely affect some wetland vegetation and associated wildlife in the wetlands. Clearing and conversion of adjoining areas to residential and recreational uses will increase fragmentation of native habitat and increase the risk of spread of invasive species and the addition of increased human activity and associated increase in domestic pets could adversely affect the habitat value of remaining native open space areas. Preservation of all onsite wetlands and providing buffers that meet or exceed the recommended requirements. Routing stormwater runoff from the proposed development through stormwater detention and water quality facilities prior to discharge to sensitive downstream areas. Limiting hydrologic impacts to major onsite wetlands by routing roof runoff and runoff from undeveloped portions of the onsite and offsite sub-basin to the wetlands. The use of stormwater detention ponds to control discharge rates before releasing roof runoff and other runoff from undeveloped surfaces to the major wetlands to avoid substantial erosion impacts. Monitoring of wetland performance after construction. Additional infiltration trenches or flow spreaders located near the source of Stream A to minimize hydrologic impacts from site development. Provide a 50-foot wetland buffer around Wetland D. Clearly marking the limits of wetland buffers or setbacks prior to construction activities on the site to prevent inadvertent or unnecessary encroachment. Including energy dissipaters or flow dispersion facility that outfalls for stormwater detention/water quality treatment facilities to prevent substantial erosion impacts within Stream A and B. Limiting major initial clearing, grubbing and grading activities where feasible to the drier months of the year (e.g. April to October) or implementing additional Best Management Practices (BMPs) for any such activities during the wet season. This would further reduce the potential for substantial adverse impacts to wetlands from sediment deposition. 15 55 of 350 Table 1 – Summary of Impacts and Mitigation Measures for Alternatives LAND USES Impacts Potential Mitigation Measures Applicable to: No Action Alternative Alternative 481 Alternative 700 . The development of the Kersey III project will convert existing forested and open space land into a preliminary plat with residential and open space land uses. Mitigation is not anticipated regarding land use in the DEIS as the applicant will be required to demonstrate compliance with the Auburn Comprehensive Plan policies and objectives and the Zoning Ordinance. The City is likely to impose mitigation on specific development proposals during the process associated with subsequent permit reviews to ensure compliance is achieved. TRANSPORTATION Impacts Potential Mitigation Measures Applicable to: Alternative 481 Alternative 700 Note: The No Action Alternative is not anticipated to impact the transportation network. Alternate 481 will generate 428 total new trips while Alternate 700 will generate 622 new trips. The intersection of Evergreen Way SE and Lakeland Hills Way SE will be degraded to a poor level of service. The new intersection of Evergreen Way SE at Kersey Way and 53rd Street SE requires traffic control and realignment to maintain functions operations of a four-way intersection. Entering site distance requirements in the southbound direction along Kersey Way SE at the eastern site access should meet or exceed City of Auburn standards with the construction of Evergreen Way SE The City of Auburn collects a transportation impact fee. Construction of a signal at Evergreen Way SE (extended) and Kersey Way SE is included in the project. Traffic control measures are needed, that will include a roundabout at Evergreen Way SE and Lakeland Hills Way SE prior to the opening of the Evergreen Way SE extension to Kersey Way. Realignment of 53rd Street SE/Kersey Way intersection with the proposed Evergreen Way SE intersection is required. An Addendum Traffic Impact Analysis dated January 11, 2005, and included in this FEIS, has been prepared to address safety along Kersey Way S.E., safety along Evergreen Way, analysis of 53 rd Street S.E., corridor analysis under 2008 conditions rather than 2005 conditions, and roundabout analysis of Evergreen Way and Lakeland Hills Way. The TIA addendum identified the need for the addition of auxiliary lanes at 53 rd St. SE & Kersey Way and an advance signal warning for the Kersey Way/Evergreen Way intersection PUBLIC SERVICES Impacts Potential Mitigation Measures Police and Fire Service Applicable to: Commensurate increase in demand related to constructed density. Tax revenues generated by the preliminary plat will be available to the City of Auburn to finance additional staff and equipment 16 56 of 350 Table 1 – Summary of Impacts and Mitigation Measures for Alternatives No Action Alternative Alternative 481 Alternative 700 needs. Incorporation of crime prevention through environmental design strategies into subdivision and house design to minimize opportunities for crime. Parks Applicable to: Alternative 481 Alternative 700 Increase in residential population increases demand for viable park spaces and recreational opportunities. Dedication land for park in accordance with City policy, 6.25-acres for each 1,000 persons of projected population. PUBLIC SERVICES Impacts Potential Mitigation Measures Schools Applicable to: No Action Alternative Alternative 481 Alternative 700 Commensurate increase in the number of school-aged children based on the constructed density. Payment of the applicable school impact fee at the time of building permit UTILITIES Impacts Potential Mitigation Measures Sanitary Sewer Alternative 481 Alternative 700 Option 1 – Sewer Main This option would require the construction of a sewer main from the Kersey III site on Kersey Way north to Oravetz Road, then along the south side of the White River, connecting to an existing manhole/sewer stub northeast of Lakeland Hills Lift Station in Oravetz Road. Increases the amount of sewage flows proceeding to the downstream pumping station and eventually the overall King County Department of Natural Resources, Waste Water Treatment Division (King County) treatment system. Construction impacts would include the trenching and excavation of the sewer line along the entire length of the conveyance system, creating the potential for impacts from erosion and sedimentation to Bowman Creek, located to the east, generally follows Kersey Way corridor. Either project creates the need to provide for a sanitary sewer system pursuant to the Auburn 2001 Comprehensive Sewer Plan. Implementation of Best Management Practices for erosion and sedimentation control along Kersey Way for the protection of Bowman Creek and along the southerly boundary and through the site for the protection of drainage courses, wetlands and slope areas. Observation of geotechnical engineering recommendations for the protection of slope areas during the trenching excavation of the force main. Size of pipes in order to accommodate the remainder of the South Hill Service Area. 17 57 of 350 Table 1 – Summary of Impacts and Mitigation Measures for Alternatives UTILITIES Impacts Potential Mitigation Measures Sanitary Sewer Alternative 481 Alternative 700 Option 2 – Sanitary Sewer Pump Station Interim Pump Station which would be designed to place a gravity sanitary sewer main in the new Evergreen Way SE extending to Kersey Way, and north on Kersey Way to the north end of the project site. A pump station would connect to the existing gravity system in Evergreen Way within the Lakeland Hills development, discharging into the existing sanitary sewer main within Lakeland Hills. This option would require the excavation, trenching and construction of the sewer main, force main, and pump station along the southerly boundary of the Kersey III project site and through the project site, primarily through open space and residential right-of-ways of the plat, creating the potential for impacts from erosion and sedimentation to downstream wetlands and Bowman Creek. Analysis of pumping demands indicates that capacity improvements are needed in the Lakeland system. The downstream capacity would accommodate Alternative 481 plus approximately 109 lots in the surrounding service area. The downstream capacity would accommodate approximately 638 units under Alternative 700. Under this option, however, no other portion of the South Hill service area basin could be accommodated within the Lakeland system. Replacement or bypass of the first two pipes in Evergreen Way in order to provide the necessary capacity that is available in the downstream system within the Lakeland Hills system. Implementation of Best Management Practices for erosion and sedimentation control along Kersey Way for the protection of Bowman Creek and along the southerly boundary and through the site for the protection of drainage courses, wetlands and slope areas. Observation of geotechnical engineering recommendations for the protection of slope areas during the trenching excavation of the force main. The number of units served by this alternative would be limited to the downstream capacity. Pump station is an interim solution and participation in the construction of the main along Kersey Way to the Metro Pump Station is still required. Sanitary Sewer No Action Alternative The No Action Alternative would require the development of 34 new wells and onsite drainfield systems. Lot sizes would be 5 acres in size or greater to meet State Health Standards. Lot sizes and drainfield systems would need to be sized to address existing onsite soils and slope conditions. 18 58 of 350 Table 1 – Summary of Impacts and Mitigation Measures for Alternatives UTILITIES Impacts Potential Mitigation Measures Water Alternative 481 Alternative 700 Alternative 481 would require approximately 332 gallons per minute (gpm) to be supplied to the site while alternative 700 requires approximately 483 gpm for peak day domestic supply. Construction impacts include the installation of water service mains along rights-of-way, which would include the management of excavation materials and possible interruption of traffic during construction. Development of a booster pump facility and extension of water main along Kersey Way to the Kersey III site per the City of Auburn Comprehensive Sewer System Plan. Water No Action Alternative No impacts are expected from the installation of wells to serve large lot developments ARCHAEOLOGICAL RESOURCES Impacts Potential Mitigation Measures Applicable to: No Action Alternative Alternative 481 Alternative 700 Potential impacts of five areas within the site which may have moderate potential for archaeological deposits which were not evident during the field reconnaissance. These areas may have potential for archaeological deposits due to the ridge line and flat areas found in these five areas. Potential impact to inadvertently discovered archaeological deposits that could be encountered during construction. A professional archaeologist should monitor ground-disturbing activities through topsoil and the upper layer of glacial deposits in the five areas for the proposed Kersey III project. In the event that hunter-fisher-gatherer or historic period archaeological deposits and/or human remains are inadvertently discovered during construction, ground- disturbing activity should be halted immediately in an area large enough to maintain integrity of the deposits and coordination with several local and state agencies should be held. Discovery of archaeological resources during construction of individual plat developments or under large lot scenario would also require the halting of ground disturbing activities in order to assess and maintain the integrity of archaeological deposits. AIR QUALITY Impacts Potential Mitigation Measures Applicable to: No Action Alternative Alternative 481 Alternative 700 Air and odor pollutants from trucks and construction equipment and operations could occur. Traffic delays due to construction traffic. Control measures and best management practices of the Associated General Contractors of Washington shall be defined and implemented for use during construction. 19 59 of 350 CHAPTER 2.0 DESCRIPTION OF ALTERNATIVES 20 60 of 350 JUSTIFICATION FOR REASONABLE USE EXCEPTION ALTERATION OF CLASS IV LANDSLIDE HAZARD AREA (ACC 16.10.150) Diamond Valley Estates City of Auburn File Nos. PLT14-0006 / VAR16-0001 King County Parcel Nos. 322105-9010, -9011, -9030, and -9037 Prepared for: MainVue WA LLC 121 3rd Avenue Kirkland, WA 98033 September 25, 2023 Our Job No. 22817 61 of 350 EXHIBIT 5 1 Description of Proposed Alteration Request: The applicant is seeking approval to alter an isolated Class IV Landslide Hazard area totaling approximately 18,800 square feet in conjunction with the development of the approved preliminary plat of Diamond Valley Estates (PLT14-0006/VAR16-0001). Class IV Landslide Hazard areas are defined in ACC 16.10.080(G)2(d). The subject property encompasses seven (7) such isolated areas as shown on Exhibit 1 titled “Steep Slope Areas Exhibit” prepared by Barghausen Consulting Engineers, Inc. dated September 1, 2023. However, the only reason these areas are designated Class IV landslide hazards is strictly due to the existing topographic slope being over 40% as set forth in the very last sentence of subsection (d) below: “d. Class IV/Very High Hazard. Areas with slopes steeper than 15 percent with mappable zones of emergent water (e.g., springs or groundwater seepage), areas of known (mappable) landslide deposits regardless of slope, and all areas with slopes 40 percent or greater” (emphasis added). That is, these are not slopes with mappable landslide deposits, springs, or groundwater seepage. A final revised geotechnical study was prepared by GeoResources as part of the preliminary plat application. This study is attached hereto as Exhibit 2 titled “Geotechnical Engineering and Geomorphology Services for Diamond Valley Estates” dated April 21, 2016. The study included a comprehensive slope stability analysis of the areas shown on Exhibit 1 and concluded that the underlying soil and groundwater conditions in these areas do not have mappable zones of emergent water or mappable landslide deposits. The only reason for the Class IV designation was because the slopes in these areas were steeper than 40%. A more recent report was prepared by Earth Solutions Northwest (ESNW) titled “Geotechnical Evaluation – Reasonable Use Exception” dated September 15, 2023, attached hereto as Exhibit 3. ESNW conducted additional test pits within the area of the proposed alteration, prepared their own independent stability analysis, and came to the same conclusions as GeoResources. The proposed alteration will encompass the entirety of this specific isolated Class IV Landslide Hazard area, (hereafter referred to as the “LHA-Road F”), totaling approximately 18,800 square feet as shown on the attached Exhibit 4 titled “RUE Grading Exhibit for Diamond Valley Estates” prepared by Barghausen Consulting Engineers Inc. dated September 12, 2023. The alteration will include clearing and grading as necessary to construct a public road connection (Road F) to an existing stub road for 54th Street SE within the adjoining plat of Forest Glen. 62 of 350 2 The public road connection was required by the city in order to provide neighborhood connectivity between adjacent residential subdivisions, as well as to establish a second public access road connection for both Diamond Valley Estates and Forest Glen. The clearing and grading work will extend beyond the boundary of the isolated area as part of the overall plat development for Lots and storm drainage facilities as generally depicted on Exhibit 4, as well as sheet 21 of 26 from the approved preliminary plat plan set titled “Diamond Valley Estates Conceptual Grading Plan” prepared by APEX Engineering PLLC for PLT14-0006 dated July 11, 2016, attached hereto as Exhibit 5. Upon completion of the alteration work and associated plat improvements, LHA-Road F will be entirely eliminated, along with any potential hazards associated with it in the present condition. It will be replaced with engineered cut/fill slopes designed and constructed to city standards as well as in accordance with the recommendations of a licensed Geotechnical Engineer. Appropriate TESC measures will be implemented during construction, and the final graded slopes will be permanently stabilized with appropriate vegetation or other measures to assure that there won’t be any adverse impacts associated with the proposed alteration. Project Narrative/Background Summary: The Diamond Valley Estates preliminary plat was approved by the HEX on February 8, 2017 (File No. PLT14-0006). The original application was filed in 2014 and went through an intensive review process leading up to the public hearing on January 25, 2017. In addition to the plat application, the applicant also applied for 2 critical area variances under VAR16-0001, one zoning variance, and 3 minor design deviations from public works standards. The critical area variances were both associated with proposed alterations of isolated Class IV Landslide Hazard Areas on the subject property. One of these alterations was to allow for the creation of proposed Lots 7 and 8. The other alteration was essentially the same as what is being requested in this application as described above for the purpose of completing a public road connection to the existing stub road (54th Street SE) in the plat of Forest Glen. Staff recommended approval of the preliminary plat along with the zoning variance, the 3 minor deviations, and the critical area variance to allow for the public road connection of proposed Road F to the stub for 54th Street SE Section IV of the Staff Report (pages 25-32) prepared by city staff for the Preliminary Plat of Diamond Valley Estates dated January 12, 2017, attached hereto as Exhibit 6, summarize the review process and analysis that staff went through to reach the above conclusions for the VAR16-0001. 63 of 350 3 After careful consideration of the materials presented in support of the variance, including the GeoResources Slope Stability Analysis, city staff concluded that the alteration of the Class IV Landslide Hazard Area associated with the construction or Road F (aka LHA- Road F), met all 6 of the criteria necessary for approval of the variance and was supportive of such alteration. Although city staff recommended approval of the proposed alteration of LHA-Road F for the construction of the Road F connection to the 54th Street SE stub road, the HEX determined that because of the way the code was written, the proposed alteration of a Class IV Landslide Hazard Area could not be reviewed or approved through the Critical Area Variance process. Such alterations could only be approved through the Reasonable Use provisions as set forth in ACC 16.10.150. As a result of the above, the HEX declined to rule on the merits of VAR16-0001. However, the HEX added Condition No. 41, confirming the applicant could apply for a Reasonable Use Exception in order to perform the requested alteration of the LHA-Road F area in order to complete the extension of Road F in the general alignment as shown on the approved preliminary plat. The HEX articulated the above in paragraph 3 of the “Substantive Conclusions of Law” section of the “Findings of Fact, Conclusions of Law, and Final Decision” approving the preliminary plat of Diamond Valley Estates dated February 8, 2017, attached hereto as Exhibit 7. It should also be noted that although the criteria that need to be met for approval of a Critical Area Variance are not exactly the same as the criteria for approval of an RUE, they have substantial similarities. They both require mitigation of impacts associated with the alteration. They also require an applicant to show there won’t be any adverse impacts on public health and safety and must be in response to conditions not caused by the applicant or prior owner. All of these criteria were deemed satisfied by the city staff for the variance and should therefore be deemed satisfied for this RUE. 64 of 350 4 Compliance with Criteria for Approval (ACC 16.10.150(C)1-5) C. An applicant for relief from strict application of these standards shall demonstrate that all of the following criteria are met: 1. No reasonable use with less impact on the critical area and its buffer is possible. (*There is no feasible and reasonable on-site alternative to the activities proposed, considering possible changes in site layout, reductions in density and similar factors, that would allow a reasonable and economically viable use with fewer adverse impacts) Response: The City defines “reasonable use” to mean “a legal concept articulated by federal and state courts in regulatory taking cases.” The leading federal case is the Supreme Court’s decision in Penn Central Transportation Co. v. City of New York (1978). Penn Central emphasizes that regulatory takings should not result in complete deprivation of all economic use of the property, and that a “reasonable use” extends beyond the minimum economically viable use. In Penn Central, the applicant sought to build a skyscraper above the Grand Central Terminal in New York City, but the city’s Landmarks Preservation Commission denied its request. Penn Cent. Transp. Co. v. City of New York, 438 U.S. 104, 104, 98 S. Ct. 2646, 2649, 57 L. Ed. 2d 631 (1978). The Supreme Court’s decision in Penn Central established a multifactor test for analyzing regulatory takings, including the economic impact of the regulation on the applicant, particularly the extent to which the regulation has interfered with distinct investment-backed expectations, as well as the character of the governmental action. Id. In a recent Washington State Supreme Court decision, Yim v. City of Seattle, the plaintiffs challenged Seattle’s FIT (First-In-Time) rule, arguing that it violated the Takings Clause of the Washington State Constitution. Chong Yim v. City of Seattle, 194 Wn.2d 651, 656, 451 P.3d 675, 681 (2019). The FIT rule requires property owners to follow specific procedures when selecting residential tenants, prioritizing the first qualified applicant meeting screening criteria. Id. The State Court held that the current federal definition of regulatory takings was adopted in Washington and that a finding of per se regulatory taking is appropriate for only two narrow categories of regulations, namely regulations that require an owner to suffer permanent physical invasion of her property and regulations that completely deprive an owner of all economically beneficial use of her property. Id. 65 of 350 5 The Court held that when an alleged regulatory taking does not fit into either of those categories, it must be considered on case-by-case basis in accordance with the Penn Central factors. As described below, application of the Penn Central factors demonstrates that this Reasonable Use Exception should be approved, so as to allow the alteration of LHA-Road F. Diamond Valley Estates encompasses 80 acres of land zoned R-5. The property could be potentially developed at a maximum of 5 units/acre for a total of 400 Lots, but the critical areas and relatively steep slopes throughout the site severely limited the potential Lot yield. During the design process the applicant determined it was impossible to meet even the minimum lot yield required by code of 238 lots, thereby requiring a zoning variance. The approved preliminary plat prepared by APEX with 200 lots was exhaustively reviewed by city staff for over 2 years prior to approval in 2017. The final layout showing the proposed alignment of Road F through LHA-Road F was determined to be the best option to reach the most reasonably economical use of the site. Any other design that would have avoided altering LHA-Road F would result in the loss of additional lots. The Penn Central factors require evaluation of: first, the economic impact of the regulation on the property; second, the extent to which the regulation interferes with distinct investment-backed expectations; and third, the character of the government action and whether it advances a legitimate public interest. Penn Cent. at 123. In this situation, all three factors of the Penn Central test are met. The City’s regulations prohibit any alteration of a Class IV Landslide Hazard area. The economic impact of the regulation on Diamond Valley Estates results in even fewer new home lots on land that is already being developed at a density lower than the City’s minimum density. By removing this geotechnical hazard through the construction of a public road, the property’s economic value is likely to increase as additional lots can be developed, reaching closer to the City’s planned minimum density. Prohibiting alteration of LHA-Road F significantly interferes with investment- backed expectations. The location and shape of LHA-Road F conflicts with the most feasible location for a public road connecting the City’s road network to the neighboring subdivision to the east. In fact, that neighboring subdivision was designed, approved, and constructed with a road stub in a location that effectively mandates the alteration of LHA- Road F in order to construct an acceptable road connection into the Diamond Valley Estates property. 66 of 350 6 Thus, any developer of the Diamond Valley Estates property would reasonably assume that approvals could be obtained for the alteration of LHA-Road F so as to build the connecting roadway. The City Staff’s prior recommendation to approve a critical area variance allowing alteration of LHA-Road F also set an expectation that alteration would be permitted to enable reasonable development of the subject property. Finally, the character of the City’s regulation is the broad protection of all areas with slopes 40 percent or greater, regardless of whether or not soil and groundwater conditions exhibit the characteristics associated with potential landslide prone areas. Generally speaking, such areas are protected in order to minimize risks of erosion along with potential landslides. However, in this case technical experts have demonstrated that LHA-Road F can be altered through regrading of the area without risk of erosion or landslide and, therefore, without harm to the common good, there is no reason to permanently protect the slope. These factors collectively support the argument that a City prohibition on removal of this specific Class IV Landslide Hazard area (LHA-Road F) constitutes a taking under the Penn Central test. Thus, no reasonable use with less impact on the critical area and buffer exists. 2. The proposed activities, as conditioned, will result in the minimum possible impacts to affected critical areas; Response: The design for the connection of Road F within Diamond Valley Estates to the stub for 54th Street SE is based on the most feasible horizontal and vertical alignment considering the nearby wetlands and stream corridor, topographic conditions, and the existing geometry of the road stub. The location of LHA-Road F makes it infeasible to circumvent the area with a public road connection that complies with all applicable city road standards. This was first determined when APEX was working with the city on the initial plat application and was subsequently reconfirmed when the most recent plat extension materials from Goldsmith were reviewed by the city in late 2022. 3. All reasonable mitigation measures have been implemented or assured; Response: The proposed alteration will completely eliminate the Class IV Landslide Hazard Area (LHA-Road F) by regrading it in accordance with recommendations of a Geotechnical Engineer as well as the city of Auburn Public Works standards. Upon completion of the plat improvements, LHA-Road F will subsequently become a public roadway along with portions of an open space tract and several residential lots as generally depicted on the approved preliminary plat. These improvements will encompass all required mitigation measures as 67 of 350 7 required by the city as shown on the approved FAC construction plans for the plat. 4. The inability to derive reasonable use is not the result of the applicant’s actions or that of a previous property owner, such as by segregating or dividing the property and creating an undevelopable condition; and Response: The City of Auburn approved the plat of Forest Glen to the east of Diamond Valley Estates, along with the associated stub connection for 54th Street SE. This created the need to extend 54th Street SE into and through the plat of Diamond Valley Estates and fixed the location of the connection as well as its horizontal and vertical alignment. Diamond Valley Estates is an undeveloped parcel of land with relatively steep slopes throughout the site ranging from 15-40%+, along with wetlands and a stream corridor and associated buffers. It is the combination of these factors, including the location of LHA-Road F in proximity to the existing off-site 54th Street SE Road stub and nearby wetland/stream corridor that necessitated the horizontal and vertical alignment of Road F as shown on the approved preliminary plat by APEX for PLT14-0006. Neither the applicant nor the prior owner created the above conditions, so this criterion has been met. 5. The applicant shall demonstrate that the use would not cause a hazard to life, health or property. Response: There is ample evidence in the record for PLT14-0006 and VAR16-0001 that the proposed alteration will not cause a hazard to life, health, or property. The geotechnical reports and slope stability analysis prepared by GeoResources and ESNW per attached Exhibits 2 and 3 both conclude that the proposed alteration will not create any adverse impacts or adversely impact life, health, or safety. The area being altered does not exhibit the characteristics typically associated with landslide hazards and is only given this designation because the slope inclination exceeds 40%. City of Auburn Public Works staff agreed with GeoResources’ conclusions that the alteration would not cause adverse impacts to life, health, or safety during their review of VAR16-0001 and the most recent study by ESNW that focused specifically on LHA-Road F reconfirmed these conclusions. Based on all of the above, this criterion has been met. 68 of 350 SCALE: 1"=100'For:Title: 22195 1 MAINVUE WA LLC 121 3RD AVENUE KIRKLAND, WA 98033 STEEP SLOPE AREAS EXHIBIT FOR 1 FOREEDIAMOND VALLEY ESTATESA PORTION OF THE S.W. 1/4 OF SECTION 32, TOWNSHIP 21 NORTH, RANGE 5 EAST, W.M.CITY OF AUBURN, KING COUNTY, WASHINGTONEVERGREEN WAYEVERGREEN WAYSTEEP SLOPE AREASTEEP SLOPE AREASTEEP SLOPE AREASTEEP SLOPE AREASTEEP SLOPE AREASTEEP SLOPE AREASTEEP SLOPE AREASTEEP SLOPE AREAS NOTESURVEY NOTEDIAMOND VALLEY ESTATES PLT14-000669 of 350EXHIBIT 6 Geotechnical Engineering and Geomorphology Services Diamond Valley Estates Development Auburn, Washington for JDH Investment Group, LLC April 21, 2016 Information Provided by Jeff Parks on 09.30.19 70 of 350 EXHIBIT 7 Geotechnical Engineering and Geomorphology Services Diamond Valley Estates Development Auburn, Washington for JDH Investment Group, LLC April 21, 2016 8410 154th Avenue NE Redmond, Washington 98052 425.861.6000 Information Provided by Jeff Parks on 09.30.19 71 of 350 Information Provided by Jeff Parks on 09.30.1972 of 350 Table of Contents INTRODUCTION ........................................................................................................................................... 1 Project Background .................................................................................................................................................... 2 SCOPE OF SERVICES ................................................................................................................................. 2 SITE CONDITIONS ....................................................................................................................................... 5 Geologic Setting .......................................................................................................................................................... 5 Soils .............................................................................................................................................................................. 6 Hydrology ..................................................................................................................................................................... 6 Surface Conditions ...................................................................................................................................................... 7 Subsurface Conditions ............................................................................................................................................... 7 Groundwater Conditions ............................................................................................................................................. 9 Laboratory Testing ...................................................................................................................................................... 9 CRITICAL AREAS REVIEW: SLOPES ....................................................................................................... 10 RESPONSE TO COMMENTS – JULY 5, 2011 CITY OF AUBURN STORM DIVISION .............................. 11 Comment 6 ............................................................................................................................................................... 11 Comment 7 ............................................................................................................................................................... 11 Comment 8 ............................................................................................................................................................... 11 Comment 9 ............................................................................................................................................................... 11 RESPONSE TO COMMENTS – AUGUST 1, 2014 CITY OF AUBURN STORM DIVISION ........................ 12 Development Review Engineering Division - Community Development and Public Works Department. ........ 12 Comment 3 ............................................................................................................................................................... 12 Comment 9 ............................................................................................................................................................... 12 Comment 11 ............................................................................................................................................................ 12 Utilities Division - Community Development and Public Works Department ................................................. 13 Comment 9 ............................................................................................................................................................... 13 Comment 10 ............................................................................................................................................................ 13 Planning Services Division - Community Development & Public Works Department ........................................ 14 Comment 19 ............................................................................................................................................................ 14 Comment 20 ............................................................................................................................................................ 14 Comment 21 ............................................................................................................................................................ 14 RESPONSE TO COMMENTS – FEBRUARY 3, 2016 CITY OF AUBURN STORM DIVISION ................... 17 Comment 3. .............................................................................................................................................................. 17 Comment 4. .............................................................................................................................................................. 17 Utilities Division - Community Development & and Public Works Department .................................................. 18 Comment 1. .............................................................................................................................................................. 18 Comment 2. .............................................................................................................................................................. 18 Comment 3. .............................................................................................................................................................. 18 Comment 4. .............................................................................................................................................................. 19 Comment 5. .............................................................................................................................................................. 19 Comment 6. .............................................................................................................................................................. 19 Planning Services Division—Community Development & Public Works Department ......................................... 19 Comment 1. .............................................................................................................................................................. 19 Information Provided by Jeff Parks on 09.30.19 73 of 350 SLOPE STABILITY .................................................................................................................................... 19 General ..................................................................................................................................................................... 19 Pond 1 ....................................................................................................................................................................... 20 Pond 2 ....................................................................................................................................................................... 20 Road F ....................................................................................................................................................................... 21 Lots 7 and 8 ............................................................................................................................................................. 21 Slope Stability Analyses ........................................................................................................................................... 21 Methodology ............................................................................................................................................................. 21 Minimum Factors of Safety ..................................................................................................................................... 22 Horizontal Ground Acceleration .............................................................................................................................. 22 Ponds 1 and 2 .......................................................................................................................................................... 23 Pond 1 ....................................................................................................................................................................... 24 Pond 2 ....................................................................................................................................................................... 24 Road F ....................................................................................................................................................................... 25 Lots 7 and 8 ............................................................................................................................................................. 26 DOWNSTREAM DRAINAGE EVALUATION ............................................................................................... 26 Dispersion Trenches ................................................................................................................................................ 26 Location 1: Pond 1, Wetland A ............................................................................................................................... 26 Location 2: Pond 2, Wetland B, South End ............................................................................................................ 27 Location 3: Pond 2, Wetland B, West Side ............................................................................................................ 27 Location 4: Pond 2, Wetland C ............................................................................................................................... 27 Tributary 0043 ......................................................................................................................................................... 27 Upstream of the Sewer Easement Culvert ............................................................................................................. 28 Downstream from Culvert ....................................................................................................................................... 28 Kersey Road Crossing .............................................................................................................................................. 29 Stream A Reconnaissance ...................................................................................................................................... 29 Stream B Reconnaissance ...................................................................................................................................... 30 DOWNSTREAM CAPACITY AND ERODIBILITY EVALUATION ................................................................. 30 Dispersion Trenches ................................................................................................................................................ 32 DISCUSSION AND CONCLUSIONS .......................................................................................................... 32 General Recommendations .................................................................................................................................... 33 Earthwork.................................................................................................................................................................. 34 Clearing and Site Preparation ................................................................................................................................. 34 Subgrade Preparation ............................................................................................................................................. 34 Structural Fill ............................................................................................................................................................ 35 Temporary Cut Slopes ............................................................................................................................................. 36 Permanent Cut and Fill Slopes ............................................................................................................................... 37 Utility Trenches ......................................................................................................................................................... 37 Sanitary Sewer Main ................................................................................................................................................ 37 Sedimentation and Erosion Control ....................................................................................................................... 38 Foundations .............................................................................................................................................................. 38 Foundation Design ................................................................................................................................................... 38 Foundation Settlement ............................................................................................................................................ 38 Lateral Resistance ................................................................................................................................................... 39 Footing Drains .......................................................................................................................................................... 39 Information Provided by Jeff Parks on 09.30.19 74 of 350 Below Grade Walls and Retaining Walls ................................................................................................................ 39 Design Parameters .................................................................................................................................................. 40 Backdrainage ........................................................................................................................................................... 40 Construction Considerations ................................................................................................................................... 41 Floor Slab Support ................................................................................................................................................... 41 Seismicity .................................................................................................................................................................. 41 Ground Shaking ....................................................................................................................................................... 42 Liquefaction Potential .............................................................................................................................................. 42 Ground Rupture ....................................................................................................................................................... 42 Pavement Recommendations and Subgrade Preparation ................................................................................... 43 Subgrade Preparation ............................................................................................................................................. 43 Asphalt Concrete Pavement .................................................................................................................................... 43 Drainage Considerations ......................................................................................................................................... 43 Grading Considerations ........................................................................................................................................... 44 Benching ................................................................................................................................................................... 44 Proposed Development of Storm Ponds ................................................................................................................ 44 Proposed Development on Slopes Exceeding 40 Percent ................................................................................... 45 Downstream Drainage Mitigation ........................................................................................................................... 45 LIMITATIONS ............................................................................................................................................ 46 REFERENCES .......................................................................................................................................... 46 LIST OF FIGURES Figure 1. Vicinity Map Figure 2. Site Plan Figure 3. Tributary 0043 – Stream Cross Sections Figure 4. Stream Profile Stationing – Tributary 0043 Figure 5. Stream Profile APPENDICES Appendix A. Field Explorations Figure A-1 – Key to Exploration Logs Figures A-2 through A-6 – Log of Monitoring Wells Figures A-7 through A-13 – Log of Test Pits Appendix B. Laboratory Testing Figures B-1 through B-4 – Sieve Analysis Results Figure B-5 –Pebble Count Results Cross Section S1 – S1’ Appendix C. Logs of Previous Field Explorations and Geologic Mapping Appendix D. Results of Slope Stability Analysis Figures D-1 through D-6 – Pond 1 Stability Analysis Figures D-7 through D-10 -- Pond 2 Stability Analysis Figures D-11 and D-12 – Section A3-A3’ Stability Analysis Figures D-13 and D-14 – Section A4-A4’ Stability Analysis Figures D-15 and D-18 – Section A5-A5’ Stability Analysis Appendix E. Apex Slope Map Appendix F. Report Limitations and Guidelines for Use Information Provided by Jeff Parks on 09.30.19 75 of 350 INTRODUCTION This report provides a summary of our geologic, geomorphic, hydrogeologic and geotechnical engineering services for the proposed Diamond Valley Estates development. The site consists of an approximately 80-acre undeveloped parcel located in Auburn, Washington. The site is situated in a ravine on the side slopes of an upland plateau, between the White River and Lake Tapps. Evergreen Way SE crosses the southern part of the parcel, however at this time the site is most readily accessible via Kersey Way SE and through a subdivision to the east. The site location is shown on the Vicinity Map, Figure 1, and the current lot layout, proposed storm ponds and proposed roadways are shown on the Site Plan, Figure 2. This report addresses comments received from Apex Engineering (Apex) on April 16, 2014 and the City of Auburn (City) on August 1, 2014 and later on February 3, 2016. Existing features at the site include locally steep, forested ravine slopes with a small stream and a series of associated wetlands occupying the lower areas of the parcel. We understand the plat concept in its present form includes 200 single-family lots. These lots are laid out on three primary tiers of land that will be significantly re-graded from the existing topography. The subdivision concept includes a stormwater drainage system with two detention ponds (Pond 1 and Pond 2) situated near the toes of steep slopes. The two ponds will be partially cut into the slopes, with retaining walls constructed along their uphill boundaries and retaining walls and fill berms constructed along their downslope boundaries. We understand that the current conceptual configuration of Pond 1 includes a cut made into a northwest facing native slope with a buttress wall at the toe of the cut, transitioning to a fill berm with an inboard retaining wall on the downslope boundary of the pond. We understand that the proposed pond bottom elevation will lie at Elevation 315 feet (NAVD 1988 datum), with the top-of-pond berm elevation at Elevation 330 feet. The top of the retaining walls will also be at Elevation 330 feet. We also understand that the current conceptual configuration of Pond 2 includes a cut made into an east facing native slope with a buttress wall at the toe of the cut, transitioning to a fill berm on the downslope boundary of the pond. A retaining wall will also be constructed on the inboard side of the berm. We understand that the proposed pond bottom will be at Elevation 285 feet, with the top-of-pond berm and top of wall elevations both at Elevation 300 feet. We understand that both ponds are intended to be used for stormwater detention, and neither pond will have graded slopes, inboard or outboard, steeper than 2H:1V (horizontal to vertical). According to the City, the ponds are to be lined. Several new roadways will be constructed for the development, including Road F which will be located in the south half of the development. Road F will cross the broad ravine bottom that extends south to north through the site, and will also cross an existing steep slope area that is inclined at 40 percent or steeper. A fill embankment with an approximate height up to about 40 feet will support the roadway where it crosses the ravine bottom. Fill slope inclinations for the embankment will be at 2H:1V. Cuts will be made uphill of the roadway within the steep slope area; these cuts will be up to about 35 feet in height and will also be inclined at 2H:1V. Much of this grading is intended to create level lots for houses. An existing steep slope inclined at approximately 2H:1V will remain and extend from a segment of Road F down to near the south end of Pond 1. Information Provided by Jeff Parks on 09.30.19 76 of 350 A steep slope area has also been identified within Lots 7 and 8 near the southwest corner of the development. We understand that grading on and near these lots will also result in finished cut slopes of 2H:1V. Project Background GeoEngineers, Inc. (GeoEngineers) presented a revised report to Apex on March 5, 2004 in support of an Environmental Impact Statement (EIS) for the proposed development of the parcel (under the former name of Kersey III Subdivision) that also included other areas beyond the current proposed project. The 2004 report focused on earth and water elements of the EIS, and evaluated surface water and groundwater elements, stormwater detention and discharge features, and steep slope, landslide, and erosion potential. In May and June of 2011, Apex submitted several revised documents for the proposed development (under the former name of Park Ridge Plat) to the City for review, including conceptual site, grading, and storm pond configuration plans, and a conceptual storm drainage report. The purpose of the City’s review was to assist in advancing the development agreement and to provide initial feedback to guide the future preliminary plat application. This report addresses review comments made by the City on July 5, 2011 and additional comments by Apex on August 1, 2014. In particular, we address City comments on the feasibility of proposed stormwater facility concepts and their potential impacts to the stability of steep slopes, other geotechnical considerations, and potential geomorphic impacts related to hydrology of the planned detention facilities. SCOPE OF SERVICES Our services included a geologic/geotechnical assessment of steep slopes for the proposed residential development, and a geotechnical exploration program consisting of test pits and soil borings with monitoring wells to supplement existing subsurface information provided in the 2004 report (GeoEngineers) to further characterize the subsurface soil and groundwater conditions at the proposed detention pond locations and along Road F. We also assessed active geomorphic conditions for the existing wetlands and streams and evaluated potential impacts to those resources from the planned drainage improvements for the development. Our scope of services for this project includes the following tasks: 1. Review available maps, the City’s Critical Areas ordinance, and our report titled “Geologic, Hydrogeologic, and Geotechnical Engineering Services, Proposed Kersey III Subdivision, Auburn, Washington” dated March 5, 2004. Apex has provided numerous maps of the proposed development. We performed field reconnaissance to verify the approximate limits of the Critical Areas. 2. Address City Storm Division Comment 6 dated July 5, 2011 with regard to proposed facilities on slopes greater than 20 percent or those closer than 50 feet to slopes greater than 20 percent. We performed field reconnaissance to confirm limits of slopes greater than 20 percent at pond locations. 3. Address City Storm Division Comment 7 dated July 5, 2011 with regard to facilities on slopes greater than 20 percent or those closer than 200 feet to landslide hazard areas. Apex provided maps to identify critical slopes for scope items 2 and 3. We performed field reconnaissance to confirm landslide hazard areas near pond locations. Information Provided by Jeff Parks on 09.30.19 77 of 350 4. Address City Storm Division Comment 9 dated July 5, 2011 with preliminary stability evaluation of pond berm embankments higher than 6 feet. 5. Participate in project planning and coordination with Apex staff, including meetings, conference calls and other correspondence. We understand that a more detailed design will be prepared for development of construction plans. 6. Coordinate equipment access for our subsurface exploration programs with Apex and the City. 7. Evaluate subsurface conditions associated with proposed detention Ponds 1 and 2 to more completely address City Storm Division Comment 9 dated July 5, 2011 with preliminary slope stability evaluation of pond berm embankments higher than 6 feet. We understand that on-site infiltration (retention) is not proposed for these ponds. Based on information provided by Apex on March 19, 2014, we understand that the bottom of Pond 1 will be at approximately Elevation 315 feet and the bottom of Pond 2 will be at approximately Elevation 285 feet. The ponds are to be lined, as required by the City. Given these parameters we completed the following tasks: a. Coordinated a request for underground utility locates through the Washington State one-call system, as required by state law. Considering that the property is privately owned and utility companies will not clear utilities outside public right-of-ways and easements, we also subcontracted a private locate service to clear utilities prior to completing explorations. b. Coordinated site access for the drilling and test pit excavating subcontractors. c. Completed three borings (B-6, -7 and -9) and two test pits (TP-25 and -26) in the vicinity of proposed Pond 1. The southern portion of Pond 1 is located at the base of steep slopes (estimated inclination of 2H:1V). The borings provided soil strength data that was used in the preliminary slope stability analysis for the finished pond slopes. Borings were completed to approximately 10 to 12 feet below proposed pond bottom level for stability analysis. We encountered seepage (advance outwash aquifer) near the maximum projected pond depth that will require specific drainage measures. The excavator used for the test pits on the shallower north side of the pond was also used to provide access for a track-mounted drill rig for the three Pond 1 borings. The drilling program included the installation of three 2-inch-diameter stand pipe monitoring wells for recording groundwater levels and potentially for aquifer testing. Vibrating wire pressure transducers with data loggers have been installed in each of the monitoring wells to continuously record groundwater levels. A staff geologist observed the drilling and test pit activities and coordinated with the subcontracted excavator to provide access for drilling equipment. d. Completed one boring (B-8) and one test pit (TP-24) for Pond 2. We completed the boring to approximately 5 feet below the proposed pond bottom level (31½-foot depth) for use in the preliminary slope stability analysis. 8. Evaluate subsurface conditions associated with the segments of Road F that will cross the ravine and the identified steep slope area. This evaluation is intended to address the City’s review comments dated August 1, 2014 with preliminary slope stability evaluation of the cut and fill slopes across the ravine and within the steep slope area. In support of this evaluation, we completed two soil borings (B-11 and -9) and four test pits (TP-27 through -30). 9. Conduct a limited geotechnical laboratory testing program including grain size analyses and moisture content tests to characterize representative soil samples from the borings and test pits. Information Provided by Jeff Parks on 09.30.19 78 of 350 10. Perform slope stability analyses using our laboratory test results and exploration data to address City Storm Division Comment 9 dated July 5, 2011 on preliminary slope stability evaluation of pond berm embankments higher than 6 feet. 11. Perform preliminary slope stability analyses to address City Storm Division Comments dated August 1, 2014 on stability evaluation of cuts and fills related to Road F and the identified steep slope areas. 12. Assist Apex in completing a variance request for the section of Road F that will cross steep slopes and also the grading of Lots 7 and 8 in an identified steep slope area. 13. Conduct a qualitative geomorphic evaluation to further characterize the capacity, composition, and erodibility of the stream channel and drainage downstream of the project site’s wetlands to address the City comments (dated August 1, 2014) on the Preliminary Plat submittal. In addition, we reviewed composition and erodibility of the stormwater pond dispersion trench discharge area into the wetlands. Our scope of services included a desktop study and a one-day field reconnaissance. Tasks included the following: a. Reviewed existing information and analyses completed to date about the stream, including but not limited to, the Revised Report, Geologic, Hydrogeologic and Geotechnical Engineering Services for the Proposed Kersey III Subdivision (GeoEngineers 2004); file documents and field notes; and City documents for the Lakeland Hills Estates subdivision (adjacent to the east); project information about the proposed stormwater system from Apex and wetland information from Raedeke Associates; updated geology and soils information, LiDAR imagery and topography from years 2003 (King County) and 2010 (Pierce County). b. Developed a stream profile from the LiDAR imagery to identify existing areas of active erosion in the stream channel and valley. c. Completed a field stream reconnaissance to evaluate current conditions in the downstream channels and to identify topographic and geomorphic features, potential sediment sources and areas of significant erosion both in-channel and in upland areas proximal to the creek. d. Measured channel cross sections in two locations to correlate observed field conditions with approximate stream channel capacity (estimated from site topographic information). e. Conducted a reconnaissance at the four dispersion trench locations that will discharge from stormwater ponds to the site wetlands to characterize the existing conditions and evaluate potential erosion hazards associated with the dispersion trench discharge flow. 14. Review and address City comments dated August 1, 2014 in a revised final geotechnical report to support the preliminary plat. A geotechnical report addressing specific design issues will be prepared as part of the final design process under a separate proposal. Specifically relative to City comments dated February 3, 2016, our revised geotechnical and geomorphology report includes: 15. Benching (terracing) recommendations relative to recommended vertical spacing (Development Review Engineering Division Comment 3). 16. Recommendations relative to keying in fill placed on slopes (Development Review Engineering Division Comment 4). Information Provided by Jeff Parks on 09.30.19 79 of 350 17. Provide the entire report dated March 5, 2004 (Utilities Division – Community Development and Public Works Comment 3). We also provide an updated figure with conventionally surveyed slopes and text that addresses surface observations relative to areas of seepage, evidence of erosion and condition of tree trunks (e.g. bowed conifer tree trunks). After further discussion the City stipulated they would defer a decision on whether to require a “full depth boring from the top to toe of slopes” until after they had reviewed the 2004 report. Such a boring, if required, would be almost 300 feet in depth. 18. Revised slope stability analyses (Utilities Division – Community Development and Public Works Comment 4) that show a higher factor of safety (greater than 1.0). We also discussed during the meeting providing examples and discussion of other jurisdiction’s minimum factor of safety requirements (WSDOT and City of Bellevue) since the city could not provide minimum factor of safety values corresponding to their code at the time of our meeting. 19. Additional explanation of slope stability modeling performed (Utilities Division – Community Development and Public Works Comment 5). 20. Analysis demonstrating increased static factor of safety for the uphill cut slope at Road F (Utilities Division –Community Development and Public Works Comment 16). 21. A Critical Area Slope exhibit provided by Apex that is referenced but was not included in the original geotechnical report (Planning Services Division – Community Development and Public Works Comment 1). SITE CONDITIONS Geologic Setting The site is situated on an upland area east of a broad alluvial valley that is shared by the White and Green Rivers, and includes a small drainage ravine fed by Lake Tapps from the plateau to the southeast (Figure 1). The area has been impacted by episodic glaciation throughout the past 2.4 million years and by tectonic deformation associated with the Cascadia Subduction Zone. The landscape in the vicinity of the project site has formed largely as a result of repeated cycles of glacial scouring and deposition, and tectonic activity, and has also been modified by landsliding, stream erosion and deposition, and human activity. In general, the site is underlain by a ½- to 2-foot thickness of forest duff and topsoil, which in turn overlies one of four distinct geologic units – specifically fill, ice contact deposits, glacial till and advance outwash. The fill is undocumented, and some of it was observed to contain organic matter. The ice contact, glacial till, and advance outwash deposits are primarily sandy materials with variable clay, silt, gravel, cobble and boulder content. The organic soils (forest duff and topsoil) and non-engineered fill are often relatively compressible, and large settlements can potentially occur when new loads are placed over these materials. The geologic units mapped in the area by Mullineaux (1965) include four primary units, from youngest to oldest: (1) Fill (map symbol: Hf); (2) Vashon ice contact deposits (Qvi); (3) Vashon till (Qvt); and (4) Vashon advance outwash deposits (Qva). The ice contact, till, and advance outwash units were deposited during the most recent glaciation of the region, which occurred 13,000 to 15,000 years ago (during the Quaternary period), and is known as the Vashon stade of the Fraser glaciation. Recently placed fill is present over glacial deposits (Qvt or Qvi) in localized areas across the site. Information Provided by Jeff Parks on 09.30.19 80 of 350 Vashon ice contact deposits (Qvi) resulted from deposition upon, within, or near stagnating glacier ice during glacier retreat. These deposits are characterized by stratified sand and gravel with local occurrences of till. Ice contact deposits at the site generally consist of a medium dense to dense mixture of sand, silt and gravel, with cobbles and boulders. Vashon till (Qvt) consists of compact, poorly sorted, nonstratified pebbly sandy silt or silty sand with occasional cobbles and boulders. Qvt includes lodgment till, which is generally dense to very dense as a result of having been deposited at the base of the glacier and overridden by thousands of feet of ice, and ablation till, which is generally loose as a result of having melted out from entrainment in glacier ice. Till at the site generally consists of dense to very dense, gray to grayish-brown silty sand with gravel, cobbles and occasional boulders. Vashon advance outwash (Qva) typically consists of well-sorted, well-stratified sand and pebbly sand representing meltwater deposits carried from the advancing front of the glacier. These sediments were deposited by streams flowing from the advancing ice sheet during the Vashon stade. Qva at the site generally consists of dense to very dense, gray-brown gravelly sand with cobbles and silt. Vashon advance outwash is mapped within the north-central portion of the site. Soils Site soils have been mapped by the United States Department of Agriculture (USDA) Soil Conservation Service (SCS; accessed from Web Soil survey, http://websoilsurvey.nrcs.usda.gov on November 26, 2014). The Diamond Valley Estates property in the vicinity of the wetlands and proposed stormwater system is underlain by Alderwood gravelly sandy loam on 8 to 15 percent slopes (map symbol: AgC). It forms on hills and ridges underlain by glacial drift and/or glacial outwash. Minor soil units in the project area include McKenna, Shalcar, and Norma soils in depressions and drainage ways and Everett soils on ridge crests. Gravel content in Alderwood soils increases with depth and the soil becomes very gravelly below 7 inches. The soil is moderately well drained and subject to neither ponding nor flooding. Alderwood C soil has a whole soil K factor of 0.10, a rating of susceptibility to sheet rill and erosion and a component of the Universal Soil Loss Equation. K factor ranges from 0.02 to 0.69. In general, the higher the K number rating, the more susceptible to sheet rill and erosion the soil is, other factors being equal. The soil has an off-road, off-trail erosion hazard rating of slight, indicating that little or no erosion is likely on disturbed areas under normal conditions. The road and trail erosion hazard rating for Alderwood C soils is moderate, but roads and trails would not be expected to be developed in the wetland buffer areas downstream of the dispersion trenches. On slopes greater than 15 percent, the Alderwood soils road and trail erosion hazard rating increases to severe (GeoEngineers 2004). Hydrology The following section has been excerpted from the Kersey III Draft EIS Water section (GeoEngineers 2004) and updated for this report. The site is located within Water Resources Inventory Area (WRIA) 10, the Puyallup-White watershed, which drains approximately 1,050 square miles in King and Pierce counties. Five wetlands (Wetlands A, B, C, D and 1) and an unnamed intermittent stream are present in the northeastern portion of the site. The headwaters of the intermittent stream are located in the vicinity of Wetland 1. Information Provided by Jeff Parks on 09.30.19 81 of 350 Surface water runoff from the western portion of the site flows into unnamed tributary number 0043, also referred to as Stream AB in project documents. A September 2002 stream reconnaissance observed erosion and blockage at the Kersey Way (stream station 17+00) culvert where an approximate 3-foot-high cascade at the culvert outlet indicated a perched culvert condition. Based on our November 2014 reconnaissance, the culvert outlet appears to have been reconstructed and the erosion has stopped. The unnamed tributary discharges into Bowman Creek approximately 100 feet downstream of Kersey Way and approximately 1,000 feet downstream of the midpoint of Bowman Creek. Bowman Creek discharges into the White River, a Class A surface water. Surface Conditions The site consists of a ravine that is bounded by two ridges and that generally slopes downward from south to north. The ravine intersects the southern site boundary at approximate Elevation 470 feet and slopes down toward the northeast where it intersects the northern site boundary at approximate Elevation 220 feet. Slope aspects are dominantly east-facing in the western portion of the site, northwest-facing in the southeastern portion of the site, and northeast-facing in the southwestern and northeastern portions of the site. The western and southeastern portions of the site contain the steepest native slopes on the parcel, with slopes that are generally greater than 20 percent, and that locally exceed 40 percent along proposed Road F and the vicinity of Lots 7 and 8 in the southern half of the parcel. Site topography is shown on Figure 2. The design of the development will be heavily influenced by the existing topography as well as City of Auburn design guidelines. In general, site development will attempt to follow existing contours, but cuts up to 35 feet high and fills up to 40 feet high are anticipated for construction of the main roadways (such as Road F) through the proposed subdivision. Secondary roads and cul-de-sacs will also require modification of the existing topography to achieve smooth transitions between the main roadway and building lots. Approximately 90 percent of the site consists of forested areas with second growth conifers (primarily Douglas fir) and deciduous species (e.g., alder and big leaf maple). Undergrowth includes salmonberry, sword fern, salal, Oregon grape, blackberry, grass and other species typical of forested areas in the Puget Sound region. Undergrowth in wetland areas located in the eastern portion of the site also includes nettles, skunk cabbage and vine maple. Results of our surface reconnaissance observations relative to the City Critical Areas code are provided below in our Critical Areas Review section. Subsurface Conditions We explored subsurface soil conditions at the site in the vicinity of the proposed storm ponds and in the vicinity of Road F by drilling five geotechnical borings (B-6 through B-9 and B-11) to depths ranging from 31½ to 100 feet below the existing ground surface (bgs), and by excavating seven test pits (TP-24 through -30) to depths ranging from 11 to 14 feet bgs. Boring B-11 was located in the approximate area where the greatest thickness of fill will be placed across the drainage swale. Each of the borings included installation of a 2-inch-diameter monitor well. The borings were drilled in March and November 2014 using track-mounted hollow stem auger, mud rotary, and sonic drilling equipment. The test pits were excavated during the same time periods using a track hoe excavator. The exploration locations are shown on Figure 2. Information Provided by Jeff Parks on 09.30.19 82 of 350 A description of the field methodology, logs of the borings and test pits, and equipment used are presented in Appendix A. A description of the geotechnical laboratory testing procedures and the results of the laboratory tests are presented in Appendix B. Previous subsurface explorations were completed by GeoEngineers on the subject parcel in June and July 2002 (GeoEngineers, 2004) which included the drilling of three borings (B-1 through B-3) and the excavation of 14 test pits (TP-1 through TP-14) (Appendix C). Two of the three previously completed borings included piezometers, which at the time of our current study are non-functioning. This report focuses on the recent explorations completed in March and November 2014, however logs for previous explorations are presented in Appendix C and more detailed information relating to the previous explorations can be found in our revised Kersey III Subdivision report (GeoEngineers, 2004). The soils encountered in our explorations are consistent with the mapped geologic units. Each of these soil units is described below. Fill located within the southern portion of the site includes subgrade material for an existing paved roadway (Evergreen Way SE). The fill generally consists of medium dense silty sand with gravel and occasional cobbles, and appears to be re-worked till (Qvt) and ice contact deposits (Qvi) that originated on site. Minor amounts of fill (less than 1 foot thick) consisting of loose to medium dense silty sand were observed in the northeastern portion of the site in test pit TP-24. Vashon ice contact deposits (Qvi) were encountered beneath the fill in test pit TP 24. Qvi was also encountered at or just below the ground surface in test pits TP-25 through TP-30 and in all five borings (B-6 through B-9, and B-11). Vashon ice contact deposits are mapped within the western, central and lower-elevation areas of the site. The on-site Vashon ice contact deposits are interpreted to have a maximum thickness of approximately 40 feet, and are underlain by Vashon till or Vashon advance outwash. Our subsurface explorations indicate that Qvi is more widely distributed at the site than indicated by existing geologic maps (Mullineaux, 1965; Luzier, 1969). Vashon till (Qvt) was identified beneath Vashon ice contact deposits in test pits TP-25 through TP-30, and in borings B-8, B-9, and B-11. Till was also identified in four previously completed on-site test pits (GeoEngineers, 2004). Vashon till is generally mapped within the higher-elevation areas of the site. The Vashon till unit is likely underlain by Vashon advance outwash or possibly by Salmon Springs (older than Vashon age) drift. Vashon advance outwash (Qva) was encountered in all of the explorations in the vicinity of proposed Pond 1, but in none of the explorations in the vicinity of proposed Pond 2. Qva was encountered beneath an approximate 10-foot thickness of Vashon ice contact deposits in boring B-6, and beneath approximately 15 feet of ice contact and till deposits in boring B-7. Qva was also encountered beneath 6½ and 9 feet of ice contact and till deposits in test pits TP-25 and TP-26, respectively. Refer to Appendix A for details. Heaving sands (saturated sands below the groundwater table that are prone to flowing when excavated) were encountered in the advance outwash zone in boring B-7 between depths of approximately 37½ and 51 feet (approximate Elevation 303 to 317 feet). Similarly, the sidewall of test pit TP-26 experienced complete collapse during excavation into the saturated sands below a depth of 8 feet. The saturated sand conditions will be a consideration when Pond 1 is excavated into the native slope to the south (Figure 2). Information Provided by Jeff Parks on 09.30.19 83 of 350 Additional detailed discussion regarding the geologic units in the study area is presented in our revised Kersey III subdivision report (GeoEngineers 2004). Groundwater Conditions We installed monitoring wells in each of the borings following drilling to allow subsequent measurement of groundwater levels. The monitoring wells are the property of the project owner. The wells should be decommissioned by a licensed well driller in accordance with Chapter 173-160 of the Washington State Administrative Code (WAC) when they are no longer needed for data collection. Alternatively, the wells could be kept intact for use during project bidding and then be decommissioned under the construction contract. Updated groundwater level measurements at monitoring wells B-6, B-7, and B-8 along with those observed during drilling of B-9 and B-11 are provided in the logs included in Appendix A. Localized zones of shallow groundwater were encountered within Vashon-age glacial deposits in three of our borings (B-6 through B-8) and three test pits (TP-24 through TP-26). Shallow lenses of wet soil and perched groundwater were also encountered in explorations previously completed at the site (GeoEngineers, 2004). These shallow zones of groundwater were typically encountered at depths of 5 to 35 feet beneath the ground surface, in 2- to 10-foot-thick lenses of sand or silty sand that were underlain by sediments with lower permeability. Groundwater was observed at a depth of 78 feet bgs in B-9, which is located upslope relative to other wells. Groundwater was not observed in test pits TP-27 through TP-30 during the time they were open. These shallow groundwater zones are perched on localized deposits of low permeability sediments. Groundwater flow within these shallow perched zones is expected to mimic the topography and travel in down-slope directions. Shallow groundwater on the western, southern, and southeastern portions of the site flows toward the wetlands shown on Figure 2. Shallow groundwater in the northeastern portion of the site generally flows toward the north. A fraction of shallow groundwater at the site is also expected to migrate downward and provide recharge to the deeper regional aquifers. Based on existing studies of the area, the shallowest regional or laterally extensive aquifer beneath the site occurs within the Vashon advance outwash (Qva) sediments at an inferred elevation of approximately 300 to 350 feet (Luzier 1969; Woodward et al. 1995). However, existing geologic maps (Mullineaux 1965; Luzier 1969), cross sections (Hart Crowser 1982), and well logs (Ecology, 2002) in the site vicinity also indicate that the presence of the Qva aquifer is uncertain beneath the southern portion of the site and is absent beneath the northwestern portion of the site. Where present, groundwater within the Qva aquifer beneath the site is inferred to flow north, toward the White River. Laboratory Testing Soil samples were obtained from the explorations for further evaluation and geotechnical laboratory testing. Selected samples were tested for the determination of moisture content and sieve analyses. A description of the geotechnical laboratory testing program and the test results are presented in Appendix B. Information Provided by Jeff Parks on 09.30.19 84 of 350 CRITICAL AREAS REVIEW: SLOPES The City (2014) defines landslide hazards relative to slope hydrology and underlying soils as follows (Chapter 16.10.020 Definitions): “Landslide hazard areas” means areas that, due to a combination of slope inclination, relative soil permeability, and hydrologic conditions are susceptible to varying degrees of risk of landsliding. Landslide hazard areas are classified as Classes I through IV based on the degree of risk as follows: 1. Class I/Low Hazard. Areas with slopes of 15 percent or less. 2. Class II/Moderate Hazard. Areas with slopes of between 15 percent and 40 percent and that are underlain by soils that consist largely of sand, gravel or glacial till. 3. Class III/High Hazard. Areas with slopes between 15 percent and 40 percent that are underlain by soils consisting largely of silt and clay. 4. Class IV/Very High Hazard. Areas with slopes steeper than 15 percent with identifiable zones of emergent water (e.g., springs or ground water seepage), areas of identifiable landslide deposits regardless of slope and all areas sloping more steeply than 40 percent.” Our surface and subsurface observations of the site indicate that there are three types of landslide hazards within the site. The site generally includes Class I/Low Hazard and Class II/Moderate hazard areas with slopes between 15 and 40 percent underlain by soils that consist of sand, gravel and glacial till. We observed no Class III/High Hazard Areas with slopes between 15 and 40 percent that are underlain by soils consisting largely of silt and clay. The site also includes those areas identified by Apex (2016) that include localized slopes exceeding 40 percent that meet the Class IV/Very High Hazard criteria in the vicinity of Road F and Lots 7 and 8 (Figure 2 and Appendix E Figure E-1). We note that for this site, these criteria are met strictly by slopes exceeding 40 percent. We observed no areas with identifiable landslide deposits or slopes steeper than 15 percent with identifiable zones of emergent water during our site reconnaissance on March 20 and November 17, 2014. We did note areas of surface water in the vicinity of both wetlands A and B during our March 20 reconnaissance, consistent with wetland hydrology discussed by other project team members. Furthermore, according to Apex, the planned construction of Road F includes the grading and placement of fill in the swale downslope of the existing slope that is greater than 40 percent. Placing this fill will buttress the toe of the existing steep slope when constructed. The City Critical Areas Ordinance prohibits alteration of Class IV/Very High Hazard areas (16.10.100). The City does recognize performance standards for mitigation planning within geologic hazards that include the limited use of retaining walls that minimize disturbance or alteration among other approaches to reduce alteration (16.10.120, Performance standards for mitigation planning). The project may also be required to apply for a Variance (section 16.10.160, Variances) as suggested by the City (August 1, 2014): “The project should apply for a variance, demonstrating need for the proposed Road F alignment and grading of Lots 7 and 8 across the slopes that exceed 40 percent.” Information Provided by Jeff Parks on 09.30.19 85 of 350 RESPONSE TO COMMENTS – JULY 5, 2011 CITY OF AUBURN STORM DIVISION The following section addresses comments made by the City Storm Division on documents submitted to the City by Apex in 2011, including conceptual site, grading, and storm pond grading plans, and a conceptual storm drainage report. The comments made by the Storm Division focus on the feasibility of proposed stormwater facility concepts with regard to impacting the stability of steep slopes, and to other geotechnical considerations. Comment 6 All [storm drainage system] facilities shall be a minimum of 50 feet from any slope greater than 20 percent. A geotechnical report must address the potential impact of a wetpond on a slope steeper than 20 percent or if closer than 50 feet. Response: The proposed storm pond concept includes ponds that will be constructed on, or within 50 feet of, slopes steeper than 20 percent. We performed slope stability analyses for the uphill cut slopes and the downhill fill berms for both ponds under static and pseudo static (seismic) loading conditions. The results of our analyses and our recommendations to achieve an adequate factor of safety against sliding are described in the Slope Stability section below. Comment 7 A geotechnical analysis is required for slopes 20 percent or greater, or if located within 200 feet of the top of a slope 20 percent or greater or landslide hazard area. The scope of the geotechnical report shall include the assessment of impoundment seepage on the stability of the natural slope where the facility will be located within the setback limits set forth in the section. Response: We note that comments from the City in 2016 now require a liner for the ponds reducing the potential impact of seepage. The site generally includes slopes between 15 and 40 percent underlain by soils that consist of sand, gravel and glacial till and localized slopes that exceed 40 percent in the vicinity of Road F and Pond 1, and also in the vicinity of Lots 7 and 8 (Figure 2). We observed no areas with identifiable landslide deposits or slopes steeper than 15 percent with identifiable zones of emergent water during our site reconnaissance on March 20 and November 17, 2014. Refer to the Slope Stability section below for further information about slope stability Comment 8 Exterior pond side slopes must not be steeper than 2H:1V unless analyzed for stability by a geotechnical engineer. Response: No exterior pond slopes are proposed to be steeper than 2H:1V in the current storm pond design concept. Fillslopes are designed with a 2H:1V slope that includes a geotextile mesh to provide an acceptable slope stability factor of safety. Comment 9 Pond berm embankments higher than 6 feet must be designed by a professional engineer with geotechnical expertise. Information Provided by Jeff Parks on 09.30.19 86 of 350 Response: We completed slope stability analyses for the Ponds 1 and 2 berm embankments for both static and seismic loading conditions. The results of our analyses and preliminary recommended measures to achieve an adequate factor of safety against sliding for both static and seismic loading conditions are presented below. RESPONSE TO COMMENTS – AUGUST 1, 2014 CITY OF AUBURN STORM DIVISION Development Review Engineering Division - Community Development and Public Works Department. Comment 3 The project proposes to substantially alter the hydrologic input to the site's wetlands which flow to the site streams and eventually the White River, off-site. As a result, additional characterization is needed of the downstream channels, including such information as capacity, composition, erodibility, etc. The report contents need to also take into consideration that there is an outlet to the stream from the adjacent plat of Lakeland Hills Estates (File Nos. PLT14-0002, FAC0?-0016). Response: A qualitative stream evaluation is included within this document that addresses characterization of downstream channels inclusive of the Lakeland Hills Estates. . Comment 9 Sheet 15 -CONCEPTUAL GRADING PLAN- Please provide cross-sections. Please show clearing limits on the conceptual plans. A slope restoration plan will be required prior to construction authorization that addresses timing, methods and duration of exposure of the developable lots as well as the 2:1 cut and fill slopes. Provide additional characterization of the downstream channels that will be receiving flows from the developed ponds, including such information as capacity, composition, erodibility, etc. Also, please show the location of the outlet to the stream from the outlet on the adjacent subdivision of Lakeland Hills Estates. Due to the significant amount and extent of clearing and grading proposed, the site clearing, grading, stabilization, pond, and road work it is anticipated the City will consider conditions that require this work to occur during the summer construction season. The Applicant should be aware and consider this in their approach to the project construction schedule. Please show on the plan the locations where soil investigations were performed. Topsoil for all landscaped areas within the plat must be in compliance with Washington State Department of Ecology (WSDOE) Best Management Practice (BMP) T5.13. The grading plan for the plat should make allowance for any import of topsoil per this BMP. Response: A qualitative stream evaluation is included within this document that addresses characterization of downstream channels inclusive of the Lakeland Hills Estates. We agree that site clearing, grading, stabilization, pond, and road work should occur during summer construction season. Comment 11 Sheet 19- CRITICAL SLOPE EXHIBIT- It appears that there are some areas where slopes in the range of 30 to 40 percent and slopes greater than 40 percent exist, but are not identified. Please identify. Please show on the plan all 4 classes of landslide geologic hazard areas in accordance with the City's critical area regulations (ACC 16.10.080(G)). The plans shows locations of critical slopes where Lots 74-77 and Roadway F are proposed. In accordance with the City's critical area regulations Information Provided by Jeff Parks on 09.30.19 87 of 350 (ACC 16.10.1OO(E)), the alteration of Class IV landslide geologic hazard areas is prohibited except as subject to the reasonable use provisions of the critical areas code. Response: An updated existing slope exhibit is provided (Apex, 2016) that includes slope areas identified as Class I, II and IV landslide hazard areas throughout the project site. The figure is included in Appendix E No Class III areas were identified within the project site. Furthermore, other comments from the City indicate that a variance application for the alteration of Class IV slopes will be considered as “reasonable use” provisions are not supported. Utilities Division - Community Development and Public Works Department Comment 9 The City anticipates the following condition of preliminary plat approval: Prior to issuance of clearing or grading permits, a grading plan for grading and clearing necessary for both the construction of infrastructure such as roads and utilities and for lot grading shall be prepared, submitted and approved by the City of Auburn. The purpose of the plan is to accomplish the maximum amount of grading at one time to limit or avoid the need for subsequent grading and disturbance, including grading of individual lots during home construction. The plan shall identify the surveyed boundary of the crest slopes for the site's 40% or greater slopes. This plan shall show quantities and locations of excavations, and embankments, the design of temporary storm drainage detention system, and methods of preventing drainage, erosion and sedimentation from impacting adjacent properties, natural and public storm drainage systems and other nearby sensitive areas. All the measures shall be implemented prior to beginning phased on-site filling, grading or construction activities. The Applicant's grading plans shall be prepared in conjunction with and reviewed by a licensed geotechnical engineer. The geotechnical engineer shall develop and submit, for the City's review, specific recommendations to mitigate grading activities with particular attention to developing a plan to minimize the extent and time soils are exposed on site and address grading and related activities during wet weather periods (the period of greatest concern is October 1 through March 31). The plans shall show the type and the extent of geologic hazard area or any other critical areas as required in chapters 16, and 18 of the International Building Code (IBC),(Policy EN-69, EN-70, ACP) and/or the City's Critical Areas Ordinance. Response: A clearing and grading plan that meets the requirements above will be developed during final design. We recommend that all clearing and grading will be completed during the dry season (typically May 1 through September 30) and during periods of extended dry weather. Likewise, we recommend that no grading or clearing activities be completed during extended periods of wet weather than may occur during the dry season. We recommend that grading and erosion control plans be developed during final design. Comment 10 The City anticipates the following condition of preliminary plat approval: Upon completion of rough grading and excavation, the Applicant shall have a geotechnical engineer re-analyze the site and determine if new or additional mitigation measures are necessary. A revised geotechnical report shall be submitted to the City of Auburn for review and approval by the City Engineer. Recommendations for areas where subsurface water is known or discovered shall be given particular attention by the geotechnical engineer and coordinated with the project engineer responsible for the storm drainage system design as part of a Facility Extension Plan (FAC) and Grading Plan (GRA) preparation. Information Provided by Jeff Parks on 09.30.19 88 of 350 Response: We anticipate that re-evaluation of the site conditions will be completed following rough grading and excavation to refine drainage design. We recommend that GeoEngineers or another qualified professional complete the re-evaluation in general accordance with the city comment 11 above. Planning Services Division - Community Development & Public Works Department Comment 19 Regarding Sheet 19 of 19, 'Critical Slope Exhibit', in accordance with the City's critical areas standards as contained in ACC 16.10.080(G)(2) which defines "Class IV Landslide Hazard Areas" as all areas with slopes 40 percent or greater and ACC 16.10.100 (E)(2)(a) which prohibits alteration of Class IV Landslide Hazard Areas subject to the reasonable use provisions of this Critical Areas Code, the project proposes grading and alteration of Class IV Landslide Hazard Areas within the southwest corner of the plat for Tract A, open space and adjacent Lots 7 and 8 and grading and alteration of Class IV Landslide Hazard Areas within near the south-central portion of the plat for "Road F", Lots 74 through 77 and Tract I, a storm drainage tract. Observance of these standards could result in a reduction of thirteen lots, foreshortening of Road F, and redesign of storm facilities in Tract I. Response: A variance will be sought for Road F, Tract I, and Lots 74 through 77 (now re-numbered Lots 71 through 73) and lots 7 and 8. Comment 20 Please ensure that Sheet 19 of 19, 'Critical Slope Exhibit', agrees with information in the report: Geotechnical Engineering Services, Diamond Valley Estates Development, Auburn WA, GeoEngineers, April 18, 2014. Response: An existing slope exhibit has been updated as requested that includes specific slope classes used to define landslide hazard areas identified within the site (Class I, II and IV). The figure is provided in Appendix E. Comment 21 Geotechnical Engineering Services, Diamond Valley Estates Development, Auburn WA, GeoEngineers, April 18, 2014. On pages 7-9 and 13-14, the report describes the project's relationship to the city's critical area regulations of ACC 16.10 and identifies that the site contains Class II /Moderate Hazard areas and Class IV/ Very High Hazard Areas. Regarding one of the Very High Hazard areas identified within the site, the report notes: According to Apex, the planned construction of Road F includes the grading and placement of fill in the swale down slope of the existing slope that is greater than 40 percent that should effectively buttress the toe of the slope when constructed." The report goes on to note that the City's critical area ordinance prohibits alteration of Class IV/Very high Hazard Slopes (ACC 16.10.100) and that the project may be required to apply for a 'Reasonable Use Provision" (ACC 16.10. 150) demonstrating the need for the proposed Road F alignment across the slopes that exceed 40 percent. The report repeats the City's criteria for the "Reasonable Use" but does not explain how the proposal may or may not fit the criteria. The project does not appear to meet the criteria. Information Provided by Jeff Parks on 09.30.19 89 of 350 11ACC 16.10.160 Variances. Applications for variances to the strict application of the terms of this chapter to a property may be submitted to the city. Minor variances, defined as up to and including 10 percent of the requirement, may be granted by the director as a Type II decision as defined by Chapter 14.03 ACC. Variance requests which exceed 10 percent may be granted by the hearing examiner as a Type Ill decision, pursuant to ACC 14.03.030 and Chapter 2.46 ACC. Approval of variances from the strict application of the critical area requirements shall conform to the following criteria: A. There are unique physical conditions peculiar and inherent to the affected property which make it difficult or infeasible to strictly comply with the provisions of this section; B. The variance is the minimum necessary to accommodate the building footprint and access; C. The proposed variance would preserve the functions and values of the critical area, and/or the proposal does not create or increase a risk to the public health, safety and general welfare, or to public or private property; D. The proposed variance would not adversely affect surrounding properties adjoining; E. Adverse impacts to critical areas resulting from the proposal are minimized; and F. The special circumstances or conditions affecting the property are not a result of the actions of the applicant or previous owner. (Ord. 6442 § 14, 2012; Ord. 5894 § 1, 2005)." Variance for Road F Tract I, and lots 71 through 73 (former lots 74-77) A. There are unique physical conditions peculiar and inherent to the affected property which make it difficult or infeasible to strictly comply with the provisions of this section, Response: The project includes a northeast oriented drainage swale with a creek and wetlands that divides the project area. The proposed Road F provides roadway connectivity to the Gillette project to the east (Geotech Consultants, 2008) that has already or is expected to receive preliminary plat approval. The roadway grades do not allow development of Road F, Lots 71 through 73 and Tract I from upslope of the locally greater than 40 percent slope area. The proposed Road F, Lots 71 through 73 and Tract I include localized slopes that are greater than 40 percent that slope north toward the drainage swale that includes Wetland A. Development of Road F, Lots 71 through 73 and Tract I avoids Wetland A impact but requires some placement of fill locally and cuts. Road F, Lots 71 through 73 and Tract I cross the project site within the lower portion of the slope that includes a slope greater than 40 percent, with a fill embankment and cut slope that avoids impacts to Wetland A. The above listed conditions make it necessary to obtain a variance in accordance with 11ACC 16.10.160 B. The variance is the minimum necessary to accommodate the building footprint and access; Response: Apex Engineering indicates that the variance includes a standard Road F road width and lot size in accordance with City of Auburn code. These design features are the minimum required in accordance with the Code. C. The proposed variance would preserve the functions and values of the critical area, and/or the proposal does not create or increase a risk to the public health, safety and general welfare, or to public or private property; Information Provided by Jeff Parks on 09.30.19 90 of 350 Response: Re-grading of the slopes greater than 40 percent will avoid impacts to Wetland A to preserve wetland function. A slope stability analysis follows to show an acceptable factor of safety to avoid creating or increasing a risk to public health, safety and general welfare or to public property associated with the proposed Road F, Lots 71 through 73 and Tract I. D. The proposed variance would not adversely affect surrounding properties adjoining; Response: No grading is proposed on adjacent properties associated with the development of Road F, Tract I, or Lots 71 through 73. The development of Road F, Tract I, or Lots 71 through 73 is not expected to adversely affect adjoining properties. E. Adverse impacts to critical areas resulting from the proposal are minimized; and Response: The development of Road F, Tract I, or Lots 71 through 73 avoids impact to Wetland A and locally regrades the slope greater than 40 to 50 percent with a minimum road width and lot size accordingly. We provide a slope stability analysis and provide preliminary concepts for a design to increase slopes greater than 40 percent locally to 50 percent. F. The special circumstances or conditions affecting the property are not a result of the actions of the applicant or previous owner. (Ord. 6442 § 14, 2012; Ord. 5894 § 1, 2005.)" Response: These specific circumstances or conditions affecting the property are the result of natural processes that created the physical conditions at the site (as described above) and are not the result of actions of the applicant or previous owner. Variance for Lots 7 and 8 A. There are unique physical conditions peculiar and inherent to the affected property which make it difficult or infeasible to strictly comply with the provisions of this section, Response: The project includes a northeast oriented drainage swale that divides the project area. Lots 7 and 8 are located along east-facing slopes locally inclined at gradients that exceed 40 percent. The grades for the area are such that a fill (as opposed to a cut) for these two lots will have consequences for the intersection at Road G with Evergreen Way SE. Therefore a localized cut with a mid-slope bench (terrace) for both Lots 7 and 8 is proposed to provide a developable lot area. Lot 7 will also include a retaining wall. B. The variance is the minimum necessary to accommodate the building footprint and access; Response: Apex indicates that the cuts that will result in a 50 percent slope are the minimum to accommodate Lots 7 and 8. C. The proposed variance would preserve the functions and values of the critical area, and/or the proposal does not create or increase a risk to the public health, safety and general welfare, or to public or private property; Response: The proposed cut and benching (terracing) will locally increase the slope to 50 percent immediately adjacent to the boundary of the Lakeland Hills Division No. 8 similar to the condition that already exists upslope of proposed Lot 6 and south of Evergreen Way SE that crosses the northern boundary of the Lakeland Hills Division No. 8. The existing drainage and function of the slope will be preserved. No risk to public health, safety and general welfare or to public or private property is anticipated from the development of Lots 7 and 8. Information Provided by Jeff Parks on 09.30.19 91 of 350 D. The proposed variance would not adversely affect surrounding properties adjoining; Response: No grading is proposed on surrounding property adjoining the project. The planned grading is not anticipated to adversely affect surrounding properties adjoining including Lakeland Hills Division No. 8 upslope of Lots 7 and 8. E. Adverse impacts to critical areas resulting from the proposal are minimized; and Response: The proposed 50 percent slope grading in localized areas with existing slopes greater than 40 percent to develop lot area for Lots 7 and 8 is the minimum grading activity necessary. F. The special circumstances or conditions affecting the property are not a result of the actions of the applicant or previous owner. (Ord. 6442 § 14, 2012; Ord. 5894 § 1, 2005.)" Response: These specific circumstances or conditions affecting the property are not the result of actions of the applicant or previous owner. RESPONSE TO COMMENTS – FEBRUARY 3, 2016 CITY OF AUBURN STORM DIVISION GeoEngineers was asked to respond to specific comments provided by City of Auburn staff on February 3, 2016 and later discussed during a meeting with City staff and the Diamond Valley owner representative Jeff Parks, project team members from Apex Engineering, GeoEngineers and Raedeke on February 23, 2016.Development Review Engineering Division – Community Development & and Public Works Department Comment 3. Benching (terracing) of the graded slopes above developed facilities, i.e., roads, ponds, and homes is required of the proposed facilities. Estimated spacing suggested is at 15- to 20 foot vertical spacing. Please consult with your geotechnical consultant as to their recommended spacing. Your present grading design appears inadequate in respect to benching along the significant 2:1 slopes proposed within the project. It is requested that further discussion and direction be provided by the geotechnical consultant in their report on vertical spacing and recommendations location of benching along the slopes. Specific areas of concern are graded areas above future housing and roadways, and ponds. Response: Additional discussion is provided below in the Recommendations and Conclusions section of the report under Grading Considerations (page 33). Comment 4. Sheet 22 shows fill slopes that are not keyed in. Special attention should be made in the design of fill slopes to prevent failure. Provide design recommendation from the geotechnical consultants on the keying in of fill slopes on this project. Response: Additional recommendations are provided for design of fill slopes in the Recommendations and Conclusions section of the report specifically under Grading Considerations (page 33). Information Provided by Jeff Parks on 09.30.19 92 of 350 Utilities Division - Community Development & and Public Works Department Comment 1. Both ponds exceed requirements to secure a Dam Construction Permit from the Dam Safety Office of the Washington State Department of Ecology. Evidence of permit compliance is required prior to approval of the FAC plans for the project. Response: comment noted. Comment 2. Retaining wall located with the storm ponds shall be concrete meeting the requirements of the Vol III 2.3.1.2 of the 2009i City of Auburn Surface Water Management Manual (SWMM). Response: We provide additional discussion relative to wall design. A concrete wall may significantly increase the excavation depth and dewatering design compared to a soldier pile wall with concrete facing. Comment 3. The geotechnical report provided is a response to the City’s previous comments but does not include a comprehensive geotechnical evaluation of the entire site. The geotechnical report title “Geologic, Hydrogeologic, and Geotechnical Engineering Services, Proposed Kersey III Subdivision, Auburn, Washington” dated March 5, 2004 is considered out of date particularly in the steep hillside areas. The report should be re-issued with revisions to bring in up to date, in accordance with current codes, and include a comprehensive subsurface evaluation of the entire site (full depth boring from top to toe of slopes). The topography, particularly of the steep areas, should be surveyed (e.g. LiDAR or conventional methods), with special emphasis on geologic hillside exposures. Hillsides should be evaluated for areas of seepage, evidence of erosion, and the condition of the tree trunks (e.g. bowed conifer tree trunks). Response: The EIS report for 2004 included the subject project area and a much larger area for development as shown in Appendix C, Figure C-21. We discussed the request for a comprehensive report during our meeting with the City on February 23, 2016. We specifically commented that this document is, in our opinion, a comprehensive report that builds on our EIS report from 2004. The 2016 report includes more recent explorations including 5 test pits and a combined 273 feet of drilling over 5 borings with monitoring wells installed in all, and a 100-ft deep boring (B-9) that extends to a depth near the proximity of the toe Elevation of the project at 303 feet which is near Wetland B. Elements of industry standard sections of geotechnical reports (surface and subsurface conditions) including recommendations specific to the project site are provided in the 2016 report. We provided the entire 2004 report for reference to City staff on March 16, 2016. Updated general geotechnical recommendations that were formerly provided in Appendix E (November 1015) have been incorporated into the General Recommendations and Section on page 33, and respectfully request the City review our 2016 report as the Diamond Valley Estate preliminary geotechnical design site specific report it is intended to be. The site has been conventionally surveyed (DBM Consultants and Apex) and we have also reviewed 2010 LiDAR data as shown in Figure 4. We have provided additional descriptions of the hillslopes relative to seepage, erosion and condition of conifer trunks. Information Provided by Jeff Parks on 09.30.19 93 of 350 Comment 4. A target slope stability for static and seismic safety factor of 1.00 is not acceptable as it burdens the City with long term liability of potential slope failure. Given the perpetual public ownership of the walls and slopes, the notion that “it is highly unlikely that the design earthquake would occur at the same time as the 100-year-high water surface elevation within the pond” is not acceptable. Response: All static slope stability factor of safety values exceed 1.00. Updated seismic slope stability analysis with factor of safety values of at least 1.10 are provided in Appendix D with supporting discussion in the slope stability section of the report below. Comment 5. As noted in the building permit comments, the buffers and setbacks from steep slopes (both at the top and toe of slopes) needs to be defined and shown on the drawings. These setbacks should consider not only the proposed lots within Diamond Valley Estates, but also setbacks from existing lots in the surrounding Lakeland Divisions 8 and 9 and the Pierce County lots to the south. Response: There is discussion provided relative to the approach for grading in steep slopes areas under the section for variances for specific lots in the report that will take slopes to 2H:1V locally in the lots previously noted. Also there is specific design and discussion in the Grading Considerations of the Recommendations and Conclusions section of the report. Comment 6. Provide additional explanation of the slope stability modeling performed, the result of which are shown in Appendix D. Response: Additional discussion is provided below in the slope stability section of the report. Planning Services Division—Community Development & Public Works Department Comment 1. On page 13 (Comment 19) the geotechnical report reference a revised critical areas slope exhibit, but the figure is not contained within the report. Response: The revised figure shows 3 slope classes is included in Appendix E, Figure E-1 (Apex, 2016) that reflect landslide hazards. The 3 slope classes reflect landslide hazard areas as 1 (slopes 0- to 15 percent, shaded green), 2 (slopes 15- to 40 percent, shaded yellow) and 4 (slopes greater than 40 percent, shaded red). As previously reported we observed no landslide hazard 3 surface conditions. Slope areas were developed using conventional survey methods by DBM Consultants that were later updated by Apex in 2013 (Felix Jacobs, Apex, personal communication 2016). SLOPE STABILITY General Movement of a slide mass occurs when the gravitational and seismic forces acting on the soil mass (driving forces) exceed the friction forces (resisting forces) at the base of the slide mass (that is, along the slide Information Provided by Jeff Parks on 09.30.19 94 of 350 surface). Measures to improve slope stability are designed to either increase the resisting forces or reduce the driving forces acting on the slide mass. The resisting forces may be increased by reducing the water pressure at the base of the slide mass (on the slide surface), installing buttressing elements such as retaining walls within or below the slope, or installing reinforcing elements in fill slopes. Driving forces may be reduced by removing soil at the head of the slide mass or by flattening the slope. It is essential to understand that each of these measures can significantly reduce, but not entirely eliminate, the risk of future slide activity. Pond 1 The construction of Pond 1 will include excavation into the adjacent hillside to the southeast and placement of a fill berm with inboard retaining wall along the northwest (downhill) side of the pond. We understand the City requires that the pond be lined. The cut for the uphill side of the pond will be up to 35 feet deep, and will result in finished slopes of 2H:1V extending up to future Road F (Figure 2). Some fill will be placed above the top of the cut to form an embankment that will support the downhill portion of Road F. Two mid-slope terraces with a width of 6 feet each will be provided between the bottom of Pond 1 and Road F. A retaining wall with an exposed height of about 15 feet (relative to bottom of pond level) will be constructed at the toe of the cut slope. A portion of this wall will extend several feet below the bottom of pond level. The wall type has not been selected at this time. The downhill berm for Pond 1 will have a 15-foot-high retaining wall on the inboard (southeast) side and a side slope of 2H:1V on the outboard (northwest) side to avoid filling Wetland A buffers downslope of the pond. A 6-foot crest width will be provided at the top of the berm, and a 15-foot-wide access road will be constructed on the downhill side of the crest. Up to 13 feet of fill will be placed to create the berm. We anticipate that on-site soils such as glacial till will be used to construct the berm. Pond 2 Construction of Pond 2 will include excavation into the adjacent hillside to the west and placement of a fill berm along the east (downhill) side of the pond. We understand the City also requires this pond to be lined. The cut for the uphill side will be up to 35 feet deep, and will result in a finished slope of 2H:1V extending up to future Road B (see Figure 2). A 15-foot-high (relative to pond bottom level) retaining wall will be constructed at the toe of the cut slope. A portion of this wall will extend several feet below bottom of pond level. The wall type has not been selected at this time. A bench with a width of 6 feet will be provided at the top of the wall. Above this bench will be a proposed slope of 2H:1V, residential building lots, and Road B. Some fill will be placed to support the downhill portion of Road B and the residential lots. The downhill berm for Pond 2 will have an inboard slope of 2H:1V and an outboard slope that will typically be at 2.H:1V but will be flatter in places. Up to approximately 18 feet of fill will be placed to construct the berm, which will have a 15-foot-wide access road at the crest and another 15-foot-wide access road near the outboard toe for a portion of the pond. Information Provided by Jeff Parks on 09.30.19 95 of 350 Road F Road F will cross the broad ravine bottom and will also cross an existing steep slope area that is inclined at 40 percent or steeper. A fill embankment about 40 feet in height will support the roadway where it crosses the ravine bottom. Fill slopes for the embankment will be inclined at 2H:1V. Cuts related to lot grading will be made uphill of the roadway within the steep slope area; these cuts will be up to 35 feet in height and will also be inclined at 2H:1V. A portion of the existing steep slope inclined at approximately 2H:1V will remain and extend from a segment of Road F down to near the south end of Pond 1. Lots 7 and 8 Lots 7 and 8 will be located within an identified steep slope area at the west end of a proposed cul-de-sac for Road G. Specific grading plans for these lots have not yet been completed; however we understand that cut slopes inclined at 2H:1V will be used for grading in the western portion of these lots. Slope Stability Analyses Methodology We completed slope stability analyses to evaluate the global static and seismic (pseudo static) stability for the currently planned configurations of Ponds 1 and 2. We also evaluated stability for cut, fill and existing slopes along Road F and Lots 7 and 8. The locations of the cross sections (Cross Sections A1-A1’ through A5-A5’) used in our analyses are shown on Figure 2. We completed the analyses using the computer program Slope/W 2004 developed by GEO-SLOPE International, Ltd. This program has the capability of analyzing slope stability for a wide range of slope and failure surface geometries along with multiple subsurface soil layers. Various groundwater conditions can also be modeled. The program computes the driving forces and resisting forces on a number of randomly generated trial failure surfaces, then computes the factor of safety as the ratio of resisting forces to driving forces. Both static and seismic loading conditions are analyzed. Seismic loading conditions are simulated by applying a horizontal force, expressed as a percentage of g (acceleration due to gravity), to the mass defined by the potential failure surfaces. In our analyses, we evaluated shallow and deep-seated failure surfaces within the cut slopes uphill of the ponds and the slopes of the fill berms that will form the downhill sides of the ponds. We also evaluated shallow and deep seated failures for cut and fill slopes associated with Road F. Using the results for Road F, we also evaluated stability of cut slopes in the vicinity of Lots 7 and 8 based on similarity to conditions along Road F. The slope profile, soil and groundwater conditions used in the stability analyses are generally as described in the Site Conditions section above. The soil layer stratigraphy and groundwater conditions in the model used in our analyses and shown in the analyses results presented in Appendix D represent conservative assumptions, particularly upslope of both ponds. Explorations related to Ponds 1 and 2 were completed in early 2014. We completed additional explorations in fall of 2014 upslope of Pond 1 and along Road F to better define subsurface conditions and to refine our analyses. Soil strength and unit weight parameters used in our analyses were selected based on our experience and judgment and are typical for the geologic units encountered in the Puget Sound region. Information Provided by Jeff Parks on 09.30.19 96 of 350 Minimum Factors of Safety We reviewed typical minimum factor of safety requirements for representative jurisdictions in Washington State, in particular, the Washington State Department of Transportation (WSDOT) and the City of Bellevue. Other jurisdictions may have different minimum factor of safety requirements. The WSDOT Geotechnical Design Manual (2015), Chapter 7, page 7-4 includes a discussion on minimum factors of safety for various constructed features as follows: ■ For slopes adjacent to but not directly supporting structures, a minimum static factor of safety of 1.3 should be used. ■ For foundations on slopes that support structures such as bridges or retaining walls, a minimum static factor of safety of 1.5 should be used. ■ For general slope stability analysis of permanent cuts, fills and landslide repairs, a minimum factor of safety of 1.25 should be used. ■ For slopes involving or adjacent to walls and structure foundations, a minimum seismic factor of safety of 1.1 should be used. ■ For other slopes (cuts, fills and landslide repairs), a minimum seismic factor of safety of 1.05 should be used. The City of Bellevue Land Use Code refers to a document, Sheet 25, Geotechnical Report and Stability Analysis Requirements (2010). This document includes minimum required factors of safety for two classes of permanent slopes: 1) Low Threat Upon Failure, defined as “those slopes whose failure will not impact buildings or other structures inhabited by humans”; and 2) High Threat Upon Failure, defined as “those slopes whose failure will impact or have a reasonable engineering probability of impacting buildings or other structures inhabited by humans”. The required minimum factors of safety for both categories follows: ■ Low Threat Upon Failure: Static, 1.4; Seismic, 1.1. ■ High Threat Upon Failure: Static: 1.5; Seismic, 1.15. Based on our review of the above factor of safety standards and our experience in other jurisdictions, it is our opinion that a minimum static factor of safety of 1.5 is appropriate for slopes involving or adjacent to walls and structures for this project. A minimum factor of safety of 1.3 is appropriate for other slopes in the project site. The factor of safety for seismic loading conditions is highly dependent on the design earthquake and therefore horizontal acceleration used as input for the stability analysis. The following section summarizes consideration of a design horizontal ground acceleration in relation to seismic factor of safety. Horizontal Ground Acceleration We used an input horizontal ground acceleration of 0.255g for the seismic case. As is common practice in the Puget Sound region, this input acceleration is one half of the peak ground acceleration (for this site, 0.51 PGA) determined in accordance with the 2012 International Building Code (IBC) and using the 2008 United States Geological Survey (USGS) probabilistic seismic hazard maps. This peak ground acceleration is associated with an earthquake that has a return period of 2,475 years, or a 2 percent probability of Information Provided by Jeff Parks on 09.30.19 97 of 350 exceedance in a 50-year period. A calculated pseudo static safety factor of 1 or less indicates the potential for slope deformation along the indicated failure surface during the design earthquake. Prior to the 2012 IBC and still currently the case in some jurisdictions, typical horizontal accelerations of 0.15g (or half of the PGA of 0.3 g for this site) were used in the Puget Sound area for seismic stability analyses. This acceleration is generally associated with an earthquake that has a 10 percent probability of exceedance in 50 years, or a return period of about 475 years. The City of Bellevue, for example, still requires this earthquake level be used in its Geotechnical Report and Stability Analysis Requirements. WSDOT typically designs transportation structures for no collapse based on a hazard level of a 7 percent probability of exceedance in 75 years, or a return period of about 1,000 years. As can be seen from the above discussion, the 2012 IBC design earthquake represents a significant increase in the PGA and the corresponding input horizontal acceleration used in stability analyses relative to typical practice for slope evaluations. This higher acceleration level results in a lower calculated factor of safety for a given slope under this relatively less likely (2 percent probability in 50 years) seismic event. Therefore, it is our opinion that an appropriate minimum seismic factor of safety for this project is 1.1 for seismic stability analyses. Ponds 1 and 2 The results of our analyses for the two ponds (Ponds 1 and 2) are summarized below. Selected analyses results are presented in Appendix D and summarized in the following table: TABLE 1. COMPUTED FACTORS OF SAFETY - SLOPE STABILITY ANALYSIS FOR PONDS 1 AND 2 Pond No. Condition Static Seismic (Pseudo static) Pond 1 Uphill – Drained Condition with Wall Embedded 10 feet Below Pond Bottom 1.96 1.10 Downhill - Lower Slope 3.06 1.52 Downhill – Upper Slope 2.41 1.36 Pond 2 Uphill – Drained Condition with Wall Embedded 10 feet Below Bottom of Pond 2.00 1.22 Downhill 3.15 1.42 Information Provided by Jeff Parks on 09.30.19 98 of 350 Pond 1 Uphill Cut Slope We evaluated the finished configuration of the uphill cut slope above Pond 1. This configuration includes a permanent drainage system at the back of the retaining wall that lowers the groundwater level to the elevation of the pond bottom (Elevation 315 feet). The wall is embedded an additional 10 feet below the bottom of the pond, as is typical of a soldier pile shoring system that might be used for this project. Lowering the groundwater level and providing embedment of the wall both act to increase the resisting forces for potential failure surfaces. The wall embedment also causes the potential failure surfaces to extend deeper beneath the surface, which increases the factor of safety. We also assumed that the pond would be empty of surface water, which would result in a lower factor of safety than if water were present in the pond, since the weight of the water retained in the lined pond would contribute to the resisting force. The resulting static factor of safety for this configuration is 1.96 (see Figure D-1 in Appendix D). The resulting pseudo static factor of safety using a horizontal ground acceleration of 0.255g is 1.10 (Figure D-2 in Appendix D). For comparison, the pseudo static factor of safety is 1.35 for horizontal ground acceleration of 0.15g which corresponds to an earthquake with a 475 year return period. The short term risk of sliding is higher if the groundwater level is not lowered during pond excavation. This would occur when encountering heaving sand under high ground water pressure. Accordingly, we recommend that dewatering of the hillside be implemented prior to starting excavation for the pond. Downhill Fill Berm We evaluated the finished configuration of the downhill fill berm for Pond 1, assuming that the pond will be lined and that no seepage will occur through the berm. The configuration includes 2H:1V side slopes and a 15-foot wide access road at about mid-height on the downhill berm face. Also included are zones of geotextile reinforced fill layers on both the upper slope (that is, above the access road) and the slope below the access road (lower slope). The reinforced zone extends for a horizontal distance of 10 feet inward from the slope face and increases the resisting force and also mitigates against shallow slope failures. The resulting static factor of safety for the reinforced lower slope is 3.06 (Figure D-3 in Appendix D). The resulting pseudo static factor of safety using a horizontal ground acceleration of 0.255g is 1.52 (Figure D-4 in Appendix D). For the upper slope the respective factors of safety are 2.41 (static) and 1.36 (seismic) (Figures D-5 and D-6, Appendix D.) Pond 2 Uphill Cut Slope The finished configuration used in our analysis for the uphill cut slope for Pond 2 is similar to Pond 1 and includes a permanent drainage system at the back of the retaining wall that lowers the groundwater level to the elevation of the pond bottom (Elevation 285 feet). The wall is embedded an additional 10 feet below the bottom of the pond as is typical of a soldier pile shoring system that might be used for this project. Lowering the groundwater level and providing embedment of the wall both act to increase the resisting forces for potential failure surfaces. The wall embedment also causes the potential failure surfaces to extend deeper beneath the surface, which increases the factor of safety. Information Provided by Jeff Parks on 09.30.19 99 of 350 We also assumed that the pond would be empty of surface water, which would result in a lower factor of safety than if water were present in the pond, since the weight of the water retained in the lined pond would contribute to the resisting force. The resulting static factor of safety for this configuration is 2.00 (Figure D-7 in Appendix D). The resulting pseudo static factor of safety using a horizontal ground acceleration of 0.255g is 1.22 (Figure D-8 in Appendix D). Downhill Fill Berm The downhill fill berm for Pond 2 will be inclined at a flatter slope than the berm for Pond 1. Also, the pond will be lined and therefore no seepage will occur through the berm. The resulting static factor of safety was computed as 3.15 and the factor of safety under seismic loading conditions was computed as 1.42 (Figures D-9 and D-10, Appendix D). Road F The results of our analyses for existing slopes and finished cut and fill slopes associated with Road F are summarized below. Selected analyses results are presented in Appendix D and summarized in the following table: TABLE 2. COMPUTED FACTORS OF SAFETY - SLOPE STABILITY ANALYSIS FOR ROAD F Section Condition Static Seismic (Pseudo static) Road F Fill embankment slope across ravine (Section A3-A3’) 1.88 1.15 Cut slope above road (Section A4-A4’) 1.84 1.15 Cut slope above road (Section A5-A5’) 1.91 1.10 Existing 2H:1V slope below road 2.11 1.26 Fill Embankment across Ravine Bottom We assumed a groundwater level at the base of the embankment and following the slope of the base. We also included a zone of geosynthetic reinforced fill extending 10 horizontal feet inward from the slope face to mitigate against shallow failures. The resulting static factor of safety is 1.88 and the factor of safety under seismic loading conditions is 1.15 (Figures D-11 and D-12, Appendix D) Uphill Cut Slopes These cut slopes will primarily expose ice contact deposits consisting of silty sand with gravel and cobbles. Under the large earthquake loading, these slopes will be somewhat susceptible to shallow surficial sloughing. Accordingly, we have evaluated a finished configuration that includes a reinforced fill slope with a vertical height of 10 feet and with the reinforcing zone extending inward from the slope face over a horizontal distance of 10 feet. This section also includes a backslope above the reinforced zone inclined at 2.2H:1V as an additional mitigation against shallow slides. Static factors of safety for cut slopes along two sections (A4-A4’ and A5-A5’) above Road F were computed at 1.84 and 1.91, respectively (Figures D-13 and D-15, Appendix D). Information Provided by Jeff Parks on 09.30.19 100 of 350 The seismic factors of safety are 1.12 and 1.10, respectively (Figures D-14 and D-16, Appendix D). Downhill Existing Slopes The computed static factor of safety for the existing slope (as represented in Section A5-A5’) modified slightly at the top by a low fill embankment to support Road F is 2.11. For seismic conditions, the computed factor of safety is 1.26 (Figures D-17 and D-18, Appendix D). Lots 7 and 8 The subsurface conditions and anticipated finished slopes for Lots 7 and 8 and vicinity are similar to the cut slopes associated with Road F. Therefore, the factors of safety and possible mitigation measures for slope stability should be similar. We note that existing cut slopes associated with nearby Evergreen Way are performing satisfactorily for static conditions. DOWNSTREAM DRAINAGE EVALUATION Dispersion Trenches The conceptual stormwater design for the Diamond Valley Estates development divides the project site into two sub-basins. Stormwater detention ponds were designed to receive built infrastructure runoff from each of the two sub-basins. Pond discharge is through dispersion trenches located between the ponds and existing site wetlands. Pond 1 will discharge to Wetland A through a single trench. Pond 2 will discharge via two trenches to Wetland B and one trench to Wetland C. The general stormwater pond layout, dispersion trench locations, and wetlands are shown in Figure 2. The maximum flow velocities for water exiting the dispersion trenches and flowing overland to the wetland (100-year flow event; Felix Jacobs, personal communication, 2014) are shown in Figure 2. All of the dispersion trenches are situated within the wetland buffers except for location 2 at the south end of Wetland B which is outside the buffer. The dispersion trench design included in the City Surface Water Management Manual (Figure VI-2-2.) specifies that receiving slopes not exceed 15 percent gradient in order to provide adequate flow control and water quality treatment. It is our understanding that the Diamond Valley Estates stormwater system design will comply with the design criteria in terms of slopes downstream of the dispersion trenches and that disturbance to native vegetation will be minimized in the areas between the trenches and the wetland receiving areas. Existing slopes in the dispersion trench overland flow areas do not exceed 15 percent (Felix Jacobs, personal communication, December 16, 2014). Field observations at the four dispersion trenches are described below. Location 1: Pond 1, Wetland A The Pond 1 dispersion trench location is densely vegetated with salmonberry, mature alder trees approximately 10 to 25 feet on center, and sword fern. The ground surface is covered with 2 to 4 inches of leaf litter and forest duff. The soil consists of silty sand with fine to coarse gravel, loose to medium dense, becoming dense to very dense at 12 to 24 inches bgs. The existing ground slope in the area was estimated to be inclined to approximately 6 percent in the field and our review of a site topographic map indicates the slope may reach 15 percent at the northeast end of the trench. The estimated maximum overland flow velocity at this location is 0.6 feet per second and the proposed trench is approximately 280 feet long. Information Provided by Jeff Parks on 09.30.19 101 of 350 Location 2: Pond 2, Wetland B, South End The southernmost Pond 2 trench is located in a moderately to densely vegetated area with salmonberry, sparse alder and maple trees. The ground surface is also covered with several inches of forest duff and the soil consists of silty sand to sand silt with occasional gravel, medium dense to dense to a depth of approximately 24 inches, and then becoming very dense. Slopes were estimated in the field to be inclined to approximately 10 percent as the trench area is located in a natural drainage swale at the head of Wetland B. The proposed dispersion trench is short, approximately 50 feet, and the estimated maximum overland flow velocity is 0.64 feet per second. Location 3: Pond 2, Wetland B, West Side On the west side of Wetland B, a constructed wetland is proposed in the buffer as mitigation. The current area is vegetated with reed canary grass and Himalayan blackberry while closer to the wetland the vegetation is dense native salmonberry and alder. Soils beneath the reed canary grass root zone consist of dense, cohesive sandy silt with gravel, becoming very dense at 1 to 2 feet bgs. The existing ground slope in this area is flat to moderate (inclined to approximately 10 percent) and sloping toward the wetland. The proposed dispersion trench at this location is approximately 100 feet long with a maximum overland flow velocity of 0.57 feet per second. Location 4: Pond 2, Wetland C The dispersion trench location into Wetland C is currently covered with dense growth of Himalayan blackberry and clumps of immature alder dispersed on approximately 20- to 50-foot centers. A thin duff layer is present beneath the blackberry. The subsurface soil consists of medium dense, gravelly, silty sand becoming very dense at approximately 2 feet bgs. The existing ground slope in the area is gentle to moderate (inclined to approximately 7 to 15 percent). The proposed dispersion trench has an arcuate shape around the head of the wetland, is approximately 160 feet long, and will have a maximum overland flow velocity of 0.37 feet per second. Tributary 0043 In order to evaluate the stream channel capacity, we utilized the United States Geological Survey (USGS) program StreamStats to estimate the drainage area and discharge at the location where Tributary 0043 leaves the Diamond Valley property, through the culvert beneath the sewer easement road (USGS StreamStats 2014). StreamStats estimates that the watershed has a drainage area of 0.32 square miles (approximately 205 acres) and includes all of the Diamond Valley Estates property plus a large portion of the Lakeland Hills Estates property located to the east, and extends south across the King-Pierce County line to approximately 64th Street East. The estimated 2-year peak streamflow is 10.3 cubic feet per second (cfs) and the 100-year estimated flow is 30.9 cfs. Tributary 0043 is an unclassified stream by King County and has been identified as having intermittent (seasonal) flow. A review of the 2010 LiDAR high-resolution topography for the site was conducted to identify areas of active erosion and deposition. The LiDAR image for Tributary 0043 is shown in Figure 4. A profile of the stream from the drainage head to the confluence with Bowman Creek is presented in Figure 5. GeoEngineers also conducted a reconnaissance of portions of the unnamed Tributary 0043 on November 17, 2014 to evaluate current conditions with respect to channel composition, current erosion Information Provided by Jeff Parks on 09.30.19 102 of 350 and capacity. Field observations are described below. At the time of our site visit, less than 0.5 cfs was estimated to be flowing in the stream at all on-site locations. Upstream of the Sewer Easement Culvert This stream channel site is located upstream from a 24-inch-diameter corrugated metal pipe (CMP) culvert that conveys the stream beneath a light utility road for a sewer easement at the northeast property boundary (see Figure 2). The road fill embankment is approximately 20 feet thick on the upstream side of the culvert. This stream channel has a meandering planform over an approximate 3 to 5 percent gradient. The channel flows through an approximately 100-foot-wide, v-shaped alluvial valley with 50- to 75-foot-high side slopes. The bankfull channel is approximately 4 feet wide by 2 feet deep and the channel floor is approximately 2 feet wide. The water depth at the time of our reconnaissance was approximately 3 inches and appeared to be at low to moderate flow. A cross section measured at this location is shown in Figure 3. The bankfull channel area calculated from the measured cross section is 3.1 square feet. The channel capacity for a water elevation at the top of the culvert pipe inlet is 11.0 square feet. The channel character and dimensions at this location appear to be representative of the reach immediately upstream for approximately 100 feet. The bed surface and substrate are composed of fine to medium sand with fine gravel. The channel is generally full of organic leaf litter and fine sand. The bed is relatively dense, with refusal depths (determined using a ½-inch-diameter steel probe rod) ranging from less than 1 inch to a maximum depth to refusal of 1 foot. A pebble count yielded a median particle size (D50) of 0.4 inches, D84 of 1.1 inch and D100 of 4.2 inches (see Appendix F for pebble count size distribution chart). Small woody debris (1- to 2-inch-diameter branches) densely cover the channel. Banks are composed of thick forest duff over organic sandy soil with gravel. Bank angles above the valley have a moderate slope inclined to approximately 30 percent. The floodplain and banks are vegetated with salmonberry, alder, sword fern and vine maple but also have a dense cover of felled trees and anthropogenic refuse. Refusal depths on the bank and valley slopes are from 2 to greater than 3 feet. Downstream from Culvert This stream channel site is located immediately downstream of the sewer easement road approximately 15 feet downstream of the outlet of the 24-inch CMP culvert (see Figure 2). The culvert is approximately 75 to 100 feet long and the gradient of the culvert appears to be approximately 5 percent. The road fill embankment is approximately 45 feet thick on the downstream side of the culvert. The invert of culvert pipe at the outlet is approximately 12 inches below grade and up to 18 inches of silt and sand have accumulated at the culvert outlet. The channel meanders in planform. A debris jam composed of tires and broken concrete immediately downstream from the culvert outlet traps sediment and forms a short section of small (less than 1-foot-high) steps and shallow pools. The bankfull channel is approximately 5 feet wide by 2 feet deep and the channel floor is approximately 3.5 feet wide. Water depth was approximately 2 inches at the time of our November reconnaissance. The channel bed and banks are better developed at this location than at the upstream culvert location. A cross section measured at this location is shown in Figure 3. The bankfull channel area calculated from the measured cross section is 9.4 square feet. The channel downstream of this location was not explored because downed trees and dense vegetation blocked access. Information Provided by Jeff Parks on 09.30.19 103 of 350 The channel floor is armored with fine to coarse gravel and cobbles, interspersed with fine sand and silt. The D50 was visually estimated to be approximately 1.7 inches and the D84 approximately 2.5 inches, slightly coarser overall than upstream of the culvert. Probe rod refusal depths varied from less than 1 inch to less than 1 foot but was generally approximately 3 inches. Bank surfaces are covered with organic debris, duff and refuse. Bank soils are a cohesive mixture of sand, silt and gravel. The riparian vegetation is composed of blackberry, salmonberry, sword fern and alder. Vegetation on the upper slopes, beginning approximately 10 feet above the stream channel is very dense. Fallen trees blocked the channel approximately 20 feet downstream of the cross section location. A significant volume of the left bank side slope is comprised of disposed automobile tires with some broken concrete. The valley is approximately 50 to 100 feet wide at the top with 30- to 50-foot-high side slopes. Kersey Road Crossing Approximately 1,300 feet downstream of the property boundary, the stream channel approaches an 18-inch-diameter concrete culvert crossing beneath Kersey Road. The channel gradient is approximately 1 to 3 percent at the culvert inlet. The road fill embankment is approximately 8 feet high on the upstream side. The stream channel upstream of the culvert is approximately 3 feet wide with 0.3 to 0.4 feet high banks. The water depth observed at the time of our reconnaissance was 0.3 feet. The channel approaches the culvert at a nearly 80 percent angle and has to make a sharp bend to enter the culvert. Some moderate bank erosion was observed on the right side of the culvert. Upstream of the culvert, the valley is broad and open, with gentle to moderate slopes extending uphill from the stream channel. The channel planform is straight to slightly sinuous and has a riffle bed morphology. Upstream of the culvert crossing, the stream has developed a floodplain, up to 100 feet wide. The bed surface and substrate and bank composition are similar to those observed at the upstream sites. Fine sediment (fine sand and silt) is accumulating on the upstream side of the culvert. Access to the downstream side of the culvert is currently restricted by fencing and dense blackberry growth and was observed from the roadway. The culvert apparently dissipates through a gabion basket wall (Apex, 2014). Water was observed flowing up out of a 4-foot-diameter catch basin covered with a raised grate (an energy dissipator) and into a stream channel densely covered by blackberry and reed canary grass. The confluence of Tributary 0043 with Bowman Creek was not observed. Stream A Reconnaissance Stream A, the headwaters of Tributary 0043, discharges from an emergent forested wetland near the eastern property boundary (see Figure 2). The stream channel includes a drainage swale that traverses the property from south to north-northeast through the eastern central portion of the site. The stream channel upstream of Wetland A was not observed during the November site reconnaissance. Through the wetland, the stream channel is poorly to moderately defined. Downstream of the wetland, the stream is gently sinuous, the channel bottom is approximately 1 to 2 feet wide and the gradient ranges between approximately 1 and 3 percent. The bed is composed of cobble and gravel with sand. Refusal depths are between 12 and 18 inches. The valley or wetland width immediately adjacent the stream ranges from approximately 15 to 25 feet and slopes very gently away from the stream. The riparian and slope vegetation primarily consists of salmonberry, sword fern, cottonwood, and alder. Information Provided by Jeff Parks on 09.30.19 104 of 350 Stream A crosses the eastern property boundary and bends approximately 70 degrees to flow north-northwest. Observations of this area on LiDAR indicate that the gradient steepens sharply to approximately 13 percent as the stream flows over a natural slope break and the stream has become entrenched in an eroded gulley. This area was observed remotely from the east side of Tributary 0043 because a large cluster of recently fallen cottonwood trees blocked access to this area. The entrenched stream area is densely vegetated and the stream channel was not visible. Stream B Reconnaissance Stream B discharges from Wetland B near the eastern site boundary approximately 215 feet south of the north property line. It flows northeast approximately 190 feet to a confluence with Tributary 0043 immediately east of the eastern property line. The channel becomes well defined as it leaves the wetland and traverses the natural slope break at the east edge of the property. The stream gradient is approximately 20 percent over this slope break and the channel has cut a steep-walled gully into the hillside. The highest banks are 4 to 6 feet through the entrenched area and approximately 10 feet wide at the top. The channel floor is approximately 2 feet wide. A very small stream discharge was observed during the November reconnaissance. Bed and bank materials consist of moderately dense to dense silty sand with gravel and cobbles. Abundant organic debris has accumulated in the channel bottom. Riparian vegetation consists of sword fern, salmonberry, cottonwood, and alder with sparse fir trees present on the side slopes. Although some bare soils were present on the steep stream banks, the channel did not have active signs of significant, recent erosion. DOWNSTREAM CAPACITY AND ERODIBILITY EVALUATION The downstream capacity and erodibility of the Tributary 0043 stream channel where it exits the property were evaluated based on the field measured cross sections and reconnaissance observations. Two previous studies evaluated the downstream drainage for prior project proposals and concluded that no erosion was occurring with the exception of the Kersey Way culvert outlet (DBM Consulting, 2004; Apex, 2014). The Kersey Way culvert appears to have been repaired and erosion observed in the past is apparently no longer occurring. The stream channel capacity was calculated by multiplying the measured cross sections by a series of possible stream flow velocities. The 2-year flow estimated by StreamStats for the drainage basin is 10.3 cfs and the 100 year flow is 30.9 cfs. Stream flow volumes have not been estimated for this location and would require hydraulic modeling to do so. Table 3 shows calculated stream flow volumes for the stream channel upstream and downstream of the sewer easement road culvert and for the culvert pipe. Information Provided by Jeff Parks on 09.30.19 105 of 350 TABLE 3. FLOW VOLUME CHANNEL CAPACITY AT SEWER EASEMENT CULVERT, UPSTREAM AND DOWNSTREAM BASED ON FIELD MEASURED CROSS SECTIONAL AREA. Velocity (ft./s) Upstream Channel Capacity (11 ft2 area) (cfs) Downstream Channel Capacity (9.4 ft2 area) (cfs) Culvert (2.16 SF) (cfs) 1 11 9.4 2.16 2 22 18.8 4.32 3 33 28.2 6.48 4 44 37.6 8.64 5 55 47 10.8 6 66 56.4 12.96 7 77 65.8 15.12 8 88 75.2 17.28 9 99 84.6 19.44 10 110 94 21.6 Many factors affect stream flow velocity including stream slope (gradient; see Figure 5), channel roughness, sediment grain size, and total sediment load. Based on our review of the available data and stream reconnaissance, the stream gradient is moderate (approximately 5 percent) in the vicinity of the project site and immediately downstream. The channel roughness is fairly high from the abundant debris (organic and anthropogenic) and bank vegetation, which will slow flow velocity. The sediment load and grain size both appear to be relatively small, indicating generally low stream power and velocities. The measured average grain size within the existing channel is fine gravel (D50 = 0.4 inches) and the maximum size observed was a 4.2-inch-diameter cobble. If significant channel erosion were occurring, gravel, cobbles and boulders that are present in source material would be observed in the stream bed. Large sediment source areas such as landslides and slumps, steep banks with bare slopes, or gravel bars in the valley bottom were not identified either in the desktop analysis or field reconnaissance. The primary area of potential erosion identified is the location at the east end of the property where Stream A (Tributary 0043) and Stream B flow over the natural break in slope and the gradient sharply steepens. Significant signs of recent, active erosion were not observed at these areas. As shown in Table 3, flow volumes that exceed the upstream channel capacity will result in ponding because downstream flow is constrained by the culvert. Ponding can also occur if the culvert becomes blocked by debris and/or sediment. Downstream flow volumes that exceed the channel capacity may result in some erosion and channel widening immediately downstream of the culvert where the channel is small and constrained in a narrow valley. Approximately 200 feet downstream of the culvert outlet, another tributary channel enters from the left and the valley bottom becomes much broader, indicating a large increase in channel and/or floodplain capacity. Based on the measured cross sections and the estimated 2-year and 100-year flows, and the fact that the proposed stormwater system must be designed such that discharge volumes will not increase, it appears that sufficient channel capacity in stream Tributary 0043 exists to manage the expected flows. Information Provided by Jeff Parks on 09.30.19 106 of 350 Our evaluation considers that other residential developments in the vicinity, including the Lakeland Hills Estates, have stormwater systems in place that meet City standards and will not increase flow volumes to the stream. In addition to stormwater detention in the designed ponds for the project, dispersion discharge and overland flow to the site wetlands should provide additional buffering capacity for stormwater runoff as opposed to a design that would discharge directly into a stream channel. Site soils and subsoils consist of dense to very dense glacial materials that are generally erosion resistant. However, if conditions change, some additional channel incision could occur at the break in slope on Streams A and B. Over time, the incision would progress upstream (headcutting) and may impact the lower portions of Wetlands B and 2. This headcutting is a natural process under the existing conditions but could be accelerated by increased flow velocity and/or volume. The culvert itself has the smallest flow capacity and limits the overall channel capacity to convey stream flow. The 2.16 square foot capacity of the 24-inch-diameter culvert is sufficient to pass the predicted 2-year flow volume (10 cfs) at a velocity of 5 feet per second (ft/s). The culvert capacity appears to be limited and would require a flow velocity of 14 ft/s to pass the 100-year flow volume of 30 cfs. These velocities are relatively high compared to the expected channel velocities (see Table 3). Sediment accumulated at the downstream end of the culvert has buried about half of the outlet, indicating that water is currently ponding at the outlet and causing sediment deposition. Debris jams present in the downstream channel are likely responsible for this condition. Dispersion Trenches Under existing conditions, the flow velocities expected from the maximum discharge of the dispersion trenches would not be expected to cause erosion because overland flow would be slowed by the surface material, vegetation and root mass. However, construction of the stormwater ponds and dispersion trenches that will disturb the vegetation and expose bare soils would result in rilling and gullying of the surface soils by sheet flow from the trenches if left in a disturbed condition. The upper 12 to 24 inches, approximately, are rated as having slight erosion hazard even on slopes less than 8 percent, and increases to moderate erosion hazard at slopes over 15 percent. DISCUSSION AND CONCLUSIONS Based on the results of our stream evaluation, as well as our subsurface explorations and our geotechnical engineering evaluations, it is our opinion that the planned Diamond Valley Estates project may be developed generally as envisioned. We provide general recommendation for residential construction in the section below. These general recommendation do not apply to certain areas where specific, more detailed recommendations are provided such as the mitigation measures to improve stability and performance of the ponds, Road F and Lots 7 and 8 cut slopes and berms under seismic conditions. Static and seismic factors of safety with the mitigating measures described meet or exceed commonly accepted minimum values. We note that the relatively low seismic factors of safety are significantly lower than would be calculated for lower intensity design level earthquakes that are used by other jurisdictions in the region when considering seismic slope hazard. The primary geotechnical considerations for the project are summarized below. inal design will further refine site specific geotechnical recommendations. Information Provided by Jeff Parks on 09.30.19 107 of 350 General Recommendations GeoEngineers presents preliminary geotechnical recommendations herein for the proposed Diamond Valley Estates development in Auburn, Washington. At the time our geotechnical services were provided, the design was in a preliminary plat stage; so our recommendations are not final and should be expected to evolve as the project elements become better defined. Additional explorations and analyses may be required in support of final design. Based on the conceptual layout, our literature review, explorations and evaluation, we conclude that development of the site can generally be accomplished as proposed and that shallow foundation support will be suitable for the planned residences. A summary of primary geotechnical considerations for the site development is provided below. The summary is presented for introductory purposes only and should be used in conjunction with the complete recommendations presented in this report. The proposed buildings may be supported on shallow spread foundations bearing on (1) undisturbed dense to very dense glacial deposits (ice contact, till or advance outwash), or (2) properly compacted structural fill extending down to the dense or very dense glacial deposits. We recommend an allowable soil bearing pressure of 2,000 pounds per square foot (psf) for design of spread footings on the undisturbed dense glacial deposits or on properly placed and compacted structural fill overlying the dense glacial soils. On-grade slabs for the houses should be underlain by a capillary break layer consisting of at least a 4 inch thickness of gravel overlain by a vapor retarder consisting of plastic sheeting. Site soils that will be encountered during construction and may be considered for use as structural fill include the medium dense to very dense glacial deposits. The ice contact and till soils contain a high percentage of fines and will be sensitive to changes in moisture content and difficult to handle and compact during wet weather. We expect that operation of equipment on these soils will not be difficult when the soils are at their natural moisture content. However, site preparation and earthwork should be completed during the drier summer months to avoid the increased cost of importing fill if the on-site soils become wet and unsuitable for use as structural fill. The very dense glacial deposits may be very difficult to excavate in the planned deeper cuts and large excavators and/or dozers equipped with rippers may be needed. We anticipate that shallow groundwater may be present as perched layers within the glacial deposits during the wet winter and spring months. We do not expect that groundwater other than perched or trapped groundwater will be encountered during excavation for shallow utilities and residences. Groundwater could be encountered at the contact between the fill soils and native glacial soils. We expect that seepage water can typically be handled by digging interceptor trenches in the excavations and pumping from sumps. ■ Separate dewatering design will be prepared for Ponds 1 and 2 as part of final design. ■ Cobbles and boulders were encountered in our explorations, and the contractor should be prepared to deal with them when encountered. ■ Effective erosion and sedimentation controls must be implemented during construction so that potential impacts to the adjacent areas can be avoided. The erosion potential of the on-site soils ranges from low to high. The erosion and sedimentation control measures used for this project should be in accordance with the requirements of the City of Auburn. Information Provided by Jeff Parks on 09.30.19 108 of 350 Earthwork Based on the subsurface soil conditions encountered in the explorations, we expect that the soils at the site may be excavated using conventional construction equipment. Very dense glacial deposits in the deeper cuts may require a large, heavy-duty excavator or dozer with rippers to accomplish the excavations. Glacial deposits on site commonly contain cobbles and boulders that will be encountered during excavation. Accordingly, the contractor should be prepared to deal with cobbles and boulders. The till and ice contact soils contain enough fines (material passing the U.S. standard No. 200 sieve) to be highly moisture-sensitive and susceptible to disturbance, especially when wet. Ideally, earthwork should be undertaken during extended periods of dry weather when the subgrade soils will be less susceptible to disturbance and provide better support for construction equipment. Dry weather construction will help reduce earthwork costs and increase the potential for using the native soils as structural fill. Trafficability on the site is not expected to be difficult during dry weather conditions. However, the native soils will be susceptible to disturbance from construction equipment during wet weather conditions and pumping and rutting of the exposed soils under equipment loads is likely when subgrades are wet. We recommend that a representative from our firm be present during proofrolling and/or probing of the exposed subgrade soils in building and pavement areas and during placement of structural fill as described below. Our representative will evaluate the adequacy of the subgrade soils and existing fill soils, identify areas needing further work; perform in-place moisture-density tests in the fill to determine if the compaction specifications are being met, and provide advice on any procedural modifications that may be appropriate for the prevailing conditions. Clearing and Site Preparation Areas to be developed or graded should be cleared of surface and subsurface deleterious matter including any debris, underbrush, trees and associated stumps and roots. Graded areas should be stripped of organic soils. Based on our explorations and site observations, we estimate that stripping depths at the site will generally be on the order of 12 inches to remove the topsoil and organic soils. Deeper excavations may be needed to remove root balls associated with large trees. The organic strippings can be stockpiled and processed for landscaping purposes to revegetate disturbed areas following completion of grading. If spread out to revegetate disturbed areas, the organic strippings should be placed in a layer less than 1-foot-thick, should not be placed on slopes greater than 3H:1V (horizontal to vertical) and should be track-walked to a uniformly compacted condition. Materials that cannot be used for landscaping or revegetation of disturbed areas should be removed from the project site. We recommend that any unsuitable soil or fill encountered in the proposed building areas and within two feet of pavement subgrades be removed and replaced with properly compacted structural fill. Excavations to remove any unsuitable soil or fill should extend horizontally beyond the building perimeters and edges of pavement for a distance equal to the excavation depths. Subgrade Preparation Prior to placing new fills, pavement base course materials or capillary break materials below on-grade floor slabs, all subgrade areas should be evaluated by proofrolling to locate any soft or pumping soils. Proofrolling can be completed using a piece of heavy, tire-mounted equipment such as a loaded dump truck. During Information Provided by Jeff Parks on 09.30.19 109 of 350 wet weather, the exposed subgrade areas should be probed to evaluate the presence and determine the extent of soft soils. If soft or pumping soils are observed they should be removed and replaced with structural fill. If deep pockets of soft or pumping soils are encountered in areas to be developed outside the building areas, it may be possible to limit the depth of overexcavation by placing a woven geotextile fabric such as Mirafi 600X (or approved equivalent) on the overexcavated subgrade prior to placing structural fill. The geotextile will provide additional support by bridging over the soft material and will help reduce fines contamination into the structural fill. We anticipate that no more than 2 feet of structural fill placed over a geotextile fabric will be needed to support pavement areas over soft subgrade conditions at this site. After completing the proofrolling, the subgrade areas should be recompacted to a firm and unyielding condition, if possible. The degree of compaction that can be achieved will depend on when the construction is performed. If the work is performed during dry weather conditions, we recommend that all subgrade areas be recompacted to at least 95 percent of the maximum dry density (MDD) in accordance with the American Society for Testing and Materials (ASTM) D 1557 test procedure. If the work is performed during wet weather conditions, it may not be possible to recompact the subgrade to 95 percent of MDD (ASTM D 1557). In this case, we recommend that the subgrade be compacted to the extent possible without causing undue weaving or pumping of the subgrade soils. Subgrade disturbance or deterioration could occur if the subgrade is wet and cannot be dried. If the subgrade deteriorates during proofrolling or compaction, it may become necessary to modify the proofrolling or compaction criteria or methods. Structural Fill All fill, whether existing on-site soil or imported soil, that will support floor slabs, pavement areas or foundations, or will be used for fill slopes, or placed against retaining walls or in utility trenches should generally meet the criteria for structural fill presented below. The suitability of soil for use as structural fill depends on its gradation and moisture content. The existing dense glacial soils encountered in some of the explorations are expected to be suitable for structural fill in areas requiring compaction to at least 95 percent of MDD, as determined by the ASTM D 1557 test method, provided the work is accomplished during the normally dry season (July through September) and that the soil can be properly moisture conditioned. However, for wet weather construction, we believe that it may be necessary to import sand and gravel with a low fines content to achieve adequate compaction for support of pavement areas, floor slabs and structures. Alternatively, admixtures, such as cement or lime, could be used to improve the workability of the native fine-grained soils to permit use as structural fill during wet weather conditions. We recommend imported structural fill consist of either crushed gravel or well graded sand and gravel containing less than 5 percent fines (materials passing U.S. Standard No. 200 sieve) by weight relative to the fraction of the material passing the ¾ inch sieve. This imported fill material should be free of rock fragments larger than 4 inches, debris and organic material. We recommend that the suitability of structural fill material from proposed borrow sources be evaluated by the geotechnical engineer before the earthwork contractor is allowed to transport any material to the site. Structural fill should be mechanically compacted to a firm, non-yielding condition. Structural fill placed in building areas to support footings and floor slabs should be compacted to at least 95 percent of MDD Information Provided by Jeff Parks on 09.30.19 110 of 350 (ASTM D 1557). Pavement area fill, including utility trench backfill, should be compacted to at least 90 percent of MDD, except for the upper 2 feet below finished subgrade surface, which should be compacted to at least 95 percent of MDD. Structural fill to support walkways should be placed after the subgrade is evaluated and be compacted to at least 90 percent of MDD. Structural fill used to construct fill slopes should be compacted to at least 90 percent of MDD. Structural fill that is compacted by heavy equipment should be placed in loose lifts generally not exceeding 10 inches in thickness. Each lift should be conditioned to the proper moisture content and compacted to the specified density before subsequent lifts are placed. We recommend that fill placed against below grade walls and retaining walls be compacted to between 90 and 92 percent MDD, using hand operated compaction equipment within 5 feet of the wall. Overcompaction should be avoided to prevent the buildup of excessive lateral pressures on the wall. Temporary Cut Slopes Temporary cut slopes may be required for rough grading, construction of retaining structures, basement excavations, or to install utilities. The stability of open cut slopes is a function of soil type, groundwater seepage, slope inclination, slope height and nearby surface loads. The use of inadequately designed open cuts could impact the stability of adjacent work areas, existing utilities, and endanger personnel. In our opinion, the contractor will be in the best position to observe subsurface conditions continuously throughout the construction process and to respond to variable soil and groundwater conditions. Therefore, the contractor should have the primary responsibility for deciding whether or not to use open cut slopes rather than some form of temporary excavation support, and for establishing the safe inclination of the cut slope. Acceptable slope inclinations should be determined during construction. All open cut slopes and temporary excavation support should be constructed or installed, and maintained in accordance with the requirements of the appropriate governmental agency. For planning purposes, temporary unsupported cut slopes more than 4 feet high may be inclined at 1-1/2H:1V maximum steepness within the surficial soils, medium dense glacial deposits, and within properly compacted structural fill. Cut slopes can be steepened to 0.75H:1V within the dense to very dense glacial deposits if groundwater seepage is not present and as approved by the geotechnical engineer. If seepage is present on the cut face of the dense to very dense glacial deposits then the cut slope should be inclined no steeper than 1H:1V. We recommend that a representative from our firm observe the cuts in the glacial deposits to assess stability prior to making final temporary cuts. The above guidelines assume that surface loads such as equipment loads and stockpile loads will be kept a sufficient distance away from the top of the cut so that the stability of the excavation is not affected. We recommend that this distance be not less than half the height of the cut. Some sloughing and raveling of the cut slopes should be expected. Temporary covering, such as heavy plastic sheeting with appropriate ballast, should be used to protect these slopes during periods of wet weather. Surface water runoff from above cut slopes should be prevented from flowing over the slope face by using berms, drainage ditches, swales or other appropriate methods. Information Provided by Jeff Parks on 09.30.19 111 of 350 If temporary cut slopes experience excessive sloughing or raveling during construction, it may become necessary to modify the cut slopes to maintain safe working conditions. Slopes experiencing problems can be flattened, regraded to add intermediate slope benches, or additional dewatering can be provided if the poor slope performance is related to groundwater seepage. Permanent Cut and Fill Slopes We recommend that permanent cut or fill slopes be constructed at inclinations of 2H:1V or flatter, and be blended into existing slopes with smooth transitions. To achieve uniform compaction, we recommend that fill slopes be overbuilt slightly and subsequently cut back to expose well compacted fill. To reduce the risk of erosion, newly constructed slopes should be planted or hydroseeded shortly after completion of grading. Until the vegetation is established, some sloughing and raveling of the slopes should be expected. This may necessitate localized repairs and reseeding. Temporary covering, such as clear heavy plastic sheeting, jute fabric, loose straw or excelsior matting could be used to protect the slopes during periods of rainfall. Utility Trenches Trench excavation, pipe bedding, and trench backfilling should be completed using the general procedures described in the 2016 Washington State Department of Transportation (WSDOT) Standard Specifications or other suitable procedures specified by the project civil engineer. Utility trench backfill should consist of structural fill and should be placed in lifts of 10 inches or less (loose thickness) such that adequate compaction can be achieved throughout the lift. Sand backfill, containing less than 5 percent fines, may be compacted in loose lifts not exceeding 12 inches when placed below five feet of the finished ground surface. Each lift must be compacted prior to placing the subsequent lift. Prior to compaction, the backfill should be moisture conditioned to within 3 percent of the optimum moisture content, if necessary. The backfill should be compacted in accordance with the criteria discussed above in the structural fill section of this report. Sanitary Sewer Main Where the pipe is bedded and/or backfilled with free-draining pea gravel, crushed rock, sand or gravel, and where the pipe invert slopes more than 5 percent, we recommend that backfill seepage barriers be constructed at appropriate intervals to prevent movement of ground water through the bedding or backfill soils. Seepage barriers are typically spaced 100 feet apart for grades of 20 percent or less. Steeper utility trench grades will require closer spacing, probably 30 feet or less. We recommend that seepage barriers consist of CDF (controlled density fill). Alternatively, impermeable soils such as silt or clay with or without cement or bentonite could be used, but we believe that it would be easier and more economical to use simple forming to place CDF barriers prior to placing trench backfill. Each seepage barrier should be notched at least 12 inches into the base and sides of the trench to key the barrier into the native soils. Although it is desirable to also notch into the trench sidewalls, we understand that this would be difficult to do if a trench box is used as temporary shoring. If the contractor can suggest an alternative, we should be contacted to evaluate the suggested option. Care must be taken during barrier construction to avoid pipe damage. Information Provided by Jeff Parks on 09.30.19 112 of 350 The barriers should extend from the base of the key trench, surround each pipe, and extend a distance of at least 2 feet or one pipe diameter, whichever is greater, above the top of the pipe bedding. They should be at least 2 feet long measured parallel to the pipes. At manhole locations, the seepage barriers could be constructed using CDF backfill on all sides of the manhole. Sedimentation and Erosion Control In our opinion, the erosion potential of the on-site soils is slight to very severe (i.e., low to very high). Construction activities including stripping and grading will expose soils to the erosional effects of wind and water. The amount and potential impacts of erosion are partly related to the time of year that construction actually occurs. Wet weather construction will increase the amount and extent of erosion and potential sedimentation. Erosion and sedimentation control measures may be implemented by using a combination of interceptor swales, straw bale barriers, silt fences and straw mulch for temporary erosion protection of exposed soils. All disturbed areas should be finish graded and seeded as soon as practical to reduce the risk of erosion. Erosion and sedimentation control measures should be installed and maintained in accordance with the requirements of the City of Auburn. Foundations We recommend that the planned residences be supported on spread footings founded on the medium dense to very dense native glacial deposits or on properly compacted structural fill extending down to dense to very dense glacial deposits. If structural fill is used to support foundations then the zone of structural fill should extend beyond the faces of the footing a distance at least equal to the thickness of the structural fill. Foundation Design For shallow foundation support, we recommend perimeter footing widths of at least 12, 15 and 18 inches for one-, two-, and three-story homes, respectively. Interior, isolated column footings should be at least twice as wide as the perimeter footing widths described above for the representative number of floors in the home. Provided that footings are supported as recommended above, an allowable bearing value of 2,000 psf may be used for footings supported on the medium dense to very dense glacial deposits or on structural fill compacted to at least 95 percent MDD placed over the glacial soils. This allowable bearing pressure applies to the total dead and long-term live loads and may be increased up to one-third for short- term live loads such as wind or seismic forces. The design frost depth for the Puget Sound area is 12 inches, therefore, we recommend that exterior footings for structures be founded at least 18 inches below lowest adjacent finished grade. Interior footings should be founded at least 12 inches below bottom of slab or adjacent finished grade. Foundation Settlement We estimate that the post-construction settlement of footings founded as recommended above will be less than one inch. Differential settlement between comparably loaded column footings or along a 25-foot-section of continuous wall footing should be less than ½ inch. We expect most of the footing settlements will occur as loads are applied. Loose or disturbed soils not removed from the footing excavation prior to placing concrete will result in additional settlement. Information Provided by Jeff Parks on 09.30.19 113 of 350 Immediately prior to placing concrete, all debris and soil slough that accumulated in the footings during forming and steel placement must be removed. Debris or loose soils not removed from the footing excavations will result in increased settlement. If wet weather construction is planned, we recommend that all footing subgrades be protected using a lean concrete mud mat. The mud mat should be placed the same day that the footing subgrade is excavated and approved for foundation support. We recommend that all footing excavations be evaluated by a representative of our firm immediately before any structural fill, mud mat, steel or concrete is placed, to evaluate if the work is being completed in accordance with our recommendations and that subsurface conditions are as expected. Lateral Resistance Lateral loads may be resisted by a combination of friction between the footing and the supporting soil, and by the passive lateral resistance of the soil surrounding the embedded portions of the footings. For shallow foundations constructed as recommended above, the allowable frictional resistance may be computed using a coefficient of friction of 0.35 applied to the vertical dead load. The allowable passive resistance on the sides of the footings may be computed using an equivalent fluid density of 300 pounds per cubic foot (pcf) if the footings are surrounded by medium dense to very dense native soil or structural fill. The structural fill should extend out from the face of the foundation element for a distance at least equal to three times the depth of the element and be compacted to at least 95 percent of the MDD (ASTM D-1557). The above values include a factor of safety of about 1.5. Footing Drains We recommend that perimeter footing drains be installed around each house. The perimeter drains should be installed at the base of the exterior footings. The perimeter drains should be provided with cleanouts and should consist of at least 4-inch-diameter perforated pipe placed on a 3-inch bed of, and surrounded by, 6 inches of drainage material enclosed in a non-woven geotextile fabric such as Mirafi 140N (or approved equivalent) to prevent fine soil from migrating into the drain material. We recommend that the drainpipe consist of either heavy-wall solid pipe (SDR-35 PVC, or equal) or rigid corrugated smooth interior polyethylene pipe (ADS N-12, or equal). We recommend against using flexible tubing for footing drainpipes. The drainage material should consist of pea gravel or “Gravel Backfill for Drains” per WSDOT Standard Specifications, Section 9 03.12(4). The perimeter drains should be sloped to drain by gravity, if practicable, to a suitable discharge point, preferably a storm drain. We recommend that the cleanouts be covered, and be placed in flush mounted utility boxes. Water collected in roof downspout lines must not be routed to the footing drain lines. Below Grade Walls and Retaining Walls The concept level design suggests that cuts and fills at the site may range up to 35 feet. At this time it is not known if these grade transitions will be supported by retaining walls or by permanent inclined slopes. If retaining structures are selected, we can provide recommendations for suitable retaining wall types and design parameters after the geometry is better defined (location, layout, height, etc.). There is a strong likelihood that below-grade foundation walls and conventional concrete walls or concrete masonry unit (CMU) block walls will be used at the site, so recommendations for these types of retaining walls are provided below. Information Provided by Jeff Parks on 09.30.19 114 of 350 Design Parameters Lateral earth pressures for design of conventional below-grade walls and retaining structures should be evaluated using equivalent fluid densities of 35 pounds per cubic foot (pcf) and 53 pcf for level backfill conditions and backfill inclined at 2H:1V, respectively, provided that the walls will not be restrained against rotation when backfill is placed. Linear interpolation can be used to assess the design lateral earth pressures for intermediate slope inclinations. If the walls will be restrained from rotation, we recommend using equivalent fluid densities of 55 pcf and 80 pcf for level backslope and 2H:1V backslope conditions, respectively. Walls are assumed to be restrained if top movement during backfilling is less than H/1000, where H is the wall height. These lateral soil pressures do not include the effects of surcharges such as floor loads, traffic loads or other surface loading. Surcharge effects should be included as appropriate. If vehicles can approach the tops of exterior walls to within 3/4 the height of the wall, a traffic surcharge should be added to the wall pressure. For car parking areas, the traffic surcharge can be approximated by the equivalent weight of an additional 1 foot of soil backfill behind the wall. For delivery truck parking areas and access driveway areas, the traffic surcharge can be approximated by the equivalent weight of an additional 2 feet of soil backfill behind the wall. Surcharge loading from earthquakes can be modeled as a uniform lateral earth pressure of 7H, where H represents the wall height, for both restrained and unrestrained walls. These recommendations are based on the assumption that all retaining walls at this project will be provided with backdrainage, as discussed below. The values for soil bearing, frictional resistance and passive resistance presented above for foundations are applicable to retaining wall design. Footings for walls located in level ground areas should be founded at a depth of 18 inches below the adjacent grade. Embedment for footings founded in areas with sloping ground should be evaluated on a case-by-case basis. Backdrainage To reduce the potential for hydrostatic water pressure buildup behind the retaining walls, we recommend that the walls be provided with backdrainage. Backdrainage can be achieved by using free draining material with perforated pipes to discharge the collected water. Free draining material should consist of a mixture of about 30 to 40 percent clean medium to coarse sand and 60 to 70 percent fine gravel, with negligible fine material (smaller than no. 200 sieve.) Alternatively, the free draining material can consist of clean gravel (as discussed above for footing drains) surrounded by a non-woven geotextile fabric such as Mirafi 140N (or approved equivalent). The zone of free draining material should be at least 2 feet wide and should extend from the base of the wall to within 1 foot of the ground surface. The free draining material should be covered with 1 foot of less permeable material, such as the on-site ice contact and till soils. A 4-inch-diameter perforated collector pipe should be installed within the free-draining material at the base of each wall. We recommend using either heavy-wall solid pipe (SDR-35 PVC, or equal) or rigid corrugated smooth interior polyethylene pipe (ADS N-12, or equal). We recommend against using flexible tubing for wall backdrain pipe. The footing drain recommended above can be incorporated into the bottom of the backdrainage zone and used for this purpose. The pipes should be laid with minimum slopes of one percent and discharge into the stormwater collection system to convey the water off site. The pipe installations should include a cleanout riser with cover located Information Provided by Jeff Parks on 09.30.19 115 of 350 at the upper end of each pipe run. The cleanouts could be placed in flush mounted access boxes. The roof downspouts should not discharge into the perforated pipes intended for providing wall backdrainage. Alternatively, where seepage at the face of a wall is not objectionable, the walls can be provided with weepholes to discharge water from the free draining wall backfill material. The weepholes should be 2-inch-diameter, and spaced about every 8 feet center-to-center along the base of the walls. The weepholes should be backed with galvanized heavy wire mesh to prevent loss of the backfill material. Construction Considerations Care should be taken by the contractor during backfilling to avoid overstressing the retaining walls. Zones of wall backfill not supporting structural elements should be compacted to between 90 and 92 percent of maximum dry density. Compaction of at least 95 percent will be needed in the upper 2 feet and at least 92 percent below that where the backfill supports structural elements such as slabs or driveways. Heavy compaction equipment should not be operated within 5 feet of below-grade walls or retaining structures to avoid overstressing the walls. Hand-operated equipment should be used in this zone. In addition, the contractor should keep all heavy construction equipment away from the top of retaining walls a distance equal to ¾ the height of the wall, or at least 5 feet, whichever is greater. Floor Slab Support We expect that floor slabs can be supported on the medium dense to very dense native soil encountered in our explorations or on properly compacted structural fill extending down to these soils. However, we recommend that an appropriate capillary break and vapor retarder be installed below the floor slab in the proposed buildings to reduce the risk of moisture migration through the on-grade floor slab. This is especially important since zones of groundwater seepage may be present below the planned floor slab level in more permeable layers within the native soil. If zones of significant seepage are observed during construction, then additional drainage protection such as a system of perforated drainpipes located below the floor slab within the capillary break material may be necessary. We recommend that floor slabs be constructed on a gravel layer to provide uniform support, drainage, and to act as a capillary break. The gravel layer should consist of at least 4 inches of clean gravel with a maximum size of ¾ inches and negligible sand or silt. If prevention of moisture migration through the slab is essential in the buildings, (e.g., in portions of the building areas where an adhesive will be used to attach tile or carpeting, for storage areas, and for enclosed areas), a vapor retardant such as plastic sheeting should be installed between the slab and the gravel layer. It may also be prudent to apply a sealer to the slab to further retard the migration of moisture through the floor. Seismicity The Puget Sound area is a seismically active region and has experienced thousands of earthquakes in historical time. Seismicity in this region is attributed primarily to the interaction between the Pacific, Juan de Fuca and North American plates. The Juan de Fuca plate is subducting beneath the North American Plate. Each year 1,000 to 2,000 earthquakes occur in Oregon and Washington. However, few of these are typically felt because the majority of the earthquakes are relatively minor, smaller than Richter magnitude 3. Information Provided by Jeff Parks on 09.30.19 116 of 350 Potential seismic hazards from earthquakes include ground shaking, liquefaction, ground rupture from lateral spreading and surface fault rupture, and landslides. Our opinions regarding the likelihood of these seismic hazards occurring at the site are presented below. These opinions are based on the seismicity criteria recommended in the 2012 edition of the International Building Code (IBC). Ground Shaking There is a risk of earthquake induced ground shaking at the site, as with all sites in the Puget Sound region, and the intensity of the ground shaking could be severe. The severity of ground shaking will primarily be a function of the earthquake magnitude and proximity to the site. In our opinion, strong ground shaking should be considered in the design of the structures and improvements at this site. We recommend that the seismic ground shaking at the site be evaluated in accordance with the applicable edition of the IBC. TABLE 1. 2012 SEISMIC DESIGN PARAMETERS 2012 IBC Parameter Recommended Value Soil Profile Type D Short Period Spectral Response Acceleration, SS (percent g) 124.4 1-Second Period Spectral Response Acceleration, S1 (percent g) 47.4 Seismic Coefficient, FA 1.0 Seismic Coefficient, FV 1.50 Peak Ground Acceleration (percent g) 51.0 Liquefaction Potential Liquefaction is a phenomenon where soils experience a rapid loss of internal strength as a consequence of strong ground shaking. Ground settlement, lateral spreading and/or sand boils may result from soil liquefaction. Structures supported on liquefied soils could suffer foundation settlement or lateral movement that could be severely damaging to the structures. Conditions favorable to liquefaction occur in loose to medium dense, clean to moderately silty sand that is below the groundwater level. Based on our evaluation of the subsurface conditions observed in the explorations completed at the site, it is our opinion that the potential for liquefaction at the site is low. Ground Rupture Ground rupture from lateral spreading is associated with liquefaction. Lateral spreading involves lateral displacements of large volumes of liquefied soil, and can occur on near-level ground as blocks of surface soils displace relative to adjacent blocks. In our opinion, ground rupture resulting from lateral spreading at the site is unlikely because the potential for liquefaction is low. Because of the thickness of the Quaternary sediments below the site, which are inferred to be more than 1,000 feet thick, the potential for surface fault rupture is considered remote. Information Provided by Jeff Parks on 09.30.19 117 of 350 Pavement Recommendations and Subgrade Preparation Subgrade Preparation Parking area and access drive pavement subgrades should be prepared as described previously in the Earthwork section of this report. In addition to these requirements, we recommend that the prepared subgrade be proofrolled thoroughly prior to paving to locate any soft or pumping soils. If proofrolling is not practical, GeoEngineers should evaluate the prepared subgrade with a hand probe rod. If soft or pumping soils are encountered, such unsuitable subgrade soils should be overexcavated and replaced. The depth of overexcavation should be determined by GeoEngineers. It may be possible to limit the depth of overexcavation of unsuitable subgrade soils by placing a geotextile reinforcement fabric such as Mirafi 600X (or approved equivalent) on the overexcavated subgrade and covering the geotextile with base course material or rock spalls. The geotextile will provide additional support by bridging over the soft material, and will help reduce fines contamination into the gravel or rock spalls. The combination of geotextile and gravel or rock should provide a stable base on which to place and compact other pavement base course materials. Asphalt Concrete Pavement Paved areas exposed to automobile traffic only should consist of 2 inches of HMA, Class ½ inch, PG 58 22 over 4 inches of crushed surfacing base course. In areas of truck traffic, new pavement sections should consist of at least 3 inches of HMA over a minimum of 6 inches of crushed surfacing base course. The crushed surfacing base course should meet the requirements of Section 9-03.9(3) of the 2004 WSDOT Standard Specifications. The crushed surfacing base course should be compacted to at least 95 percent of the maximum dry density prior to HMA placement. Asphalt-Treated Base Because pavements may be constructed during the wet seasons, consideration may be given to covering the areas to be paved with asphalt-treated base (ATB) for protection. Parking areas should be surfaced with 3 inches of ATB, and truck driveways for materials delivery should be surfaced with 6 inches of ATB. Prior to placement of the final pavement sections, we recommend that areas of ATB pavement failure be removed and the subgrade repaired. If ATB is used and is serviceable when final pavements are constructed, the crushed surfacing base course can be eliminated, and the design asphalt concrete pavement thickness can be placed directly over the ATB. Drainage Considerations The following discussion is for shallow groundwater seepage encountered during residential construction. Additional specific dewatering design for pond construction will be required during final design and is not within these considerations. We anticipate shallow groundwater seepage could be encountered in excavations depending on the time of year construction takes place, especially in the winter months. However, we expect that this seepage water can be handled by digging interceptor trenches in the excavations and pumping from sumps. The seepage water if not intercepted and removed from the excavations will make it difficult to place and compact structural fill and may destabilize cut slopes. All paved and landscaped areas should be graded so that surface drainage is directed away from the buildings to appropriate catch basins. Information Provided by Jeff Parks on 09.30.19 118 of 350 Water collected in roof downspout lines must not be routed to the footing drain lines. Roof downspout water should be routed to appropriate discharge points in separate pipe systems. Grading Considerations The site includes slopes that are locally steeper than 40 percent, and relatively large areas where slopes are between 15 and 40 percent. In addition, the site soils encountered in the explorations contain a high percentage of fines (particles passing the No. 200 sieve) and are highly moisture sensitive. These soils will be difficult to operate on and compact when they are wetter than the optimum moisture content for compaction. Accordingly, we recommend that site preparation and earthwork be completed during the normally dry months of the year (May through September). Effective erosion and sedimentation controls must be implemented during construction so that potential impacts to adjacent areas are reduced. The erosion and sediment control measures used for this project should be in accordance with the requirement of the City of Auburn. Benching Where new fill is placed on existing slopes, the new fill should be keyed into the existing slopes as described in Section 2-03.3(14) of the 2016 WSDOT Standard Specifications for embankment construction, except as noted herein. The benches should be keyed into slopes and into medium dense to dense native soils. We recommend that the benches be at least 5 feet wide into the slope, with the vertical height between benches not more than 3 feet. Each bench should be sloped outward to drain. Also, the bench surfaces should be thoroughly compacted prior to placing new embankment fill soils. Existing unsuitable organic, fill and loose soils must be removed from areas to receive fill. Terracing We recommend that terraces be included in permanent cut and fill slopes to control surface runoff and erosion on these slopes. The 2012 IBC provides requirements for terracing in Section J109 of Appendix J as follows: Terraces at least 6 feet in width shall be established at not more than 30-foot vertical intervals on all cut or fill slopes to control surface drainage and debris. Suitable access shall be provided to allow for cleaning and maintenance. Where vertical slope heights exceed 30 feet, we recommend that a terrace be provided at the approximate midpoint of the slope. Proposed Development of Storm Ponds The slope stability analyses provides an evaluation regarding the proposed geometry and depth of Ponds 1 and 2. Based on the results of our stability analysis, we conclude that the current concepts for the two ponds are feasible, provided that drainage measures, wall embedment and other measures are implemented to increase the factor of safety against sliding for seismic loading conditions. Pond 1 is located near the toe of slopes that are locally 20 percent and steeper. Our slope stability analysis indicates that the pond and berms are feasible with some required drainage design. Construction of Pond 1 will need to be preceded by temporary dewatering of the hillside above the pond in order to reduce the risk of “blowout” of the excavation face during construction when heaving sand and high groundwater pressures Information Provided by Jeff Parks on 09.30.19 119 of 350 are encountered. Permanent dewatering measures will be required to lower the groundwater table upslope, from and below the proposed pond over the long term. We recommend further analysis to assess the magnitude of temporary and permanent dewatering that will be required. To refine our drainage design recommendations, we completed boring B-9 and installed a monitoring well upslope of B-6 and B-7 to confirm the presence and depth to the sandy advance outwash unit and groundwater. Groundwater is currently being monitored at B-6, B-7, B-8, B-9 and B-11. Our slope stability analyses for Pond 2 indicate that the configurations for the pond and berms are feasible with some required drainage design related to the proposed retaining wall at the toe of the cut for the pond. Proposed Development on Slopes Exceeding 40 Percent General grading of the site and road development will include those areas identified as having slopes locally greater than 40 percent that are defined by the City critical areas code as Landslide Hazards class IV. The slopes greater than 40 percent have an approximate slope distance of approximately 100 feet or less. However, these areas appear to be generally consistent with previous geologic mapping as dense glacial till or advance outwash with overlying sand and gravel ice contact deposits. We observed no indication of slope movement including no observed tilted or pistol butted conifer trees during our reconnaissance of these areas and noted that constructed fill slopes for Evergreen Way SE dovetail with existing native slopes steeper than 40 percent that followed the EIS studies completed by GeoEngineers (2004). Based on our evaluation and slope stability analyses, we conclude that the proposed site development including lots and roadways identified in Apex’s slope mapping within areas greater 40 percent can be accommodated with adequate static and seismic factors of safety for both finished 2H:1V cut and fill slopes with the use of mitigating measures described previously in the Stability Analysis section of this report. Downstream Drainage Mitigation Based on the information we have to date, it is our opinion that mitigation for capacity or potential erosion in Streams A and B, or Tributary 0043 is not required because stream flows are expected to remain unchanged. In addition, the buffering provided by indirect discharge from the designed stormwater ponds to the stream by routing flow overland and through onsite wetlands will dampen effects expected from a shorter runoff duration caused by the increased impervious surface from site development. Active fluvial processes will not be changed by the project. However, in the future, if headcutting on Streams A and B should occur due to unanticipated, changed conditions, and threaten upstream wetland integrity, mitigation could be implemented. Possible mitigation measures include bed and bank armoring with rip rap, step pool stream construction, and/or other such grade control structures. The conceptual design for the discharge from the stormwater ponds to the wetlands through the dispersion trenches aims to minimize potential erosion. Where possible, existing slopes and gradients will remain intact and native vegetation will be undisturbed (Felix Jacobs, personal communication December 16, 2014). Soil erosion between the dispersion trench discharge and the wetland receiving waters should be expected in areas where existing vegetation will be removed and areas of ground disturbance associated with pond, dispersion trench, and other facility construction such as the wetland mitigation construction planned at Wetland B. The severity of this type of erosion is difficult to predict but would be expected to increase over time if bare soil remains exposed on slopes. Potential erosion should be mitigated either by re-establishing slopes and vegetation with root structure and mass similar to the existing conditions, or engineered solutions should be considered. Ground slopes downstream of the Information Provided by Jeff Parks on 09.30.19 120 of 350 dispersion trenches should be constructed with gradients less that 15 percent, in accordance with City design criteria. Other engineering solutions include design and construction of slope grade controls and/or placement of geotextile or geogrid-type products on the slope that allow planting through the material in compliance with wetland buffer plant requirements. If planting and root structures are to be part of the mitigation plan, planting should take place so that plants are well established prior to full operation of the dispersion trenches. LIMITATIONS We have prepared this report for the exclusive use of JDH Investment Group, LLC and their authorized agents for the Diamond Valley Estates Development project in Auburn, Washington. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in the field of geotechnical engineering in this area at the time this report was prepared. No warranty or other conditions, express or implied, should be understood. Please refer to Appendix F titled “Report Limitations and Guidelines for Use” for additional information pertaining to use of this report. REFERENCES Apex Engineering, 2014. Preliminary Plat Conceptual Storm Drainage Report for Diamond Valley Estates. March 26, 2014. Apex Engineering, Diamond Valley Estates, Critical Slope Exhibit, Sheet 19 of 19, Scale 1 inch:100 feet, dated December 2, 2014. Apex Engineering, Diamond Valley Estates, Existing Slope Exhibit, Scale 1 inch:200 feet, dated April 4, 2016. City of Auburn, Comments Diamond Valley Estate, 16 pages, August 1, 2014. City of Auburn, Municipal Code, Title 16, Chapter 16.10, Critical Area, accessed on March 16, 2014 at http://www.codepublishing.com/wa/auburn/. City of Bellevue, 2010, Geotechnical Report & Stability Analysis Requirements. DBM Consulting Engineers, 2000. Downstream analysis for the Kersey Three Project, Sites located south of Kersey Way between the intersections of 47th Street SE and 53rd Street SE, Auburn, Washington. August 21, 2000. GeoEngineers, Inc., (2004), Geologic, Hydrogeologic and Geotechnical Engineering Services, Proposed Kersey III Subdivision, Auburn, Washington, Revised Report, March 5, 2004. Geotech Consultants, Inc., Addendum to Geotechnical Engineering Study, Proposed Forest Glen at Lakeland, prepared for Roger Gillette (Gillette Plat), 37 p., April 4, 2008. Information Provided by Jeff Parks on 09.30.19 121 of 350 Harrelson, C.C., Rawlins, C.L., Potyondy, J.P. 1994. Stream Channel Reference Sites: An Illustrated Guide to Field Technique. General Technical Report RM-245. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 61 p. Hart Crowser & Associates, Inc., 1982, Ground Water Study, Auburn, Washington. Consultant’s report prepared for Pool Engineering Inc., dated July 21, 1982. Jacobs, Felix. Personal communication via email November 24, 2014. Diamond Valley Estates, Sections for Wetland Flow Comparison and Calculated Flows From Ponds To Wetlands. Apex Engineering. Jacobs, Felix. Personal communication via email November 26, 2014. Diamond Valley Estates, Calculated flows velocities at dispersion trenches. Apex Engineering. Luzier, J.E., 1969, Geology and Ground-Water Resources of Southwestern King County, Washington. Washington State Dept. of Ecology, Water Supply Bulletin 28. Mullineaux, D.R., 1965, Geologic Map of the Auburn Quadrangle, King & Pierce Counties, Washington. U.S. Geological Survey, Geologic Quadrangle Map GQ-406.Washington State Department of Transportation, 2012, “Standard Specifications for Road, Bridge and Municipal Construction.” U.S. Geological Survey, Stream Stats, Washington State, http://streamstatsags.cr.usgs.gov, accessed November 12, 2014. Washington State Department of Ecology, Northwest Regional Office, 2002a, review of well records and boring logs on file; information provided on January 24, 2002. International Code Council, 2012, “International Building Code.” Washington State Department of Transportation, 2015, Geotechnical Design Manual, M 46-03.08. Washington State Department of Transportation, 2016, Standard Specifications for Road, Bridge and Municipal Construction, M 41-10. Woodward, G.G., Packard, F.A., Dion, N.P., and Sumioka, S.S., 1995, Occurrence and quality of ground water in southwestern King County, Washington: U.S. Geological Survey Water-Resources Investigation Report 92-4098, 69 p., 4 plates. Information Provided by Jeff Parks on 09.30.19 122 of 350 FIGURES Information Provided by Jeff Parks on 09.30.19 123 of 350 µ Vicinity Map Figure 1 Diamond Valley Estates DevelopmentAuburn, Washington Pierce King Thurston Kitsap Mason Tacoma §¨¦5 UV16 UV167 UV512 UV161 UV163 2,000 2,0000 Feet Data Sources: ESRI Data & Maps, Street Maps 2005Base map from ESRI Data Online. Notes:1. The locations of all features shown are approximate.2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication.3. It is unlawful to copy or reproduce all or any part thereof, whether for personal use or resale, without permission. Transverse Mercator, Zone 10 N North, North American Datum 1983North arrow oriented to grid northOffice: RedmondPath: \\red\projects\21\21166001\GIS\21166001_F1_VM.mxdMap Revised: 17 December 2014 glohrmeyerSITE Property Boundary Information Provided by Jeff Parks on 09.30.19 124 of 350 FEET 0200 200 Notes 1. The locations of all features shown are approximate. 2. This drawing is for information purposes. It is intended to assist in showing features discussed in an attached document. GeoEngineers, Inc. cannot guarantee the accuracy and content of electronic files. The master file is stored by GeoEngineers, Inc. and will serve as the official record of this communication. Reference: Base CAD files 30153-03.dwg and 30153wrk 11-26-14.dwg provided by Apex Engineering. Dispersion trench velocity values provided by Felix Jacobs, personal communication, 11-26-14. Legend Figure 2 Diamond Valley Estates Development Auburn, Washington Site Plan TP-25 TP-26 TP-24 B-8 Boring by GeoEngineers for current study Test Pit by GeoEngineers for current study Boring by GeoEngineers (2004) Test Pit by GeoEngineers (2004) Test Pit by Earth Consultants (2000) B-1 TP-1 B-1 TP-1 B-2 B-3 B-1 TP-14 TP-13 TP-12 TP-11 TP-10 TP-6 TP-5 TP-7 TP-8 TP-9 TP-2 TP-3 TP-1 TP-4 B-6 B-7 ECTP-5 ECTP-5 ECTP-6 ECTP-7 ECTP-8 ECTP-3 ECTP-2 ECTP-1 ECTP-4 TP-27 TP-28TP-29 TP-30 B-11 B-9 Dispersion Trench Location with Velocities (fps - Feet Per Second) Cross-Section Location 0.6 fps 0 . 6 f p s 0.64fps0.57 fps 0.37fps1 1 2 3 4 Information Provided by Jeff Parks on 09.30.19 125 of 350 S1S1'S2S2'Information Provided by Jeff Parks on 09.30.19126 of 350 200 400600800 1000 1200 1400160018002000 2200 24 0 0 26 0 02 8 0 0300 0 3200 340 0 3600 3800 4000 4200 4400 4600 4800 5000 5200 5400 5600 5800 6000Evergreen WayKersey WayWetland A Wetland B Stream B Stream A Bowman Creek Property Boundary Flow Direction Stream Stationing Wetland Lambert Conformal ConicWashington State Plane North. North American Datum 1983Note: This drawing is for informational purposes. It is intended to assist in showing features discussed in an attached document.Path: Redmond P:/21/21166001/00/GIS/21166001_Elevation_Differences.mxd£Data Sources: 2010 Pierce County LiDAR. All other sources from Pierce County and GeoEngineers field reconnaissanceAll locations are approximate.Office: REDMStream Profile StationingTributary 0043 0 1,600800 Feet 200 Figure 4 Diamond Valley Estates Information Provided by Jeff Parks on 09.30.19 127 of 350 Stream ProfileDiamond Valley Estates Development Auburn, WashingtonFigure 5Information Provided by Jeff Parks on 09.30.19128 of 350 APPENDICES Information Provided by Jeff Parks on 09.30.19 129 of 350 APPENDIX A Field Explorations Information Provided by Jeff Parks on 09.30.19 130 of 350 APPENDIX A FIELD EXPLORATIONS General The locations of the explorations were located using GPS, and were surveyed after completion. These are shown on the Site Plan, Figure 2. Subsurface conditions were explored at the site by drilling five borings (B-6 through B-9 and B-11) to depths ranging from 31½ to 100 feet, and by excavating six test pits (TP-24 through TP-27, TP-29 and TP-30) to depths ranging from 11 to 14 feet. The borings were drilled using one or more of the following methods, depending on subsurface conditions: (1) hollow-stem auger (HSA) using a CME 850 track-mounted drill rig; (2) mud rotary using a CME 850 track-mounted drill rig; (3) sonic drilling, using a track-mounted spider-sonic F1576 with 6-inch outer-diameter casing 5 feet in length, or a mini-sonic with 6-inch outer-diameter casing 10 feet in length. The test pits were excavated using a track hoe PC 120 excavator. Borings The borings were continuously monitored by a geologist from our firm who examined and classified the soils encountered, obtained representative soil samples, observed groundwater conditions and prepared a detailed log of each exploration. In borings advanced using HSA or mud rotary equipment, soils were generally sampled at 2½- or 5-foot vertical intervals with a 2-inch outside-diameter split-barrel standard penetration test (SPT). In borings advanced using sonic drilling equipment soil was collected continuously in 10-foot-long runs. From these runs, soil was generally sampled every 5 feet, or where changes in soil units were documented. An SPT sampler was occasionally also used for sampling, but was driven at depths based on lithology, not pre-determined intervals. SPT samples were obtained by driving the sampler 18 inches into the soil with a 140-pound automatic hammer. The number of blows required for each 6 inches of penetration was recorded. The blow count ("N-value") of the soil was calculated as the number of blows required for the final 12 inches of penetration. This resistance, or N-value, provides a measure of the relative density of granular soils and the relative consistency of cohesive soils. Where very dense soil conditions preclude driving the full 18 inches, the penetration resistance for the partial penetration was entered on the logs. The blow counts are shown on the boring logs at the respective sample depths. Soils encountered in the borings were visually classified in general accordance with the classification system described in Figure A-1. A key to the boring log symbols is also presented in Figure A-1. The logs of the borings are presented in Figures A-2 through A-6. The boring logs are based on our interpretation of the field and laboratory data and indicate the various types of soils and groundwater conditions encountered. The logs also indicate the depths at which these soils or their characteristics change, although the change may actually be gradual. If the change occurred between samples, it was interpreted. The densities noted on the boring logs are based on the blow count data obtained in the borings and judgment based on the conditions encountered. Observations of groundwater conditions were made during drilling. The groundwater conditions encountered during drilling are presented on the boring logs. Groundwater conditions observed during drilling represent a short-term condition and may or may not be representative of the long-term groundwater conditions at the site. Groundwater conditions observed during drilling should be considered approximate. Information Provided by Jeff Parks on 09.30.19 131 of 350 We installed monitoring wells in each of the borings following drilling to allow subsequent measurement of groundwater levels. Each well was 2 inches in diameter and placed at depths relative to the groundwater table. These monitoring wells are the property of the project owner, and should be decommissioned by a licensed well driller in accordance with Chapter 173-160 of the Washington State Administrative Code (WAC) when they are no longer needed for data collection. Alternatively, the wells could be kept intact for use during project bidding and then be decommissioned under the construction contract. For well construction details, refer to the corresponding boring log in Figures A-2 through A-6. Test Pits The test pits were completed using a track hoe excavator. The test pits were continuously monitored by a geologist from our firm who examined and classified the soils encountered, obtained representative soil samples, observed groundwater conditions and prepared a detailed log of each test pit. Representative soil samples were collected where distinct soil units were observed in the excavation. Soils encountered in the test pits were visually classified in general accordance with the classification system described in Figure A-1. A key to the test pit log symbols is also presented in Figure A-1. The logs of the test pits are presented in Figures A-5 to A-12. The test pits logs are based on our interpretation of the field and laboratory data and indicate the various types of soils and groundwater conditions encountered. The logs also indicate the depths at which these soils or their characteristics change, although the change may actually be gradual. If the change occurred between samples, it was interpreted. The densities noted on the boring logs are based on the blow count data obtained in the test pits and judgment based on the conditions encountered. Information Provided by Jeff Parks on 09.30.19 132 of 350 AC Cement ConcreteCC Asphalt Concrete No Visible Sheen Slight Sheen Moderate Sheen Heavy Sheen Not Tested NS SS MS HS NT ADDITIONAL MATERIAL SYMBOLS Measured groundwater level in exploration, well, or piezometer Measured free product in well or piezometer Graphic Log Contact Groundwater Contact Material Description Contact Laboratory / Field Tests Sheen Classification Sampler Symbol Descriptions NOTE: The reader must refer to the discussion in the report text and the logs of explorations for a proper understanding of subsurface conditions. Descriptions on the logs apply only at the specific exploration locations and at the time the explorations were made; they are not warranted to be representative of subsurface conditions at other locations or times. GRAPH Topsoil/ Forest Duff/Sod Crushed Rock/ Quarry Spalls FIGURE A-1 2.4-inch I.D. split barrel SYMBOLS TYPICAL KEY TO EXPLORATION LOGS CR DESCRIPTIONSLETTER TS GC PT OH CH MH OL GM GP GW DESCRIPTIONS TYPICAL LETTER (APPRECIABLE AMOUNT OF FINES) MAJOR DIVISIONS POORLY-GRADED SANDS, GRAVELLY SAND PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS CLEAN SANDS GRAVELS WITH FINES CLEAN GRAVELS HIGHLY ORGANIC SOILS SILTS AND CLAYS SILTS AND CLAYS SAND AND SANDY SOILS GRAVEL AND GRAVELLY SOILS (LITTLE OR NO FINES) FINE GRAINED SOILS COARSE GRAINED SOILS SW MORE THAN 50% OF COARSE FRACTION RETAINED ON NO. 4 SIEVE CL WELL-GRADED SANDS, GRAVELLY SANDS SILTY GRAVELS, GRAVEL - SAND - SILT MIXTURES LIQUID LIMIT GREATER THAN 50 SILTY SANDS, SAND - SILTMIXTURES (APPRECIABLE AMOUNT OF FINES) SOIL CLASSIFICATION CHART LIQUID LIMIT LESS THAN 50 SANDS WITH FINES SP (LITTLE OR NO FINES) ML SC SM NOTE: Multiple symbols are used to indicate borderline or dual soil classifications MORE THAN 50% OF COARSE FRACTION PASSING NO. 4 SIEVE CLAYEY GRAVELS, GRAVEL - SAND - CLAY MIXTURES CLAYEY SANDS, SAND - CLAY MIXTURES INORGANIC SILTS, ROCK FLOUR, CLAYEY SILTS WITH SLIGHT PLASTICITY ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS SILTY SOILS ORGANIC CLAYS AND SILTS OF MEDIUM TO HIGH PLASTICITY INORGANIC CLAYS OF HIGH PLASTICITY MORE THAN 50% PASSING NO. 200 SIEVE MORE THAN 50% RETAINED ON NO. 200 SIEVE WELL-GRADED GRAVELS, GRAVEL - SAND MIXTURES POORLY-GRADED GRAVELS,GRAVEL - SAND MIXTURES INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS GRAPH SYMBOLS Standard Penetration Test (SPT) Shelby tube Piston Direct-Push Bulk or grab Continuous Coring Distinct contact between soil strata Approximate contact between soil strata Contact between geologic units Contact between soil of the same geologic unit %F %G AL CA CP CS DS HA MC MD OC PM PI PP PPM SA TX UC VS Percent fines Percent gravel Atterberg limits Chemical analysis Laboratory compaction test Consolidation test Direct shear Hydrometer analysis Moisture content Moisture content and dry density Organic content Permeability or hydraulic conductivity Plasticity index Pocket penetrometer Parts per million Sieve analysis Triaxial compression Unconfined compression Vane shear Blowcount is recorded for driven samplers as the number of blows required to advance sampler 12 inches (or distance noted). See exploration log for hammer weight and drop. A "P" indicates sampler pushed using the weight of the drill rig. A "WOH" indicates sampler pushed using the weight of the hammer. Rev. 02/16 Information Provided by Jeff Parks on 09.30.19 133 of 350 3 18 10 10 18 8 50/5" 59 38 50/4" 77 50/4" Brownish gray silty gravel with sand (very dense, moist) (ice contact deposits) (Very rough drilling at 1.5 feet) (Very rough and hard drilling through 5 to 6 feet) Brown fine to coarse sand with silt and gravel (very dense, moist) Cobbles at 12 feet (Very rough and hard drilling through 13.5 feet; smoother drilling at 13.5 feet) (Perched groundwater encountered during drilling) Grades to fine to medium sand with silt and gravel Brown fine to medium sand with silt and gravel (medium dense, wet) (advance outwash) (Rough drilling at 17 feet) (Smooth drilling at 19.5 feet) Becomes very dense (Perched groundwater encountered during drilling) (Very rough drilling at 20 to 22 feet) (Smooth drilling at 22 feet) With occasional gravel (Very rough and hard drilling at 34 feet; GM SP-SM SP-SM 1 2 3 4 5 6 2.0 31.0 Grout surface seal Bentonite seal Schedule 20 well casing Colorado silica sand backfill Logged By BHCDrilled Date Measured Drilling Method3/20/2014 3/20/2014 Horizontal Datum Vertical Datum DOE Well I.D.: BHV-750 A 2 (in) well was installed on 3/21/2014 to a depth of 50 (ft). 3/22/2014Easting (X) Northing (Y) Drilling Equipment 52 Top of Casing Elevation (ft)354.08 Start End Checked By Location: Proposed Pond 1 42.4 CME-850 Track Elevation (ft) Groundwater Driller Depth to Water (ft) BHCTotal Depth (ft)Hollow-Stem Auger Notes: Hammer Data Surface Elevation (ft)355.5 Automatic 140 (lbs) / 30 (in) Drop Holocene 313.2 3.57 foot stickup Steel surface monument Note: See Figure A-1 for explanation of symbols. FIELD DATA Depth (feet)0 5 10 15 20 25 30 35 IntervalElevation (feet)355350345340335330325Collected SampleRecovered (in)Blows/footGraphic LogMATERIAL DESCRIPTION GroupClassificationWater LevelSample NameTestingWELL LOG MoistureContent (%)FinesContent (%)Log of Monitoring Well B-6 Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-2 Sheet 1 of 2Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_WELL_%FInformation Provided by Jeff Parks on 09.30.19 134 of 350 11 12 10 10 5 5 50/5" 50/5" 50/3" 50/4" 50/5" 50/6" cobbles) With gravel Grades to fine to coarse sand with silt and occasional gravel (very dense, wet) Brown silty fine to coarse sand with gravel (very dense, wet) SM 7 8 9 SA 10 SA 11 12 35.0 45.0 47.0 52.0 Schedule 20, 0.030-inch-slot, well screen Bentonite 3/8-inch 8.8 15.8 8.6 6.6 Note: See Figure A-1 for explanation of symbols. FIELD DATA Depth (feet)35 40 45 50 IntervalElevation (feet)320315310305Collected SampleRecovered (in)Blows/footGraphic LogMATERIAL DESCRIPTION GroupClassificationWater LevelSample NameTestingWELL LOG MoistureContent (%)FinesContent (%)Log of Monitoring Well B-6 (continued) Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-2 Sheet 2 of 2Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_WELL_%FInformation Provided by Jeff Parks on 09.30.19 135 of 350 1 8 12 10 12 16 20 20 75 68 69 65 Grayish brown silty fine to coarse sand with gravel (medium dense, moist) (ice contact deposits) (Poor recovery) (Rough drilling at 2.5 feet) (Smooth drilling at 6 feet) Grades to silty fine to medium sand with gravel (Slightly rough drilling from 11 to 12 feet) Decreasing silt, with occasional gravel (Perched groundwater encountered during drilling) Brownish gray and very dense Brownish gray silty fine to coarse sand with trace gravel (medium dense, moist) (advance outwash) Increasing silt SM SM 1 2 3 SA 4 5 6 1.0 32.0 Concrete surface seal Bentonite seal Schedule 20 well casing Colorado silica sand backfill 10.5 15 Logged By BHCDrilled Date Measured Drilling Method3/22/2014 3/22/2014 Horizontal Datum Vertical Datum DOE Well I.D.: BHV-751 A 2 (in) well was installed on 3/22/2014 to a depth of 51 (ft). 3/22/2014Easting (X) Northing (Y) Drilling Equipment 51.5 Top of Casing Elevation (ft)357.41 Start End Checked By Location: Proposed Pond 1 29.9 CME-850 Track Elevation (ft) Groundwater Driller Depth to Water (ft) BHCTotal Depth (ft)Hollow-Stem Auger Notes: Hammer Data Surface Elevation (ft)353.99 Automatic 140 (lbs) / 30 (in) Drop Holocene 324.1 3.42 foot stickup Steel surface monument Note: See Figure A-1 for explanation of symbols. FIELD DATA Depth (feet)0 5 10 15 20 25 30 35 IntervalElevation (feet)350345340335330325320Collected SampleRecovered (in)Blows/footGraphic LogMATERIAL DESCRIPTION GroupClassificationWater LevelSample NameTestingWELL LOG MoistureContent (%)FinesContent (%)Log of Monitoring Well B-7 Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-3 Sheet 1 of 2Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_WELL_%FInformation Provided by Jeff Parks on 09.30.19 136 of 350 18 18 18 6 8 68 30 90 50/4" 50/5.5" Becomes dense (12 inch heave at 37.5 feet; driller added water to hole) (6 inch heave at 40 feet) With occasional gravel (9 inch heave at 45 feet) (Slightly rough drilling from 47 to 48 feet) 7 8 9 SA 10 11 35.0 45.0 48.5 51.5 Schedule 20, 0.030-inch-slot, well screen Bentonite 3/8-inch 19.2 12.6 Note: See Figure A-1 for explanation of symbols. FIELD DATA Depth (feet)35 40 45 50 IntervalElevation (feet)315310305Collected SampleRecovered (in)Blows/footGraphic LogMATERIAL DESCRIPTION GroupClassificationWater LevelSample NameTestingWELL LOG MoistureContent (%)FinesContent (%)Log of Monitoring Well B-7 (continued) Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-3 Sheet 2 of 2Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_WELL_%FInformation Provided by Jeff Parks on 09.30.19 137 of 350 6 6 8 18 8 12 16 23 63 39 36 59 48 41 Grayish-brown silty fine to coarse sand with gravel (medium dense, moist to wet) (ice contact deposits) (Rough drilling at 2.5 feet) Grayish brown silty gravel with sand (very dense, wet) (Very rough and hard drilling at 9.5 feet) (Rough and hard drilling at 12.5 feet; cobbles) Grayish brown silty fine to coarse sand with gravel (dense, wet) (weathered till) Grayish brown silty gravel with sand (very dense, wet) (glacial till) (Very rough drilling at 21 feet; cobbles) Becomes brownish gray (Very rough drilling at 24.5 feet) Becomes dense, moist (Very rough drilling) Becomes gray SM GM SM GM 1 2 3 MC 4 5 SA 6 7 SA 1.0 8.0 12.0 27.0 28.5 31.5 Concrete surface seal Bentonite seal Schedule 20 well casing Colorado silica sand backfill Schedule 20, 0.030-inch-slot, well screen Bentonite 3/8-inch 7.6 9.5 10.8 30.6 24.2 Logged By BHCDrilled Date Measured Drilling Method3/20/2014 3/20/2014 Horizontal Datum Vertical Datum DOE Well I.D.: BHV-749 A 2 (in) well was installed on 3/20/2014 to a depth of 31.5 (ft). 3/20/2014Easting (X) Northing (Y) Drilling Equipment 31.5 Top of Casing Elevation (ft)311.72 Start End Checked By Location: Proposed Pond 2 4.1 CME-850 Track Elevation (ft) Groundwater Driller Depth to Water (ft) BHCTotal Depth (ft)Hollow-Stem Auger Notes: Hammer Data Surface Elevation (ft)311.72 Automatic 140 (lbs) / 30 (in) Drop Holocene 307.6 2.92 foot stickup Steel surface monument Note: See Figure A-1 for explanation of symbols. FIELD DATA Depth (feet)0 5 10 15 20 25 30 IntervalElevation (feet)310305300295290285Collected SampleRecovered (in)Blows/footGraphic LogMATERIAL DESCRIPTION GroupClassificationWater LevelSample NameTestingWELL LOG MoistureContent (%)FinesContent (%)Log of Monitoring Well B-8 Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-4 Sheet 1 of 1Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_WELL_%FInformation Provided by Jeff Parks on 09.30.19 138 of 350 5 3 10 5 3 39 50/5" 50/6" 50/5" 50/6" 50/5" Brown silty sand with gravel Brownish gray sandy gravel with silt, cobbles and boulders (dense, moist) (ice contact deposits) Becomes very dense Brown silty sand with gravel (very dense, moist) Gray silty gravel (very dense, dry) Becomes brown (Perched groundwater encountered during drilling) Grayish brown sand with gravel (very dense, moist) Brown silty gravel with sand, cobbles and boulders (very dense, moist) Brownish gray sandy gravel with silt (very dense, moist) 3-inch layer of brown silt, gravel and cobbles Brown silty gravel with sand and cobbles (very dense, moist) SM GP SM GM GM SP GM GP-GM GM #1 #2 #3 #4 #5 #6 3.0 Concrete surface seal Schedule 40 PVC well casing Bentonite seal 6.9 21.2 Logged By BHCDrilled Date Measured Drilling Method5/12/2014 5/12/2014 Horizontal Datum Vertical Datum DOE Well I.D.: BIM-580 A 2 (in) well was installed on 11/14/2014 to a depth of 100 (ft). 11/17/2014Easting (X) Northing (Y) Drilling Equipment 100 Top of Casing Elevation (ft) Start End Checked By 78.0 CME-850 Track Elevation (ft) Groundwater Driller Depth to Water (ft) BHC/ERHTotal Depth (ft) HSA/Mud Rotary Sonic Notes: Hammer Data Surface Elevation (ft)402.23 Automatic 140 (lbs) / 30 (in) Drop Holocene 324.2 3.15 foot stickup Steel surface monument Note: See Figure A-1 for explanation of symbols. FIELD DATA Depth (feet)0 5 10 15 20 25 30 35 IntervalElevation (feet)400395390385380375370Collected SampleRecovered (in)Blows/footGraphic LogMATERIAL DESCRIPTION GroupClassificationWater LevelSample NameTestingWELL LOG MoistureContent (%)FinesContent (%)Log of Monitoring Well B-9 Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-5 Sheet 1 of 3Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_WELL_%FInformation Provided by Jeff Parks on 09.30.19 139 of 350 4.5 8 6 6 6 6 6 6 6 6 4 6 6 6 6 6 50/5" 56 50/2" Gray medium to coarse gravel with silt, sand, cobbles and boulders (very dense, wet) Grayish brown silty fine to coarse gravel with sand and occasional cobbles (very dense, moist) (till) Brown silty fine to coarse sand with gravel and cobbles (very dense, dry) Gray brown silty fine to coarse gravel with sand and cobbles Orange brown fine to medium sand with trace silt (dense, moist) Light brown to light gray silty fine to coarse sand with gravel (very dense, dry) Grayish brown silty fine to medium sand with occasional gravel (dense, moist) Becomes dry Orange-brown fine to medium sand with trace silt and occasional gravel (dense, moist) Brown silty fine to coarse sand with gravel (very dense, moist) Becomes to gray Grayish brown silty fine to coarse gravel with sand (very dense, moist) Brown fine to medium sand with gravel Gray silty fine to medium sand with occasional gravel (very dense, moist) Brown silty fine to medium sand with occasional gravel (dense, moist) Gray silty fine to medium sand to sandy silt with occasional gravel Brown fine to medium sand with trace silt (dense, moist) Gray fine tp coarse gravel with silt and sand (dry) Brown fine to coarse sand with silt and occasional gravel Grades to no gravel Brown fine to medium sand with trace silt (dense, moist) GP GM SM GM SP SM SM SP-SM SM GM SP SM SM SM-ML SP GP-GM SP-SM SP #7 #8 1 SA 2 3 MC 4 5 6 MC 7 %F 8 8 9 MC 10 11 SA 12 13 MC 62.0 65.0 10/20 Colorado silica sand backfill Schedule 40 PVC, 0.020-inch-slot, well screen 6.9 5.9 3.2 4.2 3.1 6.3 7.7 21.2 11.6 26.0 Note: See Figure A-1 for explanation of symbols. FIELD DATA Depth (feet)35 40 45 50 55 60 65 70 75 IntervalElevation (feet)365360355350345340335330325Collected SampleRecovered (in)Blows/footGraphic LogMATERIAL DESCRIPTION GroupClassificationWater LevelSample NameTestingWELL LOG MoistureContent (%)FinesContent (%)Log of Monitoring Well B-9 (continued) Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-5 Sheet 2 of 3Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_WELL_%FInformation Provided by Jeff Parks on 09.30.19 140 of 350 6 6 6 6 6 Brown fine to medium sand iwth silt and occasional gravel (moist) Gray silty fine to medium sand with occasional gravel and cobble (very dense, moist) Brown fine to medium sand with silt and occasional gravel (medium dense, wet) Silt and gravel content increases Grayish brown silt with trace sand and occasional gravel (very dense, moist to wet) Sand and gravel content increase, becomes more dense Becomes sandy Brown silty fine to coarse sand with gravel (very dense, moist) Brown silty fine to coarse sand with occasional gravel (dense to very dense, wet) With occasional orange brown lenses SP-SM GM SP-SM ML SM 14 SA 15 16 MC 17 18 90.0 100.0 Schedule 40 PVC end cap 14 6.5 5.9 Note: See Figure A-1 for explanation of symbols. FIELD DATA Depth (feet)80 85 90 95 100 IntervalElevation (feet)320315310305Collected SampleRecovered (in)Blows/footGraphic LogMATERIAL DESCRIPTION GroupClassificationWater LevelSample NameTestingWELL LOG MoistureContent (%)FinesContent (%)Log of Monitoring Well B-9 (continued) Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-5 Sheet 3 of 3Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_WELL_%FInformation Provided by Jeff Parks on 09.30.19 141 of 350 5 12 12 12 54 36 Dark brown silty fine to coarse gravel with sand Brown fine to coarse gravel with silt, sand and occasional organics (wood) (moist) Dark brown silty fine to coarse gravel with sand and cobbles (very dense, moist) (ice contact deposits) Becomes brown (medium dense, moist) Becomes very dense Brown silty fine to coarse sand with gravel and occasional cobbles (very dense, moist) (weathered till) Brown sandy silt with gravel (hard, moist) Brown silty fine to coarse sand with gravel and cobbles (medium dense, wet) Brown silty gravel with sand (dense, moist) (glacial till) Brown silty fine to coarse sand with gravel (dense, moist) Gray sandy silt with gravel (dense, moist) GM GP-GM GM SM ML SM GM SM ML 1 2 3 4 5 6 MC 7 8 9a 9b 10 11 MC 12 13 14 SA 15 MC 16 17 18 MC 3.0 27.0 30.0 Concrete surface seal Bentonite seal Schedule 40 PVC well casing Schedule 40 PVC, 0.020-inch-slot, well screen 10/20 Colorado silica sand backfill 4.5 11.4 9.5 7.3 7.2 9.6 Logged By BHCDrilled Date Measured Drilling Method11/11/2014 11/12/2014 Horizontal Datum Vertical Datum DOE Well I.D.: BIM-579 A 2 (in) well was installed on 11/12/2014 to a depth of 40 (ft). 11/17/2014Easting (X) Northing (Y) Drilling Equipment 40 Top of Casing Elevation (ft) Start End Checked By 32.2 Spider Sonic F1576 Elevation (ft) Groundwater Driller Depth to Water (ft) ERHTotal Depth (ft)Sonic w/ SPT Notes: Hammer Data Surface Elevation (ft)362.74 Automatic 140 (lbs) / 30 (in) Drop Holocene 330.6 2 foot stickup Steel surface monument Note: See Figure A-1 for explanation of symbols. FIELD DATA Depth (feet)0 5 10 15 20 25 30 35 IntervalElevation (feet)360355350345340335330Collected SampleRecovered (in)Blows/footGraphic LogMATERIAL DESCRIPTION GroupClassificationWater LevelSample NameTestingWELL LOG MoistureContent (%)FinesContent (%)Log of Monitoring Well B-11 Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-6 Sheet 1 of 2Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_WELL_%FInformation Provided by Jeff Parks on 09.30.19 142 of 350 Brown silty fine to medium sand with occasional gravel (very dense, moist) Light brown silty gravel with sand (very dense, moist) (advance outwash) SM GM 19 20 SA 40.0 Schedule 40 PVC end cap 2.4 19.8 Note: See Figure A-1 for explanation of symbols. FIELD DATA Depth (feet)35 40 IntervalElevation (feet)325Collected SampleRecovered (in)Blows/footGraphic LogMATERIAL DESCRIPTION GroupClassificationWater LevelSample NameTestingWELL LOG MoistureContent (%)FinesContent (%)Log of Monitoring Well B-11 (continued) Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-6 Sheet 2 of 2Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_GEOTECH_WELL_%FInformation Provided by Jeff Parks on 09.30.19 143 of 350 1 2 3 4 5 MC 6 OL SM GM SM Dark brown organic silt with sand and occasional gravel (roots) Reddish brown silty fine to medium sand with occasional gravel (loose, wet) (fill?) Brown silty gravel with sand (very dense, wet) (ice contact deposits) Brownish gray silty fine to medium sand with gravel (very dense, wet) (till) With occasional cobbles Becomes gray with coarser sand With occasional cobbles Becomes moist Test pit completed at 11 feet Rapid groundwater seepage observed at 2.5 feet Slight caving observed from 2 to 3 feet Very hard digging Continued very hard digging 9.7 Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTEC_%FLog of Test Pit TP-24 Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-7 Sheet 1 of 1 Date Excavated: Equipment: Logged By:3/19/2014 Komatsu PC 120 Total Depth (ft) BHC 11.0 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 SAMPLE Graphic LogElevation (feet)298297296295294293292291290289288Sample NameTestingGroupClassificationEncountered WaterMATERIAL DESCRIPTION REMARKS MoistureContent (%)FinesContent (%)MoistureContent (%)Information Provided by Jeff Parks on 09.30.19 144 of 350 1 2 3 4 5 6 7 OL SM GM SP-SM SM SP Dark brown organic silt with sand (soft, moist) (forest duff) Reddish brown silty fine to coarse sand with gravel (medium dense, moist to wet) (ice contact deposits) Brown silty gravel with sand (very dense, wet) Brownish gray fine to coarse sand with gravel and variable silt (very dense, wet) Brownish gray silty fine to coarse sand with gravel (very dense, wet) (till) Becomes gray Tan-gray fine to medium sand with occasional gravel (dense, wet) (advance outwash) Test pit completed at 12 feet Moderate groundwater seepage observed from 2.5 to 6.5 feet Moderate caving observed at 9 feet Hard digging with 3-inch cobbles Hard digging Very hard digging Easier digging Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTEC_%FLog of Test Pit TP-25 Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-8 Sheet 1 of 1 Date Excavated: Equipment: Logged By:3/19/2014 Komatsu PC 120 Total Depth (ft) BHC 12.0 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 12 SAMPLE Graphic LogElevation (feet)342341340339338337336335334333332331Sample NameTestingGroupClassificationEncountered WaterMATERIAL DESCRIPTION REMARKS MoistureContent (%)FinesContent (%)MoistureContent (%)Information Provided by Jeff Parks on 09.30.19 145 of 350 1 2 3 4 5 6 SA OL SM SP-SM SM SP-SM SM Dark brown organic silt with sand (soft, moist) (forest duff) Reddish brown silty fine to ocarse sand with gravel (loose, wet) (ice contact deposits) Becomes orange-brown Brownish gray fine to medium sand with silt and gravel (very dense, wet) Brownish gray silty fine to coarse sand with gravel (very dense, wet) Tan fine to medium sand with silt and occasional gravel (dense, wet) (till) Gray silty fine to medium sand with occasional gravel (very dense, wet) Test pit completed at 12 feet Moderate to rapid groundwater seepage observed at 1.75 and 8 feet Slight caving observed from 2 to 4 feet Hard digging with cobbles Easier digging 19.6 17.5 Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTEC_%FLog of Test Pit TP-26 Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-9 Sheet 1 of 1 Date Excavated: Equipment: Logged By:3/19/2014 Komatsu PC 120 Total Depth (ft) BHC 12.0 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 12 SAMPLE Graphic LogElevation (feet)333332331330329328327326325324323322Sample NameTestingGroupClassificationEncountered WaterMATERIAL DESCRIPTION REMARKS MoistureContent (%)FinesContent (%)MoistureContent (%)Information Provided by Jeff Parks on 09.30.19 146 of 350 1 2 3 4 OL GM GP-GM SM Brown organic silt with occasional gravel and trace sand Dark brown silty fine to coarse gravel with sand and trace roots (moist) (ice contact deposits) Becomes light grayish brown Brown to gray fine to coarse gravel with sand and silt (moist) Becomes light brown to light gray Cobbles observed Becomes dark gray, decreased gravel content and increased moisture Grayish brown silty coarse sand with gravel (moist) (till) Test pit completed at 14 feet No groundwater seepage observed Slight caving observed at 5.5 feet Probe penetration 0.5 feet Probe penetration 0.2 feet Hard digging Hard digging Easier digging Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTEC_%FLog of Test Pit TP-27 Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-10 Sheet 1 of 1 Date Excavated: Equipment: Logged By:11/3/2014 Komatsu PC 120 Total Depth (ft) APL 14.0 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 12 13 14 SAMPLE Graphic LogElevation (feet)401400399398397396395394393392391390389388Sample NameTestingGroupClassificationEncountered WaterMATERIAL DESCRIPTION REMARKS MoistureContent (%)FinesContent (%)MoistureContent (%)Information Provided by Jeff Parks on 09.30.19 147 of 350 1 2 3 4 OL SM GM/SM SM Dark brown organic silt with sand (roots) Brown silty fine to coarse sand with gravel (loose, moist) Grayish brown silty gravel with sand to silty fine to coarse sand with gravel (cobbles observed) (very dense, dry to moist) (ice contact deposits) Boulders encountered Becomes dry Becomes moist Becomes gray Gray silty fine to coarse sand with gravel (till) Cobbles observed Test pit completed at 13.5 feet No groundwater seepage observed Slight caving observed from 2 to 3 feet Probe penetrates 2 to 2.5 feet Hard digging Probe penetrates 2 feet Very hard digging Easier digging Easier digging Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTEC_%FLog of Test Pit TP-28 Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-11 Sheet 1 of 1 Date Excavated: Equipment: Logged By:10/31/2014 Komatsu PC 120 Total Depth (ft) BHC 13.5 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 12 13 SAMPLE Graphic LogElevation (feet)377376375374373372371370369368367366365Sample NameTestingGroupClassificationEncountered WaterMATERIAL DESCRIPTION REMARKS MoistureContent (%)FinesContent (%)MoistureContent (%)Information Provided by Jeff Parks on 09.30.19 148 of 350 1 2 3 4 OL SM GM SM GM SM Brown organic silt with occasional gravel (moist) (topsoil) Gravel observed Brown silty fine to coarse sand with occasional gravel (moist) (ice contact deposits) Increased gravel content Brown silty fine to coarse gravel with sand (moist) Cobbles observed Gray silty fine to coarse sand with gravel (cobbles observed) (moist) Becomes light gray Brown silty fine to coarse gravel with sand (cobbles observed) (moist) Becomes dark gray Increased sand content Brown silty fine to coarse sand with gravel (cobbles observed) (till) Becomes brown-gray with less gravel Test pit completed at 13.5 feet No groundwater seepage observed No caving observed Probe penetration 1.5 feet Probe penetration 0.3 feet Harder digging Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTEC_%FLog of Test Pit TP-29 Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-12 Sheet 1 of 1 Date Excavated: Equipment: Logged By:11/3/2014 Komatsu PC 120 Total Depth (ft) APL 13.5 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 12 13 SAMPLE Graphic LogElevation (feet)407406405404403402401400399398397396395394Sample NameTestingGroupClassificationEncountered WaterMATERIAL DESCRIPTION REMARKS MoistureContent (%)FinesContent (%)MoistureContent (%)Information Provided by Jeff Parks on 09.30.19 149 of 350 1 2 3 SM GP-GM Brown silty fine to coarse sand with organic matter (roots) (moist) With occasional gravel Cobbles observed Light brown to gray fine to coarse gravel with sand and silt (moist) (ice contact deposits) Cobbles observed Becomes brown, increased moisture Cobbles observed from 8 to 10 feet Becomes brown to gray Large boulders and cobbles observed Test pit completed at 13 feet No groundwater seepage observed No caving observed Probe penetrates 1.5 feet Probe penetrates 0.3 feet Ice contact Probe penetrates 0.1 feet Digging gets harder Hard digging Hard digging Notes: See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot.Redmond: Date:4/20/16 Path:W:\PROJECTS\21\21166001\GINT\2116600100.GPJ DBTemplate/LibTemplate:GEOENGINEERS8.GDT/GEI8_TESTPIT_1P_GEOTEC_%FLog of Test Pit TP-30 Diamond Valley Estates Development Auburn, Washington 21166-001-00 Project: Project Location: Project Number:Figure A-13 Sheet 1 of 1 Date Excavated: Equipment: Logged By:11/3/2014 Komatsu PC 120 Total Depth (ft) APL 13.0 Testing SampleDepth (feet)1 2 3 4 5 6 7 8 9 10 11 12 13 SAMPLE Graphic LogElevation (feet)386385384383382381380379378377376375374Sample NameTestingGroupClassificationEncountered WaterMATERIAL DESCRIPTION REMARKS MoistureContent (%)FinesContent (%)MoistureContent (%)Information Provided by Jeff Parks on 09.30.19 150 of 350 APPENDIX B Laboratory Testing Information Provided by Jeff Parks on 09.30.19 151 of 350 APPENDIX B LABORATORY TESTING Soil samples obtained from the explorations were transported to GeoEngineers’ laboratory and evaluated to confirm or modify field classifications, as well as to evaluate engineering properties of the soil samples. We selected representative samples for laboratory testing including moisture content, fines content, sieve analysis, Atterberg limits, and consolidation tests. The tests were performed in general accordance with the test methods of the ASTM International (ASTM) or other applicable procedures. Moisture Content Moisture content tests were completed in general accordance with ASTM D 2216 for representative samples obtained from the explorations. The results of these tests are presented on the exploration logs in Appendix A at the depths at which the samples were obtained. Sieve Analyses Sieve and Percent Fines (minus 200) analyses were performed on selected samples in general accordance with ASTM D 422 to determine the sample grain size distribution. The wet sieve analysis method was used to determine the percentage of soil greater than the U.S. No. 200 mesh sieve. The results of the sieve analyses were plotted and classified in general accordance with the Unified Soil Classification System (USCS) and are presented in Figures B-1 and B-4. Pebble Count We conducted a pebble count in the field along the channel floor of cross section S1. The pebble count procedure generally conformed to the Wolman Pebble Count method (Harrelson et al. 1994). The field equipment used was a pre-calibrated template (gravelometer) and a field notebook. The gravelometer was calibrated to the Wentworth size classification, based on ½ phi values. Phi is a logarithmic transformation of the ratio of a particle diameter in mm to a standard grain diameter of 1 mm. Phi values were as follows: 2, 4, 5.7, 8, 11.3, 16, 22.6, 32, 45, 64, 90 and 128. The small stream channel at cross section S1 necessitated using a pebble count area about 10 feet long by 4 feet wide. The data collection procedure was as follows: the collector averted his eyes and selected the first particle that touched the toe of his boot. The intermediate (B) axis was measured for each particle, the size recorded, and the particle discarded outside the measurement area. This process was repeated by walking across the channel until measuring 100 particles. A particle size distribution analysis was completed using Excel software following data collection. Information Provided by Jeff Parks on 09.30.19 152 of 350 FIGURE B-1 SIEVE ANALYSIS RESULTS EXPLORATION NUMBERDEPTH(ft)SOIL CLASSIFICATIONB-6B-6B-7B-742½ 451540Poorly graded sand with silt and gravel (SP-SM)Poorly graded sand with silt (SP-SM)Silty sand with gravel (SM)Silty sand (SM)21166-001-00 SAS: SAS 03-31-2014SYMBOL3/8”3”#20#200#40 #60 #1001.5”#10#43/4”01020304050607080901000.0010.010.11101001000PERCENT PASSING BY WEIGHT .GRAIN SIZE IN MILLIMETERSU.S. STANDARD SIEVE SIZESANDSILT OR CLAYCOBBLESGRAVELCOARSE MEDIUM FINECOARSE FINEBOULDERSInformation Provided by Jeff Parks on 09.30.19153 of 350 FIGURE B-2 SIEVE ANALYSIS RESULTS EXPLORATION NUMBERDEPTH(ft)SOIL CLASSIFICATIONB-8B-8TP-2622½ 3011½ Silty gravel with sand (GM)Silty gravel with sand (GM)Silty sand (SM)21166-001-00 SAS: SAS 03-31-2014SYMBOL3/8”3”#20#200#40 #60 #1001.5”#10#43/4”01020304050607080901000.0010.010.11101001000PERCENT PASSING BY WEIGHT .GRAIN SIZE IN MILLIMETERSU.S. STANDARD SIEVE SIZESANDSILT OR CLAYCOBBLESGRAVELCOARSE MEDIUM FINECOARSE FINEBOULDERSInformation Provided by Jeff Parks on 09.30.19154 of 350 FIGURE B-3 SIEVE ANALYSIS RESULTS EXPLORATION NUMBERDEPTH(ft)SOIL CLASSIFICATIONB-9B-9B-941 6982Silty gravel with sand (GM)Silty sand (SM)Poorly graded sand with silt (SP-SM)21166-001-00 SAS: SAS 11-21-2014SYMBOL3/8”3”#20#200#40 #60 #1001.5”#10#43/4”01020304050607080901000.0010.010.11101001000PERCENT PASSING BY WEIGHT .GRAIN SIZE IN MILLIMETERSU.S. STANDARD SIEVE SIZESANDSILT OR CLAYCOBBLESGRAVELCOARSE MEDIUM FINECOARSE FINEBOULDERSInformation Provided by Jeff Parks on 09.30.19155 of 350 FIGURE B-4 SIEVE ANALYSIS RESULTS EXPLORATION NUMBERDEPTH(ft)SOIL CLASSIFICATIONB-11B-1123 69Poorly graded gravel with silt and sand (GP-GM)Silty gravel with sand (GM)21166-001-00 SAS: SAS 11-21-2014SYMBOL3/8”3”#20#200#40 #60 #1001.5”#10#43/4”01020304050607080901000.0010.010.11101001000PERCENT PASSING BY WEIGHT .GRAIN SIZE IN MILLIMETERSU.S. STANDARD SIEVE SIZESANDSILT OR CLAYCOBBLESGRAVELCOARSE MEDIUM FINECOARSE FINEBOULDERSInformation Provided by Jeff Parks on 09.30.19156 of 350 APPENDIX C Logs of Previous Field Explorations and Geologic Mapping Information Provided by Jeff Parks on 09.30.19 157 of 350 Figure C-1 Information Provided by Jeff Parks on 09.30.19 158 of 350 Figure C-2 Information Provided by Jeff Parks on 09.30.19 159 of 350 Figure C-3 Information Provided by Jeff Parks on 09.30.19 160 of 350 Figure C-4 Information Provided by Jeff Parks on 09.30.19 161 of 350 Figure C-5 Information Provided by Jeff Parks on 09.30.19 162 of 350 Figure C-6 Information Provided by Jeff Parks on 09.30.19 163 of 350 Figure C-7 Information Provided by Jeff Parks on 09.30.19 164 of 350 Figure C-8 Information Provided by Jeff Parks on 09.30.19 165 of 350 Figure C-9 Information Provided by Jeff Parks on 09.30.19 166 of 350 Figure C-10 Information Provided by Jeff Parks on 09.30.19 167 of 350 Figure C-11 Information Provided by Jeff Parks on 09.30.19 168 of 350 Figure C-12 Information Provided by Jeff Parks on 09.30.19 169 of 350 Figure C-13 Information Provided by Jeff Parks on 09.30.19 170 of 350 Figure C-14 Information Provided by Jeff Parks on 09.30.19 171 of 350 Figure C-15 Information Provided by Jeff Parks on 09.30.19 172 of 350 Figure C-16 Information Provided by Jeff Parks on 09.30.19 173 of 350 Figure C-17 Information Provided by Jeff Parks on 09.30.19 174 of 350 Figure C-18 Information Provided by Jeff Parks on 09.30.19 175 of 350 Figure C-19 Information Provided by Jeff Parks on 09.30.19 176 of 350 Figure C-20 Information Provided by Jeff Parks on 09.30.19 177 of 350 Figure C-21Information Provided by Jeff Parks on 09.30.19178 of 350 APPENDIX D Results of Slope Stability Analysis Information Provided by Jeff Parks on 09.30.19 179 of 350 Spencer’s method of analysis was used for global stability analyses.The cross section evaluated for stability analyses is representative of section A1-A1’ shown on Figure 2 and is considered the most critical section for Pond 1.1.2.Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Pond 1 – Uphill – Drained ConditionStatic Global StabilityDiamond Valley Estates DevelopmentAuburn, WashingtonFigure D-1Information Provided by Jeff Parks on 09.30.19180 of 350 Spencer’s method of analysis was used for global stability analyses.The horizontal seismic coefficient, kh, used to evaluate pseudo-static (seismic) stability is based on ½ of the peak ground acceleration (PGA) for the design event (recurrence interval of 2475 years). The cross section evaluated for stability analyses is representative of section A1-A1’ shown on Figure 2 and is considered the most critical section for Pond 1.1.2.3.Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Pond 1 – Uphill – Drained ConditionSeismic Global StabilityDiamond Valley Estates DevelopmentAuburn, WashingtonFigure D-2Information Provided by Jeff Parks on 09.30.19181 of 350 Spencer’s method of analysis was used for global stability analyses.The cross section evaluated for stability analyses is representative of section A1-A1’ shown on Figure 2 and is considered the most critical section for Pond 1.1.2.Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Pond 1 – Downhill – Lower Slope Static Global StabilityDiamond Valley Estates DevelopmentAuburn, WashingtonFigure D-3Information Provided by Jeff Parks on 09.30.19182 of 350 Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Pond 1 – Downhill – Lower Slope Seismic Global StabilityDiamond Valley Estates DevelopmentAuburn, WashingtonFigure D-4Spencer’s method of analysis was used for global stability analyses.The horizontal seismic coefficient, kh, used to evaluate pseudo-static (seismic) stability is based on ½ of the peak ground acceleration (PGA) for the design event (recurrence interval of 2475 years). The cross section evaluated for stability analyses is representative of section A1-A1’ shown on Figure 2 and is considered the most critical section for Pond 1.1.2.3.Information Provided by Jeff Parks on 09.30.19183 of 350 Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Pond 1 –Downhill – Upper SlopeStatic Global StabilityDiamond Valley Estates DevelopmentAuburn, WashingtonFigure D-5Spencer’s method of analysis was used for global stability analyses.The cross section evaluated for stability analyses is representative of section A1-A1’ shown on Figure 2 and is considered the most critical section for Pond 1.1.2.Information Provided by Jeff Parks on 09.30.19184 of 350 Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Pond 1 –Downhill – Upper SlopeSeismic Global StabilityDiamond Valley Estates DevelopmentAuburn, WashingtonFigure D-6Spencer’s method of analysis was used for global stability analyses.The horizontal seismic coefficient, kh, used to evaluate pseudo-static (seismic) stability is based on ½ of the peak ground acceleration (PGA) for the design event (recurrence interval of 2475 years). The cross section evaluated for stability analyses is representative of section A1-A1’ shown on Figure 2 and is considered the most critical section for Pond 1.1.2.3.Information Provided by Jeff Parks on 09.30.19185 of 350 Spencer’s method of analysis was used for global stability analyses.The cross section evaluated for stability analyses is representative of section A2-A2’ shown on Figure 2 and is considered the most critical section for Pond 2.1.2.Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Pond 2 – Uphill – Drained ConditionStatic Global StabilityDiamond Valley Estates DevelopmentAuburn, WashingtonFigure D-7Information Provided by Jeff Parks on 09.30.19186 of 350 Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Pond 2 – Uphill – Drained ConditionSeismic Global StabilityDiamond Valley Estates DevelopmentAuburn, WashingtonFigure D-8Spencer’s method of analysis was used for global stability analyses.The horizontal seismic coefficient, kh, used to evaluate pseudo-static (seismic) stability is based on ½ of the peak ground acceleration (PGA) for the design event (recurrence interval of 2475 years). The cross section evaluated for stability analyses is representative of section A2-A2’ shown on Figure 2 and is considered the most critical section for Pond 2.1.2.3.Information Provided by Jeff Parks on 09.30.19187 of 350 Spencer’s method of analysis was used for global stability analyses.The cross section evaluated for stability analyses is representative of section A2-A2’ shown on Figure 2 and is considered the most critical section for Pond 2.1.2.Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Pond 2 – DownhillStatic Global StabilityDiamond Valley Estates DevelopmentAuburn, WashingtonFigure D-9Information Provided by Jeff Parks on 09.30.19188 of 350 Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Pond 2 – DownhillSeismic Global Stability Diamond Valley Estates DevelopmentAuburn, WashingtonFigure D-10Spencer’s method of analysis was used for global stability analyses.The horizontal seismic coefficient, kh, used to evaluate pseudo-static (seismic) stability is based on ½ of the peak ground acceleration (PGA) for the design event (recurrence interval of 2475 years). The cross section evaluated for stability analyses is representative of section A2-A2’ shown on Figure 2 and is considered the most critical section for Pond 2.1.2.3.Information Provided by Jeff Parks on 09.30.19189 of 350 Spencer’s method of analysis was used for global stability analyses.The cross section evaluated for stability analyses as approximately shown in Section A3-A3’ in Figure 2.1.2.Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Section A3-A3’Static Global StabilityDiamond Valley Estates DevelopmentAuburn, WashingtonFigure D-11Information Provided by Jeff Parks on 09.30.19190 of 350 Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Section A3-A3’Seismic Global Stability Diamond Valley Estates DevelopmentAuburn, WashingtonFigure D-12Spencer’s method of analysis was used for global stability analyses.The horizontal seismic coefficient, kh, used to evaluate pseudo-static (seismic) stability is based on ½ of the peak ground acceleration (PGA) for the design event (recurrence interval of 2475 years). The cross section evaluated for stability analyses as approximately shown in Section A3-A3’ in Figure 2.1.2.3.Information Provided by Jeff Parks on 09.30.19191 of 350 Spencer’s method of analysis was used for global stability analyses.The cross section evaluated for stability analyses as approximately shown in Section A4-A4’ in Figure 2.1.2.Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Section A4-A4’Static Global StabilityDiamond Valley Estates DevelopmentAuburn, WashingtonFigure D-13Information Provided by Jeff Parks on 09.30.19192 of 350 Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Section A4-A4’Seismic Global Stability Diamond Valley Estates DevelopmentAuburn, WashingtonFigure D-14Spencer’s method of analysis was used for global stability analyses.The horizontal seismic coefficient, kh, used to evaluate pseudo-static (seismic) stability is based on ½ of the peak ground acceleration (PGA) for the design event (recurrence interval of 2475 years). The cross section evaluated for stability analyses as approximately shown in Section A4-A4’ in Figure 2.1.2.3.Information Provided by Jeff Parks on 09.30.19193 of 350 Spencer’s method of analysis was used for global stability analyses.The cross section evaluated for stability analyses as approximately shown in Section A5-A5’ in Figure 2.1.2.Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Section A5-A5’ – Uphill Static Global StabilityDiamond Valley Estates DevelopmentAuburn, WashingtonFigure D-15Information Provided by Jeff Parks on 09.30.19194 of 350 Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Section A5-A5’ – Uphill Seismic Global Stability Diamond Valley Estates DevelopmentAuburn, WashingtonFigure D-16Spencer’s method of analysis was used for global stability analyses.The horizontal seismic coefficient, kh, used to evaluate pseudo-static (seismic) stability is based on ½ of the peak ground acceleration (PGA) for the design event (recurrence interval of 2475 years). The cross section evaluated for stability analyses as approximately shown in Section A5-A5’ in Figure 2.1.2.3.Information Provided by Jeff Parks on 09.30.19195 of 350 Spencer’s method of analysis was used for global stability analyses.The cross section evaluated for stability analyses as approximately shown in Section A5-A5’ in Figure 2.1.2.Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Section A5-A5’ – Downhill Static Global StabilityDiamond Valley Estates DevelopmentAuburn, WashingtonFigure D-17Information Provided by Jeff Parks on 09.30.19196 of 350 Notes:Reference: SLOPE/W, May 2014 Release, Version 8.13.0.9042Section A5-A5’ – Downhill Seismic Global Stability Diamond Valley Estates DevelopmentAuburn, WashingtonFigure D-18Spencer’s method of analysis was used for global stability analyses.The horizontal seismic coefficient, kh, used to evaluate pseudo-static (seismic) stability is based on ½ of the peak ground acceleration (PGA) for the design event (recurrence interval of 2475 years). The cross section evaluated for stability analyses as approximately shown in Section A5-A5’ in Figure 2.1.2.3.Information Provided by Jeff Parks on 09.30.19197 of 350 APPENDIX E Apex Slope Map Information Provided by Jeff Parks on 09.30.19 198 of 350 Figure E-1 Information Provided by Jeff Parks on 09.30.19 199 of 350 APPENDIX F Report Limitations and Guidelines for Use Information Provided by Jeff Parks on 09.30.19 200 of 350 APPENDIX F REPORT LIMITATIONS AND GUIDELINES FOR USE 1 This appendix provides information to help you manage your risks with respect to the use of this report. Geotechnical Services Are Performed for Specific Purposes, Persons and Projects This report has been prepared for the exclusive use of JDH Investment Group, LLC and other project team members for the Diamond Valley Estates development project. This report is not intended for use by others, and the information contained herein is not applicable to other sites. GeoEngineers structures our services to meet the specific needs of our clients. For example, a geotechnical or geologic study conducted for a civil engineer or architect may not fulfill the needs of a construction contractor or even another civil engineer or architect that are involved in the same project. Because each geotechnical or geologic study is unique, each geotechnical engineering or geologic report is unique, prepared solely for the specific client and project site. Our report is prepared for the exclusive use of our Client. No other party may rely on the product of our services unless we agree in advance to such reliance in writing. This is to provide our firm with reasonable protection against open-ended liability claims by third parties with whom there would otherwise be no contractual limits to their actions. Within the limitations of scope, schedule and budget, our services have been executed in accordance with our Agreement with the Client and generally accepted geotechnical practices in this area at the time this report was prepared. This report should not be applied for any purpose or project except the one originally contemplated. A Geotechnical Engineering or Geologic Report Is Based on a Unique Set of Project-specific Factors This report has been prepared for the Diamond Valley Estates development project in Auburn, Washington. GeoEngineers considered a number of unique, project-specific factors when establishing the scope of services for this project and report. Unless GeoEngineers specifically indicates otherwise, do not rely on this report if it was: ■ not prepared for you; ■ not prepared for your project; ■ not prepared for the specific site explored; or ■ completed before important project changes were made. For example, changes that can affect the applicability of this report include those that affect: ■ the function of the proposed structure; ■ elevation, configuration, location, orientation or weight of the proposed structure; ■ composition of the design team; or ■ project ownership. 1 Developed based on material provided by ASFE, Professional Firms Practicing in the Geosciences; www.asfe.org . Information Provided by Jeff Parks on 09.30.19 201 of 350 If important changes are made after the date of this report, GeoEngineers should be given the opportunity to review our interpretations and recommendations and provide written modifications or confirmation, as appropriate. Subsurface Conditions Can Change This geotechnical or geologic report is based on conditions that existed at the time the study was performed. The findings and conclusions of this report may be affected by the passage of time, by manmade events such as construction on or adjacent to the site, or by natural events such as floods, earthquakes, slope instability or groundwater fluctuations. Always contact GeoEngineers before applying a report to determine if it remains applicable. Most Geotechnical and Geologic Findings Are Professional Opinions Our interpretations of subsurface conditions are based on field observations from widely spaced sampling locations at the site. Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. GeoEngineers reviewed field and laboratory data and then applied our professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ, sometimes significantly, from those indicated in this report. Our report, conclusions and interpretations should not be construed as a warranty of the subsurface conditions. Geotechnical Engineering Report Recommendations Are Not Final Do not over-rely on the preliminary construction recommendations included in this report. These recommendations are not final, because they were developed principally from GeoEngineers’ professional judgment and opinion. GeoEngineers’ recommendations can be finalized only by observing actual subsurface conditions revealed during construction. GeoEngineers cannot assume responsibility or liability for this report's recommendations if we do not perform construction observation. Sufficient monitoring, testing and consultation by GeoEngineers should be provided during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether or not earthwork activities are completed in accordance with our recommendations. Retaining GeoEngineers for construction observation for this project is the most effective method of managing the risks associated with unanticipated conditions. A Geotechnical Engineering or Geologic Report Could Be Subject to Misinterpretation Misinterpretation of this report by other design team members can result in costly problems. You could lower that risk by having GeoEngineers confer with appropriate members of the design team after submitting the report. Also retain GeoEngineers to review pertinent elements of the design team's plans and specifications. Contractors can also misinterpret a geotechnical engineering or geologic report. Reduce that risk by having GeoEngineers participate in pre-bid and preconstruction conferences, and by providing construction observation. Do Not Redraw the Exploration Logs Geotechnical engineers and geologists prepare final boring and testing logs based upon their interpretation of field logs and laboratory data. To prevent errors or omissions, the logs included in a geotechnical engineering or geologic report should never be redrawn for inclusion in architectural or other design Information Provided by Jeff Parks on 09.30.19 202 of 350 drawings. Only photographic or electronic reproduction is acceptable, but recognize that separating logs from the report can elevate risk. Give Contractors a Complete Report and Guidance Some owners and design professionals believe they can make contractors liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give contractors the complete geotechnical engineering or geologic report, but preface it with a clearly written letter of transmittal. In that letter, advise contractors that the report was not prepared for purposes of bid development and that the report's accuracy is limited; encourage them to confer with GeoEngineers and/or to conduct additional study to obtain the specific types of information they need or prefer. A pre-bid conference can also be valuable. Be sure contractors have sufficient time to perform additional study. Only then might an owner be in a position to give contractors the best information available, while requiring them to at least share the financial responsibilities stemming from unanticipated conditions. Further, a contingency for unanticipated conditions should be included in your project budget and schedule. Contractors Are Responsible for Site Safety on Their Own Construction Projects Our geotechnical recommendations are not intended to direct the contractor’s procedures, methods, schedule or management of the work site. The contractor is solely responsible for job site safety and for managing construction operations to minimize risks to on-site personnel and to adjacent properties. Read These Provisions Closely Some clients, design professionals and contractors may not recognize that the geoscience practices (geotechnical engineering or geology) are far less exact than other engineering and natural science disciplines. This lack of understanding can create unrealistic expectations that could lead to disappointments, claims and disputes. GeoEngineers includes these explanatory “limitations” provisions in our reports to help reduce such risks. Please confer with GeoEngineers if you are unclear how these “Report Limitations and Guidelines for Use” apply to your project or site. Geotechnical, Geologic and Environmental Reports Should Not Be Interchanged The equipment, techniques and personnel used to perform an environmental study differ significantly from those used to perform a geotechnical or geologic study and vice versa. For that reason, a geotechnical engineering or geologic report does not usually relate any environmental findings, conclusions or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Similarly, environmental reports are not used to address geotechnical or geologic concerns regarding a specific project. Biological Pollutants GeoEngineers’ Scope of Work specifically excludes the investigation, detection, prevention or assessment of the presence of Biological Pollutants. Accordingly, this report does not include any interpretations, recommendations, findings, or conclusions regarding the detecting, assessing, preventing or abating of Biological Pollutants and no conclusions or inferences should be drawn regarding Biological Pollutants, as they may relate to this project. The term “Biological Pollutants” includes, but is not limited to, molds, fungi, spores, bacteria, and viruses, and/or any of their byproducts. Information Provided by Jeff Parks on 09.30.19 203 of 350 If Client desires these specialized services, they should be obtained from a consultant who offers services in this specialized field. Information Provided by Jeff Parks on 09.30.19 204 of 350 Have we delivered World Class Client Service? Please let us know by visiting www.geoengineers.com/feedback. Information Provided by Jeff Parks on 09.30.19 205 of 350 15365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 • (425) 449-4704 • FAX (425) 449-4711 Earth Solutions NW LLC Geotechnical Engineering, Construction Observation/Testing and Environmental Services September 15, 2023 ES-8849.01 MainVue WA, LLC 121 – 3rd Avenue Kirkland, Washington 98033 Attention: Vanessa Normandin Subject: Geotechnical Evaluation – Reasonable Use Exception Proposed Diamond Valley Estates 18XX Evergreen Way Southeast Auburn, Washington Greetings: As requested, Earth Solutions NW, LLC (ESNW) has prepared this evaluation letter regarding the reasonable use exception (RUE) currently being pursued for the subject project. Project Description Based on a review of the referenced site plan, various sloping areas that exceed a gradient of at least 40 percent have been delineated intermittently throughout the project area. Per Auburn Municipal Code (AMC) Chapter 16.10.020, such areas would be defined as Class IV landslide hazard areas, and application of standard buffers and development restrictions in such areas would be imposed. In general, site layout designs appear to have successfully incorporated buffer distances from the identified hazard areas. An exception occurs in the vicinity of Lot 70 and the adjacent portion of Road F, Tract G, and Tract I, where an isolated slope feature that meets the definition of a Class IV landslide hazard area is present. Based on our observations and review, this sloping feature only meets the AMC Class IV landslide designation on the basis of slope gradients (40 percent or greater). We understand the project has elected to pursue a RUE to allow for alteration of this slope feature and development of the proposed lots and access roadways as currently proposed. As such, the intent of this letter is to evaluate, from a geotechnical standpoint, the feasibility of the currently proposed modifications to the area. 206 of 350339 of 350 EXHIBIT 8 MainVue WA, LLC ES-8849.01 September 15, 2023 Page 2 Earth Solutions NW, LLC Subsurface Conditions Prior geotechnical evaluation and associated site investigation activities have been completed across the site and area of the proposed RUE by GeoEngineers, Inc. (GeoEngineers). As a supplement, ESNW completed a series of targeted test pit explorations in the subject area in August 2023. Based on a review of the referenced GeoEngineers report and the site conditions observed during our August 2023 fieldwork, the area of the proposed RUE is underlain by consolidated silty sand with gravel, silty gravel with sand, and poorly graded sand with variable fines content. Regardless of classification, native soils were primarily encountered and/or reported in a medium dense to dense condition near surface and became increasingly denser with depth. Groundwater seepage was exposed within the area toward the base of the slope feature during the August 2023 exploration; however, the observed groundwater was consistent with a discrete, transient seepage zone and not a surficial exposure of consistently emerging groundwater. Landslide Hazard and RUE Discussion Based on our review of the referenced grading plans, the area of focus will be subject to a combination of cut and fill activities. Within the boundaries of Lot 70, grade cuts of about 25 feet will be employed in conjunction with grade fills of about five feet. Within Road F, Tract G, and Tract I, grades fill of up to about 30 feet will be utilized. Similar grade alterations are also proposed in the immediately surrounding areas. Adjacent grade changes will be accommodated using gravity-style rockeries and/or 2H:1V permanent (engineered) slopes. Slope Stability Modeling A global slope stability analysis was completed using GeoStudio 2023 Slope/W software to evaluate slope stability characteristics of the pre-existing slope configuration (A-A’) and post- construction conditions (B-B’-B”) within the area of the proposed RUE. Different cross-section lines were chosen for each condition to provide a more accurate depiction of each modeled stability section. Soil strength parameters were selected based on our experience with similar deposits, the conditions encountered during our subsurface exploration, and the conditions reported in the referenced GeoEngineers report. Soil characterizations and “materials” in the models are intended to provide a general depiction of the soil characteristics and represent in-situ soil density and overall strength characterization rather than a specific soil classification. It is our opinion that the models present a general, comprehensive, and conservative depiction of the slope stability characteristics in each area and modeled condition. A piezometric line was modeled at the contact of the native soil materials and is applied to the underlying unit. Modeling the piezometric line in this matter conservatively assumes a static groundwater condition exists at the contact of the native soil materials, even though ESNW did not observe a static groundwater condition during the fieldwork. Groundwater expressions across the site are expected in the form of discrete, transient, and seasonally fluctuating seepage zones rather than as a static, uniformly established groundwater table. 207 of 350 MainVue WA, LLC ES-8849.01 September 15, 2023 Page 3 Earth Solutions NW, LLC Two models were produced and represent the pre-existing and post-construction configurations within the area of focus. Each model analyses two conditions: static and pseudo-static. For the pseudo-static condition, a horizontal seismic coefficient (Kh) of 0.3 was used in both configurations. This equates to approximately one-half of the site-modified peak ground acceleration (PGAM). For this evaluation, a minimum acceptable factor-of-safety (FOS) of 1.5 for a static condition and 1.1 for a pseudo-static condition were assumed. These values are consistent with local standards of practice and nearby jurisdictional requirements and are also consistent with the FOS values used in the GeoEngineers report. The critical slip surfaces (for each condition) are highlighted on the model outputs, and the calculated numerical FOS values are provided in the following table: Model Condition Minimum Calculated FOS Value Pre-Existing (A-A’) Static 1.52 Pseudo-static 0.85 Post-Construction (B-B’-B”) Static 1.51 Pseudo-static 1.11 As demonstrated through the post-construction models, the target minimum FOS values have been achieved for both static and pseudo-static conditions. Notably, the models predict that the pseudo-static condition will be improved in the post-construction condition compared with the pre- existing condition. On this basis, it is our opinion that the slope within the area of the proposed RUE will remain stable in the post-construction (graded) condition. Discussion From a geotechnical standpoint, ESNW takes no exception to the regrading of the slope feature in the area of focus. Slopes gradients that exceed 40 percent in the area are relatively limited in extent, with respect to the overall, larger slope feature. As such, this area is isolated and does not appear to require protection from regrading. As demonstrated in the previous section, retaining this area would not be beneficial for overall global stability in the post-construction condition, especially when considering loading from the design-level earthquake. Alteration of the area as proposed will allow the slope to be re-graded in an engineered manner and in accordance with local standards of practice. Structural fill placed that is placed along the slope will be keyed into the slope and compacted to the target relative density. Grade changes would be accommodated using permanent (engineered) fill slopes, retaining walls, rockeries, or some combination thereof. Furthermore, there is an opportunity to improve the long-term drainage characteristics within the area of focus if earthwork and grading activities are permitted to incur; such drainage improvements may include the use of interceptor drains, curtain drains, or similar designs. Construction of these elements will allow for more control of subsurface groundwater flows, which in turn will improve post-construction slope stability. At a minimum, the final civil plans will incorporate the drainage provisions outlined in point 36 of the Hearing Examiner’s conditions. 208 of 350 MainVue WA, LLC ES-8849.01 September 15, 2023 Page 4 Earth Solutions NW, LLC As is typical, an ESNW representative would be present during earthwork and grading activities to provide geotechnical consulting services, including construction observation, compaction testing, and making supplementary recommendations to maintain slope and soil stability, as necessary. We trust this letter meets your current needs. Should you have any questions, or if additional information is required, please call. Sincerely, EARTH SOLUTIONS NW, LLC Chase G. Halsen, L.G., L.E.G. Keven D. Hoffmann, P.E. Senior Project Geologist Associate Principal Engineer Attachments: Plate 1 – Slope Stability Cross-Sections Slope Stability Outputs cc: MainVue WA, LLC Attention: Allison Rothstein Barghausen Consulting Engineers, Inc. Attention: Tom Barghausen, P.E. Barry Talkington, P.E. Vicente Varas, P.E. Margi Fosdick References: RUE Grading Exhibit, prepared by Barghausen Consulting Engineers, Inc., Job No. 22817, dated September 8, 2023 Geotechnical Engineering and Geomorphology Services Report, prepared by GeoEngineers, Inc., File No. 21166-001-00, dated April 21, 2016 Chapter 16.10 of the Auburn Municipal Code 09/15/2023 09/15/2023 209 of 350 Plate Proj. No. Date Checked DrawnEarth Solutions NWLLCGeotechnical Engineering,ConstructionObservation/Testing and Environmental ServicesEarthSolutionsNWLLCEarthSolutionsNWLLCSlope Stability Cross-SectionsDiamond Valley EstatesAuburn, WashingtonNORTHNOTE: This plate may contain areas of color. ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. NOTE: The graphics shown on this plate are not intended for design purposes or precise scale measurements, but only to illustrate the approximate test locations relative to the approximate locations of existing and / or proposed site features. The information illustrated is largely based on data provided by the client at the time of our study. ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. Reference: Barghausen Consulting Engineering, Inc. 0 75 150 Scale in Feet 1"=150' MRS CGH 09/11/2023 8849.01 1 A’ A’ B B’ B” 210 of 350 1.52 Distance 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270 275 280 285 290 295 300 305 310 315 320 325 330 335 340 345 350 355 360 365 370 375 380 385 390 395 400 405 410 415Elevation330 335 340 345 350 355 360 365 370 375 380 385 390 395 400 405 410 415 420 425 430 435 440 445 450 Extent of Steep Slope Area Color Name Unit Weight (pcf) Effective Cohesion (psf) Effective Friction Angle (°) Piezometric Surface Dense to Very Desnse Silty Sand, Silty Gravel, or Outwash 125 150 36 1 Medium Dense Silty Sand/Silty Gravel 125 50 34 A-A' Existing Static 211 of 350 9/8/23, 12:27 PM Diamond Valley Estates RUE - Existing Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…1/11 Diamond Valley Estates RUE - Existing Static Report generated using GeoStudio 2022.1. Copyright © 2022 Bentley Systems, Incorporated. File Informa on File Version: 11.04 Created By: Chase Halsen Last Edited By: Chase Halsen Revision Number: 16 Date: 09/08/2023 Time: 12:26:00 PM Tool Version: 11.4.2.250 File Name: Exis ng.gsz Directory: C:\Users\chase.halsen\Desktop\Project Files\8849\8849.01\Slope Stability RUE\Exis ng Slope\ Last Solved Date: 09/08/2023 Last Solved Time: 12:26:08 PM Project Se ngs Unit System: U.S. Customary Units Analysis Se ngs Diamond Valley Estates RUE - Exis ng Sta c Descrip on: Exis ng Slope Condi on Kind: SLOPE/W Analysis Type: Morgenstern-Price Se ngs Side Func on Interslice force func on op on: Half-Sine PWP Condi ons from: Piezometric Surfaces Apply Phrea c Correc on: No Use Staged Rapid Drawdown: No Unit Weight of Water: 62.430189 pcf Slip Surface Direc on of movement: Le to Right Use Passive Mode: No Slip Surface Op on: Entry and Exit Cri cal slip surfaces saved: 1 Op mize Cri cal Slip Surface Loca on: No Tension Crack Op on: (none) Distribu on F of S Calcula on Op on: Constant Convergence Geometry Se ngs Minimum Slip Surface Depth: 0.1 212 of 350 9/8/23, 12:27 PM Diamond Valley Estates RUE - Existing Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…2/11 Number of Slices: 30 Factor of Safety Convergence Se ngs Maximum Number of Itera ons: 100 Tolerable difference in F of S: 0.001 Under-Relaxa on Criteria Ini al Rate: 1 Minimum Rate: 0.1 Rate Reduc on Factor: 0.65 Reduc on Frequency (itera ons): 50 Solu on Se ngs Search Method: Root Finder Tolerable difference between star ng and converged F of S: 3 Maximum itera ons to calculate converged lambda: 20 Max Absolute Lambda: 2 Materials Medium Dense Silty Sand/Silty Gravel Slope Stability Material Model: Mohr-Coulomb Unit Weight: 125 pcf Effec ve Cohesion: 50 psf Effec ve Fric on Angle: 34 ° Phi-B: 0 ° Dense to Very Desnse Silty Sand, Silty Gravel, or Outwash Slope Stability Material Model: Mohr-Coulomb Unit Weight: 125 pcf Effec ve Cohesion: 150 psf Effec ve Fric on Angle: 36 ° Phi-B: 0 ° Pore Water Pressure Piezometric Surface: 1 Slip Surface Entry and Exit Le Type: Range Le -Zone Le Coordinate: (0.80193, 439.85551) Le -Zone Right Coordinate: (176.75, 390) Le -Zone Increment: 50 Right Type: Range Right-Zone Le Coordinate: (178.99509, 389.06649) Right-Zone Right Coordinate: (406, 360) Right-Zone Increment: 50 Radius Increments: 4 Slip Surface Limits Le Coordinate: (0, 440) 213 of 350 9/8/23, 12:27 PM Diamond Valley Estates RUE - Existing Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…3/11 Right Coordinate: (407, 354) Piezometric Surfaces Piezometric Surface 1 Coordinates X Y Coordinate 1 0 433 Coordinate 2 10 431 Coordinate 3 22 430 Coordinate 4 33 428 Coordinate 5 45 426 Coordinate 6 72 423 Coordinate 7 103 413 Coordinate 8 128 403 Coordinate 9 153 393 Coordinate 10 177 383 Coordinate 11 201 373 Coordinate 12 226 364 Coordinate 13 233 362 Coordinate 14 239 360 Coordinate 15 246 358 Coordinate 16 280 356 Coordinate 17 327 354 Coordinate 18 407 354 Geometry Name: 2D Geometry Se ngs View: 2D Element Thickness: 1 Points X Y Point 1 0 440 Point 2 11.1 438 Point 3 22.2 436 Point 4 33.3 434 Point 5 44.4 432 Point 6 72.2 430 Point 7 102.7 420 Point 8 127.7 410 214 of 350 9/8/23, 12:27 PM Diamond Valley Estates RUE - Existing Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…4/11 Point 9 152.7 400 Point 10 176.75 390 Point 11 200.8 380 Point 12 227.2 370 Point 13 232.75 368 Point 14 238.3 366 Point 15 245.7 364 Point 16 279 362 Point 17 326.2 360 Point 18 406.75 360 Point 19 0 433 Point 20 10 431 Point 21 22 430 Point 22 33 428 Point 23 45 426 Point 24 72 423 Point 25 103 413 Point 26 128 403 Point 27 153 393 Point 28 177 383 Point 29 201 373 Point 30 226 364 Point 31 233 362 Point 32 239 360 Point 33 246 358 Point 34 280 356 Point 35 327 354 Point 36 407 354 Point 37 0 330 Point 38 407 330 Point 39 105.55 450 Point 40 200 450 Regions Material Points Region 1 Medium Dense Silty Sand/Silty Gravel 1,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,18,17,16,15,14,13,12,11,10, Region 2 Dense to Very Desnse Silty Sand, Silty 19,37,38,36,35,34,33,32,31,30,29,28,27,26,25,24,23,22,21,20 215 of 350 9/8/23, 12:27 PM Diamond Valley Estates RUE - Existing Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…5/11 Gravel, or Outwash Slip Results Slip Surfaces Analysed: 11445 of 13005 converged Current Slip Surface Slip Surface: 4,673 Factor of Safety: 1.52 Volume: 4,590.3328 ³ Weight: 573,791.6 lbf Resis ng Moment: 43,139,920 lbf· Ac va ng Moment: 28,294,071 lbf· Resis ng Force: 254,219.19 lbf Ac va ng Force: 166,721.75 lbf Slip Rank: 1 of 13,005 slip surfaces Exit: (248.53323, 363.82984) Entry: (66.343389, 430.42134) Radius: 155.66849 Center: (199.23815, 511.48712) Slip Slices X Y PWP Base Normal Stress Fric onal Strength Cohesive Strength Suc on Strength Base Materia Slice 1 68.719561 426.76091 0 psf 225.30347 psf 151.96911 psf 50 psf 0 psf Medium Dense Silty Sand/Silt Gravel Slice 2 71.547866 422.45204 37.345335 psf 482.6699 psf 323.54724 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 3 72.1 421.66207 81.513147 psf 556.36622 psf 345.00096 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 4 75.25 417.49709 278.09688 psf 867.18773 psf 427.99955 psf 150 psf 0 psf Dense to Very Desnse216 of 350 9/8/23, 12:27 PM Diamond Valley Estates RUE - Existing Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…6/11 Silty Sand, Silty Gravel, o Outwash Slice 5 81.35 409.93307 627.47312 psf 1,408.5513 psf 567.4865 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 6 87.45 403.24266 922.31059 psf 1,858.1556 psf 679.93121 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 7 93.55 397.27055 1,172.3041 psf 2,240.5305 psf 776.11192 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 8 99.65 391.90818 1,384.2314 psf 2,573.2097 psf 863.84331 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 9 102.85 389.24978 1,485.7512 psf 2,737.2896 psf 909.29585 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 10 106.0875 386.82446 1,557.0427 psf 2,860.6635 psf 947.13595 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash217 of 350 9/8/23, 12:27 PM Diamond Valley Estates RUE - Existing Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…7/11 Slice 11 112.2625 382.43654 1,676.7786 psf 3,086.9913 psf 1,024.5795 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 12 118.4375 378.48004 1,769.581 psf 3,292.3579 psf 1,106.3622 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 13 124.6125 374.91732 1,837.8002 psf 3,481.3016 psf 1,194.0737 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 14 127.85 373.15281 1,867.1116 psf 3,578.7554 psf 1,243.5821 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 15 131.0875 371.57153 1,884.9841 psf 3,664.6706 psf 1,293.018 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 16 137.2625 368.7273 1,908.3476 psf 3,826.3817 psf 1,393.5334 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 17 143.4375 366.2011 1,911.8556 psf 3,974.3779 psf 1,498.5101 psf 150 psf 0 psf Dense to Very Desnse Silty Sand,218 of 350 9/8/23, 12:27 PM Diamond Valley Estates RUE - Existing Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…8/11 Silty Gravel, o Outwash Slice 18 149.6125 363.97657 1,896.5309 psf 4,106.1018 psf 1,605.3472 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 19 152.85 362.89105 1,883.4534 psf 4,171.0394 psf 1,662.0285 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 20 155.96875 361.985 1,859.0477 psf 4,214.6288 psf 1,711.4298 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 21 161.90625 360.39226 1,804.0326 psf 4,284.9461 psf 1,802.4891 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 22 167.84375 359.04735 1,733.5459 psf 4,323.9267 psf 1,882.0218 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 23 173.78125 357.94374 1,647.9948 psf 4,324.3713 psf 1,944.5013 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 24 176.875 357.43339 1,599.3798 psf 4,311.3524 psf 1,970.3634 psf 150 psf 0 psf Dense to Very219 of 350 9/8/23, 12:27 PM Diamond Valley Estates RUE - Existing Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…9/11 Desnse Silty Sand, Silty Gravel, o Outwash Slice 25 179.975 357.04418 1,543.0391 psf 4,275.5676 psf 1,985.2981 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 26 185.925 356.41771 1,427.3752 psf 4,173.7139 psf 1,995.3319 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 27 191.875 356.0214 1,297.3423 psf 4,011.4569 psf 1,971.9197 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 28 197.825 355.85348 1,153.0504 psf 3,784.0716 psf 1,911.5488 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 29 200.9 355.82754 1,074.6815 psf 3,645.5309 psf 1,867.8315 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 30 204.125 355.92677 995.6508 psf 3,485.4805 psf 1,808.9672 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty 220 of 350 9/8/23, 12:27 PM Diamond Valley Estates RUE - Existing Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existi…10/11 Gravel, o Outwash Slice 31 210.375 356.24913 835.05793 psf 3,130.3391 psf 1,667.6194 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 32 216.625 356.82463 658.66172 psf 2,706.1089 psf 1,487.5574 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 33 222.875 357.6561 466.28454 psf 2,220.4203 psf 1,274.4542 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 34 226.6 358.24341 348.68292 psf 1,909.2233 psf 1,133.7989 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 35 229.975 358.90956 246.89412 psf 1,612.8645 psf 992.43558 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 36 232.875 359.49625 158.53914 psf 1,356.2433 psf 870.18303 psf 150 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 37 235.16977 360.0387 77.291223 psf 1,145.8261 psf 776.33605 psf 150 psf 0 psf Dense to Very Desnse221 of 350 9/8/23, 12:27 PM Diamond Valley Estates RUE - Existing Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existi…11/11 Silty Sand, Silty Gravel, o Outwash Slice 38 237.81977 360.67634 0 psf 861.4529 psf 581.05732 psf 50 psf 0 psf Medium Dense Silty Sand/Silt Gravel Slice 39 238.65 360.89079 0 psf 784.70747 psf 529.29187 psf 50 psf 0 psf Medium Dense Silty Sand/Silt Gravel Slice 40 242.35 361.94819 0 psf 463.93323 psf 312.92692 psf 50 psf 0 psf Medium Dense Silty Sand/Silt Gravel Slice 41 245.85 362.96107 0 psf 166.88633 psf 112.56625 psf 50 psf 0 psf Medium Dense Silty Sand/Silt Gravel Slice 42 247.26661 363.41899 0 psf 85.427124 psf 57.621323 psf 50 psf 0 psf Medium Dense Silty Sand/Silt Gravel 222 of 350 0.85 Distance 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270 275 280 285 290 295 300 305 310 315 320 325 330 335 340 345 350 355 360 365 370 375 380 385 390 395 400 405 410 415Elevation330 335 340 345 350 355 360 365 370 375 380 385 390 395 400 405 410 415 420 425 430 435 440 445 450 Extent of Steep Slope Area Color Name Unit Weight (pcf) Effective Cohesion (psf) Effective Friction Angle (°) Piezometric Surface Dense to Very Desnse Silty Sand, Silty Gravel, or Outwash 125 300 36 1 Medium Dense Silty Sand/Silty Gravel 125 100 34 A-A' Existing Pseudo-Static 223 of 350 9/8/23, 12:24 PM Diamond Valley Estates RUE - Existing Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…1/12 Diamond Valley Estates RUE - Existing Seismic Report generated using GeoStudio 2022.1. Copyright © 2022 Bentley Systems, Incorporated. File Informa on File Version: 11.04 Created By: Chase Halsen Last Edited By: Chase Halsen Revision Number: 15 Date: 09/08/2023 Time: 12:23:21 PM Tool Version: 11.4.2.250 File Name: Exis ng.gsz Directory: C:\Users\chase.halsen\Desktop\Project Files\8849\8849.01\Slope Stability RUE\Exis ng Slope\ Last Solved Date: 09/08/2023 Last Solved Time: 12:23:30 PM Project Se ngs Unit System: U.S. Customary Units Analysis Se ngs Diamond Valley Estates RUE - Exis ng Seismic Descrip on: Exis ng Slope Condi on Kind: SLOPE/W Analysis Type: Morgenstern-Price Se ngs Side Func on Interslice force func on op on: Half-Sine PWP Condi ons from: Piezometric Surfaces Apply Phrea c Correc on: No Use Staged Rapid Drawdown: No Unit Weight of Water: 62.430189 pcf Slip Surface Direc on of movement: Le to Right Use Passive Mode: No Slip Surface Op on: Entry and Exit Cri cal slip surfaces saved: 1 Op mize Cri cal Slip Surface Loca on: No Tension Crack Op on: (none) Distribu on F of S Calcula on Op on: Constant Convergence 224 of 350 9/8/23, 12:24 PM Diamond Valley Estates RUE - Existing Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…2/12 Geometry Se ngs Minimum Slip Surface Depth: 0.1 Number of Slices: 30 Factor of Safety Convergence Se ngs Maximum Number of Itera ons: 100 Tolerable difference in F of S: 0.001 Under-Relaxa on Criteria Ini al Rate: 1 Minimum Rate: 0.1 Rate Reduc on Factor: 0.65 Reduc on Frequency (itera ons): 50 Solu on Se ngs Search Method: Root Finder Tolerable difference between star ng and converged F of S: 3 Maximum itera ons to calculate converged lambda: 20 Max Absolute Lambda: 2 Materials Medium Dense Silty Sand/Silty Gravel Slope Stability Material Model: Mohr-Coulomb Unit Weight: 125 pcf Effec ve Cohesion: 100 psf Effec ve Fric on Angle: 34 ° Phi-B: 0 ° Dense to Very Desnse Silty Sand, Silty Gravel, or Outwash Slope Stability Material Model: Mohr-Coulomb Unit Weight: 125 pcf Effec ve Cohesion: 300 psf Effec ve Fric on Angle: 36 ° Phi-B: 0 ° Pore Water Pressure Piezometric Surface: 1 Slip Surface Entry and Exit Le Type: Range Le -Zone Le Coordinate: (0.63069, 439.88636) Le -Zone Right Coordinate: (176.75, 390) Le -Zone Increment: 50 Right Type: Range Right-Zone Le Coordinate: (178.62243, 389.22144) Right-Zone Right Coordinate: (406, 360) Right-Zone Increment: 50 Radius Increments: 4 225 of 350 9/8/23, 12:24 PM Diamond Valley Estates RUE - Existing Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…3/12 Slip Surface Limits Le Coordinate: (0, 440) Right Coordinate: (407, 354) Piezometric Surfaces Piezometric Surface 1 Coordinates X Y Coordinate 1 0 433 Coordinate 2 10 431 Coordinate 3 22 430 Coordinate 4 33 428 Coordinate 5 45 426 Coordinate 6 72 423 Coordinate 7 103 413 Coordinate 8 128 403 Coordinate 9 153 393 Coordinate 10 177 383 Coordinate 11 201 373 Coordinate 12 226 364 Coordinate 13 233 362 Coordinate 14 239 360 Coordinate 15 246 358 Coordinate 16 280 356 Coordinate 17 327 354 Coordinate 18 407 354 Seismic Coefficients Horz Seismic Coef.: 0.3 Geometry Name: 2D Geometry Se ngs View: 2D Element Thickness: 1 Points X Y Point 1 0 440 Point 2 11.1 438 226 of 350 9/8/23, 12:24 PM Diamond Valley Estates RUE - Existing Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…4/12 Point 3 22.2 436 Point 4 33.3 434 Point 5 44.4 432 Point 6 72.2 430 Point 7 102.7 420 Point 8 127.7 410 Point 9 152.7 400 Point 10 176.75 390 Point 11 200.8 380 Point 12 227.2 370 Point 13 232.75 368 Point 14 238.3 366 Point 15 245.7 364 Point 16 279 362 Point 17 326.2 360 Point 18 406.75 360 Point 19 0 433 Point 20 10 431 Point 21 22 430 Point 22 33 428 Point 23 45 426 Point 24 72 423 Point 25 103 413 Point 26 128 403 Point 27 153 393 Point 28 177 383 Point 29 201 373 Point 30 226 364 Point 31 233 362 Point 32 239 360 Point 33 246 358 Point 34 280 356 Point 35 327 354 Point 36 407 354 Point 37 0 330 Point 38 407 330 Point 39 105.55 450 Point 40 200 450 Regions Material Points Region 1 Medium Dense Silty Sand/Silty Gravel 1,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,18,17,16,15,14,13,12,11,10, 227 of 350 9/8/23, 12:24 PM Diamond Valley Estates RUE - Existing Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…5/12 Region 2 Dense to Very Desnse Silty Sand, Silty Gravel, or Outwash 19,37,38,36,35,34,33,32,31,30,29,28,27,26,25,24,23,22,21,20 Slip Results Slip Surfaces Analysed: 10119 of 13005 converged Current Slip Surface Slip Surface: 92 Factor of Safety: 0.85 Volume: 6,049.3584 ³ Weight: 756,169.8 lbf Resis ng Moment: 1.2273585e+08 lbf· Ac va ng Moment: 1.4498809e+08 lbf· Resis ng Force: 343,607.45 lbf Ac va ng Force: 405,661.3 lbf Slip Rank: 1 of 13,005 slip surfaces Exit: (257.5272, 363.28966) Entry: (0.63069038, 439.88636) Radius: 340.70362 Center: (218.57865, 701.7597) Slip Slices X Y PWP Base Normal Stress Fric onal Strength Cohesive Strength Suc on Strength Base Materia Slice 1 5.3153452 436.12531 0 psf 164.8903 psf 111.21991 psf 100 psf 0 psf Medium Dense Silty Sand/Silt Gravel Slice 2 10.55 431.94021 0 psf 416.07453 psf 280.64581 psf 100 psf 0 psf Medium Dense Silty Sand/Silt Gravel Slice 3 11.545756 431.1751 0 psf 461.36634 psf 311.19552 psf 100 psf 0 psf Medium Dense Silty Sand/Silt Gravel Slice 4 16.995756 427.16043 203.30936 psf 658.31432 psf 330.58045 psf 300 psf 0 psf Dense to Very 228 of 350 9/8/23, 12:24 PM Diamond Valley Estates RUE - Existing Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…6/12 Desnse Silty Sand, Silty Gravel, o Outwash Slice 5 22.1 423.41624 409.89048 psf 943.24439 psf 387.5043 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 6 27.6 419.68952 580.11991 psf 1,196.0637 psf 447.50937 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 7 33.15 415.93608 751.59209 psf 1,446.4565 psf 504.84851 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 8 38.85 412.39162 913.56464 psf 1,666.2471 psf 546.85583 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 9 44.7 408.76644 1,079.0161 psf 1,891.0502 psf 589.97735 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 10 49.5 406.01572 1,216.4071 psf 2,093.1488 psf 636.99017 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty 229 of 350 9/8/23, 12:24 PM Diamond Valley Estates RUE - Existing Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…7/12 Gravel, o Outwash Slice 11 58.5 401.04755 1,464.1407 psf 2,456.6516 psf 721.10132 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 12 67.5 396.42547 1,690.268 psf 2,797.4348 psf 804.40371 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 13 72.1 394.15126 1,799.0183 psf 2,969.9438 psf 850.7272 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 14 76.0125 392.34698 1,832.8669 psf 3,025.1201 psf 866.22263 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 15 83.6375 388.94569 1,891.652 psf 3,133.1485 psf 902.00001 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 16 91.2625 385.76498 1,936.6661 psf 3,246.2263 psf 951.45118 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 17 98.8875 382.79825 1,968.3215 psf 3,367.9545 psf 1,016.8929 psf 300 psf 0 psf Dense to Very Desnse230 of 350 9/8/23, 12:24 PM Diamond Valley Estates RUE - Existing Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…8/12 Silty Sand, Silty Gravel, o Outwash Slice 18 102.85 381.31343 1,981.2194 psf 3,435.8273 psf 1,056.8344 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 19 107.11667 379.83392 1,967.7628 psf 3,482.6605 psf 1,100.6377 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 20 115.35 377.09966 1,932.8601 psf 3,585.7152 psf 1,200.8695 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 21 123.58333 374.59541 1,883.5972 psf 3,698.2471 psf 1,318.4203 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 22 127.85 373.35865 1,854.2606 psf 3,760.7004 psf 1,385.1096 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 23 132.11667 372.23706 1,817.7344 psf 3,818.0019 psf 1,453.2794 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash231 of 350 9/8/23, 12:24 PM Diamond Valley Estates RUE - Existing Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existin…9/12 Slice 24 140.35 370.18566 1,740.2006 psf 3,926.2681 psf 1,588.271 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 25 148.58333 368.35016 1,649.1874 psf 4,013.9855 psf 1,718.1264 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 26 152.85 367.45642 1,598.436 psf 4,050.0918 psf 1,781.2322 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 27 156.95833 366.69896 1,539.0122 psf 4,059.0779 psf 1,830.9349 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 28 164.875 365.33912 1,417.9748 psf 4,044.2443 psf 1,908.0965 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 29 172.79167 364.17037 1,285.0068 psf 3,965.8209 psf 1,947.7255 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 30 176.875 363.61809 1,213.2679 psf 3,901.6777 psf 1,953.2441 psf 300 psf 0 psf Dense to Very Desnse Silty Sand,232 of 350 9/8/23, 12:24 PM Diamond Valley Estates RUE - Existing Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existi…10/12 Silty Gravel, o Outwash Slice 31 180.96667 363.16205 1,135.3038 psf 3,806.5154 psf 1,940.7489 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 32 188.9 362.37455 978.1012 psf 3,569.1649 psf 1,882.518 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 33 196.83333 361.77396 809.22932 psf 3,249.1916 psf 1,772.7363 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 34 200.9 361.51506 719.60813 psf 3,059.1411 psf 1,699.7702 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 35 205.16667 361.3457 633.93467 psf 2,847.8526 psf 1,608.5055 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 36 213.5 361.11942 460.77106 psf 2,390.6662 psf 1,402.1509 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 37 221.83333 361.09711 274.87351 psf 1,875.905 psf 1,163.2175 psf 300 psf 0 psf Dense to Very233 of 350 9/8/23, 12:24 PM Diamond Valley Estates RUE - Existing Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existi…11/12 Desnse Silty Sand, Silty Gravel, o Outwash Slice 38 226.6 361.15104 167.15853 psf 1,563.5288 psf 1,014.5224 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 39 229.975 361.25805 100.2775 psf 1,337.5698 psf 898.94547 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 40 232.875 361.35618 42.423541 psf 1,143.5786 psf 800.03596 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 41 233.84426 361.39929 19.933073 psf 1,078.4428 psf 769.05231 psf 300 psf 0 psf Dense to Very Desnse Silty Sand, Silty Gravel, o Outwash Slice 42 236.49426 361.53225 0 psf 824.7251 psf 556.2841 psf 100 psf 0 psf Medium Dense Silty Sand/Silt Gravel Slice 43 238.65 361.64799 0 psf 685.88964 psf 462.6384 psf 100 psf 0 psf Medium Dense Silty Sand/Silt Gravel Slice 44 242.35 361.90296 0 psf 486.62788 psf 328.23465 psf 100 psf 0 psf Medium Dense Silty 234 of 350 9/8/23, 12:24 PM Diamond Valley Estates RUE - Existing Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Existing Slope/Existing - Diamond Valley Estates RUE - Existi…12/12 Sand/Silt Gravel Slice 45 245.85 362.14932 0 psf 304.65964 psf 205.49552 psf 100 psf 0 psf Medium Dense Silty Sand/Silt Gravel Slice 46 251.7636 362.72551 0 psf 156.11366 psf 105.29999 psf 100 psf 0 psf Medium Dense Silty Sand/Silt Gravel 235 of 350 1.51 Distance 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270 275 280 285 290 295 300 305 310 315 320 325 330 335 340 345 350 355 360 365 370 375 380 385 390 395 400 405 410 415 420 425 430 435 440 445 450 455 460 465 470 475 480 485 490 495 500 505 510 515 520 525 530 535 540 545 550 555 560 565 570 575 580 585 590 595 600 605 610 615 620 625 630 635 640 645 650 655 660 665 670 675 680 685 690 695 700Elevation325 330 335 340 345 350 355 360 365 370 375 380 385 390 395 400 405 410 415 Extent of Steep Slope Area 250 psf Live Load B B'B'' Color Name Unit Weight (pcf) Effective Cohesion (psf) Effective Friction Angle (°) Piezometric Surface Dense to Very Dense Silty Sand, Silty Gravel, Outwash 125 150 36 1 Medium Dense Silty Sand and Silty Gravel 125 50 34 Structural Fill 125 0 34 Color Name Unit Weight (pcf) Effective Cohesion (psf) Effective Friction Angle (°) Piezometric Surface Dense to Very Dense Silty Sand, Silty Gravel, Outwash 125 150 36 1 Medium Dense Silty Sand and Silty Gravel 125 50 34 Structural Fill 125 0 34 Color Name Unit Weight (pcf) Effective Cohesion (psf) Effective Friction Angle (°) Piezometric Surface Dense to Very Dense Silty Sand, Silty Gravel, Outwash 125 150 36 1 Medium Dense Silty Sand and Silty Gravel 125 50 34 Structural Fill 125 0 34 B-B'-B" Post-Construction Static Condition 236 of 350 9/8/23, 12:31 PM Diamond Valley Estates RUE - Post Construction Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…1/7 Diamond Valley Estates RUE - Post Construction Static Report generated using GeoStudio 2022.1. Copyright © 2022 Bentley Systems, Incorporated. File Informa on File Version: 11.04 Created By: Chase Halsen Last Edited By: Chase Halsen Revision Number: 36 Date: 09/08/2023 Time: 12:30:50 PM Tool Version: 11.4.2.250 File Name: Post Construc on.gsz Directory: C:\Users\chase.halsen\Desktop\Project Files\8849\8849.01\Slope Stability RUE\Post Construc on\ Last Solved Date: 09/08/2023 Last Solved Time: 12:31:02 PM Project Se ngs Unit System: U.S. Customary Units Analysis Se ngs Diamond Valley Estates RUE - Post Construc on Sta c Kind: SLOPE/W Analysis Type: Morgenstern-Price Se ngs Side Func on Interslice force func on op on: Half-Sine PWP Condi ons from: Piezometric Surfaces Apply Phrea c Correc on: No Use Staged Rapid Drawdown: No Unit Weight of Water: 62.430189 pcf Slip Surface Direc on of movement: Le to Right Use Passive Mode: No Slip Surface Op on: Entry and Exit Cri cal slip surfaces saved: 1 Op mize Cri cal Slip Surface Loca on: No Tension Crack Op on: (none) Distribu on F of S Calcula on Op on: Constant Convergence 237 of 350 9/8/23, 12:31 PM Diamond Valley Estates RUE - Post Construction Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…2/7 Geometry Se ngs Minimum Slip Surface Depth: 3 Number of Slices: 30 Factor of Safety Convergence Se ngs Maximum Number of Itera ons: 100 Tolerable difference in F of S: 0.001 Under-Relaxa on Criteria Ini al Rate: 1 Minimum Rate: 0.1 Rate Reduc on Factor: 0.65 Reduc on Frequency (itera ons): 50 Solu on Se ngs Search Method: Root Finder Tolerable difference between star ng and converged F of S: 3 Maximum itera ons to calculate converged lambda: 20 Max Absolute Lambda: 2 Materials Structural Fill Slope Stability Material Model: Mohr-Coulomb Unit Weight: 125 pcf Effec ve Cohesion: 0 psf Effec ve Fric on Angle: 34 ° Phi-B: 0 ° Medium Dense Silty Sand and Silty Gravel Slope Stability Material Model: Mohr-Coulomb Unit Weight: 125 pcf Effec ve Cohesion: 50 psf Effec ve Fric on Angle: 34 ° Phi-B: 0 ° Dense to Very Dense Silty Sand, Silty Gravel, Outwash Slope Stability Material Model: Mohr-Coulomb Unit Weight: 125 pcf Effec ve Cohesion: 150 psf Effec ve Fric on Angle: 36 ° Phi-B: 0 ° Pore Water Pressure Piezometric Surface: 1 Slip Surface Entry and Exit Le Type: Range Le -Zone Le Coordinate: (0, 412) Le -Zone Right Coordinate: (395, 394) Le -Zone Increment: 50 Right Type: Range 238 of 350 9/8/23, 12:31 PM Diamond Valley Estates RUE - Post Construction Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…3/7 Right-Zone Le Coordinate: (405, 390) Right-Zone Right Coordinate: (637.5, 340.0991) Right-Zone Increment: 50 Radius Increments: 4 Slip Surface Limits Le Coordinate: (0, 412) Right Coordinate: (638.6, 340) Piezometric Surfaces Piezometric Surface 1 Coordinates X Y Coordinate 1 0 405 Coordinate 2 7.5 405 Coordinate 3 22.5 402.5 Coordinate 4 65 400 Coordinate 5 110 397.5 Coordinate 6 145 395 Coordinate 7 197.5 392.5 Coordinate 8 217.5 390 Coordinate 9 260 390 Coordinate 10 297.5 385 Coordinate 11 372.5 377.5 Coordinate 12 397.5 370 Coordinate 13 405 367.5 Coordinate 14 427.5 362.5 Coordinate 15 447.5 357.5 Coordinate 16 467.5 352.5 Coordinate 17 495 347.5 Coordinate 18 522.5 342.5 Coordinate 19 530 340 Coordinate 20 550 340 Coordinate 21 590 335 Coordinate 22 617.5 335 Coordinate 23 637.5 332.5 Surcharge Loads Surcharge Load 1 Surcharge (Unit Weight): 250 pcf 239 of 350 9/8/23, 12:31 PM Diamond Valley Estates RUE - Post Construction Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…4/7 Direc on: Ver cal Coordinates X Y 338.9 400 372.7 400 Geometry Name: 2D Geometry (2) Se ngs View: 2D Element Thickness: 1 Points X Y Point 1 0 412 Point 2 130.55 410 Point 3 141.65 408 Point 4 163.85 406 Point 5 183.25 404 Point 6 205.45 402 Point 7 216.55 398 Point 8 373 394 Point 9 397.2 394 Point 10 405 390 Point 11 426.3 380 Point 12 447.1 370 Point 13 467.9 360 Point 14 481.8 358 Point 15 495.7 356 Point 16 504 354 Point 17 512.3 352 Point 18 522 350 Point 19 530.3 348 Point 20 549.7 346 Point 21 588.6 344 Point 22 616.4 342 Point 23 638.6 340 Point 24 260.95 396 Point 25 373 384 Point 26 397.3 378 Point 27 405 374 Point 28 426.3 370 Point 29 447.1 364 240 of 350 9/8/23, 12:31 PM Diamond Valley Estates RUE - Post Construction Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…5/7 Point 30 0 405 Point 31 7.5 405 Point 32 22.5 402.5 Point 33 65 400 Point 34 110 397.5 Point 35 145 395 Point 36 197.5 392.5 Point 37 217.5 390 Point 38 260 390 Point 39 297.5 385 Point 40 372.5 377.5 Point 41 397.5 370 Point 42 405 367.5 Point 43 427.5 362.5 Point 44 447.5 357.5 Point 45 467.5 352.5 Point 46 495 347.5 Point 47 522.5 342.5 Point 48 530 340 Point 49 550 340 Point 50 590 335 Point 51 617.5 335 Point 52 637.5 332.5 Point 53 0 325 Point 54 637.5 325 Point 55 372.2 420 Point 56 405.5 415 Regions Material Points Region 1 Structural Fill 1,7,6,5,4,3,2 Region 2 Structural Fill 24,25,26,27,28,29,13,12,11,10,9,8 Region 3 Medium Dense Silty Sand and Silty Gravel 1,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,23,22,21,20, Region 4 Dense to Very Dense Silty Sand, Silty Gravel, Outwash 30,53,54,52,51,50,49,48,47,46,45,44,43,42,41,40,39,38,37,36,35,34,33,32,31 241 of 350 9/8/23, 12:31 PM Diamond Valley Estates RUE - Post Construction Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…6/7 Slip Results Slip Surfaces Analysed: 12453 of 13005 converged Current Slip Surface Slip Surface: 12,822 Factor of Safety: 1.51 Volume: 391.26981 ³ Weight: 48,908.726 lbf Resis ng Moment: 3,504,660.2 lbf· Ac va ng Moment: 2,325,643.6 lbf· Resis ng Force: 27,485.308 lbf Ac va ng Force: 18,235.241 lbf Slip Rank: 1 of 13,005 slip surfaces Exit: (465.85981, 360.98086) Entry: (395, 394) Radius: 114.94681 Center: (476.0871, 475.47179) Slip Slices X Y PWP Base Normal Stress Fric onal Strength Cohesive Strength Suc on Strength Base Material Slice 1 396.1 392.93399 0 psf 91.12535 psf 61.464824 psf 0 psf 0 psf Structural Fill Slice 2 397.35 391.72696 0 psf 187.3378 psf 126.36094 psf 0 psf 0 psf Structural Fill Slice 3 398.75 390.44892 0 psf 233.04418 psf 157.19029 psf 0 psf 0 psf Structural Fill Slice 4 401.25 388.23954 0 psf 308.85347 psf 208.3243 psf 0 psf 0 psf Structural Fill Slice 5 403.75 386.15479 0 psf 375.21915 psf 253.08851 psf 0 psf 0 psf Structural Fill Slice 6 406.18333 384.23577 0 psf 436.97918 psf 294.74618 psf 0 psf 0 psf Structural Fill Slice 7 408.55 382.46979 0 psf 495.7684 psf 334.40001 psf 0 psf 0 psf Structural Fill Slice 8 410.91667 380.79592 0 psf 549.83747 psf 370.87005 psf 0 psf 0 psf Structural Fill Slice 9 413.28333 379.20933 0 psf 599.87117 psf 404.61821 psf 0 psf 0 psf Structural Fill Slice 10 415.65 377.70578 0 psf 646.31348 psf 435.94395 psf 0 psf 0 psf Structural Fill Slice 11 418.01667 376.28149 0 psf 689.38079 psf 464.99321 psf 0 psf 0 psf Structural Fill Slice 12 420.38333 374.93309 0 psf 729.07017 psf 491.76404 psf 0 psf 0 psf Structural Fill Slice 13 422.75 373.65755 0 psf 765.16535 psf 516.11055 psf 0 psf 0 psf Structural Fill 242 of 350 9/8/23, 12:31 PM Diamond Valley Estates RUE - Post Construction Static file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…7/7 Slice 14 425.11667 372.45217 0 psf 797.24331 psf 537.7474 psf 0 psf 0 psf Structural Fill Slice 15 426.9 371.58262 0 psf 818.31671 psf 551.96159 psf 0 psf 0 psf Structural Fill Slice 16 428.725 370.74455 0 psf 834.06678 psf 562.58515 psf 0 psf 0 psf Structural Fill Slice 17 431.175 369.67055 0 psf 850.39056 psf 573.59567 psf 0 psf 0 psf Structural Fill Slice 18 433.625 368.66354 0 psf 859.12411 psf 579.48653 psf 0 psf 0 psf Structural Fill Slice 19 436.075 367.72164 0 psf 859.07761 psf 579.45516 psf 0 psf 0 psf Structural Fill Slice 20 438.525 366.84316 0 psf 849.07058 psf 572.70534 psf 0 psf 0 psf Structural Fill Slice 21 440.975 366.02657 0 psf 828.03141 psf 558.51424 psf 0 psf 0 psf Structural Fill Slice 22 443.425 365.2705 0 psf 795.10638 psf 536.30602 psf 0 psf 0 psf Structural Fill Slice 23 445.875 364.5737 0 psf 749.76657 psf 505.72394 psf 0 psf 0 psf Structural Fill Slice 24 447.3 364.18823 0 psf 718.59442 psf 484.69806 psf 0 psf 0 psf Structural Fill Slice 25 448.91646 363.79188 0 psf 675.75193 psf 455.80043 psf 0 psf 0 psf Structural Fill Slice 26 451.74938 363.14038 0 psf 590.48478 psf 398.28701 psf 0 psf 0 psf Structural Fill Slice 27 454.38095 362.59982 0 psf 498.52839 psf 336.26164 psf 0 psf 0 psf Structural Fill Slice 28 456.87903 362.14868 0 psf 400.87408 psf 270.39298 psf 0 psf 0 psf Structural Fill Slice 29 459.44497 361.74348 0 psf 292.5256 psf 197.31101 psf 0 psf 0 psf Structural Fill Slice 30 462.0109 361.39743 0 psf 178.06695 psf 120.10767 psf 0 psf 0 psf Structural Fill Slice 31 464.57684 361.10999 0 psf 59.602179 psf 40.202177 psf 0 psf 0 psf Structural Fill 243 of 350 1.11 Distance 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270 275 280 285 290 295 300 305 310 315 320 325 330 335 340 345 350 355 360 365 370 375 380 385 390 395 400 405 410 415 420 425 430 435 440 445 450 455 460 465 470 475 480 485 490 495 500 505 510 515 520 525 530 535 540 545 550 555 560 565 570 575 580 585 590 595 600 605 610 615 620 625 630 635 640 645 650 655 660 665 670 675 680 685 690 695 700Elevation325 330 335 340 345 350 355 360 365 370 375 380 385 390 395 400 405 410 415 Extent of Steep Slope Area 250 psf Live Load B B'B'' Color Name Unit Weight (pcf) Effective Cohesion (psf) Effective Friction Angle (°) Piezometric Surface Dense to Very Dense Silty Sand, Silty Gravel, Outwash 125 300 36 1 Medium Dense Silty Sand and Silty Gravel 125 100 34 Structural Fill 125 200 34 Color Name Unit Weight (pcf) Effective Cohesion (psf) Effective Friction Angle (°) Piezometric Surface Dense to Very Dense Silty Sand, Silty Gravel, Outwash 125 300 36 1 Medium Dense Silty Sand and Silty Gravel 125 100 34 Structural Fill 125 200 34 Color Name Unit Weight (pcf) Effective Cohesion (psf) Effective Friction Angle (°) Piezometric Surface Dense to Very Dense Silty Sand, Silty Gravel, Outwash 125 300 36 1 Medium Dense Silty Sand and Silty Gravel 125 100 34 Structural Fill 125 200 34 B-B'-B" Post-Construction Pseudo-Static Condition 244 of 350 9/8/23, 11:46 AM Diamond Valley Estates RUE - Post Construction Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…1/9 Diamond Valley Estates RUE - Post Construction Seismic Report generated using GeoStudio 2022.1. Copyright © 2022 Bentley Systems, Incorporated. File Informa on File Version: 11.04 Created By: Chase Halsen Last Edited By: Chase Halsen Revision Number: 33 Date: 09/08/2023 Time: 11:45:12 AM Tool Version: 11.4.2.250 File Name: Post Construc on.gsz Directory: C:\Users\chase.halsen\Desktop\Project Files\8849\8849.01\Slope Stability RUE\Post Construc on\ Last Solved Date: 09/08/2023 Last Solved Time: 11:45:44 AM Project Se ngs Unit System: U.S. Customary Units Analysis Se ngs Diamond Valley Estates RUE - Post Construc on Seismic Kind: SLOPE/W Analysis Type: Morgenstern-Price Se ngs Side Func on Interslice force func on op on: Half-Sine PWP Condi ons from: Piezometric Surfaces Apply Phrea c Correc on: No Use Staged Rapid Drawdown: No Unit Weight of Water: 62.430189 pcf Slip Surface Direc on of movement: Le to Right Use Passive Mode: No Slip Surface Op on: Entry and Exit Cri cal slip surfaces saved: 1 Op mize Cri cal Slip Surface Loca on: No Tension Crack Op on: (none) Distribu on F of S Calcula on Op on: Constant Convergence 245 of 350 9/8/23, 11:46 AM Diamond Valley Estates RUE - Post Construction Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…2/9 Geometry Se ngs Minimum Slip Surface Depth: 3 Number of Slices: 30 Factor of Safety Convergence Se ngs Maximum Number of Itera ons: 100 Tolerable difference in F of S: 0.001 Under-Relaxa on Criteria Ini al Rate: 1 Minimum Rate: 0.1 Rate Reduc on Factor: 0.65 Reduc on Frequency (itera ons): 50 Solu on Se ngs Search Method: Root Finder Tolerable difference between star ng and converged F of S: 3 Maximum itera ons to calculate converged lambda: 20 Max Absolute Lambda: 2 Materials Structural Fill Slope Stability Material Model: Mohr-Coulomb Unit Weight: 125 pcf Effec ve Cohesion: 200 psf Effec ve Fric on Angle: 34 ° Phi-B: 0 ° Medium Dense Silty Sand and Silty Gravel Slope Stability Material Model: Mohr-Coulomb Unit Weight: 125 pcf Effec ve Cohesion: 100 psf Effec ve Fric on Angle: 34 ° Phi-B: 0 ° Dense to Very Dense Silty Sand, Silty Gravel, Outwash Slope Stability Material Model: Mohr-Coulomb Unit Weight: 125 pcf Effec ve Cohesion: 300 psf Effec ve Fric on Angle: 36 ° Phi-B: 0 ° Pore Water Pressure Piezometric Surface: 1 Slip Surface Entry and Exit Le Type: Range Le -Zone Le Coordinate: (2.5, 411.9617) Le -Zone Right Coordinate: (395, 394) Le -Zone Increment: 50 Right Type: Range 246 of 350 9/8/23, 11:46 AM Diamond Valley Estates RUE - Post Construction Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…3/9 Right-Zone Le Coordinate: (404.67435, 390.167) Right-Zone Right Coordinate: (638.6, 340) Right-Zone Increment: 50 Radius Increments: 4 Slip Surface Limits Le Coordinate: (0, 412) Right Coordinate: (638.6, 340) Piezometric Surfaces Piezometric Surface 1 Coordinates X Y Coordinate 1 0 405 Coordinate 2 7.5 405 Coordinate 3 22.5 402.5 Coordinate 4 65 400 Coordinate 5 110 397.5 Coordinate 6 145 395 Coordinate 7 197.5 392.5 Coordinate 8 217.5 390 Coordinate 9 260 390 Coordinate 10 297.5 385 Coordinate 11 372.5 377.5 Coordinate 12 397.5 370 Coordinate 13 405 367.5 Coordinate 14 427.5 362.5 Coordinate 15 447.5 357.5 Coordinate 16 467.5 352.5 Coordinate 17 495 347.5 Coordinate 18 522.5 342.5 Coordinate 19 530 340 Coordinate 20 550 340 Coordinate 21 590 335 Coordinate 22 617.5 335 Coordinate 23 637.5 332.5 Seismic Coefficients Horz Seismic Coef.: 0.3 247 of 350 9/8/23, 11:46 AM Diamond Valley Estates RUE - Post Construction Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…4/9 Surcharge Loads Surcharge Load 1 Surcharge (Unit Weight): 250 pcf Direc on: Ver cal Coordinates X Y 338.9 400 372.7 400 Geometry Name: 2D Geometry (2) Se ngs View: 2D Element Thickness: 1 Points X Y Point 1 0 412 Point 2 130.55 410 Point 3 141.65 408 Point 4 163.85 406 Point 5 183.25 404 Point 6 205.45 402 Point 7 216.55 398 Point 8 373 394 Point 9 397.2 394 Point 10 405 390 Point 11 426.3 380 Point 12 447.1 370 Point 13 467.9 360 Point 14 481.8 358 Point 15 495.7 356 Point 16 504 354 Point 17 512.3 352 Point 18 522 350 Point 19 530.3 348 Point 20 549.7 346 Point 21 588.6 344 Point 22 616.4 342 Point 23 638.6 340 Point 24 260.95 396 Point 25 373 384 248 of 350 9/8/23, 11:46 AM Diamond Valley Estates RUE - Post Construction Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…5/9 Point 26 397.3 378 Point 27 405 374 Point 28 426.3 370 Point 29 447.1 364 Point 30 0 405 Point 31 7.5 405 Point 32 22.5 402.5 Point 33 65 400 Point 34 110 397.5 Point 35 145 395 Point 36 197.5 392.5 Point 37 217.5 390 Point 38 260 390 Point 39 297.5 385 Point 40 372.5 377.5 Point 41 397.5 370 Point 42 405 367.5 Point 43 427.5 362.5 Point 44 447.5 357.5 Point 45 467.5 352.5 Point 46 495 347.5 Point 47 522.5 342.5 Point 48 530 340 Point 49 550 340 Point 50 590 335 Point 51 617.5 335 Point 52 637.5 332.5 Point 53 0 325 Point 54 637.5 325 Point 55 372.2 420 Point 56 405.5 415 Regions Material Points Region 1 Structural Fill 1,7,6,5,4,3,2 Region 2 Structural Fill 24,25,26,27,28,29,13,12,11,10,9,8 Region 3 Medium Dense Silty Sand and Silty Gravel 1,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,23,22,21,20, Region 4 Dense to Very Dense Silty 30,53,54,52,51,50,49,48,47,46,45,44,43,42,41,40,39,38,37,36,35,34,33,32,31 249 of 350 9/8/23, 11:46 AM Diamond Valley Estates RUE - Post Construction Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…6/9 Sand, Silty Gravel, Outwash Slip Results Slip Surfaces Analysed: 10093 of 13005 converged Current Slip Surface Slip Surface: 12,572 Factor of Safety: 1.11 Volume: 640.23743 ³ Weight: 80,029.679 lbf Resis ng Moment: 7,315,315.9 lbf· Ac va ng Moment: 6,613,890.9 lbf· Resis ng Force: 52,604.169 lbf Ac va ng Force: 47,526.133 lbf Slip Rank: 1 of 13,005 slip surfaces Exit: (470.50071, 359.6258) Entry: (387.12524, 394) Radius: 126.63049 Center: (473.91553, 486.21024) Slip Slices X Y PWP Base Normal Stress Fric onal Strength Cohesive Strength Suc on Strength Base Material Slice 1 388.38458 392.84631 0 psf -5.7660194 psf -3.8892292 psf 200 psf 0 psf Structural Fill Slice 2 390.90327 390.59922 0 psf 184.01652 psf 124.12071 psf 200 psf 0 psf Structural Fill Slice 3 393.42196 388.46871 0 psf 351.65856 psf 237.1967 psf 200 psf 0 psf Structural Fill Slice 4 395.94065 386.44729 0 psf 501.70867 psf 338.40677 psf 200 psf 0 psf Structural Fill Slice 5 397.35 385.34911 0 psf 575.2026 psf 387.97905 psf 200 psf 0 psf Structural Fill Slice 6 398.75 384.31317 0 psf 595.97614 psf 401.99098 psf 200 psf 0 psf Structural Fill Slice 7 401.25 382.51514 0 psf 631.05874 psf 425.65449 psf 200 psf 0 psf Structural Fill Slice 8 403.75 380.80708 0 psf 662.77876 psf 447.04992 psf 200 psf 0 psf Structural Fill Slice 9 406.38618 379.10103 0 psf 698.23664 psf 470.96656 psf 200 psf 0 psf Structural Fill Slice 10 409.15853 377.4021 0 psf 738.78615 psf 498.31755 psf 200 psf 0 psf Structural Fill 250 of 350 9/8/23, 11:46 AM Diamond Valley Estates RUE - Post Construction Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…7/9 Slice 11 411.93088 375.79893 0 psf 779.61344 psf 525.8559 psf 200 psf 0 psf Structural Fill Slice 12 414.70323 374.28738 0 psf 821.82019 psf 554.32472 psf 200 psf 0 psf Structural Fill Slice 13 417.47558 372.86379 0 psf 866.10309 psf 584.19391 psf 200 psf 0 psf Structural Fill Slice 14 420.24793 371.52489 0 psf 912.66023 psf 615.5971 psf 200 psf 0 psf Structural Fill Slice 15 422.80058 370.36155 0 psf 918.47749 psf 619.52089 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 16 425.13353 369.3599 0 psf 954.48248 psf 643.80656 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 17 426.9 368.63301 0 psf 982.36946 psf 662.61657 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 18 428.9 367.86058 0 psf 1,011.7565 psf 682.43837 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 19 431.7 366.833 0 psf 1,051.7859 psf 709.43853 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 20 434.5 365.87933 0 psf 1,086.2232 psf 732.66679 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 21 437.3 364.99784 0 psf 1,110.6155 psf 749.11959 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 22 440.1 364.18696 0 psf 1,120.0827 psf 755.5053 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 23 442.9 363.44529 0 psf 1,109.8655 psf 748.61371 psf 100 psf 0 psf Medium Dense Silty Sand 251 of 350 9/8/23, 11:46 AM Diamond Valley Estates RUE - Post Construction Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…8/9 and Silty Gravel Slice 24 445.7 362.77158 0 psf 1,075.997 psf 725.76911 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 25 447.3 362.40857 0 psf 1,046.5267 psf 705.89121 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 26 448.92857 362.07801 0 psf 1,004.3486 psf 677.44169 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 27 451.78571 361.53687 0 psf 911.50345 psf 614.81684 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 28 454.64286 361.0633 0 psf 793.02769 psf 534.90393 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 29 457.5 360.65652 0 psf 652.97895 psf 440.43987 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 30 460.35714 360.31589 0 psf 496.71557 psf 335.03888 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 31 463.21429 360.04087 0 psf 329.98731 psf 222.57925 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 32 466.07143 359.83103 0 psf 158.0741 psf 106.62233 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel Slice 33 467.7 359.73254 0 psf 59.820447 psf 40.349401 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel 252 of 350 9/8/23, 11:46 AM Diamond Valley Estates RUE - Post Construction Seismic file:///C:/Users/chase.halsen/Desktop/Project Files/8849/8849.01/Slope Stability RUE/Post Construction/Post Construction - Diamond Valley Estates R…9/9 Slice 34 469.20035 359.67425 0 psf 22.435454 psf 15.132905 psf 100 psf 0 psf Medium Dense Silty Sand and Silty Gravel 253 of 350 70648552535457566563696667687177788379818082848687888955454443394041427273747576133133135137187186187132134TRACT H1366261SCALE: 1"=50'NOT FORCONSTRUCTIONCONSTRUCTION NOTESRUE GRADING EXHIBITFor:Title: 22817 1 MAINVUE WA LLC 121 3RD AVENUE KIRKLAND, WA 98033 RUE GRADING EXHIBIT FOR 1 DIAMOND VALLEY ESTATESCITY OF AUBURN, KING COUNTY, WASHINGTONDIAMOND VALLEY ESTATESA PORTION OF THE S.W. 1/4 OF SECTION 32, TOWNSHIP 21 NORTH, RANGE 5 EAST, W.M.FORDETENTIONVAULT ATRACT ITRACT GROAD FROAD BROAD CWETLAND 1NOTE:SHADED AREA REPRESENTS THEEXTENT OF THE STEEP SLOPEAREA TO BE ALTERED254 of 350EXHIBIT 9 255 of 350 EXHIBIT 10 Preliminary Plat Diamond Valley Estates PLT14-0006 I.GENERAL INFORMATION: Application Date: April 21, 2014, Resubmitted April 27, July 14, August 15, September 16, and November 8, 2016 Applicant(s)/ Blake Haddock Property Owner(s): JDH Investment Group Corporation P.O. Box 2952 Lake Havasu City, AZ 86405 Agent: James E. Kirkebo III (“Tres”), Principal/Project Manager Apex Engineering, PLLC 2601 S 35th ST, Suite 200 Tacoma WA 98409 Related Project Nos: Diamond Valley Estates, PLT14-0006 Formerly, Park Ridge, MIS08-0017 Formerly, Kersey III, Division 3, SEP00-0040 Project Description: To subdivide four parcels totaling approximately 79.45 acres into 200 single- family residential lots and ten tracts and associated clearing, grading and construction of stormwater facilities, public streets, utilities, and landscaping. The project site contains wetlands, streams and geologic hazard areas. Proposed Location: The project site is located on the north and south sides of Evergreen Way SE, between Quincy and Udall AV SE, within the SW ¼ of Section 32-21-05, W.M. Parcel Numbers: King County Assessor’s Parcel No's: 322105-9010, -9011, -9030 & -9037 Subject Property and Adjacent Property Land Use designation, Zoning Classification and Current Land Use: Comprehensive Plan Designation Zoning Classification Current Land Use Site Single-Family Residential / Vacant R-5 Residential (5 dwelling units (du)/acre (ac)) Vacant except for developed right-of- way of Evergreen Way SE North Single-Family Residential R-5 Residential (5 du/ac)Vacant South Unincorporated Pierce County City of Auburn – Potential Annexation Area Unincorporated Pierce County - Moderate Density Single Family Residential Zone Single-family residential / Vacant Moderate Density Single Family Residential (MSF) Single Family Residential West Single-Family Residential R7 Residential (7 du/ac) Single-family residential East Single-Family Residential R5 Residential (5 du/ac) and Planned Unit Development (under former code section, now repealed) Single-family residential 256 of 350 EXHIBIT 11 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 2 List of Exhibits Exhibit 1: Staff Report Exhibit 2: Vicinity Map showing adjacent zoning classifications. Exhibit 3: Completed Preliminary Plat Application, PLT14-0006. Exhibit 4: Preliminary Plat Conceptual Storm Drainage Report for Diamond Valley Estates, Apex Engineering PLLC, March 26, 2014, Rev. December 8, 2014. Exhibit 5: Title Report, Fidelity National Title of Washington, April 10, 2014. Exhibit 6: Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016. Exhibit 7: Diamond Valley Estates Landscape Plan, Sheets L1 and L2, Bradley Design Group, Inc., March 19, 2014, Rev. July 11, 2016. Exhibit 8: Draft Environmental Impact Statement (DEIS) for Kersey III Preliminary Plat and Appendices , City of Auburn, July 1, 2004. (This document due to size, is available on the City’s Secured File Transfer Site (SFTP) and upon request) Exhibit 9: Final Environmental Impact Statement (FEIS) for Kersey III Preliminary Plat , pages i through vii (Submitted with Application), City of Auburn, February 11, 2005. This document due to size, is available on the City’s Secured File Transfer Site (SFTP) and upon request) Exhibit 10: Pre-Application Meeting Summary, Park Ridge Development Agreement Proposal (Kersey 3, Div. 3), City of Auburn, August 27, 2008. Exhibit 11: School Access Analysis Diamond Valley Estates, Apex Engineering PLLC, undated. Exhibit 12: Letter: Diamond Valley Estates response to City Comments (2011), Jeffrey P.K. Hee P.E., Transportation Solutions Inc.(TSI), March 14, 2014. Exhibit 13: Wetland (and Streams) Assessment, Diamond Valley Estates Auburn WA, Raedeke Associates Inc. April 8, 2014. Exhibit 14: Geotechnical Engineering Services and Geomorphology Services, Diamond Valley Estates Development, Auburn WA, GeoEngineers, April 18, 2014., Rev. November 16, 2015, Rev. April 21, 2016. Exhibit 15: Comment Responses for Preliminary Plat of Diamond Valley Estates (Letter), Geoffrey P. Sherwin, Apex Engineering PLLC, April 27, 2016. Exhibit 16: Diamond Valley Estates Plat Modif. Request (Narrative Request for 3 Engineering Design Standard deviations), Apex Engineering PLLC, undated. Exhibit 17: Staff Recommendation on Modification to Plat Standards for Relief from Engineering Design Standards, City of Auburn, January 18, 2017. Exhibit 18: Technical Memorandum - Diamond Valley Estates Preliminary Plat (Wetlands)– Response to Feb. 3, 2016 City of Auburn Comments, Raedeke Associates Inc. April 19, 2016. Exhibit 19: Comment Responses for Preliminary Plat of Diamond Valley Estates (Letter), Geoffrey P. Sherwin, Apex Engineering PLLC, July 6, 2016. Exhibit 20: Comment Responses for Preliminary Plat of Diamond Valley Estates (Letter), Geoffrey P. Sherwin, Apex Engineering PLLC, July 7, 2016. Exhibit 21: Diamond Valley Estates Modification of Plat Standards (Narrative for Request from Minimum Residential Density), James E. Kirkebo III, Apex Engineering PLLC, Received July 14, 2016. Exhibit 22: Diamond Valley Estates U-Turn Exhibit with Bus Added, Sheet 1, Apex Engineering PLLC, Rec. August 15, 2016. Exhibit 23: Diamond Valley Estates Road B at Road F/C Mini Roundabout Design Report, Transportation Solutions Inc., November 8, 2016. Exhibit 24: Notice of Application for Park Ridge Development Agreement. Exhibit 25: Invitation for Developer Hosted Open House Required for Development Agreement Projects (Park Ridge). Exhibit 26: Completed Application for Critical Areas Variance (Class IV, Landslide Hazard), VAR16-0001. Exhibit 27: Variance Slope Exhibit (COLOR). Exhibit 28: Combined Notice of Application & Notice of Hearing – Diamond Valley Estates PLT14-0006. Exhibit 29: Affidavits of Mailing, Posting, & Publication, PLT14-0006 (three documents). 257 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 3 Map showing adjacent zoning designations: II. SEPA STATUS: A Determination of Significance (DS) was issued for the Project as part of a previous larger development proposal. A Draft Environmental Impact Statement was issued by the City of Auburn on July 1, 2004 (File No. SEP00-0004). After observance of a 45-day public comment period, a Final Environmental Impact Statement was issued on February 11, 2005. The document was titled: “Final Environmental Impact Statement for the Kersey III Preliminary Plat”. The proposed Action evaluated in the Environmental Impact Statement involves the development of a low-density preliminary plat of 481 dwelling units or a higher density 700 dwelling unit development on an approximately 170-acre site located in the southerly portion of the City of Auburn. The 700-unit alternative would be developed under the city’s Planned Unit Development (PUD) regulations, while a portion of the 481-unit alternative would require PUD approval. The project consisted of seven (7) undeveloped forested parcels. The project will be governed by, among other regulations, the City of Auburn zoning and subdivision ordinances. Open space and sensitive areas would be provided or protected as required by the City of Auburn sensitive area regulations. Certain portions of the site will not be developed due to steep slopes, wetlands, and power line corridors. The project’s proposed construction consisted of three (3) divisions and six (6) phases (2 divisions for each phase). The subject property was identified as “Kersey III, Division 3”. The proposal included approximately 620,000 cubic yards of earthwork, which was expected to 258 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 4 remain on the development site. The proposal required the on-site and off-site installation of new public facilities to serve the development, to include water, storm sewer and sanitary sewer lines. On-site storm facilities include wet ponds for detention and water quality treatment. The proposal also required the dedication of land for use as a public park. The proposal required the dedication and construction of approximately four (4) miles of new public rights-of-way to serve the development and provide internal circulation. The improvements include internal streets and a new arterial connection from existing terminus of Evergreen Way SE (off-site to the west) to Kersey Way SE. A public meeting on the environmental impact statement process was held on July 28, 2004 from 4:00 to 8:00 pm at the Lakeland Community Center. III. FINDINGS OF FACT: General/Background/History 1. An Environmental Impact Statement (EIS) was required for the Kersey Ill preliminary plat proposal, originally proposed in 2000. The Draft and Final EIS addressed the subject property, plus the adjoining two properties to the east that are now developed (Exhibits 8 & 9). Two total development alternatives were analyzed in the EIS documents; one for 481 total dwelling units, the other for 700 dwelling units covering for all properties. As noted, the current proposal involves 200 dwelling units (lots) for approximately one third of the area addressed in the EIS. The other two-thirds was developed with approximately 373 dwelling units. The Draft EIS was issued on July 1, 2004, with the Final EIS being issued on February 11, 2005. A public meeting on the environmental impact statement process was held on July 28, 2004 from 4:00 to 8:00 pm at the Lakeland Community Center. 2. The first two eastern divisions or subdivisions of the project evaluated in the EIS submitted applications and proceeded through the approval process and were rezoned to Planned Unit Development (PUD) and each received preliminary and final plat approvals, construction was completed and homes were subsequently constructed. 3. The subject property as the third division (Kersey III, Division 3) located to the west did not submit applications to the City and was not rezoned to PUD prior to the City’s repealing this former code section (ACC 18.69, Planned Unit Developments) by the city’s adoption of Ordinance No. 5991 (April 17, 2006). 259 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 5 4. For these earlier two divisions of this larger project, the applicants, Wayne Jones of Lakeridge Development and Joyce & Peter Bowles, requested a change in zoning to the Planned Unit Development (PUD), approval of a Planned Unit Development (PUD), and preliminary plat approval for Kersey Ill, Divisions 1 & 2. Kersey Ill Division 1 was a 169-lot single-family residential subdivision of a 50.85-acre site located west of Kersey Way SE at approx. 53rd St. SE. Kersey Ill Division 2, was a proposed 204-lot single-family residential subdivision located on an adjacent 38.46-acre parcel abutting the western boundary of Division 1. Although owned separately, the two projects were processed concurrently and agreed to share common open space and recreational amenities. According to the staff report prepared for the proposal, Division 1 lot sizes averaged 5,032 sq. ft. in size, with an average lot width of 50 ft. The smallest lot was proposed to be 3,985 sq. ft. in area. The overall project density was 3.32 dwelling units per acre. Since the project was proposed as a PUD, smaller lot sizes than typical zoning standards are allowed. The minimum standards for lots within a single-family density PUD were contained in ACC 18.69.070 (subsequently repealed). The Division 2 lot sizes averaged 5,127 sq. ft. in area, with an average lot width of 40 ft. The smallest lot was proposed as 3,999 sq. ft. in area. Overall project density is 5.30 dwelling units per acre. Collectively, the two projects consist of 373 dwelling units at an overall density of 4.17 units per acre. Temporary cul-de-sacs and utility services were provided to ensure that each phase can stand-alone pursuant to Auburn City Code (ACC) Section 18.69.110. 5. Recommended mitigation measures for all 3 phases are included starting on Page 9 of the Final EIS. Per the mitigation measures of the Kersey Ill Final EIS, no homes may be constructed until Evergreen Way SE is extended from its current eastern terminus within Lakeland Hills east to Kersey Way at 53rd ST. SE. The Applicants entered into an agreement with each other and the owner of property to the west (the future Kersey Ill, Division 3) regarding the construction of Evergreen Way SE. A traffic signal was required to be installed at the 53rd ST. SE intersection and the 53rd ST. SE approach will need to be reconfigured to eliminate the current angular intersection. The extension of Evergreen Way SE and the traffic signal at the intersection of 53rd St SE were both completed prior to the completion of the Kersey III, Divisions 1 and 2 developments. The EIS recommended development of this area will also require the construction of a temporary sewage pump station to the north along Kersey Way SE, to be removed when sanitary sewer lines were extended southward along Kersey Way from Oravetz Road SE. Those sanitary sewer lines were constructed prior to the development of the first two phases of the Kersey III project, so the construction of the temporary pump station is unnecessary. The EIS recommended City of Auburn water service will be provided by connecting to existing water lines within the Lakeland Hills development (to the west). Numerous off-site improvements will need to be made to the water system, including the construction of a booster pump station at the Terrace View Development along East Valley Highway (a.k.a. A ST SW). This booster pump station was constructed in 2010. The western 300 feet of the Division 1 site is encumbered by the Bonneville Power Administration's (BPA’s) electrical transmission lines and easements. This area was partially developed as an active and passive open space amenity, including a linear trail and open natural areas. Separate active recreational facilities are provided directly adjacent to this area, but not within the power line easement. Active amenities include a sport court and playground equipment. Internal pathways and one public road crossing provide access to these facilities. The open space and amenities benefit residents of both Divisions. 260 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 6 6.On October 6, 2008 the City Council adopted Ordinance No. 6187 repealing the City’s code provisions for development agreements. Consistent with the city’s practice and law, the Ordinance became effective five days after publication or October 14, 2008. 7.On October 13, 2008, the then Applicant, Jeff Mann of Apex Engineering PLLC, on behalf of Todd Duty, agent for Property Owner, Betty Frye, filed an application (File No. MIS08-0017) for a Development Agreement under the city’s code provisions for development agreements (ACC 14.21) before this code section was repealed by Ordinance No. 6187 on October 14, 2008 (the effective date). The development agreement proposal was for subdivision of approximately 81 acres into 256 lots; mostly for detached single family homes and approximately 40 townhomes. The residential development was titled “Park Ridge”. While the project was considered vested to the process under the city code section for a negotiated development agreement, the latest Applicant has submitted a preliminary plat application under the standards in effect at the time of this application. 8.A Notice of Application (NOA) for the development proposal (Park Ridge) was issued November 24, 2008. The notices were posted at the Site, mailed to adjacent property owners according to County Tax Assessor records within a minimum of 300 feet of the Site, and published in The Seattle Times, newspaper (Exhibit 24). 9.Up through 2010 the City staff reviewed several resubmittals of the development agreement for the purpose of sufficient information for the City Council’s consideration and to serve as a basis for a staff recommendation. In 2012, the City granted several extensions for resubmittal of information for application processing, under ACC 14.06.010(G). 10.The King County Tax Assessor website records show the property was purchased by JDH Investment Group, Applicant, on May 31, 2013. Information/Description of Preliminary Plat Proposal 11.On April 21, 2014 a Preliminary Plat Application (File No PLT14-0006) was filed by James E. (“Tres”) Kirkebo III of Apex Engineering, PLLC on behalf of Blake Haddock of JDH Investment Group Corporation for the subdivision of an approximately 79.45 acres (“Site”) into 202 single- family residential lots and eleven (11) tracts under the R5, Residential five dwelling units per acre zoning standard (Exhibit 3). 12.The City’s plat submittal requirements specify that the Applicant must identify any plat phasing that is proposed. No such phasing is identified with the application. As a result, the City has not considered nor evaluated any phasing of the construction or final platting to consider how each phase could function independently for preliminary plat conditions. As a result, no phasing is allowed based on the current proposal. Any change to include phasing would likely require the specific preparation of civil plans based on the phasing and may require a “major adjustment” of an approved preliminary plat (ACC 17.10.100(B)) to ensure that preliminary plat conditions are re-reviewed for coordination with any phasing. 13.The Applicant has not proposed a gated community. Gated communities can be authorized when identified along with the preliminary plat per ACC 18.31.140. 14.On April 27, 2016, an Application for a modification of plat standards (deviation) pursuant to ACC Chapter 17.18 (Modification of Standards and Specifications) was submitted for relief from the City Engineering Design Standards (manual) for the following issues: Deviation Request #1: Allow four horizontal curves that are less than the minimum radius of 333 feet for a “local residential” classified street. 261 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 7 Deviation Request #2: Allow the use of walls on more than three sides in the storm ponds and not require 25% of the pond perimeter to be a vegetated soil slope not steeper than 3:1. The project’s relationship to each of the requests for Modification of Standards is addressed in separate sections of this Report, below 15. On May 5, 2016 a Variance Application was submitted for a variance from the city’s critical area requirements that prohibit alteration of Class IV Landslide Hazard Areas (ACC 16.10.100(E)(2) (Exhibits 26 & 27). The plat proposes grading and alteration of a Class IV Landslide Hazard Area within the southwest corner of the Plat for Tract A (Open Space) and the adjacent Lots 7 & 8, and grading and alteration of Class IV Landslide Hazard Areas near the south-central portion of the Plat for “Road F”, Lots 71 - 73, and “Tract I” (a storm drainage tract). The location of these Class IV Landslide Hazard Areas (slopes 40% or greater) are shown on “Critical Slope Exhibit”, Sheet 26 of Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016. The project’s relationship to the variance criteria are addressed in a separate section, below. 16. The Application was revised and resubmitted on July 14, 2016 in response to City comments. The project was changed to include 200 lots and ten tracts, among other revisions. 17. Also on July 14, 2016, the application was modified to include a letter request for a modification of plat standards for relief from the minimum density standard of the zoning code (Exhibit 21). The application was also revised to include an additional modification of the plat standards for relief from the Engineering Design Standards as follows (Exhibit 16): Deviation Request #3: Allow a modified street section for portions of Road B and Road C, northerly of the intersection with Road F. The intent of the modified street section design is to allow ingress/egress of emergency vehicles and non-emergency vehicles without interference from each other. The project’s relationship to each of the requests for Modification of Standards is addressed in separate sections of this Report, below. 18. The Site is roughly rectangular in shape; the longer axis is aligned north-south measuring approximately 2,698.94 feet by approximately 1,328.7 feet east-west. 19. The project site is located on the north and south sides of Evergreen Way SE, between Quincy and Udall AV SE, within the SW ¼ of Section 32-21-05, W.M. The four parcels comprising the property are identified by King County Assessor’s Parcel No's: 322105-9010, -9011, -9030 & - 9037. 20. A description of the current site conditions is found in the: Wetland Assessment, Diamond Valley Estates Auburn WA, Raedeke Associates Inc. April 8, 2014 (Exhibit 13), as follows: “3.1 GENERAL PROPERTY DESCRIPTION The Diamond Valley Estates project site is located within the Bowman Creek basin on the north slope of the Lake Tapps plateau, south of the White River. The site consists of a series of north to south oriented ridges and ravines that slope down to the north towards Kersey Way (Figure 2). Elevations of the overall site range from approximately 220 feet above sea level at the northeastern corner of the property to about 570 feet above sea level at the southwest property corner. The site consists of moderately to steeply sloping terrain.” 262 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 8 “At the time of our 2013 site investigation, the property was undeveloped and dominated by deciduous, mixed and coniferous forests. In addition to the forested areas, a small area of pasture is located in the north-central portion of the site.” “The majority of the property appears to have been logged during the 1930's to 1940's based on the 18-inch to 24-inch diameter at breast height of the majority of the coniferous trees on the site. Several areas within the northeastern portion of the site appear to have been logged more recently due to the relatively smaller diameters of trees found growing in these areas. Several old logging roads and trails extend through the property.” 21. The Site is currently mainly vacant forested hillside generally sloping to the NE. The southern portion of the Site contains an east-west segment of Evergreen Way SE and associated temporary stormwater pond for the road. The construction of Evergreen Way SE was required as a prerequisite to any development of the Kersey III Preliminary Plats projects, as identified in the EIS documents. This constructed roadway was completed and dedicated to the City in 2009. 22. The Comprehensive Land Use designation for the Property is “Single-Family Residential”. The Site is also part of the Lakeland Hills Special Planning Area, adopted by Resolution No. 1851 in April 1988 as a sub-area or neighborhood plan of the City’s Comprehensive Plan. The Plan was developed after preparation of a Draft and Final EIS in 1981. An excerpt from the Plan describes its main purpose: “The Lakeland Hills Plan applies the policy guidance contained in the comprehensive plan to the area known as Lakeland Hills. Plan policies are discussed as they relate to three main subject areas: land use; natural environment, parks and open space; and facilities. This Plan is consistent with and implements the key mitigation measures related to land use described in the Environmental Impact Statement prepared for the Lakeland Hills development. “ 23. The Site is zoned R5 Residential, Five (5) Dwelling Units per Acre (ACC 18.07). The stated purpose of the R5, Residential zone is: “. . .to create a living environment of optimum standards for single-family dwellings. It is further intended to achieve development densities of four to five dwelling units per net acre. This zone will provide for the development of single-family detached dwellings and for such accessory uses as are related, incidental and not detrimental to the single-family residential environment.” 24. The site is approximately 79.44 acres or 3,460,427 square feet (SF) as specified by the application materials and King County Assessor’s website data. Auburn City Code (ACC) 18.02.065 guides the density calculations for development. City regulations provide for a minimum and base (maximum) density for the R5 Residential zone of 4 and 5 dwelling units per net acre, respectively. As depicted on Sheet 1 of the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016 (Exhibit 6). The gross acreage less deductions yields a “net acreage” of 2,801,098 sq. ft. (or 64.30 acres). This “net acreage” yields a base (maximum) density of 322 dwelling units for the Site. This net acreage also yields a minimum density of 238 dwelling units. The Project proposes 200 dwelling units (lots); a 16% reduction from, and less than the minimum number of dwelling units required by code. Relief from the minimum density standard must be granted to authorize the plat, as proposed. 263 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 9 25. Per ACC 12.64A, (Required Public Improvements), the following public right-of-way (ROW) edication and construction of public right-of-way improvements are required for the subdivision: • Dedication of ROW and construction of improvements for “Road B” to a “boulevard- modified” Residential Collector standard between Evergreen Way SE and G ST SE based on standards specified in the City of Auburn Engineering Design Standards. A modification of plat standards (deviation) is requested to the modified boulevard section in order to provide a wider divided access as an alternative to providing a second access. • Dedication of ROW and construction of improvements for “Road B” to a modified “Residential Collector” standard between Evergreen Way SE and the intersection of “Roads B, C and F” based on standards specified in the City of Auburn Engineering Design Standards. A modification of plat standards (deviation) is required. • Dedication of ROW and construction of improvements for “Road B” to a modified “Local Residential” standard between the intersection of “Roads B, C and F” and the northern property line based on standards specified in the City of Auburn Engineering Design Standards. A modification of plat standards (deviation) is required. • Dedication of ROW and construction of improvements for “Road C” to a modified “Local Residential” standard between intersection of “Roads B, C and F” and the northern property line based on standards specified in the City of Auburn Engineering Design Standards. A modification of plat standards (deviation) is required. • Dedication of ROW and construction of improvements for “Road E” to the “Local Residential” standard specified in the City of Auburn Engineering Design Standards. • Dedication of ROW and construction of improvements for “Road F” to the “Local Residential” standard specified in the City of Auburn Engineering Design Standards. • Dedication of ROW and construction of improvements for “Road G” to the “Local Residential” standard specified in the City of Auburn Engineering Design Standards. • (There is no identified “Road A” or “Road D”). 26. The extension of “Road F” at the location proposed at the east boundary of the Site is necessary to serve the adjacent approved preliminary plat of Forest Glen (City File No. PLT06- 0008). The civil plans for this Forest Glen plat are currently under review by the City. The second public street connection is needed to serve the future lots within this adjacent plat. 27. “Road B” is proposed to end in a temporary cul-de-sac at the midpoint of the north boundary of the Site since it is foreseeable to be extended in the future to serve future off-site development to the north. There are no active proposals or applications for off-site development to the north. 28. “Road C” is not depicted as extending to the north boundary of the Site and having a temporary cul-de-sac since grades in this vicinity and off-site to the north appear to preclude off-site future extension of this public roadway. There are no active proposals or applications for off-site development to the north. 29. The plat proposes use of shared driveways between adjacent lots at selected locations within the plat. Shared driveways are needed to address corner lots and where individual driveways would be located too close to street intersections and where a center median in Road C limits driveway locations. The shared driveways are shown on Sheet 20, “Conceptual Grading Plan”, of the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016 (Exhibit 6). Further changes may be identified during civil plan review process. 30. Water service to serve the plat will be provided by the City of Auburn. Connections will be required to be constructed by the applicant to the existing 12-inch water lines in Evergreen 264 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 10 Way SE with main line extensions within the rights-of-way and publicly dedicated tracts or easements in the plat. 31. The water system shall be designed to meet City of Auburn Design Standards (Chapter 7 – Water Facilities) and the City’s 2015 Comprehensive Water Plan (Chapter 3 - Policies and Criteria). For each pressure zone, the distribution system pressures shall be 35 pounds per sq. inch (psi) minimum and 80 psi maximum. 32. Due to considerable elevation changes across the site, the site will require separation into three water pressure zones regulated by pressure reducing stations to be constructed by the applicant, generally, as follows: 630 zone – Lots 1 – 54 565 zone – Lots 55 - 84 and 133 - 200 500 zone – Lots 85 - 132 33. Sanitary sewer service to serve the plat will be provided by the City of Auburn. Sewer connection will be required to be constructed by the applicant from the terminus of the sewer line existing near the NE corner of the site that was previously constructed with the earlier divisions of the Kersey III, Preliminary Plats. The construction of public main extensions will be required westward along the north property boundary of the plat to “Road B” and within the right-of-way through the plat. Where the public mains are not coincident with street rights-of- way, publicly dedicated tracts or easements are required to meet city standards. 34. Fire hydrants and mains capable of providing the required fire flow shall be provided per City of Auburn Engineering Design Standards and the International Fire Code (IFC). Fire hydrant locations shall be approved by the Fire Marshal. 35. The requirements of ACC 13.48 Storm Drainage Utility, ACC 15.74 Land Clearing, Filling, and Grading, and the City’s Surface Water Management Manual (SWMM) are applicable to the Site and Project. 36. Traffic, fire, park, and school impacts are mitigated through the payment of impact fees in effect at the time of Building Permit issuance for each lot or deferred per ACC 19.02.070(E) (School Impact fees); 19.04.040(H) (Transportation Impact Fees); 19.06.040(F) (Fire Impact Fees); and 19.08.030(G) (Parks Impact Fees). 37. The plat includes ten proposed tracts totaling approximately 30 acres as depicted on Sheet 1 of the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016, as follows: • TRACT "A” = 85,844+/- SF. Open Space, To Homeowner's Association (H.O.A.) • TRACT “B” = 3,226+/- SF. Open Space / Utility Tract, To City Of Auburn • TRACT "C" = 1,182+/- SF. Shared Access Facility, Lots 24 & 25, To Lots 24 & 25 • TRACT "D" = 3,800+/- SF. Shared Access Facility, Lots 27 - 29, To Lots 27 - 29 • TRACT "E" = 109,371+/- SF, Open Space, To H.O.A. • TRACT "F" = 4,481+/- SF. Open Space / Utility Tract, To City Of Auburn • TRACT "G" = 255,551+/- SF. Open Space, To H.O.A. • TRACT "H" = 5,170+/- SF. Open Space, To H.O.A. • TRACT "I" = 834,497+/- SF. Open Space, Wetlands, Streams, Buffers ▪ Wetlands = 28,220+/- SF. To H.O.A. ▪ Streams = 8,391+/- SF. To H.O.A. ▪ Wetland And Stream Buffers = 207,650+/- SF. To H.O.A. ▪ Storm Facility/Open Space = 590,236+/- SF. To City Of Auburn (Storm Facilities To Be In Tracts Dedicated To The City, Tract Limits To Be Finalized During FAC Process) 265 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 11 •TRACT “J” = 3,175+/- SF. Shared Access Facility, Lots 157 & 158, And Utility Tract, To Lots 157 & 158 As noted on this Sheet 1, the tracts are anticipated to be further revised and clarified in purpose, provisions and location through the civil plan review and approval process. Revisions may include creation of new tracts or revision of the size of proposed tracts to align with ownership and maintenance responsibilities. For example, sight distance tracts may be created to be maintained by the future Homeowner’s Association (HOA), or two new storm tracts limited to the area of Storm Pond 1 and 2 (to be owned by the City) shall be created from what is currently shown as Tract “I”, which shall be owned and maintained by the HOA. 38.Critical areas on the Site and in the vicinity of the Site include geologic hazard areas, wildlife habitat areas, wetlands, and streams. Initial information on these are found in the Kersey III Preliminary Plat Draft Environmental Impact Statement, July 2004, City of Auburn. More site- specific information related to the proposal includes a geotechnical report and a wetland report (including streams) prepared to accompany the preliminary plat application. 39.Information on the site’s streams is found in the: Wetland Assessment, Diamond Valley Estates Auburn WA, Raedeke Associates Inc., April 8, 2014. It identifies the site contains two streams; Streams A and B. Both streams flow northward to the NE corner of the Site. The streams join off-site to the east to become Stream AB within a steeply-sided ravine that is partly within the northeast corner of the project site. Stream AB flows northwesterly to re-enter the Site briefly before leaving the Site again at the north boundary. Stream AB flows northward from the project site for approximately 1,200 feet to the south side of Kersey Way SE. Stream AB passes beneath Kersey Way SE through a concrete pipe and flows approximately 100 feet further to the north before reaching Bowman Creek. Water was present within Streams A, B, and AB at the time of Raedeke’s May 2002 site investigations; however, water was not present within any on-site portion of the stream channels during their September 2002 or July/August 2013 site investigations. This could be attributable to the late season investigation. 40.Information on the site’s wetlands is found in the: The Wetland Assessment, Diamond Valley Estates Auburn WA, Raedeke Associates Inc. April 8, 2014. It identifies the site contains approximately 0.7 acres (30,420 square feet) of wetlands based on current site conditions. Six wetlands occur within the project site (Wetlands A, B, C, and D, and Wetlands 1 and 2). Three of the identified wetlands (Wetlands A, 1, and 2) are associated with Stream A within the eastern portion of the property. One of the wetlands (Wetland D) is hydrologically isolated within a closed depression in the central portion of the project site. Two of the wetlands are on slopes (Wetlands B and C) within the northeast portion of the site. Wetland C is also isolated with no surface connection to on-site streams. Several areas adjacent to existing wetlands that had been previously delineated as potential wetland extensions and described in the EIS documents no longer meet criteria to be determined wetlands based on guidance provided by the regional supplement to the U.S. Army Corps of Engineers (COE) wetland delineation manual for the Western Mountains, Valleys, and Coast Region (COE 2010). This guidance was not available at the time of the original delineations in 2000 by DBM Engineers Inc. (DBM) and boundary verifications by Raedeke Associates, Inc. in 2002. This guidance was used to determine that several areas abutting Wetland A and Wetland B and within the Stream A channel just upstream and downstream of Wetland A were not wetland because they no longer met hydric soil criteria. One new wetland area was delineated (Wetland 2) since the preparation of the EIS documents. This area is within the Stream A channel, approximately 80 feet downstream from Wetland A. The area had not been delineated at the time of the 2000 DBM investigation or during the 2002 boundary verification by Raedeke Associates, Inc. Although at that time the 266 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 12 area had hydric soils and evidence of seasonal inundation, it was not vegetated and thus, did not meet criteria for dominance by hydrophytic vegetation as is required to be determined a wetland by the COE wetland delineation manual (Environmental Laboratory 1987). At the time of current investigation, the area was dominated by yellow skunk cabbage (Lysichiton americanus, OBL) and therefore met criteria for dominance by hydrophytes. Tables 1 and 2 provide a summary of all wetlands and streams that were delineated or investigated within the site, including their size, vegetation cover class, likely Washington Dept. of Ecology (DOE) ratings, and corresponding buffer widths that likely would be required per City of Auburn (2014) code. Wetland delineation data forms for the wetland and upland area are found in Appendix A of the Wetland Report. Table 1. Wetland Ratings per revised WDOE (Hruby 2004, WDOE 2008b) ratings form and corresponding City of Auburn (2014) buffer standards: Cowardin Classification HGM Classification WDOE Rating Total Function Score Habitat Function Score Wetland Buffer (ft.) Wetland 1 PFO Riverine III 33 16 25-50 Wetland 2 PEM Riverine IV 22 16 25-30 Wetland A PFO Riverine III 48 20 25-50 Wetland B PEM/PFO Slope III 34 21 25-50 Wetland C PFO Slope III 37 18 25-50 Wetland D PEM/PSS Depressional 11 53 17 50-100 Table 2. Stream Classifications and corresponding City Auburn (2014) buffer standards: Stream Class Minimum Buffer (ft.) Stream A III 25-50 Stream B III 25-50 Stream AB III 25-50 41. The Wetland Assessment, Diamond Valley Estates Auburn WA, Raedeke Associates Inc. April 8, 2014, identifies that alteration of site wetlands may be subject to jurisdiction of the Army Corps of Engineers (COE) and the Washington Dept. of Ecology (WDOE) and alteration of the site streams (including changes in flow) are subject to the jurisdiction of the Washington Dept. of Fish and Wildlife. 42. The Site slopes and geologic hazards areas were evaluated in the report: A Geotechnical Engineering Services and Geomorphology Services, Diamond Valley Estates Development, Auburn WA, GeoEngineers, April 18, 2014., Rev. November 16, 2015, Rev. April 21, 2016. At Page1, the Report describes the relationship of site conditions to project construction as follows: “Existing features at the site include locally steep, forested ravine slopes with a small stream and a series of associated wetlands occupying the lower areas of the parcel. We understand the plat concept in its present form includes 200 single- family lots. These lots are laid out on three primary tiers of land that will be significantly re-graded from the existing topography. The subdivision concept includes a stormwater drainage system with two detention ponds (Pond 1 and Pond 2) situated near the toes of steep slopes. The two ponds will be partially cut into the slopes, with retaining walls constructed along their uphill boundaries and 267 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 13 retaining walls and fill berms constructed along their downslope boundaries. We understand that the current conceptual configuration of Pond 1 includes a cut made into a northwest facing native slope with a buttress wall at the toe of the cut, transitioning to a fill berm with an inboard retaining wall on the downslope boundary of the pond. We understand that the proposed pond bottom elevation will lie at Elevation 315 feet (NAVD 1988 datum), with the top-of-pond berm elevation at Elevation 330 feet. The top of the retaining walls will also be at Elevation 330 feet.” “We also understand that the current conceptual configuration of Pond 2 includes a cut made into an east facing native slope with a buttress wall at the toe of the cut, transitioning to a fill berm on the downslope boundary of the pond. A retaining wall will also be constructed on the inboard side of the berm. We understand that the proposed pond bottom will be at Elevation 285 feet, with the top-of-pond berm and top of wall elevations both at Elevation 300 feet.” “We understand that both ponds are intended to be used for stormwater detention, and neither pond will have graded slopes, inboard or outboard, steeper than 2H:1V (horizontal to vertical). According to the City, the ponds are to be lined.” “Several new roadways will be constructed for the development, including Road F which will be located in the south half of the development. Road F will cross the broad ravine bottom that extends south to north through the site, and will also cross an existing steep slope area that is inclined at 40 percent or steeper. A fill embankment with an approximate height up to about 40 feet will support the roadway where it crosses the ravine bottom. Fill slope inclinations for the embankment will be at 2H:1V. Cuts will be made uphill of the roadway within the steep slope area; these cuts will be up to about 35 feet in height and will also be inclined at 2H:1V. Much of this grading is intended to create level lots for houses. An existing steep slope inclined at approximately 2H:1V will remain and extend from a segment of Road F down to near the south end of Pond 1. A steep slope area has also been identified within Lots 7 and 8 near the southwest corner of the development. We understand that grading on and near these lots will also result in finished cut slopes of 2H:1V.” 43. Based on the geologic, geomorphic, hydrogeologic and geotechnical engineering characteristics investigated, the Report: A Geotechnical Engineering Services and Geomorphology Services, Diamond Valley Estates Development, Auburn WA, GeoEngineers, April 18, 2014., Rev. April 21, 2016 (Exhibit 14), contains numerous recommendations for construction on Pages 33 through 46. The recommendations address such subjects as: • Earthwork, clearing & site preparation, subgrade preparation & structural fill, temporary cut slopes, permanent cut and fill slopes, Utility trenches, sanitary sewer main construction, & sedimentation and erosion control • Foundation design, foundation settlement, lateral resistance, & footing drains • Below grade wall and retaining walls design parameters, back drainage, wall design construction considerations • floor slab support, seismicity, ground shaking, liquefaction potential, ground rupture • pavement recommendations and subgrade preparation, asphalt concrete pavement, drainage considerations • Grading considerations, benching, & terracing 268 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 14 • Proposed development of storm ponds • Proposed development on slopes exceeding 40 percent • Downstream drainage mitigation 44. It is possible that further geotechnical analysis of the site required during civil plan review or-- as a result of redesign--may result in the loss of and/or reconfiguration of certain lots. All lots must accommodate reasonable site development (building foot print) and meet the requirements for maximum driveway grades and of stormwater management and seek to avoid requiring variances/deviations in the future. 45. The Site is not located in the regulatory floodplain or special flood hazard areas per Federal Emergency Management Agency (FEMA) maps. 46. The Site is located partially in Groundwater Protection Zone 3 and partially in Groundwater Protection Zone 4 and the Project shall implement best management practices for water resource protection during construction, as required by City critical areas regulations. 47. The Site is not located within any shoreline designation. 48. Due to the length of time and numerous project changes, a combined Notice of Application and Notice of Hearing was issued on January 10, 2017 (Exhibit 28). The Notice of Public Hearing was issued a minimum of 10 days prior to the public hearing date as required by ACC 18.70.040. The notice was posted at the Site, mailed to adjacent property owners within at least 300 feet of the Site, and published in The Seattle Times newspaper (Exhibit 29). III. PRELIMINARY PLAT CONCLUSIONS: 1. ACC Section 17.10.070 specifies the approval criteria for a Preliminary Plat. Following is staff analysis of this Preliminary Plat application’s compliance with each criterion. The criteria are listed below in italics, followed by a staff analysis. A. Adequate provisions are made for the public health, safety and general welfare and for open spaces, drainage ways, streets, alleys, other public ways, water supplies, sanitary wastes, parks, playgrounds and schools. Staff Analysis: The Project includes adequate provisions for public health, safety and general welfare through provision of open spaces, non-motorized and public road access, water and sanitary sewer service, stormwater management, fire protection, recreation, and schools. Open Space - The topography and presence of critical areas (geologic hazard areas, wetlands and streams) results in a development configuration of tiered roads and lots and results in a proportion of the Project area set aside in Tracts as “Open Space” to buffer to adjacent development like subdivisions to the west (Lakeland Hills Division 9 and 10) and to the east (Forest Glen (future plat) & Lakeland Hills Estates). The open space also serves as a buffer and amenity for the future residents. While Sheet 1 of the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016, lists seven of the ten tracts as proposed for “Open Space” (Tracts A, B, E, F, G, H, and I). Two of these tracts (Tracts B & F) are really utility corridors and Tract H is established for roadway sight distance and thus these three are of limited natural “Open Space” benefit due to compatibility of vegetative maintenance. Three of the four remaining tracts (Tracts A, E, & G) while they may partially be disturbed by clearing and grading will be required to be replanted in native vegetation and represent approximately 13.0 percent of the site. The remaining Tract I, which is approximately 24.1 percent of the site 269 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 15 is proposed to consist of a mosaic of maintained stormwater ponds (Storm Pond #1 & #2), side slopes and maintenance accesses to the stormwater ponds & utilities, and the site’s streams and wetlands and city required buffers associated with each. As noted on this Sheet 1, the purpose and configuration of Tracts, especially Tract I, will likely be refined through the civil plan review process. Related to this, it is generally not appropriate to have the City Storm utility own and maintain the critical area features within this Tract for which there is mitigation construction monitoring obligations unless there is a mechanism to distinguish between management of the different functional areas. Separate tracts are generally preferential. Non-Motorized & Public Road Access – Sheet 1 of the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016, lists the following publicly dedicated roads to be constructed with the plat, as follows: o ROAD B = 2,871+/- LF. 50' / Variable Width ROW, 171,246+/- SF. o ROAD C = 1,379+/- LF. 50' / Variable Width ROW, 87,435+/- SF. o ROAD E = 480+/- LF. 50' R/W, 28,449+/- SF. o ROAD F = 975+/- LF. 50' / Variable Width ROW, 54,406+/- SF. o ROAD G = 883+/- LF. 50' ROW, 53,345+/-. SF. No private roads are proposed. However, Tracts C, D, & J are proposed as private shared access and utility tracts serving specific adjacent lots. These tracts may be owned jointly by the adjacent lot owners or the HOA. As noted, Evergreen Way SE (a Residential Collector) was previously constructed and runs east-west through the southern portion of the plat. The rest of the plat roads are to be constructed for the plat by the applicant. An excerpt from the City’s Transportation Plan, Policy TR-66 provides guidance on city standards for length of stub-end streets and number of dwellings accessed: “3. The City Engineer shall have the discretion to permit stub end streets and require interim mitigation for stub end streets longer than 600 feet to provide for adequate circulation and access. However, this does not diminish the City Council's authority to deny stub end streets longer than 600 ft.” “4. Dead end streets shall not be more than 600 feet-in-length. --Dead end streets ending - in permanent cul-de-sacs shall serve a maximum of 25 dwelling units. When applicable, non-motorized paths shall be provided at the end of the street to shorten walking distances to an adjacent arterial or public facilities including, but not limited to, schools and parks.” Dedication of ROW and construction of improvements for Road B to a “boulevard-modified” Residential Collector standard between Evergreen Way SE and G ST SE and approximately 100 feet north of Evergreen Way SE is proposed. Approval of a deviation (modification of plat standard) is requested to the boulevard cross section in order to provide a wider divided access as an alternative to providing a second access. Dedication of ROW and construction of improvements for Road B to a modified “Local Residential” standard between 100 feet north of Evergreen Way SE and the intersection of Roads B/C/F is proposed. Approval of a deviation (modification of plat standard) is requested 270 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 16 to provide two travels lanes and parking on one side. The other side would be required to be marked “no parking”. Dedication of ROW and construction of improvements for Road B to a modified “Local Residential” standard between the intersection of Roads B/C/F and north to approximately Lots 124 and 97 is proposed. Approval of a deviation (modification of plat standard) is requested to provide two travels lanes and a center two-way left turn lane with no parking on either side. Dedication of ROW and construction of improvements for Road C to a modified “Local Residential” standard between the intersection of Roads B/C/F and north to approximately Lots 173 and 143 is proposed. Approval of a deviation (modification of City standard) is requested to provide two travel lanes and a center median with no parking on either side. In its review of the Project, the City’s Transportation staff and the Valley Regional Fire Authority (VRFA), with approval of the modifications of plat standards and with the conditions recommended, found the proposed ROW dedications and improvements to provide safe and sufficient access to serve the lots. Non-Motorized access will be provided by public sidewalks constructed on both sides of the public streets. The topography and presence of critical areas (geologic hazard areas, wetlands and streams) results in a development configuration of tiered roads and lots that limits opportunities for separate pedestrian pathways outside of right-of-way linking to off-site development. Tract D may have potential as a pedestrian pathway connection to development to the south. Water, Sanitary Sewer Service, & Stormwater Management - The City provides water service to the plat. Connections will be required to constructed to the existing 12-inch water lines in Evergreen Way SE with main line extensions within the rights-of-way of the plat, or within publicly dedicated tracts or easements. Due to considerable elevation changes across the site, the site will require separation into three water pressure zones regulated by pressure reducing stations to be constructed by the applicant, generally, as follows: 630 zone – Lots 1 – 54 565 zone – Lots 55 - 84 and 133 - 200 500 zone – Lots 85 - 132 The City provides sewer service to the plat. Connections will be required to be constructed from the terminus of the sewer line existing near the NE corner of the site that was previously constructed with the earlier divisions of the Kersey III, Preliminary Plats. The construction of public main extensions will be required westward along the north property boundary of the plat to Road B and within the right-of-way through the plat. Where the public mains are not coincident with street rights-of-way, publicly dedicated tracts or easements are required to city standards. Based on city Utilities Division review of conceptual utility plans, City water and sewer service is available and capable of serving the Site. Stormwater management, drainage, and erosion control will be adequately provided consistent with the ACC 13.48, “Storm Drainage Utility”, ACC 15.74, “Land Clearing, Filling, and Grading”, the City’s Surface Water Management Manual (SWMM), and other applicable City standards. 271 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 17 The Report: Preliminary Plat Conceptual Storm Drainage Report for Diamond Valley Estates, Apex Engineer PLLC, March 26, 2014, Rev. December 8, 2014 (Exhibit 4), provides the following summary of the site’s existing and proposed stormwater management system: “As part of the Evergreen Way SE construction, a storm pond was constructed for water quality and water quantity for runoff from Evergreen Way SE. Offsite flow from the south is conveyed under Evergreen Way SE in a separate conveyance system and does not flow into the Evergreen Way SE pond.” “With the exception of Evergreen Way SE, the majority of the existing site is forested and contains wetlands in the northeast portion of the site. There is approximately 150 feet of fall in elevation from the north to the south and approximately 201 feet of fall in elevation from the west to the east. According to the geotechnical study performed as part of the Kersey Ill EIS, site soils are generally of the Alderwood series (Type C).” “Wetlands have been identified in the northeast portion of the site that are "flow-through" and drain to the unnamed tributary. The unnamed tributary flows through the northeastern portion of the site, meanders off the project through the northwesterly margin of the adjacent Lakeland Hills Estates project, and back into the DVE project just before crossing under the sewer access road at the northeast corner of the DVE project in a 24-inch diameter culvert.” “Based on the existing ground topography, there are two existing drainage basins. The developed condition also has two drainage basins. In order to not create downstream impacts, a detention pond is proposed in each developed basin that outlets to the wetlands of the unnamed tributary. A drainage area south of the project contributes flow to the project and is collected in a bypass pipe that is conveyed to the unnamed tributary.” “Chapter 2: Existing Conditions Summary Below is a summary of the existing conditions of each basin for the project. Refer to the Pre- Developed Basin map for a pictorial view of the existing conditions.” Existing Basin 1 - 58.8 Acres Forested Condition – Mod. Slope - Type C soil Existing Basin 2 - 32.8 Acres Forested Condition - Steep Slope - Type C soil “Chapter 3: Off-Site Analysis An off-site drainage analysis was performed for the Kersey Ill EIS in 2004. Per current City of Auburn design guidelines, stormwater discharges shall match developed discharge durations to pre-developed durations for the range of pre- developed discharge rates from 50% of the 2- year peak flow up to the full 50- year peak flow. The pre-developed condition to be matched shall be a forested land cover. Given these constraints, impacts to the downstream system are not anticipated.” “As part of the preliminary plat process, a qualitative downstream analysis was performed on September 12, 2013. See Appendix D for the downstream notes and map. Additional analysis of the downstream system was prepared by GeoEngineers. This analysis determined that the downstream system will not be adversely affected by the controlled release from stormwater drainage improvements.” 272 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 18 There are existing water and sewer system payback agreements that apply for all parcels of the proposed plat. Fire Protection - Adequate provision of fire and emergency access is provided by the provision of public streets. In its review of the Project, the City’s Transportation staff and the Valley Regional Fire Authority (VRFA), with approval of the modifications and with the proposed conditions, found the proposed ROW dedications and improvements to provide safe and sufficient access to serve the lots. Adequate provision of fire protection is anticipated to be provided by installation of water mains and fire hydrants meeting city standards and by constructing fire sprinklers within selected homes. Fire protection is also provided through the payment of fire impact fees at the time of Building Permit issuance for each lot or as may be deferred per ACC 19.06.040(F) and construction consistent with the City of Auburn Engineering Design Standards and the International Fire Code (IFC) To ensure emergency access to the lots of the Plat, the project must comply with International Fire Code (IFC) requirements. This will include constructing homes with fire sprinkler systems where more than 30 lots cannot be served by two separate and remote approved fire apparatus access roads for the residential lots (see Section D107 and D104.3 of the IFC). As conditioned, the Project will have adequate provisions for emergency access/fire protection. Recreation - Adequate provisions for parks are made through the payment of park impact fees at the time of Building Permit issuance for each lot or as may be deferred per ACC 19.08.030(G). The proposed Project of 200 lots exceeds the threshold of 50 units that requires the dedication of park space in accordance with ACC 17.14.100, (Parks and Playgrounds). However, as part of the Lakeland Hills Special Planning Area, Policy LH2.3 provides a requirement to provide 7.25 acres of parking land per 1,000 residents at a rate of 2.5 persons per household. An amount of park land dedication has been already satisfied by the past dedication of park land within and around Lakeland Hills at the time of past Lakeland developers, including Lakeland Hills Park, Roegner Park, Sunset Park, Mill Pond Park, and Natural Open Spaces. Schools - Adequate provisions for schools are made through the payment of school impact fees at the time of Building Permit issuance for each lot or as may be deferred per ACC 19.02.070(E). Access for safe school walking routes will be provided by the public sidewalks constructed along both sides of the plat’s internal streets. According to the document: School Access Analysis Diamond Valley Estates, Apex Engineering PLLC, undated, the proposed lots/homes are within the Auburn School District; and served by Gildo Rey Elementary, Olympic Middle, and Auburn High School. Gilda Rey Elementary is located approximately 3.3 miles to the north. Olympic Middle School is located approximately 4.5 miles to the north. Auburn High School is located approximately 5.5 miles to the north. It is anticipated that students would be bused to all three school locations. Staff finds the Project meets the criterion, as conditioned herein and with approval of the identified modification to plat standards (deviations). B. Conformance of the proposed subdivision to the general purposes of the comprehensive plan. Staff Analysis: The Applications are vested to the Comprehensive Plan in effect prior to the adoption of substantially revised Comprehensive Plan adopted in December of 2015. The 273 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 19 Comprehensive Plan contains policy guidance related to this application. The Project is consistent with the general purposes of the Comprehensive Plan. Specifically, the Project is consistent with the following Comprehensive Plan goals, objectives, and policies: “Capital Facilities Goal 13: City Utilities “Ensure that development will only occur if the urban services necessary to support the development will be available at the time of development.” “Objective 13.1: To ensure safe and adequate water service, for both domestic and fire protection purposes, to meet the needs of the existing community and provide for its planned growth.” “Policy CF-16: The City shall continue its policy of requiring that water system extensions needed to serve new development shall be built prior to or simultaneous with such development, according to the size and configuration identified by the Comprehensive Water Plan as necessary to serve future planned development.” “Policy CF-18: The City shall continue to recognize the overall system impacts of new development upon the City water system through the collection and appropriate use of system development charges or similar fees.” “Objective 13.2: To ensure the efficient transmission of sanitary sewage to the appropriate treatment and disposal facilities, in order to meet the needs of the existing community and provide for its planned growth.” “Policy CF-23: The City shall continue its policy of requiring that sewer system extensions needed to serve new development shall be built prior to or simultaneous with such development, according to the size and configuration identified by the Comprehensive Sanitary Sewer Plan and Comprehensive Plan as necessary to serve future planned development.” “Policy CF-25: The City shall continue to recognize the overall system impacts of new development upon the City sewer system, through the collection and appropriate use of system development charges or similar fees.” “Objective 13.4: To ensure that collection, conveyance, storage and discharge of storm drainage is provided in a sufficient and environmentally responsible manner, in order to meet the needs of the existing community and provide for its planned growth.” “Policy CF-37: The City shall require developers to construct storm drainage improvements directly serving the development, including any necessary off-site improvements.” “Policy CF-39: The City shall recognize the overall system impacts of new development upon the City's drainage system, through the collection of system development charges or similar fees to assist in the financing of new and oversized (e.g. regional drainage improvements.)” “Policy CF-42: Drainage facilities serving the larger community should be owned, operated and maintained by the City's storm drainage utility.” “Policy CF-53: The City shall seek to minimize the impacts to the natural river system’s hydrology by encouraging pre-treatment of surface flows of new development and re- introduction into the groundwater where feasible.” 274 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 20 The necessary City utilities are available for the Project, specifically water and sewer service are available and capable of serving the Site. To ensure that the water and sewer service impacts of the new development are addressed, water and sewer system development charges are assessed at the time of Building Permit issuance for each lot. The stormwater resulting from the plat’s grading and construction of impervious surfaces is proposed to be managed within the site’s two existing drainage basins. A detention pond in each developed basin is proposed near the NE corner of the site and each outlets to the site’s wetlands or streams. Also, a drainage area south of the project contributes flow to the project and is collected in a bypass pipe that is conveyed to the unnamed tributary. Based on City Utility division’s review of the conceptual utility plans within the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016 and the Preliminary Plat Conceptual Storm Drainage Report for Diamond Valley Estates, Apex Engineer PLLC, March 26, 2014, Rev. December 8, 2014, it is anticipated stormwater management, drainage, and erosion control will be adequately provided consistent with the ACC 13.48 Storm Drainage Utility, ACC 15.74 Land Clearing, Filling, and Grading, the City’s 2009 Surface Water Management Manual (SWMM), and any other applicable City standards. To ensure that the storm drainage impacts of the new development are addressed, storm system development charges are assessed at the time of Facilities Extension Agreement (FAC) approval for the Site and Building Permit issuance for each lot. “Land Use Goal 7: Residential Development To emphasize housing development at single family densities, in order to reestablish a mix of housing types appropriate for a family oriented community, while recognizing the need and desire for both lower density and higher density housing appropriately located to meet the housing needs of all members of the community.” “Policy LU-17: Residential densities in areas designated for single family residential uses should be no greater than 7 units per acre.” “Objective 7.2: To designate land for the development of new single family homes.” “Policy LU-26: Emphasis shall be placed upon the manner in which the recreational needs of the residents shall be met in the approval of any residential development.” “Parks Goal 21: Parks, Recreation, and Open Space To provide and maintain a comprehensive system of parks and opens spaces that responds to the recreational, cultural, environment, and aesthetic needs and desires of the City’s residents.” “Policy PR-2: New developments shall contribute to the development of new parks at a level commensurate with their share of new facility needs as established by the Park and Recreation Plan.” The Site is approximately 79.44 acres (3,460,427 sq. ft.). The net site area used to calculate density, which excludes the areas specified in ACC 18.02.065(A), “Methods of Calculating Density”, is 64.3 acres (2,801,098 sq. ft.). With 200 lots proposed, the unit count is less than the R5 Residential zoning district minimum density of 4 units per acre (238 dwelling units). However, relief from the minimum density has been requested by the Applicant and appears justified by the site’s topography and critical areas (geologic hazard areas, wetlands and streams). 275 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 21 With approval of the variance, the Project can be made consistent with the Comprehensive Plan policy regarding density of areas designated for single-family residential uses. As such, the proposed Project assists the City in meeting its housing targets and growth management objectives. Recreational needs of the residents are met through the previous dedications of park land as part of the Lakeland Hills Special Planning Area and through assessment of park impact fees at the time of Building Permit issuance for each lot unless deferred per ACC 19.08.030(G). Staff finds the Project meets the criterion. C. Conformance of the proposed subdivision to the general purposes of any other applicable policies or plans which have been adopted by the City Council. Staff Analysis: The preceding analysis for approval Criteria B is in support of the Project’s consistency with the City of Auburn Capital Facilities Plan, Comprehensive Water Plan, Comprehensive Sewer Plan, Comprehensive Drainage Plan, and the Parks, Recreation and Open Space Plan. The Project is also consistent with general purposes of the Comprehensive Transportation Plan. Specifically, the Project is consistent with the following Comprehensive Plan elements: “Policy TR-4: Safety shall be prioritized over driving convenience.” “Policy TR-23: Require developments to construct or finance transportation improvements and/or implement strategies that mitigate the impacts of new development concurrent with (within 6 years of) development, as required by the Growth Management act.” “Coordination, Planning, and Implementation Objective: Finance To finance the transportation systems necessary to serve new development, while ensuring the City has the capability to finance general transportation needs.” “Policy TR-28: Require developments or redevelopments to construct transportation infrastructure systems needed to serve new developments.” Policy TR-30: Improvements that serve new developments will be constructed as a part of the development process. All costs will be borne by the developer when the development is served by the proposed transportation improvements. In some instances, the City may choose to participate in this construction if improvements serve more than adjacent developments. “Policy TR-34: Maintain a traffic impact fee system based on the Institute of Traffic Engineers (ITE) guidelines, as modified by the City Council, as a means of enabling development to mitigate appropriately for associated traffic impacts.” “Policy TR-55: On-street parking should be allowed only when consistent with the function of the street and with traffic volumes.” “Policy TR-56: New developments should provide adequate off-street parking to meet their needs.” “Street System Objective: Functional Classification To provide an integrated street network of appropriate classes of streets designed to facilitate different types of traffic flows and access needs.” 276 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 22 “Policy TR-75: The classification standards adopted in the Auburn Engineering Design Standards are considered the City’s minimum standards for new streets. In cases in which the City attempts to rebuild an existing street within an established right-of-way, the City Council reserves the authority to determine if additional right-of-way should be obtained in order to realize the improvement. Preservation of neighborhood continuity and cohesiveness will be respected.” The Project is required to construct transportation infrastructure system improvements per ACC 12.64A, “Required Public Improvements.” The City’s Transportation staff have conceptually reviewed the proposed ROW dedications and construction of improvements for consistency with the City of Auburn Engineering Design Standards. The proposed public ROW dedications and construction of improvements are summarized as follows: o ROAD B = 2,871+/- LF. 50' / Variable Width ROW, 171,246+/- SF. o ROAD C = 1,379+/- LF. 50' / Variable Width ROW, 87,435+/- SF. o ROAD E = 480+/- LF. 50' ROW, 28,449+/- SF. o ROAD F = 975+/- LF. 50' / Variable Width ROW, 54,406+/- SF. o ROAD G = 883+/- LF. 50' ROW, 53,345+/-. SF. In addition, to ensure that the transportation needs of all residents are addressed, demonstration of adequate off-street parking provided per ACC 18.52 is required for Building Permit approval, and traffic impact fees are assessed at the time of Building Permit issuance for each lot. The Valley Regional Fire Authority has also reviewed the proposed right-of-way dedications and construction of improvements and has identified the need to restrict on-street parking on portions of Road B and C as a Condition of Approval for the Preliminary Plat due to width to provide adequate emergency access. As such, the Project will facilitate the different types of traffic flows and access needs for the Site, as conditioned herein. Non-Motorized System Objective: Pedestrian Travel To enhance and encourage pedestrian travel in Auburn. Policy TR-130: Require developers to incorporate pedestrian facilities into new development and redevelopment in conformance with the Auburn City Code. Policy TR-133: Work towards buffering pedestrian walkways from moving traffic, particularly in areas with high levels of pedestrian movements, such as near schools and commercial areas, and along corridors with heavy vehicular traffic. As part of the Project, sidewalks are required along the Site’s street frontages. Sidewalks will be constructed where roads and sidewalks do not exist today and connecting to Evergreen Way SE. During civil plan review, the City should evaluate whether Tract D, a shared access and utility tract could be extended north to Evergreen Way SE to provide a public pedestrian connection and shorter route of travel to the adjacent subdivision of Kersey III, Division 2. The “Residential Collector” and “Local Residential” street standards per the City of Auburn Engineering Design Standards include the use of landscaping area to separate the sidewalk from vehicular traffic. “Non-Motorized System Objective: Bicycle Travel To improve Auburn’s bicycling network. 277 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 23 Policy TR-138: During the development review process, ensure projects are consistent with the Non-Motorized chapter of the Comprehensive Transportation Plan by requiring right-of-way dedications and other improvements as needed to develop the bicycle network.” Staff finds the Project meets the criterion, as conditioned herein. D. Conformance of the proposed subdivision to the general purposes of this title, as enumerated in ACC 17.02.030. “The purpose of this title is to regulate the division of land lying within the corporate limits of the city, and to promote the public health, safety and general welfare and prevent or abate public nuisances in accordance with standards established by the state and the city, and to: • Prevent the overcrowding of land; • Promote safe and convenient travel by the public on streets and highways; • Promote the effective use of land; • Provide for adequate light and air; • Facilitate adequate provision for water, sewerage, storm drainage, parks and recreational areas, sites for schools and school grounds, and other public requirements; • Provide for proper ingress and egress; • Provide for the expeditious review and approval of proposed land divisions which comply with this title, the Auburn zoning ordinance, other city plans, policies and land use controls, and Chapter 58.17 RCW; • Adequately provide for the housing and commercial needs of the citizens of the state and city; • Require uniform monumenting of land divisions and conveyance by accurate legal description; and • Implement the goals, objectives and policies of the Auburn comprehensive plan.” Staff Analysis: The proposed Project meets the general purposes of ACC Title 17, “Land Adjustments and Divisions”. With approval of the requested variances (critical area and minimum density) and the transportation and utility related modifications to plat standards (deviations), the proposed Project will meet meets the general purposes of ACC Title 17, “Land Adjustments and Divisions”. The Project remains consistent with general purpose of the city’s subdivision code (ACC 17.02.030) in that it does not overcrowd the Site with development, is an effective use of land, and will provide for adequate light and air through the setback and lot coverage requirements of the R5 zoning district. As addressed under Staff Analysis of Criterion A above, the proposed Project makes adequate provisions for ingress/egress, water, sewer, storm drainage, fire protection, schools, and parks. Staff Analysis of Criterion B, above, addresses how the project complies with the City of Auburn Comprehensive Plan. The proposed Project will develop 200 single-family residential lots providing housing for citizens of the state and city. 278 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 24 As such, the Project is also consistent with subdivision standards of Revised Code of Washington (RCW) 58.17. Staff finds the Project meets the criterion. E.Conformance of the proposed subdivision to the Auburn zoning ordinance and any other applicable planning or engineering standards and specifications as adopted by the city, or as modified and approved as part of a previously approved PUD. Staff Analysis: The proposed Project meets or is capable of meeting the zoning standards and critical area regulations with two exceptions. More specifically, the plat meets or is cable of meeting R5 zoning district development regulations specified in ACC Section 18.07.030, except for the minimum density standard. A comparison of the project to the city standards is as follows Development Standard Standard of the R5 Zone Standard as Proposed by the Project Minimum lot width 50 ft. 50 ft. Minimum lot area per dwelling unit 6,000sq. ft. 6,000 sq. ft. Minimum average lot area per dwelling unit 8,000 sq. ft. SF 8,791 sq. ft. The future single-family residences will be required to meet the zoning development standards, such as minimum setbacks and lot coverage specified for the R5 zone in ACC 18.07.030. More specifically, the plat meets or is cable of meeting the city’s critical area regulations specified in ACC Section 16.10. except for the prohibition on alteration of Class IV Landslide Hazard Areas. The application requests a variance from the city’s critical area requirements that prohibit alteration of Class IV landslide hazard areas (ACC 16.10.100(E)(2)). The plat proposes grading and alteration of Class IV Landslide Hazard Areas within the southwest corner of the Plat for Tract A, (Open Space) and the adjacent Lots 7 & 8 and Tract A and grading and alteration of Class IV Landslide Hazard Areas near the south-central portion for “Road F” Lots 71 through 73 and “Tract I” (storm drainage tract). The Project meets or is capable of meeting other applicable engineering standards except for the requested transportation and stormwater pond related Modification (deviations). Road, storm drainage, sewer, and water facilities will be reviewed for conformance with, and are required to meet the City’s Engineering Design and Construction Standards. These facilities are reviewed as part of the Facility Extension Agreement (FAC), Grading, Storm, and Building Permit applications and plans to be submitted by the Applicant. With approval of the requested variances (from the critical area regulations and R5 minimum density standard of the zoning code) and the transportation and storm pond related deviations, the proposed Project will meet the Auburn zoning ordinance and any other applicable planning or engineering standards and specifications as adopted by the city. With approval of the requested variances (from the critical area regulations and R5 minimum density standard of the zoning code) and the transportation and storm pond related 279 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 25 deviations, staff finds the Project meets the criterion. The Project is not part of an approved Planned Unit Development (PUD). F. The potential environmental impacts of the proposed subdivision are mitigated such that the preliminary plat will not have an unacceptable adverse effect upon the quality of the environment; Staff Analysis: Development of this property was thoroughly evaluated through an Environmental Impact Statement process. The Final EIS, issued on February 11, 2005, includes 10 pages of potential impacts and suggested mitigation measures, which are recommended to be made conditions of project approval. With implementation and observance of the EIS conditions (mitigation measures) and the proposed plat conditions the Project will not have significant adverse environmental impacts. Staff finds the Project meets the criterion. G. Adequate provisions are made so the preliminary plat will prevent or abate public nuisances. Staff Analysis: Adequate provisions are made so the proposed Project will prevent or abate public nuisances. The Site is currently mainly vacant forested hillside generally sloping to the NE. The southern portion of the Site contains an east-west segment of Evergreen Way SE and associated temporary stormwater pond for the road. As the site is mainly undeveloped, there are no active code violation cases for the site and no known public nuisances. In the future, the proposed construction of the plat will be reviewed as part of the Facility Extension Agreement (FAC), Grading, Storm, and Building Permit applications and plans to be submitted by the Applicant. With construction consistent with subsequent City approvals, the creation of public nuisances will be prevented. Staff finds the Project meets the criterion, as conditioned herein. IV. CONCLUSIONS - VARIANCE FROM CRITICAL AREA REGULATIONS (File No. VAR16-0001): 1. On May 5, 2016 a variance application (File No VAR16-0001) was filed by James “Tres” Kirkebo of Apex Engineering, PLLC on behalf of Randall Jackson, as Manager of JDH Investment Group Corporation related to the subdivision of an approximately 79.45 acres (“Site”) into 200 single-family residential lots and ten tracts under the R5, Residential five dwelling units per acre zoning standard. 2. The application requests a variance from the city’s critical area requirements that prohibit alteration of Class IV Landslide Hazard Areas (ACC 16.10.100(E)(2)). The plat proposes grading and alteration of Class IV Landslide Hazard Areas within two different geographic areas of the site; the southwest corner of the Plat for Tract A, (Open Space) and the adjacent Lots 7 & 8 and grading and alteration of Class IV Landslide Hazard Areas near the south- central portion for “Road F”, Lots 71 through 73 and within “Tract I” (storm drainage tract). 3. The City’s critical areas regulations provide the following general and specific purpose statement at ACC 16.10.010(B): “B. The city finds that these critical areas perform a variety of valuable and beneficial biological and physical functions that benefit the city and its residents. Alteration of 280 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 26 certain critical areas may also pose a threat to public safety or to public and private property or the environment. The city therefore finds that identification, regulation and protection of critical areas are necessary to protect the public health, safety and general welfare. The city further finds that the functions of critical areas and the purpose of these regulations include the following: 5. Geologic Hazard Areas. Geologic hazard areas include lands or areas characterized by geologic, hydrologic and topographic conditions that render them susceptible to varying degrees of risk of landslides, erosion, seismic or volcanic activity. The primary goals of regulating geologic hazards are to avoid and minimize potential impacts to life and property by regulating and/or limiting land uses where necessary, and to conduct appropriate levels of analysis and ensure sound engineering and construction practices to address identified hazards.” 4. The City’s critical areas regulations at ACC 16.10.080 (Classification and rating of critical areas) provides the following system of classifications applicable to Landslide Hazard Areas: “G. Geologic Hazard Classifications. Geologic hazard areas shall be classified according to the criteria in this section: . 2. Landslide Hazard Areas. Landslide hazard areas are classified as Class I, Class II, Class III, or Class IV as follows: a. Class I/Low Hazard. Areas with slopes of 15 percent or less. b. Class II/Moderate Hazard. Areas with slopes of between 15 percent and 40 percent and that are underlain by soils that consist largely of sand, gravel, or glacial till. c. Class III/High Hazard. Areas with slopes between 15 percent and 40 percent that are underlain by soils consisting largely of silt and clay. d. Class IV/Very High Hazard. Areas with slopes steeper than 15 percent with mappable zones of emergent water (e.g., springs or ground water seepage), areas of known (mappable) landslide deposits regardless of slope, and all areas with slopes 40 percent or greater.” 5. Class IV Very High Landslide Hazard is the highest, most sensitive category. To avoid and minimize potential impacts to life and property from identified landslide hazards, the city’s critical area regulations provide certain specific standards based on the degree of susceptibility; the critical areas code prohibits the alteration of Class IV – Very High Hazard Landslide Hazard Areas. Specifically, ACC 16.10.100 (Alteration or development of critical areas – Standards and criteria) says. “ACC 16.10.100 Alteration or development of critical areas – Standards and criteria Alteration of specific critical areas and/or their buffers may be allowed by the director subject to the criteria of this section. Alteration shall implement the mitigation standards as identified in ACC 16.10.110, and the performance standards of ACC 16.10.120 and the monitoring requirements of ACC 16.10.130.” “E. Geologic Hazard Areas.” “1. General Standards. The city may approve, condition or deny proposals for the alteration of geologic hazard areas, as appropriate, based on the degree to which the significant risks posed by critical hazard areas to public and private property and to public health and safety can be mitigated. The objective of mitigation measures shall be to render a site containing a critical geologic hazard as safe as one not containing such hazard or one characterized by a low hazard. In appropriate cases, conditions 281 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 27 may include limitations of proposed uses, modification of density, alteration of site layout and other appropriate changes to the proposal. Where potential impacts cannot be effectively mitigated or where the risk to public health, safety and welfare, public or private property, or important natural resources is significant notwithstanding mitigation, the proposal shall be denied.” “2. Specific Standards. a.Class IV Landslide Hazard Areas. Alteration shall be prohibited subject to the reasonable use provisions of this chapter.” (Emphasis added) 6.The city’s critical area regulations provide the following variance process and criteria for relief from standards. “16.10.160 Variances. Applications for variances to the strict application of the terms of this chapter to a property may be submitted to the city. Minor variances, defined as up to and including 10 percent of the requirement, may be granted by the director as a Type II decision as defined by Chapter 14.03 ACC. Variance requests which exceed 10 percent may be granted by the hearing examiner as a Type III decision, pursuant to ACC 14.03.030 and Chapter 2.46 ACC. Approval of variances from the strict application of the critical area requirements shall conform to the following criteria: A. There are unique physical conditions peculiar and inherent to the affected property which make it difficult or infeasible to strictly comply with the provisions of this section; B. The variance is the minimum necessary to accommodate the building footprint and access; C. The proposed variance would preserve the functions and values of the critical area, and/or the proposal does not create or increase a risk to the public health, safety and general welfare, or to public or private property; D. The proposed variance would not adversely affect surrounding properties adjoining; E. Adverse impacts to critical areas resulting from the proposal are minimized; and F. The special circumstances or conditions affecting the property are not a result of the actions of the applicant or previous owner.” 7.Following is staff analysis of this critical area regulation variance application’s compliance with each criterion. The criteria are lettered and listed below in italics, followed by the Applicant’s response as provide with their application and then a staff analysis. A.That there are unique physical conditions including narrowness or shallowness of lot size or shape, or exceptional topographical or other physical conditions peculiar to and inherent in the particular lot; and that, as a result of such unique physical conditions, practical difficulties or unnecessary hardships arise in complying with provisions of this title. Applicant’s Analysis: Variance for Road F, Tract I, and Lots 71 through 73: “Response: The project includes a northeast oriented drainage swale with a creek and wetlands that divides the project area. The proposed Road F provides roadway connectivity to the Gillette project (Forest Glen Preliminary Plat) to the east (Geotech Consultants, 2008) that has already or is expected to receive preliminary plat approval. The roadway grades do not allow development of Road F, Lots 71 through 73 and Tract I from upslope of the locally greater than 40 percent slope area. The proposed Road F, Lots 71 through 73 and Tract I include localized slopes that are greater than 40 percent that slope north toward the drainage swale that includes Wetland A. Development of Road F, Lots 71 through 73 and Tract I avoids Wetland A impact but requires some placement of fill local fill and cuts. Road F, Lots 71 through 73 and 282 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 28 Tract I cross the project site within the lower portion of the slope that includes a slope greater than 40 percent, with a fill embankment and cut slope that avoids impacts to Wetland A. The above listed conditions make it necessary to obtain a variance in accordance with ACC 16.10.160.” Variance for Lots 7 & 8 and Tract A: “Response: The project includes a northeast oriented drainage swale that divides the project area. Lots 7 and 8 are located along east-facing slopes locally inclined at gradients that exceed 40 percent. The grades for the area are such that a fill (as opposed to a cut) for these two lots will have consequences for the intersection at Road G with Evergreen Way SE. Therefore, a localized cut with a mid-slope bench (terrace) for both Lots 7 and 8 is proposed to provide a developable lot area. Lot 7 will also include a retaining wall.” Staff Analysis: The Site slopes and geologic hazards areas were evaluated in the report: A Geotechnical Engineering Services and Geomorphology Services, Diamond Valley Estates Development, Auburn WA, GeoEngineers, April 18, 2014., Rev. November 16, 2015, Rev. April 21, 2016. At Page1, the Report describes the relationship of site conditions to project construction as follows: “Existing features at the site include locally steep, forested ravine slopes with a small stream and a series of associated wetlands occupying the lower areas of the parcel. We understand the plat concept in its present form includes 200 single-family lots. These lots are laid out on three primary tiers of land that will be significantly re-graded from the existing topography. The subdivision concept includes a stormwater drainage system with two detention ponds (Pond 1 and Pond 2) situated near the toes of steep slopes. The two ponds will be partially cut into the slopes, with retaining walls constructed along their uphill boundaries and retaining walls and fill berms constructed along their downslope boundaries. We understand that the current conceptual configuration of Pond 1 includes a cut made into a northwest facing native slope with a buttress wall at the toe of the cut, transitioning to a fill berm with an inboard retaining wall on the downslope boundary of the pond. We understand that the proposed pond bottom elevation will lie at Elevation 315 feet (NAVD 1988 datum), with the top-of-pond berm elevation at Elevation 330 feet. The top of the retaining walls will also be at Elevation 330 feet.” “Several new roadways will be constructed for the development, including Road F which will be located in the south half of the development. Road F will cross the broad ravine bottom that extends south to north through the site, and will also cross an existing steep slope area that is inclined at 40 percent or steeper. A fill embankment with an approximate height up to about 40 feet will support the roadway where it crosses the ravine bottom. Fill slope inclinations for the embankment will be at 2H:1V. Cuts will be made uphill of the roadway within the steep slope area; these cuts will be up to about 35 feet in height and will also be inclined at 2H:1V. Much of this grading is intended to create level lots for houses. An existing steep slope inclined at approximately 2H:1V will remain and extend from a segment of Road F down to near the south end of Pond 1. A steep slope area has also been identified within Lots 7 and 8 near the southwest corner of the development. We understand that grading on and near these lots will also result in finished cut slopes of 2H:1V.” With the exception of Evergreen Way SE, the majority of the existing site is undeveloped and mainly forested and contains wetlands in the northeast, lower portion of the site. There is 283 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 29 approximately 150 feet of fall in elevation from the north to the south and approximately 201 feet of fall in elevation from the west to the east. The Site’s topography is shown on the “Critical Slope Exhibit”, Sheet 26 of 26 as part of the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016. (Exhibit 14) According to this Exhibit the site consists of slopes in the following ranges: • approximately a third of the site is slopes between 15 - 25 percent; • approximately a quarter of the site consists of slopes between 25 - 40 percent; and, • approximately eight percent of the site consists of slopes greater than 40 percent slopes. All areas with slopes 40 percent or greater are classified as Class IV/Very High Landslide Hazard Areas (ACC 16.10.080). For accuracy, some of the 40 percent slopes occurring on-site were the result of grading for construction of Evergreen Way SE and these resultant roadway side slopes are shown paralleling both sides of the roadway on this Exhibit. The construction of public facilities (such as roads) within a critical area are governed by a different approval process, criteria, and decision by the Hearing Examiner under ACC 16.10.170 (Special exception for public agencies and utilities) and do not require a variance by this applicant. Due to the substantial grade change across the site and slope to the northeast, and the presence of two stream courses and wetlands there are unique physical conditions consisting of exceptional topographical or other physical conditions peculiar to and inherent to the Site; and that, as a result of such unique physical conditions, practical difficulties and hardships arise in complying with provisions of this title. City staff have requested several project revisions of the Applicant to carefully evaluate, at least a conceptual level, the preliminary plat’s consistency with city standards for maximum road grade, for water pressure zones, and impoundment for stormwater pond side slopes, among the other elements that are made more complicated by steep slopes. The City’s critical area regulations also require the use of “mitigation sequencing” (ACC 16.10.020) which requires avoiding alteration of regulated critical areas, prior to implementing other form of mitigation. Staff finds the request meets the criterion. B. The variance is the minimum necessary to accommodate the building footprint and access; Applicant’s Analysis: Variance for Road F, Tract I, and Lots 71 through 73: “Response: Apex Engineering indicates that the variance includes a standard Road F road width and lot size in accordance with City of Auburn code. These design features are the minimum required in accordance with the Code.” Variance for Lots 7 & 8 and Tract A: “Response: Apex indicates that the cuts that will result in a 50 percent slope are the minimum to accommodate Lots 7 and 8.” Staff Analysis: Per the ‘Staff Analysis’ of compliance with ACC 18.70.010(A)(1) criteria above, strict conformity with the prohibition on alteration of slopes 40 percent or greater would preclude construction of Road F and the proposed connection to the adjacent approved preliminary plat of Forest Glen. If the roadway connection cannot be constructed, this plat and the adjacent 284 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 30 plat cannot meet City standards for the provision of a second access, the length of dead-end streets and for utility connections. In the case of Lots 7 & 8, and Tract A, the proposed construction exceeds the minimum necessary to accommodate the building footprint and access. The length of Road G to the west could be shortened and fewer lots proposed and avoid alteration of the slopes exceeding 40 percent. Staff finds the request meets the criterion in the case of Road F, Tract I, and Lots 71 through 73 and does not meet the criterion for Lots 7 and 8. C.The proposed variance would preserve the functions and values of the critical area, and/or the proposal does not create or increase a risk to the public health, safety and general welfare, or to public or private property; Applicant’s Analysis: Variance for Road F, Tract I, and Lots 71 through 73 “Response: Re-grading of the slopes greater than 40 percent will avoid impacts to Wetland A to preserve wetland function. A slope stability analysis follows to show an acceptable factor of safety to avoid creating or increasing a risk to public health, safety and general welfare or to public property associated with the proposed Road F, Lots 71 through 73 and Tract I.” Variance for Lots 7 & 8 and Tract A: “Response: The proposed cut and benching (terracing) will locally increase the slope to 50 percent immediately adjacent to the boundary of the Lakeland Hills Division No. 8 similar to the condition that already exists upslope of proposed Lot 6 and south of Evergreen Way SE that crosses the northern boundary of the Lakeland Hills Division No. 8. The existing drainage and function of the slope will be preserved. No risk to public health, safety and general welfare or to public or private property is anticipated from the development of Lots 7 and 8.” Staff Analysis: In the case of the variance requested for Road F, Tract I, and Lots 71 through 73 (former Lots 74-77) allowing alteration of slopes greater than 40 percent will avoid impacts to Wetland A to preserve Wetland A and Stream A functions and to provide roadway and utility connection to an adjacent plat while allowing reasonable site development. Lot and storm pond construction are also proposed associated with this roadway construction. A slope stability analysis has been conducted to show an acceptable factor of safety to avoid creating or increasing risk to public health, safety and general welfare or to public property associated with the proposed Road F, Lots 71 through 73 and Tract I, including storm pond construction and maintenance construction on a hillside. Staff finds the request meets the criterion in the case of Road F, Tract I, and Lots 71 through 73 (former Lots 74-77) and does not meet the criterion for Lots 7 & 8 and Tract A. D.The proposed variance would not adversely affect surrounding properties adjoining; Applicant’s Analysis: Variance for Road F, Tract I, and Lots 71 through 73 “Response: No grading is proposed on adjacent properties associated with the development of Road F, Tract I, or Lots 71 through 73. The development of Road F, Tract I, or Lots 71 through 73 is not expected to adversely affect adjoining properties.” 285 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 31 Variance for Lots 7 & 8 and Tract A: “Response: No grading is proposed on surrounding property adjoining the project. The planned grading is not anticipated to adversely affect surrounding properties adjoining including Lakeland Hills Division No. 8 upslope of Lots 7 and 8.” Staff Analysis: In the case of the variance requested for Road F, Tract I, and Lots 71 through 73 allowing alteration of slopes greater than 40 percent will avoid impacts to Wetland A to preserve Wetland A and Stream A functions and to provide roadway and utility connection to an adjacent future plat of Forest Glen allowing reasonable site development. This would not adversely affect surrounding properties adjoining but benefit adjacent property. In the case of Lots 7 & 8 and Tract A, the proposed construction will alter the neighborhood character by creating very restricted footprint areas for the future home construction within the future Lots 7 and 8 that can be avoided. The proposed construction will alter the neighborhood character through proposed clearing of existing forest vegetation to regrade to 2 horizontal to 1 vertical (2H:1V) and terracing the hillside above Lots 7 & 8. This clearing and regrading is proposed for the full width of Tract A uphill to the property line and adjacent to lots in the Plat of Lakeland Hills Division No. 8 (approximately 150 feet). The regrading will remove existing forest vegetation with the potential for increased instability. Approving the variance will likely adversely affect the neighborhood character for the lots of the adjacent plat of Lakeland Hills Division No. 8, to the west, by grading up to the shared property line. Staff finds the request meets the criterion in the case of Road F, Tract I, and Lots 71 through 73 (former Lots 74-77) and does not meet the criterion for Lots 7 & 8 and Tract A. E. Adverse impacts to critical areas resulting from the proposal are minimized; and Applicant’s Analysis: Variance for Road F, Tract I, and Lots 71 through 73 “Response: The development of Road F, Tract I, or Lots 71 through 73 avoids impact to Wetland A and locally regrades the slope greater than 40 to 50 percent with a minimum road width and lot size accordingly. We provide a slope stability analysis and provide preliminary concepts for a design to increase slopes greater than 40 percent locally to 50 percent.” Variance for Lots 7 & 8and Tract A: “Response: The proposed 50 percent slope grading in localized areas with existing slopes greater than 40 percent to develop lot area for Lots 7 and 8 is the minimum grading activity necessary.” Staff Analysis: In the case of the variance requested for Road F, Tract I, and Lots 71 through 73 allowing alteration of slopes greater than 40 percent will avoid impacts to Wetland A to preserve wetland A and Stream A functions and to provide roadway and utility connection to an adjacent plat while allowing reasonable site development. In the case of Lots 7 & 8 and Tract A, the proposed construction exceeds the minimum necessary to accommodate the building footprint and access. The length of Road G to the west could be shortened and fewer lots proposed and avoid alteration of the slopes exceeding 40 percent. 286 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 32 Staff finds the request meets the criterion in the case of Road F, Tract I, and Lots 71 through 73 (former Lots 74-77) and does not meet the criterion for Lots 7 & 8 and Tract A. F. That the special circumstances and conditions associated with the variance are not a result of the actions of the applicant or previous owners. Applicant’s Analysis: Variance for Road F, Tract I, and Lots 71 through 73 “Response: These specific circumstances or conditions affecting the property are the result of natural processes that created the physical conditions at the site (as described above) and are not the result of actions of the applicant or previous owner.” Variance for Lots 7 & 8 and Tract A: “Response: These specific circumstances or conditions affecting the property are not the result of actions of the applicant or previous owner.” Staff Analysis: In the case of the variance requested for Road F, Tract I, and Lots 71 through 73, staff concurs that the special circumstances and conditions associated with the Variance are related to result of natural processes that created the physical conditions at the site. And these special circumstances and conditions are not the result of actions of the applicant or previous property owner. In the case of Lots 7 & 8 and Tract A, the proposed construction exceeds the minimum necessary to accommodate the building footprint and access and thus the need for the variance is created by the proposed actions of the property owner. Staff finds the request meets the criterion in the case of Road F, Tract I, and Lots 71 through 73 and does not meet the criterion for Lots 7 & 8 and Tract A. V. STAFF RECOMMENDATION - VARIANCE FROM CRITICAL AREA REGULATIONS (File No. VAR16-0001): 1. Staff recommends approval of the Variance from the city’s critical area requirements that prohibit alteration of Class IV Landslide Hazard Areas (ACC 16.10.100(E)(2)) for the proposed grading and alteration of Class IV Landside Hazard Areas near the south-central portion for “Road F”, Lots 71 through 73 and within “Tract I” (storm drainage tract). 2. Staff recommends denial of the Variance from the city’s critical area requirements that prohibit alteration of Class IV Landslide Hazard Areas (ACC 16.10.100(E)(2)) for the proposed grading and alteration of Class IV Landside Hazard Area within the southwest corner of the Plat for Tract A, (Open Space) and the adjacent Lots 7 & 8 and Tract A. 3. In the event the variance from the city’s critical area requirements that prohibit alteration of Class IV landslide hazard areas is approved, and grading of Lots 7 & 8 and Tract A is allowed to address a low static factor of safety and eliminate potential for groundwater surfacing at grade, installation of a permanent drainage dewatering trench system is required. VI. CONCLUSIONS - VARIANCE FROM ZONING CODE MINIMUM DENSITY STANDARD (File No. Not Applicable) 1. On July 14, 2016 a letter request was filed by James E. Kirkebo III of Apex Engineering, PLLC on behalf of Randall Jackson, as Manager of JDH Investment Group Corporation requesting a 287 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 33 “Modification to Plat Standards” under ACC 17.18 for an exception to the minimum density standard of the R5, Residential zoning district (Exhibit 21). 2.Table 18.07.030 (Residential Development Standards) of the City Code specifies the R5, Residential zoning district permits a minimum of 4, and a maximum of 5 dwelling units per acre for the Site. The request seeks to reduce the number of dwellings below this minimum standard. 3.The site is 79.44 acres or 3,460,427 square feet (SF) as specified by the application materials and King County Assessor’s website data. Auburn City Code (ACC) 18.02.065 guides the density calculations for development. City regulations provide for a minimum and base (maximum) density for the R5 Residential zone of 4 and 5 dwelling units per net acre, respectively. As depicted on Sheet 1 of the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016. The gross acreage less deductions yields a “net acreage” of 2,801,098 sq. ft. (or 64.30 acres). This “net acreage” yields a base (maximum) density of 322 dwelling units for the Site based on 5 dwelling units per acre. This net acreage also yields a minimum density of 238 dwelling units based on 4 dwelling units per acre. The Project proposes 200 dwelling units (or lots); which yields approximately 3.35 dwelling units per net acre according to information shown on Sheet 1 of the: Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016. 4.Auburn City Code (ACC) Sections 17.18.005 and 17.18.010, prescribe a process for relief from adherence to any standard established or referenced by Chapter 17.14 ACC or established or referenced the City’s Engineering Design Standards and City’s Engineering Construction Standards (documents) when associated with the city’s review of a preliminary plat, as follows. This request for relief when not associated with a preliminary plat is referred to as a “deviation”. “17.18.005 Purpose. This chapter details methods of modifying standards or specifications of either a formal subdivision or a short subdivision and the findings of fact that must be made to approve such modification.” “17.18.010 Formal subdivisions. A. The hearing examiner may approve a modification of any standard or specification established or referenced by Chapter 17.14 ACC or established or referenced in the city’s design standards or construction standards, upon making the findings of fact in ACC 17.18.030; provided, that the hearing examiner shall obtain the concurrence of the city engineer for any requests to modify any city of Auburn design or construction standard.” “B. The request for modification shall be processed simultaneously with the preliminary plat and the applicant shall submit the modification on forms provided by the department.” 5.ACC Section 17.18.030 specifies the approval criteria for modifications to the standards, as follows: “17.18.030 Findings of fact. A. Such modification is necessary because of special circumstances related to the size, shape, topography, location or surroundings of the subject property, to provide the owner with development rights and privileges permitted to other properties in the vicinity and in the zoning district in which the subject property is located; B. That, because of such special circumstances, the development of the property in strict conformity with the provisions of this title will not allow a reasonable and harmonious use of the property; 288 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 34 C. That the modification, if granted, will not alter the character of the neighborhood, or be detrimental to surrounding properties in which the property is located; D. Such modification will not be materially detrimental to the implementation of the policies and objectives of the comprehensive land use, transportation and utility comprehensive plans of the city; E. Literal interpretation of the provisions of this title would deprive the applicant of rights commonly enjoyed by other properties in the same zoning district; F. The approval of the modification will be consistent with the purpose of this title; G. The modification cannot lessen the requirements of the zoning ordinance. Any such modification must be processed as a variance pursuant to ACC 18.70.010.” (Emphasis added) Due to this last criterion, while a “modification to Plat Standard” was requested by the Applicant, the request for relief from a standard that is contained in the zoning code (such as the minimum density specified in Table 18.07.030 (Residential Development Standards)) must be processed as a “Variance”. 6. ACC 18.70.010(A), “Variances”, specifies that the Hearing Examiner may approve, or modify and approve an application for a Variance if the application satisfies all of the approval criteria specified in ACC 18.70.010(A)(1) thru ACC 18.70.010(A)(10). What follows is staff analysis of this Variance application’s compliance with each criterion. The criteria are listed below in italics, followed by a staff analysis. A. That there are unique physical conditions including narrowness or shallowness of lot size or shape, or exceptional topographical or other physical conditions peculiar to and inherent in the particular lot; and that, as a result of such unique physical conditions, practical difficulties or unnecessary hardships arise in complying with provisions of this title. Staff Analysis: As previously noted in response to the criterion of the critical areas variance, the majority of the existing site is undeveloped and mainly forested and contains wetlands in the northeast, lower portion of the site. There is approximately 150 feet of fall in elevation from the north to the south and approximately 201 feet of fall in elevation from the west to the east. The Site’s topography is shown on the “Critical Slope Exhibit”, Sheet 26 of 26 as part of the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016 (Exhibit 6). According to this Exhibit the site consists of slopes in the following ranges: • approximately a third of the site is slopes between 15 - 25 percent; • approximately a quarter of the site consists of slopes between 25 - 40 percent; and, • approximately eight percent of the site consists of slopes greater than 40 percent slopes. Due to the substantial grade change across the site and slope to the northeast, and the presence of two stream courses and several wetlands, there are unique physical conditions consisting of exceptional topographical or other physical conditions peculiar to and inherent to the Site; and that, as a result of such unique physical conditions, practical difficulties and hardships arise in complying with provisions of this title. City staff have requested several project revisions of the Applicant to carefully evaluate, at least a conceptual level, the preliminary plat’s consistency with city standards for maximum road grade, for water pressure zones, and impoundment for stormwater pond side slopes, among the other elements that are made more complicated by steep slopes. The City’s critical area regulations also require the use of “mitigation sequencing” (ACC 289 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 35 16.10.020) which requires avoiding alteration of regulated critical areas, such as the on-site streams and wetlands prior to implementing other form of mitigation. Staff finds the request meets the criterion. B.That, because of such physical conditions, the development of the lot in strict conformity with the provisions of this title will not allow a reasonable and harmonious use of such lot. Staff Analysis: Per the ‘Staff Analysis’ of compliance with ACC 18.70.010(A)(1) criteria above, strict conformity with the minimum density standard of four dwelling units per net acre does not allow for reasonable and harmonious residential development of the Site. Residential development is the reasonable use of a Site zoned R5, which is “intended to create a living environment of optimum standards for single-family dwellings.” The proposed Project proposes to meet or is capable of meeting the zoning standards, more specifically, the plat meets or is cable of meeting R5 zoning district development regulations specified in ACC Section 18.07.030, except for the minimum density standard. A comparison of the project to the city standards is as follows: Development Standard Standard of the R5 Zone Standard as Proposed by the Project Minimum lot width 50 ft. 50 ft. Minimum lot area per dwelling unit 6,000 sq. ft. 6,000 sq. ft. Minimum average lot area per dwelling unit 8,000 sq. ft. SF 8,791 sq. ft. If the variance were not approved, project modifications to increase the lot and dwelling unit count likely would result in not achieving other zoning standards, such as lot width and minimum lot area. Staff finds the request meets the criterion. C.That the variance, if granted, will not alter the character of the neighborhood, or be detrimental to surrounding properties in which the lot is located. For nonconforming single-family homes, this finding is determined to be met if the features of the proposed variance are consistent with other comparable features within 500 feet of the proposal. Staff Analysis: The Variance is not anticipated to alter the character of the neighborhood or be detrimental to surrounding properties since the site is bordered on at least two (2) sides by properties that consist of more level sites and were developed under different zoning standards. The currently developed single family residential subdivisions located to the east were developed under the city’s Planned Unit Development (PUD) standards in effect at the time. The PUD standards yielded lots in the approximately 4,000 to 5,000 square foot range and a density of overall density of 4.17 units per acre, according to the staff reports prepared for those subdivisions. Since the earlier division of the Kersey III project was proposed as a PUD, smaller lot sizes than typical zoning standards were allowed. The subdivisions located uphill to the west, Lakeland Hill Divisions 8, 9, and 10, were developed under the City’s former R2, Residential (6,000 square foot minimum lot size). These more level sites 290 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 36 are developed with similar lots sizes. The requested variance is not anticipated to be detrimental to other surrounding properties. Staff finds the request meets the criterion. D. That the special circumstances and conditions associated with the variance are not a result of the actions of the applicant or previous owners. Staff Analysis: The special circumstances and conditions associated with the Variance are related to result of natural processes (slope, wetlands and streams) that created the physical conditions at the site. And these special circumstances and conditions are not the result of actions of the applicant or previous property owner. Staff finds the request meets the criterion. E. Literal interpretation of the provisions of this title would deprive the applicant of rights commonly enjoyed by other properties in the same zoning district. Staff Analysis: Per the ‘Staff Analysis’ of compliance with ACC 18.70.010(A)(1) above, compliance with the literal interpretation of the 4 dwelling per net acre minimum density standard of the R5 zone would deprive the applicant of rights commonly enjoyed by other properties in the same zoning district. The Site’s topography and critical areas results in challenges for configuring roads that meet city maximum grade standards and designing utility systems that operate by gravity, such as sewer and storm drainage and or operate under appropriate pressure such as the water system, for example. The project as originally proposed had more lots but in order to meet other city engineering standards the number of lot was reduced. Project changes during the civil plan review process may further affect the number of lots; however, the number of lots is not expected to increase, and certainly not above the minimum density of 238. Staff finds the request meets the criterion. F. The approval of the variance will be consistent with the purpose of this title and the zoning district in which the property is located. Staff Analysis: The Variance meets the general purposes of Title 18 ACC, “Zoning”, as the reduction in density for the Site does not adversely impact the City’s ability to adequately provide housing for the projected future population growth of the City. The Comprehensive Plan projects a 9,000-household gain between 2010 and 2030. Considering the reduction of 38 dwelling units for the Site, the City is anticipated to accommodate a net 8,962 housing units between 2012 and 2030, handily capable of accommodating housing for the projected growth. Staff finds the request meets the criterion. G. The variance will not allow an increase in the number of dwelling units permitted by the zoning district. Staff Analysis: The R5 zone permits a minimum of 4 and a maximum of 5 dwelling units per acre for the Site. The request seeks to reduce the number of dwellings; rather than increase. With approval of the variance, the project would achieve approximately 3.35 dwelling units per net acre 291 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 37 according to information shown on Sheet 1 of the: Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016. Staff finds the request meets the criterion. H. The authorization of such variance will not adversely affect the comprehensive plan. Staff Analysis: Per the ‘Staff Analysis’ of compliance with ACC 18.70.010(A)(6) above, the Variance does not adversely affect the Comprehensive Plan. Staff finds the request meets the criterion. I. The variance shall not allow a land use which is not permitted under the zoning district in which the property is located. Staff Analysis: The Variance is requested to accommodate a density standard less than the minimum required. It does not propose to affect the land uses that are allowed in the R5, Residential zoning district. Staff finds the request meets the criterion. J. The variance shall not change any regulations or conditions established by surface mining permits, administrative use permits, conditional use permits or contract rezones authorized by the city council. Staff Analysis: The Site has not been subject to any surface mining permits, Administrative Use Permits, Conditional Use Permits, or Contract Rezones authorized by the City Council. Staff finds the criterion does not apply. VII. STAFF RECOMMENDATION – VARIANCE FROM MINIMUM DENSITY STANDARD (File No. Not Applicable) 1. Staff recommends approval of the Variance to reduce the number of dwellings below the minimum density standard of four (4) dwelling units per acre standard of the R5, Residential zoning district (Table 18.07.030 (Residential Development Standards) of the City Code without conditions. VIII. CONCLUSIONS - PLAT MODIFICATIONS FROM ENGINEERING DESIGN STANDARDS 1. As noted in the previous discussion of the density variance, Auburn City Code (ACC) Sections 17.18.005 and 17.18.010, prescribe a process for relief from strict adherence to standards established or referenced by Chapter 17.14 ACC (Improvement Requirements – Subdivisions) or established or referenced in the City’s Engineering Design Standards and City’s Engineering Construction Standards (manuals) when associated with the city’s review of a preliminary plat, as follows. Similar requests for relief when not associated with a preliminary plat are referred to as a “deviation”. 2. On July 14, 2016 the application was modified to include requests for a modification of plat 292 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 38 standards for relief from the Engineering Design Standard as follows (Exhibit 16): Deviation Request #1: Allow four horizontal curves that are less than the minimum radius of 333 feet for a “local residential” classified street. Deviation Request #2: Allow the use of walls on more than three sides in the storm ponds and not require 25% of the pond perimeter to be a vegetated soil slope not steeper than 3:1. Deviation Request #3: Allow a modified street section for a portion of Road B north and south of Evergreen Way SE and a portion of Roads B & C northerly of the intersection of Road F. The intent of the modified street section design is to allow ingress/egress of emergency vehicles and non-emergency vehicles without interference from each other. 3.ACC Section 17.18.030 specifies the approval criteria for modifications to the design or construction standards, as follows: “17.18.030 Findings of Fact. A. Such modification is necessary because of special circumstances related to the size, shape, topography, location or surroundings of the subject property, to provide the owner with development rights and privileges permitted to other properties in the vicinity and in the zoning district in which the subject property is located; B. That, because of such special circumstances, the development of the property in strict conformity with the provisions of this title will not allow a reasonable and harmonious use of the property; C. That the modification, if granted, will not alter the character of the neighborhood, or be detrimental to surrounding properties in which the property is located; D. Such modification will not be materially detrimental to the implementation of the policies and objectives of the comprehensive land use, transportation and utility comprehensive plans of the city; E. Literal interpretation of the provisions of this title would deprive the applicant of rights commonly enjoyed by other properties in the same zoning district; F. The approval of the modification will be consistent with the purpose of this title; G. The modification cannot lessen the requirements of the zoning ordinance. Any such modification must be processed as a variance pursuant to ACC 18.70.010.” 4.Following is staff analysis of each of the deviation requests’ compliance with the criteria of ACC Section 17.18.030. The criteria are listed below in italics, followed by a staff analysis of each request. See also, the separate City Engineer Recommendation (Exhibit 17). A.Such modification is necessary because of special circumstances related to the size, shape, topography, location or surroundings of the subject property, to provide the owner with development rights and privileges permitted to other properties in the vicinity and in the zoning district in which the subject property is located. Staff Analysis: As noted in the earlier staff analysis of the variance requests, the Site contains substantial grade change and contains two stream courses and wetland areas. These are unique physical conditions consisting of exceptional topographical or other physical conditions peculiar to and inherent to the Site; and that, as a result of such unique physical conditions, practical difficulties and hardships arise in complying with the provisions of this title and each of these three standards of the City of Auburn Engineering Design Standards (manual). B.That, because of such special circumstances, the development of the property in strict conformity with the provisions of this title will not allow a reasonable and harmonious use of the property. Staff Analysis: 293 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 39 As noted in the earlier staff analysis of the variance requests, the difficulty in complying is as a result of topographical and other physical conditions peculiar to and inherent to the Site. The roadway curve radius and the need for walls around three sides of the ponds are as a result of designing the project to work with the Site’s slopes. The need for the roadway section modifications to Roads B & C is to accommodate a road network that meets public access and emergency access needs through wider street segments in the event both needs are required simultaneously. Currently, there is not an opportunity to make a second emergency vehicle access via another direction due to development status or grades of adjacent sites. A future connection of Road B is proposed where future extension is reasonably foreseeable. C. That the modification, if granted, will not alter the character of the neighborhood, or be detrimental to surrounding properties in which the property is located. Staff Analysis: As noted in the earlier staff analysis of the variance requests, the approval of the three Modifications are not anticipated to alter the character of the neighborhood or be detrimental to surrounding properties since the site is bordered on at least two (2) sides by residential subdivisions that consist of more level sites that were developed under different zoning standards. D. Such modification will not be materially detrimental to the implementation of the policies and objectives of the comprehensive land use, circulation and utility plans of the City. Staff Analysis: All of the above modifications to the City of Auburn Engineering Design Standards (manual) have been reviewed by Transportation and Utilities staff and by the City Engineer and will not be materially detrimental to surrounding properties nor to public safety (Exhibit 17). Consequently, approval of the three Modifications is also consistent with the Comprehensive Stormwater Drainage Plan and the Comprehensive Transportation Plan policies of providing stormwater management, preserving neighborhood continuity and cohesiveness and provisioning of a safe transportation system. E. Literal interpretation of the provisions of this title would deprive the applicant of rights commonly enjoyed by other properties in the same zoning district. Staff Analysis: The site is bordered to the east and west by residential subdivisions that consist of more level sites and were previously developed with single family residences. Both sites were under different city zoning and engineering standards than the subject Site due to the timing difference. However, the subdivision to the east was evaluated in the same environmental review documents(EIS’s), as the subject proposal and has been anticipated for residential development for many years and the earlier divisions have been allowed. F. The approval of the modification will be consistent with the purpose of this title. Staff Analysis: The approval of the three Modifications will be consistent with purpose of Title 17, the ‘Land Adjustments Divisions Ordinance’. The requested Modifications meet the functional and safety objectives of the City’s Engineering Design Standards. See also the “Staff Recommendation for Modification of Plat Standards – Engineering Design Standards”, City of Auburn, January 18, 2017 (Exhibit 17). G. The modification cannot lessen the requirements of the zoning ordinance. Any such modification must be processed as a variance pursuant to ACC 18.70.010. Staff Analysis: 294 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 40 The three requested Modifications to the Engineering Design Standards (manual) do not lessen requirements of the zoning ordinance. IX. STAFF RECOMMENDATION – PRELIMINARY PLAT APPLICATION, PLT14-0006 1. Staff recommends approval of this Preliminary Plat, of Diamond Valley Estates, based upon compliance with the project description and application materials as provided in the Preliminary Plat application (File No. PLT14-0006) and the Conditions of Approval set forth below. The recommendation includes partial approval of the requested Variances (for approval of the zoning minimum density standard, and partial approval of the critical areas variance for alteration of Class IV Landslide Hazard Areas) and approval of the requested three Modifications of Plat Standards from the City’s Engineering Design Standards. Any modifications from the project description, exhibits, timing, or conditions must be reviewed and approved by the City of Auburn for conformity with this approval. Any change from these may require administrative or Hearing Examiner approval of changes to the preliminary plat and/or environmental review. X. CONDITIONS OF APPROVAL- PRELIMINARY PLAT APPLICATION, PLT14-0006 Earth: 1. All approvals and permits related to the Project and issued by the City, including permits related to the construction of single-family residences, shall be consistent with and implement recommendations of the document: Geotechnical Engineering Services and Geomorphology Services, Diamond Valley Estates Development, Auburn WA, GeoEngineers, Rev. April 21, 2016. This shall include approvals and permits related to retaining walls. 2. Site clearing, grading, stabilization, pond, and roadwork shall occur during summer construction season. Prior to issuance of clearing or grading permits or public facility extension (FAC), a grading plan for grading and clearing necessary for both the construction of infrastructure such as roads and utilities and for lot grading shall be prepared, submitted and approved by the City of Auburn. The purpose of the plan is to accomplish the maximum amount of grading at one time to limit or avoid the need for subsequent grading and disturbance, including grading of individual lots during home construction. The plan shall identify the surveyed boundary of the crest slopes for the site's 40% or greater slopes. This plan shall show quantities and locations of excavations and embankments, the design of temporary storm drainage detention system(s), and methods of preventing drainage, erosion and sedimentation from impacting adjacent properties, natural and public storm drainage systems, and other nearby sensitive areas. All the measures shall be implemented prior to beginning on-site filling, grading or construction activities. The applicant's grading plans shall be prepared in conjunction with, and reviewed by, a geotechnical engineer licensed in the State of Washington. The geotechnical engineer shall develop and submit, for the City's review, specific recommendations to mitigate grading activities with particular attention to developing a plan to minimize the extent and time soils are exposed on site and address grading and related activities during wet weather periods (the period of greatest concern is October 1 through March 31). The plans shall show the type and the extent of geologic hazard area or any other critical areas as required in Chapters 16 ‘Structural Design’ and 18 ‘Soils and Foundations’ of the International Building Code (IBC) and/or the Titles 16 ‘Environment’ and 18 ‘Zoning’ of the City of Auburn’s Code. 3. Because of the high likelihood of encountering hillside seeps during earthwork, upon completion of rough grading and excavation, the Applicant shall have a geotechnical engineer licensed in the State of Washington re-analyze the site and determine if new or 295 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 41 additional mitigation measures are necessary. A revised geotechnical report shall be submitted to the City of Auburn for review and approval by the City Engineer. Recommendations for areas where subsurface water is known or discovered shall be given particular attention by the geotechnical engineer and coordinated with the project engineer responsible for the storm drainage system design. 4.To reduce the length of unimpeded high slopes and to collect and reduce the probable impacts of sheet flow on slope faces, installation of benches at least 6 feet wide into the slopes associated with Ponds 1 & 2, Road F and Lot 7 & 8 is required. Maximum vertical spacing between benches shall be 30 feet, as approved by the City Engineer. Groundwater: 5.The Site is located within Groundwater Protection Zones 3 and 4. All approvals and permits related to the Project and issued by the City shall be consistent with best management practices (BMPs) per ACC 16.10.120(E)(1) and (2) and the following from the Surface Water Management Manual (SWMM) at a minimum: BMP C101 – Preserving Natural Vegetation BMP C102 – Buffer Zone BMP C103 – High Visibility Plastic or Metal Fence BMP C120 – Temporary and Permanent Seeding BMP C153 – Material Storage, Delivery, and Containment BMP C160 – Certified Erosion and Sediment Control Lead 6.Prior to issuance of a grading permit additional analysis is required to be submitted to the city for review and approval to assess the magnitude of the temporary and permanent dewatering that is/will be required. All permanent dewatering shall be designed to ensure long term, low cost, minimal maintenance. The Applicant shall provide a detailed description of the required maintenance, frequency and how the facilities will be accessed, prior to permit issuance, including accessibility for long-term maintenance. Wetlands/Streams 7.The Wetland Assessment, Diamond Valley Estates Auburn WA, Raedeke Associates Inc. April 8, 2014, identifies that alteration of site wetlands and streams may be subject to jurisdiction of the Army Corps of Engineers (COE) and the Washington Dept. of Ecology (WDOE) and alteration of the site streams (including changes in flow) is subject to the jurisdiction of the Washington Dept. of Fish and Wildlife (WDFW). Concurrent with the review of land clearing, grading, or public facility extension (FAC) approvals, a final wetland/stream mitigation plan is required to be prepared and submitted to the city for review and approval. The plan shall address the wetland and stream classification, functions, and values, and shall ensure consistency with the purpose and intent of the city’s critical areas regulations consistent with ACC 16.10, and include copies of permits and correspondence with Army Corps of Engineers and Department of Ecology, related to permitting or exemption, as applicable. The mitigation plan shall be reviewed and approved prior to clearing, grading, or permit approval and issuance. The mitigation plan shall be part of the approved construction plan set. The mitigation plan shall include the following: a.Stream channel conditions shall be monitored during the course of wetland/stream mitigation implementation and long-term monitoring to determine whether conditions have changed from pre-developed conditions or new erosion is occurring. The final mitigation plan shall provide for a contingency plan that identifies site-specific mitigation measures to protect the channel and prevent further erosion, as appropriate, in consultation with the project geotechnical engineer, civil engineer, and 296 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 42 the City of Auburn, depending on the location and observed conditions. Such measures could include “soft” armoring with additional plantings or large woody debris, or “hard” armoring as suggested by GeoEngineers, Inc. (2016). If headcutting is observed in the stream reaches where the gradient increases, it is not clear b. whether “soft” armoring would be effective in preventing further erosion. If one of the “hard” armoring measures identified by GeoEngineers, Inc. (2016) is deemed necessary, this would likely require additional permits from the U.S. Army Corps of Engineers, WDFW, and City of Auburn. c. Pre-developed photos and reports shall be provided for the existing condition of the wetlands and stream channels along with a mitigation plan on the monitoring and process to address potential impacts created by the development, consistent with the City’s Critical Areas Ordinance. Plants: 8. To mitigate for aesthetic and wildlife impacts and support slope stability, due to the removal of significant trees and creation of steep slopes, a revegetation plan shall be prepared meeting the minimum "Best Management Practices" per Washington State Department of Ecology guidance for planting native vegetation on steep slopes. The plan shall be prepared by a plant biologist (or other professional with equivalent degree) in consultation with the geotechnical engineer. The plan shall be prepared and submitted for city review and approval by Planning Director identifying how disturbed portions of slopes, including those necessary for the construction of utilities and any other improvements, shall be landscaped/revegetated and stabilized. The proposal shall also identify measures to be taken for native vegetation retention during the construction process, include an installation schedule for landscaping/native revegetation, and define the overall restoration approach. The plan shall also address responsibility for long term retention of vegetation. Prior to final plat approval, the applicant shall post a financial guarantee, in a form acceptable to the City, that ensures that newly planted hillside restoration vegetation will survive according to approved performance standards for a minimum three-year period (including a minimum of two full growing seasons) following planting and so that dead and unhealthy trees shall be promptly replaced. Language shall be recorded as part of the final plat and as part of restrictive covenants indicating that the property owner shall, where applicable, be responsible for maintenance and retention of trees/vegetation on individual lots, if appropriate, and the Homeowner's Association responsible for maintenance and retention of vegetation in areas held in common. 9. Dispersion Trenches, if utilized, shall avoid/minimize disturbance of native vegetation in and around the dispersion trenches. Aesthetics: 10. The Developer will be required to enter into an agreement or submit a declaration of Conditions, Covenants, and Restrictions (CC&Rs), enforceable by the City, in a manner acceptable to the City, to ensure the long term maintenance by the Homeowners Association (HOA) of the open space tracts and areas necessary to meet sight distance standards prior to issuance of final plat approval. 11. Proposed Conditions, Covenants and Restrictions (CC&Rs) for the future Homeowners' Association shall be submitted for review and approval by the City prior to final plat approval. This document shall specify the financial means of maintenance of all common tracts and open spaces by the HOA. 12. The final design of the landscaping shall be generally consistent with the Diamond Valley Estates Landscape Plan, Sheet L1 and L2, Bradley Design Group, Inc., March 19, 2014, July 297 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 43 11, 2016. The landscape plan shall be included with the civil plans (public facility extension and grading) and may require revisions to meet code requirements and to coordinate with other site improvements. 13.Any plat entrance signage shall be a low monument style with accenting landscaping. The number, style, placement of signs and associated landscaping shall be approved by the Planning Director meeting Chapter 18.56 ACC (Signs). 14.Fencing along the boundary of the plat shall be of consistent material, style, and color. The Planning Director shall approve such fences, which shall be equivalent to a 6 ft. high solid wood fence. Any fencing to be erected adjacent to any of the pedestrian pathways or leading to the open space tracts shall also be submitted to the Director for approval and may be different. 15.Compliance with all the mitigation measures as noted on Pages 9 - 19 of the "Kersey Ill Preliminary Plat Final EIS" City of Auburn, February 11, 2005 and as otherwise noted throughout the document is required Historic/cultural preservation: 16.In the event ground disturbing activity results in the discovery of resources with potential historical, cultural and/or archeological significance, work shall be stopped in a large enough area to maintain integrity of the discovery and appropriate local, State and tribal offices shall be notified immediately. Transportation: 17.While the document, School Access Analysis Diamond Valley Estates, Apex Engineering PLLC, undated, identifies that the Auburn School District serves this Site, and anticipates providing school bus service to the proposed plat based on distance to schools, prior to approval of the civil plans (public facility extension and grading), the applicant shall consult with the Auburn School District Transportation Coordinator to determine if the plat construction shall include a pick-up/drop-off area from Evergreen Way SE to avoid school buses having to enter the plat. The results of the consultation shall be shared with the City and any necessary revisions to the plat made. 18.A note shall be placed on the Final Plat indicating that there shall be no direct access to Evergreen Way SE from the individual lots of the plat. 19.Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the plans shall show that appropriate portions of public streets shall be posted no- parking on the appropriate portions of the streets due to its road width or presence of medians. Also, the cul-de-sacs shall be posted “No Parking” around their entire perimeter. Posting shall be in accordance with ACC 10.36.175. 20.As condition of preliminary plat approval, It shall be the responsibility of the developer that is extending the public street improvements, to remove the temporary cul-de-sac on adjacent plats, at their expense. 21.The following note, or functional equivalent, as determined by the City Engineer, shall be provided on the final plat: "WHEN IT BECOMES NECESSARY, AS PART OF A SUBDIVISION, TO INSTALL A TEMPORARY CUL-DE-SAC PER CITY OF AUBURN DESIGN STANDARDS, THE PORTION OF THE TEMPORARY CUL-DE-SAC ENCROACHING ON THE ADJACENT PRIVATE PROPERTY SHALL BE PLACED IN A TEMPORARY EASEMENT DEDICATED TO THE CITY OF AUBURN. THE TEMPORARY EASEMENT SHOWN ON THE LOTS IS HEREBY RESERVED, GRANTED AND CONVEYED TO THE CITY OF AUBURN FOR TEMPORARY 298 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 44 PUBLIC ROADWAY PURPOSE, UPON THE RECORDING OF THIS PLAT. THE CITY OF AUBURN IS HEREBY RESPONSIBLE FOR THE MAINTENANCE OF THE TEMPORARY PUBLIC ROADWAY FACILITIES WITHIN SAID EASEMENT. UPON THE CONSTRUCTION OF AN EXTENSION OF THE STREET, AND WHEN DETERMINED BY THE CITY OF AUBURN THAT THE TEMPORARY CUL-DE-SAC IS NO LONGER REQUIRED, IT SHALL BE THE RESPONSIBILITY OF THE DEVELOPER THAT IS EXTENDING THE PUBLIC STREET IMPROVEMENTS, TO REMOVE THE TEMPORARY CUL-DE-SAC AT THEIR EXPENSE. IN CONJUNCTION WITH TEMPORARY CUL-DE-SAC REMOVAL, THE DEVELOPER SHALL ALSO FINISH CONSTRUCTION OF THE PUBLIC STREET WITHIN THE TEMPORARY CUL- DE-SAC AREA IN ACCORDANCE WITH THE CITY OF AUBURN DESIGN STANDARDS APPLICABLE TO THE STREET CLASSIFICATION, AS WELL AS ANY PRIVATE IMPROVEMENTS AND PROPERTY RESTORATION THAT MAY BE NECESSARY ON ADJACENT LOTS AFFECTED BY THE REMOVAL OF THE TEMPORARY CUL-DE-SAC. THE TEMPORARY EASEMENT SHALL AUTOMATICALLY TERMINATE UPON REMOVAL OF THE TEMPORARY CUL-DE-SAC IMPROVEMENTS, AS APPROVED BY THE CITY OF AUBURN." 22. Consistent with City Comprehensive Plan Policy (Policy TR-130) for pedestrian connectivity, during civil plan review, the City will evaluate whether Tract D, a shared access and utility tract, is capable of being extended north to connect to Evergreen Way SE to provide a public pedestrian connection and shorter walking route for school age children to bus stops and pedestrians to the adjacent subdivision of Kersey III, Division 2. If feasible, as determined by the City Engineer, this construction shall be shown on the civil plans and contain appropriate easement provisions provided on the Final Plat. 23. The Facilities Extension Agreement (FAC) shall include the design of the mini roundabout at the intersection of Roads B, C and F as identified in Exhibit 23 – Diamond Valley Estates Road B at Road F/C Mini Roundabout Design Report, Transportation Solutions Inc., November 8, 2016, as reviewed and accepted by the City Engineer. Public services: 24. Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the construction plans shall show that the water system design is sufficient to demonstrate any portion of a future proposed structure is within 300 feet of a fire hydrant. 25. Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the construction plans shall show conformance with International Fire Code standards for fire apparatus access roads, generally as follows: • Road G (including Tracts B, C, and D): lots requiring residential fire sprinklers include Lots 3-12 and 16-35; • Road C (including Tract J): lots requiring residential fire sprinklers include Lots 135-181. To eliminate the second remote access requirement for development of over 30 dwelling units; Exception 1, residential fire sprinkler systems (RFS) can be used in the following areas of the development. Note that, if at time of dwelling construction, the secondary access road is accessible from the future development, Exception 2 can be evaluated. At this time, however, residential fire sprinkler system will be required in the following areas of the development: • Road B: lots requiring residential fire sprinklers include Lots 86-132 • Road F: lots requiring residential fire sprinklers include Lots 68-81. 299 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 45 Utilities: 26.Prior to Final Plat Approval, the applicant shall create from “Tract I” separate tracts to contain only Storm Pond 1 and Storm Pond 2, said new tracts to be owned by the City, and “Tract I” to be under the ownership and maintenance of the HOA. 27.Prior to the approval of the construction plans under the Facilities Extension Agreement (FAC), the applicant shall work with the appropriate regulatory agencies to determine if Stormwater Ponds 1 and 2 are subject to the provisions of Washington State Dam Safety and provide this correspondence to the City. If Dam Safety requirements apply, the Applicant shall also secure the necessary permits and comply with the State regulations for dams on the construction plans. 28.Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), provide documentation of application to the Washington State Department of Ecology (WSDOE) for a General Storm Permit, as required for all projects over 1 acre in size. 29.Benching of the graded slopes above developed storm drainage facilities (i.e., roads, ponds, and homes) is required for protection of the proposed facilities. Benches shall be at least 6 feet wide. Maximum vertical spacing between benches shall be 30 feet, as referenced on Page 44 of the Geotechnical Engineering Services and Geomorphology Services, Diamond Valley Estates Development, Auburn WA, GeoEngineers, Rev. April 21, 2016 and as reviewed and accepted by the City Engineer. 30.Sheet 22 of Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016 shows fill slopes that are not keyed in. Special attention should be made in the design of fill slopes to prevent failure. Prior to the approval of civil plans provide design recommendation from the geotechnical consultant on the keying-in of fill slopes on this project and as reviewed and accepted by the City Engineer. 31.Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the Conceptual Utility Plan, Sheets 14 and 15 of Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016, shows steep storm pipe runs, and, as a result, appropriately designed energy dissipation features are required at the end of long runs of pipe, at pipe intersections, and at the inlet/outlet to the storm drainage ponds. 32.A note shall be placed on the Final Plat indicating that the Diamond Valley Estates Homeowner’s Association and its heirs and successors shall maintain those portions of the tracts containing stormwater ponds and specifically the portions located outside the fenced pond boundaries, or if no fence is provided, outside the 10-year storm water surface elevation, as determined by the City Engineer. Additionally, the Covenants, Conditions, and Restrictions (CC&Rs) to be reviewed by the City shall also address this maintenance responsibility. 33.The building permit applications for the individual lots shall identify that all residential stormwater downspout connections and footing drains shall be tight-lined to the nearest public drainage system and be placed with private drainage easements to be shown and described on the final plat. No runoff will be allowed to run uncontrolled through separately owned lots under the final Site design. 34.Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the construction plans shall show the following for areas of Ponds 1 and 2: Uphill Cut Slope: Temporary dewatering of the hillside above Pond 1 shall occur prior to its construction. A permanent drainage dewatering system shall be included on the 300 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 46 civil plans and installed in “Tract I” near the base of the slope and shall be owned and maintained by the HOA under a maintenance agreement with the City. Downhill Fill Berm: A full liner of the entire pond and slopes is required. A partial liner would allow seepage from the unlined area to bypass the lined part. A permanent drainage dewatering system shall be installed below the outboard fill slope, and shall be owned and maintained by the City. Uphill Cut Slope: Temporary dewatering of the hillside above Pond 2 shall occur prior to its construction. A permanent drainage dewatering system shall be included on the civil plans and installed in “Tract I” near the base of the slope and shall be owned and maintained by the HOA under a maintenance agreement with the City. Downhill Fill Berm: A full liner of the entire pond and slopes is required. A partial liner would allow seepage from the unlined area to bypass the lined part. A permanent drainage dewatering system shall be installed below the outboard fill slope, and shall be owned and maintained by the City. The outboard fill slope of 2H:1V is described on Page 24 of the Geotechnical Engineering Services and Geomorphology Services, Diamond Valley Estates Development, Auburn WA, GeoEngineers, Rev. April 21, 2016. As noted in the Condition above, the Diamond Valley Estates HOA will be responsible for maintenance of these slopes. 35. Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the plans shall show that the stormwater pond access roads for Storm Ponds 1 and 2 shall have a maximum grade of 15% for paved access roads, 7% for gravel access roads. 36. Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the plans shall show that the following condition is applicable to Road F: Uphill Cut Slope: To increase the static factor of safety above 1.00 and eliminate the potential for groundwater surfacing at grade, installation of a permanent drainage dewatering trench system is required. Downhill Existing Slopes: To increase the static factor of safety above the calculated 1.03, installation a permanent drainage dewatering system at the toe of the slope that shall be owned and maintained by the HOA under a maintenance agreement with the City is required. 37. The plat proposes grading and alteration of Class IV Landside Hazard Areas within the southwest corner of the Plat for Tract A, (Open Space) and the adjacent Lots 7 and 8. In the event the variance from the city’s critical area requirements that prohibit alteration of Class IV Landslide Hazard Areas (ACC 16.10.100(E)(2)) is approved, and grading of Lots 7 & 8 and Tract A is allowed, to address a low static factor of safety and eliminate potential for groundwater surfacing at grade, installation of a permanent drainage dewatering trench system that shall be owned and maintained by the HOA under a maintenance agreement with the City will be required. 38. Tracts D (a shared private utility and access tract) and F (a utility tract) shall be owned and maintained by the homeowner’s association or one or more individual lot owners. The portions of the sanitary sewer system located within those tracts shall lie within a public utility easement located completely within those tracts, as shown in the Conceptual Utility Plan, Sheet 14 of Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016. 39. Tract I, as shown on Sheet 1 of Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016 (consisting of wetlands, streams, buffers, storm facilities at the NE corner) contains wetlands and proposed 301 of 350 PLT14-0006, Diamond Valley Estates January 12, 2017 Page 47 storm ponds in addition to the outfall sewer line on a fairly steep slope. On the final plat, the applicant shall dedicate to the City of Auburn a 30' sewer easement, centered on the sewer pipe as constructed, across the proposed Tract I. That portion of Tract I is to be owned and maintained by the HOA. 40. From the Conceptual Utility Plan, Sheets 14 and 15 of Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016, it appears that the required separation between utilities (mostly sewer and water) has not been ensured within the roadways, specifically on curved portions of Road B and Road F. Prior to City approval of construction plans, the civil plans (FAC) must show that the required separation is not prevented by the proposed road geometry. If relief from this standard is needed, the Hearing Examiner agrees to delegate authority to the City Engineer to decide if a deviation from the Engineer Design Standards (manual) will be allowed. Staff respectfully reserves the right to supplement the record of the case to respond to matters and information raised subsequent to the writing of this report. 302 of 350 BEFORE THE HEARING EXAMINER FOR THE CITY OF AUBURN Phil Olbrechts, Hearing Examiner RE: Diamond Valley Estates Preliminary Plat, Variance and Street Standard Modifications PLT14-0006; VAR16-0001 FINDINGS OF FACT, CONCLUSIONS OF LAW AND FINAL DECISION INTRODUCTION The applicant requests approval of a preliminary plat for a 200-lot single-family residential subdivision of a 79.45-acre parcel located on the north and south sides of Evergreen Way SE, between Quincy and Udall Ave SE. The applicant also requests a variance to build a road and do some grading within a Class IV Landslide Hazard and a variance to the applicable minimum four units per acre density requirement to 3.35 dwelling units per acre. The application further requests approval of three deviations to street and stormwater engineering standards. The preliminary plat, density variance and engineering deviations are approved. The critical areas variance is denied because approval of a reasonable use exception, not variance, is required for building within a Class IV Landslide Hazard Area. For the proposed landslide hazard area encroachments, the application is conditioned upon acquiring approval of the requisite reasonable use waivers, or in the alternative removing the proposed encroachments. The legal basis for denying the critical area variance is outli ned in Conclusion of Law No. 3. The parties are encouraged to request reconsideration if they have a compelling alternative code interpretation. ORAL TESTIMONY Jeff Dixon, principal City of Auburn planner, summarized the proposal. Mr. Dixon introduced revisions to staff recommended conditions No. 14, 33 and 34. In response to examiner questions, Mr. Dixon confirmed that the proposed subdivision would represent the final buildout of the project area covered by the EIS and that the preferred alternative in the EIS contemplated 700 lots and the proposed buildout totaled less than 600 lots. Mr. Dixon explained that the reasonable use waiver was not used in lieu of the variance for work in the landslide hazard areas because the reasonable use process only applies to development proposals where the applicant would be denied all reasonable use if the development proposal were denied. The road stub required for the Forest Glen subdivision will allow for alternative access to the Diamond Estates Information Provided by Jeff Parks on 09.30.19 303 of 350 EXHIBIT 12 Subdivision once Forest Glen is developed. Staff concluded that the requested variance for grading at proposed Lots 7 and 8 could destabilize the slope because the geotechnical analysis presented by the applicant wasn’t sufficient to establish that the slopes would be stable long-term. The proposed slope work for Lots 7 and 8 could adversely affect adjoining steep slopes. The City Engineer and other members of the City’s development team were concerned about slope stability. Mr. Dixon noted staff had no objection to requiring mineral resource land notice on the final plat as requested in Ex. 30. James Kirkebo, applicant representative from Apex Engineering, noted that primary access for the property is Evergreen Way. Site topography is one of its prominent features. Slopes range from 15% to 40%. It has a general fall from the west to the east and south to the north. Meeting City density standards and dealing with the slopes at the same time has been a challenge. The site is composed primarily of coniferous and deciduous regrowth trees. There are multiple wetlands, each of which has been delineated, categorized and analyzed. The central wetland will be filled. Proposed on- site mitigation is composed of a replacement wetland at a 2:1 ratio. There are also two streams on site. The zoning standards that apply to the subject property are different than those that applied to the first two divisions of development of the EIS project area. The number of lots was significantly reduced when the applicant decided to increase proposed minimum lot width from 50 feet to 55 feet. The EIS project area anticipated 700 lots. Divisions I and II have only built out 373 units and the applicant is only proposing 200 more lots for a total of 573 lots. The EIS alternative to the 700 lots was 481 lots, so the proposed final build out is in between the two alternatives. The EIS had anticipated 251 specifically for the proposed Diamond Estates project area (Division III). Mr. Kirkebo further stated that the proposal involves roads with five different road classifications. Mr. Kirkebo went over the requested deviations for each of the road classifications as well as proposed driveway access and shared driveway configurations. Mr. Kirkebo noted that the proposal would involve a total of 651,960 cubic yards of cut and 344,420 cubic yards of fill. Total area for replanting and hydro- seeding is 27.81 acres. 19.5 acres of non-disturbed areas will be protected for a total of 47.21 acres of undeveloped property, more than half the property. The project site covers two storm drainage basins. Some roof top drainage will be directed to wetland recharge. The project will have two storm ponds totaling 3.91 acres with a pond volume of 1,550,236 cubic feet storage capacity. City water will be extended from Evergreen Way and will be stubbed to the east. Sewer will be lined in from an existing line to the northeast of the project. A 2.5-acre recreation tract will be provided with grassy areas, picnic areas and a play structure. Pedestrian access is provided from three locations. Mr. Kirkebo noted that the applicant generally supports the conditions of approval. The Lot 7 and 8 variance is not supported by staff. The applicant would like to see that condition massaged so that staff can get additional geotechnical information that wasn’t provided during preliminary plat review. The applicant is confident that it can provide information to assuage staff concerns. Information Provided by Jeff Parks on 09.30.19 304 of 350 Chip Barnett of Geoengineers addressed geotechnical issues for the applicant. Geoengineers was involved with the first two EIS phases since 2002, doing subsurface explorations and geologic mapping. Site conditions include glacially consolidated soils. The soils are composed of sands, gravel, cobbles and other coarse, dense materials. Previously, Geoengineers had done three borings of up to sixty feet deep and 150 feet of drilling. 14 test pits were dug across the site in 2002 with an excavator with depths of 12 feet. In 2013 and 2016 five exploratory borings were done at the project site that ranged from 31 feet to 100 feet. Six additional test pits were also dug with depths of 12 feet. Drilling of 225 feet was performed. A critical areas evaluation of the slopes and a geomorphic stream evaluation were performed to evaluate dispersion from the stormwater ponds. Four monitoring wells were installed in the borings to a maximum depth of 70 feet to monitor groundwater conditions for design of stormwater ponds and development of the site. Herbert Pschunder, geotechnical engineer, noted he started working on the project three years ago. Mr. Pschunder noted that it was his opinion that the proposed work necessitating the variance for Lots 7 and 8 could be done without destabilizing slopes based upon the borings and other soil evaluation done at other parts of the site. In response to examiner questions, he acknowledged that no borings were done directly at Lots 7 and 8. He concluded from the data available from the surrounding area that the slopes had a safety factor of 1.5, which is considered adequately safe for development. Lots 7 and 8 also had an earthquake safety factor of 1.1, which is also considered acceptably safe for development. Eight prior borings had been performed in the project area and the data on soils and slopes from those borings showed that Lots 7 and 8 could be developed without creating any slope or earthquake safety problems. Emmett Pritchard, senior biologist, first started on this project in 2002 as part of the first two divisions. He worked on the wetland classifications and ratings. Wetland 2 is a new wetland that was identified in 2013 and 2014. The new wetland was found based upon the new wetland classification standards not in place for the first two divisions. Wetland D is proposed to be filled. Impacts are unavoidable because it’s in the path of the roadway, whose location is constrained by the location of Evergreen Way and topography. No alternative location was possible given the topography. The applicant has proposed three acres more of stream and wetland buffering than required by City code, or 56% additional area. Wetland and stream hydrology will be maintained by a bypass to the south of the site that will capture water to the south of the site and then tight line it to a dispersion device outside the wetland and stream buffers. Dispersion trenches will also bring in water from roof top runoff and the stormwater facilities. In response to examiner questions, Jack Webb, City Traffic Engineer, responded that the six cul-de-sacs proposed by the applicant are not optimal, but unavoidable due to topography and surrounding development. Information Provided by Jeff Parks on 09.30.19 305 of 350 Tony Theimer, neighboring property owner, asked if the graded slopes bordering the undisturbed areas would be similar to Division II. Mr. Kirkebo responded they would be similar due to the City’s erosion control standards. Mr. Theimer also asked the reason for the No. 3 deviation request. Mr. Kirkebo responded that the reason for the 25% deviation request was necessary to avoid adversely impacting surrounding critical areas. Mr. Theimer asked what signalization would be used for the Evergreen Way intersection. Mr. Webb answered that the intersection would be two two-way stop signs with no controls on Evergreen Way through traffic. Mr. Theimer wanted to know the status of property ownership to the north. He wanted to know what the likelihood was that connections would be made to the north and dump traffic into Kersey Way. He noted it would be beneficial to area residents if Evergreen Way didn’t have to bear the entire traffic generation of the project site. Mr. Kirkebo responded that there are no current development plans for property to the north, however, Road B has been stubbed to provide a connection to the north for an ultimate connection to Kersey Way. Mr. Dixon responded there are no pending applications for development of property to the north. The City also isn’t aware of any development plans. The City does recognize a connection to the north as a viable future connection. He noted that a connection through Forest Glen from the project site will connect to Kersey. Warren Oas, neighboring property owner, wanted to know if the applicant would put a fence along his backyard. Mr. Dixon responded that the Oas property would be along open space tracts where there would be no fencing. There will be no trails in those open space tracts as previously proposed, so fencing isn’t necessary. Mr. Kirkebo confirmed there were no plans to put in trails in the perimeter open space by the Oas property. Mr. Oas also inquired when the project would be done. Mr. Kirkebo responded that the construction permitting for the project is a minimum of nine months and there are summer season constraints on construction. Mr. Kirkebo noted there are currently no definite plans for construction build out. Mr. Oas concluded with stating that there’s a giant rock in the area that historically served as a navigation post when settlers went through the area. Mark Hancock, representing Segale properties, testified he’d like to see a mineral resource land notice placed on the final plat. In response to examiner questions, Mr. Dixon noted that he’s not aware if staff has ever previously made the interpretation that the variance process could be used in lieu of the reasonable process. In rebuttal, Mr. Dixon noted that an archaeological survey has been conducted for the property and the conclusion of the report was there’s low potential for archaeological resources on the property. In rebuttal, Mr. Kirkebo noted the project meets all plat and variance criteria. Information Provided by Jeff Parks on 09.30.19 306 of 350 EXHIBITS The 29 exhibits identified at page 2 of the January 12, 2017 staff report were admitted into the record during the January 25, 2017 public hearing. The following exhibits were admitted into the record during the hearing: Exhibit 30: January 23, 2017 Letter from Mark Segale to Jeff Dixon Exhibit 31: Staff Power Point Exhibit 32: Applicant Power Point Exhibit 33: Applicant proposed condition revisions Exhibit 34: Staff recommended conditions if CAO variance approved FINDINGS OF FACT Procedural: 1.Applicant. The applicant is JDH Investment Group Corporation. 2.Hearing. A hearing was held on the application on June 25, 2017 at 5:30 pm. Substantive: 3.Site/Proposal Description. The applicant requests approval of a preliminary plat for a 200-lot single-family subdivision of a 79.45-acre parcel located on the north and south sides of Evergreen Way SE, between Quincy and Udall Ave SE. The applicant also requests a variance to build a road and do some grading within a Class IV Landslide Hazard and a variance to the applicable minimum four units per acre density requirement to 3.35 dwelling units per acre. The application further requests approval of three deviations to street and stormwater engineering standards. The Diamond Valley Estates project site is undeveloped and located within the Bowman Creek basin on the north slope of the Lake Tapps plateau, south of the White River. The site consists of moderately to steeply sloping terrain. The property is undeveloped and dominated by deciduous, mixed and coniferous forests. In addition to the forested areas, a small area of pasture is in the north-central portion of the site. Most the property appears to have been logged in the 1930’s to 1940’s. The project site faces considerable development challenges because of a multitude of steep slopes. The site consists of a series of north to south oriented ridges and ravines that slope down to the north towards Kersey Way (Staff Report, Figure 2). Elevations of the overall site range from approximately 220 feet above sea level at the northeastern corner of the property to about 570 feet above sea level at the southwest property Information Provided by Jeff Parks on 09.30.19 307 of 350 corner. The site’s topography is shown on the “Critical Slope Exhibit”, Sheet 26 of 26 as part of the Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016. (Exhibit 14). According to Exhibit 14 the site consists of slopes in the following ranges: • approximately a third of the site is slopes between 15 - 25 percent; • approximately a quarter of the site consists of slopes between 25 - 40 percent; and, • approximately eight percent of the site consists of slopes greater than 40 percent slopes. A large amount of grading is necessary because the 200 lots proposed by the applicant will be laid out on three primary tiers of land that will be significantly re-graded from the existing topography. The proposal includes a stormwater drainage system with two detention ponds (Pond 1 and Pond 2) situated near the toes of steep slopes. The two ponds will be partially cut into the slopes, with retaining walls constructed along their uphill boundaries and retaining walls and fill berms constructed along their downslope boundaries. Project impacts were thoroughly assessed as part of a larger, multi-phase 700-dwelling unit residential development called “Kersey IIII Preliminary Plat” in an Environmental Impact Statement (EIS) issued in February 11, 2005. The EIS assessed two development alternatives, one for 700 dwelling units and one for 481 dwelling units. The total project site was composed of three subdivision divisions. The proposal comprises the third and final division. The other two divisions have already been developed for a total of 373 lots. With the final 200 lots for the subject proposal, total buildout will be 573 lots, 127 lots1 less than the 700-dwelling unit alternative assessed in the EIS. The applicant requests two variances to a critical area regulation that prohibits alteration of Class IV Landslide Hazard Areas (ACC 16.10.100(E)(2)). To develop Lots 7 and 8, the applicant proposes grading and alteration of the landslide hazard area within the southwest corner of the plat for Tract A (Open Space) and the adjacent Lots 7 & 8. To construct Road F, the applicant proposes grading and alteration of the landslide hazard near the south-central portion of the plat at “Road F”, Lots 71 - 73, and “Tract I” (a storm drainage tract). The applicant also requests a variance to ACC Table 18.07.030(B), which imposes a minimum density of four dwelling units per acre in the R5 zone. The applicant proposes 3.35 dwelling units per acre. 1 As far as can be ascertained from the record, all lots are limited to development of single family homes, such that the total number of lots corresponds to the total number of dwelling units. Information Provided by Jeff Parks on 09.30.19 308 of 350 The applicant’s three deviation requests are as follows: Deviation Request #1: Allow four horizontal curves that are less than the minimum radius of 333 feet for a “local residential” classified street. Deviation Request #2: Allow the use of walls on more than three sides in the storm ponds and not require 25% of the pond perimeter to be a vegetated soil slope not steeper than 3:1. Deviation Request #3: Allow a modified street section for portions of Road B and Road C, northerly of the intersection with Road F. The intent of the modified street section design is to allow ingress/egress of emergency vehicles and non-emergency vehicles without interference from each other. 4. Characteristics of the Area. The subdivision is surrounded by property zoned and developed for single-family use. The property to the north is currently undeveloped but zoned R5. 5. Adverse Impacts. As conditioned, there are no significant adverse impacts associated with the proposal. More specifically, impacts are addressed as follows: A. Critical Areas. Critical areas on the project site include geologic hazard areas, wetlands, and streams. Impacts to all critical areas are mitigated by buffers and compensation as required by the City’s critical area regulations, so it is concluded that all impacts are sufficiently mitigated. Impacts are more specifically addressed as follows: 1. Streams. The project site contains two streams that flow to the northeast corner of the site. The streams merge off-site and the merged stream then re-enters the project site at the north boundary. The two streams and the merged stream are all classified as Type III streams under the City’s critical area regulations. 2. Wetlands. The project site contains six wetlands totaling 0.7 acres in area. One wetland is rated a Class II wetland, four are Class III wetlands and one is a Class IV wetland under the City’s critical area regulations. All wetlands except one will maintain the buffers required by City code. The applicant proposes to provide more buffering than required by code, providing an excess of approximately 139,400 square feet of additional native forest buffer than required by the City’s standard stream and wetland buffers, an increase of 53% over what is required. As outlined in the section on drainage below, the stormwater system will also maintain predevelopment hydrology with nonpolluted waters. From this information, it is determined that six of the seven wetlands will not be adversely affected by the proposal. Information Provided by Jeff Parks on 09.30.19 309 of 350 As to the seventh wetland, that wetland will be filled by the proposal. The seventh wetland, identified as Wetland D in the applicant’s wetlands report, is the sole Class II wetland of the project site. The filling of the wetland is necessary to construct Road B for access to building lots and installation of utilities. A total of 2,200 square feet of wetland would be filled. As noted in the wetlands report, lost wetland functions that would occur due to the filling of Wetland D would be primarily flood/stormwater control, base flow/groundwater support, and water quality improvement due to the effectiveness of closed depression wetlands such as Westland D in providing those functions. Due to Wetland D’s small size, impacts to other wetland functions such as natural biologic support, overall habitat functions, specific habitat functions are likely to be small relative the levels of functions that are provided by other on-site and nearby off-site wetlands located north of the project site. City regulations require a replacement ratio of 2:1. The applicant is proposing a replacement wetland of the required area within a relatively level pasture at the project site to be hydrated by discharge from one of the stormwater ponds. Hydrology will also be provided by sheet flow from upland buffers and from direct precipitation. The applicant will also install hyrdophytic vegetation within the replacement wetland buffers. The wetlands report concludes that the replacement wetland would compensate for the functions lost by the filling of Wetland D and would provide for improved wildlife habitat functions due to superior connectivity to other wetlands. The staff report does not address the filling of Wetland D. It is unknown whether staff have found the wetland compensation to be acceptable. However, given the staff’s intense review of stormwater impacts to wetlands, See Ex. 18, it does appear that staff reviewed the wetlands report and found its proposed wetland filling and mitigation to be consistent with the City’s critical area requirements. Given these factors, it is determined that the proposal will not create significant adverse impacts to wetlands. 3. Landslide Hazard Areas. Class IV Landslide Hazard Areas are present at the project site in the form of slopes greater than 40%. The applicant has proposed the alteration of two landslide hazard areas at the project site via a critical areas variance application. However, as determined in Conclusion of Law No. 3, the applicant must apply for a reasonable use exception instead of a variance to alter a Class IV Landslide Hazard Area. The conditions of approval of this decision require that the applicant acquire approval of a reasonable use exception or refrain from making alterations to the Class IV areas. Therefore, an assessment of impacts to the Class IV areas is premature at this time. Information Provided by Jeff Parks on 09.30.19 310 of 350 4. Groundwater. The site is located partially in Groundwater Protection Zone 3 and partially in Groundwater Protection Zone 4. As conditioned, the Project shall implement best management practices for water resource protection during construction, as required by City critical areas regulations. B. Drainage. The proposal will not create any adverse stormwater impacts. The applicant has prepared a preliminary stormwater report that staff have determined preliminarily complies with the City’s stormwater regulations. The final details of the proposed stormwater system will be made to conform to applicable standards by City staff as part of final plat review. The City’s stormwater and critical area regulations require that the proposal maintain off-site stormwater flows and velocities at pre-development levels and that critical areas not be adversely affected. More specifically, City of Auburn stormwater standards require that stormwater discharges match developed discharge durations to pre-developed durations for the range of pre-developed discharge rates from 50% of the 2- year peak flow up to the full 50-year peak flow. Compliance with these regulations assures that the proposal will not create any significant adverse stormwater impacts. An off- site drainage analysis was performed for the Kersey III EIS in 2004. As part of the preliminary plat process, a qualitative downstream analysis was performed on September 12, 2013. Additional analysis of the downstream system was prepared by GeoEngineers. This analysis determined that the downstream system will not be adversely affected by the controlled release from stormwater drainage improvements. The applicant’s wetland analysis, Ex. 13, also determined that there would be no increase in runoff volume to streams and wetlands. Further, as testified by the applicant’s wetlands expert, roof top drainage and other nonpolluted stormwater flows will be diverted to the stream and wetlands to maintain predevelopment hydrology. The project site contains two drainage basins. To not create downstream impacts, a detention pond is proposed in each developed basin that outlets to the on-site wetlands. A drainage area south of the project contributes flow to the project and is collected in a bypass pipe that is conveyed to one of the on-site streams. C. Population Allocation. As previously identified, the applicant is requesting a variance to minimum density standards in the R5 district. As determined in the staff report, this will not adversely affect the City’s ability to meet state mandated growth targets. The applicant’s requested reduction in density only results in the net loss of 38 dwelling units. As this is only what appears to be the second request for a density reduction in the last decade, the cumulative impact of such a requested reduction in density is nominal to the City’s ability to absorb growth targets. In addition, staff have Information Provided by Jeff Parks on 09.30.19 311 of 350 determined at page 36 of the staff report that, with reduced density, the City’s zoning standards will accommodate the construction of 8,962 dwelling units between 2012 and 2030, which staff have determined is sufficient to meet growth targets. 6. Adequacy of Infrastructure and Public Services. The proposal will be adequately served by public infrastructure. Stormwater facilities have already been addressed in Finding of Fact No. 5 above. In general, the streets, sidewalks, storm drainage facilities, and sewer mains will be required to meet the City’s Design Standards during engineering review and shall be required to meet and implement those standards prior to final plat approval. These facilities will be reviewed as part of the facility extension, grading, and civil plans to be submitted by the applicant. The following more specifically addresses other infrastructure and services: A. Water. Water service to serve the plat will be provided by the City of Auburn. The applicant will be required to construct connections to the existing 12-inch water lines in Evergreen Way SE, with main line extensions within the rights- of-way and publicly dedicated tracts or easements in the plat. Based on City Utilities Division review of conceptual utility plans, City staff determined that water service is available and capable of serving the site. B. Sewer. Sewer service will be provided by the City of Auburn. The applicant will be required to construct a sewer connection from the terminus of the existing sewer line near the NE corner of the site. This sewer line was previously constructed with the earlier divisions of the Kersey III, Preliminary Plats. Based on City Utilities Division review of the conceptual utility plans, City staff determined that City sewer service is available and capable of serving the site. C. Transportation. Lots will be accessed by publicly dedicated interior roads. Public Works staff have reviewed the proposed road network and found it to preliminarily conform to City standards. It is determined that the proposed interior road network provides for safe and efficient lot access. The roads end in four cul-de-sacs and two stub roads. As testified by the City Engineer, the cul-de-sacs are unavoidable due to the steep topography. Comprehensive Plan Policy TR-66 prohibits cul-de-sac roads longer than 600 feet, but authorizes the City Engineer to permit stub roads over 600 feet along with mitigation as necessary. Proposed stub Road B of the plat is over 600 feet in length. To mitigate for the extra length, the applicant has requested a series of cross- section deviations to Road B to widen travel lanes and thereby provide for safe ingress and egress. The City’s Transportation staff and the Valley Regional Fire Authority (VRFA) found the proposed deviations, in conjunction with staff recommended conditions, to provide safe and sufficient access to the lots served by Road B. Information Provided by Jeff Parks on 09.30.19 312 of 350 Off-site traffic impacts are not addressed in the staff report. There is no direct statement in the record that the City’s Public Works staff reviewed off-site traffic impacts and found them to be adequately mitigated. Page 16 of the final EIS for the Kersey III development, Ex. 9, identifies the off-site improvements necessary to mitigate off-site traffic impacts. Page 5 of the staff report identifies that some of the mitigation measures having been implemented, but the report doesn’t address all the improvements recommended in the EIS. Specifically, it is unknown whether the mitigation in a January 11, 2005 traffic impact analysis addendum has been completed, which includes the addition of auxiliary lanes at 53rd St. SE and Kersey Way and an advance signal warning for the Kersey Way/Evergreen Way intersection. A roundabout is also recommended at Evergreen Way SE and Lakeland Hills Way SE, although this roundabout has been presumably constructed since the EIS recommended condition requires the construction of the roundabout prior to the extension of Evergreen Way to Kersey Way, which the staff report states has been completed. However, staff recommended condition of approval No. 15 requires compliance with all FEIS mitigation measures, which would include installation of all the off-site traffic improvements identified at page 16 of the FEIS. Based on this condition and the comprehensive review of traffic impacts through the EIS project (which was for a larger development, no less), it is determined that the proposal will not create any significant off-site traffic impacts. D. Schools. Adequate provisions for schools are made through the payment of school impact fees at the time of building permit issuance for each lot or as may be deferred per ACC 19.02.070(E). Access for safe school walking routes will be provided by the public sidewalks constructed along both sides of the plat’s internal streets. According to the document: School Access Analysis Diamond Valley Estates, Apex Engineering PLLC, undated, the proposed lots/homes are within the Auburn School District; and served by Gildo Rey Elementary, Olympic Middle, and Auburn High School. Gilda Rey Elementary is located approximately 3.3 miles to the north. Olympic Middle School is located approximately 4.5 miles to the north. Auburn High School is located approximately 5.5 miles to the north. It is anticipated that students would be bused to all three school locations. E. Parks and Open Space. Adequate provisions for parks are made through the payment of park impact fees at the time of building permit issuance for each lot or as may be deferred per ACC 19.08.030(G). ACC 17.14.100 provides that an applicant should dedicate park land where a proposed subdivision will result in a substantial increase in demand for park land and that “generally” this will occur with subdivisions supporting 50 or more dwelling units. The proposed project of 200 lots exceeds the threshold of 50 units that requires the dedication of park space in accordance with ACC 17.14.100, (Parks and Playgrounds). The staff report notes that this standard Information Provided by Jeff Parks on 09.30.19 313 of 350 has been met by the dedication of park land in surrounding development. Comprehensive Plan Policy LH2.3 requires 7.25 acres of park land per 1,000 residents at the rate of 2.5 persons per household in the Lakeland Hills Special Planning Area (applicable to the subject property). Staff determined this standard was also met by park dedications in surrounding subdivisions. It is also recognized that the 2.51 Tract E of the proposal is designated as a recreational tract, which the applicant asserted in its power point (Ex. 32) will include a grassy play area, picnic tables and a play structure at a minimum. Apparently, Tract E will not be publicly dedicated as park property, which is apparently why the staff report didn’t recognize Tract E as contributing towards the applicant’s park dedication requirements. City standards do not require any specific amount of open space for the subdivision, so none can be required absent evidence demonstrating a specific need for the open space. See Isla Verde Int’l Holdings v. City of Camas, 146 Wn.2d 740 (2002). However, the applicant nonetheless proposes a significant amount of open space that would exceed any demonstrated open space needs for the project. The proposal includes 19.41 acres of non-disturbed natural vegetation area and a combined area of 47.21 acres of non-disturbed and replanted areas. F. Police and Fire Protection. Police and Fire services will serve the proposed development and will be provided by the Valley Regional Fire Authority and the City of Auburn Police Department. In its review of the Project, the City’s Transportation staff and the Valley Regional Fire Authority (VRFA), with approval of the modifications and with the proposed conditions, found the proposed ROW dedications and improvements to provide safe and sufficient access to serve the lots. To ensure emergency access to the lots of the plat, the project must comply with International Fire Code (IFC) requirements. This will include constructing homes with fire sprinkler systems where more than 30 lots cannot be served by two separate and remote approved fire apparatus access roads for the residential lots (see Section D107 and D104.3 of the IFC). Fire protection is also provided through the payment of fire impact fees at the time of building permit issuance for each lot or as may be deferred per ACC 19.06.040(F), and construction consistent with the City of Auburn Engineering Design Standards and the International Fire Code (IFC). Fire hydrants and fire flow will also be made to comply with City standards as part of final plat review. As conditioned, the project will have adequate provisions for emergency access/fire protection. CONCLUSIONS OF LAW Procedural: 1. Authority of Hearing Examiner. ACC 17.10.050 grants the Hearing Examiner with the authority to review and make a final decision on an application for Information Provided by Jeff Parks on 09.30.19 314 of 350 preliminary plat. ACC 18.70.010 grants the Hearing Examiner with the authority to review and make a final decision on variance requests for zoning code provisions. ACC 17.18.010(A) grants the Hearing Examiner with the authority to approve modifications to the City’s Design Standards with the concurrence of the City Engineer. Substantive: 2. Zoning and Comprehensive Plan Designation. The site is zoned R-5 Residential and its Comprehensive Plan map designation is Single-Family Residential. 3. Applicability of Variance to Class IV Landslide Hazards. Variance requests may not be made for alterations to Class IV Landslide Hazard areas. It is recognized that ACC 16.10.160 generally authorizes variances in addition to reasonable use requests to the requirements of Chapter 16.10 ACC (also known as the City’s Critical Areas Ordinance). However, ACC 16.10.100(E)(2)(a) provides that for Class IV Landslide Hazard Areas, “[a]lteration shall be prohibited subject to the reasonable use provisions of this chapter.” Similar provisions limit alteration to the reasonable use process for Category I wetlands, ACC 16.10.100(A)(1), and Critical Habitat, ACC 16.10.100(C)(1). Class IV Landslide Hazard Areas, Class I Wetlands and Critical Habitat are the most sensitive of the City’s protected critical areas. No such similar limitations are called out for Class I-III geologically hazardous areas, Class II-IV wetlands or secondary or tertiary habitat. It’s fairly clear that the City Council intended to set a higher bar for modification of the regulations of the City’s most sensitive critical areas. This interpretation is supported by the rule of statutory construction that ordinances must be construed in a manner that all the language used is given effect, with no portion rendered meaningless or superfluous. See Rapid Settlements, Ltd. V. Symetra Life Ins. Co., 134 Wn. App. 329, 332 (2006). If ACC 16.10.100(E)(2)(a) is intended to still allow alteration through variance application, there would be no need for it and it would be rendered meaningless. This is because the less sensitive critical areas, i.e. the aforementioned Class I-III geologically hazardous areas, Class II-IV wetlands and secondary or tertiary habitat, make no mention of what alteration process (reasonable use or variance) applies to them. They don’t need to because ACC 16.10.150 (Reasonable Use Process) and ACC 16.10.160 (Variance Process) by their own terms apply to all critical area requirements. If the City Council wanted the more sensitive critical areas to also be subject to both the variance and reasonable use process, the Council similarly didn’t need to make any reference to what modification process applied to them. The only2 contrary interpretation, if any meaning is to be given to 2 There is the added argument to be made that the Class IV Landslide Hazard ACC 16.10.100(E)(2)(a) provision references reasonable use and that reasonable use, in turn, provides at ACC 16.10.150(F) that the applicant should apply for a variance except when application of the critical area regulations would deny all reasonable use. However, if the ACC 16.10.100(E)(2)(a) reference to “reasonable use” is intended to Information Provided by Jeff Parks on 09.30.19 315 of 350 ACC 16.10.100(E)(2)(a), is that only the most sensitive critical area regulations are subject to both variance and reasonable use review and the less sensitive critical areas don’t qualify for any alteration. That, of course, would be nonsensical. Class IV Landslide Hazard Areas, Class I wetlands and Critical Habitat are all highly sensitive critical areas. To afford maximum protection while still recognizing constitutionally protected property rights, the Council only intended to allow alteration through the reasonable use process. 4. Review Criteria and Application. ACC 17.06.070 governs the criteria for preliminary plat approval. ACC 17.18.030 governs the criteria for Design Standard deviations. ACC 18.10.070(A) governs the criteria for variances to minimum density standards. Relevant criteria are quoted below with corresponding conclusions of law. Preliminary Plat Standards: ACC 17.07.070(A): Adequate provisions are made for the public health, safety and general welfare and for open spaces, drainage ways, streets, alleys, other public ways, water supplies, sanitary wastes, parks, playgrounds and sites for schools and school grounds. 5. As identified in Finding of Fact No. 5 and 6, the proposal is adequately served by all public services and utilities required in the criterion above. As further determined in Finding of Fact No. 5, there are no adverse impacts associated with the proposal. Given the absence of any adverse impacts in conjunction with adequate public facilities, it is concluded that adequate provision is made for the public health, safety and welfare. ACC 17.07.070(B): Conformance of the proposed subdivision to the general purposes of the Comprehensive Plan. 6. The proposal is consistent with the Comprehensive Plan for the reasons identified in Pages 18-21 of the staff report. ACC 17.07.070(C): Conformance of the proposed subdivision to the general purposes of any other applicable policies or plans that have been adopted by the City Council. fold in the ACC 16.10.150(F) “reasonable use” reference to variance review, there was no need for ACC 16.10.100(E)(2)(a) to begin with since both the variance and reasonable use provisions would apply in its absence. The only way to logically construe ACC 16.10.100(E)(2)(a) is that it limits modifications to those authorized by reasonable use review, not variance review. Information Provided by Jeff Parks on 09.30.19 316 of 350 7. The proposal is consistent with all other applicable policies and plans for the reasons identified at pages 21-23 of the staff report. ACC 17.07.070(D): Conformance of the proposed subdivision to the general purposes of the Land Division Ordinance as enumerated in ACC Section 17.02.030. ACC 17.02.030: The purpose of this title is to regulate the division of land lying within the corporate limits of the city, and to promote the public health, safety and general welfare and prevent or abate public nuisances in accordance with standards established by the state and the city, and to: A.Prevent the overcrowding of land; B.Lessen congestion and promote safe and convenient travel by the public on streets and highways; C.Promote the effective use of land; D.Provide for adequate light and air; E.Facilitate adequate provision for water, sewerage, drainage, parks and recreational areas, sites for schools and school grounds, and other public requirements; F.Provide for proper ingress and egress; G.Provide for the expeditious review and approval of proposed land divisions which comply with this title, the Auburn zoning ordinance, other city plans, policies and land use controls, and Chapter 58.17 RCW; H.Adequately provide for the housing and commercial needs of the citizens of the state and city; I.Require uniform monumenting of land divisions and conveyance by accurate legal description; J.Implement the goals, objectives and policies of the Auburn comprehensive plan; K.Prevent or abate public nuisances. 8. The proposal is consistent with the purposes of the Land Division Ordinance as enumerated above. The roads designed for the proposal are safely designed to meet traffic demand and sidewalks on both sides of the subdivision street promote pedestrian safety. Applicable zoning setbacks and an ample amount of open space provide for adequate light and air. The proposal does not result in overcrowding as it proposes a density that is less than that specified for the applicable zoning district. As previously discussed, the proposal is consistent with and implements the Auburn Comprehensive Plan. As previously determined the proposal is adequately served by all essential public facilities and it is consistent with the comprehensive plan. The subdivision process, with the required surveying and recording of final plats, provides for uniform monumenting and conveyance by accurate legal description. ACC 17.07.070(E): Conformance of the proposed subdivision to the Auburn Zoning Ordinance and any other applicable planning or engineering standards and specifications as adopted by the City. Information Provided by Jeff Parks on 09.30.19 317 of 350 9.Except for the requested variances and deviation requests, the proposal is in conformance with applicable development standards as outlined at pages 24-25 of the staff report. ACC 17.07.070(F): The potential environmental impacts of the proposed subdivision are mitigated such that the preliminary plat will not have an unacceptable adverse effect upon the quality of the environment. 10.As determined in Finding of Fact No. 5 there are no significant adverse impacts associated with the proposal. ACC 17.07.070(G): Adequate provisions are made so the preliminary plat will prevent or abate public nuisances. 11.As determined in Finding of Fact No. 5, there are no significant adverse impacts associated with the proposal. Consequently, no public nuisance is anticipated. Density Variance: ACC 18.70.010(A)(1): That there are unique physical conditions including narrowness or shallowness of lot size or shape, or exceptional topographical or other physical conditions peculiar to and inherent to the particular lot; and that, as a result of such unique physical conditions, practical difficulties or unnecessary hardships arise in complying with provisions of this title. 12.The criterion is met. The project site is heavily affected by unique physical conditions. As outlined in Finding of Fact No. 3, most the project site is composed of slopes at least 15% in grade. The site is also heavily encumbered with wetlands and streams. Because of these physical conditions, City staff had to request several project revisions of the applicant to ensure consistency with City standards for maximum road grade, for water pressure zones, and impoundment for stormwater pond side slopes. Avoiding the complicated network of critical areas and buffers necessitates the requested reduction in density. ACC 18.70.010(A) (2): That, because of such physical conditions, the development of the lot in strict conformity with the provisions of the Zoning Ordinance will not allow reasonable and harmonious use of such lots. 13.The criterion is met. As noted in the staff report, if the variance were not approved, project modifications to increase the lot and dwelling unit count likely would result in not achieving other zoning standards, such as lot width and minimum lot area, which would be considered to preclude reasonable and harmonious use of such lots. Information Provided by Jeff Parks on 09.30.19 318 of 350 ACC 18.70.010(A) (3): That the variance, if granted, will not alter the character of the neighborhood, or be detrimental to surrounding properties in which the lot is located. For nonconforming single-family homes, this finding is determined to be met if the features of the proposed variance are consistent with other comparable features within 500 feet of the proposal. 14. The criterion is met. The proposal will not alter neighborhood character or be detrimental to surrounding properties. Surrounding properties are already residentially developed or zoned for that purpose. The density of the proposed project will be less than that of surrounding residential development, but given all surrounding development is also single-family development, the reduced density is not out of character and would not adversely affect surrounding properties. ACC 18.70.010(A) (4): That the special circumstances and conditions associated with the variance are not a result of the actions of the applicant or previous owners. 15. The criterion is met as the applicant and previous owners are not in any way responsible for the topography and wetlands and streams on the property. ACC 18.70.010(A) (5): Literal interpretation of the provisions of the zoning code would deprive the applicant of rights commonly enjoyed by other properties in the same zoning district. 16. The criterion is met. In the absence of variance approval, as previously noted the applicant would be forced to develop lots of substandard size. ACC 18.70.010(A) (6): The approval of the variance will be consistent with the purpose of the zoning code and the zoning district in which the property is located. 17. The criterion is met. The stated purpose of the zoning regulations as noted in ACC 18.02.020 includes promoting convenience, comfort, prosperity, and general welfare of the city’s population and creation and preservation of a more healthful, serviceable and attractive municipality and environment in which to live. These objectives are met since as determined in Finding of Fact No. 5, the proposed subdivision at the proposed reduced density will not create an y significant adverse impacts. ACC 18.70.010(A) (7): Variance will not allow an increase in the number of dwelling units permitted by the zoning district. 18. No increase is proposed. ACC 18.70.010(A) (8): The authorization of such variance will not adversely affect the comprehensive plan. 19. As previously determined, the proposal overall is consistent with the Comprehensive Plan. More specifically, as determined in Finding of Fact No. 5 the Information Provided by Jeff Parks on 09.30.19 319 of 350 proposal will not detract from the City’s ability to meet projected growth targets upon which the land use element of the comprehensive plan is based. ACC 18.70.010(A) (9): The variance shall not allow land use that is not permitted under the zoning district in which the property is located. 20. The proposed single-family dwellings are authorized in the R5 zone. ACC 18.70.010(A)(10): The variance shall not change any regulations or conditions established by surface mining permits, conditional use permits, or contract rezones authorized by the City Council. 21. According to staff, there are no known regulations or conditions established by surface mining periods, conditional use permits, or contract rezones authorized by the City Council that apply to this site. Deviations (Conclusions include findings of fact): ACC 17.18.030(A): Such modification is necessary because of special circumstances related to the size shape topography location or surroundings of the subject property to provide the owner with development rights and privileges permitted to other properties in the vicinity and in the zoning district in which the subject property is located. 22. The criterion is met. As noted in the analysis of the variance request, the project site contains substantial grade change and contains two stream courses and wetland areas. These are unique physical conditions consisting of exceptional topographical or other physical conditions peculiar to and inherent to the site; and that, because of such unique physical conditions, practical difficulties and hardships arise in complying with the provisions of this title and each of these three standards of the City of Auburn Engineering Design Standards (manual). ACC 17.18.030(B): That because of such special circumstances the development of the property in strict conformity with the provision of this title will not allow a reasonable and harmonious use of the property. 23. The criterion is met. As noted in the earlier analysis of the variance requests, the difficulty in complying is results from topographical and other physical conditions peculiar to and inherent to the site. The roadway curve radius and the need for walls around three sides of the ponds are the result of slope constraints. The need for the roadway section modifications to Roads B & C are to accommodate a road network that meets public access and emergency access needs through wider street segments in the event both needs are required simultaneously. Currently, there is not an opportunity to make a second emergency vehicle access via another direction due to development status or grades of adjacent sites. A future connection of Road B is proposed where future extension is reasonably foreseeable Information Provided by Jeff Parks on 09.30.19 320 of 350 ACC 17.18.030(C): That the modification if granted will not alter the character of the neighborhood or be detrimental to surrounding properties in which the property is located 24. The criterion is met. The proposed deviations will for the most part not be visible to surrounding properties and there are no potential adverse impacts to surrounding properties reasonably inferred from the deviations. The modest changes to road and stormwater design standards will make a negligible difference to neighborhood character. ACC 17.18.030(D): Such modification will not be materially detrimental to the implementation of the policies and objectives of the comprehensive land use circulation and utility plans of the city 25. The criterion is met. All the requested deviations have been reviewed by Transportation and Utilities staff and by the City Engineer, who has determined that they will not be materially detrimental to surrounding properties nor to public safety (Exhibit 17). Consequently, approval of the three Modifications is also consistent with the Comprehensive Stormwater Drainage Plan and the Comprehensive Transportation Plan policies of providing stormwater management, preserving neighborhood continuity and cohesiveness and provisioning of a safe transportation system. ACC 17.18.030(E): Literal interpretation of the provisions of this title would deprive the applicant of rights commonly enjoyed by other properties in the same zoning district. 26. The criterion is met. Without the deviations, the applicant would be unable to construct a safe and efficient road network, since topography requires several dead-end streets. The Applicant would also be precluded from constructing a reasonably feasible stormwater system. Deprivation of a safe and efficient road system and a feasible stormwater system would qualify as deprivation of rights commonly enjoyed by other properties in the vicinity, which are composed of subdivisions in areas with far less topographical and critical area constraints. ACC 17.18.030(F): The approval of the modification will be consistent with the purpose of this title 27. As previously concluded, the proposal as a whole is consistent with purpose of Title 17, the ‘Land Adjustments Divisions Ordinance. The deviations are reasonably necessary for the Applicant’s project design. ACC 17.18.030(G): The modification cannot lessen the requirements of the zoning ordinance. 28. The modifications do not violate any Zoning Ordinance provisions. Information Provided by Jeff Parks on 09.30.19 321 of 350 DECISION The proposed preliminary plat, as described in this decision and in Ex. 6, is approved subject to the following conditions: Earth: 1. All approvals and permits related to the Project and issued by the City, including permits related to the construction of single-family residences, shall be consistent with and implement recommendations of the document: Geotechnical Engineering Services and Geomorphology Services, Diamond Valley Estates Development, Auburn WA, GeoEngineers, Rev. April 21, 2016. This shall include approvals and permits related to retaining walls. 2. Site clearing, grading, stabilization, pond, and roadwork shall occur during summer construction season, except as otherwise authorized by City staff. Prior to issuance of clearing or grading permits or public facility extension (FAC), a grading plan for grading and clearing necessary for both the construction of infrastructure such as roads and utilities and for lot grading shall be prepared, submitted and approved by the City of Auburn. The purpose of the plan is to accomplish the maximum amount of grading at one time to limit or avoid the need for subsequent grading and disturbance, including grading of individual lots during home construction. The plan shall identify the surveyed boundary of the crest slopes for the site's 40% or greater slopes. This plan shall show quantities and locations of excavations and embankments, the design of temporary storm drainage detention system(s), and methods of preventing drainage, erosion and sedimentation from impacting adjacent properties, natural and public storm drainage systems, and other nearby sensitive areas. All the measures shall be implemented prior to beginning on-site filling, grading or construction activities. The applicant's grading plans shall be prepared in conjunction with, and reviewed by, a geotechnical engineer licensed in the State of Washington. The geotechnical engineer shall develop and submit, for the City's review, specific recommendations to mitigate grading activities with particular attention to developing a plan to minimize the extent and time soils are exposed on site and address grading and related activities during wet weather periods (the period of greatest concern is October 1 through March 31). The plans shall show the type and the extent of geologic hazard area or any other critical areas as required in Chapters 16 ‘Structural Design’ and 18 ‘Soils and Foundations’ of the International Building Code (IBC) and/or the Titles 16 ‘Environment’ and 18 ‘Zoning’ of the City of Auburn’s Code. 3. Because of the high likelihood of encountering hillside seeps during earthwork, upon completion of rough grading and excavation, the applicant shall have a geotechnical engineer licensed in the State of Washington re-analyze the site and determine if new or additional mitigation measures are necessary. A revised geotechnical report shall be submitted to the City of Auburn for review and approval by the City Engineer. Recommendations for areas where subsurface water is known or discovered shall be given particular attention by the geotechnical engineer and coordinated with the project engineer responsible for the storm drainage system design. Information Provided by Jeff Parks on 09.30.19 322 of 350 4.To reduce the length of unimpeded high slopes and to collect and reduce the probable impacts of sheet flow on slope faces, installation of benches at least 6 feet wide into the slopes associated with Ponds 1 & 2, Road F and Lot 7 & 8 is required. Maximum vertical spacing between benches shall be 30 feet, as approved by the City Engineer. Staff shall waive this condition to the extent necessary to ensure consistency with the examiner’s conclusion that the applicant’s critical area variance requests are denied. Groundwater: 5.The Site is located within Groundwater Protection Zones 3 and 4. All approvals and permits related to the Project and issued by the City shall be consistent with best management practices (BMPs) per ACC 16.10.120(E)(1) and (2) and the following from the Surface Water Management Manual (SWMM) at a minimum: BMP C101 – Preserving Natural Vegetation BMP C102 – Buffer Zone BMP C103 – High Visibility Plastic or Metal Fence BMP C120 – Temporary and Permanent Seeding BMP C153 – Material Storage, Delivery, and Containment BMP C160 – Certified Erosion and Sediment Control Lead 6.Prior to issuance of a grading permit additional analysis is required to be submitted to the city for review and approval to assess the magnitude of the temporary and permanent dewatering that is/will be required. All permanent dewatering shall be designed to ensure long term, low cost, minimal maintenance. The applicant shall provide a detailed description of the required maintenance, frequency and how the facilities will be accessed, prior to permit issuance, including accessibility for long-term maintenance. Wetlands/Streams 7.The Wetland Assessment, Diamond Valley Estates Auburn WA, Raedeke Associates Inc. April 8, 2014, identifies that alteration of site wetlands and streams may be subject to jurisdiction of the Army Corps of Engineers (COE) and the Washington Dept. of Ecology (WDOE) and alteration of the site streams (including changes in flow) is subject to the jurisdiction of the Washington Dept. of Fish and Wildlife (WDFW). Concurrent with the review of land clearing, grading, or public facility extension (FAC) approvals, a final wetland/stream mitigation plan is required to be prepared and submitted to the city for review and approval. The plan shall address the wetland and stream classification, functions, and values, and shall ensure consistency with the purpose and intent of the city’s critical areas regulations consistent with ACC 16.10, and include copies of permits and correspondence with Army Corps of Engineers and Department of Ecology, related to permitting or exemption, as applicable. The mitigation plan shall be reviewed and approved prior to clearing, grading, or permit approval and issuance. The mitigation plan shall be part of the approved construction plan set. The mitigation plan shall include the following: Information Provided by Jeff Parks on 09.30.19 323 of 350 a. Stream channel conditions shall be monitored during the course of wetland/stream mitigation implementation and long-term monitoring to determine whether conditions have changed from pre-developed conditions or new erosion is occurring. The final mitigation plan shall provide for a contingency plan that identifies site-specific mitigation measures to protect the channel and prevent further erosion, as appropriate, in consultation with the project geotechnical engineer, civil engineer, and the City of Auburn, depending on the location and observed conditions. Such measures could include “soft” armoring with additional plantings or large woody debris, or “hard” armoring as suggested by GeoEngineers, Inc. (2016). b. If headcutting is observed in the stream reaches where the gradient increases, it is not clear whether “soft” armoring would be effective in preventing further erosion.If one of the “hard” armoring measures identified by GeoEngineers, Inc. (2016) is deemed necessary, this would likely require additional permits from the U.S. Army Corps of Engineers, WDFW, and City of Auburn. c. Pre-developed photos and reports shall be provided for the existing condition of the wetlands and stream channels along with a mitigation plan on the monitoring and process to address potential impacts created by the development, consistent with the City’s Critical Areas Ordinance. Plants: 8. To mitigate for aesthetic and wildlife impacts and support slope stability, due to the removal of significant trees and creation of steep slopes, a revegetation plan shall be prepared meeting the minimum "Best Management Practices" per Washington State Department of Ecology guidance for planting native vegetation on steep slopes. The plan shall be prepared by a plant biologist (or other professional with equivalent degree) in consultation with the geotechnical engineer. The plan shall be prepared and submitted for city review and approval by Planning Director identifying how disturbed portions of slopes, including those necessary for the construction of utilities and any other improvements, shall be landscaped/revegetated and stabilized. The proposal shall also identify measures to be taken for native vegetation retention during the construction process, include an installation schedule for landscaping/native revegetation, and define the overall restoration approach. The plan shall also address responsibility for long term retention of vegetation. Prior to final plat approval, the applicant shall post a financial guarantee, in a form acceptable to the City, that ensures that newly planted hillside restoration vegetation will survive according to approved performance standards for a minimum three-year period (including a minimum of two full growing seasons) following planting and so that dead and unhealthy trees shall be promptly replaced. Language shall be recorded as part of the final plat and as part of restrictive covenants indicating that the property owner shall, where applicable, be responsible for maintenance and retention of trees/vegetation on individual lots, if appropriate, and the Homeowner's Association responsible for maintenance and retention of vegetation in areas held in common. Information Provided by Jeff Parks on 09.30.19 324 of 350 9. Dispersion Trenches, if utilized, shall avoid/minimize disturbance of native vegetation in and around the dispersion trenches. Aesthetics: 10. The developer will be required to enter into an agreement or submit a declaration of Conditions, Covenants, and Restrictions (CC&Rs), enforceable by the City, in a manner acceptable to the City, to ensure the long term maintenance by the Homeowners Association (HOA) of the open space tracts and areas necessary to meet sight distance standards prior to issuance of final plat approval. 11. Proposed Conditions, Covenants and Restrictions (CC&Rs) for the future Homeowners' Association shall be submitted for review and approval by the City prior to final plat approval. This document shall specify the financial means of maintenance of all common tracts and open spaces by the HOA. 12. The final design of the landscaping shall be generally consistent with the Diamond Valley Estates Landscape Plan, Sheet L1 and L2, Bradley Design Group, Inc., March 19, 2014, July 11, 2016. The landscape plan shall be included with the civil plans (public facility extension and grading) and may require revisions to meet code requirements and to coordinate with other site improvements. 13. Any plat entrance signage shall be a low monument style with accenting landscaping. The number, style, placement of signs and associated landscaping shall be approved by the Planning Director and comply with Chapter 18.56 ACC (Signs). 14. Any fencing placed along the rear yard property lines of the residential lots by the applicant shall be of consistent material, style, and color. The Planning Director shall approve such fences, which shall be equivalent to a 6-ft. high solid wood fence. Any fencing to be erected adjacent to any of the pedestrian pathways or leading to the open space tracts shall also be submitted to the Director for approval and may be different. 15. Compliance with all the mitigation measures as noted on Pages 9 - 19 of the "Kersey III Preliminary Plat Final EIS" City of Auburn, February 11, 2005 and as otherwise noted throughout the document is required. Historic/cultural preservation: 16. In the event ground disturbing activity results in the discovery of resources with potential historical, cultural and/or archeological significance, work shall be stopped in a large enough area to maintain integrity of the discovery and appropriate local, State and tribal offices shall be notified immediately. Transportation: 17. While the document, School Access Analysis Diamond Valley Estates, Apex Engineering PLLC, undated, identifies that the Auburn School District serves this Site, and anticipates providing school bus service to the proposed plat based on distance to schools, prior to approval of the civil plans (public facility extension Information Provided by Jeff Parks on 09.30.19 325 of 350 and grading), the applicant shall consult with the Auburn School District Transportation Coordinator to determine if the plat construction shall include a pick-up/drop-off area from Evergreen Way SE to avoid school buses having to enter the plat. The results of the consultation shall be shared with the City and any necessary revisions to the plat made. 18.A note shall be placed on the Final Plat indicating that there shall be no direct access to Evergreen Way SE from the individual lots of the plat. 19.Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the plans shall show that appropriate portions of public streets shall be posted no-parking on the appropriate portions of the streets due to its road width or presence of medians. Also, the cul-de-sacs shall be posted “No Parking” around their entire perimeter. Posting shall be in accordance with ACC 10.36.175. 20.As condition of preliminary plat approval, it shall be the responsibility of the developer that is extending the public street improvements, to remove the temporary cul-de-sac on adjacent plats, at their expense. 21.The following note, or functional equivalent, as determined by the City Engineer, shall be provided on the final plat: "WHEN IT BECOMES NECESSARY, AS PART OF A SUBDIVISION, TO INSTALL A TEMPORARY CUL-DE-SAC PER CITY OF AUBURN DESIGN STANDARDS, THE PORTION OF THE TEMPORARY CUL- DE-SAC ENCROACHING ON THE ADJACENT PRIVATE PROPERTY SHALL BE PLACED IN A TEMPORARY EASEMENT DEDICATED TO THE CITY OF AUBURN. THE TEMPORARY EASEMENT SHOWN ON THE LOTS IS HEREBY RESERVED, GRANTED AND CONVEYED TO THE CITY OF AUBURN FOR TEMPORARY PUBLIC ROADWAY PURPOSE, UPON THE RECORDING OF THIS PLAT. THE CITY OF AUBURN IS HEREBY RESPONSIBLE FOR THE MAINTENANCE OF THE TEMPORARY PUBLIC ROADWAY FACILITIES WITHIN SAID EASEMENT. UPON THE CONSTRUCTION OF AN EXTENSION OF THE STREET, AND WHEN DETERMINED BY THE CITY OF AUBURN THAT THE TEMPORARY CUL-DE-SAC IS NO LONGER REQUIRED, IT SHALL BE THE RESPONSIBILITY OF THE DEVELOPER THAT IS EXTENDING THE PUBLIC STREET IMPROVEMENTS, TO REMOVE THE TEMPORARY CUL-DE-SAC AT THEIR EXPENSE. IN CONJUNCTION WITH TEMPORARY CUL-DE-SAC REMOVAL, THE DEVELOPER SHALL ALSO FINISH CONSTRUCTION OF THE PUBLIC STREET WITHIN THE TEMPORARY CUL-DE-SAC AREA IN ACCORDANCE WITH THE CITY OF AUBURN DESIGN STANDARDS APPLICABLE TO THE STREET CLASSIFICATION, AS WELL AS ANY PRIVATE IMPROVEMENTS AND PROPERTY RESTORATION THAT MAY BE NECESSARY ON ADJACENT LOTS Information Provided by Jeff Parks on 09.30.19 326 of 350 AFFECTED BY THE REMOVAL OF THE TEMPORARY CU L-DE- SAC. THE TEMPORARY EASEMENT SHALL AUTOMATICALLY TERMINATE UPON REMOVAL OF THE TEMPORARY CUL-DE-SAC IMPROVEMENTS, AS APPROVED BY THE CITY OF AUBURN." 22. Consistent with City Comprehensive Plan Policy (Policy TR-130) for pedestrian connectivity, during civil plan review, the City will evaluate whether Tract D, a shared access and utility tract, is capable of being extended north to connect to Evergreen Way SE to provide a public pedestrian connection and shorter walking route for school age children to bus stops and pedestrians to the adjacent subdivision of Kersey III, Division 2. If feasible, as determined by the City Engineer, this construction shall be shown on the civil plans and contain appropriate easement provisions provided on the Final Plat. 23. The Facilities Extension Agreement (FAC) shall include the design of the mini roundabout at the intersection of Roads B, C and F as identified in Exhibit 23 – Diamond Valley Estates Road B at Road F/C Mini Roundabout Design Report, Transportation Solutions Inc., November 8, 2016, as reviewed and accepted by the City Engineer. Public services: 24. Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the construction plans shall show that the water system design is sufficient to demonstrate any portion of a future proposed structure is within 300 feet of a fire hydrant. 25. Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the construction plans shall show conformance with International Fire Code standards for fire apparatus access roads, generally as follows: Road G (including Tracts B, C, and D): lots requiring residential fire sprinklers include Lots 3-12 and 16-35; Road C (including Tract J): lots requiring residential fire sprinklers include Lots 135-181. To eliminate the second remote access requirement for development of over 30 dwelling units; Exception 1, residential fire sprinkler systems (RFS) can be used in the following areas of the development. Note that, if at time of dwelling construction, the secondary access road is accessible from the future development, Exception 2 can be evaluated. At this time, however, residential fire sprinkler system will be required in the following areas of the development: Road B: lots requiring residential fire sprinklers include Lots 86-132 Road F: lots requiring residential fire sprinklers include Lots 68-81. Information Provided by Jeff Parks on 09.30.19 327 of 350 Utilities: 26. Prior to Final Plat Approval, the applicant shall create from “Tract I” separate tracts to contain only Storm Pond 1 and Storm Pond 2, said new tracts to be owned by the City, and “Tract I” to be under the ownership and maintenance of the HOA. 27. Prior to the approval of the construction plans under the Facilities Extension Agreement (FAC), the applicant shall work with the appropriate regulatory agencies to determine if Stormwater Ponds 1 and 2 are subject to the provisions of Washington State Dam Safety and provide this correspondence to the City. If Dam Safety requirements apply, the Applicant shall also secure the necessary permits and comply with the State regulations for dams on the construction plans. 28. Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), provide documentation of application to the Washington State Department of Ecology (WSDOE) for a General Storm Permit, as required for all projects over 1 acre in size. 29. Benching of the graded slopes above developed storm drainage facilities (i.e., roads, ponds, and homes) is required for protection of the proposed facilities. Benches shall be at least 6 feet wide. Maximum vertical spacing between benches shall be 30 feet, as referenced on Page 44 of the Geotechnical Engineering Services and Geomorphology Services, Diamond Valley Estates Development, Auburn WA, GeoEngineers, Rev. April 21, 2016 and as reviewed and accepted by the City Engineer. 30. Sheet 22 of Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016 shows fill slopes that are not keyed in. Special attention should be made in the design of fill slopes to prevent failure. Prior to the approval of civil plans provide design recommendation from the geotechnical consultant on the keying- in of fill slopes on this project and as reviewed and accepted by the City Engineer. 31. Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the Conceptual Utility Plan, Sheets 14 and 15 of Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. April 27, 2016, Rev. July 14, 2016, shows steep storm pipe runs, and, as a result, appropriately designed energy dissipation features are required at the end of long runs of pipe, at pipe intersections, and at the inlet/outlet to the storm drainage ponds. 32. A note shall be placed on the Final Plat indicating that the Diamond Valley Estates Homeowner’s Association and its heirs and successors shall maintain those portions of the tracts containing stormwater ponds and specifically the portions located outside the fenced pond boundaries, or if no fence is provided, outside the 10-year storm water surface elevation, as determined by the City Engineer. Additionally, the Covenants, Conditions, and Restrictions (CC&Rs) to be reviewed by the City shall also address this maintenance responsibility. 33. The building permit applications for the individual lots shall identify that all residential stormwater downspout connections and footing drains shall be tight- lined to the nearest public drainage system and be placed with private drainage easements to be shown and described on the final plat, except for approximately Information Provided by Jeff Parks on 09.30.19 328 of 350 17 lots referenced on Page 4 and in Appendix C of Exhibit 4, Preliminary Plat Conceptual Drainage Report for Diamond Valley Estates, (Apex Engineering PLLC, March 26, 2014, Rev. December 8, 2014) that are intended to discharge to the onsite wetlands for rehydration of the wetlands . No runoff will be allowed to run uncontrolled through separately owned lots under the final Site design. 34.Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the construction plans shall show the following for areas of Ponds 1 and 2: Uphill Cut Slope: Temporary dewatering of the hillside above each pond shall occur prior to its construction. A permanent drainage dewatering system shall be included on the civil plans and installed in “Tract I” near the base of the slope and shall be owned and maintained by the HOA under a maintenance agreement with the City. Downhill Fill Berm: A full liner of the entire pond and slopes is required. A partial liner would allow seepage from the unlined area to bypass the lined part. A permanent drainage dewatering system shall be installed below the outboard fill slope, and shall be owned and maintained by the City. 35.Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the plans shall show that the stormwater pond access roads for Storm Ponds 1 and 2 shall have a maximum grade of 15% for paved access roads, 7% for gravel access roads. 36.Prior to City approval of the construction plans under the Facilities Extension Agreement (FAC), the plans shall show that the following condition is applicable to Road F: Uphill Cut Slope: To increase the static factor of safety above 1.00 and eliminate the potential for groundwater surfacing at grade, installation of a permanent drainage dewatering trench system is required. Downhill Existing Slopes: To increase the static factor of safety above the calculated 1.03, installation a permanent drainage dewatering system at the toe of the slope that shall be owned and maintained by the HOA under a maintenance agreement with the City is required. 37.Tracts D (a shared private utility and access tract) and F (a utility tract) shall be owned and maintained by the homeowner’s association or one or more individual lot owners. The portions of the sanitary sewer system located within those tracts shall lie within a public utility easement located completely within those tracts, as shown in the Conceptual Utility Plan, Sheet 14 of Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016. 38.Tract I, as shown on Sheet 1 of Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016 (consisting of wetlands, streams, buffers, storm facilities at the NE corner) contains Information Provided by Jeff Parks on 09.30.19 329 of 350 wetlands and proposed storm ponds in addition to the outfall sewer line on a steep slope. On the final plat, the applicant shall dedicate to the City of Auburn a 30' sewer easement, centered on the sewer pipe as constructed, across the proposed Tract I. That portion of Tract I is to be owned and maintained by the HOA. 39.From the Conceptual Utility Plan, Sheets 14 and 15 of Diamond Valley Estates Preliminary Plat (drawings) Sheets 1 through 26, Apex Engineering PLLC, March 26, 2014, Rev. July 14, 2016, it appears that the required separation between utilities (mostly sewer and water) has not been ensured within the roadways, specifically on curved portions of Road B and Road F. Prior to City approval of construction plans, the civil plans (FAC) must show that the required separation is not prevented by the proposed road geometry. If relief from this standard is needed, the Hearing Examiner agrees to delegate authority to the City Engineer to decide if a deviation from the Engineer Design Standards (manual) will be allowed. 40.Notice of adjoining Mineral Resource Lands in conformance with RCW 36.70A.060(1)(b) and as approved by City staff shall be placed on the final plat. 41.For each of the critical area variances requested by the Applicant, the applicant shall either revise the proposal to remove the requested encroachment or acquire approval of a reasonable use exception pursuant to ACC 16.10.150. DATED this 8th day of February, 2017. City of Auburn Hearing Examiner Appeal Right and Valuation Notices This decision is final subject to appeal to superior court as governed by Chapter 36.70C RCW. Affected property owners may request a change in valuation for property tax purposes notwithstanding any program of revaluation. Information Provided by Jeff Parks on 09.30.19 330 of 350 331 of 350 EXHIBIT 13 332 of 350 333 of 350 334 of 350 335 of 350 MEMORANDUM 22035 Preliminary Design for Minor Adjustment Memo_2022-11-30 11400 SE 8th St, Suite 450, Bellevue, WA 98004 P a g e | 1 PO Box 3565, Bellevue, WA 98009 T: 425.462.1080 |F: 425.462.7719 www.goldsmithengineering.com Date: November 30, 2022 To: Jeff Dixon, City of Auburn Community Development cc: Jim Sprott, Pulte Homes of Washington, Inc.; Alex Wilford, Pulte Homes of Washington, Inc.; Ryan Kohlmann, Pulte Homes of Washington, Inc. From: Keith Goldsmith Re: Diamond Valley Estates Preliminary Plat – Revised Preliminary Design for Minor Adjustment This memorandum is provided in response to the City of Auburn’s request for additional information to preliminarily evaluate and provide a determination for a request for a minor adjustment to the Approved Diamond Valley Estates Preliminary Plat (City File #PLT14-0006). Updated Diamond Valley Estates preliminary designs proposed for the minor adjustment include: •An Exhibit overlaying the revised road and lots to avoid critical areas, •Revised preliminary utility plans from the preliminary plat, •Revised preliminary grading plans from the preliminary plat, •Revised preliminary road profiles from the preliminary plat. The adjustment to the preliminary plat configuration includes realignment of Roads E, F and G to avoid certain Class IV Landslide Hazard areas as required by Hearing Examiner approval condition #2, realignment of the Stormwater Pond #1 access road to avoid said Landslide Hazard, and demonstration that the required benching of slopes over 30’ in height can be accomplished without significantly altering the plat configuration. It was a tremendous help to have a better understanding of the City’s administrative interpretation of Class IV Landslide Hazard areas refining the broadness of Auburn City Code Section 16.10.100(E). We now understand that the City applies a threshold area of 40% slopes before classifying them as a Class IV Landslide Hazard as well as recognizing that manmade cuts or fill embankments such as those associated with Evergreen Way SE are likewise not regulated under Section 16.10.100(E). Per the city’s request, the following minor adjustment code criteria elements per Auburn Municipal Code ACC 17.10.100(A) have been evaluated and are addressed specific to the proposed preliminary design updates submitted herewith. 336 of 350 EXHIBIT 14 Memo Cont… Diamond Valley Estates Preliminary Plat -Revised Preliminary Design for Minor Adjustment 22035 Preliminary Design for Minor Adjustment Memo_2022-11-30 P a g e | 2 A. Minor Adjustment. 1. The adjustment maintains the design intent or purpose of the original approval; and the proposed revisions do not exceed the 10% dimensional change criteria. • Approved preliminary plat lot count was 200. The revised preliminary site design proposes 193 lots. A 7% reduction in lot yield. • The proposed reconfiguration only affects Roads E, F, and G as they relate to avoidance of 40% slopes. This is consistent with the Finding of Fact #3 of the FINDINGS OF FACT, CONCLUSIONS OF LAW AND FINAL DECISION of the Hearing Examiner dated February 8, 2017, the configuration of lots needs to be revised to avoid two Class IV Landslide Hazard areas. • All other roads and lots remain unchanged, and all access connections remain unchanged from the approved preliminary plat. • Road F proposes a horizontal radius of approximately 175’ which deviates from the minimum 333’ radius. The Findings of Fact, Conclusions of Law and Final Decision of the Hearing Examiner approved a Deviation to design horizontal curves less than 333’ radius. Specifically, there were four (4) curves identified on the preliminary plat, two on Road B and two on Road E. The revised layout provides four (4) horizontal curves under the standard 333’ radius, the same two on Road B, one curve on Road E and the 175’ radius curve on Road F, to avoid the Class IV Landslide Hazard. • Road E and F profiles have been revised per the revised alignment but are demonstrated to maintain a maximum 8% road grade allowed per the code. • Stormwater pond #1 can be graded to meet benching requirements and current standards for the pond access road. The sizes of ponds will not change significantly, and final designs will address fill keyways per the geotechnical recommendations. 2. The adjustment maintains the quality of design or product established by the original approval; and There is no proposed change to the quality of design or the proposed lot sizes ranging from 50’ to 65’ in width. There are no proposed changes to access and circulation or off-site road connections. The major grading will not change significantly albeit avoiding the Class IV Landslide Hazard per the Hearing Examiner Conditions. 3. The adjustment does not cause a significant environmental or land use impact on or beyond the site; The proposed adjustment does not change any impact on the environment or land use that was not part of the original preliminary plat approval. The only adjustment is the modest adjustment in the alignment of Roads E, F and G to avoid impact to Class IV landslide hazard areas as directed by the Hearing Examiner. 4. The adjustment is not precluded by the terms of this title or by state law from being decided administratively. 337 of 350 Memo Cont… Diamond Valley Estates Preliminary Plat -Revised Preliminary Design for Minor Adjustment 22035 Preliminary Design for Minor Adjustment Memo_2022-11-30 P a g e | 3 The proposal is that the modest change in road alignment and 7% reduction on lot yield would appear to be within the realm of minor adjustment of a preliminary plat (ACC 17.10.100(A)) and therefore should be allowed as an administrative decision. 5.Circumstances render it impractical, unfeasible or detrimental to the public interest to accomplish the subject condition or requirement of preliminary plat or short plat approval.” The Hearing Examiner Approval Condition #2 requires that grading revisions be made to avoid certain Class IV Landslide Hazard areas. This condition renders the road and lot layout depicted on the approved preliminary plat infeasible to develop without adjustment to the alignment of Roads E, F and G or the issuance of a Reasonable Use Exception for development in a critical area. The proposed adjustment to the road and lot configuration is proposed as minor adjustment to avoid said Class IV Landslide Hazard areas without significantly altering the intent of the original design. Conclusion: We respectfully request that city staff provide a response to the following questions upon review of the updated plans and memorandum submitted herein. 1.Will the City conclude for Pulte Homes that this change can be submitted and processed as a Minor Adjustment to the Preliminary Plat? 2.Will the City allow the plat development to be phased into multiple final plats? The intent would be to be working on the entire plat but the scope of work is too much to record the entire project in just one construction season. 3.Assuming phasing is allowed, does recording the first phase, or division of the plat preserve the preliminary plat approval past the February 2025 deadline (i.e. past the end of the third extension)? Thank you, we look forward to your response. 338 of 350 24633150606682TRACT "A"8882613710914131112153716172218353634211920233332252928262730403941434542444946485253515459586162646765716869707273747576807778798183848785869089929496919593981029799100101TRACT "G"TRACT "I"474555TR. "B"TR. "C"TR. "D"TRACT "I"TRACT "I"TRACT "G"TRACT "G"38TR. "H "25'25'25'25'25'25'25' 25'25'25'25'25'36'36'27.5'27.5'27.5'27.5'27.5' 27.5'23'31'36' 36'31'23'31'29'29'25'25'29' 29' 25'25' 33'33'103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132991341351361371381391401411421431441031041471481491501511521531541551561571581591601611621631641651661671681691701711721731741751761771781791801811821831841851861871881891901911921935657TRACT "F"TRACT "J"TRACT "E"ROAD G EVERGREEN WAY S.E.ROAD BROAD FROAD BROAD CROAD BROA D E 2022/11/09 10:20 DIAMOND VALLEY ESTATES PRELIMINARY PLAT MINOR ADJUSTMENT PULTE HOMES OF WASHINGTON INC. OCTOBER 2022 JOB NO.: 22035 300 20050 1000 SCALE: 1" = 100'KER S EY WAY N E L:\2022\22035\3 DEVELOPMENT\CAD\HOST DRAWINGS\PRELIMINARY PLAT MINOR ADJUSTMENT\22035E04-COMP-LOTS.DWG KING COUNTY PIERCE COUNTYR=45'R=45'53rd ST SE 54th ST SE CLASS IVLANDSLIDE AREASBOUNDARY DIAMOND VALLEY ESTATESCLASS IVLANDSLIDE AREASUDALL ST SEEVERGREEN WAY SE 55th ST. SE 56th ST. SE 57th ST. SEUDALL AVE SE50t h S T SE ORIGINAL PRELIMINARY PLAT LOT LINES AND ROW MINOR AMENDMENT TO PRE-PLAT LOT LINES AND ROW 339 of 350 EXHIBIT 15 September 26, 2023 Submitted via MyBuildingPermit.com City of Auburn Planning and Development Department 1 East Main Street Auburn, WA 98001 RE: Application for Reasonable Use Exception (RUE) ACC 16.10.080(G)(d): “Alteration of Class IV Landslide Hazard Area (Slopes over 40%)” Associated City of Auburn File Nos. PLT14-0006 and VAR16-0001 Parcel Nos. 322105-9010, 322105-9011, 322105-9030 and 322105-9037 Our Job No. 22817 On behalf of MainVue Homes, we are submitting the required documents for a Reasonable Use Exception (RUE) Application associated with the alteration of an isolated onsite area of 40% slopes within the Diamond Valley Estates Preliminary Plat (PLT14-0006). This alteration is subject to review through the RUE process as set forth in ACC 16.10.100(E)2(a), and was specifically referenced in the Findings of Fact summarized in the Hearing Examiners Decision issued February 8, 2017, as well as in Condition No. 41. In addition to the application being submitted via MyBuildingPermit.com, the following documents will be uploaded for routing and review: 1. Reasonable Use Exception Checklist. 2. Owner Letter of Authorization form dated August 29, 2023. 3. Final Environmental Impact Statement (FEIS) for Kersey III Preliminary Plat dated February 11, 2005. 4. Written Statement / Reasonable Use Justification Narrative prepared by Barghausen Consulting Engineers, Inc. dated September 25, 2023 in support of the RUE, including a detailed review of the criteria for approval of an RUE as set forth in ACC 16.10.150 (C). 5. “Steep Slope Areas Exhibit” prepared by Barghausen Consulting Engineers, Inc. dated September 1, 2023, referred to as Exhibit 1 in the Justification Narrative. 6. “Geotechnical Engineering and Geomorphology Services for Diamond Valley Estates” study prepared by GeoEngineers dated April 21, 2016, referred to as Exhibit 2 in the Justification Narrative. 7. “Geotechnical Evaluation – Reasonable Use Exception” report prepared by Earth Solutions Northwest (ESNW) dated September 15, 2023, referred to as Exhibit 3 in the Justification Narrative. This report confirms the proposed alteration will not cause a hazard to life, health, or property, as required per ACC 16.10.100(E)2(c)(i), as well as ACC 16.10.150(C)5 8. “RUE Grading Exhibit for Diamond Valley Estates” prepared by Barghausen Consulting Engineers Inc. dated September 12, 2023, referred to as Exhibit 4 in the Justification Narrative. 340 of 350339 of 350 EXHIBIT 16 City of Auburn Planning and Development Department -2-September 26, 2023 9. “Diamond Valley Estates Conceptual Grading Plan” prepared by APEX Engineering PLLC for PLT14-0006 dated July 11, 2016, referred to as Exhibit 5 in the Justification Narrative. 10. Pages 25-32 from the “Staff Report for the Preliminary Plat of Diamond Valley Estates—PLT14- 0006” prepared by the city of Auburn dated January 12, 2017, referred to as Exhibit 6 in the Justification Narrative. These excerpts summarize prior city staff review of the proposed alteration of this specific steep slope area under the provisions of VAR16-0001. City Staff recommended approval of the proposed alteration but the Hearing Examiners Decision (HEX) determined that the alteration could only be approved through the RUE process rather than through a Variance process. 11. “Findings of Fact, Conclusions of Law, and Final Decision” approving the preliminary plat of Diamond Valley Estates dated February 8, 2017, referred to as Exhibit 7 in the Justification Narrative. Pages 12-13 in the Final Decision summarize the above conclusion by the Hearing Examiner that the RUE process is the appropriate means for review/approval for an alteration of such critical areas, and Condition No. 41 on page 28 of the Final Decision authorizes the applicant to apply for an RUE. It is our understanding that the above documents comprise a complete Reasonable Use Exception (RUE) application for this specific request. A landscape plan is not required for this alteration as the entire area being altered is integral to the final roadway/plat development improvements that will be reviewed under a separate FAC application. If you have any questions or need additional information, please contact me at this office. Thank you. Respectfully, Thomas A. Barghausen, P.E. President TAB/mf 22817c.002.docx enc: As Noted cc: Vanessa Normandin, MainVue Homes Allison Rothstein, MainVue Homes Barry Talkington, Barghausen Consulting Engineers, Inc. Vicente Varas, Barghausen Consulting Engineers, Inc. 341 of 350 City of Auburn NOTICE OF PUBLIC HEARING Diamond Valley Estates (formerly Park Ridge) Critical Area Reasonable Use Exception CAO23-0010 The City of Auburn is issuing a Notice of Hearing for the following described project. The permit applications and listed studies may be reviewed at the Community Development Department at 1 East Main Street, 2nd Floor, Customer Service Center, Auburn, WA 98001. Proposal: Request for a Critical Areas Reasonable Use Exception (RUE) pursuant to ACC 16.10.150 and ACC 16.10.080(G)(d) for Class IV Landslide hazard area within a previously approved preliminary Plat of Diamond Valley Estates (PLT14-0006). The plat consists of four parcels totaling approx. 79.45 acres & proposed for approx. 200 single-family residential lots and ten tracts and associated clearing, grading and construction of stormwater facilities, public streets, utilities, and landscaping. The project site contains wetlands, streams, and geologic hazard areas. Location: The project site is located on the north and south sides of Evergreen Way SE, between Quincy and Udall AV SE, within the SW ¼ of Section 32-21-05, W.M. King Co. Assessor’s Parcel No's: 322105- 9010, -9011, -9030 & -9037 Notice of Application: November 6, 2023 Notice of Completeness: October 24, 2023 Permit Application: September 26, 2023 File No. CAO23-0010 Applicant/ Allison Rothstein, Director of Land Entitlement and Development Property Owner(s): MainVue Homes WA LLC 121 - 3rd Ave Kirkland, WA 98033 Agent: Thomas A. Barghausen, P.E. President Barghausen Consulting Engineers Inc. 18215 72nd Avenue South Kent, WA 98032 Studies/Plans Submitted With Application: •Final Environmental Impact Statement (FEIS) for Kersey III Preliminary Plat, City of Auburn, February 11, 2005. •Written Statement / Reasonable Use Justification Narrative, Barghausen Consulting Engineers, Inc., September 25, 2023. •“Steep Slope Areas Exhibit”, Barghausen Consulting Engineers, Inc., September 1, 2023 •“Geotechnical Engineering and Geomorphology Services for Diamond Valley Estates,” GeoEngineers April 21, 2016 •“Geotechnical Evaluation – Reasonable Use Exception, Proposed Diamond Valley Estates, 18XX Evergreen Way SE”, Earth Solutions Northwest (ESNW) September 15, 2023 •“RUE Grading Exhibit for Diamond Valley Estates”, Barghausen Consulting Engineers Inc., September 12, 2023, (Referred to as Exhibit 4 in the Applicant’s Justification Narrative) •“Diamond Valley Estates Conceptual Grading Plan” APEX Engineering PLLC for PLT14-0006, July 11, 2016, 342 of 350 EXHIBIT 17 NOTICE OF PUBLIC HEARING – CAO23-0010 (Continued) Page 2 of 3 •“Staff Report for the Preliminary Plat of Diamond Valley Estates—PLT14-0006”, City of Auburn, January 12, 2017 •“Hearing Examiner Final Decision on Preliminary Plat of Diamond Valley Estate,” February 8, 2017 Other Permits, Plans, and Approvals Needed: Variances, Deviations, Facilities Extension Agreement/Approval, Grading Permit, Storm Permit, Final Plat, Building Permits, Utility Permits, Forest Practice Permit. Wetland & Stream permits may be required by the Army Corps of Engineers or WA Dept. of Ecology or WA Dept. of Fish Wildlife. Statement of Consistency & List of Applicable Development Regulations: This proposal is subject to and shall be consistent with the Auburn City Code, Comprehensive Plan, & Public Works Engineering Design Standards. Public Comment Period: All persons may comment on this application. Written comments must be received prior to 5:00 p.m. on November 15, 2023 to the mailing address of 25 West Main Street, Auburn, WA, 98001-4998 or in-person at the hearing. Any person wishing to become a party of record shall include in their comments that they wish to receive notice of and participate in any hearings, if relevant, request a copy of decisions once made, and be made aware of appeal rights. For questions regarding this project, please contact Jeff Dixon, Planning Srvs. Manager at jdixon@auburnwa.gov or (253) 804-5033. Public Hearing: The Hearing Examiner will conduct a public hearing on the Critical Area Reasonable Use Exception at City Hall Council Chambers, 25 West Main Street, Auburn, WA 98001 on November 15, 2023 at 5:30 pm. 343 of 350 NOTICE OF PUBLIC HEARING – CAO23-0010 (Continued) Page 3 of 3 Project Site 344 of 350 345 of 350 Diamond Valley Estates RUE - CAO23-0010 BCE #22817 346 of 350 347 of 350 348 of 350 349 of 350 350 of 350