HomeMy WebLinkAboutAuburn Drainage Plan Vol 1 - Final Dec2011December 2009
Amended December 2011
City of Auburn
Comprehensive Stormwater
Drainage Plan
Volume 1 - Report
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CITY OF AUBURN COMPREHENSIVE
STORMWATER DRAINAGE PLAN
Prepared for
City of Auburn Public Works Department,
Auburn, Washington
December 2009
Amended December 2011
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CITY OF AUBURN COMPREHENSIVE
STORMWATER DRAINAGE PLAN
Prepared for
City of Auburn Public Works Department, Auburn, Washington
December 2009
Amended December 2011
City of Auburn Contract Number AG-C-302
Brown and Caldwell Project Numbers 132802 and 135347
701 Pike Street, Suite 1200
Seattle, WA 98101
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Table of Contents COMPREHENSIVE STORMWATER DRAINAGE PLAN
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TABLE OF CONTENTS
LIST OF FIGURES........................................................................................................................................................iv
LIST OF TABLES...........................................................................................................................................................v
LIST OF ABBREVIATIONS...........................................................................................................................................vi
EXECUTIVE SUMMARY...............................................................................................................................................1
ES-1 LOS Goals.......................................................................................................................................................2
ES-2 Evaluation of the Stormwater Utility.....................................................................................................4
ES-3 Implementation Plan............................................................................................................................7
ES-3.1 6-Year and 20-Year CIP..........................................................................................................7
ES-3.2 Monitoring..............................................................................................................................10
ES-3.3 Programmatic Measures for NPDES Compliance.................................................................11
ES-3.4 Recommendations for Additional Studies and Activities........................................................12
1. INTRODUCTION.....................................................................................................................................................1-1
1.1 Purpose and Objectives....................................................................................................................1-1
1.2 Approach and Document Organization.............................................................................................1-2
2. BACKGROUND......................................................................................................................................................2-1
2.1 Stormwater Utility..............................................................................................................................2-1
2.1.1 Organizational Structure.......................................................................................................2-2
2.1.2 Funding Mechanisms............................................................................................................2-3
2.2 Development Code and Design Standards Update..........................................................................2-5
2.3 Regulatory Considerations................................................................................................................2-6
2.3.1 Growth Management Act......................................................................................................2-7
2.3.2 Phase II Municipal Stormwater Permit..................................................................................2-8
2.3.3 Governmental Accounting Standards Board.........................................................................2-9
3. UTILITY POLICIES AND LEVEL OF SERVICE GOALS........................................................................................3-1
3.1 Level of Service Goals within Storm Drainage Utilities.....................................................................3-1
3.2 Levels of Service..............................................................................................................................3-2
3.2.1 Incorporation of Existing Comp Plan Storm Drainage Policies.............................................3-2
3.2.2 Levels of Service..................................................................................................................3-3
4. DRAINAGE SYSTEM..............................................................................................................................................4-1
4.1 Natural Drainage...............................................................................................................................4-1
4.1.1 Green River..........................................................................................................................4-1
4.1.2 White River...........................................................................................................................4-2
4.1.3 Mill Creek..............................................................................................................................4-2
4.1.4 Drainage Areas.....................................................................................................................4-3
4.1.5 Climate and Precipitation......................................................................................................4-4
4.1.6 Geology and Groundwater....................................................................................................4-5
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4.1.7 Soils and Runoff Potential....................................................................................................4-5
4.1.8 Land Use and Development.................................................................................................4-6
4.1.9 Flood Hazard Mapping.........................................................................................................4-7
4.2 Stormwater Drainage Infrastructure..................................................................................................4-7
4.3 Critical Facilities................................................................................................................................4-9
4.4 Water Quality..................................................................................................................................4-10
4.4.1 Existing Water Quality Conditions.......................................................................................4-10
4.4.2 Water Quality Regulatory Compliance................................................................................4-11
4.5 Existing Drainage Problems............................................................................................................4-11
4.6 Potential Future Drainage Problems...............................................................................................4-13
5. EVALUATION OF THE STORMWATER UTILITY..................................................................................................5-1
5.1 Hydraulic Investigation......................................................................................................................5-2
5.1.1 Review of Existing Model......................................................................................................5-2
5.1.2 Modeling Methodology..........................................................................................................5-3
5.2 Asset Life-Cycle Investigation...........................................................................................................5-4
5.2.1 Economic Life Analysis of Drainage Pipes...........................................................................5-5
5.2.2 Pump Station Condition Assessment....................................................................................5-6
5.3 Environmental Investigation..............................................................................................................5-7
5.4 Maintenance and Operations Investigation.......................................................................................5-8
6. CAPITAL IMPROVEMENTS...................................................................................................................................6-1
6.1 Project Prioritization..........................................................................................................................6-5
6.2 Ongoing Drainage Projects...............................................................................................................6-5
6.3 Proposed Drainage Projects.............................................................................................................6-7
6.4 Programmatic and Long-Term Drainage Planning Projects............................................................6-35
6.5 Repair and Replacement................................................................................................................6-36
6.5.1 Economic Life-Cycle Analysis Results................................................................................6-36
6.5.2 Pipes Identified for Intervention..........................................................................................6-37
6.5.3 Pipes Identified for Conditional Assessment.......................................................................6-38
6.5.4 Recommended Improvements for Economic Life-Cycle Analyses.....................................6-38
7. IMPLEMENTATION PLAN......................................................................................................................................7-1
7.1 6-Year and 20-Year CIP...................................................................................................................7-1
7.2 Monitoring.........................................................................................................................................7-4
7.2.1 Precipitation Monitoring........................................................................................................7-4
7.2.2 Flow Monitoring....................................................................................................................7-5
7.2.3 Water Level Monitoring.........................................................................................................7-5
7.2.4 Water Quality Monitoring......................................................................................................7-6
7.2.5 Monitoring Costs...................................................................................................................7-7
7.3 Programmatic Measures for NPDES Compliance............................................................................7-7
7.4 Recommendations for Additional Studies and Activities...................................................................7-8
7.4.1 Continue System Inventory...................................................................................................7-9
7.4.2 Update Criticality Database..................................................................................................7-9
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7.4.3 Risk Assessment: Asset Vulnerability Analysis..................................................................7-11
7.4.4 Evaluate Maintenance and Operations Program................................................................7-11
7.4.5 Incorporate Sustainability...................................................................................................7-11
7.4.6 Assist with Mill Creek Restoration Studies..........................................................................7-13
7.4.7 Downtown Stormwater Control Study.................................................................................7-13
8. FINANCIAL PLAN...................................................................................................................................................8-1
8.1 Past Financial Performance..............................................................................................................8-1
8.1.1 Comparative Financial Statements.......................................................................................8-1
8.2 Financial Plan...................................................................................................................................8-4
8.2.1 Utility Fund Structure............................................................................................................8-4
8.2.2 Financial Policies..................................................................................................................8-5
8.2.3 Capital Funding Plan............................................................................................................8-7
8.3 Available CIP Funding Assistance and Financing Resources..........................................................8-9
8.3.1 Utility Resources...................................................................................................................8-9
8.3.2 Outside Resources.............................................................................................................8-11
8.4 Financial Forecast...........................................................................................................................8-14
8.4.2 Financial Forecast..............................................................................................................8-14
8.4.3 City Funds and Reserve Balances......................................................................................8-16
8.5 Rate Structures...............................................................................................................................8-16
8.5.1 Existing Retail Rates...........................................................................................................8-16
8.5.2 Projected Retail Rates........................................................................................................8-17
8.6 Affordability.....................................................................................................................................8-17
8.7 Conclusion......................................................................................................................................8-18
9. LIMITATIONS.........................................................................................................................................................9-1
Report Limitations.................................................................................................................................................9-1
REFERENCES.....................................................................................................................................................REF-1
APPENDIX A: WESTERN WASHINGTON PHASE II MUNICIPAL STORMWATER PERMIT
APPENDIX B: GREEN RIVER PUMP OPERATIONS PROCEDURES PLAN
APPENDIX C: 2009 STORMWATER MANAGEMENT PLAN
APPENDIX D: SYSTEM INVENTORY AND MODELING
APPENDIX E: FLOW MONITORING PLAN
APPENDIX F: ECONOMIC LIFE ANALYSIS
APPENDIX G: PUMP STATION CONDITION ASSESSMENT
APPENDIX H: PHASE II NPDES STORMWATER PERMIT COMPLIANCE WORK PLAN
APPENDIX I: REVIEW OF OPERATION AND MAINTENANCE
APPENDIX J: PLANNING-LEVEL COST ASSUMPTIONS
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LIST OF FIGURES
Figure ES-1. Sub-basin drainage areas prioritized for evaluation and inventory ...................................................... 5
Figure ES-2. Timeline for NPDES Permit compliance ............................................................................................ 12
Figure 2-1. Public Works Department staff organizational chart ........................................................................... 2-3
Figure 4-1. Natural drainage features of the city of Auburn ................................................................................. 4-15
Figure 4-2. Drainage sub-basins for the Auburn stormwater utility ...................................................................... 4-17
Figure 4-3. Surface geology in the vicinity of the Auburn stormwater utility ........................................................ 4-19
Figure 4-4. Hydrologic soil groups for soils in the vicinity of the Auburn stormwater utility .................................. 4-21
Figure 4-5. Land use designations for the city of Auburn (Comp Plan, 2008) ..................................................... 4-23
Figure 4-6. Sub-basin priorities for system inventory .......................................................................................... 4-25
Figure 4-7. Drainage infrastructure for the Auburn stormwater utility .................................................................. 4-27
Figure 4-8. City and storm drainage critical facilities for the city of Auburn ......................................................... 4-29
Figure 4-9. Observed drainage problem locations for the Auburn stormwater utility ........................................... 4-31
Figure 4-10. City of Auburn downtown area and urban center ............................................................................ 4-33
Figure 5-1. Example of annualized cost of ownership with minimum highlighted in red (age 23) ......................... 5-6
Figure 6-1. Project locations, stormwater utility Capital Improvement Program .................................................... 6-3
Figure 6-2. Proposed capital improvements at Auburn Way S pump station, Phase 1 (CIP Project 11A) .......... 6-11
Figure 6-3. Proposed bypass piping at 2nd and G Streets (CIP Project 12) ....................................................... 6-17
Figure 6-4. Proposed capital improvements to relieve flooding at 30th Street NE (CIP Project 13A,
13B, and 13C) ............................................................................................................................. 6-21
Figure 6-5. Proposed capital improvements at West Main Street (CIP Project 14) ............................................. 6-25
Figure 6-6. Proposed capital improvements at 296th Street pond in West Hill area (CIP Project 15A and B) .... 6-29
Figure 6-7. Proposed capital improvements at Bry’s Cove Pond in West Hill area (CIP Project 16A and B) ...... 6-33
Figure 6-8. Future annual spending for repair and replacement given calculated optimal timing ........................ 6-37
Figure 6-9. Relative criticality of stormwater drainage pipes identified for condition assessment ....................... 6-24
Figure 7-1. Annual costs for 6-year CIP ................................................................................................................ 7-3
Figure 7-2. Timeline for NPDES Permit compliance ............................................................................................. 7-8
Figure 7-3. Distribution of pipe ages based on the City's current criticality database .......................................... 7-10
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LIST OF TABLES
Table ES-1-1. LOS Goals.........................................................................................................................................2
Table ES-1-2. Project Cost Summary for 6-Year and 20-Year CIP..........................................................................9
Table ES-1-3. Proposed Flow Monitoring Sites......................................................................................................10
Table 2-1. 2009 and 2010 Utility Rates for Storm Drainage Service.....................................................................2-4
Table 2-2. Federal, State, and City Regulations and Programs Relevant to the Auburn Stormwater Utility.........2-6
Table 3-1. LOS Goals............................................................................................................................................3-4
Table 4-1. Precipitation Frequency Data for Auburn, Washington, from NOAA Atlas 2........................................4-4
Table 4-2. FEMA Flood Insurance Rate Maps Applicable to the Auburn..............................................................4-7
Table 4-3. Stormwater Drainage Infrastructure Summary.....................................................................................4-9
Table 4-4 Critical Facilities..................................................................................................................................4-10
Table 4-5. List of Known High-Priority Drainage Problems.................................................................................4-12
Table 5-1. City of Auburn Stormwater Drainage Pump Station Inventory.............................................................5-6
Table 6-1. Summary of Ongoinga Capital Improvement Projects..........................................................................6-6
Table 6-2. Summary of Ongoing and Long-Term Programs to Address Drainage Infrastructure........................6-35
Table 7-1. Annual Project Cost Summary for 6-Year CIP.....................................................................................7-2
Table 7-2. Cost Summary for 20-Year CIP............................................................................................................7-4
Table 7-3. Proposed Flow Monitoring Sites...........................................................................................................7-5
Table 7-4. Proposed Water Level Monitoring Sites...............................................................................................7-6
Table 8-1. Statement of Revenues, Expenses, and Changes in Fund Net...........................................................8-2
Table 8-2. Statement of Net Assets......................................................................................................................8-3
Table 8-3. 2009–2014 Stormwater CIP.................................................................................................................8-7
Table 8-4. 2009-2019 Capital Financing Plan.......................................................................................................8-9
Table 8-5. Current System Development Charge Schedulea ..............................................................................8-10
Table 8-6. Financial Forecast..............................................................................................................................8-15
Table 8-7. Cash Balance Summary.....................................................................................................................8-16
Table 8-8. Existing Retail Stormwater Rates.......................................................................................................8-17
Table 8-9. Affordability Test................................................................................................................................8-18
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LIST OF ABBREVIATIONS
ac-ft acre-feet
ACC Auburn City Code
AKART all known, available, and reasonable methods of prevention, control, and treatment
BCE business case evaluation
BMP best management practice
CCTV closed circuit television
CERB Community Economic Revitalization Board
cfs cubic feet per second
CIP Capital Improvement Program
CMMS computerized maintenance management system
Comp Plan Comprehensive Plan for the City of Auburn (Land Use Plan)
CTED Department of Community, Trade, and Economic Development
CWA Clean Water Act
DUC designated urban center
Ecology Washington State Department of Ecology
EPA Environmental Protection Agency
ERP Ecosystem Restoration Project
ESA Endangered Species Act
ESU equivalent service unit
GASB Governmental Accounting Standards Board
GIS geographic information system
GMA Growth Management Act
GO general obligation
HPA hydraulic project approval
IDDE illicit discharge detection and elimination
LFC local facilities charge
LID low impact development
LOS level of service
M&O maintenance and operations
MEP maximum extent practicable
MHI median household income
MS4 municipal separate storm sewer system
NGVD29 National Geodetic Vertical Datum 1929
NAVD88 North American Vertical Datum 1988
NOAA National Oceanic and Atmospheric Administration
NPDES National Pollutant Discharge Elimination System
NSF non-single-family
PLC programmable logic controller
PWTF Public Works Trust Fund
R&R repair and replacement
RCW Revised Code of Washington
ROW right-of-way
RSI required supplementary information
SAMP Special Area Management Plan
SCADA supervisory control and data acquisition
SDC system development charge
COMPREHENSIVE STORMWATER DRAINAGE PLAN
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SEPA State Environmental Policy Act
SMP Shoreline Master Program
SOS Save Our Streets
sq ft square feet
SR State Route
SWMP Stormwater Management Program
TMDL total maximum daily load
UGA urban growth area
ULID Utility Local Improvement District
USACE U.S. Army Corps of Engineers
WRIA Water Resource Inventory Areas
ES-1
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P:\135347 Auburn Drainage Phase II\009 Storm Drainage Comprehensive Plan\Final\Auburn Drainage Plan Final Dec09(v2).doc
CITY OF AUBURN COMPREHENSIVE
STORMWATER DRAINAGE PLAN
EXECUTIVE SUMMARY
This Comprehensive Stormwater Drainage Plan (Drainage Plan) for the city of Auburn (City)
updates the previous plan, which was completed in August 2002. An update to the 2002 Drainage
Plan was necessary for several reasons including new regulatory requirements, continued growth and
development, the need for a comprehensive system inventory and an update of the list of projects
for the Capital Improvement Program (CIP). This comprehensive plan contains time frames which
are the intended framework for future funding decisions and within which future actions and
decisions are intended to occur. However, these time frames are estimates, and depending on factors
involved in the processing of applications and project work, and availability of funding, the timing
may change from the included time frames. The framework does not represent actual commitments
by the city of Auburn which may depend on funding resources available.
The purpose of this new Drainage Plan is to guide the City’s Stormwater Drainage utility with
respect to future activities and improvements for the stormwater drainage system. An asset
management approach was used to develop a work plan for the stormwater utility, consisting of the
following basic steps:
Review background information about the stormwater utility including the organizational
structure, funding mechanisms, and regulatory drivers (Chapter 2).
Examine City policies affecting the stormwater utility and develop specific level of service (LOS)
goals around those policies. LOS goals are policy- and community-based objectives for capital
facility infrastructure development, operation, maintenance, and other utility activities (Chapter 3).
Study and characterize the current and expected future conditions of the drainage system
(Chapter 4), including both natural and constructed drainage elements. The constructed drainage
system requires a detailed system inventory for use in analyses and asset management.
Evaluate the stormwater utility with respect to established LOS goals to identify gaps between
those goals and current or expected future service levels (Chapter 5). General types of evaluations
include hydraulic analyses of the drainage system, asset life-cycle analyses, environmental
assessments and investigations, review of maintenance and operations (M&O) practices, and
organizational investigations.
Develop alternatives to reduce or eliminate identified gaps in service. Such alternatives consist of
both capital improvement projects and non-structural, programmatic activities.
Recommendations for capital improvements are based on detailed hydraulic modeling and
criticality-based economic life-cycle analyses (Chapter 6).
Establish the implementation plan, which is the future work plan for the utility (Chapter 7).
Capital improvement projects from Chapter 6 are prioritized and placed into 6- year and 20-year
CIP time frames. Non-capital works recommendations such as flow monitoring, regulatory
Executive Summary COMPREHENSIVE STORMWATER DRAINAGE PLAN
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compliance, M&O improvements, and additional asset management activities are also included in
the implementation plan.
Provide a financial plan to support the costs associated with proposed improvements.
The following sections summarize the development of the Drainage Plan and outline the
recommendations contained in the implementation plan.
ES-1 LOS Goals
LOS goals provide a framework for the utility to assess its staffing levels, prioritize its resources,
justify its rate structure, and document its successes. It is important that LOS goals include clear
criteria to use in evaluating how well those goals are being met. Descriptions of LOS goals for the
stormwater utility were developed for this Drainage Plan; LOS goals are based on existing City
policies as presented in the 2008 Comprehensive Plan for the City of Auburn (Comp Plan). LOS
goals and associated City polices are listed in Table ES-1.
Table ES-1. LOS Goals
Item Policy description 2009 Drainage Plan LOS goal
Policy category: protection of public safety and property
1 The City shall seek to manage stormwater runoff within
the public right-of-way (ROW) to allow access to and
functionality of critical services such as hospitals, fire
and police stations, Emergency Operations Center,
maintenance and operations, and city hall. See policy
EN-57.
Surface water flooding will disrupt the function of critical facilities (i.e., with
floodwaters reaching the building structure, damaging the structure, and
permitting no ingress/egress) with an annual chance of occurrence of no greater
than 1 percent (i.e., an average recurrence interval of 100 years).
2 The City shall seek to manage stormwater runoff within
the city-owned public ROW to preserve mobility on
major transportation routes (i.e., arterial roads) and
residential roads. See policy EN-57.
Flooding disruption that inundates the city roadways to an impassable level with
an annual chance of occurrence of no greater than 4 percent (i.e., an average
recurrence interval of 25 years).
3 The City shall seek to manage stormwater runoff from
the public ROW to protect real property structures
(e.g., residences and businesses). See policy EN-57.
Flooding (surface water from ROW runoff entering premises and damaging
building structures) with an annual chance of occurrence of no greater than 2
percent (i.e., an average recurrence interval of 50 years).
4 The City shall seek to prevent erosion and landslides
related to construction, operation, and maintenance of
the publicly owned drainage system. See polices CF-
48 and EN-3.
No erosion or landslides resulting from public drainage infrastructure
construction, operation, or maintenance. No direct stormwater discharge will be
permitted on steep slopes.
5 The City shall seek to maintain storm drainage
infrastructure to ensure proper function of drainage
facilities. The City shall seek to seasonally maintain
storm drain inlets, conveyance, and outfalls to preserve
design conveyance capacity. See policies CF-40 and
EN-17.
The City will refine its maintenance practices and reallocate staff as needed to
address seasonal concerns, with an emphasis on maintaining facilities that have
a high “consequence of failure.” An example would be focusing extra M&O staff
on catch basin inlet cleaning during autumn when leaves are falling. Activities will
be documented within the City's CartêGraph computerized maintenance
management system (CMMS).
Policy category: reliability of the storm drainage infrastructure
6 The City shall seek to maintain an asset criticality
database to be used in prioritizing asset maintenance
and repair and replacement (R&R). See policies CF-40
and EN-17.
The existing criticality database (developed for this Drainage Plan) will be refined
to include more asset information, such as pipe material, diameter, age,
consequence of failure, etc. The criticality database will be validated using the
results of previous and ongoing M&O inspections. Activities will be documented
within the City's CartêGraph CMMS.
Executive Summary COMPREHENSIVE STORMWATER DRAINAGE PLAN
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Table ES-1. LOS Goals
Item Policy description 2009 Drainage Plan LOS goal
7 The City shall seek to perform condition assessments
of critical assets. See policies CF-40 and EN-17.
The City will develop and implement a condition assessment schedule for critical
assets as identified through criticality analyses of stormwater infrastructure
assets. Criticality is based on the risk and consequences of failure. Criticality
data will be stored in a criticality database, and condition assessment activities
will be documented in the CMMS.
8 The City shall seek to repair or replace system assets
before they exceed their economic lives. See policies
CF-40 and EN-17.
The number of high-criticality pipe segments beyond their economic lives will be
determined. After the criticality database inventory is complete, the City’s goal
will be to limit the number of pipe segments beyond their economic lives,
including setting specific numeric goals for replacement of those segments.
9 The City shall seek to conduct maintenance activities
in accordance with a schedule developed to comply
with Washington State Department of Ecology
(Ecology) requirements and asset criticality. See
policies CF-40, EN-12 and EN-17.
No deferred maintenance on all critical or Ecology-required assets. The City will
prioritize its inspection activities based on the combined “risk of failure” and
“consequence of failure” computed by the criticality database and meet current
NPDES inspection schedule (e.g., inspecting outfalls). The experience of M&O
staff should be incorporated into the criticality database (see item 6 above).
Inspection activities will be documented in the CMMS.
Policy category: protection of the environment
10 The City shall seek to provide pump redundancy and
backup power generators or dual power feeds at City-
owned and -operated drainage pump stations. See
policy EN-17.
Pump stations will be designed with two or more pumps to ensure proper
function during maintenance. Backup and/or dual-feed power supplies will be
installed as needed.
11 The City shall seek to comply with all federal, state,
and local regulations in operation and maintenance of
the City’s storm drainage infrastructure. See policy EN-
12.
Meet all relevant regulatory requirements. Examples include complying with
NPDES Phase II inspection cycle, performing all necessary ESA consultations,
etc.
12 The City shall protect and preserve existing native
vegetation and drainage courses while maintaining
their conveyance capacity. See policy CF-45.
No net loss of native vegetation (in terms of area) or natural drainage systems (in
terms of stream length) to maintain existing habitat along drainage ways. This
does not apply to constructed or maintained facilities.
13 The City shall seek to reduce runoff volumes and
pollutant loads associated with new development. See
policy EN-15.
The City will comply with the elements of the NPDES Phase II Stormwater
Permit and implement an Ecology-equivalent stormwater manual for new
development. Identify appropriate areas and provide guidance for the
implementation of low impact development (LID) drainage management
measures by new development and redevelopment (including City-owned
properties).
14 The City shall seek to evaluate drainage utility activities
to emphasize sustainability. See policy CF-40.
City staff will identify specific areas to measure sustainability by examining how
storm drainage utility operations affect energy resources and natural resources.
City staff will benchmark practices and log changes over the next planning
period.
15 The City shall continue to participate in regional storm
drainage, water resources, and water quality planning
efforts. See policies CF-48 and EN-12.
The City will continue to actively participate in developing and implementing
regional water quality planning and flood hazard reduction efforts within the
Green River, Mill Creek, and White River drainage basins.
Policy category: storm drainage utility financial performance
16 The City shall continue to fund and provide storm
drainage services through the existing storm drainage
utility. See policy CF-40.
The City's storm drainage utility should be responsible for implementation,
maintenance, and operation of the City's drainage system. Goal of 100% of cost
of drainage service delivery recovered via storm drainage utility fees. Seek
opportunities to provide public drainage benefits through grants funding and/or
development partnerships where applicable.
17 The City shall assess appropriate rates and system
development charges (SDCs) to fund the ongoing
maintenance, operation, and capital expenditures of
the utility, in accordance with the Drainage Plan. See
policy CF-41.
Periodic cost of service studies shall be completed to reassess the monthly
service fees and SDCs. Updates to coincide with 6-year CIP updates.
Executive Summary COMPREHENSIVE STORMWATER DRAINAGE PLAN
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Table ES-1. LOS Goals
Item Policy description 2009 Drainage Plan LOS goal
18 The City shall seek to track the cost of claims as a
metric. See policy CF-41.
City staff will summarize the annual costs of claims for the recent past to
establish a baseline measurement of existing practices. If the current costs are
deemed excessive, City staff will define methods to reduce the risk of claims and
measure its progress at reducing the overall cost of claims.
19 The City shall seek to track elements of CIP
implementation: (1) individual schedule, (2) project
budget accuracy, and (3) overall performance in
implementing CIP. See policies CF-40 and CF-48.
City staff will summarize current methods for CIP implementation to create a
baseline (e.g., schedule and costs) against which future improvements can be
evaluated.
Policy category: customer satisfaction
20 The City shall seek to evaluate and strive to maintain
customer satisfaction with drainage utility service
delivery. See policy CF-40.
To effectively measure the public perception of utility performance, City staff will
conduct the following: (1) summarize annual customer complaint reports, (2)
communicate proactively with community and stakeholders regarding drainage
infrastructure improvements, and (3) comply with Stormwater NPDES Phase II
Permit requirements for public education and outreach.
21 The City shall seek to build, operate, and maintain
drainage utility infrastructure within an overarching goal
of protecting employee safety. See policy CF-40.
City staff will track health and safety incidents to create a baseline against which
to evaluate future improvements.
ES-2 Evaluation of the Stormwater Utility
A series of investigations were conducted to evaluate the stormwater utility and identify gaps
between existing service levels and the desired LOS goals. Such investigations typically fall into one
of five basic types of investigations: hydraulic, economic (i.e., asset life-cycle), environmental, or
maintenance and operations. The following paragraphs summarize the evaluations conducted as part
of the development of this Drainage Plan:
Hydraulic. The City’s existing XP-SWMM1 hydraulic model was reviewed and compared with
infrastructure data contained in the City’s geographic information system (GIS). Data gaps and
inconsistencies between the two data sources led the City to embark on an effort to develop an
improved and more-detailed drainage system inventory, which would serve as the basis for a new
hydraulic model. MIKE URBAN2 software was selected for this purpose because it would be
consistent with the City’s sanitary sewer model and uses common GIS data formats. A complete
update of the City’s drainage system inventory will require a substantial effort; thereby
necessitating a phased approach. The system was divided and prioritized for evaluation by
drainage sub-basin (Figure ES-1). This Drainage Plan focuses on high- and medium-priority sub-
basins. Low-priority sub-basins and sub-basins without a designated priority were deferred to
future efforts (see recommendations future activities in the implementation plan).
1 XP-SWMM is a program developed by XP Software for hydrodynamic modeling of stormwater and wastewater
collection systems. XP-SWMM uses the SWMM5 engine, which is public domain modeling software distributed by the
EPA. Information about XP-SWMM software can be found at http://www.xpsoftware.com/products/xpswmm/.
2 MIKE URBAN is a GIS-integrated, modular software program developed by the Danish Hydraulic Institute for
modeling water distribution and collection systems. The stormwater module is internally powered by the SWMM5
engine, which is public domain software distributed by EPA. Information about MIKE URBAN software can be found
at http://www.dhigroup.com/Software/Urban/MIKEURBAN.aspx.
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COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 5,280 feet
December 2009
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_FigES-1(priorities).mxd
FIGURE ES-1
SUB-BASIN DRAINAGE AREAS
PRIORITIZED FOR EVALUATION
AND INVENTORY
0.500.5
Miles
[N
L E G E N D
Roadway
Auburn City Boundary
Evaluation/Inventory Priority
High
Medium
Low
Future Efforts
NOTES:
Sub-basin delineations are based on the 2002 Drainage Plan and are used for reference.
Gray areas appearing as gaps between sub-basins are areas adjacent to rivers that drain directly to those rivers.
back of Figure ES-1.
Executive Summary COMPREHENSIVE STORMWATER DRAINAGE PLAN
ES-7
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Economic. Asset life-cycle investigations also require detailed system information. An economic
life analysis of the utility’s drainage pipes was conducted using available data in system inventory.
Those data within the system inventory that are used for such an analysis (e.g., pipe material, pipe
age, and proximity to critical facilities) form what is referred to as a criticality database. The
economic life analysis examined the probability of failure and the costs associated with a failure
to determine the optimal timing for intervention and to prioritize maintenance activities.
Environmental. Environmental investigations centered on regulatory compliance for the
National Pollutant Discharge Elimination System (NPDES) Permit. A legal requirements analysis
was conducted and stormwater management programs, codes, standards, processes, and
documentation protocols were assessed, including interviews with appropriate staff. The results
were used to identify gaps and develop potential actions to comply with the NPDES Permit
conditions over the 5-year Permit period. Some policy issues and potential compliance strategies
were also identified. A compliance work plan was developed, as well as Stormwater Management
Plans (SWMPs) for 2008 and 2009.
Maintenance and operations. A preliminary evaluation of M&O activities was conducted for
this Drainage Plan. Current ditch and drainage line maintenance activities were examined and the
City’s CartêGraph computerized maintenance management system (CMMS) software was
reviewed. Recommendations were made for ways to optimize M&O activities including a list of
key elements for the development of a structured M&O program.
ES-3 Implementation Plan
The implementation plan brings together information from the system evaluation to form a work
plan of future activities for the stormwater utility. The implementation plan consists of 6-year and
20-year CIP, recommendations including monitoring and data collection, activities for NPDES
compliance, and recommendations for using asset management strategies to improve utility M&O
with an outlook on long-term sustainability.
ES-3.1 6-Year and 20-Year CIP
The 6-year CIP focuses mainly on existing flooding problems where recent storm events have
revealed deficiencies in the drainage system. Most of the capital improvement projects are designed
to mitigate flooding in these areas and are expected to provide substantial and immediate benefits.
The 6-year CIP also contains ongoing drainage projects developed prior to, or during the
completion of this Drainage Plan and ongoing programmatic efforts, such as the drainage utility’s
participation in the Save Our Streets (SOS) program.
As current problems are addressed in the near term, the focus of the CIP begins to shift toward a
more proactive program, where repair or replacement of storm drainage assets can be prioritized
according to the optimal timing for interventions. Ultimately, this process will allow the City to meet
customer service levels, effectively manage risks, and minimize the City’s costs of ownership.
After existing drainage problems are addressed, the City will begin to shift its priorities away from
responding to known drainage problems toward managing existing storm drainage assets to ensure
that LOS goals are continuously met. These long-range capital improvements will focus on
Executive Summary COMPREHENSIVE STORMWATER DRAINAGE PLAN
ES-8
Use of contents on this sheet is subject to the limitations specified at the end of this document.
programmatic activities, such as developing a repair and replacement schedule that examines asset
inspection and maintenance results to identify assets that are nearing the end of their economic life.
The 20-year CIP adds projects identified through asset life-cycle investigations, or projects that
address long-term regional issues (e.g., the impact of Mill Creek aggradation on storm drainage
discharge capacity).
Table ES-2 lists all 19 capital improvement projects included in this Drainage Plan and lays out
annual expenditures for the 6-year and 20-year CIP time frames.
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Executive Summary COMPREHENSIVE STORMWATER DRAINAGE PLAN
ES-10
Use of contents on this sheet is subject to the limitations specified at the end of this document.
ES-3.2 Monitoring
Evaluating the adequacy of the stormwater drainage system and analyzing potential capital
improvements require extensive data to produce accurate and reliable results. Such data includes not
only infrastructure data such as pipe sizes, invert elevations, and outfall locations, but also
stormwater data such as flow rates, runoff volumes, and flooding elevations. The City should
continue to collect these types of data and store them in a consistent and organized manner.
Table ES-3 summarizes specific recommendations for additional monitoring data collection.
Table ES-3. Proposed Flow Monitoring Sites
Site number Location Purpose
Start
year
Approximate
duration
RG-01 City Hall (Main and Division
Streets)a
Characterize rainfall-runoff processes and design for
drainage of stormwater runoff
current Indefiniteb
Q-Pipe-B4 Parking lot near Henry Rd. Provide data for hydrologic and hydraulic model
calibration (Basin B)
2010 1 to 2 wet
seasonsc
Q-Pipe-C346 G St. SE and 2nd St. SE Quantify flows to support modeling and design for CIP
Project 11 in Drainage Plan
2010 1 to 2 wet
seasonsc
Q-Pipe-B86 B St. SE and 12th St. SE Quantify flows to support modeling and design for CIP
Project 10 in Drainage Plan
2009 1 to 2 wet
seasonsc
Q-Pipe-C26 M St. SE and Auburn Way S Quantify flows to support modeling and design for CIP
Project 10 in Drainage Plan
2009 1 to 2 wet
seasonsc
Q-Pipe-C59 Dogwood St. near Auburn Way S Data to calibrate model for analysis of potential capital
improvement project
2011 1 to 2 wet
seasonsc
Q-Pipe-P2 Near West Main and SR 167 Quantify flows to support modeling and design for CIP
Project 13 in Drainage Plan
2010 1 to 2 wet
seasonsc
Q-Pipe-I10 30th St. NE near airport Quantify flows to support modeling and design for CIP
Project 12 in Drainage Plan
2009 1 to 2 wet
seasonsc
WL-Mill-01 Mill Creek at 37th St. NW Evaluate stages in Mill Creek and assess backwater
effects on drainage system
2011 10 yearsd
WL-Mill-02 Mill Creek at 29th St. NW Evaluate stages in Mill Creek and assess backwater
effects on drainage system
2011 10 yearsd
WL-Mill-03 Mill Creek at 15th St. NW Evaluate stages in Mill Creek and assess backwater
effects on drainage system
2011 10 yearsd
WL-Mill-04 Mill Creek at West Main St. Evaluate stages in Mill Creek and assess backwater
effects on drainage system
2011 10 yearsd
WL-Pond-01 West Airport Pond at 30th St. NW Evaluate pond capacity to support design analyses for
CIP Project 12 in Drainage Plan
2009 2 yearsc
WL-Pond-02 A St. SE and 17th St. SE Evaluate pond capacity to support design analyses for
CIP Project 10 in Drainage Plan
2009 Indefinitee
WL-Pond-03 D St. SE and 21st St. SEa Evaluate pond capacity to support design analyses for
CIP Project 10 in Drainage Plan
2009 Indefinitee
WL-Pond-04 South 296th St. near 55th Ave. S Evaluate pond capacity to support design analyses for
CIP Project 14 in Drainage Plan
2011 6 yearsc
WL-Pond-05 South 296th St. near 57th Pl. S Evaluate pond capacity to support design analyses for
CIP Project 15 in Drainage Plan
2012 6 yearsc
WL-Pond-06 U St. SE and 29th St. SE Evaluate pond capacity and infiltration rates to assess
need for improvements
2012 Indefinitee
Executive Summary COMPREHENSIVE STORMWATER DRAINAGE PLAN
ES-11
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Table ES-3. Proposed Flow Monitoring Sites
Site number Location Purpose
Start
year
Approximate
duration
WL-Pond-07 M St. SE and 37th St. SEa Evaluate pond capacity and infiltration rates to assess
need for improvements
2012 Indefinitee
WL-Pond-08 Lakeland South Pond 1 Monitor water level to evaluate hazard risk (dam safety) 2012 Indefinitee
WL-Pond-09 Lakeland South Pond 2 Monitor water level to evaluate hazard risk (dam safety) 2012 Indefinitee
WL-Pond-10 Lakeland East Pond Monitor water level to evaluate hazard risk (dam safety) 2012 Indefinitee
WL-Pond-11 Mill Pond (Oravetz Rd. SE) Monitor water level to evaluate hazard risk (dam safety) 2012 Indefinitee
a. Existing monitoring site; continue monitoring but consider equipment upgrades.
b. To be continually reevaluated; however, data should be collected continuously for future monitoring needs.
c. Data to support CIP needs at least one wet season of good data—approximately October through April; if sufficiently large storms occur during the first
season, then Year 2 data may not be necessary.
d. Based on need to examine backwater effects on system, if new capital improvements are identified for Mill Creek, additional years may be needed.
e. To be continually reevaluated; if data indicate stormwater pond is performing adequately or has low risk of failure then monitoring could cease.
ES-3.3 Programmatic Measures for NPDES Compliance
The city of Auburn is covered by the Western Washington Phase II Municipal Stormwater Permit,
which regulates stormwater discharges from the City’s municipal stormwater system. The City has
been actively engaged in compliance activities since the issuance of the Permit, including the
following:
Stormwater management plan administration
Public education and outreach
Public involvement
Illicit discharge detection and elimination
Control of runoff from development, redevelopment, and construction sites
Pollution prevention and municipal operation and maintenance
Monitoring.
Figure ES-2 shows a timeline for compliance with specific elements of the Permit.
Executive Summary COMPREHENSIVE STORMWATER DRAINAGE PLAN
ES-12
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Begin keeping records for
inspections,
maintenance, and
enforcement
End of
First
Permit
Ma
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c
h
3
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,
2
0
0
8
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9
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,
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1
2
Permit
Effective
Fe
b
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6
,
2
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0
7
Submit first SWMP and first
Annual Report to Ecology
and post on website
Begin tracking
Permit costs
Implement
public
education
program
Implement BMPs for municipal operations
Update codes, standards,
SOPs, inspections,
maintenance, and
documentation for
municipal operations and
public drainage system
O&M Complete storm
system map
Fully
implement
SWMP
Complete assessment of
outfall
Continue existing
programs
Begin hotline for
reporting illicit
discharges
Update codes, standards, SOPs, inspections, enforcement,
maintenance, and documentation for IDDE
Conduct responder IDDE training
Conduct general IDDE
training
Conduct municipal activities
training
Adopt new stormwater manual*Conduct controlling construction runoff training*
Develop SWPPPs for City
facilities
Implement monitoring
preparation requirements
Begin monitoring outfalls for illicit discharges
Update codes, standards, SOPs, inspections,
enforcement, maintenance, and documentation
for controlling construction runoff*
Acronym Key:
BMP: best management practice
IDDE: illicit discharge detection and
elimination
O&M: operation and maintenance
SOP: standard operating procedure
SWMP: stormwater management plan
SWPPP: Stormwater pollution prevention plan
Note:Requirements
marked with an asterisk
(*) were delayed from
August 16, 2009 to
February 16, 2010 per
permit modifications
dated June 17, 2009.
Select potential monitoring
locations.
Figure ES-2. Timeline for NPDES Permit compliance
ES-3.4 Recommendations for Additional Studies and Activities
Additional recommendations were made for activities that will support asset management and
ongoing M&O; specifically, the following recommendations were made:
Continue system inventory. The level of effort required to complete the system inventory
requires a phased approach. Updates completed during the development of this Drainage Plan
focused on high- and medium-priority sub-basins. Additional data inventory activities will need
to be completed for low priority sub-basins and sub-basins in the West Hill, Lea Hill, and
Southeast areas of the City. After those phases are complete the system inventory should be
continually updated (e.g., annually) and reviewed for quality control.
Update criticality database. Detailed infrastructure data are stored in an asset criticality
database, which should be developed and maintained in conjunction with the system inventory.
As the criticality database is improved the economic life model can be updated and R&R
priorities can be refined.
Executive Summary COMPREHENSIVE STORMWATER DRAINAGE PLAN
ES-13
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Risk Assessment: Asset Vulnerability Analysis. The City should conduct a vulnerability
analysis on the entire stormwater drainage system to examine the potential for natural disasters
such as flood, erosion, earthquake or volcanic activity to cause system failures. Of particular
concern are critical facilities such as pump stations, major drainage lines, hospitals, fire and police
stations, Emergency Operations Center, M&O, and city hall. The probabilities of failure
associated with natural hazards should be weighed with the consequences of failure to determine
if action is necessary and to identify appropriate mitigation measures.
Optimize maintenance and operations program. Optimizing M&O activities through an
asset management-based program will lead to increased effectiveness in managing risk, public
perception, regulatory compliance, and costs to the utility. The City should continue to develop
an M&O program to provide strategies that will optimize resources, connect staff availability,
identify critical assets, and prioritize M&O activities.
Incorporate sustainability. Under the “protection of the environment” policy category in
Table ES-1, the City has a policy to evaluate drainage utility activities with regard to sustainability.
The City should take steps toward incorporating sustainability with utility activities.
Recommended actions include developing specific and measurable sustainability goals for the
utility and establishing standards that incorporate sustainability into project and activities.
Assist with Mill Creek Restoration Studies. Restoring Mill Creek will not only improve water
quality and habitat, but could also improve flooding and drainage. As restoration projects are
developed, the City could offer their assistance with predesign studies. For example, the City
could use its planned monitoring effort in Mill Creek to provide valuable hydraulic grade data to
either demonstrate the need for channel improvements or support the restoration design process.
Downtown Stormwater Control Study. Development in downtown area is no longer exempt
from stormwater control requirements given recent changes to the NPDES Permit. The City
should conduct a study of potential stormwater development standards for the downtown area so
that the City can continue providing incentives for redevelopment while meeting the NPDES
Permit requirements. Options include onsite water quality treatment, onsite water quality
treatment in combination with flow duration control, and offsite stormwater control facilities.
A timeline was developed to illustrate how each of the recommended activities in the
implementation plan fit together within 6-year and 20-year time frames. This timeline is presented
on the following page.
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Phase 1
2009 2010 2011 2012 2013 2014 2015 2020 2025 2030
1. R Street SE Storm Drain Improvement
2. SCADA (Telemetry) Upgrades
3. White River Storm Pump Station Replacement, Phase 1
4. White River Storm Pump Station Replacement, Phase 2
5. Peasley Canyon Culvert Replacement
6. M Street NE/Harvey Road & 8th Street Improvements
7. Les Gove Neighborhood Improvement
8. West Valley Highway
9. Port of Seattle Mitigation Project
11. Improvements for Auburn Way S, SR 18 at M and 17th St.
12. Bypass at 2nd Street SE and G Street SE
13. Relieve 30th Street NE Area Flooding
14. West Main St. Pump Upgrade
15. South 296th Street Pond Expansion
16. Bry’s Cove Pond Expansion
17. Storm Drainage Infrastructure Repair & Replacement
18. Arterial Preservation Utility Improvements
19. SOS Utility Improvements
20. Regional Drainage Improvement Projects
Q1 Q2 Q3 Q4
Phase 1 Phase 2
Phase 2
Phase 1 Phase 2
Q-Pipe-B4. Parking lot near Henry Road
Q-Pipe-C346. G Street SE and 2nd Street SE
Q-Pipe-B86. B Street SE and 12th Street SE
Q-Pipe-C26. M Street SE and Auburn Way S
Q-Pipe-C59. Dogwood Street
Q-Pipe-P2. Near West Main and SR 167
Q-Pipe-I10. 30th Street NE near airport
WL-Mill-01,02,03,04. Mill Creek Profile
WL-Pond-01. West Airport Pond
WL-Pond-02. A Street SE and 17th Street SE
WL-Pond-03. D Street SE and 21st Street SE
WL-Pond-04. South 296th Street at 55th Ave S
WL-Pond-05. South 296th Street at 57th Place S
WL-Pond-06. U Street SE and 29th Street SE
WL-Pond-07. M Street SE and 37th Street SE
WL-Pond-08,09,10,11. Large Ponds for Dam Safety
Detailed 6-year CIP Timeframe
SWMP administrative tasks
Develop new stormwater manual
Update codes, standards, SOPs, maintenance for IDDE
Develop SWPPPs for City facilities
En
d
o
f
F
i
r
s
t
Pe
r
m
i
t
Review and refine LOS Goals
Establish specific sustainability goals and standards
Complete system inventory
Conduct new economic life-cycle analyses
Update, check, revise system inventory
Update criticality database
Evaluate M&O program
Expand functionality of Cartegraph CMMS software
Low Priority and West Hill Lea Hill
Remaining 20-year CIP Summary
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
IMPLEMENTATION PLAN ACTIVITIES TIMELINE
City of Auburn Comprehensive Stormwater Drainage Plan
Southeast
Additional Studies and Activities (Section 7.4)
NPDES Compliance (Section 7.3)
Monitoring (Section 7.2)
CIP (Section 7.1)
Data feed
Activity
Optional
K E Y
Continued
into next
permit term
Risk Assessment –Asset Vulnerability Analysis
Assist with Mill Creek Restoration Studies
Public education and outreach, IDDE and outfall monitoring
Update codes, standards, SOPs, maint. for construction, O&M
10. M&O Facility Improvements
Evaluate Stormwater Management for Downtown Area
Phase 1 Phase 2
Phase 1
Phase 2 Phase 3
1-1
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P:\135347 Auburn Drainage Phase II\009 Storm Drainage Comprehensive Plan\Final\Auburn Drainage Plan Final Dec09(v2).doc
CITY OF AUBURN COMPREHENSIVE
STORMWATER DRAINAGE PLAN
1. INTRODUCTION
This Comprehensive Stormwater Drainage Plan for the City of Auburn, Washington, updates the
previous plan that was completed in August 2002. An update to the 2002 Drainage Plan was
necessary for several reasons:
The Washington State Growth Management Act (GMA) requires planning documents to be
reassessed and updated periodically.
New and updated regulatory and permitting requirements such as those associated with the
National Pollutant Discharge Elimination System (NPDES) needed to be addressed.
Continued growth and development, especially in newly annexed areas, requires new and revised
evaluations of the stormwater drainage system to maintain an understanding of existing and
potential problems throughout the utility service area.
A comprehensive system inventory was needed to account for utility assets and to improve the
accuracy of the analyses used to develop capital improvement projects.
The Capital Improvement Program (CIP) proposed in the 2002 Drainage Plan needed to be
reevaluated to account for completed projects, changes in system conditions, and new
development, as well as to incorporate new financial information.
This comprehensive plan contains time frames which are the intended framework for future funding
decisions and within which future actions and decisions are intended to occur. However, these time
frames are estimates, and depending on factors involved in the processing of applications and
project work, and availability of funding, the timing may change from the included time frames. The
framework does not represent actual commitments by the city of Auburn which may depend on
funding resources available.
1.1 Purpose and Objectives
The purpose of the Drainage Plan is to guide the City’s Stormwater Drainage utility with respect to
future activities and improvements. To fulfill this stated purpose the following objectives were
achieved:
Evaluate environmental, social, and regulatory drivers to develop level of service (LOS) goals for
capital facility infrastructure development, operation, maintenance, and other key elements of
utility management.
Create a comprehensive stormwater drainage system inventory that incorporates currently
available infrastructure data into a digital database that can be directly linked with the hydraulic
model used for analyzing the system.
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Perform hydraulic modeling analysis to evaluate system capacity focusing on known problems
and areas where data are available for model calibration.
Evaluate the condition of the City’s stormwater pumping stations, and perform an economic life
analysis of existing assets within the stormwater collections system to develop recommendations
for future rehabilitation, refurbishment, repair and replacement (R&R) activities.
Develop a monitoring plan to collect data that can be used to evaluate the performance of system
assets, as well as to calibrate hydraulic models in future modeling efforts.
Develop a CIP by sustainably meeting required customer service levels, effectively managing
risks, and minimizing the City’s costs of drainage asset ownership.
Develop recommendations for improving the maintenance and operations (M&O) program.
Prioritize capital improvement projects and R&R activities to accommodate both 6-year and 20-
year funding frameworks.
Incorporate information and activities from concurrent NDPES compliance planning.
1.2 Approach and Document Organization
Asset management principles were used throughout the development of this Drainage Plan. An asset
management approach is designed to deliver defined service levels at an acceptable risk with the
lowest life-cycle cost. Given this approach, a study phase was initiated to develop LOS goals, analyze
the system with respect to those goals, and develop recommendations for achieving those goals.
This Drainage Plan is organized with that general process in mind, and has been structured in a way
that focuses on the actions the utility will take while implementing the plan. In most cases,
supporting documentation and background information will be included in appendices rather than
chapters of the Drainage Plan. The Drainage Plan is organized into the following chapters:
Chapter 1 Introduction: describes the reasons for developing an updated Drainage Plan, and also
states the purpose and objectives of the Drainage Plan
Chapter 2 Background: provides background information regarding the stormwater utility and
regulatory drivers for developing LOS goals
Chapter 3 Utility Policies and Level of Service Goals: specifies the LOS goals used to develop
capital improvements and future M&O activities
Chapter 4 City of Auburn Drainage System: describes the existing and future conditions of the
City’s drainage system
Chapter 5 System Analysis: describes methodologies used to evaluate asset conditions and analyze
system capacity
Chapter 6 Capital Improvements: describes recommended capital improvement projects
including cost estimates and conceptual figures
Chapter 7 Implementation Plan: prioritizes capital improvement projects and lays out a future
work plan
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Chapter 8 Financial Plan: identifies the total cost of providing stormwater drainage services and
provides a program for the utility to remain viable during execution of the CIP.
Chapter 9 Limitations
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P:\135347 Auburn Drainage Phase II\009 Storm Drainage Comprehensive Plan\Final\Auburn Drainage Plan Final Dec09(v2).doc
CITY OF AUBURN COMPREHENSIVE
STORMWATER DRAINAGE PLAN
2. BACKGROUND
This chapter provides a brief description of the stormwater utility, organizational structure, and
funding mechanisms, as well as an overview of the federal, state, and local regulations that can affect
stormwater management in the city.
2.1 Stormwater Utility
Recurring local flooding, continued development, and degradation of water resources led the city of
Auburn to form a public utility in 1986 to provide ongoing management of a storm drainage
system1. Chapter 35.67 of the Revised Code of Washington (RCW) provides for the creation and
funding of a public sewerage system and associated drainage systems. Establishment of a storm
drainage utility is found in Chapter 13.48 of the Auburn City Code (ACC). The general purpose of
the storm drainage utility is to avoid public nuisances and promote public health, safety, and welfare
by reducing the likelihood of:
Inundation of public and private property by stormwater
Uncontrolled volume increase, rate or contaminated load of runoff
Degradation of existing water resources such as creeks, streams, rivers, ponds, lakes,
groundwater, and other water bodies
Degradation of water used for contact recreation, aquatic habitat, and aesthetic quality
Jeopardy to the community’s compliance with federal flood insurance programs.
The City’s current storm drainage system consists of 197 miles of pipe, 27 miles of ditches, more
than 10,000 catch basins and manholes, 159 storage facilities, and six stormwater pump stations
designed to convey rainwater from various collection points for eventual discharge to nearby
receiving waters. A detailed description of the drainage system is provided in Chapter 4.
Sections 2.1.1 and 2.1.2 below describe the organizational structure of the stormwater utility and
funding mechanisms, respectively.
1 A public utility for stormwater management was established by City of Auburn Ordinance No. 4193 on December 15,
1986.
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2.1.1 Organizational Structure
The City’s stormwater utility is organized under the larger umbrella of the Public Works
Department. This department covers five basic areas of responsibility:
Water Utility Program
Sanitary Sewer Utility Program
Storm Drainage Utility Program
Transportation Program
Equipment Rental Program.
Under these programs the Public Works Department carries out long-term planning, budget
management, interaction and regulation of development, management of capital improvements, and
M&O for the associated City facilities. Given these program responsibilities, the Public Works
Department is divided into the Water Division, Sanitary Sewer Division, Storm Drainage Division,
Street Division, Engineering Division, and Equipment Rental Division.
The organizational structure of personnel within the Public Works Department is arranged such that
some groups service multiple divisions and programs (see Figure 2-1, additional detail for Utilities
section provided for clarity). Engineering services for storm drainage facilities are provided by the
Utilities Engineering section, which also provides engineering services for water and sanitary sewer
facilities. Other groups within the Public Works Department that support stormwater drainage-
related activities include Maintenance and Operations (M&O); one of the five divisions within M&O
is dedicated to stormwater facilities.
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Public Works Director
City Engineer/
Assistant Director
Senior Project
Engineer
Development
Engineer
Development
Support Supervisor
Construction
Manager
Survey Supervisor
Contract
Administrator
General Services/
Fleet Manager
Street Division
Manager
Sewer Division
Manager
Water Operations
Manager
Water Distribution
Manager
Storm Division
Manager
M & O Support
Manager
Assistant City Engineer
Maintenance &
Operations Manager Transportation Manager Utilities Engineer
Figure 2-1. Public Works Department staff organizational chart
2.1.2 Funding Mechanisms
The following section provides adapted text from ACC, Title 13: Water, Sewers and Public Utilities,
Chapter 13.48, Storm Drainage Utility, §13.48.060, Authority to establish rates. Per the ACC, the
City has established rate classifications, service charges, and various fees and charges to pay for the
following costs:
The development, adoption, and implementation of a comprehensive storm drainage utility
master plan
The debt service and related financing expenses of the construction and reconstruction of storm
drainage and water quality facilities required for the management of storm and surface waters that
benefit the service area but not presently in existence
The operation, repair, maintenance, improvement, replacement, and reconstruction of storm
drainage facilities that benefit the present service area (e.g., capital improvement projects to
increase system capacity in accordance with LOS goals).
The purchase of a fee or lesser interest, including easements, in land which may be necessary for
the storm drainage system in the service area including, but not limited to, land necessary for the
installation and construction of storm drainage facilities and all other facilities which are
2: Background COMPREHENSIVE STORMWATER DRAINAGE PLAN
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reasonably required for proper and adequate management of stormwaters for the benefit of the
service area
The costs of monitoring, inspection, enforcement, and administration of the utility including, but
not limited to, water quality surveillance, private system maintenance inspection, construction
inspection, and other activities which are reasonably required for the proper and adequate
implementation of the City’s storm and surface water policies.
2.1.2.1 Rates
The currently established rates for the storm drainage service are provided in the table below, which
lists rates for years 2009 and 2010. Base rates are the monthly charge for service from the storm
drainage utility to recover costs incurred by the utility such as administrative, billing, and collection.
Equivalent service units (ESU) are used as a means for estimating the impervious surfaces estimated
to contribute an amount of runoff to the city’s storm drainage system which is approximately equal
to that which is created by the average single-family residential parcel. “Impervious,” as defined by
the City (see ACC Chapter 13.41), is a hard surface area that prevents the entry of water into the soil
mantle. Common impervious surfaces include, but are not limited to, rooftops, walkways, patios,
concrete, or asphalt paving. Open, uncovered, retention/detention facilities shall not be considered
as impervious surfaces for the purpose of ESU calculations. One ESU is equal to 2,600 square feet
of impervious surface area or any portion thereof.
Table 2-1 provides the current monthly charges, base rates, and ESU monthly rates for
classifications used by the utility.
Table 2-1. 2009 and 2010 Utility Rates for Storm Drainage Service
Effective as of January 1, 2009 Effective as of January 1, 2010
Single-family parcel types Monthly charge Monthly charge
Single-family residential parcelsa $13.38 $14.18
Two-family residential parcelsb 13.38 14.18
Non-single-family parcels
Base rate per
month
ESU rate per
month (ESU)
Base rate per
month
ESU rate per
month (ESU)
Non-single-family (NSF)c $8.32 $10.65 $8.82 $11.29
NSF with detentiond 8.32 8.55 8.82 9.07
NSF with retentione 8.32 5.30 8.82 5.61
NSF with water quality treatmentf 8.32 6.40 8.82 6.78
NSF with detention and water quality treatment 8.32 4.83 8.82 5.12
NSF with retention and water quality treatment 8.32 3.03 8.82 3.21
a. Any parcel of land having on it a single detached dwelling unit which is designed for occupancy by one family or a similar group of people.
b. A building designed exclusively for occupancy by two families living independently of each other, and containing two dwelling units.
c. Any parcel of developed land other than single-family or two-family (duplex) residential.
d. “Detention” is the temporary storage of storm and surface water runoff with provisions for the controlled off-site surface release of the stored water.
e. “Retention” means the storage of storm and surface water runoff with no provisions for off-site surface release of the stored water other than by evaporation
and infiltration.
f. “Water quality treatment” means an engineered and approved facility to remove contaminants in the existing flow regime of stormwater generated from a
developed parcel pursuant to applicable design standards in place at the time of approval.
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Storm drainage utility rates are billed on a monthly basis. Storm drainage charges start from the day
water meter servicing the property is installed by the City. In cases where the property does not
receive water service from the City, storm drainage charges start from the day that the storm
drainage permit is finalized by the City. Payments received for utility bills are applied to expenses in
the following order of priority: late charges, additional fees, storm, garbage, sewer, and water.
Payment for storm drainage service charges is due and payable to the finance department office 15
days after the billing date appearing on the bill. Utility charges are constituted as a lien, and thus can
be applied to a lien upon the property from which such charges are due, superior to all other liens
and encumbrances whatsoever, except for general taxed and local special assessments.
2.1.2.2 Fees
The City has permit fees and connection fees. Permit fees are applied to cover the planning,
checking, inspection, record drawings, and processing of permit information for new connections to
the public storm drainage system. A repair permit fee is applied to cover inspection and processing
of permit information for repairs conducted to private storm drainage systems.
Connection fees are charges in lieu of assessments. Such fees can be applied to properties that have
not previously paid for storm drainage systems abutting their property, but intend to connect to it.
The City determines the charge in lieu of assessment amount based on the property’s proportional
share of the calculated cost for the storm drainage system. Properties connected to storm drainage
systems constructed prior to 1987 are not required to pay a charge in lieu of assessment, unless
required to do so under an existing agreement. The City rarely charges connection fees for
stormwater, but rather a system development charge (SDC) at the time a new customer joins into
the system (see the following section).
2.1.2.3 System Development Charge
A utility SDC is a charge imposed on new customers, or existing customers revising use of their
property, in recognition of the previous investment of the city and its customers in the utility
systems. The purpose of an SDC is to recover a fair share of the costs of providing existing utility
system infrastructure to serve new customers or revised uses of existing customers. As with
stormwater utility rates, SDCs are based on the relative amount of impervious surface added to the
system. In 2009, SDCs were estimated to be $1,162 per ESU (see Section 2.1.2.1 for a definition of
ESU).
2.2 Development Code and Design Standards Update
Beginning in late 2008 and continuing to the present, the City has conducted a substantive update to
its development regulations and design standards contained within the ACC, including the City’s
Zoning Code, Subdivision Code, and Engineering Design Standards. The update is intended to
improve the readability of the development regulations, address problems with the content, ensure
consistency with other state land use and environmental regulations, and address City Council policy
and process expectations as a result of the Council’s self-initiated removal from quasi-judicial
decision-making for land use applications and decisions. It is expected that this update effort will be
completed in 2010.
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Development regulations related to stormwater and drainage design standards are also being revised
as part of the overall code update. The City will develop new stormwater design standards based on
current policies and level of service goals, which at the same time will bring the City into compliance
with current regulations. One of the major outcomes is that the City will adopt a new stormwater
manual that is equivalent to the minimum requirements set forth by the Washington State
Department of Ecology (Ecology). Adopting a new stormwater manual is one of the major steps for
compliance with the NPDES Permit (see the following section for an overview of the NPDES
Permit program and Chapter 7 for specific steps toward NPDES compliance).
2.3 Regulatory Considerations
Numerous federal, state, and local regulations can affect stormwater management in the city. Table
2-2 summarizes a number of the applicable regulations.
Table 2-2. Federal, State, and City Regulations and Programs
Relevant to the Auburn Stormwater Utility
Title
Regulation
or program Application to the City
Federal
Clean Water Act (CWA): §402
NPDES Permit
Regulation The Phase II NPDES Permit contains a number of requirements that affect stormwater
management in the city. See Section 2.3.2 below.
CWA: §303(d) total maximum daily
load (TMDL) listing
Regulation TMDLs could lead to more stringent stormwater quality controls in future Phase II
NPDES Permits.
CWA: §404 permit requirements Regulation Some stormwater capital improvement projects can affect wetlands or other “waters of
the U.S.” §404 permitting and mitigation can increase CIP costs and schedules.
Endangered Species Act (ESA) Regulation Stormwater capital improvement projects that involves federal permitting or funding
could require consultation with federal agencies under §7 of the ESA. ESA consultation
could increase project timelines and costs.
National Flood Insurance Program Program Drainage Plan could affect the city’s rating under the Community Rating System, which
affects flood insurance rates.
Governmental Accounting Standards
Board (GASB) Statement 34
Program Requires accurate inventory of City’s stormwater infrastructure. See Section 2.3.3
below.
State
State Environmental Policy Act
(SEPA)
Regulation Each capital improvement project would require SEPA review prior to implementation;
unless that project qualifies as exempt.
Water quality standards Regulation The Phase II NPDES Permit does not authorize discharges that would violate State
water quality standards. The State may establish TMDLs for water bodies that violate
the standards. As noted above, the TMDLs can become NPDES Permit requirements.
§401 water quality certification Regulation Individual projects that require §404 or other federal permits would also require a 401
certification from Ecology. A 401 certification could include site-specific mitigation
measures, which could affect capital improvement project design and cost estimates.
Puget Sound Water Quality
Management Plan
Program Drainage Plan recommendations should be consistent with the Puget Sound Water
Quality Management Plan.
Puget Sound Partnership Program In 2007, the Washington State Legislature created a new State agency for the purpose
of developing and overseeing the implementation of an “Action Agenda” to restore Puget
Sound by 2020. The Partnership’s “Action Agenda” identified stormwater runoff as a key
cause of Puget Sound’s water quality problems.
GMA and City Comprehensive Plan Regulation This Drainage Plan is required by the GMA. GMA is discussed in Section 2.3.1 below.
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Table 2-2. Federal, State, and City Regulations and Programs
Relevant to the Auburn Stormwater Utility
Title
Regulation
or program Application to the City
State Hydraulic Code Regulation Capital improvement projects that involve work in waters of the state would require a
hydraulic project approval (HPA) permit. HPA permitting and mitigation measures could
affect CIP costs.
Archaeological and cultural
coordination
Regulation If any capital improvement projects are planned for areas with known or suspected
archaeological sites. The City will need to coordinate with the Department of
Archaeology and Historic Preservation, local Indian tribes, and King County Historic
Preservation.
City
Environmental review Regulation Each capital improvement project would be subject to environmental review prior to
permitting and construction as prescribed in ACC 16.06, This chapter of the ACC was
adopted under the authority of SEPA.
Critical areas ordinance Regulation The Drainage Plan should avoid capital improvement projects in critical areas (e.g.,
wetlands, groundwater protection zones, or wildlife habitat). If a capital improvement
project must be sited in a critical area, the cost estimate should include costs for
mitigation and permitting as prescribed in ACC 16.10.
Development regulations Regulation The City’s development regulations must be consistent with Phase II NPDES Permit
requirements.
Shoreline Master Program (SMP) Regulation Future projects should be located and designed to be consistent with the City shoreline
regulations (ACC 16.08). Projects within designated shorelines could require permits
and mitigation, which could affect project costs and schedules.
Most of the regulations listed in Table 2-2 primarily affect the implementation of specific measures
recommended in the Drainage Plan. For example, CIP that could affect wetlands would need to
comply with City critical areas regulations and possibly federal CWA Section 404 regulations.
However, three of the regulations listed in Table 2-2 —the GMA, Ecology’s Phase II NPDES
Stormwater Permit, and federal GASB Statement 34—directly affect the LOS for this Drainage
Plan. These regulations are discussed greater detail in Sections 2.3.1 through 2.3.3 below.
2.3.1 Growth Management Act
The Washington State Legislature enacted the GMA in 1990 in response to rapid population growth
and concerns with suburban sprawl, environmental protection, quality of life, and related issues. The
GMA is codified primarily in RCW Chapter 36.70A.
The GMA provides a framework for regional coordination, and counties planning under the GMA
are required to adopt countywide planning policies to guide plan adoption within the county and to
establish urban growth areas (UGAs). Local comprehensive plans must include the following
elements: land use, housing, capital facilities, utilities, transportation, economic development, parks
and recreation, and for counties, a rural element. This Drainage Plan serves as the capital facilities
element for City-owned storm drainage assets.
RCW 36.70A.070 requires capital facilities elements to include:
An inventory of existing capital facilities owned by public entities, showing the locations and
capacities of the capital facilities.
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A forecast of the future needs for such capital facilities.
The proposed locations and capacities of expanded or new capital facilities.
At least a 6-year plan that will finance such capital facilities within projected funding capacities
and clearly identifies sources of public money for such purposes.
A requirement to reassess the land use element if probable funding falls short of meeting existing
needs and to ensure that the land use element, capital facilities plan element, and financing plan
within the capital facilities plan element are coordinated and consistent. Park and recreation
facilities shall be included in the capital facilities plan element.
To facilitate meeting the above requirements, WAC 365-195-315 recommends:
The selection of LOS or planning assumptions for the various facilities to apply during the
planning period (20 years or more) and which reflect community goals.
A forecast of the future needs for such capital facilities based on the LOS or planning
assumptions selected and consistent with the growth, densities, and distribution of growth
anticipated in the land use element.
The creation of a 6-year capital facilities plan for financing capital facilities needed within that
time frame. Projected funding capacities are to be evaluated, followed by the identification of
sources of public or private funds for which there is reasonable assurance of availability. The
6-year plan should be updated at least biennially so that financial planning remains sufficiently
ahead of the present for concurrency to be evaluated.
A provision should be made to reassess the land use element and other elements of the plan
periodically in light of the evolving capital facilities plan. If the probable funding for capital
facilities at any time is insufficient to meet existing needs, the land use element must be
reassessed. At the same time funding possibilities and LOS might also be reassessed. The 6-year
plan should require that as a result of such reassessment, appropriate action must be taken to
ensure the internal consistency of the land use and capital facilities portions of the plan. The plan
should set forth how, if at all, pending applications for development will be affected while such a
reassessment is being undertaken.
2.3.2 Phase II Municipal Stormwater Permit
The NPDES Permit program is a requirement of the federal CWA, which is intended to protect and
restore waters for “fishable, swimmable” uses. The federal Environmental Protection Agency (EPA)
has delegated Permit authority to state environmental agencies, and these agencies can set Permit
conditions in accordance with and in addition to the minimum federal requirements. In Washington,
Ecology is the NPDES-delegated Permit authority.
Phase I of the stormwater NPDES regulation applies to cities and counties that operate municipal
separate storm sewer systems (MS4s) and had populations of 100,000 people or more according to
the 1990 census. Phase II of the stormwater NPDES regulation applies to municipalities that
operate MS4s and have populations of fewer than 100,000 people.
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Ecology issued the NPDES Phase II Permit (Permit) in February 2007. The Phase II Permit covers
about 100 municipalities in Washington, including the city of Auburn. The Permit requires the City
to submit a Stormwater Management Program (SWMP) by March 31 of each year, in which the City
reports progress on the implementation of Permit requirements. The Permit also requires submittal
of documentation that describes proposed SWMP activities for the coming year. Implementation of
various Permit conditions is staggered throughout the 5-year Permit term from February 16, 2007,
through February 15, 2012. The Permit will be revised and reissued at the end of this period. The
Phase II Permit and associated requirements are described in detail in the City’s 2008 SWMP
document (Brown and Caldwell consultants, 2008).
The Phase II Permit allows municipalities to discharge stormwater runoff from their municipal
drainage systems into the state’s water bodies (e.g., streams, rivers, lakes, and wetlands) as long as
municipalities implement programs to protect water quality by reducing the discharge of “nonpoint
source” pollutants to the “maximum extent practicable” (MEP) through application of Permit-
specified “best management practices” (BMPs). The BMPs specified in the Permit are collectively
referred to as the SWMP and grouped under the following program components:
Public education and outreach
Public involvement
Illicit discharge detection and elimination (IDDE)
Control of runoff from development, redevelopment, and construction sites
Pollution prevention and municipal operation and maintenance
Monitoring.
The Phase II Permit also requires compliance with established total maximum daily loads (TMDLs)2.
The current Phase II Permit does not contain any TMDL requirements for the City. However,
Ecology has identified several water bodies in the vicinity of Auburn that do not appear to meet the
water quality standards. If Ecology establishes TMDLs for one or more of these water bodies prior
to 2012, the next version of the Phase II Permit may contain additional requirements specified in the
TMDL.
A copy of the Western Washington Phase II Municipal Stormwater Permit is included in
Appendix A.
2.3.3 Governmental Accounting Standards Board
Financial reporting by public utilities must adhere to requirements set by the GASB, the agency
responsible for developing standards of state and local governmental accounting and financial
reporting. Most prominent is GASB Statement 34, “Basic Financial Statements—and Management’s
Discussion and Analysis—for State and Local Governments,” which was issued in June 1999. The
2 A TMDL is a calculated maximum pollutant loading a water body can receive while still meeting water quality
standards. Once a TMDL is established the State determines how much each source must reduce its discharges of the
pollutant in order to bring the water body back into compliance with the water quality standards. The federal CWA
requires that TMDLs be established for all water bodies that do not meet water quality standards, and that TMDL
requirements be included in the NPDES permits for dischargers into the affected water bodies.
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main objective of Statement 34’s requirements is to have financial reports that are more
comprehensive and are easier to understand by the public. Statement 34 consists of several
components which can be seen in full in paragraphs 3–166 of the GASB publications. In summary,
Statement 34 requires that the basic financial statements and required supplementary information
(RSI) for general purpose governments should consist of the following:
Management’s discussion and analysis. In sum, this requirement states that prior to the basic
financial statements, a discussion providing an analytical overview of the government’s financial
activities is necessary.
Basic financial statements, which should include:
· Government-wide financial statements which include information on net assets (e.g., storm
drainage infrastructure) and a statement of activities.
· Fund financial statements which focus on information about the government’s major
governmental and enterprise funds (e.g., the City’s storm drainage utility), including its
blended component units.
· Notes to the financial statements that will enable users to understand the basic financial
statements.
Required supplementary information. Budgetary comparison schedules should be presented
as RSI along with other types of data as required by previous GASB pronouncements.
Consequently, the City needs an accurate inventory of its stormwater infrastructure in order to
comply with the GASB 34 requirements.
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CITY OF AUBURN COMPREHENSIVE
STORMWATER DRAINAGE PLAN
3. UTILITY POLICIES AND LEVEL OF SERVICE GOALS
This chapter describes a set of guiding policies for the City’s storm drainage utility and LOS goals
for complying with these policies. These policies and LOS goals are consistent with those described
in the City’s 2008 Comprehensive Plan (Comp Plan).
Level of service is generally defined as a community’s specific goals or objectives for capital facility
infrastructure development, operation, maintenance, and other key elements of utility management.
These goals provide a framework for the utility to assess its staffing levels, prioritize its resources,
justify its rate structure, and document its successes. LOS goals should relate directly to City policies
and include clear criteria to use in evaluating how well LOS goals are being met.
The City has developed policies and LOS goals for the following elements of storm drainage utility
operation:
Protection of public safety and property
Reliability of the storm drainage infrastructure
The role of the utility in protecting the environment
Financial performance of the utility
Customer satisfaction
Health and safety.
The remainder of this section introduces the concept of LOS goals in storm drainage utilities and
proposes specific LOS goals for the City.
3.1 Level of Service Goals within Storm Drainage Utilities
LOS goals defined by a storm drainage utility can relate to quality, quantity, reliability,
responsiveness, safety, environmental acceptability, and cost of delivering service. To serve as
effective management tools, LOS goals should be measurable. For example, a measurable “public
health and safety” LOS goal for drainage would be to ensure that flooding beyond a certain depth
does not recur on critical traffic routes more often than a target frequency (e.g., flooding that affects
private property limited to an average of once per 50 years). An example of an “environmental
protection” LOS goal would be compliance with all required elements of the City’s Phase II NPDES
Stormwater Permit. In the latter example, the NPDES Permit has embedded specific metrics for
evaluating compliance (e.g., implementation of 95 percent of Permit-required stormwater facility
inspections). In this instance, the Permit is mandating that the City implement measurable LOS
criteria.
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By documenting LOS, a storm drainage utility provides a transparent set of metrics to elected
officials and the community, and can begin to communicate with stakeholders about rate
implications associated with increasing or decreasing service. Higher LOS standards result in greater
costs to taxpayers, rate payers, and new development; lower LOS standards may result in lower rates
but unacceptable public safety, environmental stewardship or regulatory compliance. LOS goals may
be flexible; communities should be willing to periodically revisit LOS goals to make sure that they
are still appropriate.
3.2 Levels of Service
This section reviews elements of the City’s current Comp Plan that apply to storm drainage utility.
This section also discusses a set of LOS goals to guide this storm drainage comprehensive planning
effort and future utility activities.
3.2.1 Incorporation of Existing Comp Plan Storm Drainage Policies
The City’s current Comp Plan contains numerous goals that relate to the operation and management
of storm drainage assets. The items below are City policies that have been used in developing
specific LOS for this Drainage Plan. These policies are taken verbatim from the 2008 Comp Plan.
The items named with “CF” and “EN” prefixes appear in the Capital Facilities and Environment
chapters, respectively.
CF-40 The City should continue to fund and provide storm drainage services through the existing storm drainage
utility. The City's storm drainage utility should be responsible for implementation, maintenance and
operation of the City's comprehensive drainage system and seek out sources of stormwater pollution and
correct them.
CF-41 Appropriate rates and system development charges shall be assessed to fund the ongoing maintenance,
operation, and capital expenditures of the utility, in accordance with the Comprehensive Drainage Plan.
Periodic cost of service studies shall be completed to reassess the monthly service and system development
charges.
CF-45 The City shall promote policies that seek to maintain the existing conveyance capacity of natural
drainage courses.
CF-48 In selecting the preferred Comprehensive Drainage Plan sub-basin alternative for implementation by the
City’s storm drainage utility, the City shall consider the following factors:
1. The most efficient and cost effective means of serving a subbasin or combination of subbasins.
2. The ability of the alternative to implement source control best management practices and to avoid or
mitigate environmental impacts, such as impacts to existing wetlands, and the degree to which the
alternative promotes water quality treatment, and protects aquatic and riparian habitat.
3. Consistency with Comprehensive Drainage Plan policies and recommendations and compatibility
with stormwater improvement policies and recommendations presented in other regional stormwater
plans.
4. Restrictions or constraints associated with receiving waters.
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5. The ability to develop a multi-use facility.
6. The degree to which the alternative preserves, increases, and is compatible with existing open space.
7. Consistency with existing and future planned development.
8. The advantages and disadvantages of storage versus conveyance while ensuring adequate treatment for
water quality treatment.
9. The degree to which the alternative preserves and enhances existing native vegetation and existing
drainage courses.
10. The alternative’s ability to reduce flood hazard impacts resulting from the 25-year design storm
event.
EN-3 The City shall seek to minimize degradation to surface water quality and aquatic habitat of creeks,
streams, rivers, ponds, lakes and other water bodies; to preserve and enhance the suitability of such water
bodies for contact recreation and fishing and to preserve and enhance the aesthetic quality of such waters
by requiring the use of current Best Management Practices for control of stormwater and nonpoint runoff.
EN-12 The City shall continue to work with adjacent jurisdictions to enhance and protect water quality in the
region through coordinated and consistent programs and regulations.
EN-15 The City recognizes that new development can have impacts including, but not limited to, flooding,
erosion and decreased water quality on downstream communities and natural drainage courses. The City
shall continue to actively participate in developing and implementing regional water quality planning and
flood hazard reduction efforts within the Green River, Mill Creek and White River drainage basins.
The findings and recommendations of these regional efforts, including, but not limited to, the “Draft”
Special Area Management Plan (SAMP) for the Mill Creek Basin, the “Draft” Mill Creek Flood
Control Plan, the Green River Basin Program Interlocal Agreement, and the Mill Creek Water
Quality Management Plan, shall be considered by the City as City programs and plans are developed
and updated.
EN-17 The City recognizes that stormwater treatment facilities do not function efficiently unless maintained. The
City shall strive to ensure that public and private stormwater collection, detention, and treatment systems
are properly maintained and functioning as designed.
EN-17A Encourage the use of low impact development techniques in public and private development proposals in
order to minimize impervious surfaces and improve water quality.
EN-57 The City shall seek to protect human health and safety and to minimize damage to the property of area
inhabitants by minimizing the potential for and extent of flooding or inundation.
3.2.2 Levels of Service
The drainage Policies and LOS (see Table 3-1) are organized by category and encompass and
elaborate on the drainage policies articulated in the City’s Comp Plan. Specific service provision
policies are presented by category, with LOS for evaluating service delivery.
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Table 3-1. LOS Goals
Item Policy description 2009 Drainage Plan LOS goal
Policy category: protection of public safety and property
1 The City shall seek to manage stormwater runoff
within the public right-of-way (ROW) to allow access
to and functionality of critical services such as
hospitals, fire and police stations, Emergency
Operations Center, maintenance and operations, and
city hall. See policy EN-57.
Surface water flooding will disrupt the function of critical facilities (i.e., with
floodwaters reaching the building structure, damaging the structure, and
permitting no ingress/egress) with an annual chance of occurrence of no
greater than 1 percent (i.e., an average recurrence interval of 100 years).
2 The City shall seek to manage stormwater runoff
within the public ROW to preserve mobility on major
transportation routes (i.e., arterial roads) and
residential roads. See policy EN-57.
Flooding disruption that inundates city roadways to an impassable level with
an annual chance of occurrence of no greater than 4 percent (i.e., an average
recurrence interval of 25 years).
3 The City shall seek to manage stormwater runoff from
the public ROW to protect real property structures
(e.g., residences and businesses). See policy EN-57.
Flooding (surface water from ROW runoff entering premises and damaging
building structures) with an annual chance of occurrence of no greater than 2
percent (i.e., an average recurrence interval of 50 years).
4 The City shall seek to prevent erosion and landslides
related to construction, operation, and maintenance
of the publicly owned drainage system. See polices
CF-48 and EN-3.
No erosion or landslides resulting from public drainage infrastructure
construction, operation, or maintenance. No direct stormwater discharge will
be permitted on steep slopes.
5 The City shall seek to maintain storm drainage
infrastructure to ensure proper function of drainage
facilities. The City shall seek to seasonally maintain
storm drain inlets, conveyance, and outfalls to
preserve design conveyance capacity. See policies
CF-40 and EN-17.
The City will refine its maintenance practices and reallocate staff as needed to
address seasonal concerns, with an emphasis on maintaining facilities that
have a high “consequence of failure.” An example would be focusing extra
M&O staff on catch basin inlet cleaning during autumn when leaves are
falling. Activities will be documented within the City's CartêGraph
computerized maintenance management system (CMMS).
Policy category: reliability of the storm drainage infrastructure
6 The City shall seek to maintain an asset criticality
database to be used in prioritizing asset maintenance
and R&R. See policies CF-40 and EN-17.
The existing criticality database (developed for this Drainage Plan) will be
refined to include more asset information, such as pipe material, diameter,
age, consequence of failure, etc. The criticality database will be validated
using the results of previous and ongoing M&O inspections. Activities will be
documented within the City's CartêGraph CMMS.
7 The City shall seek to perform condition assessments
of critical assets. See policies CF-40 and EN-17.
The City will develop and implement a condition assessment schedule for
critical assets as identified through criticality analyses of stormwater
infrastructure assets. Criticality is based on the risk and consequences of
failure. Criticality data will be stored in a criticality database, and condition
assessment activities will be documented in the CMMS.
8 The City shall seek to repair or replace system assets
before they exceed their economic lives. See policies
CF-40 and EN-17.
The number of high-criticality pipe segments beyond their economic lives will
be determined. After the criticality database inventory is complete, the City’s
goal will be to limit the number of pipe segments beyond their economic lives,
including setting specific numeric goals for replacement of those segments.
9 The City shall seek to conduct maintenance activities
in accordance with a schedule developed to comply
with Ecology requirements and asset criticality. See
policies CF-40, EN-12 and EN-17.
No deferred maintenance on all critical or Ecology-required assets. The City
will prioritize its inspection activities based on the combined “risk of failure”
and “consequence of failure” computed by the criticality database and meet
current NPDES inspection schedule (e.g., inspecting outfalls). The experience
of M&O staff should be incorporated into the criticality database (see item 6
above). Inspection activities will be documented in the CMMS.
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Table 3-1. LOS Goals
Item Policy description 2009 Drainage Plan LOS goal
Policy category: protection of the environment
10 The City shall seek to provide pump redundancy and
backup power generators or dual power feeds at City-
owned and -operated drainage pump stations. See
policy EN-17.
Pump stations will be designed with two or more pumps to ensure proper
function during maintenance. Backup and/or dual-feed power supplies will be
installed as needed.
11 The City shall seek to comply with all federal, state,
and local regulations in operation and maintenance of
the City’s storm drainage infrastructure. See policy
EN-12.
Meet all specific targets. Examples include complying with NPDES Phase II
inspection cycle, performing all necessary ESA consultations, etc.
12 The City shall protect and preserve existing native
vegetation and drainage courses while maintaining
their conveyance capacity. See policy CF-45.
No net loss of native vegetation (in terms of area) or natural drainage systems
(in terms of stream length) to maintain existing habitat along drainage ways.
This does not apply to constructed or maintained facilities.
13 The City shall seek to reduce runoff volumes and
pollutant loads associated with new development.
See policy EN-15.
The City will comply with the elements of the NPDES Phase II Stormwater
Permit and implement an Ecology-equivalent stormwater manual for new
development. Identify appropriate areas and provide guidance for the
implementation of low impact development (LID) drainage management
measures by new development and redevelopment (including City-owned
properties).
14 The City shall seek to evaluate drainage utility
activities to emphasize sustainability. See policy CF-
40.
City staff will identify specific areas to measure sustainability by examining
how storm drainage utility operations affect energy resources and natural
resources. City staff will benchmark practices and log changes over the next
planning period.
15 The City shall continue to participate in regional storm
drainage, water resources, and water quality planning
efforts. See policies CF-48 and EN-12.
The City will continue to actively participate in developing and implementing
regional water quality planning and flood hazard reduction efforts within the
Green River, Mill Creek, and White River drainage basins.
Policy category: storm drainage utility financial performance
16 The City shall continue to fund and provide storm
drainage services through the existing storm drainage
utility. See policy CF-40.
The City's storm drainage utility should be responsible for implementation,
maintenance, and operation of the City's drainage system. Goal of 100% of
cost of drainage service delivery recovered via storm drainage utility fees.
Seek opportunities to provide public drainage benefits through grants funding
and/or development partnerships where applicable.
17 The City shall assess appropriate rates and SDCs to
fund the ongoing maintenance, operation, and capital
expenditures of the utility, in accordance with the
Drainage Plan. See policy CF-41.
Periodic cost of service studies shall be completed to reassess the monthly
service fees and SDCs. Updates to coincide with 6-year CIP updates.
18 The City shall seek to track the cost of claims as a
metric. See policy CF-41.
City staff will summarize the annual costs of claims for the recent past to
establish a baseline measurement of existing practices. If the current costs
are deemed excessive, City staff will define methods to reduce the risk of
claims and measure its progress at reducing the overall cost of claims.
19 The City shall seek to track elements of CIP
implementation: (1) individual schedule, (2) project
budget accuracy, and (3) overall performance in
implementing CIP. See policies CF-40 and CF-48.
City staff will summarize current methods for CIP implementation to create a
baseline (e.g., schedule and costs) against which future improvements can be
evaluated.
Policy category: customer satisfaction
20 The City shall seek to evaluate and strive to maintain
customer satisfaction with drainage utility service
delivery. See policy CF-40.
To effectively measure the public perception of utility performance, City staff
will conduct the following: (1) summarize annual customer complaint reports,
(2) communicate proactively with community and stakeholders regarding
drainage infrastructure improvements, and (3) comply with Stormwater
NPDES Phase II Permit requirements for public education and outreach.
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Table 3-1. LOS Goals
Item Policy description 2009 Drainage Plan LOS goal
21 The City shall seek to build, operate, and maintain
drainage utility infrastructure within an overarching
goal of protecting employee safety. See policy CF-40.
City staff will track health and safety incidents to create a baseline against
which to evaluate future improvements.
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CITY OF AUBURN COMPREHENSIVE
STORMWATER DRAINAGE PLAN
4. DRAINAGE SYSTEM
Chapter 3 lays out clear LOS goals for the stormwater utility. The next step toward developing a
future work plan is to collect and organize information describing the current conditions of the
stormwater drainage system. This information provides the basis for investigations (Chapter 5)
designed to evaluate the stormwater utility performance relative to the LOS goals. This chapter
provides an overview of the City’s drainage system including both natural (Section 4.1) and
constructed (Section 4.2) drainage elements.
Figures presented in this chapter consist of several maps of the stormwater utility service, drainage
and surrounding areas. These figures are presented at the end of the chapter.
4.1 Natural Drainage
The city of Auburn encompasses approximately 30 square miles; the central portion of the city lies
along the bottom of the valley, while the outer edges of the city extend into the surrounding hills
(see Figure 4-1). In general, stormwater runoff from the city flows to one of three major receiving
waters: Green River, White River, and Mill Creek. Other notable water features in the Auburn area
include the following:
Big Soos Creek, which drains southeast into the Green River
Soosette Creek (also known as Little Soos Creek), which drains south into Big Soos Creek
Mullen Slough, which drains along the northwest side of Mill Creek toward the Green River
Bowman Creek, which drains north into the White River
Olson Creek, which drains west into the Green River
Lake Tapps, which is located just south of the city
White Lake, which is located southeast of R Street SE and State Route (SR) 18.
Coal Creek Springs, which drains north to the White River.
The city contains nearly 400 acres of wetlands; approximately 80 acres are classified as
forested/shrub wetland and the remainder are classified as freshwater emergent wetland. The
freshwater emergent is located primarily on the western part of the city along Mill Creek. The
forest/shrub wetland lies mainly in the eastern part of the city and along the White and Green
Rivers.
The following sections provide additional information on each of the three major receiving waters.
4.1.1 Green River
The Green River flows over 93 miles beginning on the west slope of the Cascade Mountains and
ending in the Duwamish Waterway, meandering through the northeast portion of Auburn along the
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east valley wall. Throughout the last century, the Green River was altered for the purpose of flood
control, including the construction of levees and bank revetments, and the diversion of the White
River in the early 1900s. In 1962, Howard A. Hanson Dam was built on the Green River to control
flooding in the valley.
In 1985, the city of Auburn entered into the Green River Management Agreement along with King
County and the cities of Kent, Renton, and Tukwila. The purpose of the agreement was to operate
existing pumping facilities to drain interior floodwaters in a manner that limits the risk of levee
overtopping and possible failure of the Green River levee system. In 1986, the participating agencies
developed the Green River Pump Operations Procedure Plan to guide pump operations and control
the cumulative effect of surface drainage into the Green River. This plan describes operation and
maintenance procedures for the City’s pumps, levees, and drainage outfalls on the Green River (see
Appendix B).
4.1.2 White River
The White River originates on the slopes of Mount Rainier and flows generally northward and
westward into the Puget Sound lowlands. Near Auburn, the White River flows north and then west
through the southern portions of the city before it curves southward toward the Puyallup River. The
White River is a very dynamic, sediment-laden river, which has led to changing channel morphology.
Prior to 1900, the White River flowed into the Green-Duwamish River; however, floodwaters from
the White River drained to both the Green-Duwamish River and the Puyallup River. A flood in
1906 caused the White River to shift and flow into the old Stuck River channel, which leads to the
Puyallup River. In 1907, a diversion wall located within Game Farm Park was constructed to
permanently direct the White River flow into the Puyallup River (USACE, October 2009).
The shifting of floodwaters from the White River caused inter-jurisdictional conflicts between King
and Pierce Counties. After attempts from the two counties to control flooding along the White
River met with limited success, the U.S. Army Corps of Engineers (USACE) was engaged for help.
In 1948, the USACE finished construction of Mud Mountain Dam to control floods on the White
River.
At the time Mud Mountain Dam was finished, White River channel capacity in the area of Auburn
was estimated to be 20,000 cfs. Since then, vegetation encroachment and sediment accumulation
have reduced channel capacity to approximately 9,000 cfs (USACE, October 2009). Reduced
channel capacity causes higher river levels during large storm events, which can impact the City’s
gravity drainage outfalls along the White River.
4.1.3 Mill Creek
Mill Creek flows out of the hills on the west side of the valley near SR 18, and then turns northward
along the western portion of the city, running adjacent to SR 167. North of the city boundary, Mill
Creek discharges into the Green River. Historically, Mill Creek served as vital habitat for migrating
salmon and provided ideal conditions for rearing and storm refuge. However, increasing
development has altered the natural flow pattern of Mill Creek, including the installation of
diversions and culverts, degradation of water quality, and aggradation from increased stormwater
inflows with high sediment loads. In many areas the stream is straight, shallow, and exhibits a lack of
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quality riparian habitat for ESA-listed species such as Chinook salmon and bull trout (USACE,
2009).
Aggradation along Mill Creek has also contributed to flooding and drainage problems. The City’s
drainage outfalls on Mill Creek can become submerged, thereby reducing the hydraulic capacity of
the system.
Several projects are underway to enhance Mill Creek habitat and improve water quality. The USACE
and King Conservation District have initiated a restoration project for the reach of Mill Creek
extending from Main Street on the west side of SR 167 to the crossing of Mill Creek with SR 167.
The city of Auburn and the U.S. Fish and Wildlife Service are partnering on a concurrent project to
replace the culvert at 15th Street NW, improving fish passage and stream flow conveyance. In
addition to riparian enhancement, these projects will remove flow constrictions, improve flow
conveyance, and reduce flood elevations along Mill Creek.
4.1.4 Drainage Areas
The city’s drainage can be described by dividing the city into the following general sub-areas1:
Lea Hill lies northeast of the Green River. Most of the Lea Hill area drains west into the Green
River. However, the eastern edge drains south and east out of the city into Soosette Creek and
Big Soos Creek.
West Hill lies west of Mill Creek. The West Hill area drains into several small tributaries to Mill
Creek. The northern portion of West Hill drains to the northeast into steep ravines that discharge
to Mullen Slough and other wetland areas on the valley floor.
The Southern portion of the city drains to the White River. The area west of Bowman Creek
consists largely of the Lakeland Hills developments, which drain to the White River to the west
and north, Bowman Creek to the east, and a small portion which drains south toward Lake
Tapps. The area east of Bowman Creek consists of rural residential development; this area drains
to Bowman Creek on the southwest and the White River on the northeast side.
The Southeast portion of the city lies along a narrow plateau between the Green and White
Rivers. Runoff from this area drains to the Green River along the north side and the White River
along the south side.
The Central and most developed areas of the city lie along the valley floor, which is relatively flat
and drains to all three main receiving waters. The southern portion of the valley from about 27th
Street SE southward plus the Boeing property drains to the White River. Areas north of 27th
Street SE are generally split between Mill Creek and the Green River. The topography in this area
is so flat that roadways and storm drainage infrastructure largely determine the receiving water to
which runoff is diverted.
1 For the purposes of this Drainage Plan, sub-areas are generally defined areas within the City that do not have clearly
defined boundaries such as those of a basin or sub-basin, which can be delineated based on topographic information.
Sub-areas are defined for the purpose of general discussion and are not used for specific evaluations or analyses.
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The above-described areas can be divided into smaller drainage sub-basins. The 1990 Comprehensive
Drainage Plan delineated 16 drainage sub-basins based on independent outfalls to receiving waters
(CH2M Hill and Kato & Warren, 1990). The total drainage area of these 16 sub-basins covered
approximately 8.3 square miles, focusing on the central corridor and most developed areas of the city.
The 2002 Comprehensive Drainage Plan (Tetra Tech, 2002) focused on roughly the same area. The
sub-basins were refined somewhat to create 19 sub-basins covering an area of approximately
9.15 square miles. Although the 2002 study did not address drainage issues outside of these 19 sub-
basins, additional sub-basins were delineated such that the entire stormwater drainage utility was
covered, resulting in a total of 61 drainage sub-basins covering approximately 34 square miles (see
Figure 4-2). Each sub-basin was identified by a series of one, two, or three letters. The 61 sub-basins
from the 2002 Drainage Plan were used as the organizational basis for this Drainage Plan because
they cover all drainage areas for the utility.
4.1.5 Climate and Precipitation
Auburn’s climate is typical of that in the Puget Sound lowlands of Western Washington, where the
summers are cool and comparatively dry, while the winters are mild, wet, and cloudy (WRCC,
2009a). Mean annual precipitation in the Puget Sound lowlands varies from 32 inches (north of
Seattle) to approximately 45 inches (near Centralia, Washington).
The precipitation gauge at Auburn city hall has been recording data since 1995. The mean annual
precipitation recorded at that gauge from 1995 to 2008 was approximately 32 inches. This is slightly
less than the mean annual precipitation recorded at the two nearest long-term gauges:
Seattle-Tacoma Airport, which is part of the National Oceanic and Atmospheric Administration
(NOAA) Cooperative Network (Station No. 457473), has a mean annual precipitation of
approximately 38 inches based on 60 years of recorded data (WRCC, 2009b). The Seattle-Tacoma
Airport gauge is located approximately 8 miles northwest of Auburn.
Kent, Washington (NOAA Co-op Station No. 454169) has a mean annual precipitation of
approximately 38 inches based on 98 years of recorded data (WRCC, 2009c). The Kent,
Washington, gauge is located approximately 7 miles north of Auburn.
Precipitation-frequency data for Washington are compiled in Volume 9 of NOAA Atlas 2 (Miller,
Frederick and Tracey, 1973); precipitation-frequency estimates for Auburn, Washington, are listed in
Table 4-1.
Table 4-1. Precipitation Frequency Data for Auburn, Washington, from
NOAA Atlas 2
Frequency, duration Precipitation (inches)
2-year, 6-hour 0.95
2-year, 24-hour 1.75
100-year, 6-hour 1.90
100-year, 24-hour 3.80
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4.1.6 Geology and Groundwater
Topography and geology in the Auburn region has been largely influenced by millions of years of
advancing and retreating glaciers; most recently with the Vashon glaciation occurring approximately
12,000–18,000 years ago (Booth, 1991). Following the retreat of the glacier, interglacial processes
such as landslides, mudflows, erosion, and alluvial deposition have continued to shape the region. In
general, the upland hills around the city’s periphery comprise glacial and interglacial deposits, while
the valley is filled with more recent deposits overlying glacial and older interglacial deposits.
Major geologic units of the White and Green River Valley include undifferentiated glacial and
interglacial deposits, Vashon recessional deltaic deposits, undifferentiated alluvium, Osceola
mudflow, and White River alluvium. The undifferentiated glacial and interglacial deposits form the
lowest layer in the valley consisting of materials deposited during the glacial periods. As the glacier
retreated, meltwater flowed into a water-filled embayment then occupying the present White and
Green River Valley area. This meltwater deposited sand and gravel known as the Vashon recessional
deltaic deposits. After the end of the glacial period the Green River deposited undifferentiated
alluvium in the valley as a result of erosion of upland glacial deposits. Approximately 5,700 years
ago, a massive volcanic mudflow from Mount Rainier, known as the Osceola mudflow, flowed
down into the valley (Troost and Booth, 2008). White River alluvium is the geologic unit nearest the
surface and consists of alluvial deposits from the White and Green Rivers. Bedrock is found
approximately 1,280 feet beneath the valley floor. Surficial geologic mapping of the Auburn region is
shown in Figure 4-3.
In general, groundwater flow systems in the Auburn area are characterized by upland recharge
flowing toward the valley. The two major aquifers in the White and Green River Valley are the
modern alluvium aquifer and a deep deltaic valley aquifer; the latter is used for city water supply. The
modern alluvium aquifer is the shallowest aquifer in the Auburn-Kent Valley, often lying 10 to
15 feet below the ground surface. Groundwater in the deep deltaic valley generally flows in a pattern
parallel to the direction of the Green River in the north and the White River in the south.
4.1.7 Soils and Runoff Potential
Surface soils are classified by the Natural Resource Conservation Service (NRCS) into four
hydrologic soil groups based on the soil’s runoff potential: A, B, C and D. Group A soils generally
have the lowest runoff potential while Group D soils have the highest. Hydrologic soil groups are
defined by NRCS (1986) as follows:
Group A is sand, loamy sand, or sandy loam types of soils. It has low runoff potential and high
infiltration rates even when thoroughly wetted. It consists chiefly of deep, well to excessively
drained sands or gravels and has a high rate of water transmission.
Group B is silt loam or loam. It has a moderate infiltration rate when thoroughly wetted and
consists chiefly of moderately deep to deep, moderately well to well drained soils with moderately
fine to moderately coarse textures.
Group C soils are sandy clay loam. It has low infiltration rates when thoroughly wetted and
consists chiefly of soils with a layer that impedes downward movement of water and soils with
moderately fine to fine structure.
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Group D soils are clay loam, silty clay loam, sandy clay, silty clay, or clay. It has very low
infiltration rates when thoroughly wetted and consists chiefly of clay soils with a high swelling
potential, soils with a permanent high water table, soils with a claypan or clay layer at or near the
surface, and shallow soils over nearly impervious material.
Figure 4-4 shows hydrologic soil group mapping for Auburn and the surrounding areas. The valley
floor is mostly Group D soils, which typically have very low infiltration rates and high runoff
potential. The West Hill, Lea Hill and the Lakeland Hills areas are predominantly Group C soils,
which have low infiltration rates and moderate to high runoff potential. The Southeast area, the
Bowman Creek area, and the valley are located generally between Highway 18 and the White River
have Group A soils, which are characterized by high infiltration rates and low runoff potential.
4.1.8 Land Use and Development
Land use and the intensity of development have considerable effects on the quality and quantity of
stormwater runoff flowing into the drainage system and ultimately discharging to receiving waters.
As the population of the city of Auburn increases, new areas of the city are developed or existing
areas are redeveloped at a higher density. These changes can result in increased stormwater runoff
and greater water quality impacts to water bodies. However, development regulations and drainage
design standards imposed by the City are intended to mitigate these impacts. The following sections
describe expected growth and how development regulations and design standards are being updated
to reduce impacts to stormwater runoff.
4.1.8.1 Recent Growth
Auburn’s population has steadily increased since the 1950s. Auburn’s population increased an
average of 8 percent per year from 1960 to 1980, then slowed to approximately 1.7 percent per year
from 1980 to 1994. Auburn’s population growth rate began to increase in 1998, as the City began
annexing new areas, which precipitated several large housing developments. By 2004, the population
reached approximately 46,000 (Comp Plan, 2008). The population increased dramatically in 2008
due to annexations of in West Hill and Lea Hill. The 2008 Comp Plan cites figures from the
Washington State Office of Financial Management and City records, which indicate that Auburn’s
population in 2008 was approximately 67,000.
4.1.8.2 Future Growth
The City’s goals, objectives, and policies for growth and development are described in detail in the
2008 Comp Plan. These goals, objectives, and policies are applied to different areas of the city
through land use designations (see Figure 4-5). The City also has developed special land use plans
for certain areas of the city where specific land use goals have been identified. An important example
is the City’s downtown area; one of the goals described in the Comp Plan is to encourage
development and redevelopment in the downtown area to serve as an urban center for the
community.
4.1.8.3 Development Regulations and Drainage Design Standards
As described in Section 2.2, the City is currently working on revisions to the stormwater code, which
will include adoption of a new stormwater manual that is equivalent to Ecology’s manual. The
stormwater regulations will contain specific requirements for managing stormwater quality and
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quantity in newly developed and redeveloped areas. For example, the new stormwater manual will
provide guidance for implementing LID measures that are designed to not only improve water
quality, but also to control peak flows and durations of runoff.
The new stormwater regulations and development standards are intended to avoid substantial
increases in stormwater discharges to the existing drainage system through the implementation of
onsite stormwater controls. Ideally, this would keep stormwater conveyance demands at or near
existing levels.
4.1.9 Flood Hazard Mapping
The city of Auburn is a participant in the National Flood Insurance Program (NFIP) administered
through the Federal Emergency Management Agency (FEMA) to enable property owners to
purchase insurance protection from the government against losses from flooding. Participation in
the NFIP is based on an agreement between the City and the federal government, stating that if the
City adopts and enforces a floodplain management ordinance to reduce future flood risks to new
construction in areas designated as Special Flood Hazard Areas (SFHA), the federal government will
make flood insurance available within the community as a financial protection against flood losses.
The SFHAs and other risk premium zones applicable to each participating community are depicted
on Flood Insurance Rate Maps (FIRMs).
Flood hazard zones were established by FEMA from a Flood Insurance Study (FIS) for King
County conducted in 2005, which examined flooding along several major rivers. Although the
primary purpose of the FIS was to establish flood insurance rates, the flood mapping resulting from
these studies is also used for floodplain management and flood hazard mitigation planning. Table
4-2 lists the Flood Insurance Rate Maps developed for areas within the city of Auburn.
Table 4-2. FEMA Flood Insurance Rate Maps Applicable to Auburn
53033C1232K 53033C1253K 53033C1264K
53033C1235K 53033C1254K 53033C1266K
53033C1242K 53033C1261K 53033C1267K
53033C1251K 53033C1262K 53033C1268K
53033C1252K 53033C1263K 53033C1269K
4.2 Stormwater Drainage Infrastructure
As part of the development of this Drainage Plan, the City embarked on a substantial effort to
update its inventory of drainage system infrastructure owned or operated by the stormwater utility.
This will be a continual effort as new data become available and surveys are conducted. An updated
system inventory will provide the City with a database of infrastructure assets which will achieve the
following objectives:
Help to meet regulatory requirements
Provide input for hydraulic models to analyze system conveyance capacity
Serve as a basis for an asset criticality database used to prioritize R&R activities
Support the City’s M&O activities through the CMMS
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Link directly to geographic information systems (GIS) for use in mapping activities.
Appendix D provides a detailed review of the City’s infrastructure data. The review found
inconsistencies between GIS data files and hydraulic modeling data files, and numerous data gaps
also were identified. These discrepancies prompted the effort to update the City’s system inventory.
The system inventory was developed using MIKE URBAN software, which simultaneously provides
input for hydraulic modeling and geospatial data sets that can be exported for use in the City’s GIS.
The magnitude of the effort needed to update infrastructure data throughout the entire City required
the system inventory to be divided into priority-based phases (see Figure 4-6). Priorities for the
system inventory were developed as follows:
High-priority drainage sub-basins include areas with known flooding problems and consist of
the most developed sub-basins near the city’s central core. High-priority sub-basins cover
approximately 4.8 square miles and include sub-basins B, C, D, F, G, H, I, and P. Infrastructure
data for these sub-basins were the first to be updated. Data were validated through a series of
quality control checks such as checking pipe profiles for inconsistencies and verifying the
connectivity of the network. When necessary, as-built drawings were reviewed and additional
field surveys were conducted. In addition, hydraulic modeling (calibrated to reproduce known
flooding problems) was performed for each of these sub-basins, providing further validation of
the drainage system data.
Medium-priority drainage sub-basins include areas that are not known to experience frequent
flooding, but do contain substantial development of infrastructure or are located in close
proximity to known flooding problems. Medium-priority sub-basins cover approximately 8.7
square miles and include sub-basins A, AA, BB, DDD, E, HV, K, L, N, O, R, S, U, V, WC, X,
and Z. Infrastructure data in these sub-basins were the second to be updated. Data updating
activities were the same as for high priority sub-basins, except that hydraulic modeling was not
performed for these drainage systems.
Low-priority drainage sub-basins are located near the city’s central core, but consist of areas that
do not have known flooding problems and contain relatively little infrastructure. Low-priority
sub-basins cover approximately 1.4 square miles and include sub-basins J, TT, PPP, and QQ.
Infrastructure data in these sub-basins were the last to be updated during the development of this
Drainage Plan. Data updating activities were the same as for high priority sub-basins, except that
hydraulic modeling was not performed for these drainage systems.
The remaining sub-basins (shown as “other” in Figure 4-6) were not inventoried as part of this
Drainage Plan, but will be addressed through recommendations for future system inventory
activities (see Chapter 7). These sub-basins include the recently annexed areas of Lea Hill and West
Hill, as well as undeveloped areas and areas covered by other planning activities. The remaining sub-
basins cover approximately 19.3 square miles and include sub-basins AAA, AZ, BBB, CC, DD, EE,
FF, GG, HH, II, JJ, KK, LL, LS, M, MM, OO, NN, NNN, PP, RR, SS, T, UU, W, WW, YY, YYY,
ZZ, and ZZZ.
Table 4-3 provides a summary of stormwater infrastructure.
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Table 4-3. Stormwater Drainage Infrastructure Summary
Infrastructure element GIS data type GIS attribute name Quantitya Units
Pipes, all sizes Polyline Storm lines 900,000 Linear feet
Pipes, all sizes (excluding force mains) Polyline Storm lines 8,800 Count
6–10 in. diameter Polyline Storm lines 3,200 Count
12–15 in. diameter Polyline Storm lines 3,700 Count
16–18 in. diameter Polyline Storm lines 600 Count
20–24 in. diameter Polyline Storm lines 600 Count
27–36 in. diameter Polyline Storm lines 400 Count
38–48 in. diameter Polyline Storm lines 200 Count
60–72 in. diameter Polyline Storm lines 30 Count
Force mains Polyline Storm lines 820 Count
Open channels Polyline Storm lines 106,000 Linear feet
Culverts Polyline Storm lines 11,200 Linear feet
Manholes Point Manhole 4,700 Count
Weirs Point Weir 1 Count
Orifices Point Orifice 1 Count
Outfalls Point Outfall 120 Count
Detention ponds Point Detention pond 120 Count
Infiltration ponds Point Infiltration pond 5 Count
Vaults Point Vault 13 Count
Pump stations Point Pump station 6 Count
a. Quantities have not yet been finalized.
Most of the storm drainage infrastructure is located in the city’s core, between Mill Creek and the
Green River, where development densities are highest. Figure 4-7 shows an overview of the City’s
stormwater drainage infrastructure.
4.3 Critical Facilities
Section 3.2.2 describes policies and LOS goals for managing the City’s critical facilities and critical
stormwater assets. Two groups of policies and LOS goals in particular focus on criticality. The first
applies to critical facilities, stating that the City will manage stormwater runoff within the public
right-of-way in the vicinity of critical facilities to allow access and ensure function of these facilities
at all times, especially during large storm events (LOS Goal 1). Nine critical facilities have been
identified and included in Table 4-4.
The second group of policies relates to the management of the City’s critical stormwater assets (LOS
Goals 6–9). The City is modifying its inspection and maintenance practices to prioritize active
management of facilities with the highest combined risk and consequence of failure (i.e., a criticality-
based maintenance program). Factors that impact criticality include the age of the asset, the repair
history of the asset, and the financial consequences of a failure. The consequences of a system
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failure impacting a hospital or school are considered more serious then a residence or unoccupied
property, and are thus assigned as critical assets. The City has identified six stormwater pump
stations as critical assets, as listed in Table 4-4. The list of critical stormwater assets may expand as
the City refines its criticality database by adding information (e.g., inspection and repair logs, asset
age; see LOS Goal 6). The locations of these critical facilities are shown in Figure 4-8.
Table 4-4 Critical Facilities
City critical facilities Address
City Hall 25 W Main Street
IS Dept. Office 8 1st Street SE
Justice Center 340 E Main Street
M&O Facility 1305 C Street SW
Regional Hospital 201 N Division Street
Senior Center 808 9th Street SE
VRFA Station 31 1101 D Street SE
VRFA Station 32 1951 R Street SE
VRFA Station 35 2905 C Street SW
Storm drainage critical facilities Address
A Street PS 404 A Street SE
Auburn Way S PS 405 Auburn Way S
Brannan Park PS 1302 30th Street NE
Emerald Park PS 499 42nd Street NE
West Main St. PS 1410 W. Main Street
White River PS 4640 A Street SE
4.4 Water Quality
This section describes the existing water quality and regulatory conditions that affect surface water
quality in Auburn and describes upcoming processes that are required to maintain compliance with
the City’s NPDES Permit.
4.4.1 Existing Water Quality Conditions
According to water resource inventories by Ecology, the main water bodies within the City’s
administrative boundaries include the Green River, Mill Creek, White Lake, White River, and
Bowman Creek. The City’s NPDES Permit requires that these water bodies meet water quality
standards and criteria. Municipal storm sewers that discharge runoff from urban areas to surface
waters are not authorized to violate state water quality standards.
Appendix 2 of the NPDES Permit describes water bodies that have been assessed as impaired and
have additional requirements based on established TMDLs. There are no approved TMDLs for the
City’s current NPDES Permit; however, several water bodies within the city are currently being
evaluated and could be included in the next NPDES Permit, which becomes effective in 2012. If
Ecology establishes TMDLs for one or more of these water bodies prior to 2012, the next version
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of the City’s NPDES Permit may contain additional requirements, such as increased monitoring and
developing methods for reducing pollutant loads.
The Green River is being evaluated for potential TMDLs for dissolved oxygen and temperature. Mill
Creek is being examined for potential TMDLs for temperature, fecal coliform, dissolved oxygen,
and copper. And the lower White River currently is under evaluation for potential TMDLs for pH
and temperature.
4.4.2 Water Quality Regulatory Compliance
The City has a well-developed municipal stormwater system M&O program that employs and
provides training on numerous processes and procedures to minimize water quality impacts from
municipal operations. The City also actively implements BMPs into its municipal activities. BMPs
are the schedules of activities, prohibitions of practices, maintenance procedures, and structural
and/or managerial practices that prevent or reduce the release of pollutants and other adverse
impacts to waters of Washington State. In addition, the City implements AKART, a methodology
which applies all known, available, and reasonable methods of prevention, control, and treatment to
the City’s practices. Although the current Permit does not require water quality monitoring, the City
currently conducts limited water quality monitoring through its Planning Department.
The City is in full compliance with its NPDES Permit, with programs, codes, processes, and
procedures that meet all of the current Permit requirements. However, the City will need to make
several changes to comply with Permit requirements that take effect during the remainder of this
Permit cycle. The City’s 2009 Stormwater Management Program (SWMP) contains a summary of
the Permit requirements and descriptions of the City’s current and planned activities for Permit
compliance (see Appendix C).
Additional discussion on regulatory compliance is contained in Section 5.3. Recommendations for
NPDES compliance and a timeline of activities are provided in Section 7.3.
4.5 Existing Drainage Problems
Members of the City staff working within the stormwater utility are experienced and familiar with
the condition of the drainage system. Several of the existing drainage problems that have been
observed by the staff are known to cause frequent flooding of roadways and adjacent property. Most
notably, a severe storm event occurring in November 2007 caused substantial flooding in several
locations. The most apparent problems have been identified for further analysis (see Hydraulic
Investigation, Section 5.1). These problems are described in Table 4-5 and the locations are mapped
in Figure 4-9. Problems that reveal deficiencies in the drainage system will be addressed through
capital improvements (see Chapter 6).
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Table 4-5. List of Known High-Priority Drainage Problems
No. Sub-basin Location Description
Approximate frequency
or last noted occurrence
P1 B Intersection: Auburn
Way S and SR 18
During heavy rain storms, stormwater ponds in Auburn Way S
(principal arterial) inhibiting traffic flow, encroaching on private
properties, and blocking access to Highway 18.
Annual road closures
P2 C Intersection: Second
St. SE and G St. SE
Surcharging of manholes in the intersection during large rain
events inhibits traffic on both 2nd St. SE (residential collector
street) and G St. SE (local street). The manhole is located in a
local low point, and water encroaches on private properties.
System surcharging about
once every 5 years
P3 C Intersection: F St. SE
and SR 18
Stormwater runoff flows overland to the north flooding F St. SE
(non-residential collector street) and encroaching on private
properties.
Annual road closures
P4 C M St. SE near Third
St. SE
The storm drain in M St. SE (principal arterial roadway) runs very
full and overflows occasionally to cause local property damage
and partial road flooding near 6th St. SE.
High flows regularly; no
observed overflows
P5 P West Main St. dead
end near SR 167
Stormwater has overflowed from the catch basin located in the
appliance store driveway causing property damage and blockage
of Old West Main St. (local street).
Catch basins surcharging
about once every five
years
P6 H, I Intersection: 30th St.
NE and C St. NE
Stormwater ponds located in the northwest portion of the airport
can overflow, inundating portions of 30th St. N and C St. NE,
both non-residential collector streets and encroaching on private
properties.
December 2007
P7 H C St. NE near 37th St.
NE
Stormwater has overflowed from manholes located along C St.
NE (non-residential collector street), in particular the manhole
located 600 ft south of 37th St. NE. (minor arterial roadway)
flooding both and encroaching on private properties.
December 2007
In addition to the specific locations listed above, drainage problems have been observed in the
Mullen Slough drainage and along Mill Creek.
Mullen Slough Tributaries. Severe erosion and sedimentation problems have been observed in
newly annexed areas of West Hill, which led to a moratorium on development in the contributing
drainage area. Erosion and down-cutting along Mullen Slough Tributaries 0045 and 0047 prompted
King County to conduct a study focused on alternatives for ravine stabilization (King County, 2008).
The instability of these tributaries contributes to chronic flooding, sedimentation, and fish habitat
problems along Mullen Slough (King County, 2008).
Tributaries 0045 and 0047 drain uplands on the north side of the West Hill area. Both tributaries
descend the valley wall in steep-sided, high-gradient ravines that transition abruptly to the low-
gradient valley floor. Sediment from the ravines is deposited along the valley floor, which consists of
a network of poorly maintained drainage ditches leading to wetlands along Mullen Slough.
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According to the King County report (2008), Tributary 0045 drains to Venture ditch, which has
been reported to overflow, sending surface water west into Mullen Slough and north across South
287th. Within the ravine Tributary 0045 exhibits a highly unstable channel where channel incision is
the dominant erosion process. In some places the channel has incised as much as 8 feet (King
County, 2008).
Runoff to Tributaries 0045 and 0047 has increased as a result of land and road development within
the drainage area (King County, 2008), which has likely contributed to the erosion and down-cutting
that have occurred.
Mill Creek. Aggradation and vegetative growth along Mill Creek have reduced the capacity of the
channel to convey flow, which exacerbates flooding during large rainfall events. Increased water
surface elevations along Mill Creek cause high tailwater conditions at the City’s drainage outfalls,
which reduces the hydraulic capacity of the drainage system and increases the likelihood of flooding
upstream.
Another flooding problem observed along Mill Creek is water ponding on the Interurban Trail
(transportation and recreation route for non-motorized vehicles). High water levels from Mill Creek
frequently inundate low areas along the trail near South 37th Street.
4.6 Potential Future Drainage Problems
As described in Section 4.1.8, stormwater regulations and development standards are intended to
minimize future increases in stormwater runoff. However, there will be special circumstances,
deviations, or aggregated small increases that could lead to future drainage problems. Some of those
problems will become apparent over time; therefore, City staff should continue to monitor the
system and track new problems as they occur.
Stormwater Controls for the Downtown Area. One such known special circumstance relates to
the City’s downtown area, which is designated as a special land use area by the City’s Comp Plan (see
Figure 4-10). In 2004, the area in the vicinity of downtown Auburn was designated as an urban
center (DUC), with plans to revitalize the area, consistent with state, regional, and local growth
management concepts. At that time, several incentives for developing within the DUC were created,
some of which pertained to stormwater management. For example, one of the incentives included
the “elimination of stormwater improvements for redevelopment of existing sites that do not result
in an increase in impervious surface.”
However, Auburn’s 2007 NPDES Permit contains new requirements that affect development
procedures within the City, including the DUC. The City will no longer be able to exempt
development in the DUC from stormwater control requirements. Onsite stormwater controls in the
downtown area are difficult to implement because the high density of the existing land use imposes
strict spatial constraints on redevelopment of those areas. Consequently, the City may need to
consider alternative methods for meeting regulatory requirements without compromising the ability
to redevelop the downtown area (see Chapter 7 for study recommendations).
THIS PAGE INTENTIONALLY LEFT BLANK.
B ST NW
L a k e
T a p p s
B i g S o o s C
Mill Creek
R i v e r
G
r
e
e
n
R
i
ver
M
i l l
C
r e e k
Creek
Mill
G
r
e
e
n
R
i
v
e
r
G
r
e
e
n
River
W h i t e
G
r
e
e
n
R i v e r
Soosette
Creek
B o w m a n
C
r
e
e
k
W h i t e
R iv e r
White
Lake
M
u
l
l
e
n
S
l
o
u
g
h
Green
Ri v e r
Lake
Meridian
SR 167
SR 18
A ST SE
C ST SW
B ST NW
I ST NE
AUBURN WAY N
A
U
B
U
R
N
W
A
Y
S
R ST SE
132ND AVE SE
RA M P
WEST VALLEY HWY NW
M ST SE
8TH ST E
E MAIN ST
24TH ST E
124TH AVE SE
122ND AVE E
BUTTE AVE
110TH AVE E
15TH ST SW
EAST VALLEY HWY SE
2ND ST E
C ST NE
SE 312TH ST
S 277TH ST
W MAIN ST
15TH ST NW
C ST NW
J
O
VIT
A B
LV
D
S 384TH ST
SE 288TH ST
198TH AVE E
53RD ST SE
9TH ST E
29TH ST SE
1
7
9
T
H
A
V
E
SE 320TH ST
114TH AVE E
116TH AVE SE
EDWARDS RD E
LAKE TAPPS PKWY SE
4 1 S T S T S E
W
E
S
T
VA
L
L
E
Y
H
W
Y
S
W
S T U C K R I V E R D R
16TH ST E
K
E
R
S
E
Y
W
A
Y
S
E
4TH ST E
18TH ST E
M ST NE
12TH ST E
SE 304TH ST
190TH AVE E
112TH AVE E
3RD AVE SE
ELLINGSON RD SW
37TH ST SE
GREEN VALLEY RDPERIMETER RD
SE 272ND ST
4
6
T
H
P
L
S
8TH ST NE
182ND AVE
E
147TH AVE SE
37TH ST NW
ACADEMY DR SE
SE LAKE HOLM RD
22ND ST NE
L
A
K
E
L
A
N
D
H
I
L
L
S
W
A
Y
S
E
O R A V E T Z R D S E
VALENTINE AVE SE
C
U
T
O
F
F
5
1
S
T
AV
E
S
SE 282ND ST
144TH AVE SE
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
55TH AVE S
1
8
5
T
H
A
V
E
E 214TH AVE E
D ST SE
1ST AVE SE
TACOMA BLVD
D ST NW
A ST NE
4TH ST SE
TBD
CELERY AVE
30TH ST NE
10
8T
H AVE
EAST BLVD (BOEING)
112T
H AVE SE
SE 316TH ST
148TH AVE SE
T
A
C
O
M
A
P
O
I
N
T
D
R
E
55TH ST SE
E
V
E
R
G
R
E
E
N
W
A
Y
S
E
D ST NE
M ST NW
O ST NE
W ST NW N ST NE
1
6
9
T
H
A
V
E
E
S 287TH ST
3RD AVE S
1
8
6
T
H
A
V
E
E
5TH AVE SW
E ST NE
37TH ST NE
142ND AVE E
S 316TH ST
H
A
R
V
E
Y
R
D
SE 368TH PL
S
C
E
N
I
C
D
R
S
E
H ST NW
M
A
I
N
S
T
S 292ND ST
WEST BLVD (BOEING)
S 300TH PL
44TH ST NW
3RD AVE SW
118TH AVE E
10TH ST NE
CLAY ST NW
4TH AVE SW
148TH AVE E
7TH ST SE
137TH AVE E
2
6
T
H
S
T
E
136TH AVE E
SE 310TH ST
S 3RD AVE
THORTON AVE SW
2
0
0
T
H
A
V
E
E
R I V E R D R
BOUNDARY BLVD
L E A H I L L R D S E
32ND ST E
118TH AVE SE
58
T
H AVE S
S 364TH PL ALGONA BLVD N
104TH AVE SE
S 372ND ST
J ST NE
ROY RD SW
4TH ST NE
PACIFIC AVE S
110TH AVE SE
D
R
I
V
E
W
A
Y
SE 281ST ST
126TH AVE E
5TH ST SE
72
N
D
A
V
E
S
56TH PL S
2
5
T
H
S
T E
BRIDGET AVE SE
I ST SE
57TH AVE S
S 328TH ST
DOGWOOD ST SE
2ND AVE SW
8TH ST SE
S 279TH ST
L ST SE
3RD AVE NW
T ST SE
F ST SE
FR O NTA G E R D
FOSTER AVE SE
52ND AVE S
H ST SE
SE 274TH ST
G ST SE
1ST ST E
166TH AVE E
S 350TH ST
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
4 9TH S T NE
S 362ND ST
H
O
W
A
R
D
R
D
I ST NW
32ND PL NE SE 296TH WAY
54TH AVE S
11TH AVE N
A ST SW
U
S
T
N
W
SEATTLE BLVD S
7
8
T
H
A
V
E
S
3RD ST E
D
E
E
R
I
S
L
A
N
D
D
R
E
135TH AVE SE
4 7 T H S T S E
2
0
4
T
H
A
V
E
E
28TH ST NE
8
6
T
H
A
V
E
S
S 356TH ST
J ST SE
R ST NW
MILL POND DR SE
27TH ST E
15TH ST E
28TH ST E
MILITARY RD S
13TH ST E
K ST SE
OLIVE AVE SE
10TH ST E
108TH AVE E
85TH AVE S
31ST ST NE
SE 323RD PL
54TH PL S
B ST SE
WYMAN DR
26TH ST SE
S 336TH ST
ST PAUL BLVD
2ND ST NW
S 340TH ST
C ST SE
B ST NE
29TH ST E
32ND ST SE1ST AVE S
36TH ST SE
ELM LN
SE 301ST ST
2
0
8
T
H
A
V
E
E
SE 287TH ST
V ST NW
2ND ST SE
23RD ST SE
4TH AVE S
3RD ST SE
QUINCY AVE SE
21ST ST NE
1
5
6
T
H
A
V
E
E
140TH AVE E
HEMLOCK ST SE
1
8
4
T
H
C
T
E
5
6
T
H
A
V
E
S
SE 298TH PL30TH ST NW
30TH ST SE
64TH AVE S
S 318TH ST
24TH ST SE
14TH ST E
H ST NE
LUND RD SW
22ND ST SE
S 324TH ST
PIKE ST NW
21ST ST E
31ST ST E
42ND ST NW
6TH AVE SW
17TH ST E
SUPERMALL DR SW
119TH
AV
E E
SE 286TH ST
9TH ST SE
5 5 T H P L S
SE 276TH PL
65TH AVE S
SE 295TH PL
G ST NE
S 2
9
7
T
H
P
L
O ST SE
2 7T H ST SE
5TH AVE N
SKINNER RD
125TH AVE E
1
0
2
N
D
A
V
E
S
E
128TH AVE E
S 354TH ST
S 344TH ST
SE 290TH ST
10TH ST SE
D ST SW
SE 280TH ST
SE 283RD PL
2
1
1
T
H
A
V
E
E
NATHAN AVE SE
V ST SE
4 5 T H S T N E
HI CREST DR
B PL NW
SE 294TH ST
7 2ND S T S E
S 285TH ST
6TH ST NW
146TH AVE SE
SE 293RD ST
3RD ST NW
126TH AVE SE
16TH ST SE
I
S
A
A
C
A
V
E
S
E
S 3 1 2 T H S T
L ST NE
ELM ST SE
S 370TH ST
20TH ST E
7TH ST E
19TH DR NE
SE 307TH PL
5 1 S T S T S E
10TH AVE N
S 364TH ST
SE 277TH PL
140TH AVE SE
28TH ST SE
PERRY AVE SE
SE 42ND ST
S 303RD PL
133RD AVE SE
108TH AVE SE
7 3 R D S T S E
SE 295TH ST
14TH ST SE
26TH ST NE
S 366TH ST
SE 297TH ST
2
1
0
T
H
A
V
E
E
24TH ST NE
SE 296TH ST
SE 285TH ST
S 368TH ST
61ST AVE S
ALDER LN S
117TH AVE SE
U ST SE
19TH ST SE
6TH ST SE
110TH PL SE
WARD AVE SE
SE 286TH PL
21ST ST SE
R PL NE
117TH
AV
E E
107TH PL SE
33RD ST SE
105TH
AVE SE
117TH PL SE
7TH ST
30TH ST E
5TH ST NE
53RD AVE S
HEATHER AVE SE
F ST NE
11
2T
H
PL
SE
51ST PL S
SE 292ND ST
S 320TH ST
SE 272ND PL
18TH ST NE
8TH ST SW
6TH AVE N
22ND ST E
123RD AVE E
63RD PL S
3RD AVE NE
130TH AVE SE
1ST ST NE
R ST NE
129TH PL SE
6TH ST NE
115TH AVE E
111TH AVE E
S 342ND ST
26TH ST NW
2 2 N D S T C T E
121ST AVE SE
SE 315TH ST
111TH PL SE
S 329TH PL
SE 321ST PL
114TH PL SE
SE 292ND ST
24TH ST E
RAMP
R A M P
SR 167
RAMP
SR 167
17TH ST E
V ST SE
SE 282ND ST
WES
T
VALLEY
HWY SW
RAM
P
53RD AVE S
TBD
25TH ST E
SR 167
16TH ST E
SE 294TH ST
O ST NE
142ND AVE E
R A M P
SE 272ND ST
13TH ST E
56TH AVE S
2ND ST SE
12TH ST E
17TH ST SE
S
R
1
6
7
SE 301ST ST
TBD
200TH AVE E
RA
M
P
SE 296TH ST
104TH AVE SE
R
A
M
P
9TH ST E
RAMP
8TH ST NE
133RD AVE SE
112TH AVE SE
T B D
52ND AVE S
16TH ST E
TBD
RAMP
SE 282ND ST
51ST AVE S
RAMP
TBD
D ST SE
TBD
2ND ST SE
K ST SE
S 277TH ST
51ST AVE S
24TH ST SE
24TH ST E
RAMP
S 277TH ST
55TH AVE S
SR 167
S R 1 8
R ST NW
SR 18
SR 167
SE 288TH ST
110TH AVE SE
R A M P
M ST NW
TBD
21ST ST E
R A M P
RA
M
P
R A M P
25TH ST SE
RA
M
P
RAMP
T
B
D
124TH AVE SE
SR 18
SR 167
SR 18
TBD
18TH ST E
SE 284TH ST
M ST NE
8TH ST E
TBD
D
R
I
V
E
W
A
Y
TBD
135TH AVE SE
TBD
144TH AVE SE
DRIVEWAY
RAMP
8TH ST E
T B D
SR 167
SR 167
D
RIV
E
W
A
Y
R ST NW
55TH AVE S
28TH ST SE
26TH ST NE
32ND ST E
SR 18
C ST NW
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 3,663 feet
December 2009
L E G E N D
Roadway
Watercourse
Water Body
Wetland
Auburn City Boundary
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig4-1.mxd
2,00002,0004,000
Feet [N
FIGURE 4-1
NATURAL DRAINAGE
FEATURES OF THE
CITY OF AUBURN
!
!
!
!
!
!
!
L a k e
T a p p s
B i g S o o s C r e e k
Mill Creek
R i v e r
G
r
e
e
n
R
i
ver
M
i l l
C
r e e k
Creek
Mill
G
r
e
e
n
R
i
v
e
r
G
r
e
e
n
River
W h i t e
G
r
e
e
n
R i v e r
Soosette
Creek
River
W
h i t
e
B o w m a n
C
r
e
e
k
W h i t e
R iv e r
R i v e r
White
Lake
M
u
l
l
e
n
S
l
o
u
g
h
Green
R iv e r
Lake
Meridian
W h i t e
S
R
1
6
7
S R 1 8
A ST SE
C ST SW
A
U
B
U
R
N
W
A
Y
S
B ST NW
I ST NE
AUBURN WAY N
R ST SE
132ND AVE SE
RA M P
WEST VALLEY HWY NW
M ST SE
8TH ST E
E MAIN ST
24TH ST E
124TH AVE SE
EAST VALLEY HWY SE
JOVITA BLVD
122ND AVE E
BUTTE AVE
S 384TH ST
110TH AVE E
15TH ST SW
SE 288TH ST
2ND ST E
C ST NE
SE 312TH ST
S 277TH ST
W MAIN ST
15TH ST NW
C ST NW
198TH AVE E
53RD ST SE
9TH ST E
29TH ST SE
GREEN VALLEY RD
1
7
9
T
H
A
V
E
SE 320TH ST
114TH AVE E
116TH AVE SE
EDWARDS RD E
LAKE TAPPS PKWY SE
41ST ST SE
WEST VALLEY HWY SW
S T U C K R I V E R D R
16TH ST E
K
E
R
S
E
Y
W
A
Y
S
E
147TH AVE SE
4TH ST E
18TH ST E
M ST NE
12TH ST E
SE 304TH ST
1
9
0
T
H
A
V
E
E
112TH AVE E
3RD AVE SE
ELLINGSON RD SW
37TH ST SE
PERIMETER RD
SE 272ND ST
4
6
T
H
P
L
S
8TH ST NE
182ND AVE E
37TH ST NW
ACADEMY DR SE
SE LAKE HOLM RD
22ND ST NE
L
A
K
E
L
A
N
D
H
I
L
L
S
W
A
Y
S
E
O R A V E TZ R D S E
VALENTI
NE AVE SE
C
U
T
O
F
F
51ST
AV
E S
SE 282ND ST
144TH AVE SE
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
55TH AVE S
1
8
5
T
H
A
V
E
E
214TH AVE E
D ST SE
1ST AVE SE
TACOMA BLVD
D ST NW
A ST NE
4TH ST SE
TBD
CELERY AVE
30TH ST NE
10
8T
H AVE
EAST BLVD (BOEING)
112
T
H AVE SE
SE 316TH ST
148TH AVE SE
T
A
C
O
M
A
P
O
I
N
T
D
R
E
A
U
B
U
R
N
-
E
N
U
M
C
L
A
W
R
D
55TH ST SE
E
V
E
R
G
R
E
E
N
W
A
Y
S
E
EMERALD DOWNS DR NW
D ST NE
M ST NW
O ST NE
S
E
3
6
8
T
H
P
L
W ST NW
1
6
9
T
H
A
V
E
E
S 287TH ST
3RD AVE S
5TH AVE SW
E ST NE
37TH ST NE
142ND AVE E
S 316TH ST
H
A
R
V
E
Y
R
D
S
C
E
N
I
C
D
R
S
E
H ST NW
M
A
I
N
S
T
S 292ND ST
WEST BLVD (BOEING)
44TH ST NW
3RD AVE SW
118TH AVE E
10TH ST NE
CLAY ST NW
4TH AVE SW
148TH AVE E
7TH ST SE
137TH AVE E
2
6
T
H
S
T
E
136TH AVE E
SE 310TH ST
S 3RD AVE
THORTON AVE SW
2
0
0
T
H
A
V
E
E
R I V E R D R
BOUNDARY BLVD
L E A H I L L R D S E
32ND ST E
118TH AVE SE
58TH AVE S
ALGONA BLVD N
104TH AVE SE
S 372ND ST
J ST NE
ROY RD SW
4TH ST NE
PACIFIC AVE S
110TH AVE SE
14TH ST NE
D
R
I
V
E
W
A
Y
SE 281ST ST
126TH AVE E
5TH ST SE
72ND AVE S
56TH PL S
25TH ST E
BRIDGET AVE SE
57TH AVE S
S 328TH ST
DOGWOOD ST SE
2ND AVE SW
8TH ST SE
S 279TH ST
L
S
T
S
E
T ST SE
F
ST
S
E
FR O NTA G E RD
C
O
T
TA
G
E
R
D
E
FO
ST
E
R
A
V
E
S
E
52ND AVE S
SE 274TH S T
1ST ST E
166
TH
A
V
E
E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
4 9TH S T NE
S 362ND ST
NO
R
M
AN
A
V
E
S
E
I
S
T
N
W
54
TH
AV
E
S
A ST SW
57TH PL S
U
S
T
N
W
32ND ST NE
7
8
T
H
A
V
E
S
3RD ST E
D
E
E
R
I
S
L
A
N
D
D
R
E
135
T
H
A
V
E
S
E
4 7 T H S T S E
2
0
4
T
H
A
V
E
E
28TH ST NE
8
6
T
H
A
V
E
S
S 356TH ST
J
ST
SE
R ST NW
27TH ST E
15TH ST E
28TH ST E
MIL
I
T
AR
Y
R
D
S
13TH ST E
K
ST
S
E
OLIVE AVE SE
10TH ST E
10
8T
H AVE E
SE 323RD PL
54TH PL S
B ST SE
WYMAN DR
26TH ST SE
S 336TH ST
ST PAUL BLVD
S 340TH ST
C
ST
S
E
B ST NE
32ND ST SE
S 300TH S T
1ST AVE S
36TH ST SE
ELM LN
SE 301ST ST
2
0
8
T
H
A
V
E
E
SE 287TH ST
V ST NW
2ND ST SE
23RD ST SE
4TH AVE S
3RD ST SE
QUINCY AVE SE
29TH ST NW
21ST ST NE
1
5
6
T
H
A
V
E
E
HEMLOCK ST SE
1
8
4
T
H
C
T
E
5
6
T
H
A
V
E
S
10
6T
H
A
V
E
E
SE 298TH PL30TH ST NW
30TH ST SE
S 318TH ST
24TH ST SE
2ND AVE S
14TH ST E
H ST NE
LUND RD SW
S 324TH ST
PIK
E
S
T
NW
21ST ST E
31ST ST E
42ND ST NW
6TH AVE SW
17TH ST E
119TH
AV
E E
SE 286TH ST
9TH ST SE
55TH PL S
SE 276TH PL
65TH AVE S
SE 295TH PL
G ST NE
27 TH ST SE
5TH AVE N
SKINNER RD
1
0
2
N
D
A
V
E
S
E
128TH AVE E
S 354TH ST
S 344TH ST
SE 364TH ST
SE 290TH ST
10TH ST SE
D ST SW
SE 280TH ST
2
1
1
T
H
A
V
E
E
NATHAN AVE SE
V ST SE
HI CREST DR
B PL NW
SE 294TH ST
S 285TH ST
6TH ST NW
146TH AVE SE
SE 293RD ST
PEA
R
L
A
V
E
S
E
3RD ST NW
126TH AVE SE
I
S
A
A
C
A
V
E
S
E
S 3 1 2 T H S T
ELM ST SE
CLAY ST
S 370TH ST
20TH ST E
52ND PL S
7TH ST E
19TH DR NE
SE 307TH PL
5 1 S T S T S E
10TH AVE N
S 364TH ST
140TH AVE SE
28TH ST SE
72 N D ST SE
15TH ST SE
13
3
R
D
A
V
E
S
E
10
8
T
H
A
VE
S
E
73RD ST SE
SE 295TH ST
26TH ST NE
S 366TH ST
SE 297TH ST
2
1
0
T
H
A
V
E
E
66TH ST SE
24TH ST NE
SE 296TH ST
SE 285TH ST
S 368TH ST
ALDER LN S
11
7
TH
A
V
E
S
E
U ST SE
19TH ST SE
6TH ST SE
110TH PL SE
A ST E
156TH AVE SE
21ST ST SE
R PL NE
117TH AVE E
105TH AVE SE
7TH ST
5TH ST NE
53
R
D A
V
E
S
HE
AT
H
E
R
A
V
E
S
E
F ST N
E
11
2T
H
PL SE
51
ST
P
L
S
SE 292ND ST
D PL SE
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
123RD AVE E
63RD PL S
THORTON PL SW
2ND CT NW
1ST ST NE
129TH PL SE
6TH ST NE
3RD ST NE
O C
T
S
E
S 342ND ST
105TH AVE E
26TH ST NW
SE 321ST PL
114TH PL SE
53RD AVE S
TB
D
118TH AVE SE
148TH AVE SE
RAMP
SE 296TH ST
32ND ST E
RAMP
106TH AVE E
SE 274TH ST
SR 167
R ST NW
17TH ST SE
D
RIV
E
W
A
Y
SE 301ST ST
RAMP
RAMP
SR 167
TBD
SR 167
RAMP
RAMP
T
B
D
SR 167
SE 272ND ST
TBD
S 277TH ST
R
A
M
P
108TH AVE E
M ST NE
DRIVEWAY
56TH AVE S
SR 18
SR 18
H ST NE
RAMP
R A M P
SR 167
21ST ST E
144
T
H
AV
E
S
E
SE 282ND ST
T
B
D
R A M P
DRIVEWAY
SR 167
16TH ST E
55TH AVE S
TBD
D
R
I
V
E
WAY
108TH AVE E
S 277TH ST
10
8
TH
A
VE
S
E
R AM P
51ST AVE S
13TH ST E
8TH ST E
5 1 S T S T S E
TBD
SR 18
32ND ST E
R
A
M
P
24TH ST E
5 5 T H P L S
51ST AVE S
SR 167
RAMP
104TH AVE SE
12TH ST E
SE 284TH ST
2ND ST SE
RA
M
P
D ST SE
26TH ST NE
SE 272ND ST
TBD
124TH AVE SE
R ST NW
9TH ST E
V ST SE
TBD
8TH ST E
1ST AVE N
S R 1 8
T B D
TBD
SE 282ND ST
200TH AVE E
R A M P
R A M P
R A M P
TBD
TBD
110TH AVE SE
SR 167
8TH ST NE
C ST N
W
T
B
D
RAMP
TBD
B
JJ
C
T
LS
OO
E
ZZ
V
H
A
M
AZ
I CCC
II
U EE
J
NN
K
S
FF
UU
AA
KK
HH
W
P
SS
YY
QQ
O
MM
RR
LL
DD
CC
N
L
GG
TT
PP
HV
D
G
AAA
ZZZ
F
I
NNN
PPP
Z R
YYY
X
WC
WW
BBB
DDD
BB
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 4,000 feet
December 2009
L E G E N D
Roadway
Watercourse
Water Body
Wetland
Auburn City Boundary
Subbasins
Major receiving water
Green River
Mill Creek
Mullen Slough
Soosette/Big Soos Creeks
White River
Outfalls
Green River
Mill Creek
White River
Other stream
!Wetland
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig4-2(subbasins).mxd
2,00002,0004,000
Feet [N
FIGURE 4-2
DRAINAGE SUB-BASINS
FOR THE CITY OF AUBURN
STORMWATER UTILITY
L a k e
T a p p s
B i g S o o s C r e e k
Mill Creek
R i v e r
G
r
e
e
n
R
i
ver
M
i l l
C
r e e k
Creek
Mill
G
r
e
e
n
R
i
v
e
r
G
r
e
e
n
River
W h i t e
G
r
e
e
n
R i v e r
Soosette
Creek
River
W
h i t
e
B o w m a n
C
r
e
e
k
W h i t e
R iv e r
R i v e r
White
Lake
M
u
l
l
e
n
S
l
o
u
g
h
Green
R iv e r
Lake
Meridian
W h i t e
S
R
1
6
7
S R 1 8
A ST SE
C ST SW
A
U
B
U
R
N
W
A
Y
S
B ST NW
I ST NE
AUBURN WAY N
R ST SE
132ND AVE SE
RA M P
WEST VALLEY HWY NW
M ST SE
8TH ST E
E MAIN ST
24TH ST E
124TH AVE SE
EAST VALLEY HWY SE
JOVITA BLVD
122ND AVE E
C ST NW
BUTTE AVE
S 384TH ST
110TH AVE E
15TH ST SW
SE 288TH ST
2ND ST E
C ST NE
SE 312TH ST
S 277TH ST
W MAIN ST
15TH ST NW
198TH AVE E
53RD ST SE
9TH ST E
29TH ST SE
GREEN VALLEY RD
1
7
9
T
H
A
V
E
SE 320TH ST
114TH AVE E
116TH AVE SE
EDWARDS RD E
LAKE TAPPS PKWY SE
41ST ST SE
WEST VALLEY HWY SW
S T U C K R I V E R D R
16TH ST E
K
E
R
S
E
Y
W
A
Y
S
E
147TH AVE SE
4TH ST E
18TH ST E
M ST NE
12TH ST E
SE 304TH ST
1
9
0
T
H
A
V
E
E
112TH AVE E
3RD AVE SE
ELLINGSON RD SW
37TH ST SE
PERIMETER RD
SE 272ND ST
4
6
T
H
P
L
S
8TH ST NE
182ND AVE E
37TH ST NW
ACADEMY DR SE
SE LAKE HOLM RD
22ND ST NE
L
A
K
E
L
A
N
D
H
I
L
L
S
W
A
Y
S
E
O R A V E TZ R D S E
VALENTI
NE AVE SE
C
U
T
O
F
F
51ST
AV
E S
SE 282ND ST
144TH AVE SE
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
55TH AVE S
1
8
5
T
H
A
V
E
E
214TH AVE E
D ST SE
1ST AVE SE
TACOMA BLVD
D ST NW
A ST NE
4TH ST SE
TBD
CELERY AVE
30TH ST NE
10
8
T
H AVE
EAST BLVD (BOEING)
112
T
H AVE SE
SE 316TH ST
148TH AVE SE
T
A
C
O
M
A
P
O
I
N
T
D
R
E
A
U
B
U
R
N
-
E
N
U
M
C
L
A
W
R
D
55TH ST SE
E
V
E
R
G
R
E
E
N
W
A
Y
S
E
EMERALD DOWNS DR NW
D ST NE
M ST NW
O ST NE
S
E
3
6
8
T
H
P
L
W ST NW
1
6
9
T
H
A
V
E
E
S 287TH ST
3RD AVE S
5TH AVE SW
E ST NE
37TH ST NE
142ND AVE E
S 316TH ST
H
A
R
V
E
Y
R
D
S
C
E
N
I
C
D
R
S
E
H ST NW
M
A
I
N
S
T
S 292ND ST
WEST BLVD (BOEING)
44TH ST NW
3RD AVE SW
118TH AVE E
10TH ST NE
CLAY ST NW
4TH AVE SW
148TH AVE E
7TH ST SE
137TH AVE E
2
6
T
H
S
T
E
136TH AVE E
SE 310TH ST
S 3RD AVE
THORTON AVE SW
2
0
0
T
H
A
V
E
E
R I V E R D R
BOUNDARY BLVD
L E A H I L L R D S E
32ND ST E
118TH AVE SE
58TH AVE S
ALGONA BLVD N
104TH AVE SE
S 372ND ST
J ST NE
ROY RD SW
4TH ST NE
PACIFIC AVE S
110TH AVE SE
14TH ST NE
D
R
I
V
E
W
A
Y
SE 281ST ST
126TH AVE E
5TH ST SE
72ND AVE S
56TH PL S
25TH ST E
BRIDGET AVE SE
57TH AVE S
S 328TH ST
DOGWOOD ST SE
2ND AVE SW
8TH ST SE
S 279TH ST
L
S
T
S
E
T ST SE
F
ST
S
E
FR O NTA G E RD
C
O
T
TA
G
E
R
D
E
FO
ST
E
R
A
V
E
S
E
52ND AVE S
SE 274TH S T
1ST ST E
166
TH
A
V
E
E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
4 9TH S T NE
S 362ND ST
NO
R
M
AN
A
V
E
S
E
I
S
T
N
W
32ND PL NE
54
TH
AV
E
S
A ST SW
57TH PL S
U
S
T
N
W
7
8
T
H
A
V
E
S
3RD ST E
D
E
E
R
I
S
L
A
N
D
D
R
E
135
T
H
A
V
E
S
E
4 7 T H S T S E
2
0
4
T
H
A
V
E
E
28TH ST NE
8
6
T
H
A
V
E
S
S 356TH ST
J
ST
SE
R ST NW
27TH ST E
15TH ST E
28TH ST E
MIL
I
T
AR
Y
R
D
S
13TH ST E
K
ST
S
E
OLIVE AVE SE
10TH ST E
10
8
T
H AVE E
31ST ST NE
SE 323RD PL
54TH PL S
B ST SE
WYMAN DR
26TH ST SE
S 336TH ST
ST PAUL BLVD
S 340TH ST
C
ST
S
E
B ST NE
32ND ST SE
S 300TH S T
1ST AVE S
36TH ST SE
ELM LN
SE 301ST ST
2
0
8
T
H
A
V
E
E
SE 287TH ST
V ST NW
2ND ST SE
23RD ST SE
4TH AVE S
3RD ST SE
QUINCY AVE SE
29TH ST NW
21ST ST NE
1
5
6
T
H
A
V
E
E
HEMLOCK ST SE
1
8
4
T
H
C
T
E
5
6
T
H
A
V
E
S
10
6T
H
A
V
E
E
SE 298TH PL30TH ST NW
30TH ST SE
S 318TH ST
24TH ST SE
2ND AVE S
14TH ST E
H ST NE
LUND RD SW
S 324TH ST
PIK
E
S
T
NW
21ST ST E
31ST ST E
42ND ST NW
6TH AVE SW
17TH ST E
119TH
AV
E E
SE 286TH ST
9TH ST SE
55TH PL S
SE 276TH PL
65TH AVE S
SE 295TH PL
G ST NE
27 TH ST SE
5TH AVE N
SKINNER RD
1
0
2
N
D
A
V
E
S
E
128TH AVE E
S 354TH ST
S 344TH ST
SE 364TH ST
SE 290TH ST
10TH ST SE
D ST SW
SE 280TH ST
2
1
1
T
H
A
V
E
E
NATHAN AVE SE
V ST SE
HI CREST DR
B PL NW
SE 294TH ST
S 285TH ST
6TH ST NW
146TH AVE SE
SE 293RD ST
PEA
R
L
A
V
E
S
E
3RD ST NW
126TH AVE SE
I
S
A
A
C
A
V
E
S
E
S 3 1 2 T H S T
ELM ST SE
CLAY ST
S 370TH ST
20TH ST E
52ND PL S
7TH ST E
19TH DR NE
SE 307TH PL
5 1 S T S T S E
10TH AVE N
S 364TH ST
140TH AVE SE
28TH ST SE
72 N D ST SE
15TH ST SE
13
3
R
D
A
V
E
S
E
10
8
T
H
A
VE
S
E
73RD ST SE
SE 295TH ST
26TH ST NE
S 366TH ST
SE 297TH ST
2
1
0
T
H
A
V
E
E
66TH ST SE
24TH ST NE
SE 296TH ST
SE 285TH ST
S 368TH ST
ALDER LN S
11
7
TH
A
V
E
S
E
U ST SE
19TH ST SE
6TH ST SE
110TH PL SE
A ST E
156TH AVE SE
21ST ST SE
R PL NE
117TH AVE E
105TH AVE SE
7TH ST
5TH ST NE
53
R
D A
V
E
S
HE
AT
H
E
R
A
V
E
S
E
F S
T N
E
112
TH PL
SE
51
ST
P
L
S
SE 292ND ST
D PL SE
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
123RD AVE E
63RD PL S
THORTON PL SW
2ND CT NW
1ST ST NE
129TH PL SE
6TH ST NE
3RD ST NE
O C
T
S
E
S 342ND ST
105TH AVE E
26TH ST NW
SE 321ST PL
114TH PL SE
RAMP
T
B
D
H ST NE
SR 167
SR 18
17TH ST SE
RAMP
RAMP
2ND ST SE
56TH AVE S
RAMP
TBD
SE 301ST ST
108TH AVE E
32ND ST E
RAMP
108TH AVE E
SE 282ND ST
SE 296TH ST
R A M P
SE 272ND ST
T B D
DRIVEWAY
D ST SE
21ST ST E
16TH ST E
SR 167
D
R
I
V
E
WAY
144
T
H
AV
E
S
E
1ST AVE N
SR 18
SR 167
DRIVEWAY
SR 167
T
B
D
SR 167
53RD AVE S
8TH ST E
D
RIV
E
W
A
Y
104TH AVE SE
SE 292ND ST
RAMP
S 277TH ST
SE 304TH ST
24TH ST E
8TH ST E
10
8
TH
A
VE
S
E
SE 274TH ST
12TH ST E
SR 18
SE 284TH ST
S R 1 8
148TH AVE SE
R A M P
9TH ST E
124TH AVE SE
R AM P
R
A
M
P
32ND ST E
72ND AVE
S
SE 272ND ST
TB
D
5 5 T H P L S
RAMP
SE 288TH ST
TBD
RAMP
SR 167
TBD
R
A
M
P
55TH AVE S
S 277TH ST
M ST NE
TBD
SR 167
R ST NW
V ST SE51ST AVE S
TBD
51ST AVE S
R A M P
RAMP
TBD
106TH AVE E
TBD
SE 282ND ST
200TH AVE E
R A M P
26TH ST NE
TBD
TBD
110TH AVE SE
SR 167
13TH ST E
8TH ST NE
5 1 S T S T S E
R ST NW
T
B
D
TBD
B
JJ
C
T
LS
OO
E
ZZ
V
H
A
M
AZ
I CCC
II
U EE
J
NN
K
S
FF
UU
AA
KK
HH
W
P
SS
YY
QQ
O
MM
RR
LL
DD
CC
N
L
GG
TT
PPP
PP
HV
D
G
AAA
ZZZ
F
I
NNN
Z R
YYY
X
WC
WW
BBB
DDD
BB
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 4,000 feet
December 2009
L E G E N D
Subbasins
Roadway
Water Body
Watercourse
Wetland
Auburn City Boundary
Surficial Geology
Qa
Qc
Qf
Qga
Qgd
Qgl
Qgo
Qgp
Qgp(s)
Qgp(st)
Qgpc
Qgt
Qls
Qp
Qvl(o)
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig4-3(geo).mxd
2,00002,0004,000
Feet [N
FIGURE 4-3
SURFACE GEOLOGY
IN THE VICINITY OF THE
CITY OF AUBURN
Geologic Unit Lithology
Qa Alluvium
Qc Continental sedimentary deposits or rocks
Qf Artificial fill, including modified land
Qga Advance continental glacial outwash, Fraser-age
Qgd Continental glacial drift, Fraser-age
Qgl Glaciolacustrine deposits, Fraser-age
Qgo Continental glacial outwash, Fraser-age
Qgp Continental glacial drift, pre-Fraser
Qgp(s)Continental glacial drift, pre-Frasier, Salmon Springs Drift
Qgp(st)Continental glacial drift, pre-Fraser, Stuck Drift
Qgpc Continental glacial drift, pre-Fraser, and nonglacial deposits
Qgt Continental glacial till, Fraser-age
Qls Mass-wasting deposits, mostly landslides
Qp Peat deposits
Qvl(o)Lahars
L a k e
T a p p s
B i g S o o s C r e e k
Mill Creek
R i v e r
G
r
e
e
n
R
i
ver
M
i l l
C
r e e k
Creek
Mill
G
r
e
e
n
R
i
v
e
r
G
r
e
e
n
River
W h i t e
G
r
e
e
n
R i v e r
Soosette
Creek
River
W
h i t
e
B o w m a n
C
r
e
e
k
W h i t e
R iv e r
R i v e r
White
Lake
M
u
l
l
e
n
S
l
o
u
g
h
Green
R iv e r
Lake
Meridian
W h i t e
S
R
1
6
7
S R 1 8
A ST SE
C ST SW
A
U
B
U
R
N
W
A
Y
S
B ST NW
I ST NE
AUBURN WAY N
R ST SE
132ND AVE SE
RA M P
WEST VALLEY HWY NW
M ST SE
8TH ST E
E MAIN ST
24TH ST E
124TH AVE SE
EAST VALLEY HWY SE
JOVITA BLVD
122ND AVE E
C ST NW
BUTTE AVE
S 384TH ST
110TH AVE E
15TH ST SW
SE 288TH ST
2ND ST E
C ST NE
SE 312TH ST
S 277TH ST
W MAIN ST
15TH ST NW
198TH AVE E
53RD ST SE
9TH ST E
29TH ST SE
GREEN VALLEY RD
1
7
9
T
H
A
V
E
SE 320TH ST
114TH AVE E
116TH AVE SE
EDWARDS RD E
LAKE TAPPS PKWY SE
41ST ST SE
WEST VALLEY HWY SW
S T U C K R I V E R D R
16TH ST E
K
E
R
S
E
Y
W
A
Y
S
E
147TH AVE SE
4TH ST E
18TH ST E
M ST NE
12TH ST E
SE 304TH ST
1
9
0
T
H
A
V
E
E
112TH AVE E
3RD AVE SE
ELLINGSON RD SW
37TH ST SE
PERIMETER RD
SE 272ND ST
4
6
T
H
P
L
S
8TH ST NE
182ND AVE E
37TH ST NW
ACADEMY DR SE
SE LAKE HOLM RD
22ND ST NE
L
A
K
E
L
A
N
D
H
I
L
L
S
W
A
Y
S
E
O R A V E TZ R D S E
VALENTI
NE AVE SE
C
U
T
O
F
F
51ST
AV
E S
SE 282ND ST
144TH AVE SE
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
55TH AVE S
1
8
5
T
H
A
V
E
E
214TH AVE E
D ST SE
1ST AVE SE
TACOMA BLVD
D ST NW
A ST NE
4TH ST SE
TBD
CELERY AVE
30TH ST NE
10
8
T
H AVE
EAST BLVD (BOEING)
112
T
H AVE SE
SE 316TH ST
148TH AVE SE
T
A
C
O
M
A
P
O
I
N
T
D
R
E
A
U
B
U
R
N
-
E
N
U
M
C
L
A
W
R
D
55TH ST SE
E
V
E
R
G
R
E
E
N
W
A
Y
S
E
EMERALD DOWNS DR NW
D ST NE
M ST NW
O ST NE
S
E
3
6
8
T
H
P
L
W ST NW
1
6
9
T
H
A
V
E
E
S 287TH ST
3RD AVE S
5TH AVE SW
E ST NE
37TH ST NE
142ND AVE E
S 316TH ST
H
A
R
V
E
Y
R
D
S
C
E
N
I
C
D
R
S
E
H ST NW
M
A
I
N
S
T
S 292ND ST
WEST BLVD (BOEING)
44TH ST NW
3RD AVE SW
118TH AVE E
10TH ST NE
CLAY ST NW
4TH AVE SW
148TH AVE E
7TH ST SE
137TH AVE E
2
6
T
H
S
T
E
136TH AVE E
SE 310TH ST
S 3RD AVE
THORTON AVE SW
2
0
0
T
H
A
V
E
E
R I V E R D R
BOUNDARY BLVD
L E A H I L L R D S E
32ND ST E
118TH AVE SE
58TH AVE S
ALGONA BLVD N
104TH AVE SE
S 372ND ST
J ST NE
ROY RD SW
4TH ST NE
PACIFIC AVE S
110TH AVE SE
14TH ST NE
D
R
I
V
E
W
A
Y
SE 281ST ST
126TH AVE E
5TH ST SE
72ND AVE S
56TH PL S
25TH ST E
BRIDGET AVE SE
57TH AVE S
S 328TH ST
DOGWOOD ST SE
2ND AVE SW
8TH ST SE
S 279TH ST
L
S
T
S
E
T ST SE
F
ST
S
E
FR O NTA G E RD
C
O
T
TA
G
E
R
D
E
FO
ST
E
R
A
V
E
S
E
52ND AVE S
SE 274TH S T
1ST ST E
166
TH
A
V
E
E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
4 9TH S T NE
S 362ND ST
NO
R
M
AN
A
V
E
S
E
I
S
T
N
W
32ND PL NE
54
TH
AV
E
S
A ST SW
57TH PL S
U
S
T
N
W
7
8
T
H
A
V
E
S
3RD ST E
D
E
E
R
I
S
L
A
N
D
D
R
E
135
T
H
A
V
E
S
E
4 7 T H S T S E
2
0
4
T
H
A
V
E
E
28TH ST NE
8
6
T
H
A
V
E
S
S 356TH ST
J
ST
SE
R ST NW
27TH ST E
15TH ST E
28TH ST E
MIL
I
T
AR
Y
R
D
S
13TH ST E
K
ST
S
E
OLIVE AVE SE
10TH ST E
10
8
T
H AVE E
31ST ST NE
SE 323RD PL
54TH PL S
B ST SE
WYMAN DR
26TH ST SE
S 336TH ST
ST PAUL BLVD
S 340TH ST
C
ST
S
E
B ST NE
32ND ST SE
S 300TH S T
1ST AVE S
36TH ST SE
ELM LN
SE 301ST ST
2
0
8
T
H
A
V
E
E
SE 287TH ST
V ST NW
2ND ST SE
23RD ST SE
4TH AVE S
3RD ST SE
QUINCY AVE SE
29TH ST NW
21ST ST NE
1
5
6
T
H
A
V
E
E
HEMLOCK ST SE
1
8
4
T
H
C
T
E
5
6
T
H
A
V
E
S
10
6T
H
A
V
E
E
SE 298TH PL30TH ST NW
30TH ST SE
S 318TH ST
24TH ST SE
2ND AVE S
14TH ST E
H ST NE
LUND RD SW
S 324TH ST
PIK
E
S
T
NW
21ST ST E
31ST ST E
42ND ST NW
6TH AVE SW
17TH ST E
119TH
AV
E E
SE 286TH ST
9TH ST SE
55TH PL S
SE 276TH PL
65TH AVE S
SE 295TH PL
G ST NE
27 TH ST SE
5TH AVE N
SKINNER RD
1
0
2
N
D
A
V
E
S
E
128TH AVE E
S 354TH ST
S 344TH ST
SE 364TH ST
SE 290TH ST
10TH ST SE
D ST SW
SE 280TH ST
2
1
1
T
H
A
V
E
E
NATHAN AVE SE
V ST SE
HI CREST DR
B PL NW
SE 294TH ST
S 285TH ST
6TH ST NW
146TH AVE SE
SE 293RD ST
PEA
R
L
A
V
E
S
E
3RD ST NW
126TH AVE SE
I
S
A
A
C
A
V
E
S
E
S 3 1 2 T H S T
ELM ST SE
CLAY ST
S 370TH ST
20TH ST E
52ND PL S
7TH ST E
19TH DR NE
SE 307TH PL
5 1 S T S T S E
10TH AVE N
S 364TH ST
140TH AVE SE
28TH ST SE
72 N D ST SE
15TH ST SE
13
3
R
D
A
V
E
S
E
10
8
T
H
A
VE
S
E
73RD ST SE
SE 295TH ST
26TH ST NE
S 366TH ST
SE 297TH ST
2
1
0
T
H
A
V
E
E
66TH ST SE
24TH ST NE
SE 296TH ST
SE 285TH ST
S 368TH ST
ALDER LN S
11
7
TH
A
V
E
S
E
U ST SE
19TH ST SE
6TH ST SE
110TH PL SE
A ST E
156TH AVE SE
21ST ST SE
R PL NE
117TH AVE E
105TH AVE SE
7TH ST
5TH ST NE
53
R
D A
V
E
S
HE
AT
H
E
R
A
V
E
S
E
F S
T N
E
112
TH PL
SE
51
ST
P
L
S
SE 292ND ST
D PL SE
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
123RD AVE E
63RD PL S
THORTON PL SW
2ND CT NW
1ST ST NE
129TH PL SE
6TH ST NE
3RD ST NE
O C
T
S
E
S 342ND ST
105TH AVE E
26TH ST NW
SE 321ST PL
114TH PL SE
RAMP
T
B
D
H ST NE
SR 167
SR 18
17TH ST SE
RAMP
RAMP
2ND ST SE
56TH AVE S
RAMP
TBD
SE 301ST ST
108TH AVE E
32ND ST E
RAMP
108TH AVE E
SE 282ND ST
SE 296TH ST
R A M P
SE 272ND ST
T B D
DRIVEWAY
D ST SE
21ST ST E
16TH ST E
SR 167
D
R
I
V
E
WAY
144
T
H
AV
E
S
E
1ST AVE N
SR 18
SR 167
DRIVEWAY
SR 167
T
B
D
SR 167
53RD AVE S
8TH ST E
D
RIV
E
W
A
Y
104TH AVE SE
SE 292ND ST
RAMP
S 277TH ST
SE 304TH ST
24TH ST E
8TH ST E
10
8
TH
A
VE
S
E
SE 274TH ST
12TH ST E
SR 18
SE 284TH ST
S R 1 8
148TH AVE SE
R A M P
9TH ST E
124TH AVE SE
R AM P
R
A
M
P
32ND ST E
72ND AVE
S
SE 272ND ST
TB
D
5 5 T H P L S
RAMP
SE 288TH ST
TBD
RAMP
SR 167
TBD
R
A
M
P
55TH AVE S
S 277TH ST
M ST NE
TBD
SR 167
R ST NW
V ST SE51ST AVE S
TBD
51ST AVE S
R A M P
RAMP
TBD
106TH AVE E
TBD
SE 282ND ST
200TH AVE E
R A M P
26TH ST NE
TBD
TBD
110TH AVE SE
SR 167
13TH ST E
8TH ST NE
5 1 S T S T S E
R ST NW
T
B
D
TBD
B
JJ
C
T
LS
OO
E
ZZ
V
H
A
M
AZ
I CCC
II
U EE
J
NN
K
S
FF
UU
AA
KK
HH
W
P
SS
YY
QQ
O
MM
RR
LL
DD
CC
N
L
GG
TT
PPP
PP
HV
D
G
AAA
ZZZ
F
I
NNN
Z R
YYY
X
WC
WW
BBB
DDD
BB
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 4,000 feet
December 2009
L E G E N D
Roadway
Subbasins
Auburn City Boundary
Hydrologic Soil Group
Type A
Type B
Type C
Type D
Water/Pits
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig4-4(soils2).mxd
2,00002,0004,000
Feet [N
FIGURE 4-4
HYDROLOGIC SOIL GROUPS
IN THE VICINITY OF THE
CITY OF AUBURN
Group A is sand, loamy sand, or sandy loam types of soils. It has low runoff
potential and high infiltration rates even when thoroughly wetted. It consists
chiefly of deep, well to excessively drained sands or gravels and has a high
rate of water transmission.
Group B is silt loam or loam. It has a moderate infiltration rate when
thoroughly wetted and consists chiefly of moderately deep to deep, moderately
well to well drained soils with moderately fine to moderately coarse textures.
Group C soils are sandy clay loam. It has low infiltration rates when thoroughly
wetted and consists chiefly of soils with a layer that impedes downward
movement of water and soils with moderately fine to fine structure.
Group D soils are clay loam, silty clay loam, sandy clay, silty clay, or clay. It
has very low infiltration rates when thoroughly wetted and consists chiefly of
clay soils with a high swelling potential, soils with a permanent high water
table, soils with a claypan or clay layer at or near the surface, and shallow soils
over nearly impervious material.
L a k e
T a p p s
B i g S o o s C r e e k
Mill Creek
R i v e r
G
r
e
e
n
R
i
ver
M
i l l
C
r e e k
Creek
Mill
G
r
e
e
n
R
i
v
e
r
G
r
e
e
n
River
W h i t e
G
r
e
e
n
R i v e r
Soosette
Creek
River
W
h i t
e
B o w m a n
C
r
e
e
k
W h i t e
R iv e r
R i v e r
White
Lake
M
u
l
l
e
n
S
l
o
u
g
h
Green
River
Lake
Meridian
W h i t e
S
R
1
6
7
A ST SE
C ST SW
A
U
B
U
R
N
W
A
Y
S
B ST NW
I ST NE
AUBURN WAY N
S R 1 8
R ST SE
132ND AVE SE
RA M P
WEST VALLEY HWY NW
M ST SE
8TH ST E
E MAIN ST
24TH ST E
124TH AVE SE
J O V I T A B L V D
EAST VALLEY HWY SE
122ND AVE E
BUTTE AVE
S 384TH ST
110TH AVE E
15TH ST SW
SE 288TH ST
2ND ST E
C ST NE
SE 312TH ST
S 277TH ST
W MAIN ST
15TH ST NW
C ST NW
198TH AVE E
53RD ST SE
9TH ST E
29TH ST SE
GREEN VALLEY RD
1
7
9
T
H
A
V
E
SE 320TH ST
114TH AVE E
116TH AVE SE
EDWARDS RD E
LAKE TAPPS PKWY SE
41ST ST SE
WEST VALLEY HWY SW
S T U C K R I V E R D R
16TH ST E
K
E
R
S
E
Y
W
A
Y
S
E
147TH AVE SE
4TH ST E
18TH ST E
M ST NE
12TH ST E
SE 304TH ST
1
9
0
T
H
A
V
E
E
112TH AVE E
3RD AVE SE
ELLINGSON RD SW
37TH ST SE
PERIMETER RD
SE 272ND ST
4
6
T
H
P
L
S
8TH ST NE
182ND AVE E
37TH ST NW
ACADEMY DR SE
SE LAKE HOLM RD
22ND ST NE
L
A
K
E
L
A
N
D
H
I
L
L
S
W
A
Y
S
E
O R A V E TZ R D S E
VALENTI
NE AVE SE
C
U
T
O
F
F
51ST
AV
E S
SE 282ND ST
144TH AVE SE
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
55TH AVE S
1
8
5
T
H
A
V
E
E
214TH AVE E
D ST SE
1ST AVE SE
TACOMA BLVD
D ST NW
A ST NE
4TH ST SE
TBD
CELERY AVE
30TH ST NE
10
8T
H AVE
EAST BLVD (BOEING)
112
T
H AVE SE
SE 316TH ST
148TH AVE SE
T
A
C
O
M
A
P
O
I
N
T
D
R
E
55TH ST SE
A
U
B
U
R
N
-
E
N
U
M
C
L
A
W
R
D
E
V
E
R
G
R
E
E
N
W
A
Y
S
E
D ST NE
M ST NW
O ST NE
S
E
3
6
8
T
H
P
L
W ST NW
1
6
9
T
H
A
V
E
E
S 287TH ST
3RD AVE S
5TH AVE SW
E ST NE
37TH ST NE
142ND AVE E
S 316TH ST
H
A
R
V
E
Y
R
D
S
C
E
N
I
C
D
R
S
E
H ST NW
M
A
I
N
S
T
S 292ND ST
WEST BLVD (BOEING)
44TH ST NW
3RD AVE SW
118TH AVE E
10TH ST NE
CLAY ST NW
4TH AVE SW
148TH AVE E
7TH ST SE
137TH AVE E
2
6
T
H
S
T
E
136TH AVE E
SE 310TH ST
S 3RD AVE
THORTON AVE SW
2
0
0
T
H
A
V
E
E
17TH ST E
R I V E R D R
BOUNDARY BLVD
L E A H I L L R D S E
32ND ST E
118TH AVE SE
58TH AVE S
ALGONA BLVD N
104TH AVE SE
S 372ND ST
J ST NE
ROY RD SW
4TH ST NE
PACIFIC AVE S
110TH AVE SE
14TH ST NE
DRIVEWAY
SE 281ST ST
126TH AVE E
5TH ST SE
72ND AVE S
56TH PL S
25TH ST E
BRIDGET AVE SE
57TH AVE S
S 328TH ST
DOGWOOD ST SE
2ND AVE SW
8TH ST SE
S 279TH ST
L
S
T
S
E
T ST SE
F
ST
S
E
FR O NTAG E R D
C
O
T
TA
G
E
R
D
E
FO
ST
E
R
A
V
E
S
E
52ND AVE S
SE 274TH S T
166
TH
A
V
E
E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
4 9TH S T NE
S 362ND ST
I
S
T
N
W
32ND PL NE
54
TH
AV
E
S
A ST SW
57TH PL S
U
S
T
N
W
7
8
T
H
A
V
E
S
3RD ST E
D
E
E
R
I
S
L
A
N
D
D
R
E
13
5
T
H
A
V
E
S
E
4 7 T H S T S E
2
0
4
T
H
A
V
E
E
28TH ST NE
8
6
T
H
A
V
E
S
S 356TH ST
J
ST
SE
R ST NW
27TH ST E
15TH ST E
28TH ST E
MIL
I
T
AR
Y
R
D
S
13TH ST E
K
ST
S
E
OLIVE AVE SE
10TH ST E
10
8T
H AVE E
31ST ST NE
SE 323RD PL
54TH PL S
B ST SE
WYMAN DR
26TH ST SE
S 336TH ST
ST PAUL BLVD
S 340TH ST
C
ST
S
E
B ST NE
32ND ST SE
S 300TH S T
1ST AVE S
36TH ST SE
ELM LN
SE 301ST ST
2
0
8
T
H
A
V
E
E
SE 287TH ST
V ST NW
2ND ST SE
23RD ST SE
4TH AVE S
3RD ST SE
QUINCY AVE SE
21ST ST NE
1
5
6
T
H
A
V
E
E
140TH AVE E
HEMLOCK ST SE
1
8
4
T
H
C
T
E
5
6
T
H
A
V
E
S
106TH AVE E
SE 298TH PL
30TH ST SE
S 318TH ST
24TH ST SE
2ND AVE S
14TH ST E
H ST NE
LUND RD SW
S 324TH ST
PIK
E
S
T
NW
21ST ST E
31ST ST E
42ND ST NW
6TH AVE SW
119TH
AV
E E
SE 286TH ST
9TH ST SE
55TH PL S
SE 276TH PL
65TH AVE S
SE 295TH PL
G ST NE
2 7T H ST SE
5TH AVE N
SKINNER RD
128TH AVE E
S 354TH ST
S 344TH ST
SE 364TH ST
SE 290TH ST
10TH ST SE
D ST SW
SE 280TH ST
2
1
1
T
H
A
V
E
E
NATHAN AVE SE
V ST SE
1
0
4
T
H
P
L
S
E
HI CREST DR
B PL NW
SE 294TH ST
72 N D ST SE
S 285TH ST
6TH ST NW
146TH AVE SE
SE 293RD ST
3RD ST NW
126TH AVE SE
I
S
A
A
C
A
V
E
S
E
S 3 1 2 T H S T
ELM ST SE
CLAY ST
S 370TH ST
20TH ST E
52ND PL S
7TH ST E
19TH DR NE
SE 307TH PL
5 1 S T S T S E
10TH AVE N
S 364TH ST
140TH AVE SE
28TH ST SE
15TH ST SE
13
3
R
D
A
V
E
S
E
10
8
T
H
A
VE
S
E
73RD ST SE
SE 295TH ST
26TH ST NE
S 366TH ST
SE 297TH ST
2
1
0
T
H
A
V
E
E
66TH ST SE
24TH ST NE
SE 296TH ST
SE 285TH ST
S 368TH ST
ALDER LN S
11
7
TH
A
V
E
S
E
U ST SE
19TH ST SE
6TH ST SE
110TH PL SE
A S T E WAR
D
A
VE
S
E
156TH AVE SE
21ST ST SE
R PL NE
117TH AVE E
105TH AVE SE
7TH ST
5TH ST NE
53
R
D A
V
E
S
HE
AT
H
E
R
A
V
E
S
E
F S
T NE
112
TH PL SE
51
ST
P
L
S
SE 292ND ST
D PL SE
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
123RD AVE E
63RD PL S
2ND CT NW
1ST ST NE
R ST NE
129TH PL SE
O C
T
S
E
S 342ND ST
105TH AVE E
26TH ST NW
5TH ST E
SE 321ST PL
114TH PL SE
110TH AVE SE
108TH AVE E
32ND ST E
TBD
144
T
H
AV
E
S
E
SE 292ND ST
16TH ST E
R A M P
16TH ST E
R A M P
RAMP
12TH ST E
TBD
TBD
106TH AVE E
26TH ST NE
RAMP
SE 296TH ST
SR 167
RAMP
SE 282ND ST
S R 1 8
R A M P
T
B
D
SE 288TH ST
SE 272ND ST
SR 167
105TH AVE E
R
A
M
P
53RD AVE S
R
A
M
P
TBD
55TH AVE S
13TH ST E
21ST ST E
56TH AVE S
SE 301ST ST
10
8T
H
A
VE
S
E
R ST NW
SR 167
RAMP
SR 167
R A M P
SR 167
200TH AVE E
TBD
124TH AVE SE
17TH ST SE
SE 274TH ST
SR 167
D
RIV
E
W
A
Y
S 277TH ST
T B D
148TH AVE SE
51ST AVE S TBD
R A M P
D ST SE
5 1 S T S T S E
SE 284TH ST
9TH ST E
5 5 T H P L S
R ST NW
2ND ST SE
R
A
M
P
RAMP
RAMP
T
B
D
SR 18
TBD
SR 18
8TH ST NE
142ND AVE E
D
R
I
V
E
WA
Y
1ST AVE N
C ST N
W
H ST NE
TBD
8TH ST E
SR 167
51ST AVE S
V ST SE
24TH ST E
RAMP
R A M P
RAMP
TBD
8TH ST E
TBD
SR 167
DRIVEWAY
SE 272ND ST
SE 282ND ST
S 277TH ST
M ST NE
T
B
D
32ND ST E
SR 18
TBD
104TH AVE SE
B
JJ
C
T
LS
OO
E
ZZ
V
H
A
M
AZ
I CCC
II
U
EE
J
NN
K
S
FF
UU
AA
KK
HH
W
P
SS
YY
QQ
O
MM
RR
LL
DD
CC
N
L
GG
TT
PP
HV
WW
D
G
AAA
ZZZ
F
I
NNN
PPP
Z R
YYY
X
WC
BBB
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 4,000 feet
December 2009
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig4-5(landuse).mxd
2,00002,0004,000
Feet [N
FIGURE 4-5
LAND USE DESIGNATIONS
FOR THE CITY OF AUBURN
(COMP PLAN, 2008)
L E G E N D
Roadway
Watercourse
Hydrography
Subbasins
Auburn City Boundary
Special Land Use Area
Existing Land Use (Comp Plan, 2008)
RURAL
SINGLE-FAMILY RESIDENTIAL
MODERATE DENSITY RESIDENTIAL
HIGH DENSITY RESIDENTIAL
OFFICE RESIDENTIAL
NEIGHBORHOOD COMMERCIAL
LIGHT COMMERCIAL
HEAVY COMMERCIAL
DOWNTOWN
LIGHT INDUSTRIAL
HEAVY INDUSTRIAL
PUBLIC AND QUASI-PUBLIC
OPEN SPACE
L a k e
T a p p s
B i g S o o s C r e e k
Mill Creek
R i v e r
G
r
e
e
n
R
i
ver
M
i l l
C
r e e k
Creek
Mill
G
r
e
e
n
R
i
v
e
r
G
r
e
e
n
River
W h i t e
G
r
e
e
n
R i v e r
Soosette
Creek
River
W
h i t
e
B o w m a n
C
r
e
e
k
W h i t e
R iv e r
R i v e r
White
Lake
M
u
l
l
e
n
S
l
o
u
g
h
Green
R iv e r
Lake
Meridian
W h i t e
S
R
1
6
7
S R 1 8
A ST SE
C ST SW
A
U
B
U
R
N
W
A
Y
S
B ST NW
I ST NE
AUBURN WAY N
R ST SE
132ND AVE SE
RA M P
WEST VALLEY HWY NW
M ST SE
8TH ST E
E MAIN ST
24TH ST E
124TH AVE SE
EAST VALLEY HWY SE
JOVITA BLVD
122ND AVE E
BUTTE AVE
S 384TH ST
110TH AVE E
15TH ST SW
SE 288TH ST
2ND ST E
C ST NE
SE 312TH ST
S 277TH ST
W MAIN ST
15TH ST NW
C ST NW
198TH AVE E
53RD ST SE
9TH ST E
29TH ST SE
GREEN VALLEY RD
1
7
9
T
H
A
V
E
SE 320TH ST
114TH AVE E
116TH AVE SE
EDWARDS RD E
LAKE TAPPS PKWY SE
41ST ST SE
WEST VALLEY HWY SW
S T U C K R I V E R D R
16TH ST E
K
E
R
S
E
Y
W
A
Y
S
E
147TH AVE SE
4TH ST E
18TH ST E
M ST NE
12TH ST E
SE 304TH ST
ELLINGSON RD SW
37TH ST SE
PERIMETER RD
SE 272ND ST
4
6
T
H
P
L
S
8TH ST NE
182ND AVE
E
37TH ST NW
ACADEMY DR SE
SE LAKE HOLM RD
22ND ST NE
L
A
K
E
L
A
N
D
H
I
L
L
S
W
A
Y
S
E
O R A V E TZ R D S E
VALENTI
NE AVE SE
C
U
T
O
F
F
51ST
AV
E S
SE 282ND ST
144TH AVE SE
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
55TH AVE S
1
8
5
T
H
A
V
E
E
214TH AVE E
D ST SE
1ST AVE SE
TACOMA BLVD
D ST NW
A ST NE
4TH ST SE
TBD
CELERY AVE
30TH ST NE
10
8T
H AVE
EAST BLVD (BOEING)
112
T
H AVE SE
SE 316TH ST
148TH AVE SE
T
A
C
O
M
A
P
O
I
N
T
D
R
E
A
U
B
U
R
N
-
E
N
U
M
C
L
A
W
R
D
55TH ST SE
E
V
E
R
G
R
E
E
N
W
A
Y
S
E
EMERALD
DOWNS DR NW
D ST NE
M ST NW
O ST NE
S
E
3
6
8
T
H
P
L
W ST NW
1
6
9
T
H
A
V
E
E
S 287TH ST
5TH AVE SW
142ND AVE E
S 316TH ST
S
C
E
N
I
C
D
R
S
E
H ST NW
M
A
I
N
S
T
S 292ND ST
44TH ST NW
3RD AVE SW
118TH AVE E
148TH AVE E
7TH ST SE
137TH AVE E
2 6 T H S T E
S 3RD AVE
THORTON AVE SW
2
0
0
T
H
A
V
E
E
R I V E R D R
BOUNDARY BLVD
L E A H I L L R D S E
32ND ST E
118TH AVE SE
58TH AVE S
104TH AVE SE
S 372ND ST
J ST NE
4TH ST NE
110TH AVE SE
D
R
I
V
E
W
A
Y
SE 281ST ST
126TH AVE E
72ND AVE S
56TH PL S
25TH ST E
BRIDGET AVE SE
57TH AVE S
DOGWOOD ST SE
S 279TH ST
L
S
T
S
E
T ST SE
F
ST
S
E
C
O
T
TA
G
E
R
D
E
52ND AVE S
SE 274TH ST
1ST ST E
166
TH
A
V
E
E
1ST AVE N
SE 299TH ST
SE 284TH ST
4 9TH S T NE
I
S
T
N
W
54TH AVE S
A ST SW
ALGONA BLVD S
7
8
T
H
A
V
E
S
3RD ST E
D
E
E
R
I
S
L
A
N
D
D
R
E
135
T
H
A
V
E
S
E
8
6
T
H
A
V
E
S
R ST NW
MILL POND DR SE
15TH ST E
28TH ST E
MIL
I
T
AR
Y
R
D
S
OLIVE AVE SE
10TH ST E
10
8T
H AVE E
SE 323RD PL
54TH PL S
B ST SE
WYMAN DR
26TH ST SE
S 336TH ST
S 340TH ST
B ST NE
32ND ST SE
S 300TH S T
SE 301ST ST
SE 287TH ST
V ST NW
QUINCY AVE SE
21ST ST NE
1
5
6
T
H
A
V
E
E
HEMLOCK ST SE
5
6
T
H
A
V
E
S
10
6T
H
A
V
E
E
LUND RD SW
42ND ST NW
32ND PL NE
17TH ST E
119TH
AV
E E
SE 276TH PL
65TH AVE S
SE 295TH PL
G ST NE
O ST SE
1
0
2
N
D
A
V
E
S
E
S 344TH ST
SE 364TH ST
SE 290TH ST
SE 280TH ST
SE 294TH ST
146TH AVE SE
V CT SE
126TH AVE SE
S 3 1 2 T H S T
SE 307TH PL
140TH AVE SE
11TH ST NE
72 N D ST SE
13
3
R
D
A
V
E
S
E
10
8
T
H
A
VE
S
E
SE 295TH ST
S 319TH ST
26TH ST NE
2
1
0
T
H
A
V
E
E
SE 296TH ST
SE 285TH ST
11
7
TH
A
V
E
S
E
6TH ST SE
A ST E
156TH AVE SE
11
7
T
H
A
VE
E
7TH ST
HE
AT
H
E
R
A
V
E
S
E
F ST N
E
112TH PL SE
51
ST
P
L
S
SE 292ND ST
114TH AVE SE
SE 272ND PL
123RD AVE E
THORTON PL SW
1ST ST NE
HOMER AVE SE
O C
T
S
E
28
TH
PL
S
E
R A M P
SR 18
SR 167
RAMP
SR 167
106TH AVE E
SE 284TH ST
124TH AVE SE
RAMP
R A M P
R
A
M
P
RAMP
TBD
B
S
T
S
E
S R 1 8
SE 296TH ST
RAMP
T
B
D
51ST AVE S
SR 167
9TH ST E
RAMP
RAMP
DRIVEWAY
RAMP
S 277TH ST
SR 167
51ST AVE S
TBD
TBD
T
B
D
R A M P
SE 288TH ST
R
A
M
P
SR 167
D
RIV
E
W
A
Y
SR 167
R ST NW
SR 18
SR 167
TBD
TBD
TBD
SR 167
32ND ST E
C ST N
W
16TH ST E
144TH AVE SE
TBD
B
C
JJ
T
E
OO
LS
V
ZZ
H
A
M
AZI CCC
II
U EE
NN
J
S
K
FF
UU
HH
W
AA
KK
P
SS
YY
QQ D
O
MM
RR
DD
G
CC
N
LL
AAA
ZZZ
L
GG
F
TT
NNN
PPP
PP
Z R
HV
X
WW
I
YYY
WC
BBB
DDD
BB
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 4,000 feet
December 2009
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig4-6(priorities).mxd
2,00002,0004,000
Feet [N
FIGURE 4-6
DRAINAGE INFRASTRUCTURE
SYSTEM INVENTORY
SUB-BASIN PRIORITIES
L E G E N D
Roadway
Watercourse
Water Body
Wetland
Subbasins
Auburn City Boundary
Inventory Priority
High
Medium
Low
Other (Not Inventoried)
NOTES:
Sub-basin delineations are based on the 2002 Drainage Plan and are used for reference.
Gray areas appearing as gaps between sub-basins are areas adjacent to rivers that drain directly to those rivers.
L a k e
T a p p s
B i g S o o s C r e e k
Mill Creek
R i v e r
G
r
e
e
n
R
i
ver
M
i l l
C
r e e k
Creek
Mill
G
r
e
e
n
R
i
v
e
r
G
r
e
e
n
River
W h i t e
G
r
e
e
n
R i v e r
Soosette
Creek
River
W
h i t
e
B o w m a n
C
r
e
e
k
W h i t e
R iv e r
R i v e r
White
Lake
M
u
l
l
e
n
S
l
o
u
g
h
Green
R iv e r
Lake
Meridian
W h i t e
"
P Basin PS
"
A Street PS
"
Auburn Way South PS
"
Emerald PS
"
Brannan Park PS
"
White River PS
S
R
1
6
7
S R 1 8
A ST SE
C ST SW
A
U
B
U
R
N
W
A
Y
S
B ST NW
I ST NE
AUBURN WAY N
R ST SE
132ND AVE SE
RA M P
WEST VALLEY HWY NW
M ST SE
8TH ST E
E MAIN ST
24TH ST E
124TH AVE SE
EAST VALLEY HWY SE
JOVITA BLVD
122ND AVE E
BUTTE AVE
S 384TH ST
110TH AVE E
15TH ST SW
SE 288TH ST
2ND ST E
C ST NE
SE 312TH ST
S 277TH ST
W MAIN ST
15TH ST NW
C ST NW
198TH AVE E
53RD ST SE
9TH ST E
29TH ST SE
GREEN VALLEY RD
1
7
9
T
H
A
V
E
SE 320TH ST
114TH AVE E
116TH AVE SE
EDWARDS RD E
LAKE TAPPS PKWY SE
41ST ST SE
WEST VALLEY HWY SW
S T U C K R I V E R D R
16TH ST E
K
E
R
S
E
Y
W
A
Y
S
E
147TH AVE SE
4TH ST E
18TH ST E
M ST NE
12TH ST E
SE 304TH ST
1
9
0
T
H
A
V
E
E
112TH AVE E
3RD AVE SE
ELLINGSON RD SW
37TH ST SE
PERIMETER RD
SE 272ND ST
4
6
T
H
P
L
S
8TH ST NE
182ND AVE E
37TH ST NW
ACADEMY DR SE
SE LAKE HOLM RD
22ND ST NE
L
A
K
E
L
A
N
D
H
I
L
L
S
W
A
Y
S
E
O R A V E TZ R D S E
VALENTI
NE AVE SE
C
U
T
O
F
F
51ST
AV
E S
SE 282ND ST
144TH AVE SE
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
55TH AVE S
1
8
5
T
H
A
V
E
E
214TH AVE E
D ST SE
1ST AVE SE
TACOMA BLVD
D ST NW
A ST NE
4TH ST SE
TBD
CELERY AVE
30TH ST NE
10
8T
H AVE
EAST BLVD (BOEING)
112
T
H AVE SE
SE 316TH ST
148TH AVE SE
T
A
C
O
M
A
P
O
I
N
T
D
R
E
A
U
B
U
R
N
-
E
N
U
M
C
L
A
W
R
D
55TH ST SE
E
V
E
R
G
R
E
E
N
W
A
Y
S
E
EMERALD DOWNS DR NW
D ST NE
M ST NW
O ST NE
S
E
3
6
8
T
H
P
L
W ST NW
1
6
9
T
H
A
V
E
E
S 287TH ST
3RD AVE S
5TH AVE SW
E ST NE
37TH ST NE
142ND AVE E
S 316TH ST
H
A
R
V
E
Y
R
D
S
C
E
N
I
C
D
R
S
E
H ST NW
M
A
I
N
S
T
S 292ND ST
WEST BLVD (BOEING)
44TH ST NW
3RD AVE SW
118TH AVE E
10TH ST NE
CLAY ST NW
4TH AVE SW
148TH AVE E
7TH ST SE
137TH AVE E
2
6
T
H
S
T
E
136TH AVE E
SE 310TH ST
S 3RD AVE
THORTON AVE SW
2
0
0
T
H
A
V
E
E
R I V E R D R
BOUNDARY BLVD
L E A H I L L R D S E
32ND ST E
118TH AVE SE
58TH AVE S
ALGONA BLVD N
104TH AVE SE
S 372ND ST
J ST NE
ROY RD SW
4TH ST NE
PACIFIC AVE S
110TH AVE SE
14TH ST NE
D
R
I
V
E
W
A
Y
SE 281ST ST
126TH AVE E
5TH ST SE
72ND AVE S
56TH PL S
25TH ST E
BRIDGET AVE SE
57TH AVE S
S 328TH ST
DOGWOOD ST SE
2ND AVE SW
8TH ST SE
S 279TH ST
L
S
T
S
E
T ST SE
F
ST
S
E
FR O NTA G E RD
C
O
T
TA
G
E
R
D
E
FO
ST
E
R
A
V
E
S
E
52ND AVE S
SE 274TH S T
1ST ST E
166
TH
A
V
E
E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
4 9TH S T NE
S 362ND ST
NO
R
M
AN
A
V
E
S
E
I
S
T
N
W
54
TH
AV
E
S
A ST SW
57TH PL S
U
S
T
N
W
32ND ST NE
7
8
T
H
A
V
E
S
3RD ST E
D
E
E
R
I
S
L
A
N
D
D
R
E
135
T
H
A
V
E
S
E
4 7 T H S T S E
2
0
4
T
H
A
V
E
E
28TH ST NE
8
6
T
H
A
V
E
S
S 356TH ST
J
ST
SE
R ST NW
27TH ST E
15TH ST E
28TH ST E
MIL
I
T
AR
Y
R
D
S
13TH ST E
K
ST
S
E
OLIVE AVE SE
10TH ST E
10
8T
H AVE E
SE 323RD PL
54TH PL S
B ST SE
WYMAN DR
26TH ST SE
S 336TH ST
ST PAUL BLVD
S 340TH ST
C
ST
S
E
B ST NE
32ND ST SE
S 300TH S T
1ST AVE S
36TH ST SE
ELM LN
SE 301ST ST
2
0
8
T
H
A
V
E
E
SE 287TH ST
V ST NW
2ND ST SE
23RD ST SE
4TH AVE S
3RD ST SE
QUINCY AVE SE
29TH ST NW
21ST ST NE
1
5
6
T
H
A
V
E
E
HEMLOCK ST SE
1
8
4
T
H
C
T
E
5
6
T
H
A
V
E
S
10
6T
H
A
V
E
E
SE 298TH PL30TH ST NW
30TH ST SE
S 318TH ST
24TH ST SE
2ND AVE S
14TH ST E
H ST NE
LUND RD SW
S 324TH ST
PIK
E
S
T
NW
21ST ST E
31ST ST E
42ND ST NW
6TH AVE SW
17TH ST E
119TH
AV
E E
SE 286TH ST
9TH ST SE
55TH PL S
SE 276TH PL
65TH AVE S
SE 295TH PL
G ST NE
27 TH ST SE
5TH AVE N
SKINNER RD
1
0
2
N
D
A
V
E
S
E
128TH AVE E
S 354TH ST
S 344TH ST
SE 364TH ST
SE 290TH ST
10TH ST SE
D ST SW
SE 280TH ST
2
1
1
T
H
A
V
E
E
NATHAN AVE SE
V ST SE
HI CREST DR
B PL NW
SE 294TH ST
S 285TH ST
6TH ST NW
146TH AVE SE
SE 293RD ST
PEA
R
L
A
V
E
S
E
3RD ST NW
126TH AVE SE
I
S
A
A
C
A
V
E
S
E
S 3 1 2 T H S T
ELM ST SE
CLAY ST
S 370TH ST
20TH ST E
52ND PL S
7TH ST E
19TH DR NE
SE 307TH PL
5 1 S T S T S E
10TH AVE N
S 364TH ST
140TH AVE SE
28TH ST SE
72 N D ST SE
15TH ST SE
13
3
R
D
A
V
E
S
E
10
8
T
H
A
VE
S
E
73RD ST SE
SE 295TH ST
26TH ST NE
S 366TH ST
SE 297TH ST
2
1
0
T
H
A
V
E
E
66TH ST SE
24TH ST NE
SE 296TH ST
SE 285TH ST
S 368TH ST
ALDER LN S
11
7
TH
A
V
E
S
E
U ST SE
19TH ST SE
6TH ST SE
110TH PL SE
A ST E
156TH AVE SE
21ST ST SE
R PL NE
117TH AVE E
105TH AVE SE
7TH ST
5TH ST NE
53
R
D A
V
E
S
HE
AT
H
E
R
A
V
E
S
E
F ST N
E
11
2T
H
PL SE
51
ST
P
L
S
SE 292ND ST
D PL SE
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
123RD AVE E
63RD PL S
THORTON PL SW
2ND CT NW
1ST ST NE
129TH PL SE
6TH ST NE
3RD ST NE
O C
T
S
E
S 342ND ST
105TH AVE E
26TH ST NW
SE 321ST PL
114TH PL SE
53RD AVE S
TB
D
118TH AVE SE
148TH AVE SE
RAMP
SE 296TH ST
32ND ST E
RAMP
106TH AVE E
SE 274TH ST
SR 167
R ST NW
17TH ST SE
D
RIV
E
W
A
Y
SE 301ST ST
RAMP
RAMP
SR 167
TBD
SR 167
RAMP
RAMP
T
B
D
SR 167
SE 272ND ST
TBD
S 277TH ST
R
A
M
P
108TH AVE E
M ST NE
DRIVEWAY
56TH AVE S
SR 18
SR 18
H ST NE
RAMP
R A M P
SR 167
21ST ST E
144
T
H
AV
E
S
E
SE 282ND ST
T
B
D
R A M P
DRIVEWAY
SR 167
16TH ST E
55TH AVE S
TBD
D
R
I
V
E
WAY
108TH AVE E
S 277TH ST
10
8
TH
A
VE
S
E
R AM P
51ST AVE S
13TH ST E
8TH ST E
5 1 S T S T S E
TBD
SR 18
32ND ST E
R
A
M
P
24TH ST E
5 5 T H P L S
51ST AVE S
SR 167
RAMP
104TH AVE SE
12TH ST E
SE 284TH ST
2ND ST SE
RA
M
P
D ST SE
26TH ST NE
SE 272ND ST
TBD
124TH AVE SE
R ST NW
9TH ST E
V ST SE
TBD
8TH ST E
1ST AVE N
S R 1 8
T B D
TBD
SE 282ND ST
200TH AVE E
R A M P
R A M P
R A M P
TBD
TBD
110TH AVE SE
SR 167
8TH ST NE
C ST N
W
T
B
D
RAMP
TBD
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 4,000 feet
December 2009
L E G E N D
Pump Station
Infiltration Pond
Detention Pond
Stormwater Vault
Storm Pipe
Open Channel (Ditch)
Roadway
Water Body
Watercourse
Wetland
Auburn City Boundary
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig4-7(infra).mxd
2,00002,0004,000
Feet [N
FIGURE 4-7
DRAINAGE INFRASTRUCTURE
FOR THE CITY OF AUBURN
STORMWATER UTILITY
4
L a k eT a p p s
B i g S o o s C r e e k
Mill Creek
R i v e r
G
r e e n
R
i
ver
M i l l C r e e k
CrMill
G
r e e n
R
i
v
e
r
G
r
e
e
n
River
W h i t e
G r e e n
R i v e r
Soosette
Creek
River
W h i t e
Bow m an
C
r
e
e
k
W h i t e
R iv e r
R i v e r
WhiteLake
M
u
l
l
e
n
S
l
o
u
g
h
Green R i v e r
Lake Meridian
W h i t e
S
R
1
6
7
SR 18
A
S
T
S
E
C ST SW
AUBURN W
AY S
B ST NW
I ST NE
AUBURN WAY N
R ST SE
132ND AVE SE
RAMP
WEST VALLEY HWY NW
M ST SE
8TH ST E
E M A IN S T
24TH ST E
124TH AVE SE
EA
ST VALLEY HWY SE
122ND AVE E
BUTTE AVE
110TH AVE E
15TH ST SW
SE 288TH ST
2ND ST EJOVITA BLVD
C ST NE
S 384TH ST
SE 312TH ST
S 277TH ST
W MAIN ST
15TH ST NW
C ST NW
198TH AVE E
53RD ST SE
9TH ST E
29TH ST SE
GREEN VALLEY RD
1
7
9
T
H
A
V
E
SE 320TH ST
114
T
H
AV
E
E
116TH AVE SE
EDWARDS RD E
LAKE TAPPS PKW Y SE
41ST ST SE
WEST VALLEY HWY SW
S T U C K R I V E R D R
16TH ST E
K
E
R
S
E
Y W
AY S
E
147TH AVE SE
4TH ST E
18TH ST E
M ST NE
12TH ST E
SE 304TH ST
1
9
0
T
H
A
V
E
E
112TH AVE E
3RD AVE SE
ELLIN GSON RD SW
37TH ST SE
PERIMETER RD
SE 272ND ST
4
6
T
H
P
L
S
8T H S T N E
182ND AVE E
37TH ST NW
AC
AD
EM
Y DR SE
SE LAKE HOLM RD
22ND ST NE
L
A
K
E
L
A
N
D
H
I
L
L
S
W
A
Y
S
E
ORAVETZ RD SE
VALENTINE AVE SE
C
U
T
O
F
F
51ST AVE S
SE 282ND ST
144TH AVE SE
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
55TH AVE S
185T
H AV
E E
214TH AVE E
D ST SE
1ST AVE SE
TACOMA BLVD
A
U
B
U
R
N
-E
N
U
M
C
L
A
W
R
D
D ST N
W
A ST NE
4T H S T S E
TBD
CELERY AVE
30TH ST NE
108TH AVE
EAST BLVD (BOEING)
112TH AVE SE
SE 316TH ST
148TH AVE SE
T
A
C
O
M
A
P
O
I
N
T
D
R
E
55TH ST SE
E
V
E
R
G
R
E
E
N
W
A
Y
S
E
D ST NE
M ST NW
O ST NE
S
E 368
T
H P
L
W ST NW
1
6
9
T
H
A
V
E
E
S 287TH ST
3RD AVE S
5TH AVE SW
E ST NE
37TH ST N E
142ND AVE E
S 316TH ST H
A
R
V
E
Y R
D
S
C
E
NIC D
R S
E
H ST NW
M
A
I
N
S
T
S 292ND ST
WEST BLVD (BOEING)
44TH ST NW
3RD AVE SW
118TH AVE E
10 TH ST N E
CLAY ST NW
4TH AVE SW
148TH AVE E
7T H ST SE
137TH AVE E
26TH ST E
136TH AVE E
SE 310TH ST
S 3RD AVE
THO
RTON AVE SW
2
0
0
T
H
A
V
E
E
17TH ST E
RIV E R D R
BOUNDARY BLVD
L E A H I L L R D S E
32ND ST E
118TH AVE SE
58TH AVE S
ALGONA BLVD N
104TH AVE SE
S 372ND ST
J ST NE
ROY RD SW
4T H S T N E
PACIFIC AVE S
110TH AVE SE
14TH ST NE
D
R
I
V
E
W
A
Y
SE 281ST ST
160TH AVE SE
126TH AVE E
5T H ST SE
72ND AVE S
56TH PL S
25TH ST E
BR
IDG
ET AVE SE
57TH AVE S
S 328TH ST
DOGWOOD ST SE
2ND AVE SW
8TH ST SE
S 279TH ST
L ST SE
T ST SE
F ST SE
FRONTAGE RD
C
O
T
T
A
G
E
R
D
E
S 358TH ST
FOSTER AVE SE
52ND AVE S
S E 2 7 4 T H S T
166TH AVE E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
4 9 T H S T N E
S 362ND ST
I
S
T
N
W
54TH AVE S
A ST SW
57TH PL S
U
S
T
N
W
32ND ST NE
7
8
T
H
A
V
E
S
3RD ST E
D
E
E
R
I
S
L
A
N
D
D
R
E
135TH AVE SE
47TH ST SE
2
0
4
T
H
A
V
E
E
28TH ST N E
8
6
T
H
A
V
E
S
S 356TH ST
J ST SE
R ST NW
27TH ST E
15TH ST E
28TH ST E
MILITARY RD S
13TH ST E
K ST SE
OLIVE AVE SE
10TH ST E
1
0
8
T
H
AV
E
E
SE 323RD PL
B ST SE
WYMAN DR
26TH ST SE
S 336TH ST
ST PAUL BLVD
S 340TH ST
C ST SE
B ST NE
32 N D S T S E
S 3 0 0 T H S T
1ST AVE S
36TH ST SE
ELM LN
SE 301ST ST
2
0
8
T
H
A
V
E
E
SE 287TH ST
V ST NW
2N D S T S E
23RD ST SE
4TH AVE S
3RD ST SE
QUINCY AVE SE
21ST ST NE
1
5
6
T
H
A
V
E
E
140TH AVE E
HEMLOCK ST SE
1
8
4
T
H
C
T E
5
6
T
H
A
V
E S
SE 298TH PL30TH ST NW
30TH ST SE
S 318TH ST
24TH ST SE
2ND AVE S
14TH ST E
H ST NE
LUND RD SW
S 324TH ST
PIKE ST NW
21ST ST E
3 1 S T S T E
42ND ST NW
6TH AVE SW
119
T
H
AV
E
E
SE 286TH ST
9TH ST SE
55TH PL S
SE 276TH PL
65TH AVE S
SE 295TH PL
G ST NE
2 7 T H S T S E5TH AVE N
SK
I
N
N
E
R
R
D
128TH AVE E
S 354TH ST
S 344TH ST
SE 364TH ST
SE 290TH ST
10TH ST SE
D ST SW
SE 280TH ST
2
1
1
T
H
A
V
E
E
NATHAN AVE SE
V ST SE
1
0
4
T
H
P
L S
EHI CREST DR
B PL NW
SE 294TH ST
7 2 N D S T S E
S 285TH ST
6TH ST NW
146TH AVE SE
SE 2 93 RD ST
3RD ST NW
126TH AVE SE
I
S
A
A
C
A
V
E
S
E
S 3 1 2 T H S T
ELM ST SE
CLAY ST
S 370TH ST
20TH ST E
52ND PL S
7 T H S T E
19TH DR NE
SE 307TH PL
5 1 S T S T S E
10TH AVE N
S 364TH ST
140TH AVE SE
28TH ST SE
15TH ST SE
133RD AVE SE
108TH AVE SE
7 3 R D S T S E
SE 295TH ST
26TH ST NE
S 366TH ST
SE 297TH ST
2
1
0
T
H
A
V
E E
66TH ST SE
24TH ST NE
SE 296TH ST
SE 285TH ST
S 368TH ST
ALDER LN S
117TH AVE SE
U ST SE
19TH ST SE
6TH ST SE
110TH PL SE
A S T E WARD AVE SE
156TH AVE SE
21ST ST SE
R PL NE
117
T
H
AV
E
E
105TH AVE SE
7TH ST
5T H S T N E
53RD AVE S
HEATHER AVE SE
F
S
T
N
E
1
1
2
T
H
P
L
S
E
51ST PL S
SE 292ND ST
D PL SE
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
123RD AVE E
63RD PL S
2ND CT NW
1S T S T N E
R ST NE
129TH PL SE
O CT SE
S 342ND ST
26TH ST NW
SE 321ST PL
114TH PL SE
SR 18
53RD AVE S
13TH ST E
RAMP
R
A
M
P
32ND ST E
148TH AVE SE
DRIVEWAY
DRIVEWAY
51ST AVE S
RAMP
SR 167
RAMP
SE 296TH ST
D
R
I
V
E
W
A
Y
17TH ST SE
142ND AVE E
16TH ST E
R A M P
SE 288TH ST
12TH ST E
R A M P
108TH AVE SE
144TH AVE SE
8TH ST E
SE 272ND ST
51ST AVE S
24TH ST E
RAMP
S 277TH ST
200TH AVE E
D ST SE
R A M P
TBD
T B D
16 TH S T E
H ST N
E
SE 292ND ST
SR 167
R ST NW
T
B
D
9TH ST E
DRIVEWAY
SE 282ND STSE 282ND ST
55TH AVE S
S R 18
104TH AVE SE
8TH ST E
51 S T S T S E
TBD
RAMP
SE 272ND ST
RAMP
110TH AVE SE
TBD
2ND ST SE
TBD
SR 18
SE 274TH ST
RAMP
SR 167
SE 284TH ST
108TH AVE E
R A M P
SE 301ST ST
SR 167
26TH ST NE
DRIVE W AY
55TH PL S
R
A
M
P
SR 167
TBD
1ST AVE N
TBD
32ND ST E
T B D
S 2 77 T H ST
124TH AVE SE
RAMP
RAMP
TBD
SR
1
6
7
R ST NW
56TH AVE S
SR 167
M ST NE
V ST SE
TBD
TBD
TBD
SR 167
8 T H S T N E
C ST NW
TBD
RAMP
S R 1 8
TBD
21ST ST E
C8
C9
C4
C1 C3
C6C7
C5C2S5
S1
S3
S2
S6
S4
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 4,000 feet
December2009
P:\135347 Auburn Drainage Phase II\GIS\MXD\Draft Plan Figures\AurburnStorm_Fig4-8(crit fac).mxd
2,000 0 2,000 4,000Feet N
FIGURE 4-8CRITICAL FACILITIESFOR THESTORMWATER UTILITY
L E G E N D
CITY CRITICAL FACILITY
STORM CRITICAL FACILITY
Roadway
Auburn City Boundary
Water Body
Watercourse
Wetland
S1 A Street PS 404 A Street SES2Auburn Way S PS 405 Auburn Way SS3Brannan Park PS 1302 30 th Street NES4Emerald Park PS 499 42 nd Street NES5West Main Street PS 1410 W Main StreetS6White River PS 4640 A Street SE
C1 City Hall 25 W Main StreetC2IS Dept. Office 8 1 st Street SEC3Justice Center 340 E Main StreetC4M&O 1305 C Street SWC5Regional Hospital 201 N Division StreetC6Senior Center 808 9 th Street SEC7VRFA Station 31 1101 D Street SEC8VRFA Station 32 1951 R Street SEC9VRFA Station 35 2905 C Street SW
STORM CRITICAL FACILITIES
CITY CRITICAL FACILITIES
C1 C3
C5
C2
S1 S2
A ST SE
C ST SW
E M A I N S T
C ST NW
SR 1 8
4 T H S T N E
RAMP
E ST NE
4TH ST SE
I ST SE
D ST SE
AUBURN WAY S
2N D ST N E
F
S
T
S
E
H ST SEE ST SE
G
S
T
S
E
D ST NW
A ST SW
A ST NE
7TH ST SE
W MAIN ST
8TH ST SE
B ST NE
1S T S T N E
3RD ST N E
A ST NW
H ST NE
D ST SW
3RD ST NW
S DIVISION ST
6TH ST SE
P A R K A V E N E
6TH S T N E
5TH ST SW
8TH ST SE
6TH ST SE
S R 1 8
RAMP
R A M P
R A M P
R
A
M
P
D
S
T
S
E
SR 1 8
7TH ST SE
!(
!(
!(!(
!(
!(
!(
L a k e
T a p p s
B i g S o o s C r e e k
Mill Creek
R i v e r
G
r
e
e
n
R
iver
M
i l l
C
r e e k
Creek
Mill
G
r
e
e
n
R
i
v
e
r
G
r
e
e
n
River
W h i t e
G
r
e
e
n
R i v e r
Soosette
Creek
Rive
W
h i t
e
B o w m a n
C
r
e
e
k
W h i t e
R iv e r
R i v e r
White
Lake
e
n
S
l
o
u
g
h
Meridian
W h i t e
S
R
1
6
7
S R 1 8
A ST SE
C ST SW
B ST NW
I ST NE
AUBURN WAY N
A
U
B
U
R
N
W
A
Y
S
R ST SE
132ND AVE SE
RA M P
WEST VALLEY HWY NW
M ST SE
8TH ST E
E MAIN ST
24TH ST E
124TH AVE SE
EAST VALLEY HWY SE
122ND AVE E
C ST NW
BUTTE AVE
110TH AVE E
15TH ST SW
SE 288TH ST
2ND ST E
C ST NE
SE 312TH ST
S 277TH ST
W MAIN ST
J
O
VIT
A B
LV
D
15TH ST NW
S 384TH ST
198TH AVE E
53RD ST SE
9TH ST E
29TH ST SE
1
7
9
T
H
A
V
E
SE 320TH ST
114TH AVE E
GREEN VALLEY RD
116TH AVE SE
EDWARDS RD E
LAKE TAPPS PKWY SE
4 1 S T S T S E
WEST VALLEY HWY SW
S T U C K R I V E R D R
16TH ST E
K
E
R
S
E
Y
W
A
Y
S
E
147TH AVE SE
4TH ST E
18TH ST E
M ST NE
12TH ST E
SE 304TH ST
1
9
0
T
H
A
V
E
E
112TH AVE E
3RD AVE SE
ELLINGSON RD SW
37TH ST SE
PERIMETER RD
SE 272ND ST
4
6
T
H
P
L
S
8TH ST NE
182ND AVE E
37TH ST NW
ACADEMY DR SE
SE LAKE HOLM RD
22ND ST NE
L
A
K
E
L
A
N
D
H
I
L
L
S
W
A
Y
S
E
O R A V E TZ R D S E
VALENTINE AVE SE
C
U
T
O
F
F
5
1
S
T
AV
E
S
SE 282ND ST
144TH AVE SE
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
55TH AVE S
1
8
5
T
H
A
V
E
E 214TH AVE E
D ST SE
1ST AVE SE
TACOMA BLVD
D ST NW
A ST NE
4TH ST SE
TBD
CELERY AVE
30TH ST NE
10
8
T
H AVE
EAST BLVD (BOEING)
112TH AVE SE
SE 316TH ST
148TH AVE SE
T
A
C
O
M
A
P
O
I
N
T
D
R
E
55TH ST SE
E
V
E
R
G
R
E
E
N
W
A
Y
S
E
EMERALD DOWNS DR NW
D ST NE
M ST NW
O ST NE
SE 368TH PL
W ST NW
1
6
9
T
H
A
V
E
E
S 287TH ST
3RD AVE S
1
8
6
T
H
A
V
E
E
5TH AVE SW
E ST NE
142ND AVE E
S 316TH ST
H
A
R
V
E
Y
R
D
S
C
E
N
I
C
D
R
S
E
H ST NW
M
A
I
N
S
T
S 292ND ST
WEST BLVD (BOEING)
44TH ST NW
3RD AVE SW
ALGONA BLVD N
118TH AVE E
10TH ST NE
CLAY ST NW
4TH AVE SW
148TH AVE E
7TH ST SE
137TH AVE E
2
6
T
H
S
T
E
136TH AVE E
SE 310TH ST
S 3RD AVE
THORTON AVE SW
2
0
0
T
H
A
V
E
E
17TH ST E
R I V E R D R
BOUNDARY BLVD
32ND ST E
118TH AVE SE
58TH AVE S
S 364TH PL
104TH AVE SE
S 372ND ST
J ST NE
ROY RD SW
4TH ST NE
PACIFIC AVE S
110TH AVE SE
14TH ST NE
D
R
I
V
E
W
A
Y
SE 281ST ST
126TH AVE E
72
N
D
A
V
E
S
56TH PL S
2
5
T
H
S
T
E
BRIDGET AVE SE
I ST SE
57TH AVE S
S 328TH ST
DOGWOOD ST SE
2ND AVE SW
8TH ST SE
S 279TH ST
L ST SE
3RD AVE N
W
T ST SE
F ST SE
FRONTAGE RD
FOSTER AVE SE
52ND AVE S
H ST SE
SE 274TH ST
1ST ST E
166TH AVE E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
49T H ST N E
S 362ND ST
E ST SE
NORMAN AVE SE
H
O
W
A
R
D
R
D
I ST NW
32ND PL NE SE 296TH WAY
54TH AVE S
A ST SW
57TH PL S
U
S
T
N
W
7
8
T
H
A
V
E
S
3RD ST E
D
E
E
R
I
S
L
A
N
D
D
R
E
135TH AVE SE
4 7 T H S T S E
2
0
4
T
H
A
V
E
E
28TH ST NE
8
6
T
H
A
V
E
S
S 356TH ST
J ST SE
R ST NW
27TH ST E
15TH ST E
28TH ST E
MILITARY RD S
13TH ST E
K ST SE
OLIVE AVE SE
10TH ST E
108TH AVE E
85TH AVE S
31ST ST NE
SE 323RD PL
54TH PL S
B ST SE
WYMAN DR
26TH ST SE
S 336TH ST
ST PAUL BLVD
S 340TH ST
C ST SE
B ST NE
32ND ST SE
S 300TH ST
1ST AVE S
36TH ST SE
ELM LN
SE 301ST ST
2
0
8
T
H
A
V
E
E
SE 287TH ST
V ST NW
2ND ST SE
23RD ST SE
4TH AVE S
QUINCY AVE SE
29TH ST NW
21ST ST NE
1
5
6
T
H
A
V
E
E
HEMLOCK ST SE
A ST NW
1
8
4
T
H
C
T
E
5
6
T
H
A
V
E
S
SE 298TH PL
30TH ST SE
S 318TH ST
24TH ST SE
2ND AVE S
14TH ST E
H ST NE
LUND RD SW
S 324TH ST
PIKE ST NW
21ST ST E
31ST ST E
42ND ST NW
6TH AVE SW
SUPERMALL DR SW
119TH
AV
E E
SE 286TH ST
9TH ST SE
55TH PL S
SE 276TH PL
65TH AVE S
SE 295TH PL
G ST NE
O ST SE
27 TH ST SE
5TH AVE N
SKINNER RD
125TH AVE E
1
0
2
N
D
A
V
E
S
E
128TH AVE E
S 354TH ST
S 344TH ST
SE 364TH ST
SE 290TH ST
10TH ST SE
D ST SW
SE 280TH ST
SE 283RD PL
2
1
1
T
H
A
V
E
E
NATHAN AVE SE
V ST SE
HI CREST DR
B PL NW
SE 294TH ST
S 285TH ST
6TH ST NW
146TH AVE SE
SE 293RD ST
PEARL AVE SE
126TH AVE SE
16TH ST SE
I
S
A
A
C
AV
E
S
E
S 3 1 2 T H S T
L ST NE
ELM ST SE
S 370TH ST
20TH ST E
52ND PL S
7TH ST E
19TH DR NE
SE 307TH PL
5 1 S T S T S E
10TH AVE N
S 364TH ST
SE 277TH PL
140TH AVE SE
28TH ST SE
PERRY AVE SE
7 2ND S T S E
SE 42ND ST
133RD AVE SE
108TH AVE SE
7 3 R D S T S E
SE 295TH ST
14TH ST SE
26TH ST NE
S 366TH ST
SE 297TH ST
2
1
0
T
H
A
V
E
E
24TH ST NE
SE 296TH ST
SE 285TH ST
S 368TH ST
ALDER LN S
117TH AVE SE
U ST SE
6TH ST SE
110TH PL SE
A ST E WARD AVE SE
SE 286TH PL
21ST ST SE
R PL NE
117TH
AV
E E
107TH PL SE
33RD ST SE
105TH AVE SE
117TH PL SE
7TH ST
5TH ST NE
53RD AVE S
N ST SE
HEATHER AVE SE
F ST NE
11
2T
H
PL SE
51ST PL S
SE 292ND ST
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
123RD AVE E
63RD PL S
THORTON PL SW
1ST ST NE
R ST NE
2ND ST NE
146TH AVE E
129TH PL SE
6TH ST NE
3RD ST NE
S 342ND ST
26TH ST NW
121ST AVE SE
111TH PL SE
SE 321ST PL
114TH PL SE
106TH PL SE
25TH ST SE
55TH AVE S
R
A
M
P
8TH ST E
RAM
P
SR 18
5 5 T H P L S
17TH ST E
110TH AVE SE
SE 272ND ST
8TH ST E
S 277TH ST
104TH AVE SE
RAMP
TBD
56TH AVE S
SR 167
R
A
M
P
R A M P
DRIVEWAY
SR 18
R A M P
SE 292ND ST
51ST AVE S
T B D
1ST AVE N
TBD
9TH ST E
RAMP
21ST ST E
TBD
24TH ST E
R A M P
SE 301ST ST
135TH AVE SE
TBD
TBD
O ST SE
D
RIV
E
W
A
Y
R
A
M
P
12TH ST E
RAMP
54TH AVE S
RAMP
SE 282ND ST
D ST NW
K ST SE
124TH AVE SE
32ND ST E
SR 167
S R 1 8
13TH ST E
RAMP
8TH ST NE
R A M P
SE 288TH ST
SR 167
5 1 S T S T S E
D
R
I
V
E
WAY
RAMP
T
B
D
TBD
26TH ST NE
200TH AVE E
SR 167
32ND ST E
R AM P
T
B
D
18TH ST E
16TH ST E
144TH AVE SE
TBD
SE 284TH ST
25TH ST E
R ST NW
D ST SE
SE 296TH ST
W
EST
VA
LLEY HW
Y SW
R A M P
TBD
R ST NW
51ST AVE S
S 277TH ST
R
A
M
P
SR 167
RA
MP
SR 167
RAMP
TBD
SR 167
TBD
T
B
D
108TH AVE SE
H ST NE
TBD
SR 18RAMP
T
B
D
SE 282ND ST
SE 304TH ST
SR 18
R ST SE
112TH AVE SE
S 277TH ST
P5
P7
P6
P3 P4
P2
P1
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 3,779 feet
December 2009
L E G E N D
Roadway
Watercourse
Water Body
Wetland
!(Drainage Problem Vicinity
Auburn City Boundary
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig4-9(drainage).mxd
2,00002,0004,000
Feet [N
FIGURE 4-9
HIGH-PRIORITY PROBLEM
LOCATIONS FOR THE CITY
OF AUBURN STORMWATER UTILITY
ID*Location
P1 Intersection: Auburn Way S and SR 18
P2 Intersection: Second St. SE and G St. SE
P3 Intersection: F St. SE and SR 18
P4 M St. SE near Third St. SE
P5 West St. dead end near SR 167
P6 Intersection: 30th St. NE and C St. NE
P7 C St. NE near 37th St. NE
*Only includes problems identified as high-priority
S R 1 8
A S
T S
E
C ST SW
C ST NW
RAMP
AUBURN WAY N
E MAIN ST
AUBURN WAY S
W MAIN ST
H ST NW
A ST NE
12TH ST SE
B ST SE
E ST NE
D ST SE
4TH ST NE
2ND ST NE
F ST SE
E ST SE G ST SE
D ST NW
A ST SW
4TH ST SE
2ND ST SE
2ND ST NW
B ST NE
1ST ST NE
3RD ST NE
A ST NW
AUBURN AVE NE
D ST SW
10TH ST SE
5TH ST SE
8TH ST NE
7TH ST SE
F ST SW
D
R
IV
E
W
A
Y
6TH ST NW
E ST SW
3RD ST NW
S DIVISION ST
G ST SW
8TH ST SE
1ST ST SW
5TH ST NE
10TH ST NE
6TH ST SE
C ST SE
N DIVISION ST
F ST NW
7TH ST NE
G ST NW
F
ST NE
PARK AVE NE
8TH ST SW
CROSS ST SE
3RD ST SW
D ST NE
6TH ST NE
9
T
H
S
T
N
E
1ST ST NW
F PL NE
10TH ST NW
9TH ST SE
11TH ST SE
TRANSIT RD SW
1ST ST SE
2ND ST SW
B ST NW
B ST SW
5TH ST SW
5TH ST NW
3RD ST SE
2ND ST SE
RAMPSR 18RAMP
G ST NW
11TH ST SE
SR 18
10TH ST NE
1ST ST SW
3RD ST NE
1ST ST NE
3RD ST SW
RAMP
8TH ST SE
11TH ST SE
R
A
M
P
9TH ST SE
F ST SE
6TH ST NW
RAMP
B ST NE
A ST NE
A ST NE
DRIVEWAY
7TH ST NE
10TH ST SE
7TH ST SE
3RD ST SW
D ST SE
R A M P
RAMP
R
A
M
P
8TH ST NE
N DIVISION ST
F ST SE
F ST
SE
E ST SE
2ND ST NW
1ST ST SW
RAMP
6TH ST SE
D ST NE
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 500 feet
December 2009
L E G E N D
Downtown Auburn (Comp Plan, 2008)
Urban Center (Comp Plan, 2008)
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig4-10(downtown).mxd
2500250500
Feet [N
FIGURE 4-10
CITY OF AUBURN
DOWNTOWN AREA AND
URBAN CENTER
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P:\135347 Auburn Drainage Phase II\009 Storm Drainage Comprehensive Plan\Final\Auburn Drainage Plan Final Dec09(v2).doc
CITY OF AUBURN COMPREHENSIVE
STORMWATER DRAINAGE PLAN
5. EVALUATION OF THE STORMWATER UTILITY
This chapter presents analyses conducted to evaluate the stormwater utility and identify gaps
between existing service levels and the desired LOS described in Section 3.2.2. The following types
of investigations are designed to evaluate the stormwater utility with respect the entire range of LOS
goals:
Hydraulic: gather system data, develop computer models, and assess hydraulic performance
with respect to LOS and associated system design criteria
Asset life-cycle: collect asset information, identify priorities and standards based on LOS,
conduct condition assessments, and compare asset conditions with priorities and standards
Environmental: assess regulatory requirements, determine time to noncompliance, and assess
risk factors associated with non-compliance
Maintenance and Operations: assess process performance, equipment, and personnel with
respect to LOS for M&O
The above types of investigations require substantial data collection and analysis and are often
completed using a phased approach. Furthermore, many investigations require continual updates as
new data and information become available. Therefore, this Drainage Plan describes not only
investigations conducted in support of its development, but it also outlines a plan of activities for
future investigations (see Chapter 7).
Investigations conducted as part of this planning effort were those essential to the development of
capital improvements for the 6-year and 20-year horizons (e.g., hydraulic investigations and asset
life-cycle investigations). A separate but concurrent investigation was completed to evaluate the
stormwater utility with respect to NPDES compliance (e.g., environmental investigation). The
following sections summarize these activities.
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5.1 Hydraulic Investigation
As described in Chapter 4, the city of Auburn owns and operates a large system of stormwater
drainage infrastructure to collect and convey stormwater runoff to nearby receiving waters. Analysis
of this drainage system required construction and application of a hydraulic model to evaluate
conveyance capacity of various infrastructure elements relative to LOS goals. Such a model was used
for development of the 2002 Drainage Plan using XP-SWMM1 software.
5.1.1 Review of Existing Model
As a preliminary step to conducting new hydraulic investigations, the existing XP-SWMM model
was reviewed to determine its suitability for use in subsequent analyses (see Appendix D). The
review concluded that the XP-SWMM model would require substantial modifications before new
modeling analyses could be conducted. The primary deficiencies were as follows:
There was limited correlation between existing GIS-based infrastructure data and the input data
contained in the XP-SWMM model. The geospatial coordinates of pipes and manholes in the
XP-SWMM model did not match with corresponding elements in the City’s GIS databases, nor
was there a consistent difference between the values. Furthermore, the identification numbers for
infrastructure elements was not consistent between GIS databases and the XP-SWMM model.
Many of the XP-SWMM and GIS data node elevations were offset by about 3.5 feet. This
difference is attributable to the use of two different vertical datums: the XP-SWMM model was
referenced to the North American Vertical Datum of 1988 (NAVD88), while the GIS system is
referenced to the National Geodetic Vertical Datum of 1929 (NGVD29). The difference
between these two vertical datums is approximately 3.5 feet in the Auburn area. Of greater
concern was the fact that not all elevations were offset by 3.5 feet, which suggests that some
portions of the model were built in the NAVD88 datum and other parts were built on the
NGVD29 datum.
The XP-SWMM model consisted of hydrologic parameters designed for event-based hydrologic
modeling (e.g., simulation of rainfall-runoff processes over a relatively short duration, such as
24 hours). A more appropriate method for evaluating LOS goals is a continuous-simulation
hydrologic model, which evaluates rainfall-runoff processes over a long period of time to account
for seasonal variations conditions such as soil moisture. For example, an event-based model only
looks at rainfall over a short duration and must assume the degree to which soils are saturated at
the beginning of the rainfall event. Alternatively, a continuous-simulation model examines rainfall
over the course of several seasons, which accounts for soil moisture based on occurrences of dry
periods or successive rainfall events.
1 XP-SWMM is a program developed by XP Software for hydrodynamic modeling of stormwater and wastewater
collection systems. XP-SWMM uses the SWMM5 engine, which is public domain modeling software distributed by the
EPA. Information about XP-SWMM software can be found at http://www.xpsoftware.com/products/xpswmm/.
5: Evaluation of the Stormwater Utility COMPREHENSIVE STORMWATER DRAINAGE PLAN
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Both the XP-SWMM model and the City’s GIS databases were found to contain data gaps,
particularly in newly developed or newly annexed areas. As the City works toward creating a
comprehensive stormwater infrastructure data inventory, the link between GIS databases and
hydraulic models becomes even more important.
Given the results of the review, it was decided that the most efficient way to proceed would be to
develop a new hydraulic model with the City’s GIS databases as a basis for data inputs. In this
manner, the City could continue to update its system inventory in GIS and simultaneously create an
up-to-date hydraulic model. In addition to increased efficiency, linking the system inventory with the
hydraulic modeling analysis provides a crucial benefit in improved model accuracy. Hydraulic
modeling analyses are used to identify potentially millions of dollars of capital improvements; thus, it
is important to utilize the most accurate and up-to-date information to represent the system.
MIKE URBAN2 software was selected for the development of the stormwater collection system
model. The City had selected MIKE URBAN for use in the modeling of the sanitary sewer
collection systems, and changing to MIKE URBAN for stormwater collection system modeling
would provide a consistent platform within the City. MIKE URBAN also provides a useful platform
for updating geospatial data inputs that can easily be exported to GIS using common data formats.
5.1.2 Modeling Methodology
Appendix D provides a detailed description of system inventory data development and hydrologic
and hydraulic modeling methodology. The following is a general description of steps followed in the
modeling methodology:
1. Infrastructure data from existing GIS databases were used to build drainage networks by
sub-basin in MIKE URBAN. These data were validated and augmented as necessary
based on as-built drawings and field investigations. Drainage network models consist of
catch basins, manholes, pipes, junctions, ditches, control structures, vaults, storage
ponds, pump stations, and outfalls.
2. The drainage network was developed to a level of detail that is sufficient for analyzing
conveyance on a system-wide scale. Pipes with a diameter of less than 1 foot were
generally not included unless they provided an important link within the system. Pipes
1 foot in diameter or greater were included; smaller-diameter pipes and pipes that were
part of private systems were generally not included in the model. Such pipes were
modeled in some cases due to difficulties in spatially differentiating between public and
private systems.
3. Infrastructure data development was completed for high-, medium-, and low-priority
sub-basins (see Section 4.2 for a description of priorities).
2 MIKE URBAN is a GIS-integrated, modular software program developed by the Danish Hydraulic Institute for
modeling water distribution and collection systems. The stormwater module is internally powered by the SWMM5
engine, which is public domain software distributed by EPA. Information about MIKE URBAN software can be found
at http://www.dhigroup.com/Software/Urban/MIKEURBAN.aspx.
5: Evaluation of the Stormwater Utility COMPREHENSIVE STORMWATER DRAINAGE PLAN
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4. Sub-basin areas were divided into smaller drainage area delineations called sub-
catchments, which in the model are linked into the drainage network at specific nodes.
Hydrologic parameters such as area, slope, and percent impervious area are developed
for each sub-catchment. This step was completed for high- and medium-priority sub-
basins.
5. Models were calibrated using historic flood levels and pump runtime data where
available. Simulations were run for the November 2006 and December 2007 events, for
which the city experienced severe flooding in several areas. This step was completed for
high-priority sub-basins.
6. Long-term simulations were performed to identify locations where LOS-based capacity
goals (e.g., capacity to convey a 25-year stormwater flow) were not met. Alternative
scenarios were developed and analyzed to identify ways to alleviate the flooding
problems through capital improvements (see Chapter 6 for a description of proposed
capital improvements). This step was completed for high-priority sub-basins where
problems were confirmed to exist.
Modeling activities were limited by the availability of data for calibration. A flow monitoring plan
has been developed to collect data that can be used to further refine future modeling efforts. In
addition, flow monitoring data can also be used to refine the modeling analyses used to develop
capital improvement projects. The monitoring plan is included in Appendix E, and recommended
activities from the monitoring plan are included in Chapter 7.
5.2 Asset Life-Cycle Investigation
Asset management is not a new practice for storm drainage utilities. All utilities manage their assets
in one way or another through maintenance practices, capital improvement projects, and R&R
activities. However, for most storm drainage utilities, the means of deciding where and how to direct
limited resources has often been done in a reactive, ad hoc approach based on incomplete or
incorrect information. In contrast, the term “asset management” usually refers to a process-based,
data-driven means of effectively managing assets. To have an effective asset management program,
the National Association of Clean Water Agencies defined asset management in the 2002 Asset
Management Handbook as “an integrated set of processes to minimize the life-cycle costs of
infrastructure assets, at an acceptable level of risk, while continuously delivering established levels of
service.”
The key elements of this definition are the life-cycle costs of assets, the risk associated with those
assets, and the LOS goals expected of the utility. The first step to effectively manage storm drainage
assets is to establish LOS goals for the City’s storm drainage utility as described in Chapter 3 of this
Drainage Plan. The next steps include performing asset assessments and economic analyses to
estimate life-cycle costs and the risk associated with each of the City’s storm drainage assets.
Investigations completed for this Drainage Plan focused on pipes and pump stations. Section 5.2.1
describes an economic life analysis of the City’s stormwater drainage pipes. Section 5.2.2 summarizes
an assessment of the City’s stormwater pumping stations.
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5.2.1 Economic Life Analysis of Drainage Pipes
An economic life model was developed to evaluate life-cycle costs and risk for the City’s storm
drainage pipe assets. The model first provides a table identifying each of the storm drainage pipes by
age, material, length, and manhole. The model next develops a risk cost associated with each asset by
multiplying a probability of failure in a year for each asset by the cost of that asset failing (including
capital, social, and environmental costs). Finally, the risk cost associated with each asset is compared
to the life-cycle cost of owning the asset to identify appropriate timing for asset renewal or
replacement. A detailed description of the economic life analysis is provided in Appendix F. The
following are basic steps in the development of the economic life analysis:
Probability of failure: A statistical distribution was used to represent the probability of failure in
any future year given an asset’s age and expected service life. Condition-specific modifications
were made to each asset based on factors such as frequency of maintenance activities, proximity
to critical slopes, and pipe length. The result is an annual probability of failure calculated for each
of the City’s storm drainage pipes.
Cost of failure: The consequence of an asset failing is determined by weighing the financial,
social, and environmental costs associated with a potential failure to meet design service levels.
Consequence parameters were identified and assigned estimated costs to capture the impact of an
asset failure. Total cost of failure for an asset includes the cost of repairs (increased if the asset
was located in areas difficult to repair), the cost of a disruption in service to both the public and
to the utility, cleanup costs, and the additional cost of reactively responding to an asset failure.
Cost of disruption varies based on the land use of the effected area. Additional details regarding
cost considerations are described in Appendix F.
Risk cost: The risk cost associated with each asset is calculated based on the probability and cost
of a failure. Although the cost of failure is considered static, risk costs increase with time because
the probability of a failure increases as an asset ages.
Life-cycle cost: To determine the economically optimal timing for asset replacement or renewal,
the life-cycle cost for each asset was estimated. The capital cost and risk cost associated with a
pipe replacement and lining were calculated, annualized, and added together to develop the
annualized cost of ownership for each asset. Because the annualized capital costs decrease as an
asset ages while the annualized risk costs increase with age, the annualized cost of ownership has
a minimum value, as shown in Figure 5-1. This is the age for which the life-cycle cost of an asset
is minimized.
Optimal timing: To determine the best time to replace an existing asset, the risk cost associated
with that asset is compared to the minimum cost of ownership for its replacement. The optimal
time to replace occurs when the risk cost of an asset begins to exceed the minimum cost of
ownership for its replacement.
Prioritized maintenance: Given the results of the life-cycle cost analysis, pipe segments were
sorted based on the existing carried risk cost to identify those pipes that are most critical to the
City’s collection system. By identifying the most critical pipes, maintenance activities can be
prioritized to address the City’s assets that carry the most risk cost.
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Figure 5-1. Example of annualized cost of ownership with minimum highlighted in red (age 23)
The economic life model requires regular updates and data checks to ensure its completeness and
accuracy. At present, a significant number of data points have not been included into the model
because of a lack of data. As the drainage system inventory is improved the economic life model can
be updated and R&R priorities can be refined. Chapter 7 describes how the economic life model can
be used to identify and prioritize pipes for future activities such as predictive maintenance, repair or
replacement.
5.2.2 Pump Station Condition Assessment
A condition assessment was conducted to evaluate the City’s stormwater pump stations with respect
to LOS goals, health and safety requirements, and to identify ways to increase reliability or reduce
costs for operation and maintenance. Table 5-1 lists the pump stations included in the condition
assessment.
Table 5-1. City of Auburn Stormwater Drainage Pump Station Inventory
Number Pump station Year constructed Location
1 A St. SE 1973 A St. SE at underpass of SR 18 and BNSF Railroad bridges
2 Auburn Way S 1994 Auburn Way S, south of 4th St. SE
3 Brannan Park 2001 East end of 30th St. NE, west of Green River
4 Emerald Park 1999 42nd St. NE, west of C St. NE
5 White River 1981 A St. SE north of White River
6 West Main St. 2008 West end of West Main St. near SR 167
5: Evaluation of the Stormwater Utility COMPREHENSIVE STORMWATER DRAINAGE PLAN
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A detailed description of the pump station condition assessment is included in Appendix G. The
condition assessment included the following basic steps:
1. As-built information and M&O manuals were reviewed.
2. Equipment checklists were prepared for mechanical/hydraulic and electrical/control
systems.
3. Site visits were made to all stations; operation of each station was observed, but no
detailed physical testing of equipment, wiring, controls, or structures was conducted.
4. Operators and maintenance personnel were interviewed regarding known issues for each
location.
5. Each pump station was inspected according to the National Electrical Code (National
Fire Protection Association 70), which is the fundamental standard for ensuring that
electrical equipment installations meet minimum safety standards.
Evaluation of certain electrical equipment was excluded due to existing contracts for engineering
services. One contract is for evaluation and recommendations associated with possible upgrades to
the pump stations’ supervisory control and data acquisition (SCADA) system. This includes possible
upgrades to each station’s local SCADA/programmable logic controller (PLC) hardware, firmware,
software, and telemetry equipment and requirements. The second contract is to verify, evaluate, and
recommend backup power system requirements for each pump station. These requirements include
sizing for permanent, portable, and possibly rented equipment. Evaluations completed under those
contracts are also expected to include transfer switch requirements and equipment selection.
Therefore, evaluations completed in support of this Drainage Plan did not include details of the
SCADA system and backup power systems for the pump stations.
Two general system-wide observations can be made. First, each of Auburn’s stormwater pump
stations is unique. Second, the City has done an excellent job of maintaining all of its stations, some
of which are now more than 40 years old.
Recommendations for pump station improvements and ongoing asset assessments are made in
Chapters 6 and 7 respectively.
5.3 Environmental Investigation
The federal Clean Water Act requires municipalities to help maintain fishable/swimmable waters
through the NPDES Permit Program (see Section 2.3.2 and Appendix A), which requires
municipalities to reduce the discharge of pollutants from their stormwater systems to the MEP by
implementing municipal stormwater management programs. The City already had a municipal
stormwater management program in place at the beginning of the Permit term in 2007; however that
program did not meet all of the Permit requirements. The new Permit requires that each
municipality develop a SWMP for each year of the Permit. Each SWMP documents the
implementation of Permit requirements for that year. The Permit also requires tracking and
reporting of SWMP implementation activities in accordance with the required implementation dates
of the 5-year Permit term.
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The first step toward developing the SWMP document was to perform a legal requirements analysis
identifying what measures will be needed and by when, in order to comply with the Permit. The City
formed a project team consisting of staff from the City Attorney’s office, the City Utilities
Engineering Department, and Brown and Caldwell consultants to lead the Permit legal requirements
analysis.
The project team reviewed Auburn’s City-wide stormwater management programs, codes, standards,
processes, and documentation protocols in order to identify potential actions to comply with the
NPDES Permit conditions over the 5-year Permit period. From these documents, the project team
created a database cataloging responsible City departments/entities, reference documents, and
potential requirements for each section of the Permit. Interviews were then conducted with
appropriate staff (e.g., stormwater M&O staff) to supplement the knowledge base provided by the
documentation. The information on existing City practices and programs was then compared to the
legal requirements of the Permit to identify potential compliance needs. Some policy issues and
potential compliance strategies were also identified. The results of this analysis were used as the
foundation for development of a compliance work plan (see Appendix H) and the submittal of the
SWMP for the 2008 deadline. The SWMP was then revised in early 2009 and is included in
Appendix C. Recommended future activities from the compliance work plan are summarized in
Chapter 7.
5.4 Maintenance and Operations Investigation
A preliminary evaluation of system operation and maintenance was conducted in support of this
Drainage Plan (see Appendix I). The following is a summary of the findings from the preliminary
evaluation.
Open ditches comprise 40 percent of the drainage system. Sedimentation continues to occur
within the open ditches because of low-gradient channel slopes. Managing sediment aggradation
in open ditches requires substantial resources to maintain the correct slope and conveyance
capacity.
Approximately 60 percent of the drainage infrastructure is buried lines or pipe. Data identifying
the location, type of pipe, and other attributes is not fully collected. Catch basins are cleaned on a
5-year rotation.
CartêGraph software is a GIS tool with maintenance-related functions, and is currently being
used as the CMMS for the City. Two of the functions currently being implemented include
management of customer service requests and work order generation.
Building on this basic knowledge of current practices, Chapter 7 provides recommendations for
improvements to the current system, working toward a more criticality-based maintenance program.
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P:\135347 Auburn Drainage Phase II\009 Storm Drainage Comprehensive Plan\Final\Auburn Drainage Plan Final Dec09(v2).doc
CITY OF AUBURN COMPREHENSIVE
STORMWATER DRAINAGE PLAN
6. CAPITAL IMPROVEMENTS
This chapter describes recommended capital improvement projects for the city of Auburn storm
drainage utility. Capital improvement projects described in this chapter are compiled into a 6-year
CIP that addresses the most crucial drainage problems and a 20-year CIP that addresses more long-
term capital planning goals (see Chapter 7). This comprehensive plan contains time frames which are
the intended framework for future funding decisions and within which future actions and decisions
are intended to occur. However, these time frames are estimates, and depending on factors involved
in the processing of applications and project work, and availability of funding, the timing may
change from the included time frames. The framework does not represent actual commitments by
the city of Auburn which may depend on funding resources available.
In general, capital improvement projects are modifications to stormwater drainage infrastructure
designed to improve the condition and function of the drainage system so that it can meet the LOS
goals established for the City’s stormwater utility (see Chapter 3). Example goals include limiting
flooding across roadway segments to an average of once per 25 years and limiting the number of
pipes that have exceeded their economic lives (prior to repair or replacement). All projects were
developed and sized to be consistent with these LOS goals.
The capital improvement projects presented in this chapter were identified and developed through
focused investigations (see Chapter 3) and by working collaboratively with City staff. This focused
and collaborative approach was based on the practical consideration that the City can only
implement two to four capital improvement projects per year given existing revenue streams and
staff availability. The intent is to produce an economical CIP that addresses the most salient issues in
the near term, while still planning for the long-term ability of the stormwater utility to meet LOS
goals. The following are basic steps used to develop capital improvement projects:
The project team worked closely with City staff to identify and characterize existing problems
based on direct staff observations from recent storm events. Such observations are a valuable
supplement to modeling analyses, and in this case, were used in conjunction with modeling
activities to assist with model calibration.
Given knowledge of existing problems, the project team identified high-priority areas defined by
the drainage sub-basin. This allowed the project team to conduct focused investigations on these
known problem areas.
A detailed system inventory was completed for high-priority sub-basins prior to hydraulic
modeling investigations to ensure accurate sizing of project components (see Section 4.2 for a
discussion of sub-basin priorities).
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
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Hydraulic modeling was completed using MIKE URBAN, a software package that uses GIS
technology to import and export data, allowing a seamless transition between the system
inventories and modeling input files.
Modeling was completed for several historical flooding events, including the event that most
closely produced a once per 25 year flow rate (the specific event varied by basin). Results from
historical events were used to fully assess the extent and severity of the drainage problem. Results
from the design event were used to size infrastructure improvements designed to mitigate
flooding.
Recommendations were developed for flow and water level monitoring in the vicinity of each
proposed project. Data available at the time of this planning effort were limited for the purposes
of calibrating a detailed hydraulic model. Monitoring data collected specifically for that purpose
will allow the hydraulic models to be refined as part of predesign studies, which will provide a
better understanding of the problem and project size requirements. This refinement effort could
potentially result in lower capital costs than those included in this section, if the data collection
program and analysis shows the facilities could be built smaller than indicated with the limited
data.
Members of the City’s staff have a thorough understanding of the stormwater drainage system
and firsthand experience with existing drainage problems. The project team maintained close
communication with City staff to identify the most viable mitigation alternatives.
Once the mitigation alternatives were defined, the project team developed concept-level costs for
each project.
An overview of project locations is shown in Figure 6-1. Following the figure, Section 6.1 describes
a tiered method for establishing project priorities. Section 6.2 summarizes ongoing projects. Section
6.3 presents detailed descriptions of new proposed projects. Section 6.4 describes programmatic and
long-term planning efforts. Section 6.5 examines the need for repair and replacement of existing
pipes.
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1
6
9
T
H
A
V
E
E
S 287TH ST
3RD AVE S
5TH AVE SW
E ST NE
142ND AVE E
S 316TH ST
H
A
R
V
E
Y
R
D
S
C
E
N
I
C
D
R
S
E
H ST NW
M
A
I
N
S
T
S 292ND ST
WEST BLVD (BOEING)
44TH ST NW
3RD AVE SW
118TH AVE E
10TH ST NE
CLAY ST NW
4TH AVE SW
148TH AVE E
7TH ST SE
137TH AVE E
2
6
T
H
S
T
E
136TH AVE E
SE 310TH ST
S 3RD AVE
THORTON AVE SW
2
0
0
T
H
A
V
E
E
17TH ST E
BOUNDARY BLVD
L E A H I L L R D S E
32ND ST E
118TH AVE SE
58TH AVE S
ALGONA BLVD N
104TH AVE SE
S 372ND ST
J ST NE
ROY RD SW
4TH ST NE
PACIFIC AVE S
110TH AVE SE
14TH ST NE
D
R
I
V
E
W
A
Y
SE 281ST ST
160TH AVE SE
126TH AVE E
72ND AVE S
56TH PL S
25TH ST E
BRIDGET AVE SE
I ST SE
57TH AVE S
S 328TH ST
DOGWOOD ST SE
2ND AVE SW
8TH ST SE
S 279TH ST
T ST SE
F ST SE
FR O NTAG E R D
C
O
T
TA
G
E
R
D
E
S 358TH ST
FOSTER AVE SE
52ND AVE S
SE 274TH S T
166TH AVE E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
49 TH S T NE
S 362ND ST
I
S
T
N
W
54TH AVE S
A ST SW
57TH PL S
U
S
T
N
W
32ND ST NE
7
8
T
H
A
V
E
S
3RD ST E
D
E
E
R
I
S
L
A
N
D
D
R
E
135TH AVE SE
4 7 T H S T S E
2
0
4
T
H
A
V
E
E
28TH ST NE
8
6
T
H
A
V
E
S
S 356TH ST
R ST NW
27TH ST E
15TH ST E
28TH ST E
MILITARY RD S
13TH ST E
K ST SE
OLIVE AVE SE
10TH ST E
10
8T
H AVE E
SE 323RD PL
B ST SE
WYMAN DR
26TH ST SE
S 336TH ST
ST PAUL BLVD
S 340TH ST
C ST SE
B ST NE
32ND ST SE
S 300T H ST
1ST AVE S
36TH ST SE
ELM LN
SE 301ST ST
2
0
8
T
H
A
V
E
E
SE 287TH ST
V ST NW
2ND ST SE
23RD ST SE
4TH AVE S
QUINCY AVE SE
21ST ST NE
1
5
6
T
H
A
V
E
E
140TH AVE E
HEMLOCK ST SE
1
8
4
T
H
C
T
E
5
6
T
H
A
V
E
S
59TH AVE S
SE 298TH PL
30TH ST SE
S 318TH ST
24TH ST SE
2ND AVE S
14TH ST E
H ST NE
S 324TH ST
PIKE ST NW
21ST ST E
31ST ST E
42ND ST NW
6TH AVE SW
119TH
AV
E E
SE 286TH ST
55TH PL S
SE 276TH PL
SE 295TH PL
G ST NE
2 7T H ST SE
5TH AVE N
SKINNER RD
128TH AVE E
S 354TH ST
S 344TH ST
SE 364TH ST
SE 290TH ST
10TH ST SE
D ST SW
SE 280TH ST
2
1
1
T
H
A
V
E
E
NATHAN AVE SE
V ST SE
1
0
4
T
H
P
L
S
E
HI CREST DR
B PL NW
SE 294TH ST
72 N D ST SE
S 285TH ST
6TH ST NW
146TH AVE SE
SE 293RD ST
3RD ST NW
126TH AVE SE
I
S
A
A
C
A
V
E
S
E
S 3 1 2 T H S T
ELM ST SE
CLAY ST
S 370TH ST
20TH ST E
7TH ST E
19TH DR NE
SE 307TH PL
5 1 S T S T S E
10TH AVE N
S 364TH ST
140TH AVE SE
28TH ST SE
15TH ST SE
133RD AVE SE
108TH AVE SE
73RD ST SE
SE 295TH ST
4TH ST SW
26TH ST NE
S 366TH ST
SE 297TH ST
2
1
0
T
H
A
V
E
E
66TH ST SE
24TH ST NE
SE 296TH ST
SE 285TH ST
S 368TH ST
ALDER LN S
117TH AVE SE
U ST SE
110TH PL SE
A S T E WARD AVE SE
156TH AVE SE
WESTERN AVE NW
21ST ST SE
R PL NE
117TH AVE E
105TH AVE SE
7TH ST
5TH ST NE
53RD AVE S
HEATHER AVE SE
F ST N
E
11
2T
H
PL SE
51ST PL S
SE 292ND ST
D PL SE
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
123RD AVE E
63RD PL S
2ND CT NW
1ST ST NE
R ST NE
129TH PL SE
S 342ND ST
26TH ST NW
SE 321ST PL
114TH PL SE
RAMP
S 277TH ST
8TH ST NE
S 292 N D ST
TBD
200TH AVE E
SE 296TH ST
D
RIV
E
W
A
Y
13TH ST E
SE 282ND ST
R A M P
TBD
T B D
148TH AVE SE
144TH AVE SE
TBD
SE 301ST ST
RAMP
124TH AVE SE
SR 167
R A M P
5 1 S T S T S E
RAMP
RAMP
M S
T NW
RAMP
RAMP
21ST ST E
51ST AVE S
108TH AVE SE
142ND AVE E
SR 18
R ST NW
SR 167
16TH ST E
D ST SE
SE 284TH ST
S R 1 8
T B D
DRIVEWAY
SR 167
SE 292ND ST
R A M P
SR 167
12TH ST E
TBD
104TH AVE SE
9TH ST E
RAMP
H ST NE
108TH AVE E
108TH AVE E
55TH AVE S
K ST SE
32ND ST E
TBD
1ST AVE N
S 277TH ST
32ND ST E
8TH ST E
T
B
D
SR 167
53RD AVE S
M ST NE
C ST N
W
SR 18
TBD
R
A
M
P
17TH ST SE
R
A
M
P
110TH AVE SE
5 5 T H P L S
D
R
I
V
E
WAY
SE 274TH ST
TBD
TBD
24TH ST E
R ST NW
56TH AVE S
SE 282ND ST
8TH ST E
SR 167
SR 167
R A M P
TBD
TBD
SR 167
SE 272ND ST
51ST AVE S
26TH ST NE
TBD
SR 1 8
SE 272ND ST
TBD
SE 288TH ST
9
8
75
3
1
6
14
1615
13
11
12
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 4,000 feet
December 2009
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig6-1(projects).mxd
2,00002,0004,000
Feet [N
FIGURE 6-1
PROJECT LOCATIONS
STORMWATER UTILITY
CAPITAL IMPROVEMENTS PROGRAM
L E G E N D
!(Project Locations
Roadway
Auburn City Boundary
Water Body
Watercourse
Wetland
ID Project Name
1 R Street SE Storm Drain Improvement
2 SCADA (Telemetry) Upgrades*
3, 4 White River Storm Pump Station Replacement, Phases 1 & 2
5 Peasley Canyon Culvert Replacement
6 M Street NE/Harvey Road & 8th Street Improvements
7 Les Gove Neighborhood Improvement
8 West Valley Highway
9 Port of Seattle Mitigation Agreement Project
10 M&O Facility Improvements*
11 Relieve Auburn Way S Flooding
12 Bypass at 2nd and G Streets SE
13 Relieve 30th Street NE Area Flooding
14 Relieve West Main Street Flooding
15 South 296th Street South Pond Expansion
16 Bry’s Cove Pond Expansion
17 Storm Drainage Infrastructure Repair & Replacement*
18 Arterial Utility Improvements*
19 SOS Utility Improvements*
20 Regional Drainage Improvement Projects*
*Project not mapped; no specific location
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-5
Use of contents on this sheet is subject to the limitations specified at the end of this document.
6.1 Project Prioritization
The project team prioritized capital improvement projects through a collaborative effort led by
storm drainage utility staff. Projects were prioritized by grouping them into one of three tiers.
Projects in the top tier, or highest priority, are classified as tier 1; projects in the middle tier are
classified as tier 2; and projects with lowest priority relative to the other projects are considered tier
3. Prioritization was based on a qualitative evaluation of the following issues:
The magnitude of the LOS gap that would be addressed by a CIP project. For example, a project
that rectifies an annual flooding problem would rank higher than a project in a different area that
eliminates less frequent flooding.
The reduction in risk and reduction in consequences associated with a CIP project. For example,
the consequence of flooding that occurs near critical facilities (e.g., hospital or fire station) or
along major arterial streets may bring more serious consequences than flooding along residential
streets. A CIP project that addresses a larger consequence would rank higher.
The opportunity for coordination with ongoing city of Auburn street improvements, other utility
and transportation projects. Coordinated projects that reduce the overall cost of a CIP project
would rank higher.
The capital funding capacity of the storm drainage utility. The overall list of project priorities
attempts to balance the need for action with the funding and implementation capacity of the
storm drainage utility.
Other considerations included the potential to improve water quality, reductions in maintenance,
and increased reliability of the system.
Priorities for each project are included in each project description in the following sections. Project
priority and budgetary constraints were considered together in developing the year-by-year schedules
for project implementation in the 6-year CIP and 20-year CIP (see Chapter 7).
6.2 Ongoing Drainage Projects
Ongoing projects consist of those projects that have been identified through previous studies. The
City has already begun funding each of these projects, which are currently in various stages of
execution. These projects must continue to receive funding under the CIP until completion and
have been included in this document to provide a complete picture of the program. Ongoing
drainage projects are summarized in Table 6-1.
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-6
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Table 6-1. Summary of Ongoinga Capital Improvement Projects
CIP
project number Project name, description, and justification Priority
Total project cost
(2009 dollars)
1 R Street SE Storm Drain Improvement: The project will coordinate storm drainage
improvements with planned roadway and paving work along sections of R St. (21st to
25th St. SE) and 21st St. (R to K St. SE). Directs flow to existing pond at 21st and D St.
SE. Opportunity for improved LOS and reliability in project area at reduced unit costs.
Improved water quality discharge to Green River.
1 $770,000
2 SCADA (Telemetry) Upgrades: The SCADA/telemetry system needs upgrading. This
project will upgrade the portion of the system currently utilizing antiquated equipment
while maintaining the portions of equipment that are compatible with newer technologies.
The existing system, based on an independent SCADA Assessment Study and the
vulnerability study, has numerous obsolete components and does not allow control of the
sewer and storm utility stations. The new system will utilize an open architecture so that
the City is no longer reliant on one vendor for repairs and maintenance.
1 340,000
3 White River Storm Pump Station Replacement, Phase 1: Evaluation of upgrade,
refurbishment, or replacement of pump station based on the expected life and current
condition of the existing facility and equipment. The existing pump station is in poor
condition and requires upgrades/replacement to maintain overall system reliability.
1 300,000
4 White River Storm Pump Station Replacement, Phase 2: Evaluation of upgrade,
refurbishment, or replacement of pump station based on the expected life and current
condition of the existing facility and equipment. The existing pump station is in poor
condition and requires upgrades/replacement to maintain overall system reliability.
2 2,200,000
5 Peasley Canyon Culvert Replacement: Replacement of the existing Mill Creek culvert
at Peasley Canyon Rd. Existing culvert is in poor condition and has a high risk of failure
which would result in closure of a principal arterial.
1 1,000,000
6 M St. NE/Harvey Rd. & 8th St. Storm Drainage Improvements: Storm drainage R&R to
coincide with an ongoing roadway improvement project. Replacing aging infrastructure
using a “criticality model” will ensure drainage system reliability and allow the City to plan
out replacement costs over time. Annual budget allotment should be refined once the
criticality model is updated with more pipe data (e.g., material and age).
2 100,000
7 Les Gove Neighborhood Improvement: Storm drain R&R coincide with an ongoing
roadway improvement project. Opportunity for improved LOS and reliability in project area
at reduced unit costs.
3 200,000
8 West Valley Highway: Storm drainage improvements as part of a proposed roadway
widening project, including new conveyance structures, water quality and detention
facilities.
3 1,500,000
9 Port of Seattle Mitigation Agreement Project: Funds associated with the Port of Seattle
Mitigation Agreement are to be used for storm drainage improvements in the vicinity of
I St. NE, 40th St. NE and SE 277th St., including new conveyance structures, water
quality and detention facilities. Funds associated with this agreement expire in 2011.
1 600,000
10 M&O Facility Improvements: Anticipated upgrades to existing maintenance and
operations facilities.
2 300,000
Subtotal: Ongoing Capital Improvement Projects $7,272,000
a. Includes projects under way in 2009.
Information regarding the implementation of ongoing projects within the 6-year and 20-year CIP is
presented in Chapter 7.
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-7
Use of contents on this sheet is subject to the limitations specified at the end of this document.
6.3 Proposed Drainage Projects
Capital improvement projects described in this section were developed as part of this Drainage Plan
and are described in sufficient detail to allow the City to proceed with budgeting, design and
construction. Project descriptions are organized into summaries containing the following
information:
Project number: CIP numbers were assigned in sequential order as each project was developed
and do not signify a priority.
Project name: A short, descriptive name that was assigned to each project.
Project location: A simple description of the project location such as the cross streets is
provided.
Project priority and schedule: Project priorities and years of implementation are provided to
present complete project summaries; however, prioritization and scheduling is discussed in more
detail in Chapter 7.
Problem analysis and monitoring: A brief description of the observed problem is presented
along with a summary of the analysis conducted to characterize the problem and evaluate
alternatives for mitigation. In some cases, pre-project data collection and monitoring is proposed.
A more complete discussion of the hydraulic analyses performed to evaluate system conveyance
capacities is summarized in Section 5.1 and described in detail in Appendix D.
Project description: A description of the proposed project is provided, including major project
elements and sizes.
Planning-level cost estimates: A list of estimated costs is provided including construction
costs, engineering and administrative costs, land acquisition costs, taxes, and contingency costs.
Cost estimating assumptions are included in Appendix J.
Project map: A figure showing the conceptual design and location of project elements.
Proposed project summaries and figures are presented on the following pages.
THIS PAGE INTENTIONALLY LEFT BLANK.
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-9
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Project number: 11A (Phase 1)
Project name: Relieve Flooding at Auburn Way S and SR 18, Phase 1
Location: Flooding occurs on Auburn Way S, near SR 18.
Project would construct flow diversions upstream near 17th St. SE.
Priority: 1
Schedule: Begin construction 2009
Problem
summary:
The section of Auburn Way S near the SR 18 underpass frequently floods during large and/or intense rain
events. The low-slope, gravity storm drain adjacent to the underpass provides limited capacity for upstream
tributary flows. The nearby Auburn Way S pump station collects flow from six catch basins located in Auburn
Way S at SR 18 and a small drainage area to the southwest. The combination of the gravity and pumped
system is insufficient to meet flow demands. Downstream piping is also capacity-limited.
Description: Project Overview: This project would reduce stormwater flows to Auburn Way S at SR 18 by diverting
stormwater away from the flooding area. Water would be redirected by gravity flow into the existing
stormwater ponds located at 17th and A Streets SE, and 21st and D Streets SE. The diversion would be
accomplished by plugging north-flowing pipes along 17th St. SE. This diversion would force more stormwater
west along 17th St. SE to the pond at A St. SE thereby relieving the AWS system. This project would be
constructed in two phases as shown in Figure 6-2. A description and cost estimate for Phase 2 is included
following Figure 6-2.
Phase 1: The initial phase would intercept stormwater in the vicinity of Auburn Way S and 17th St. SE by
installing a control manhole to limit flow into the existing northwest flowing pipe. The control manhole would
redirect stormwater into new 24-inch diameter storm drain piping to the west along 17th St. SE, and then
south along K St. SE. At the intersection of K St. SE and 18th St. SE, the diversion flow would connect to the
existing storm drain that runs to the south in K St. SE. The combined stormwater flow would be conveyed to
the retention pond located at 21st St. and D St. SE. During Phase 1, the diversion flow would be limited to
available excess capacity in the existing storm drains in K St. SE and 21st St. SE; no additional capacity
would be required in this portion of the storm drainage network.
Phase 2: See description following Figure 6-2.
LOS goal(s)
addressed:
Flooding disruption that inundates the roadways to an impassable level no more than once every 25 years.
(LOS Goal 2)
Recommended
predesign
refinements:
Auburn staff should monitor flows downstream of the ponds to verify the proposed flow reduction is sufficient
to meet the street flooding LOS goal for Auburn Way S and SR 18. The model was only calibrated to limited
pond depth data and anecdotal flooding information. If necessary, additional detention could be incorporated
near B St. SE and 12th St. SE.
Cost estimate: Control structures (two) at 17th St. SE and M St. SE (vicinity); 17th St. SE and K St. SE ...............$30,000
Phase 1 Diversion pipe: 1,500 ft of 24-in.-diameter pipe................................................................................$209,000
Subtotal line-item costs.....................................................................................................................$239,000
Contractor overhead, profit and mobilization (18% of subtotal of line-item costs)............................$43,000
Washington State sales tax (9.5% of all above construction costs).................................................$27,000
Construction contingency (20% of all above construction costs)......................................................$62,000
Subtotal construction costs...............................................................................................................$371,000
Administration, engineering design and permitting (25% of construction costs)..............................$93,000
CIP 11A (Phase 1) project cost: $464,000a
a. The initial construction cost estimate for this phase came in at $400,000; however, the conceptual design cost estimate will be provided here for planning
purposes as a conservative estimate to cover additional costs that may arise during the completion of Phase 1.
THIS PAGE INTENTIONALLY LEFT BLANK.
COMPREHENSIVE STORMWATER DRAINAGE PLAN
December 2009
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig6-2(CIP11).mxd
FIGURE 6-2
PROJECT 11: RELIEVE FLOODING
AT AUBURN WAY S PUMP STATION
AND SR 18
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"
Upsize Pipe
(Phase 2)
"
17th and A Street Pond
Deepen pond +7 acre-feet
"
21st and D Street Pond
"
Modify
Regulator
(Phase 1)
Phase 1
Diversion
"
Flow Regulator
(Phase 2)
Phase 2
Diversion
"
Install New Pipe
(Phase 1)A
C
R
M
K
29th
17th
21st
A
u
b
u
r
n
F
25th
12th
L
D
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6th
J
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B
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5 t h
7th
SR 18
I
Aleshire
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9th
E
26th
15th
31st
23rd
30th
24th
N27th
10th
22nd
13th
8th
32nd
Elm
28th
14th
16th
Birch
Aspen
Unnamed
11th
20th
Pike
Dogwood
Cedar
Hopping
Transit
Easement
31st
31st
26th
6th
C
28th
C
23rd
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9 t h
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26th
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11th
8 t h
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F
[N
50005001,000
Feet
1 inch = 1,000 feet
L E G E N D
!(Storm Drain (Node)
Storm Drain (Pipe)
Pond
PHASE 1: DIVERT TO 21st ST POND
1) Install flow diversion manhole
2) Install 1,500 feet of new 24-inch diameter pipe (to K and 18th St SE)
3) Limit flow to available downstream capacity
PHASE 2: DIVERT TO 17TH AND A ST POND
1) Block all northwest flow at Auburn Way S and 17th St SE
2) Block all north flow along 17th St SE at J and B St SE
3) Upsize pipe in 17th St SE to 30-in diameter
4) Deepen 17th St and A Street SE pond to add 7 acre-feet of storage
back of Figure 6-2.
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-13
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Project number: 11B (Phase 2)
Project name: Relieve Flooding at Auburn Way S and SR 18, Phase 2
Location: Flooding occurs on Auburn Way S, near SR 18. Flow diversions would occur upstream near 17th St. SE.
Priority: 2
Schedule: Begin construction 2011
Problem
summary:
The section of Auburn Way S near the SR 18 underpass frequently floods during large and/or intense rain
events. The low-slope, gravity storm drain adjacent to the underpass provides limited capacity for upstream
tributary flows. The nearby Auburn Way S pump station collects flow from six catch basins located in Auburn
Way S at SR 18 and a small drainage area to the southwest. The combination of the gravity and pumped
system is insufficient to meet flow demands. Downstream piping is also capacity-limited.
Description: Overview: This project would reduce stormwater flows to Auburn Way S at SR 18 by diverting stormwater
away from the flooding area. Water would be redirected by gravity flow into the existing stormwater ponds
located at 17th St. SE and A St. SE, and 21st St. SE and D St. SE. The diversion would be accomplished by
plugging north-flowing pipes along 17th St. SE. This diversion would force more stormwater west along 17th
St. SE to the pond at A St. SE. This project would be constructed in two phases.
Phase 2: The follow-on phase would divert additional stormwater to the 17th St. SE and A St. SE pond by
plugging northward flowing pipes along 17th St. SE at J St. SE and B St. SE. To accommodate the
additional flow in 17th St. SE, the storm drain line would need to be upsized, from K St. SE west to A St. SE
(manhole B57). This project would also require deepening of the 17th St. SE and A St. SE pond. Once the
17th St. SE storm drain and pond improvements are complete, the diversion structure in the vicinity to M St.
SE and Auburn Way S would be modified to prevent any continued flow in the existing northwest flowing
pipe.
LOS goal(s)
addressed:
Flooding disruption that inundates the roadways to an impassable level no more than once every 25 years.
(LOS Goal 2)
Recommended
predesign
refinements:
See description of CIP 11A
Upsize pipe (24 to 30 in. diameter): 120 ft of pipe in 17th St. SE from B to A Streets SE (pond)......$21,000
Upsize pipe (to 30 in. diameter): 3,200 ft of pipe in 17th St. SE (see Figure 6-2)..............................$534,000
Add detention volume: add 7 ac-ft to 17th St. SE and A St. SE pond................................................$280,000
Control structure: new outlet structure for the 17th St. SE and A St. SE pond...................................$10,000
Subtotal line-item costs......................................................................................................................$845,000
Contractor overhead, profit and mobilization (18% of subtotal of line-item costs)..............................$152,000
Washington State sales tax (9.5% of all above construction costs)...................................................$95,000
Construction contingency (20% of all above construction costs).......................................................$218,000
Subtotal construction costs.................................................................................................................$1,310,000
Cost estimate:
Phase 2
Administration, engineering design and permitting (25% of construction costs)................................$328,000
CIP 11B (Phase 2) project cost: $1,638,000
Total CIP 11 project cost (Phases 1 and 2) $2,102,000
THIS PAGE INTENTIONALLY LEFT BLANK.
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-15
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Project number: 12
Project name: Bypass Piping at 2nd St. SE and G St. SE
Location: Street flooding in the vicinity of 2nd St. SE and G St. SE
Priority: 2
Schedule: Begin construction 2012
Problem
summary:
The existing storm pipe running northward in G St. SE between 4th St. SE and Main St. does not have
adequate capacity to convey upstream flows and local inflows. A total of 240 acres within sub-basin B drain
to the 30-inch diameter storm drain in G St. SE. Storm drainage capacity is further limited in the area,
because the manhole at G St. SE and 2nd St. SE has very little cover. Because the pipe is shallow,
moderate levels of surcharging could produce surface flooding that impacts the street intersection and
adjacent private property. This intersection is located in a localized low spot that collects stormwater from the
surrounding streets and adds this water to the overburdened pipe flowing northward in G St. SE. This
manhole is also bisected by a King County regional sewer line that produces a hydraulic constriction when
the City’s storm drain is surcharged.
Local residents described a history of flooding as part of a neighborhood planning effort. As recently as
December, 3, 2007, Auburn city staff observed manhole surcharging to within 2 feet of the surface. The staff
observations were made 6 to 8 hours after the local peak flow, so the maximum surcharge level was even
higher than was observed.
Description: This project would install a bypass pipe that would intercept upstream stormwater flows near 4th St. SE and
G St. SE and convey these flows in a parallel storm drain beyond the local low spot at 2nd St. SE and G St.
SE. The parallel line would dramatically reduce flow in the existing storm drain near the low point at 2nd and
G Streets. The local runoff that collects at 2nd St. SE and G St. SE would continue to flow downstream in the
existing storm main (north of 2nd St. SE). The existing storm main and the bypass pipe would connect two
blocks to the north at the intersection of G St. SE and Main St.
LOS goal(s)
addressed:
Flooding disruption that inundates the roadways to an impassable level no more than once every 25 years.
(LOS Goal 2)
Recommended
post-
construction
monitoring:
Monitor flow and water surface elevations in the vicinity of the reconnection point between the existing storm
drain and the bypass line to ensure the combined flows do not produce a backwater effect that surcharges
the existing storm drain at 2nd St. SE and G St. SE (see Appendix E, site Q-Pipe-C346). Periodic site
inspections by the maintenance crews during storm events would also be informative.
Cost estimate: Diversion pipe: 1,400 ft of 30-in.-diameter pipe.................................................................................$234,000
Subtotal line-item costs......................................................................................................................$234,000
Contractor overhead, profit and mobilization (18% of subtotal of line-item costs).............................$42,000
Washington State sales tax (9.5% of all above construction costs)...................................................$26,000
Construction contingency (20% of all above construction costs).......................................................$60,000
Subtotal construction costs................................................................................................................$362,000
Administration, engineering design and permitting (25% of construction costs)................................$91,000
CIP 12 project cost: $453,000
Potential funding
option:
Because the commercial businesses located along West Main St. would receive the primary benefit, the
City could explore implementing a Utility Local Improvement District (ULID) to fund this project.
6-16
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"
Install Bypass Pipe
J
F
D
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K
4th
IH
G
6th
5th
Ma i n
SR 18
2nd
1st
D
2nd
I
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I
1st
1st
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 300 feet
December 2009
L E G E N D
!(Storm Drain (Node)
Storm Drain (Pipe)
Pond
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig6-3(CIP12).mxd
FIGURE 6-3
PROJECT 12: BYPASS PIPING AT
2ND AND G STREETS SE
1500150300
Feet [N
back of Figure 6-3
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-19
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Project
number:
13 (Phases 1, 2, 3 described jointly)
Project name: Relieve 30th St. NE Area Flooding
Location: Street flooding in 30th St. NE between C St. NE and Auburn Way North; east of I St. NE between 32nd St. NE and 35th St.
NE; C St. NE between 30th St. NE and 37th St. NE
Priority: 1
Schedule: Phase construction with Phase 1 in 2013, Phase 2 in 2014, and Phase 3 in 2015
Problem
summary:
The north central area of Auburn has a history of surface flooding with significant flooding occurring about once every few
years. The December 3, 2007, storm event produced extensive flooding that included (a) inundation of 30th St. NE in the
vicinity of C St. NE, (b) extended duration of inundation near I St. NE adjacent to the CRISTA Ministries property and (c)
flooding along C St. NE northward toward 37th St. NE. The flooding on C St. NE required sandbagging to protect local
businesses. The flooding along 30th St. NE was high enough to overtop the sidewalk near the intersection. In addition to the
problems noted above, the gravity storm drain that runs eastward in 30th St. NE to the Brannan Park Pump Station does not
have enough capacity and surcharges frequently. The surcharging of the 30th St pipeline causes backups in contributing
systems, notably the City Airport and nearby private property. In addition, the residential development east of I St. NE
between 32nd St. NE and 35th St. NE commonly experiences prolonged periods of standing water due to high ground water
impacts from the Green River on its infiltration system.
Description: This project consists of separate upgrades that address flooding along 30th St. NE, C St. NE and I St. NE. The
implementation of these projects could occur in phases, as funding, staff availability, and CIP priorities allow.
Phase 1 would address the flooding along 30th St. NE. This project would install a new storm drain from the northwest
corner of the airport property (MH I107) to the existing Brannan Park storm pump station. This pipe would replace the
existing 30-inch diameter pipe generally located along the 30th St. NE alignment and the northerly boundary of Brannan
Park by improving the conveyance system’s hydraulic capacity, thereby reducing the potential for stormwater flooding into
the street. The pipe would be set at a consistent slope of 0.2 percent, which would increase flow velocities to help avoid the
current problems with siltation of the pipe and standing water. The proposed pipe alignment would follow the public right of
way until the pipe turns east from I St. NE toward Brannan Park. This portion of pipe would then be constructed within an
existing storm easement across public and private property. To reduce construction impacts to private properties, towards
the east end of the project the pipe could be located entirely within Brannan Park, to the north of the park’s ball fields. Some
tree removal may be necessary for construction within the park. Key components include:
3,820 feet of 42-in.-diameter gravity storm drain from the NW corner of airport property to the existing Brannan Park storm
pump station
Removal of floatable capture baffles upstream of the Brannan Park pump station (these are not needed to protect the
pumps and reduce the system’s hydraulic capacity)
Phase 2 would address the flooding adjacent to I St. NE. This project would locate a storm drain line to capture stormwater
from the two residential developments at the west edge for the former CRISTA Ministries property. Currently, stormwater
flows are discharged onto a depressed area on the CRISTA Ministries property where its infiltration is limited by high
groundwater levels that occur during extended periods of high flows on the Green River. The storm water ponds within the
parking of the two residential developments and presents a nuisance and potential hazard to local residents. This phase
would construct a new storm drain within I St. NE southward to connect into the upgraded 42-inch diameter (Phase 1) storm
drain near the intersection at I St. NE and 30th St. NE. The 42-inch diameter line would have sufficient available capacity to
convey the I St. NE flows. Key components of Phase 2 include:
1,760 feet of 15-inch diameter gravity storm drain
Catch basin and incidental grading to collect stormwater at the upstream end of system
Phase 3 would address flooding in C St. NE near 37th St. NE. Currently stormwater flows along C St. NE are conveyed and
discharged to Mill Creek via the 37th St. NE storm conveyance line. Deposition of sediment within Mill Creek has raised the
water levels within the creek and diminished the capacity of the gravity system in C St. NE and downstream in 37th St. NE.
This project would reduce flooding in C St. NE by redirecting wet weather high flows southward to the 42-inch diameter
(Phase 1) storm drain in 30th St. NE. By redirecting the C St. NE drainage into the Brannan Park system, these flows would
no longer be affected by high water levels in Mill Creek. To avoid deepening the Phase 1 gravity line (and extensive retrofits
to the Brannan Park pump station), this project would include a wet weather pump station and force main connection to 30th
St. NE. The upgraded 42-inch diameter pipe in 30th St. NE would have sufficient capacity for these additional flows. Key
components of Phase 3 include:
Wet weather pump station (estimated capacity of 4.5 to 7 cfs).
1,730 feet of 15-inch diameter force main
Diversion structure in C St. NE for pump station
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-20
Use of contents on this sheet is subject to the limitations specified at the end of this document.
This project would not require extensive modifications to the Brannan Park pump station. However, upon completion city
staff should consider lowering the level settings for pumps 4 and 5, since the hydraulic improvements will allow more
stormwater to reach the pump station.
LOS goal(s)
addressed:
Flooding disruption that inundates the roadways to an impassable level no more than once every 25 years. (LOS Goal 2)
Flooding causing property damage no more than once every 50 years (LOS Goal 3)
Recommended
predesign
refinements:
· Prior to implementing this project, city staff should conduct an additional review of the private stormwater facilities along
the C St. NE corridor to refine the design capacity of the proposed pump station.
Cost estimate:
Phase 1
Gravity storm drain: install 3,820 feet of 42-in.-diameter pipe from airport to Brannan Park PS ........................$1,584,000
Subtotal line-item costs ................................................................................................................................$1,584,000
Contractor overhead, profit and mobilization (18% of subtotal of line-item costs) ..............................................$285,000
Washington State sales tax (9.5% of all above construction costs) ................................................................$178,000
Construction contingency (20% of all above construction costs) ........................................................................$409,000
Subtotal construction costs................................................................................................................................$2,456,000
Administration, engineering design and permitting (20% of construction costs) .................................................$491,000
CIP 13A (Phase 1) project cost: $2,947,000
Cost estimate:
Phase 2
Gravity storm drain: install 1,760 feet of 15-in.-diameter pipe (along I St. NE to Phase 1 storm drain) .............$360,000
Subtotal line-item costs ................................................................................................................................$360,000
Contractor overhead, profit and mobilization (18% of subtotal of line-item costs) ..............................................$65,000
Washington State sales tax (9.5% of all above construction costs) ................................................................$40,000
Construction contingency (20% of all above construction costs) ........................................................................$93,000
Subtotal construction costs................................................................................................................................$558,000
Administration, engineering design and permitting (20% of construction costs) .................................................$112,000
CIP 13B (Phase 2) project cost $670,000
Cost estimate:
Phase 3
Stormwater pump station: 7-cfs pump station located C St. NE to the south of 37th St. NE ..............................$320,000
Force main: install 1,730 feet of 15-in.-diameter pipe (connect to Phase 1 storm drain) ................................$300,000
Subtotal line-item costs ................................................................................................................................$620,000
Contractor overhead, profit and mobilization (18% of subtotal of line-item costs) ..............................................$112,000
Washington State sales tax (9.5% of all above construction costs) ................................................................$70,000
Construction contingency (20% of all above construction costs) ........................................................................$160,000
Subtotal construction costs................................................................................................................................$962,000
Administration, engineering design and permitting (25% of construction costs) .................................................$192,000
CIP 13C (Phase 3) project cost $1,154,000
Total CIP 13 project cost (Phases 1, 2, 3) $4,771,000
G
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R
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John Reddington
J
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t
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Brannan ParkPump Station
PHASE 3New pump station in C St NENew 1,730lf force main in C St NE
PHASE 1:New 3,820lf 42-in drainagepipe in 30th St NE
PHASE 2:New 1,760lf 15-in drainagepipe in I St NE
I
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Aubu
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30th
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37th
15th
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42nd
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21st 21st
17th
M
D
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 1,000 feet
December 2009 (Revise d July 20 11)
P:\Auburn\138808 Au burn Modeling Suppor t On-Call (2010)\Task 091 - Reddington Levee Setback\GIS\MXD\AurburnStor m_CIP13_v2.mxd
FIGURE 6-4PROJECT 13: RELIEVE 30TH ST. NEAREA FLOODING50005001,000Feet N
LEGEND
Proposed Pump Station
Existing Pump Station
Proposed Drainage Pipe
Proposed Force Main
Existing Drainage Pipe
Pond
Project will relieve flooding to meet LOS #2 goal (25-yr flow capacity).
back of Figure 6-4
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-23
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Project number: 14
Project name: West Main St. Pump Upgrade
Location: West Main St. immediately south of the SR 167 overpass
Priority: 2
Schedule: Begin construction 2013
Problem
summary:
The dead-end portion of Old West Main St. near SR 167 has a history of observed flooding. The City installed a
temporary pump station to dewater the gravity pipe flowing in West Main St. and protect local businesses from
flooding; however, the pump station does not meet the City’s proposed LOS guidelines regarding pump
redundancy, and the pumps may not be large enough to convey the once per 25-year flow rate. In addition,
during wet years as stormwater builds in the ditch that runs along the east side of SR 167, there is the potential
for water to flow back toward the private properties that the temporary pump station was designed to protect.
Description: Pump station improvements are required to maintain sufficient drainage capacity near the west end of West
main St. The wet well of the pump station must be low enough to adequately drain the lowest catch basin at the
site of previous flooding, and the pump station must be sized to convey the peak 25-year flow rate with
discharge adjacent to, but outside the limits of the wetland located to the north of the overpass approach. These
improvements can be accomplished one of two ways:
1. The temporary pump station can be abandoned and a new pump station can be constructed.
2. The existing pump station can be modified to meet the capacity and redundancy requirements.
Additional hydraulic modeling is required to determine the preferred alternative; data must be collected to
calibrate the hydraulic model and obtain a more accurate estimate of the 25-year capacity. This will determine if
the temporary pump station can be utilized or if a new higher-capacity pump station is necessary. If the
temporary pump station is used, a second pump must be installed to meet the LOS goal 10 requirement for dual
pumps.
A force main from the new/modified pump station would be routed to the north side of the approach to the West
Main St. overpass and through the existing culvert under the overpass, if possible. At the force main discharge,
flows would be passed through an energy dissipation structure; if necessary, the flap gate in the ditch along SR
167 should be retrofitted to prevent backflow from the north side of the overpass back toward West Main St.
(i.e., the project should include hydraulic controls to prevent recirculation of stormwater). Key components
include:
· 20-cfs pump station (with dual pump redundancy) and force main conveyance to the north side of the Old
West Main St. overpass
· Hydraulic structures to prevent stormwater recirculation.
LOS goal(s)
addressed:
· Flooding disruption that inundates the roadways to an impassable level no more than once every 25 years.
(LOS Goal 2)
· Flooding (surface water from ROW runoff entering premises and damaging building structures) no more than
once every 50 years. (LOS Goal 3)
· Pump stations will be designed with two or more pumps to ensure proper function during maintenance.
Backup and/or dual-feed power supplies will be installed as needed. (LOS Goal 10)
Recommended
predesign
refinements:
· Conduct a thorough review of private drainage plans for the large commercial properties in the sub-basin.
This review should identify any additional onsite detention facilities that were not included in the large,
planning-level MIKE-URBAN model.
· Conduct flow monitoring upstream of existing, temporary pump station (see Appendix E, site Q-Pipe-P2).
Monitoring data will be used to improve the calibration of the hydraulic model, which is crucial to refining
conveyance requirements for the project and finalizing the required project elements.
· Evaluate site plans and stormwater detention potential to the south of West Main St. Together these activities
will enable a more detailed calibration of the storm drainage model and allow the city to refine the required
capacity of the new pump station to meet the street flooding LOS goal.
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-24
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Stormwater pump station: 20-cfs low-head pump station located in West Main St.............................$431,000
Gravity piping: redirect 300 ft of 12-in.-diameter pipe to new pump station location ...........................$35,000
Force main: construct new force main below underpass (from south to north side)...........................$70,000
Discharge structure: energy dissipation structure and swale to calm force main flows.......................$25,000
Ancillary improvements: decommission existing PS; flap gate to prevent back flow to W. Main St. $25,000
Subtotal line-item costs.......................................................................................................................$586,000
Contractor overhead, profit and mobilization (18% of subtotal of line-item costs)...............................$105,000
Washington State sales tax (9.5% of all above construction costs)....................................................$66,000
Construction contingency (20% of all above construction costs)........................................................$151,000
Subtotal construction costs..................................................................................................................$908,000
Cost estimate:
Administration, engineering design and permitting (25% of construction costs).................................$227,000
CIP 14 project cost $1,135,000
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"
Pump Station Improvements
"
Force Main and
Discharge Structure
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Existing Wetland
(Auburn Environmental Park)
"
Existing Drainage Ditch
C
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15th
D
A
SR 167
2ndClay
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3rd
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SR 167
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SR 18
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F
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2nd
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G
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 1,000 feet
December 2009
L E G E N D
!(Storm Drain (Node)
Storm Drain (Pipe)
Pond
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig6-5(CIP14).mxd
FIGURE 6-5
PROJECT 14
WEST MAIN STREET
PUMP STATION UPGRADE
50005001,000
Feet [N
back of Figure 6-5
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-27
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Project number: 15A, B (Phases 1 and 2 described jointly)
Project name: South 296th St. Pond Expansion, Phase 1
Location: West Hill area and Tributary 0047 to Mullen Slough
Priority: 1 (Phase 1) and 2 (Phase 2)
Schedule: Begin construction 2010 (Phase 1) and 2011 (Phase 2)
Problem
summary:
Several small streams drain water from the West Hill area down the valley wall and into Mullen Slough, which is a tributary
to Mill Creek. Mullen Slough exhibits flooding, sedimentation, and fish habitat problems. Erosion and transported
sediments from the streams draining off of West Hill can contribute to these receiving water problems. A stream
designated Tributary 0045 is of particular concern because an assessment of the stream found it to be highly unstable. As
the steam flows down the valley wall it enters into a steep ravine with an incised stream channel between 4 and 8 ft deep.
When the stream reaches the valley floor it transitions abruptly to a low-gradient channel, which causes sediments
deposition. A second stream (designated Tributary 0047) contributes flow to Tributary 0045 through an overflow drainage
pipe just north of South 296th St. near 54th Ct. South. The additional flow historically diverted from Tributary 0047 to
Tributary 0045 exacerbates erosive conditions.
Description: An existing stormwater facility on the south side of South 296th St. detains stormwater runoff leading to Tributary 0047.
Water is discharged from the existing stormwater facility under South 296th St. and into a wetland area on the north side of
the road. It is this wetland area where water is drained through the drainage pipe into the Tributary 0045 drainage basin.
Expanding South 296th St. detention facility would decrease stormwater runoff discharge rates as well as volumes to
Tributaries 0047 and 0045. The project will be built in two phases.
Phase 1: Modification to the existing outlet structure will provide additional detention storage. The pond would be
expanded from 4 ac-ft to approximately 8 ac-ft by excavating the bottom to increase storage capacity. In addition, a control
structure would be installed at the inlet of the drainage pipe leading to Tributary 0045. Both structures would include an
overflow weir and a low-flow orifice. Only minor earthwork would be required to prevent flooding of adjacent properties.
Phase 2: The existing stormwater facility would be expanded by approximately 8 ac-ft to 15 ac-ft. The outlet and pipe
under South 296th St. would need to be lowered to accommodate the lower pond bottom elevation. Some additional
earthwork would be required around the periphery of the pond to prevent flooding of adjacent properties. The pond
expansion would require the purchase of a vacant parcel to the south.
LOS goal(s)
addressed:
· Flooding disruption that inundates the roadways to an impassable level no more than once every 25 years. (LOS Goal 2)
· No erosion or landslides resulting from public drainage infrastructure construction, operation, or maintenance. No
stormwater discharge will be permitted on steep slopes. (LOS Goal 4)
· Flooding causing property damage no more than once every 50 years (LOS Goal 3).
Recommended
predesign
refinements:
· Recommendations for pond expansion are based on information obtained from the King County study (2008). No
additional analyses were completed as part of the development of this conceptual design. It is recommended that a
more-detailed hydrologic study be conducted to calculated flow-frequency for inflows to the ponds.
· Conduct automated stormwater depth monitoring within the pond (see Appendix E, site WL-Pond-04). The results of the
monitoring will (a) estimate existing infiltration capacity at the site and (b) refine the current estimate of stormwater flows
into the pond.
Pond excavation and associated earthwork: add 4 ac-ft of storage......................................................................$195,800
Outlet structure and other hydraulic improvements...............................................................................................$39,000
Subtotal line-item costs..........................................................................................................................................$234,800
Contractor overhead, profit and mobilization (18% of subtotal of line-item costs).................................................$42,000
Washington State sales tax (9.5% of all above construction costs).......................................................................$26,000
Construction contingency (20% of all above construction costs)...........................................................................$60,000
Subtotal construction costs....................................................................................................................................$362,800
Cost estimate:
Phase 1
Administration, engineering design and permitting (25% of construction costs)...................................................$91,000
CIP 15A (Phase 1) project cost: $453,800
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-28
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Pond excavation, associated piping (minor) and earthwork: add 7 ac-ft of storage..............................................$425,000
Land acquisition: 2 acres........................................................................................................................................$150,000
Subtotal line-item costs..........................................................................................................................................$575,000
Contractor overhead, profit and mobilization (18% of subtotal of line-item costs).................................................$104,000
Washington State sales tax (9.5% of all above construction costs).......................................................................$65,000
Construction contingency (20% of all above construction costs)...........................................................................$149,000
Subtotal construction costs....................................................................................................................................$893,000
Cost estimate:
Phase 2
Administration, engineering design and permitting (20% of construction costs)...................................................$179,000
CIP 15B (Phase 2) project cost: $1,072,000
Total CIP 15 project cost: $1,525,000
"
Expand Existing Pond
(Phase 1)
"
Additional Expansion
(Phase 2)
Tributary 047
"
Overflow
Drain Leading
to Tributary 045
"
New Outlet
51ST AVE S
S 296TH ST
S
2
9
7
T
H
P
L
55TH AVE S
52ND PL S
5
4T
H
C
T
S
S 297TH ST
296TH ST S
54TH PL S
5 3 R D P L S
53RD AVE S
S 298T
H CT
S 299TH CT
S 296TH CT
55TH
AVE S
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 250 feet
December 2009
L E G E N D
!(Storm Drain (Node)*
Storm Drain (Pipe)*
Pond
*Note: Inventory not complete
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig6-6(CIP15).mxd
FIGURE 6-6
PROJECT 15:
SOUTH 296TH STREET
POND EXPANSION
1250125250
Feet [N
back of Figure 6-6
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-31
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Project number: 16A, B (Phases 1 and 2 described jointly)
Project name: Bry’s Cove Pond Expansion
Location: West Hill area and Tributary 0045 to Mullen Slough
Priority: 2
Schedule: Begin construction 2010 (Phase 1) and 2014 (Phase 2)
Problem
summary:
Several small streams drain water from the West Hill area down the valley wall and into Mullen Slough, which is a tributary
to Mill Creek. Mullen Slough exhibits flooding, sedimentation, and fish habitat problems. Erosion and transported
sediments from the streams draining off of West Hill can contribute to these receiving water problems. A stream
designated Tributary 0045 is of particular concern because an assessment of the stream found it to be highly unstable. As
the steam flows down the valley wall it enters into a steep ravine with an incised stream channel between 4 and 8 ft deep.
When the stream reaches the valley floor it transitions abruptly to a low-gradient channel, which causes sediment
deposition.
Description: This project would reduce flows and sediment loads to Mullen Slough via Tributary 0045 by increasing the stormwater
detention capacity at the proposed Bry’s Cove pond. The project would be built in two phases.
Phase 1: An existing stormwater facility near 57th Pl. S and north of South 296th St. has additional storage capacity
available for detaining runoff leading to Tributary 0045. The pond would be expanded by excavating the bottom to increase
storage capacity. New outlet controls would be installed to maximize available detention storage.
Phase 2: Upon the completion of the Bry’s Cove Plat, an additional 14,000 sq ft of space is available on the parcel to the
north. The proposed project would utilize the open space and pond for Bry’s Cove located to the north and expand the
existing pond to increase the overall storage capacity.
LOS goal(s)
addressed:
· Flooding disruption that inundates the roadways to an impassable level no more than once every 25 years. (LOS Goal 2)
· No erosion or landslides resulting from public drainage infrastructure construction, operation, or maintenance. No
stormwater discharge will be permitted on steep slopes. (LOS Goal 4)
· Flooding causing property damage no more than once every 50 years (LOS Goal 3).
Recommended
predesign
refinements:
· Recommendations for pond expansion are based on information obtained from the King County study (2008). No
additional analyses were completed as part of the development of this conceptual design. It is recommended that a
more-detailed hydrologic study be conducted to calculated flow-frequency for inflows to the ponds.
· Conduct automated stormwater depth monitoring within the pond(see Appendix E, site WL-Pond-04). The results of the
monitoring will help (a) estimate existing infiltration capacity at the site and (b) refine the current estimate of stormwater
flows into the pond.
Pond excavation and associated earthwork: add 1 ac-ft of storage......................................................................$61,000
Outlet structure and other hydraulic improvements...............................................................................................$7,000
Subtotal line-item costs..........................................................................................................................................$68,000
Contractor overhead, profit and mobilization (18% of subtotal of line-item costs).................................................$12,000
Washington State sales tax (9.5% of all above construction costs).......................................................................$8,000
Construction contingency (20% of all above construction costs)...........................................................................$18,000
Subtotal construction costs....................................................................................................................................$106,000
Cost estimate:
Phase 1
Administration, engineering design and permitting (25% of construction costs)...................................................$27,000
CIP 15A (Phase 1) project cost $133,000
Pond excavation and associated earthwork: add 1.3 ac-ft of storage..................................................................$173,000
Outlet structure and other hydraulic improvements..............................................................................................$7,000
Land acquisition: 0.4 acres....................................................................................................................................$40,000
Subtotal line-item costs.........................................................................................................................................$220,000
Contractor overhead, profit and mobilization (18% of subtotal of line-item costs)................................................$40,000
Washington State sales tax (9.5% of all above construction costs)......................................................................$25,000
Construction contingency (20% of all above construction costs)..........................................................................$71,000
Subtotal construction costs...................................................................................................................................$356,000
Cost estimate:
Phase 2
Administration, engineering design and permitting (25% of construction costs)...................................................$89,000
CIP 16B (Phase 2) project cost $445,000
Total CIP 16 project cost $578,000
THIS PAGE INTENTIONALLY LEFT BLANK.
"
Tributary 045
"
Expand Existing Pond
(Phase 1)
"
Additional Expansion
(Phase 2)
"
New Outlet
S 296TH ST
59TH AVE S
57TH PL S
55TH AVE S
S 296TH PL
S 297TH ST
54
T
H C
T
S
54TH PL S
S
2
8
6
T
H
C
T
S 294TH ST
5
8
T
H
P
L
S
6
0
T
H
C
T
S
S
2
9
8
T
H
P
L
S 2 92 N D P L
61ST AVE S
S 296TH CT
55TH
AVE S
5
8
T
H
P
L
S
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 250 feet
December 2009
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig6-7(CIP16).mxd
FIGURE 6-7
PROJECT 16
BRY’S COVE
POND EXPANSION
1250125250
Feet [N
L E G E N D
!(Storm Drain (Node)*
Storm Drain (Pipe)*
Pond
*Note: Inventory not complete
back of Figure 6-7
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-35
Use of contents on this sheet is subject to the limitations specified at the end of this document.
6.4 Programmatic and Long-Term Drainage Planning Projects
To ensure an adequate level of utility funding in the future, the City must consider longer range
programmatic efforts to maintain and/or improve storm drainage service. The City must also
consider future regional drainage issues that cover a broader scope than the specific projects
described in the previous section (e.g., restoration and drainage improvements within Mill Creek).
Table 6-2 lists programmatic and long-term planning issues that should be included in the storm
drainage utility budget. These projects are not linked to any specific problem or location, but are
included for budgetary purposes. By itemizing these activities, the storm drainage utility can track
actual costs to compare with budgeted costs and specifically track how these expenditures address
the LOS goals listed in Chapter 3. The items listed in the table below are distributed between the
6-year CIP and 20-year CIP in Chapter 7.
Table 6-2. Summary of Ongoing and Long-Term Programs to Address Drainage Infrastructure
CIP
project number Project or program name and description Priority
Total project cost
(2009 dollars)
17 Storm Drainage Infrastructure Repair & Replacement: This item addresses the need
to repair or replace storm drainage infrastructure such as individual pipes, pump station
repair and maintenance, and pond improvements. The long-term priorities for repair and
replacement should be developed by adhering to LOS Goals 6–7 and 9 regarding the
maintenance of a criticality database and the prioritized assessment of critical
infrastructure.
LOS goal(s) addressed: Goal 8: “The City shall seek to repair or replace system assets
before they exceed their economic lives.”
1 $2,587,365
18 Arterial Preservation Utility Improvements: The storm drainage utility will seek
opportunities to incorporate drainage improvements into transportation and street
overlay projects on city arterials. By coordinating and cost-sharing with ongoing street
projects, the storm drainage utility can reduce the unit cost of storm drainage
infrastructure projects.
LOS goal(s) addressed: Goal 16: “The City shall continue to fund and provide storm
drainage services through the existing storm drainage utility.” Seeking opportunities to
implement drainage improvements at lower unit costs will help the storm drainage utility
remain within its funding limits.
3 $1,293,682
19 SOS Utility Improvements: Drainage infrastructure improvements associated with the
Save Our Streets program. Coordinating and cost-sharing with the SOS Utility program
can reduce the overall costs of implementing drainage improvement projects.
LOS goal(s) addressed: Goal 16: “The City shall continue to fund and provide storm
drainage services through the existing storm drainage utility.” Seeking opportunities to
implement drainage improvements at lower unit costs will help the storm drainage utility
remain within its funding limits.
3 $912,000
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-36
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Table 6-2. Summary of Ongoing and Long-Term Programs to Address Drainage Infrastructure
CIP
project number Project or program name and description Priority
Total project cost
(2009 dollars)
20 Long-term Drainage Improvements: This item establishes a budget for large-scale
future drainage improvements. Likely drainage improvement projects include:
· Mitigating impacts of Green River flooding. Current flood control limitations in the
Upper Green River could become a potential ongoing issue of concern for the Storm
Drainage Utility.
· Mitigating backwater flooding conditions along Mill Creek. Channel aggradation (i.e.,
rising stream channel) along Mill Creek could further limit the discharge capacity of the
gravity portion of the storm drainage system. This may also help to reduce flooding
along the Interurban Trail.
· Regional stormwater facilities for the downtown area. Redevelopment in the downtown
will need to meet current stormwater design standards; this may be better achieved
through regional facilities rather than distributed facilities due to the spatial constraints
of high-density land use. A study must first be completed to determine the best course
of action (see Chapter 7).
The budget value for this item reflects an assumed level of participation by the city of
Auburn. The actual level of participation should be determined in response to the
benefits of specific projects developed in collaboration with other regional planning
agencies.
LOS goal(s) addressed: The precise list must be determined for specific projects.
Likely goals addressed include Goals 1–3 (limiting flooding), 12 (protection of native
vegetation and drainage courses), and 15 (participation in regional planning efforts).
3 $7,579,637
6.5 Repair and Replacement
The 6-year CIP focuses mainly on existing flooding problems where recent storm events have
revealed deficiencies in the drainage system. Most of the capital improvement projects are designed
to mitigate flooding in these areas and are expected to provide substantial and immediate benefits.
As current problems are addressed in the near term, the focus of the CIP begins to shift from a
reactive program to a more proactive program, where repair or replacement of storm drainage assets
can be prioritized according to the optimal timing for interventions. Ultimately, this process will
allow the City to meet customer service levels, effectively manage risks, and minimize the City’s
costs of ownership.
6.5.1 Economic Life-Cycle Analysis Results
An economic life model containing data for the City’s stormwater drainage pipes was developed as
part of this Drainage Plan (see Section 5.2.1). The model was used to evaluate the condition of pipes
within the drainage system and identify repair and replacement needs.
There are a number of ways in which an organization can reactively or proactively address an asset
failure. For this economic life-cycle analysis, the intervention methods considered included open-cut
replacement of a pipe segment and, for segments for which it was deemed appropriate, lining of the
pipe segment. The analysis examined pipe characteristics (e.g., age, material, and length), as well as
the risks and consequences of failure and compared those results with repair and replacement costs
to determine optimal timing for intervention.
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-37
Use of contents on this sheet is subject to the limitations specified at the end of this document.
Given future intervention timing, a graph of projected spending for future years can be generated.
Figure 6-8 presents a long-term spending program for the stormwater collection system. As shown,
lining is generally the preferred intervention option because of the relatively young system age, but
full replacement may become more viable if updates on missing material type or capacity issues
preclude lining as an option. As the graph indicates, R&R spending needs are projected to increase
substantially beginning around 2050 and peaking near 2075.
$0.0 million
$0.4 million
$0.8 million
$1.2 million
$1.6 million
$2.0 million
20102060211021602210
Year
Co
s
t
Replacement Cost
Lining Cost
Figure 6-8. Future annual spending for repair and replacement given calculated optimal timing
6.5.2 Pipes Identified for Intervention
Because of the relatively young age of the surface water collection system, there are very few
segments identified for proactive intervention in the next decade. However, it should be noted that
the results of this initial analysis are only as good as the input data describing the pipes. As
infrastructure data are improved in the economic life model, more pipes may be identified for earlier
intervention (see recommended improvements in Section 6.5.4 and recommendations for updating
the criticality database described in Chapter 7). To prioritize R&R projects as they become more
frequent in the future, a benefit/cost ratio was also developed to identify interventions that would
result in the greatest savings for the lowest price. Benefit/cost was calculated as the ratio of the risk
cost carried by the existing asset divided by the minimum annualized cost of ownership of the
intervention. Therefore, segments with a benefit/cost ratio greater than or equal to 1 are appropriate
for intervention. In addition, a high benefit/cost ratio indicates a greater proportion of savings per
year for the cost of intervening. As multiple segments become due for intervention in the future, the
benefit-cost ratio can be used as a means to support prioritizing where finite R&R funds are spent.
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-38
Use of contents on this sheet is subject to the limitations specified at the end of this document.
The benefit/cost ratio tends to favor segments that are the most likely to fail (i.e., old segments with
poor condition scores) and relatively inexpensive to intervene (i.e., short, small-diameter segments).
Thus, high consequence, larger pipes that are expensive to replace could potentially show up too low
on an R&R priority list using benefit/cost. Because of the adjustment to the probability of failure
based on pipe length and the increase in consequence cost based on diameter, the long, large-
diameter segments will still be identified for intervention at an appropriate age. However, sorting by
the consequence costs for segments identified for intervention would provide an alternative project
priority list that favors replacing large pipes first.
6.5.3 Pipes Identified for Conditional Assessment
The risk currently carried by each pipe provides a justification for focused conditional assessment
activities (e.g., closed-circuit television inspections) as part of a risk-based maintenance strategy. In
general, risk-based maintenance strategies recommend predictive maintenance and risk mitigation
practices for high risk assets, preventive and routine maintenance for medium risk assets, and
routine maintenance or even a “run-to-failure” approach for low risk assets.
As an example, Figure 6-9 shows the relative risk of pipes within the City’s drainage system sorted
into three categories; red segments are the top 20 percent of the City’s length of pipe in terms of
risk, yellow segments are the next 30 percent of the City’s length of pipes, and the green segments
are the bottom 50 percent. Pipes carrying the highest risk can be flagged for condition assessment or
other predictive maintenance activities. For assets that are not carrying as much risk (yellow and
green segments in Figure 6-9), maintenance activities can be modified to better fit the criticality of
each individual segment. For some segments this may mean reducing the number of inspections, but
for others it could mean increasing the frequency of maintenance activities.
6.5.4 Recommended Improvements for Economic Life-Cycle Analyses
The results from the economic life model are only as accurate as the inputs. Improving the accuracy
of the information on which the model is built is the main area for improvement. The data input
improvements can be organized into three groups of information as follows:
Cost assumptions: Verifying the cost information for the consequence parameters, spot repair
costs, and intervention costs will ensure that the model is calculating accurate intervention
timings and that cost projections represent an accurate spending program. The costs presented
here were generated based on Brown and Caldwell’s experience with cities similar to Auburn.
Therefore, continually verifying and customizing these costs to reflect Auburn’s surface water
collection system are important to generate accurate results.
Failure trending: The probability of failure used in the economic life model presumes that the
City’s segments will fail in a manner described by a specific type of statistical distribution. Such a
statistical distribution can be customizable to meet a variety of conditions that influence failure;
however, verifying the parameters used to describe the distribution will require trending of actual
failure rates. With this information, the probability function can be customized specifically to the
Auburn stormwater utility and will better predict optimal intervention timing.
Need for additional information: The economic life model is based on data inputs from a
criticality database containing data describing current conditions of stormwater infrastructure.
6: Capital Improvements COMPREHENSIVE STORMWATER DRAINAGE PLAN
6-39
Use of contents on this sheet is subject to the limitations specified at the end of this document.
The completeness and accuracy of these input data are crucial to the usefulness of the economic
life-cycle analysis results.
The economic life model is designed to be a “living document,” with yearly updates of the internal
data. As the model is improved and more information becomes available the modeling results can be
revised and additional pipes can be identified for intervention. Specific instructions for updating the
economic life model are contained in Appendix F.
THIS PAGE INTENTIONALLY LEFT BLANK.
L a k e
T a p p s
B i g S o o s C r e e k
Mill Creek
R i v e r
G
r
e
e
n
R
i
ver
M
i l l
C
r e e k
Creek
Mill
G
r
e
e
n
R
i
v
e
r
G
r
e
e
n
River
W h i t e
G
r
e
e
n
R i v e r
Soosette
Creek
River
W
h i t
e
B o w m a n
C
r
e
e
k
W h i t e
R iv e r
R i v e r
White
Lake
M
u
l
l
e
n
S
l
o
u
g
h
Green
R iv e r
Lake
Meridian
W h i t e
S
R
1
6
7
S R 1 8
A ST SE
C ST SW
A
U
B
U
R
N
W
A
Y
S
B ST NW
I ST NE
AUBURN WAY N
R ST SE
132ND AVE SE
RA M P
WEST VALLEY HWY NW
M ST SE
8TH ST E
E MAIN ST
24TH ST E
124TH AVE SE
EAST VALLEY HWY SE
JOVITA BLVD
122ND AVE E
BUTTE AVE
S 384TH ST
110TH AVE E
15TH ST SW
SE 288TH ST
2ND ST E
C ST NE
SE 312TH ST
S 277TH ST
W MAIN ST
15TH ST NW
C ST NW
198TH AVE E
53RD ST SE
9TH ST E
29TH ST SE
GREEN VALLEY RD
1
7
9
T
H
A
V
E
SE 320TH ST
114TH AVE E
116TH AVE SE
EDWARDS RD E
LAKE TAPPS PKWY SE
41ST ST SE
WEST VALLEY HWY SW
S T U C K R I V E R D R
16TH ST E
K
E
R
S
E
Y
W
A
Y
S
E
147TH AVE SE
4TH ST E
18TH ST E
M ST NE
12TH ST E
SE 304TH ST
1
9
0
T
H
A
V
E
E
112TH AVE E
3RD AVE SE
ELLINGSON RD SW
37TH ST SE
PERIMETER RD
SE 272ND ST
4
6
T
H
P
L
S
8TH ST NE
182ND AVE E
37TH ST NW
ACADEMY DR SE
SE LAKE HOLM RD
22ND ST NE
L
A
K
E
L
A
N
D
H
I
L
L
S
W
A
Y
S
E
O R A V E TZ R D S E
VALENTI
NE AVE SE
C
U
T
O
F
F
51ST
AV
E S
SE 282ND ST
144TH AVE SE
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
55TH AVE S
1
8
5
T
H
A
V
E
E
214TH AVE E
D ST SE
1ST AVE SE
TACOMA BLVD
D ST NW
A ST NE
4TH ST SE
TBD
CELERY AVE
30TH ST NE
10
8T
H AVE
EAST BLVD (BOEING)
112
T
H AVE SE
SE 316TH ST
148TH AVE SE
T
A
C
O
M
A
P
O
I
N
T
D
R
E
A
U
B
U
R
N
-
E
N
U
M
C
L
A
W
R
D
55TH ST SE
E
V
E
R
G
R
E
E
N
W
A
Y
S
E
EMERALD DOWNS DR NW
D ST NE
M ST NW
O ST NE
S
E
3
6
8
T
H
P
L
W ST NW
1
6
9
T
H
A
V
E
E
S 287TH ST
3RD AVE S
5TH AVE SW
E ST NE
37TH ST NE
142ND AVE E
S 316TH ST
H
A
R
V
E
Y
R
D
S
C
E
N
I
C
D
R
S
E
H ST NW
M
A
I
N
S
T
S 292ND ST
WEST BLVD (BOEING)
44TH ST NW
3RD AVE SW
118TH AVE E
10TH ST NE
CLAY ST NW
4TH AVE SW
148TH AVE E
7TH ST SE
137TH AVE E
2
6
T
H
S
T
E
136TH AVE E
SE 310TH ST
S 3RD AVE
THORTON AVE SW
2
0
0
T
H
A
V
E
E
R I V E R D R
BOUNDARY BLVD
L E A H I L L R D S E
32ND ST E
118TH AVE SE
58TH AVE S
ALGONA BLVD N
104TH AVE SE
S 372ND ST
J ST NE
ROY RD SW
4TH ST NE
PACIFIC AVE S
110TH AVE SE
14TH ST NE
D
R
I
V
E
W
A
Y
SE 281ST ST
126TH AVE E
5TH ST SE
72ND AVE S
56TH PL S
25TH ST E
BRIDGET AVE SE
57TH AVE S
S 328TH ST
DOGWOOD ST SE
2ND AVE SW
8TH ST SE
S 279TH ST
L
S
T
S
E
T ST SE
F
ST
S
E
FR O NTA G E RD
C
O
T
TA
G
E
R
D
E
FO
ST
E
R
A
V
E
S
E
52ND AVE S
SE 274TH S T
1ST ST E
166
TH
A
V
E
E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
4 9TH S T NE
S 362ND ST
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23RD ST SE
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31ST ST E
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24TH ST NE
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A
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S
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19TH ST SE
6TH ST SE
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105TH AVE SE
7TH ST
5TH ST NE
53
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D A
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A
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P
L
S
SE 292ND ST
D PL SE
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
123RD AVE E
63RD PL S
THORTON PL SW
2ND CT NW
1ST ST NE
129TH PL SE
6TH ST NE
3RD ST NE
O C
T
S
E
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114TH PL SE
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TB
D
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148TH AVE SE
RAMP
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32ND ST E
RAMP
106TH AVE E
SE 274TH ST
SR 167
R ST NW
17TH ST SE
D
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E
W
A
Y
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RAMP
RAMP
SR 167
TBD
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RAMP
RAMP
T
B
D
SR 167
SE 272ND ST
TBD
S 277TH ST
R
A
M
P
108TH AVE E
M ST NE
DRIVEWAY
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SR 18
SR 18
H ST NE
RAMP
R A M P
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21ST ST E
144
T
H
AV
E
S
E
SE 282ND ST
T
B
D
R A M P
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16TH ST E
55TH AVE S
TBD
D
R
I
V
E
WAY
108TH AVE E
S 277TH ST
10
8
TH
A
VE
S
E
R AM P
51ST AVE S
13TH ST E
8TH ST E
5 1 S T S T S E
TBD
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32ND ST E
R
A
M
P
24TH ST E
5 5 T H P L S
51ST AVE S
SR 167
RAMP
104TH AVE SE
12TH ST E
SE 284TH ST
2ND ST SE
RA
M
P
D ST SE
26TH ST NE
SE 272ND ST
TBD
124TH AVE SE
R ST NW
9TH ST E
V ST SE
TBD
8TH ST E
1ST AVE N
S R 1 8
T B D
TBD
SE 282ND ST
200TH AVE E
R A M P
R A M P
R A M P
TBD
TBD
110TH AVE SE
SR 167
8TH ST NE
C ST N
W
T
B
D
RAMP
TBD
COMPREHENSIVE STORMWATER DRAINAGE PLAN
1 inch = 4,000 feet
December 2009
P:\135347 Auburn Drainage Phase II\GIS\MXD\Drainage Plan Figures\AurburnStorm_Fig6-9(ca priorities).mxd
2,00002,0004,000
Feet [N
FIGURE 6-9
PRIORITIES FOR CONDITION
ASSESSMENT OF STORM
DRAINAGE PIPES
L E G E N D
Roadway
Watercourse
Water Body
Wetland
Auburn City Boundary
Priorities based on Risk
Low Risk
Moderate Risk
Highest Risk
7-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
P:\135347 Auburn Drainage Phase II\009 Storm Drainage Comprehensive Plan\Final\Auburn Drainage Plan Final Dec09(v2).doc
CITY OF AUBURN COMPREHENSIVE
STORMWATER DRAINAGE PLAN
7. IMPLEMENTATION PLAN
This chapter presents the implementation plan, which brings together information from the
preceding chapters to form a work plan of future activities for the stormwater utility. The
information in this chapter serves as a roadmap to the storm drainage utility staff. This roadmap
outlines the critical elements of plan implementation (e.g., CIP implementation, stormwater
monitoring, asset management, and sustainability) and links them into a schedule of utility activities.
The implementation plan is divided into four sections:
Section 7.1 presents the CIPs for both 6-year and 20-year time frames.
Section 7.2 describes recommendations for future monitoring and data collection to support
predesign studies and future planning activities.
Section 7.3 contains a summary of activities for NPDES Permit compliance.
Section 7.4 makes recommendations for additional studies and activities.
The foldout chart at the conclusion of this section shows the proposed implementation timeline.
7.1 6-Year and 20-Year CIP
The 6-year CIP contains near-term capital improvement projects focused on mitigating the most
critical existing drainage problems that have been observed and are well understood by the City’s
staff. These projects are described in detail in Chapter 6. The 6-year CIP also contains ongoing
drainage projects that predate this Drainage Plan and will be completed within the next 6 years. In
addition to site-specific projects, the 6-year CIP contains ongoing programmatic efforts, such as the
drainage utility’s participation in the Save Our Streets program. Table 7-1 lists all 20 capital
improvement projects described in Chapter 6 and lays out annual expenditures for the 6-year CIP
time frame. Project timing is based on project priorities weighed with likely budgetary constraints
such that costs are distributed somewhat evenly from year to year (see Figure 7-1).
7:
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$0
$1,000,000
$2,000,000
$3,000,000
$4,000,000
$5,000,000
$6,000,000
200920102011201220132014
An
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Year
Priority 3
Priority 2
Priority 1 (Project)
Priority 1 (Programmatic)
Figure 7-1. Annual costs for 6-year CIP
Long-term stormwater conveyance demands should remain near current levels because unlike
wastewater planning where population growth brings additional flow demands, most new and
redevelopment projects will be subject to the City’s development standards for onsite
stormwater control. Local stormwater detention and integrated low-impact development (LID)
stormwater features should control stormwater flows to maintain approximate existing levels.
After existing drainage problems are addressed, the City will begin to shift its priorities away
from responding to known drainage problems toward managing existing storm drainage assets
to ensure that LOS goals are continuously met. These long-range capital improvements will
focus on programmatic activities, such as developing a repair and replacement schedule that
examines asset inspection and maintenance results to identify assets that are nearing the end of
their economic life.
Projects identified for 20-year CIP are less specific than the 6-year CIP projects. As new data
are collected and additional information is gathered, a better understanding of the problem will
be attained and the capital improvement projects will take shape. The following section provides
recommendations for activities that will assist with developing specific 20-year CIP projects.
Table 7-2 summarizes the project expenditures in the years 2015 to 2028 and forecasts total CIP
costs for the 20-year period from 2009 through 2028.
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Table 7-2. Cost Summary for 20-Year CIP
Project
number Project name Priority
Project costs for 2015–2028
(2009 dollars)
13C Relieve 30th St. NE Area Flooding, Phase 3 1 $1,154,000
17 Storm Drainage Infrastructure Repair & Replacement 1 5,600,000
10 Regional Drainage Improvement Projects 3 7,000,000
Total 2015–2028 CIP cost for priority 1 projects 6,754,000
Total 2015–2028 CIP cost for priority 2 projects 0
Total 2015–2028 CIP cost for priority 3 projects 7,000,000
Total CIP cost (2015 to 2028) $13,754,000
Total 20-year CIP cost $35,763,484
Even with the benefit of staff experience and detailed hydraulic investigations, the recommended
capital improvement projects reflect some uncertainty in the engineering calculations. To help
minimize uncertainty, 6-year and 20-year CIPs have been developed in conjunction with a
monitoring plan to obtain information that can be used in predesign studies to refine the sizing of
project components. The effort expended by the City to collect flow and level data to refine the CIP
elements will bring substantial benefits in reduced costs (as the engineering uncertainty envelope is
narrowed) and/or improved performance of CIP projects—and likely both. The monitoring plan is
included as Appendix E and summarized in the following section.
7.2 Monitoring
Evaluating the adequacy of the stormwater drainage system and analyzing potential capital
improvements require extensive data to produce accurate and reliable results. Such data include not
only infrastructure data such as pipe sizes, invert elevations, and outfall locations, but also
stormwater data such as flow rates, runoff volumes, and flooding elevations. The City should
continue to collect these types of data and store them in a consistent and organized manner. The
following sections describe specific recommendations for additional monitoring data collection.
7.2.1 Precipitation Monitoring
Precipitation is the source of stormwater runoff. Precipitation intensity and duration data are needed
to characterize rainfall-runoff processes and adequately design for drainage of stormwater runoff.
The City has been collecting precipitation data at city hall since 1995, and is currently using an Onset
model RG3 HOBO tipping bucket gauge to record precipitation data. The City should continue to
monitor precipitation at city hall using this equipment. However, an upgrade to telemetry-capable
equipment should be considered when the City’s data telemetry system is implemented (CIP Project
2), which is scheduled for 2009 and 2011. Integrating the rain gauge data into the telemetry system
will simplify data collection and minimize the chance of losing important data due to an undetected
equipment failure. It is also recommended that a manual rain gauge be kept as a backup and to
validate recorded data.
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7.2.2 Flow Monitoring
Flow data are used to gain a better understanding of the hydrologic and hydraulic conditions within
a drainage basin. Accurate measurement of flow provides both peak discharge estimates for sizing
conveyance capacity within the drainage network and runoff volumes for use in evaluating storm
drainage facilities and improvement projects. Several capital improvement projects are sized based
on hydraulic modeling analyses where model input parameters were adjusted until the simulation
reproduced observed conditions that were based on a limited set of anecdotal information. These
analyses can be improved by using newly collected flow data to perform addition model calibration,
which will enable engineers to refine the design of proposed project elements. Table 7-3 lists each of
the recommended flow monitoring sites, the corresponding CIP project, the recommended start
year, and the approximate duration of monitoring. Additional details are provided in Appendix E.
Table 7-3. Proposed Flow Monitoring Sites
Site number Location Purpose
Start
year
Approx.
duration
Q-Pipe-B4 Parking lot near Henry Rd. Provide data for hydrologic and hydraulic model
calibration (Basin B)
2010 1 to 2 wet
seasonsa
Q-Pipe-C346 G St. SE and 2nd St. SE Quantify flows to support modeling and design for
CIP Project 11 in Drainage Plan
2010 1 to 2 wet
seasonsa
Q-Pipe-B86 B St. SE and 12th St. SE Quantify flows to support modeling and design for
CIP Project 10 in Drainage Plan
2009 1 to 2 wet
seasonsa
Q-Pipe-C26 M St. SE and Auburn Way S Quantify flows to support modeling and design for
CIP Project 10 in Drainage Plan
2009 1 to 2 wet
seasonsa
Q-Pipe-C59 Dogwood St. near Auburn Way S Data to calibrate model for analysis of potential
capital improvement project
2011 1 to 2 wet
seasonsa
Q-Pipe-P2 Near West Main and SR 167 Quantify flows to support modeling and design for
CIP Project 13 in Drainage Plan
2010 1 to 2 wet
seasonsa
Q-Pipe-I10 30th St. NE near airport Quantify flows to support modeling and design for
CIP Project 12 in Drainage Plan
2009 1 to 2 wet
seasonsa
a. Data to support CIP needs at least one wet season of good data—approximately October through April; if sufficiently large storms occur during the first
season, then Year 2 data may not be necessary.
7.2.3 Water Level Monitoring
Water level data can also be useful for evaluating the performance of stormwater ponds and
assessing the risk of overtopping. Monitoring data can be used to estimate the potential untapped
capacity in a pond site, which will be particularly important for CIP projects 10, 14, and 15.
Monitoring other ponds will enable the City to identify changes in performance that may indicate
excessive sedimentation and the need for active maintenance. Additionally, water level monitoring in
Mill Creek will help the City establish a baseline from which to evaluate the impact of Mill Creek
water elevations to generate flooding in the storm drainage network.
The City should implement a water level monitoring program at selected sites to collect data for the
purposes described above. Because water level monitoring is less expensive than flow monitoring, a
broader ongoing water level monitoring program is more practical. Water level monitoring
equipment should be compatible with telemetric data systems such that each site can be integrated
into the City’s new telemetry system, wherever continuous power and data lines are available. Table
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7-4 lists each of the recommended water level monitoring sites, the purpose of the monitoring, the
recommended start year, and the approximate duration of monitoring. Additional details are
provided in Appendix E.
Table 7-4. Proposed Water Level Monitoring Sites
Site number Location Purpose Start year
Approx.
duration
WL-Mill-01 Mill Creek at 37th St. NW Evaluate stages in Mill Creek and assess backwater
effects on drainage system
2011 10 yearsa
WL-Mill-02 Mill Creek at 29th St. NW Evaluate stages in Mill Creek and assess backwater
effects on drainage system
2011 10 yearsa
WL-Mill-03 Mill Creek at 15th St. NW Evaluate stages in Mill Creek and assess backwater
effects on drainage system
2011 10 yearsa
WL-Mill-04 Mill Creek at West Main St Evaluate stages in Mill Creek and assess backwater
effects on drainage system
2011 10 yearsa
WL-Pond-01 West Airport Pond at 30th St. NW Evaluate pond capacity to support design analyses for
CIP Project 12 in Drainage Plan
2009 2 yearsb
WL-Pond-02 A St. SE and 17th St. SE Evaluate pond capacity to support design analyses for
CIP Project 10 in Drainage Plan
2009 Indefinitec
WL-Pond-03 D St. SE and 21st St. SEd Evaluate pond capacity to support design analyses for
CIP Project 10 in Drainage Plan
2009 Indefinitec
WL-Pond-04 South 296th St. near 55th Ave. S Evaluate pond capacity to support design analyses for
CIP Project 14 in Drainage Plan
2011 6 yearsc
WL-Pond-05 South 296th St. near 57th Pl. S Evaluate pond capacity to support design analyses for
CIP Project 15 in Drainage Plan
2012 6 yearsc
WL-Pond-06 U St. SE and 29th St. SE Evaluate pond capacity and infiltration rates to assess
need for improvements
2012 Indefinitec
WL-Pond-07 M St. SE and 37th St. SEd Evaluate pond capacity and infiltration rates to assess
need for improvements
2012 Indefinitec
WL-Pond-08 Lakeland South Pond 1 Monitor water level to evaluate hazard risk (dam safety) 2012 Indefinitec
WL-Pond-09 Lakeland South Pond 2 Monitor water level to evaluate hazard risk (dam safety) 2012 Indefinitec
WL-Pond-10 Lakeland East Pond Monitor water level to evaluate hazard risk (dam safety) 2012 Indefinitec
WL-Pond-11 Mill Pond (Oravetz Rd. SE) Monitor water level to evaluate hazard risk (dam safety) 2012 Indefinitec
a. Based on need to examine backwater effects on system; if new capital improvements are identified for Mill Creek, additional years may be needed.
b. Data to support CIP needs at least one wet season of good data; if this is accomplished in Year 1, then Year 2 data may not be necessary.
c. To be continually reevaluated; if data indicate that stormwater pond is performing adequately or has low risk of failure, then monitoring could cease.
d. Existing monitoring site; continue monitoring but consider equipment upgrades.
7.2.4 Water Quality Monitoring
The current NPDES Permit, which is effective through 2012, does not require stormwater
monitoring. However, the Permit does call for utilities to identify potential monitoring sites, with the
presumed intention of requiring monitoring in future permits. Refer to Section S8 of the current
NPDES Permit (Appendix A) for additional information.
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7.2.5 Monitoring Costs
Cost estimates have not been developed for the monitoring recommendations. Total costs will
depend on selected equipment (purchase or leasing), number of sites to be monitored concurrently,
staff resources and/or the need for hiring outside services. Refer to Appendix E for additional
discussion regarding approximate costs.
7.3 Programmatic Measures for NPDES Compliance
The city of Auburn is covered by the Western Washington Phase II Municipal Stormwater Permit
(Permit). The Permit regulates stormwater discharges from the City’s municipal stormwater system
(see Section 2.3.2). The current version of the Permit will remain in effect until February 2012, when
a new version is due to be issued.
The City has been actively engaged in compliance activities since the issuance of the Permit,
including the following seven major components of Permit activity:
Stormwater management plan administration
Public education and outreach
Public involvement
Illicit discharge detection and elimination
Control of runoff from development, redevelopment, and construction sites
Pollution prevention and municipal operation and maintenance
Monitoring.
Figure 7-2 shows a timeline for compliance with specific elements of the Permit. The specific
activities and requirements are described in detail in Appendix H.
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Begin keeping records for
inspections,
maintenance, and
enforcement
End of
First
Permit
Ma
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Effective
Fe
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Submit first SWMP and first
Annual Report to Ecology
and post on website
Begin tracking
Permit costs
Implement
public
education
program
Implement BMPs for municipal operations
Update codes, standards,
SOPs, inspections,
maintenance, and
documentation for
municipal operations and
public drainage system
O&M Complete storm
system map
Fully
implement
SWMP
Complete assessment of
outfall
Continue existing
programs
Begin hotline for
reporting illicit
discharges
Update codes, standards, SOPs, inspections, enforcement,
maintenance, and documentation for IDDE
Conduct responder IDDE training
Conduct general IDDE
training
Conduct municipal activities
training
Adopt new stormwater manual*Conduct controlling construction runoff training*
Develop SWPPPs for City
facilities
Implement monitoring
preparation requirements
Begin monitoring outfalls for illicit discharges
Update codes, standards, SOPs, inspections,
enforcement, maintenance, and documentation
for controlling construction runoff*
Acronym Key:
BMP: best management practice
IDDE: illicit discharge detection and
elimination
O&M: operation and maintenance
SOP: standard operating procedure
SWMP: stormwater management plan
SWPPP: Stormwater pollution prevention plan
Note:Requirements
marked with an asterisk
(*) were delayed from
August 16, 2009 to
February 16, 2010 per
permit modifications
dated June 17, 2009.
Select potential monitoring
locations.
Figure 7-2. Timeline for NPDES Permit compliance
The tools and activities required for NPDES compliance should be coordinated with other storm
drainage utility activities to maximize efficiency and consistency. For example, the monitoring
elements required later in the Permit cycle should benefit from the staff experience implementing
the monitoring plan (see Appendix E). Furthermore, the storm drainage utility should select
NPDES compliance monitoring equipment that is compatible with the CIP-related monitoring (e.g.,
same data loggers, communication software, and data processing software).
7.4 Recommendations for Additional Studies and Activities
Some of the problems identified during the development of this Drainage Plan will require
additional studies to better define the problem and evaluate alternatives before mitigation projects
and strategies can be identified. Other activities conducted as part of the development of this
Drainage Plan will require follow-up or continued improvements. The following sections present
recommendations for future studies and activities.
The following sections provide recommendations for additional studies and ongoing activities for
the stormwater utility. Sections 7.4.1 and 7.4.2 discuss the continued development of the system
inventory and asset criticality database, respectively. This is followed by Section 7.4.3, which
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presents a recommendation that a risk assessment be conducted to evaluate the vulnerability of
utility assets. Section 7.4.4 provides a discussion about ways to optimize the M&O program through
criticality-based strategies and use of the CMMS. Section 7.4.5 presents recommendations for
developing and incorporating sustainability goals with utility activities. Two of the problems
identified in Chapter 4 will require additional studies to better define the problems and evaluate
alternatives before mitigation projects and strategies can be identified; these are addressed in
Sections 7.4.6 and 7.4.7.
7.4.1 Continue System Inventory
One of the earliest tasks performed in preparation of this Drainage Plan was an assessment of
available infrastructure data, which primarily existed in two forms: GIS digital files and hydraulic
modeling digital files. The assessment found inconsistencies between the two data sources and
numerous data gaps (see Appendix D). These findings prompted an effort to produce a new and
updated set of infrastructure data files referred to collectively as a system inventory. These files were
developed using MIKE URBAN hydraulic modeling software, which stores geospatial information
that allows the data to be easily transferred from MIKE URBAN to common GIS software
platforms.
The magnitude of the system inventory effort required a phased approach (see Section 4.2).
Infrastructure within high-priority drainage sub-basins was inventoried first so that the results could
be used for hydraulic modeling and analyses of known flooding problems. Infrastructure data for
medium- and low-priority sub-basins were also updated; however, hydraulic modeling was not
performed. Infrastructure data were not updated for the remaining areas of the city. Therefore, it is
recommended that the data inventory task be continued as part of future activities.
The remaining sub-basins cover approximately 19.3 square miles and include sub-basins AAA, AZ,
BBB, CC, DD, EE, FF, GG, HH, II, JJ, KK, LL, M, MM, OO, NN, NNN, PP, RR, SS, UU, W,
WW, YY, YYY, ZZ, and ZZZ (see Section 4.2). Continuing the phased approach, the remaining
sub-basins can be divided into three geographic areas and completed over the next 3 years as
follows:
The West Hill area, which consists of sub-basins M, OO, NN, NNN, PP, RR, and SS, should be
completed in 2010.
The Lea Hill area, which consists of sub-basins AAA, AZ, BBB, UU, W, WW, YY, and ZZ,
should be completed in 2011.
The Southeast area, which consists of sub-basins CC, DD, EE, FF, GG, HH, II, JJ, KK, LL,
MM, YYY, and ZZZ, should be completed in 2012.
System inventory data should be continually updated and reviewed for quality control.
7.4.2 Update Criticality Database
Similar to hydraulic models, the economic life model described in Chapter 4 requires detailed input
data describing infrastructure components. These data are stored in an asset criticality database,
which should be developed and maintained in conjunction with the system inventory developed for
hydraulic modeling. Therefore, as new infrastructure data are added to the system inventory, data
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attributes should include both attributes required for hydraulic modeling and those required for
economic life-cycle analysis. Furthermore, regular updates and data checks should be made for
existing data to ensure its completeness and accuracy.
At present, a significant number of data points have not been included in the economic life model
because of a lack of sufficient data. This is evidenced by the distribution of pipe ages in the current
criticality database. Figure 7-3 shows a large gap in pipe ages between 91 and 100 years old and
between 41 and 50 years old, which indicates a 40-year window in which pipe data may not have
been tracked properly. Of the approximately 3,500 pipes in the criticality database at the time of the
economic life-cycle analysis, 15 percent of the pipes had no information regarding the age of the
pipe.
1075
1262
418
91 81
0000 27
540
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200
400
600
800
1000
1200
1400
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Age of Pipes (years)
Nu
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P
i
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Figure 7-3. Distribution of pipe ages based on the City's current criticality database
As the criticality database is improved the economic life model can be updated and R&R priorities
can be refined. The addition of this information will help improve the accuracy of the model and
better capture the risk costs carried by pipe segments. Additional information is needed for the
following areas:
Approximately 3,000 segments are catalogued as pipe material “unknown.”
Approximately 540 segments are missing installation dates.
Condition assessments and frequency of maintenance activities need to be recorded.
Approximately 300 segments are missing pipe diameter.
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Approximately 2,000 segments are missing depth-of-bury information.
Segments located within an easement or underwater need to be identified.
Segments not available for lining because they are already at peak capacity need to be identified.
Capacity information needs to be added based on hydrology and hydraulic modeling.
Additionally, although zoning information has been included in the model, more detailed zoning
information could be added in the future if such information is available. For example, although all
commercial zones were given the same consequence in this initial economic life-cycle analysis,
failures in a particular business core could be shown to cost more than failures in other commercial
zones.
7.4.3 Risk Assessment: Asset Vulnerability Analysis
Asset life-cycle analyses described in the previous section examine risk to individual assets, which
focus on small-scale modes of failure (e.g., pipe breakage). However, stormwater utility assets are
also vulnerable to failure caused by wide-scale events such as natural disasters. A utility must also
consider these risks and take action to mitigate those risks where feasible. Such actions could be in
the form of capital improvements or utility programs.
The City should conduct a vulnerability analysis on the entire stormwater drainage system to
examine the potential for natural disasters such as flood, erosion, earthquake or volcanic activity to
cause system failures. The associated probabilities of failure should be weighed with the
consequences of failure to determine if action is necessary and to identify appropriate mitigation
measures.
7.4.4 Evaluate Maintenance and Operations Program
M&O activities represent the remainder of large expenditures by storm drainage utilities after capital
costs. Therefore, optimizing these activities through an asset management program leads to
increased effectiveness in managing risk, public perception, regulatory compliance, and costs to the
utility. An evaluation of the M&O program will help to identify strategies for connecting staff
availability, characterizing critical assets, and prioritizing activities to ensure that the right assets are
receiving the correct maintenance based on an optimized schedule. Appendix H describes a
criticality-based approach to maintenance activities.
As part of the M&O evaluation, the City should explore expanding the functionality of CartêGraph
software. The City has purchased five modules to maximize the use of this tool; integrating the
software into the maintenance process will increase the accuracy of the data and the value of the
system.
7.4.5 Incorporate Sustainability
As the City implements this Drainage Plan, a need to prioritize projects and activities in a repeatable,
defensible manner will emerge. This process will need to have a standard method for evaluating all
of the LOS goals listed in Chapter 3, including goals related to sustainability.
Under the “protection of the environment” policy category in Table 3-1, the City has a policy to
evaluate drainage utility activities to emphasize sustainability. The goal associated with this policy is
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to identify specific areas to measure sustainability by examining how the storm drainage utility
operations affect energy resources and natural resources. The examples provided include items such
as weighing energy consumption impacts and costs during capital project development, selecting
biodegradable and locally produced cleaning and maintenance products, and structuring
maintenance and other activities to minimize vehicle miles traveled. However, quantifying these
goals and effectively utilizing information in decision-making can be challenging.
Traditionally, public works projects are evaluated on initial capital investments and the annual costs
of M&O. A project’s environmental and community benefits and costs are typically discussed, but in
many instances cost is the overriding decision criteria. By more rigorously including environmental
and community benefits and costs such as sustainability in the analysis, projects can be evaluated in a
manner that truly considers the full cost of ownership. The following actions are recommended to
develop and incorporate sustainability goals within the stormwater utility:
Define sustainability. Sustainability means different things to different people. To develop specific
goals, it is important to have a clear definition of the term. The United Nations-appointed World
Commission on Environment and Development defined sustainability as “development that meets
the needs of the present without compromising the ability of future generations to meet their own
needs.” The City must first agree upon and accept a definition of sustainability as it pertains to the
utility.
Develop sustainability goals. The challenge for the decision-maker is to take a general definition
and create discernible criteria that can be described and compared in a supportable way and used to
make defensible decisions. The City should strive to provide metrics around the specific
sustainability goals it would like to accomplish (e.g., instead of “minimize vehicle miles traveled,” the
metric would be “reduce vehicle travel by 20 percent”). Once LOS metrics are defined, projects and
activities can be evaluated in a repeatable fashion.
Establish a method of evaluation. The City should develop a consistent and repeatable method
for evaluating projects and activities. A recommended approach would be to develop an evaluation
process that builds upon the concept of life-cycle costing by also including consideration and
quantification, in economic terms, environmental and community impacts to determine the full cost
of a specific alternative. A quantitative approach such as this, considers environmental and
community risks and costs, which provides economic support for a decision at the management and
policy level.
The above actions provide a mechanism for incorporating sustainability into stormwater utility
activities in the same way other LOS goals are achieved. Investigations are conducted to evaluate
project and activities with respect to LOS criteria. Gaps are identified and alternatives are developed
for reducing or eliminating those gaps. Alternatives are evaluated by a life-cycle present value
benefit/cost analysis, considering not only budgetary impacts but also risks, environmental
considerations, and societal costs. By having a repeatable, defensible process that includes
environmental and community factors such as sustainability, the City can prioritize projects and
activities based both on full costs of ownership and on a project’s ability to meet or exceed LOS
requirements.
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7.4.6 Assist with Mill Creek Restoration Studies
Mill Creek is experiencing problems due to aggradation, decreased capacity, increased flood stages,
and varying degrees of water quality and habitat impairments. Most of these issues are being
addressed by the Green-Duwamish Ecosystem Restoration Project (ERP), which is a cooperative
effort by 16 local governments, Indian tribes, several regulating agencies, and other interested
parties. The ERP developed a list of 45 restoration projects for the watershed; several of which are
located within the city of Auburn. Two projects have recently proceeded into design phases: Mill
Creek Wetland 5K Reach Restoration and the 15th Street NW culvert replacement.
The city of Auburn has been an integral part of many of the ERP restoration projects, and it is
recommended that the City continue to be involved in this process. Restoring Mill Creek will not
only improve water quality and habitat, but could also improve flooding and drainage. As individual
projects become more developed, additional studies might be identified; the City could offer their
assistance with these new studies. For example, the City could use its planned monitoring effort in
Mill Creek to provide valuable hydraulic grade data to either demonstrate the need for channel
improvements or support the restoration design process.
7.4.7 Downtown Stormwater Control Study
In 2004, the area in the vicinity of downtown Auburn was designated as an urban center (DUC),
with plans to revitalize the area, consistent with state, regional, and local growth management
concepts. At that time, several incentives for developing within the DUC were created, some of
which pertained to stormwater management. For example, one of the incentives included the
“elimination of stormwater improvements for redevelopment of existing sites that do not result in
an increase in impervious surface.”
However, Auburn’s 2007 NPDES Permit contains new requirements that affect development
procedures within the City, including the DUC. One key change is that the City cannot exclude
development within the DUC from stormwater controls. In response to these changes, Auburn
should prepare stormwater development standards for the DUC so that the City can continue
providing incentives for redevelopment while meeting the NPDES Permit requirements.
The City should conduct a study of potential stormwater development standards that focuses on the
following options for stormwater controls:
Onsite water quality treatment options that can be incorporated into the planned landscaping or
buried below ground (e.g., cisterns, planters, bioretention, and vaults). These types of systems
would have no “effective footprint” and would follow LID principles. These systems may need
to be coupled with offsite flow detention systems.
Onsite water quality treatment and flow duration control options that incorporate LID principles.
This stormwater control approach would use the same types of BMPs as the approach above, but
the facilities would be sized to provide both treatment and detention.
Offsite stormwater control facilities (i.e., not located in the DUC) that would provide the
stormwater control requirements of the Permit without constraining the site development
process within the DUC.
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Phase 1
2009 2010 2011 2012 2013 2014 2015 2020 2025 2030
1. R Street SE Storm Drain Improvement
2. SCADA (Telemetry) Upgrades
3. White River Storm Pump Station Replacement, Phase 1
4. White River Storm Pump Station Replacement, Phase 2
5. Peasley Canyon Culvert Replacement
6. M Street NE/Harvey Road & 8th Street Improvements
7. Les Gove Neighborhood Improvement
8. West Valley Highway
9. Port of Seattle Mitigation Project
11. Improvements for Auburn Way S, SR 18 at M and 17th St.
12. Bypass at 2nd Street SE and G Street SE
13. Relieve 30th Street NE Area Flooding
14. West Main St. Pump Upgrade
15. South 296th Street Pond Expansion
16. Bry’s Cove Pond Expansion
17. Storm Drainage Infrastructure Repair & Replacement
18. Arterial Preservation Utility Improvements
19. SOS Utility Improvements
20. Regional Drainage Improvement Projects
Q1 Q2 Q3 Q4
Phase 1 Phase 2
Phase 2
Phase 1 Phase 2
Q-Pipe-B4. Parking lot near Henry Road
Q-Pipe-C346. G Street SE and 2nd Street SE
Q-Pipe-B86. B Street SE and 12th Street SE
Q-Pipe-C26. M Street SE and Auburn Way S
Q-Pipe-C59. Dogwood Street
Q-Pipe-P2. Near West Main and SR 167
Q-Pipe-I10. 30th Street NE near airport
WL-Mill-01,02,03,04. Mill Creek Profile
WL-Pond-01. West Airport Pond
WL-Pond-02. A Street SE and 17th Street SE
WL-Pond-03. D Street SE and 21st Street SE
WL-Pond-04. South 296th Street at 55th Ave S
WL-Pond-05. South 296th Street at 57th Place S
WL-Pond-06. U Street SE and 29th Street SE
WL-Pond-07. M Street SE and 37th Street SE
WL-Pond-08,09,10,11. Large Ponds for Dam Safety
Detailed 6-year CIP Timeframe
SWMP administrative tasks
Develop new stormwater manual
Update codes, standards, SOPs, maintenance for IDDE
Develop SWPPPs for City facilities
En
d
o
f
F
i
r
s
t
Pe
r
m
i
t
Review and refine LOS Goals
Establish specific sustainability goals and standards
Complete system inventory
Conduct new economic life-cycle analyses
Update, check, revise system inventory
Update criticality database
Evaluate M&O program
Expand functionality of Cartegraph CMMS software
Low Priority and West Hill Lea Hill
Remaining 20-year CIP Summary
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
IMPLEMENTATION PLAN ACTIVITIES TIMELINE
City of Auburn Comprehensive Stormwater Drainage Plan
Southeast
Additional Studies and Activities (Section 7.4)
NPDES Compliance (Section 7.3)
Monitoring (Section 7.2)
CIP (Section 7.1)
Data feed
Activity
Optional
K E Y
Continued
into next
permit term
Risk Assessment –Asset Vulnerability Analysis
Assist with Mill Creek Restoration Studies
Public education and outreach, IDDE and outfall monitoring
Update codes, standards, SOPs, maint. for construction, O&M
10. M&O Facility Improvements
Evaluate Stormwater Management for Downtown Area
Phase 1 Phase 2
Phase 1
Phase 2 Phase 3
8-1
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P:\135347 Auburn Drainage Phase II\009 Storm Drainage Comprehensive Plan\Final\Auburn Drainage Plan Final Dec09(v2).doc
CITY OF AUBURN COMPREHENSIVE
STORMWATER DRAINAGE PLAN
8. FINANCIAL PLAN
The objective of the financial plan is to identify the total cost of providing stormwater service and to
provide a financial program that allows the stormwater utility to remain financially viable during
execution of the CIP identified in Chapter 6. This viability analysis considers the historical financial
condition of the utility, the sufficiency of utility revenues to meet current and future financial and
policy obligations, and the financial impact of executing the CIP.
8.1 Past Financial Performance
This section includes a historical (2003–2008) summary of financial performance as reported by the
city of Auburn on the Statement of Revenues, Expenses, and Changes in Fund Equity and the
Statement of Net Assets, specific to the stormwater utility.
In general, these statements indicate that the financial condition of the utility has gradually
deteriorated and that without a rate adjustment, the utility’s ability to generate sufficient revenues
from service charges to meet its financial obligations may be in jeopardy.
The City recognizes the utility’s financial condition; a comprehensive rate study is underway to
evaluate the forecasted financial needs of the utility over the 2009–2014 planning horizon and
identify the level of stormwater rate increases necessary to fully fund its financial obligations. This
rate study continues to be underway with results anticipated by the end of the first quarter 2010.
8.1.1 Comparative Financial Statements
Table 8-1 shows a consolidated Statement of Revenues, Expenses, and Changes in Net Assets for
2003–2008. This table shows that over the past 6 years, growth in revenues—which is derived
primarily from stormwater service charges—has not been able to keep pace with growth in
operating expenses over the same time period, resulting in an annual operating loss since 2004.
Findings and trends. As discussed above and as shown in Table 8-1, revenues from operations
have not been able to keep pace with expenses. For example, operating income, which is a
measurement of the difference between revenues and operating expenses, declined from a net
income of $227,000 in 2003 to a net operating loss of $29,000 in 2008. Key performance indicators
over this time frame are discussed below:
The M&O coverage ratio (service revenues divided by operating expenses) declined from 1.08
in 2003 to 0.99 in 2008. A ratio of 1.0 or above is desired.
The operating ratio (total operating expenses divided by total operating revenues) has increased
from 92 percent in 2003 to 101 percent in 2008. A ratio greater than 90 percent indicates that
there is little room for new debt service and capital replacement without additional rate increases.
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A ratio greater than 100 percent indicates that operating expenses exceed operating revenues and
is indicative of an unsustainable financial condition.
The debt service coverage ratio (revenues less M&O expenses divided by total annual debt
service) decreased from 3.1 in 2003 to 2.3 in 20081. This compares to the industry target of 1.25
or greater. A ratio close to or below 1.25 indicates a financial condition that has little to no room
for new debt service without additional rate increases.
Table 8-1. Statement of Revenues, Expenses, and Changes in Fund Net
200320042005200620072008
OPERATING REVENUES
Charges for services $3,024,333$3,073,400$3,144,307$3,936,275$4,196,564$5,159,389
Other operating revenue $159$562$168$997
Total operating revenues $3,024,333$3,073,559$3,144,307$3,936,837$4,196,732$5,160,386
OPERATING EXPENSES
Maintenance and operations $684,166$835,530$991,577$1,182,889$1,397,273$1,551,406
Administration $1,005,424$1,052,752$1,071,759$1,268,878$1,394,071$1,979,083
Depreciation/amortization $854,681$889,869$902,363$953,750$951,898$1,241,980
Other operating expenses $252,729$265,844$279,723$344,895$388,563$417,130
Total operating expenses $2,797,000$3,043,995$3,245,422$3,750,412$4,131,805$5,189,599
OPERATING INCOME (LOSS)$227,333$29,564($101,115)$186,425$64,927($29,213)
NON OPERATING REVENUE (EXPENSES)
Interest revenue $58,011$75,674$175,421$316,473$416,141$295,975
Other non-operating revenue $19,407$5,580$189,541$588$77,300
Interest expense ($153,751)($123,243)($99,619)($86,173)($67,420)($37,224)
Other non-operating expenses ($4,428)($2,112)($9,858)($15,750)($25,656)$0
Total non-operating revenue (expenses)($80,761)($44,101)$255,485$214,550$323,653$336,051
INCOME (LOSS) BEFORE CONTRIBUTIONS AND TRANSFERS $146,572($14,537)$154,370$400,975$388,580$306,838
CAPITAL CONTRIBUTIONS $1,510,171$270,366$2,299,285$761,997$2,200,687$920,944
TRANSERS IN $200,000$2,100
TRANSFERS OUT ($10,473)($166,000)($335,200)($163,000)($50,000)($159,100)
Change in net assets $1,646,270$89,829$2,318,455$1,002,072$2,539,267$1,068,682
TOTAL NET ASSETS BEGINNING OF YEAR $30,733,188$32,379,458$32,245,901$34,564,356$35,566,428$38,105,695
Prior period adjustment ($223,386)
TOTAL NET ASSETS END OF YEAR $32,379,458$32,245,901$34,564,356$35,566,428$38,105,695$39,174,377
Table 8-1. Statement of Revenues, Expenses, and Changes in Fund Net Assets
Table 8-2 presents the statement of net assets. The City’s total net assets, which represent the
difference between total assets and total liabilities, has remained steady between 2003 and 2008. Key
performance indicators and trends are discussed below.
1 Total annual debt service includes interest expense and the current portion of outstanding liabilities as shown in the Statement of
Net Assets.
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Table 8-2. Statement of Net Assets
200320042005200620072008
ASSETS
Current assets:
Cash and cash equivalents$3,163,910$2,909,516$3,310,469$5,174,580$3,534,480$6,328,751
Investments $579,281$1,543,922$1,980,950$996,563$3,507,344$1,052,500
Restricted cash
Bond payments $454,953$452,740$449,902$442,329
Customer deposits
Other $584,230$556,715$504,933$479,991
Restricted cash, cash equivalents, and investments$1,201,167$1,144,431
Customer accounts $960,026$764,626$571,075$665,993$489,623$720,823
Other receivables $16,957$5,910$3,115$45,369$4,521
Inventories $4,887$5,264$5,201$7,263$7,597$8,764
Total current assets $5,909,271$6,384,716$6,912,788$7,856,969$8,539,248$9,037,679
Non-current assets
Long-term contracts and notes $0$0$0$0$0$0
Capital assets
Land $4,543,744$5,011,418$5,686,254$5,686,254$5,686,254$5,686,254
Buildings and equipment$75,788$114,615$144,561$160,173$192,076$201,255
Improvements other than buildings$32,671,272$32,640,891$34,403,317$34,491,359$37,356,499$38,271,397
Construction in progress$263,102$295,938$123,833$660,226$266,636$808,357
Less: accumulated depreciation (A/D)($7,947,145)($8,837,014)($9,739,378)($10,693,127)($11,645,026)($12,887,006)
Total capital assets (Net of A/D)$29,606,761$29,225,848$30,618,587$30,304,885$31,856,439$32,080,257
Other non-current assets
Deferred charges $32,662$28,067
Total non-current assets $29,639,423$29,253,915$30,618,587$30,304,885$31,856,439$32,080,257
Total assets $35,548,694$35,638,631$37,531,375$38,161,854$40,395,687$41,117,936
LIABILITIES
Current liabilities
Current payables $134,303$129,120$118,484$103,153$189,865$218,480
Customer deposits
Interfund payables
Loans payable: current
Employee leave benefits: current$63,035$46,364$51,301$51,807$66,260$92,777
Revenue bonds payable: current$310,900$327,600$343,000$361,300$379,900$398,500
General obligation bonds payble: current
Accured interest $160,636$142,047$111,954$91,441$70,002$43,829
Deposits $6,025
Other liabilities payable
Total current liabilities $674,899$645,131$624,739$607,701$706,027$753,586
Non-current liabilities
Deferred revenue $597,204$597,204$597,204$597,204$597,204
Employee leave benefits $52,224$38,671$40,537$39,427$7,712$11,443
Deferred credits $24,713$21,924
Loans payable
Revenue bonds payable$2,417,400$2,089,800$1,704,539 $1,351,094$979,049$581,326
General obligation bonds payable
Total non-current liabilities $2,494,337$2,747,599$2,342,280$1,987,725$1,583,965$1,189,973
Total liabilities $3,169,236$3,392,730$2,967,019$2,595,426$2,289,992$1,943,559
NET ASSETS
Invested in capital assets, net of related debt$20,670,701$26,808,448$28,571,047$28,592,491$30,497,490 $31,100,432
Restiricted for:
Debt service $374,784$374,784$284,230$256,715$204,933$179,991
Construction
Unrestricted $11,333,973$5,062,669$5,709,079$6,717,222$7,403,272 $7,893,954
Total net assets $32,379,458$32,245,901$34,564,356$35,566,428$38,105,695$39,174,377
Total liabilities and net assets $35,548,694$35,638,631$37,531,375$38,161,854$40,395,687$41,117,936
Table 8-2. Statement of Net Assets
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Total net assets: Total net assets, which represent the difference between total assets and total
liabilities, steadily increased from $32.4 million in 2003 to $39.2 million in 2008.
Liquidity ratio: The current ratio (unrestricted current assets divided by current liabilities)
increased from 5.6 in 2003 to 9.8 in 2008, reflecting a rise in the amount of cash and cash
equivalents during this period. A ratio of 2:1 or higher is considered good in terms of healthy
liquidity.
Capital structure ratio: The debt–to-equity ratio (total debt divided by the sum of retained
earnings and contributed equity) declined from 9 percent debt/91 percent equity in 2003 to 4
percent debt/96 percent equity in 2008. This reduction in debt indicates that the City has capacity
to acquire new debt to help fund the CIP without jeopardizing its debt-to-equity position. This
indicator should be evaluated in context with the debt service coverage ratio discussed above.
8.2 Financial Plan
The city of Auburn stormwater utility is responsible to fund all of its related costs; it does not
depend on general tax revenues or general fund resources. The primary source of funding for the
utility is collections from stormwater service charges. The City controls the level of service charges
by ordinance and, subject to statutory authority, can adjust user charges as needed to meet financial
objectives.
The financial plan can only provide a qualified assurance of financial feasibility if it considers the
“total system” costs of providing stormwater service—both operating and capital. To meet these
objectives, the following elements are completed:
Capital funding plan. This plan identifies the total CIP obligations for the 2009–2014 planning
period. The plan defines a strategy for funding the CIP including an analysis of available
resources from rate revenues, existing reserves, SDCs, debt financing, and any special resources
that may be readily available (e.g., grants, developer contributions, etc.). The capital funding plan
impacts the financial plan through the use of debt financing (resulting in annual debt service) and
the assumed rate revenue resources available for capital funding.
Financial forecast. This forecast identifies annual non-capital costs associated with the
operation, maintenance, and administration of the stormwater system. Included in the financial
plan is a reserve analysis that forecasts cash flow and fund balance activity along with testing for
satisfaction of actual or recommended minimum fund balance policies. The financial plan
ultimately evaluates the sufficiency of utility revenues in meeting all obligations, including cash
uses such as operating expenses, debt service, and reserve contributions, as well as any coverage
requirements associated with long-term debt.
8.2.1 Utility Fund Structure
To account for operating, capital, and restricted activities, the City maintains the following three
separate accounts within the stormwater utility:
Operations: serves as an operating account where operating revenues are deposited and
operating expenses are paid.
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Capital projects: serves as a capital account where capital revenues are deposited (SDCs, grant
proceeds, and debt proceeds) and capital expenditures are paid.
Restricted bond reserve: serves as a restricted account set up to comply with revenue bond
covenants as discussed above.
Minimum balance thresholds for these accounts are discussed under the next section, Financial
Policies.
8.2.2 Financial Policies
A brief summary of the key financial policies employed by the City, as well as those recommended
and incorporated in the financial program, is presented in this section.
8.2.2.1 Reserve Policies
Utility reserves serve multiple functions: They can be used to address variability and timing of
expenditures and receipts; occasional disruptions in activities, costs, or revenues; utility debt
obligations; and many other functions. The collective use of individual reserves helps to limit the
City’s exposure to revenue shortfalls, meet long-term capital obligations, and reduce the potential for
bond coverage defaults. Common reserves among municipal utilities are operating reserves, capital
contingency reserves, and bond reserves. The City currently maintains a form of these reserves as
described below:
Operating reserve: An operating reserve, or working capital reserve, provides a minimum
unrestricted fund balance needed to accommodate the short-term cycles of revenues and
expenses. These reserves are intended to address both anticipated and unanticipated changes in
revenues and expenses. Anticipated changes may include billing and receipt cycles, payroll cycles,
and other payables. Operating reserves can be used to meet short-term cash deficiencies due to
the timing of annual revenues and expenditures.
Generally, utilities target a certain number of days of working capital as a beginning cash balance
to provide the liquidity needed to allow regular management of payable and payment cycles.
Consistent with industry practice, a working capital reserve of between 8 and 12 percent, or 30 to
45 days of M&O expenses, is targeted. Based upon the City’s 2009 budget, this target is
equivalent to approximately $450,000 to $700,000.2
Capital contingency reserve: A capital contingency reserve is an amount of cash set aside in
case of an emergency should a piece of equipment or a portion of the utility’s infrastructure fail
unexpectedly. Additionally, the reserve could be used for other unanticipated capital needs
including capital project cost overruns. There are various approaches to identifying an
appropriate level for this reserve, such as (1) a percentage of a utility system fixed asset costs and
(2) determining the cost of replacing highly critical assets or facilities. For purposes of this
analysis, a minimum fund balance equal to 1 percent of plant in service is targeted.
2 City financial policies require a minimum working capital balance of $1.0 million in each utility fund (combined operations and CIP).
This financial analysis is compliant with this fiscal policy.
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Bond reserve: Bond covenants often establish reserve requirements as a means of protecting an
agency against the risk of nonpayment. This bond reserve can be funded with cash on hand, but
is more often funded at the time of borrowing as part of the bond principal. This reserve
requirement can also be met by using a surety bond. The City maintains a restricted bond reserve
in compliance with its bond covenants.
8.2.2.2 System Reinvestment Policies
The purpose of system reinvestment funding is to provide for the replacement of aging system
facilities to ensure sustainability of the system for ongoing operation. Each year, the utility’s assets
lose value, and as they lose value they move toward eventual replacement. That accumulating loss in
value and future liability is typically measured for reporting purposes through annual depreciation
expense, which is based on the original cost of the asset over its anticipated useful life. While this
expense reflects the consumption of the existing asset and its original investment, the replacement
of that asset will likely cost much more, factoring in inflation and construction conditions.
Therefore, the added annual replacement liability is even greater than the annual depreciation
expense.
This analysis assumes no system reinvestment funding for the future replacement of system assets,
consistent with current City practice. We recommend that the City incorporate a policy of system
reinvestment funding through rates as soon as feasible.
8.2.2.3 Debt Policies
Bond covenants often establish a minimum debt coverage ratio as a means of protecting an agency
against the risk of nonpayment. The City’s current bond covenants require a ratio of 1.25 times
annual revenue bond debt service.
Existing long-term debt includes a 1999 revenue bond issue and a 2005 revenue refinancing bond
issue, both of which were issued for stormwater and water construction projects. Final debt service
payment for the 1999 bonds is scheduled to occur in 2009 and 2016 for the revenue refinancing
bonds.
This financial plan includes a planned 2010 bond issue by the city of Auburn in the amount of $6.5
million to support the construction of water and stormwater utility projects. Based upon discussions
with City staff, proceeds from this issuance will be split $4.0 million to the water utility and $2.5
million to the stormwater utility. The terms of this bond issuance include a par value of $6.5 million
and an annual interest rate of 5.5 percent with semi-annual payments spread over a 20-year period.
Existing bond covenants dictate a coverage ratio of 1.25.
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8.2.3 Capital Funding Plan
The CIP developed for this Drainage Plan totals 20 separate projects valued at $22.0 million.
Significant projects during the 2009–2014 period include the following:
annual storm drainage infrastructure repair/replacement projects: $2.6 million
arterial utility improvements: $1.3 million
relieving Auburn Way S flooding phases 1 and 2: $2.0 million
relieving 30th Street NE area flooding phases 1 and 2: $3.6 million
White River storm pump station replacement: $2.5 million
Peasley Canyon culvert replacement: $1.0 million
West Main Street pump upgrade: $1.1 million
S. 296th Street south pond expansion phases 1 and 2: $1.5 million
West Valley Highway improvements: $1.5 million
SOS utility improvements: $900,000
R Street storm drain improvements: $770,000
Port of Seattle mitigation agreement project: $600,000
SCADA telemetry upgrades: $340,000.
Table 8-3 summarizes the annual costs associated with the 6-year CIP.
Table 8-3. 2009–2014 Stormwater CIP
Year Annual CIP
2009 3,245,000
2010 4,521,000
2011 5,986,540
2012 1,358,636
2013 4,582,306
2014 2,315,202
6-year total $22,009,484
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A capital funding plan is developed to determine the total resources available to meet the CIP needs
and determine if new debt financing will be required. The utility started 2009 with a cash balance of
$5.9 million for its capital program. Future SDC collections are projected at $200,000 annually
through 2014. To be conservative, no growth in this revenue source is assumed.
The 2009–2014 funding plan includes $2.5 million in proceeds from the planned 2010 bond issue as
discussed earlier, $1.2 million in SDCs, $16.0 million in existing cash reserves including interest, and
$11.2 million in new revenue bonds. A summary of the 2009–2014 capital funding plan is
summarized in Table 8-4 below. Figures presented are in inflated dollars.
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Table 8-4. 2009–2014 Capital Financing Plan
2009 2010 2011 2012 2013 2014 Total
Total capital projects $3,245,000 $4,521,800 $5,986,540 $1,358,636 $4,582,306 $2,315,202 $22,009,484
2010 City planned revenue bond $0 $2,500,000 $0 $0 $0 $0 $2,500,000
New revenue bond proceeds $0 $0 $4,658,723 $875,441 $3,147,475 $2,489,419 $11,171,058
Use of system development changes $200,000 $200,000 $200,000 $200,000 $200,000 $200,000 $1,200,000
Use of capital fund balance $3,045,000 $1,821,800 $1,127,817 $283,195 $1,234,831 ($374,217) $7,138,426
Total funding sources $3,245,000 $4,521,800 $5,986,540 $1,358,636 $4,582,306 $2,315,202 $22,009,484
8.3 Available CIP Funding Assistance and Financing
Resources
Feasible long-term capital funding strategies should be defined to ensure that adequate resources are
available to fund the CIP identified in this Drainage Plan. In addition to the utility’s resources such
as accumulated cash reserves, capital revenues, bond proceeds, and SDCs, capital needs can also be
met from outside sources such as grants, low-interest loans, and bond financing. The following is a
summary of utility and outside resources.
8.3.1 Utility Resources
Utility resources appropriate for funding capital needs include accumulated cash in the CIP funds,
bond proceeds, and capital revenues such as SDCs. The first two resources have been discussed in
the Financial Policies section. Capital-related revenues are discussed below.
8.3.1.1 System Development Charges
An SDC as provided for by RCW 35.92.025 refers to a one-time charge imposed on new customers as
a condition of connection to the utility system. The purpose of the SDC is twofold: to promote equity
between new and existing customers, and to provide a source of revenue to fund capital projects.
Equity is served by providing a vehicle for new customers to share in the capital costs incurred to
support their addition to the system. SDC revenues provide a source of cash flow used to support
utility capital needs; revenue can be used only to fund utility capital projects or to pay debt service
incurred to finance those projects.
In the absence of an SDC, growth-related capital costs would be borne in large part by existing
customers. In addition, the net investment in the utility already collected from existing customers,
whether through rates, charges, and/or assessments, would be diluted by the addition of new
customers, effectively subsidizing new customers with prior customers’ payments. To establish equity,
an SDC should recover a proportionate share of the existing and future infrastructure costs from a
new customer. From a financial perspective, a new customer should become financially equivalent to
an existing customer by paying the SDC.
The following table summarizes the City’s current SDC schedule.
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Table 8-5. Current System Development Charge Schedulea
SDC
Charge per equivalent service unit (ESU) b $1,162
a. Source: City of Auburn fee schedule, Fees for City Permits and Actions, effective January 1, 2009. As approved per Ord. 5819, as amended.
b. ESU is a term used to define the capacity that is required by new development within the stormwater system. A single-family house is established as 1.0 ESU.
It should be noted that, as part of a comprehensive rate study started in late 2008, the City will be
evaluating its SDC level based upon the City’s planned 20-year CIP. Results are expected by the end
of the first quarter 2010.
8.3.1.2 Local Facilities Charge
While an SDC is the manner in which new customers pay their share of general facilities costs, local
facilities funding is used to pay the costs of local facilities that connect each property to the system’s
infrastructure. Local facilities funding is often overlooked in a rate forecast because it is funded up
front by either connecting customers, developers, or through an assessment to properties—but
never from rates. Although these funding mechanisms do not provide a capital revenue source
toward funding CIP costs, the discussion of these charges is included in this chapter, as they are an
impact to the new customer of the system.
A number of mechanisms can be considered toward funding local facilities. One of the following
scenarios typically occurs:
the utility charges a connection fee based on the cost of the local facilities (under the same
authority as the SDC)
a developer funds extension of the system to their development and turns those facilities over to
the utility (contributed capital)
a local assessment is set up called a Utility Local Improvement District (ULID) which collects tax
revenue from benefited properties.
A local facilities charge (LFC) is a variation of the SDC authorized through RCW 35.92.025. It is a
city-imposed charge to recover the cost related to service extension to local properties. Often called
a front-footage charge and imposed on the basis of footage of main “fronting” a particular property,
it is usually implemented as a reimbursement mechanism to a city for the cost of a local facility that
directly serves a property. It is a form of connection charge and therefore can accumulate up to 10
years of interest. It typically applies to instances where no developer-installed facilities are needed
through developer extension due to the prior existence of available mains already serving the
developing property.
The developer extension is a requirement that a developer install onsite and sometimes offsite
improvements as a condition of extending service. These are in addition to the SDC required and
must be built to City standards. The City is authorized to enter into developer extension agreements
under RCW 35.91.020. Part of the agreement between the City and the developer for the developer
to extend service might include a latecomer agreement, resulting in a latecomer charge to new
connections to the developer extension.
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Latecomer charges are a variation of developer extensions whereby new customers connecting to
a developer-installed improvement make a payment to the City based on their share of the
developer’s cost (RCW 35.91.020). The City passes this cost on to the developer who installed the
facilities. This is part of the developer extension process, and defines the allocation of costs and
records latecomer obligations on the title of affected properties. No interest is allowed, and the
reimbursement agreement cannot exceed 15 years in duration.
A ULID is another mechanism for funding infrastructure that assesses benefited properties based
on the special benefit received by the construction of specific facilities (RCW 35.43.042). Most often
used for local facilities, some ULIDs also recover related general facilities costs. Substantial legal and
procedural requirements can make this a relatively expensive process, and there are mechanisms by
which a ULID can be rejected by a majority of property ownership within the assessment district
boundary.
8.3.2 Outside Resources
Grants, low-cost loans, and public debt present other possible funding sources. These financing
options are discussed in this section.
8.3.2.1 Grants and Low-Cost Loans
Historically, federal and state grant programs were available to local utilities for capital funding
assistance. However, these assistance programs have been mostly eliminated, substantially reduced in
scope and amount, or replaced by loan programs. Remaining miscellaneous grant programs are
generally lightly funded and heavily subscribed. Nonetheless, the benefit of even the very low-
interest loans makes the effort of applying worthwhile. Grants and low-cost loans for Washington
State utilities are available from Ecology and the Department of Community, Trade, and Economic
Development (CTED). Each includes programs for which the City might be eligible. They are
primarily targeted at low-income and/or rural communities.
Department of Ecology (from the FY2010–2011 Water Quality Financial Assistance
Guidelines)
The Department of Ecology Water Quality Program administers three major funding programs that
provide low-interest loans, grants, or loan-and-grant combinations for projects that protect,
preserve, and enhance water quality in Washington. These guidelines describe how to apply for
funding, meet program requirements, and manage funded projects for the following programs:
the Centennial Clean Water Program (Centennial)
the Clean Water Act Section 319 Nonpoint Source Grant Program (Section 319)
the Washington State Water Pollution Control Revolving Fund (Revolving Fund).
Further detail is available at http://www.ecy.wa.gov/biblio/0810080.html.
Department of Community, Trade, and Economic Development (from the CTED Web
site)
CTED has two grant and loan programs that the City might be eligible for:
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the Community Economic Revitalization Board (CERB) grant and loan program
the Public Works Trust Fund (PWTF) loan program.
Each of these programs is described in greater detail below.
Community Economic Revitalization Board: CERB primarily offers low-cost loans; grants are
made available only to the extent that a loan is not reasonably possible. The CERB targets public
facility funding for economically disadvantaged communities, specifically targeting job creation and
retention. Priority criteria include the unemployment rates, number of jobs created and/or retained,
wage rates, projected private investment, and estimated state and local revenues generated by the
project. Traditional construction projects are offered at a maximum dollar limit per project of $1
million. A local match of 25 percent is targeted.
Eligible applicants include cities, towns, port districts, special purpose districts, federally recognized
Indian tribes, and municipal corporations.
The CERB’s policy is that all loans made by the CERB will be secured by a general obligation pledge
of the taxing power of the borrowing entity. Terms do not exceed 20 years including available
payment deferral of interest and principal for up to 5 years. Interest rates match the most current
rate of Washington State bonds (not to exceed 10 percent).
Further detail is available at http://www.cted.wa.gov/site/64/default.aspx.
Public Works Trust Fund: Cities, towns, counties, and special purpose districts are eligible to
receive loans. Water, sewer, storm, roads, bridges, and solid waste/recycling are eligible and funds
may be used for repair, replacement, rehabilitation, reconstruction, and improvements including
reasonable growth (generally the 20-year growth projection in the comprehensive plan).
PWTF loans are available at interest rates of 0.5, 1, and 2 percent with the lower interest rates given
to applicants who pay a larger share of the total project costs. The loan applicant must provide a
minimum local match of funds of 5 percent toward the project cost to qualify for a 2 percent loan,
10 percent for a 1 percent loan, and 15 percent for a 0.5 percent loan. The useful life of the project
determines the loan term up to a maximum of 20 years.
Further detail is available at http://www.cted.wa.gov/site/361/default.aspx.
8.3.2.2 Public Debt
Public debt options include general obligation (GO) bonds and revenue bonds, which are discussed
in this section.
General obligation bonds: GO bonds are bonds secured by the full faith and credit of the issuing
agency, committing all available tax and revenue resources to debt repayment. With this high level of
commitment, GO bonds have relatively low interest rates and few financial restrictions. However,
the authority to issue GO bonds is restricted in terms of the amount and use of the funds, as
defined by Washington constitution and statute. Specifically, the amount of debt that can be issued
is linked to assessed valuation.
RCW 39.36.020 states:
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“(ii) Counties, cities, and towns are limited to an indebtedness amount not exceeding one
and one-half percent of the value of the taxable property in such counties, cities, or towns
without the assent of three-fifths of the voters therein voting at an election held for that
purpose.
(b) In cases requiring such assent counties, cities, towns, and public hospital districts are
limited to a total indebtedness of two and one-half percent of the value of the taxable
property therein.”
While bonding capacity can limit availability of GO bonds for utility purposes, these can sometimes
play a valuable role in project financing. A rate savings may be realized through two avenues: the
lower interest rate and related bond costs; and the extension of repayment obligation to all tax-
paying properties (not just developed properties) through the authorization of an ad valorem property
tax levy.
Revenue bonds: Revenue bonds are commonly used to fund utility capital improvements. The debt
is secured by the revenues of the issuing utility and the debt obligation does not extend to the City’s
other revenue sources. With this limited commitment, revenue bonds typically bear higher interest
rates than GO bonds and also require security conditions related to the maintenance of dedicated
reserves (a bond reserve) and financial performance (added bond debt service coverage). The City
agrees to satisfy these requirements by ordinance as a condition of bond sale.
Revenue bonds can be issued in Washington without a public vote. There is no bonding limit,
except perhaps the practical limit of the utility’s ability to generate sufficient revenue to repay the
debt and provide coverage. In some cases, poor credit might make issuing bonds problematic.
8.3.2.3 Summary
An ideal funding strategy would include the use of grants and low-cost loans when debt issuance is
required. However, these resources are very limited and competitive in nature and do not provide a
reliable source of funding for planning purposes. It is recommended that the City pursue these
funding avenues but assume bond financing to meet needs above the utility’s available cash
resources. GO bonds may be useful for special circumstances, but due to the bonding capacity limits
they are most often reserved for other City (non-utility) purposes. Revenue bonds are a more secure
financing mechanism for utility needs. The capital financing strategy developed to fund the updated
CIP assumes the following funding priority:
1. Available grant funds
2. Accumulated capital cash reserves
3. Annual revenue collections from SDCs
4. Annual transfers of rate-funded capital or excess cash (above minimum balance targets) from
operating accounts
5. Interest earnings on CIP Fund balances and other miscellaneous capital resources
6. Revenue bond financing.
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8.4 Financial Forecast
The financial forecast, or revenue requirement analysis, forecasts the amount of annual revenue that
needs to be generated by rates. The analysis incorporates operating revenues, M&O expenses, debt
service payments, rate-funded capital needs, and any other identified revenues or expenses related to
utility operations, and determines the sufficiency of the current level of rates. Revenue needs are also
impacted by debt covenants (typically applicable to revenue bonds) and specific fiscal policies and
financial goals of the utility.
For this analysis, two revenue sufficiency criteria have been developed to reflect the financial goals
and constraints of the utility: cash needs must be met, and debt coverage requirements must be
realized. In order to operate successfully with respect to these goals, both tests of revenue
sufficiency must be met.
8.4.1.1 Cash Test
The cash flow test identifies all known cash requirements for the utility in each year of the planning
period. Capital needs are identified and a capital funding strategy is established. This may include the
use of debt, cash reserves, outside assistance, and rate funding. Cash requirements to be funded
from rates are determined. Typically, these include M&O expenses, debt service payments, system
reinvestment funding or directly funded capital outlays, and any additions to specified reserve
balances. The total annual cash needs of the utility are then compared to total operating revenues
(under current rates) to forecast annual revenue surpluses or shortfalls.
8.4.1.2 Coverage Test
The coverage test is based on a commitment made by the City when issuing revenue bonds. For
purposes of this analysis, revenue bond debt is assumed for any needed debt issuance. As a security
condition of issuance, the City is required per covenant to agree that the revenue bond debt would
have a higher priority for payment (a senior lien) compared to most other utility expenditures; the
only outlays with a higher lien are M&O expenses. Debt service coverage is expressed as a multiplier
of the annual revenue bond debt service payment. For example, a 1.0 coverage factor would imply
that no additional cushion is required. A 1.25 coverage factor means that revenues must be sufficient
to pay M&O expenses and annual revenue bond debt service payments, plus an additional 25
percent of annual revenue bond debt service payments. The excess cash flow derived from the
added coverage, if any, can be used for any utility purpose, including funding capital projects. The
existing coverage requirement on the City’s outstanding revenue bonds is 1.25 times bond debt.
In determining the annual revenue requirement, both the cash and coverage sufficiency tests must
be met; the test with the greatest deficiency drives the level of needed rate increase in any given year.
8.4.2 Financial Forecast
The financial forecast is developed from the City’s adopted 2009–2010 biennial budget documents
along with other key factors and assumptions to develop a complete portrayal of the stormwater
utility annual financial obligations. The following is a list of the key revenue and expense factors and
assumptions used to develop the forecast:
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Annual customer growth is estimated at 2.0 percent over the study period based on discussions
with City staff.
The City’s 2009–2010 budget forms the baseline for revenue and expense forecasts. Included in
the 2009–2010 budget is a City-adopted stormwater rate increase of 6.06 percent effective
January 2009 and a 5.99 percent rate increase effective January 2010. These increases were
applied across the board, affecting all rates and customer classes.
City rate revenues include revenues from stormwater service charges. Estimated stormwater
service charges for 2009 were forecasted incorporating customer growth.
Interest earnings assume a rate of 2.5 percent applied to beginning of year cash balances.
M&O expenses are escalated from the 2010 budget figures at 4.0 percent per year for general cost
and labor inflation and 6 percent for employee benefit cost inflation. State taxes are calculated
based on prevailing tax rates.
Existing debt service schedules were provided by the City and two revenue bond issues.
Future debt service has been added as outlined in the capital funding plan. The forecast assumes
a revenue bond interest rate of 6 percent, issuance cost of 2 percent, and a 20-year term.
Consistent with current City practice, no system reinvestment funding is forecasted.
This financial plan focuses on the 2009–2014 planning period. Table 8-6 summarizes the projected
financial performance for the 2009–2014 planning period based upon the above assumptions.
Table 8-6. Financial Forecast
200920102011201220132014
Revenues
Rate revenues under existing rates$5,321,000$5,689,000$5,802,780$5,918,836$6,037,212$6,157,957
Non-rate revenues$50,000$50,706$49,606$40,777$35,256$27,833
Total revenues$5,371,000$5,739,706$5,852,386$5,959,613$6,072,469$6,185,790
Expenses
Cash operating expenses$5,246,385$5,489,365$5,565,534$5,791,060$6,026,367$6,271,900
NPDES compliance expenses$0$121,400$210,392$203,208 $211,336$219,789
Existing debt services$96,379$346,223$347,263$348,147$346,275$346,951
Debt service: City-planned 2010 revenue bonds$0$102,583$205,166$205,166$205,166$205,166
Debt service: new revenue bond proceeds$0$0$454,930 $540,418$847,773$1,090,868
Rate-funded system reinvestment$0$0$0$0$0$0
Total expenses$5,342,764$6,059,571$6,783,285$7,087,998$7,636,917$8,134,674
Annual surplus/(deficiency)$28,236($319,865)($930,898)($1,128,386)($1,564,448)($1,948,884)
Debt service coverage (target: at least 1.25)1.072.041.000.490.02(0.43)
Table 8-6. Financial Forecast
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Table 8-6 shows the forecasted rate revenues under the City’s adopted 2009–2010 budget5, and the
forecasted rate revenues over the remaining 2011–2014 planning period. This financial forecast
shows that planned and forecasted stormwater utility service charges under current adopted rates are
not sufficient to fund the “total system” cost of the utility. The gap between revenues and expenses
is forecasted to be minimal in 2009 and continue declining through 2014. In addition, as a result of
the resource deficiency, debt service coverage is forecasted to fall below the minimum threshold as
prescribed by the City’s bond covenants starting in 2009.
The City recognizes that forecasted stormwater utility service charge revenues under existing rates
are insufficient to meet its forecasted financial obligations. A comprehensive rate study is underway
to evaluate the forecasted financial needs of the utility over the 2009–2014 planning horizon and
identify the level of stormwater rate increases necessary to fully fund its financial obligations. Results
of this rate study is anticipated by the end of the first quarter 2010.
8.4.3 City Funds and Reserve Balances
Table 8-7 shows a summary of the projected ending City operating and capital reserve balances
through 2014 based on the rate forecasts presented herein. As shown below, as forecasted revenues
are unable to keep pace with the forecasted growth in expenses, the operating fund is projected to
gradually erode and fall into a deficit position starting in 2013. The capital fund balance is forecasted
to decline to about $200,000 starting in 2011 reflecting the annual collection of SDC revenues and
associated interest earnings. The debt reserve balance is set by covenant and is in compliance with
coverage requirements.
Table 8-7. Cash Balance Summary
200920102011201220132014
Operating fund$2,028,236$1,708,372$770,576($379,322)($1,979,027)($3,955,744)
Capital fund$3,061,090$1,327,817$233,195$205,830$205,146$205,129
Debt reserves$0$0$454,930$540,418$847,773$1,090,868
Total$5,089,326$3,036,189$1,458,702$366,926($926,108)($2,659,748)
Combined minimum target balance$776,379$851,426$1,379,796$1,492,970$1,855,213$2,146,129
Table 8-7. Cash Balance Summary
8.5 Rate Structures
Existing and projected retail rates are discussed in this section.
8.5.1 Existing Retail Rates
The City’s existing retail stormwater rates for inside-city customers comprises two rate classes. The
retail rate schedule for the single-family residential customer class consists of a fixed base monthly
5 2009-2010 rate revenues reflect City Ordinance 6204, adopted September 2008, which increased monthly stormwater rates 6.06
percent in January 2009 and 5.99 percent in January 2010.
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charge. The retail rate schedule for the non-single-family residential customer class consists of a base
monthly charge and a single volume rate per ESU depending upon the type of stormwater service6.
The City does not have any outside-city customers. Low-income single-family residential customers
are provided a 50 percent discount to the rates presented. To qualify for a low-income discount, a
customer must be 62 years of age or older and meet low-income guidelines as defined by the U.S.
Department of Housing and Urban Development7.
Table 8-8 presents the City’s existing retail stormwater monthly rate schedule for each customer
classification.
Table 8-8. Existing Retail Stormwater Rates
Jan. 1, 2009Jan. 1, 2010
Inside city
Single-family residential$13.38$14.18
Non-single-family residential
Base rate (all classes)$8.32$8.82
Volume rates (per ESU)
Non-SFR $10.65$11.29
NSF w/ detention$8.55$9.07
NSF w/ retention$5.30$5.61
NSF w/ WQ$6.40$6.78
NSF w/ detention and WQ$4.83$5.12
NSF w/ retention and WQ$3.03$3.21
Low income discount: 50%
Current monthly rates
Table 8-8. Existing Retail Stormwater Rates
8.5.2 Projected Retail Rates
As discussed above, a rate study is presently underway to assess the level of retail stormwater rate
increases necessary to fully fund utility financial obligations.
8.6 Affordability
A common affordability benchmark for utility rates is to test the monthly median income equivalent
against the existing and projected monthly utility rates. The typical threshold used to assess relative
affordability is 1.5 percent of the median household income (MHI). In the case of the City’s
stormwater utility, utility billings should not exceed $814.10 over the course of a year or $67.84 on a
monthly basis. Based upon the City’s adopted rates for 2010, a typical stormwater service billing is
$170.16 per year or $14.18 per month, both of which are well within the affordability benchmark as
outlined above.
6 AMC 13.48.100.
7 AMC 13.24 and 13.24.050.
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Table 8-9 below presents the results of the affordability test8.
Table 8-9. Affordability Test
1999 median household income (MHI)$39,208
Assumed annual growth in MHI 3.00%
Estimated 2010 MHI $54,273
Affordability benchmark 1.50%
Maximum affordable billing
- Annual $814.10
- Monthly $67.84
Actual billing at 7.5 ccf per month
- Annual $170.16
- Monthly $14.18
Table 8-9. Affordability Test
Rate affordability should be evaluated for future years following completion of the rate study.
8.7 Conclusion
This financial plan indicates that the City’s adopted rates will not be sufficient to fund utility
financial obligations. The City is aware of this financial situation and had therefore initiated a
comprehensive stormwater rate study to determine the appropriate level of adjustment to
stormwater rates over the 2009–2014 planning period. This study is presently underway with results
expected by the end of the first quarter 2010.
8 Based on city of Auburn 1999 median household income of $39,208 as published by the U.S. Census Bureau. Median household
income is escalated to 2010 values at rate of 3 percent per year. Current billings are based upon existing 2010 rates.
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CITY OF AUBURN COMPREHENSIVE
STORMWATER DRAINAGE PLAN
9. LIMITATIONS
Report Limitations
This document was prepared solely for the city of Auburn in accordance with professional standards
at the time the services were performed and in accordance with the contract between the city of
Auburn and Brown and Caldwell dated July 12, 2007. This document is governed by the specific
scope of work authorized by the city of Auburn; it is not intended to be relied upon by any other
party except for regulatory authorities contemplated by the scope of work. We have relied on
information or instructions provided by the city of Auburn and other parties and, unless otherwise
expressly indicated, have made no independent investigation as to the validity, completeness, or
accuracy of such information.
This document sets forth the results of certain services performed by Brown and Caldwell with
respect to the property or facilities described therein (the Property). The city of Auburn recognizes
and acknowledges that these services were designed and performed within various limitations,
including budget and time constraints. These services were not designed or intended to determine
the existence and nature of all possible environmental risks (which term shall include the presence or
suspected or potential presence of any hazardous waste or hazardous substance, as defined under
any applicable law or regulation, or any other actual or potential environmental problems or
liabilities) affecting the Property. The nature of environmental risks is such that no amount of
additional inspection and testing could determine as a matter of certainty that all environmental risks
affecting the Property had been identified. Accordingly, THIS DOCUMENT DOES NOT
PURPORT TO DESCRIBE ALL ENVIRONMENTAL RISKS AFFECTING THE PROPERTY,
NOR WILL ANY ADDITIONAL TESTING OR INSPECTION RECOMMENDED OR
OTHERWISE REFERRED TO IN THIS DOCUMENT NECESSARILY IDENTIFY ALL
ENVIRONMENTAL RISKS AFFECTING THE PROPERTY.
Further, Brown and Caldwell makes no warranties, express or implied, with respect to this
document, except for those, if any, contained in the agreement pursuant to which the document was
prepared. All data, drawings, documents, or information contained this report have been prepared
exclusively for the person or entity to whom it was addressed and may not be relied upon by any
other person or entity without the prior written consent of Brown and Caldwell unless otherwise
provided by the Agreement pursuant to which these services were provided.
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REFERENCES
Auburn City Code (ACC). 2009. http://www.codepublishing.com/wa/auburn/.
Carlaw, Tim. Auburn Public Works. Email correspondence on June 12, 2009.
City of Auburn Comprehensive Plan (Comp Plan). Amended 2008. City of Auburn.
http://www.auburnwa.gov/business/Planning___Development/Comprehensive_Plan.asp.
King County. September 2008. Draft Alternatives Analysis Report, Tributary 045 Ravine Stabilization Capital Improvement Project, Project
0D1871. King County Department of Natural Resources and Parks, Water and Land Resources Division, Capital Projects Section.
201 South Jackson St., Suite 600, Seattle, Washington, 98104.
Miller, J.F., Frederick, R.H., and Tracey, R.J. 1973. Precipitation-frequency Atlas of the Western United States: NOAA Atlas 2 Volume IX-
Washington. United States Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service.
Silver Spring, Maryland.
Natural Resources Conservation Center (NRCS). June 1986. Urban Hydrology for Small Watershed, Technical Release 55 (TR-55). United
States Department of Agriculture, Natural Resources Conservation Service, Conservation Engineering Division.
Tetra Tech, Inc. September 2002. City of Auburn 2002 Comprehensive Drainage Plan. Prepared for the city of Auburn by Tetra Tech/KCM,
Inc., 1917 First Ave., Seattle, WA 98101.
U.S. Army Corps of Engineers (USACE). April 2009. Project Management Plan for Wetland 5K Reach Mill Creek Restoration, Green Duwamish
Ecosystem Restoration Program. U.S. Army Corps of Engineers, Seattle District,
U.S. Army Corps of Engineers (USACE). October 2009. Mud Mountain Dam: White and Puyallup Rivers Channel Capacity Study. U.S. Army
Corps of Engineers, Seattle District, Hydraulic Engineering Section.
Western Regional Climate Center (WRCC). 2009a. “Climate of Washington.” http://www.wrcc.dri.edu/narratives/WASHINGTON.htmWestern
Regional Climate Center (WRCC). 2009b. “Period of Record Monthly Climate Summary for Seattle Tcoma Wscmo Ap, Washington.”
http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?wa7473
Western Regional Climate Center (WRCC). 2009c. “Period of Record Monthly Climate Summary for Kent, Washington.”
http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?wa4169
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Seattle WA 98101
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Fax: 206.749.2200
www.brownandcaldwell.com