HomeMy WebLinkAboutAuburn Drainage Plan Draft.pdf
Comprehensive Storm
Drainage Plan
Prepared for the
Community Development and
Public Works Department
City of Auburn, Washington
April 2015
DRAFT
701 Pike St., Suite 1200
Seattle, WA 98101
Comprehensive Storm Drainage Plan
Prepared for the
Community Development and Public Works Department
City of Auburn, Washington
April 2015
This is a draft and is not intended to be a final representation
of the work done or recommendations made by Brown and Caldwell.
It should not be relied upon; consult the final report.
DRAFT
v
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Table of Contents
List of Figures ............................................................................................................................................. viii
List of Tables ................................................................................................................................................ ix
List of Abbreviations .................................................................................................................................... xi
Executive Summary ............................................................................................................................... ES-1
ES-1 LOS Goals ............................................................................................................................. ES-1
ES-2 Evaluation of the Storm Drainage Utility .............................................................................. ES-4
ES-3 Implementation Plan ........................................................................................................... ES-5
ES-3.1 6-Year and 20-Year CIP ......................................................................................... ES-5
ES-3.2 Monitoring .............................................................................................................. ES-7
ES-3.3 Programmatic Measures for NPDES Compliance ............................................... ES-9
ES-3.4 Future Staffing and Equipment Needs .............................................................. ES-10
ES-3.5 Assessment Management .................................................................................. ES-10
ES-3.6 Recommendations for Additional Activities ....................................................... ES-10
ES-3 Financial Plan ..................................................................................................................... ES-11
1. Introduction .........................................................................................................................................1-1
Purpose and Objectives ..........................................................................................................1-1 1.1
Approach and Document Organization .................................................................................1-2 1.2
2. Background .........................................................................................................................................2-1
Storm Drainage Utility .............................................................................................................2-1 2.1
2.1.1 Organizational Structure ..........................................................................................2-1
2.1.2 Funding Mechanisms ...............................................................................................2-2
Development Code and Design Standards Updates ............................................................2-4 2.2
Regulatory Considerations .....................................................................................................2-5 2.3
2.3.1 Growth Management Act .........................................................................................2-6
2.3.2 Phase II Municipal Stormwater Permit ....................................................................2-7
2.3.3 Governmental Accounting Standards Board ..........................................................2-8
3. Utility Policies and Level-of-Service Goals.........................................................................................3-1
Level-of-Service Goals within Storm Drainage Utilities ........................................................3-1 3.1
Comp Plan Policies and Levels of Service .............................................................................3-2 3.2
3.2.1 Incorporation of Existing Comp Plan Policies Related to Storm Drainage ............3-2
3.2.2 Levels of Service .......................................................................................................3-4
4. Drainage System ................................................................................................................................4-1
Natural Drainage.....................................................................................................................4-1 4.1
4.1.1 Green River ...............................................................................................................4-1
4.1.2 White River ................................................................................................................4-2
4.1.3 Mill Creek ..................................................................................................................4-2
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4.1.4 Drainage Areas ......................................................................................................... 4-3
4.1.5 Climate and Precipitation ........................................................................................ 4-3
4.1.6 Geology and Groundwater ....................................................................................... 4-4
4.1.7 Soils and Runoff Potential ....................................................................................... 4-4
4.1.8 Land Use and Development .................................................................................... 4-5
4.1.9 Flood Hazard Mapping ............................................................................................. 4-6
Stormwater Drainage Infrastructure ..................................................................................... 4-7 4.2
Critical Facilities ..................................................................................................................... 4-8 4.3
Water Quality .......................................................................................................................... 4-9 4.4
4.4.1 Existing Conditions ................................................................................................... 4-9
4.4.2 Regulatory Compliance .......................................................................................... 4-10
Existing Drainage Problems ................................................................................................. 4-10 4.5
5. Evaluation of the Storm Drainage Utility .......................................................................................... 5-1
Hydraulic Evaluation .............................................................................................................. 5-1 5.1
5.1.1 Updating Existing Models ........................................................................................ 5-2
5.1.2 Creating New Models ............................................................................................... 5-2
Asset Management Evaluation .............................................................................................. 5-3 5.2
Environmental Investigation .................................................................................................. 5-6 5.3
6. Maintenance and Operations ............................................................................................................ 6-1
Utility Responsibility and Authority ........................................................................................ 6-1 6.1
6.1.1 Organizational Structure .......................................................................................... 6-1
6.1.2 Staffing Level............................................................................................................ 6-1
6.1.3 Level of Service ........................................................................................................ 6-2
6.1.4 Training and Education ............................................................................................ 6-2
Routine Operations Provided by the Storm Drainage Utility ................................................ 6-3 6.2
6.2.1 Catch Basin and Manhole Inspection, Cleaning, and Repair ................................ 6-3
6.2.2 Stormwater Pipeline Cleaning and CCTV ................................................................ 6-3
6.2.3 Stormwater Outfall Inspection, Cleaning, and Maintenance ................................ 6-4
6.2.4 Drainage Ditch Maintenance and Restoration ...................................................... 6-4
6.2.5 Stormwater Pond and Swale Inspection, Maintenance, and Restoration ........... 6-4
6.2.6 Culvert Inspection and Cleaning ............................................................................. 6-5
6.2.7 General Facility Maintenance and Other Field Tasks ............................................ 6-5
Routine Operations Provided to the Storm Drainage Utility ................................................ 6-5 6.3
6.3.1 Vegetative Maintenance .......................................................................................... 6-5
6.3.2 Stormwater Pump Station Maintenance ................................................................ 6-5
6.3.3 Stormwater Pond Maintenance by King County .................................................... 6-6
6.3.4 Stormfilter Maintenance.......................................................................................... 6-6
Non-Routine and Emergency Operations.............................................................................. 6-6 6.4
6.4.1 Customer Service Requests .................................................................................... 6-7
6.4.2 Emergency Response Program ............................................................................... 6-7
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Data Collection and Record-Keeping.....................................................................................6-8 6.5
M&O Staffing Requirements ..................................................................................................6-9 6.6
6.6.1 Existing Staffing Requirements ...............................................................................6-9
6.6.2 Future Staffing Requirements and Equipment Needs ........................................ 6-10
Potential Improvement Opportunities and Capital Needs ................................................ 6-12 6.7
7. Capital Improvements ........................................................................................................................7-1
Project Prioritization ...............................................................................................................7-2 7.1
Proposed Drainage Projects...................................................................................................7-4 7.2
Programmatic Drainage Projects ........................................................................................ 7-45 7.3
8. Implementation Plan ..........................................................................................................................8-1
6-Year and 20-Year CIP ..........................................................................................................8-1 8.1
Monitoring ...............................................................................................................................8-4 8.2
8.2.1 Precipitation ..............................................................................................................8-4
8.2.2 Flow ...........................................................................................................................8-4
8.2.3 Stream and Pond Water Level .................................................................................8-7
8.2.4 Water Quality ............................................................................................................8-8
Programmatic Measures for NPDES Compliance .................................................................8-8 8.3
Future Staffing and Equipment Needs ..................................................................................8-9 8.4
8.4.1 Engineering Services ................................................................................................8-9
8.4.2 M&O Services ........................................................................................................ 8-10
Continue Implementation of Best Practices for Asset Management ............................... 8-11 8.5
8.5.1 Continue System Inventory ................................................................................... 8-11
8.5.2 Implement Economic Life Model Using Cartegraph Data ................................... 8-12
8.5.3 Economic Life Model Improvements .................................................................... 8-12
8.5.4 Maintenance and R&R Prioritization .................................................................... 8-13
8.5.5 M&O Activities........................................................................................................ 8-13
Recommendations for Additional Activities ....................................................................... 8-14 8.6
8.6.1 Develop Easement Review and Acquisition Program ......................................... 8-14
8.6.2 Risk Assessment/Asset Vulnerability Analysis .................................................... 8-14
8.6.3 Incorporate Sustainability ..................................................................................... 8-14
9. Finance ................................................................................................................................................9-1
Past Financial Performance ...................................................................................................9-1 9.1
9.1.1 Statement of Revenues, Expenses, and Changes in Net Position ........................9-1
9.1.2 Statement of Net Position ........................................................................................9-2
9.1.3 Outstanding Debt Principal ......................................................................................9-4
Available Capital Funding Resources ....................................................................................9-5 9.2
9.2.1 Internal Utility Resources .........................................................................................9-5
9.2.2 Government Programs and Resources ...................................................................9-7
9.2.3 Public Debt Financing ..............................................................................................9-9
9.2.4 Capital Resource Funding Summary .................................................................... 9-10
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Financial Plan ....................................................................................................................... 9-10 9.3
9.3.1 Utility Fund Structure ............................................................................................. 9-11
9.3.2 Financial Policies ................................................................................................... 9-11
9.3.3 Capital Funding Plan .............................................................................................. 9-13
Financial Forecast ................................................................................................................ 9-14 9.4
9.4.1 Cash Test ................................................................................................................ 9-14
9.4.2 Coverage Test ......................................................................................................... 9-14
9.4.3 Financial Forecast Assumptions ........................................................................... 9-15
9.4.4 City Funds and Reserve Balances ........................................................................ 9-17
Existing Rate Structure and Projected Schedule ............................................................... 9-17 9.5
Affordability ........................................................................................................................... 9-18 9.6
Conclusion ............................................................................................................................ 9-19 9.7
10. Limitations .................................................................................................................................... 10-1
11. References ................................................................................................................................... 11-1
Appendix A: Western Washington Phase II Municipal Stormwater Permit ........................................... A-1
Appendix B: Phase II NPDES Stormwater Permit Compliance Work Plan ............................................. B-1
Appendix C: Hydrologic and Hydraulic Modeling and Evaluation .......................................................... C-1
Appendix D: SEPA Compliance ................................................................................................................ D-1
List of Figures
Figure ES-1. NPDES Compliance Schedule .......................................................................................... ES-9
Figure ES-2. Implementation Plan Activities Timeline ........................................................................ES-13
Figure 2-1. Community Development and Public Works Department Staff Organizational Chart ...... 2-2
Figure 4-1. Natural Drainage Features of the City of Auburn .............................................................. 4-13
Figure 4-2. Drainage Subareas for the City of Auburn Storm Drainage Utility .................................... 4-15
Figure 4-3. Surface Geology in the Vicinity of the City of Auburn ........................................................ 4-17
Figure 4-4. Land Use Designations for the City of Auburn ................................................................... 4-19
Figure 4-5. Drainage Infrastructure for the City of Auburn Storm Drainage Utility ............................. 4-21
Figure 4-6. City and Storm Drainage Critical Facilities for the City of Auburn .................................... 4-23
Figure 4-7. Drainage Problem Locations for the Storm Drainage Utility ............................................. 4-25
Figure 5-1. Drainage Pipe Summary ....................................................................................................... 5-5
Figure 7-1. Project Locations, Storm Drainage Utility Capital Improvement Program ......................... 7-3
Figure 7-2. Project 1: West Main Street Pump Station Upgrade ........................................................... 7-7
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Figure 7-3. Project 2: 37th and I Streets NW Storm Improvements ................................................... 7-11
Figure 7-4. Project 3: Hillside Drainage Assessment........................................................................... 7-15
Figure 7-5. Project 4A: 30th Street NE Area Flooding, Phase 2 .......................................................... 7-19
Figure 7-6. Project 4B: 30th Street NE Area Flooding, Phase 3 ......................................................... 7-21
Figure 7-7. Project 5A: West Hills Drainage Improvements, S 330th St. and 46th Pl. S .................. 7-25
Figure 7-8. Project 5B: West Hill Drainage Improvements, S 314th St. and 54th Ave. S ................. 7-29
Figure 7-9. Project 6: North Airport Area Improvements ..................................................................... 7-33
Figure 7-10. Project 7: D St. SE Storm Improvements ........................................................................ 7-37
Figure 7-11. Project 8: 23rd St. SE Drainage Improvements.............................................................. 7-41
Figure 8-1. Annual Costs for 6-year CIP ...................................................................................................8-3
Figure 8-2. Proposed Monitoring Locations ............................................................................................8-6
Figure 8-3. NPDES Compliance Schedule ...............................................................................................8-9
Figure 8-4. Implementation Plan Activities Timeline ........................................................................... 8-17
List of Tables
Table ES-1. Level-of-Service Goals ........................................................................................................ ES-2
Table ES-2. Project Cost Summary for 6- and 20-Year CIP ................................................................. ES-6
Table ES-3. Proposed Flow Monitoring Sites ........................................................................................ ES-7
Table ES-4. Proposed Water Level Monitoring Sites ........................................................................... ES-8
Table 2-1. 2015 and 2016 Utility Rates for Storm Drainage Service ...................................................2-3
Table 2-2. Federal, State, and City Regulations and Programs Relevant to the Auburn
Storm Drainage Utility .......................................................................................................................2-5
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 Auburn .....................................................4-6
Table 4-3. Stormwater Drainage Infrastructure Summary .....................................................................4-7
Table 4-4. Critical City Facilities ...............................................................................................................4-8
Table 4-5. Critical Stormwater Facilities ..................................................................................................4-9
Table 4-6. Existing Drainage Problems ................................................................................................. 4-11
Table 6-1. Storm Drainage Utility M&O Personnel ..................................................................................6-2
Table 6-2. Existing Storm Drainage System Maintenance and Staffing Requirements .......................6-9
Table 6-3. Future Storm Drainage System Maintenance and Staffing Requirements ...................... 6-11
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Table 7-1. Summary Programmatic Drainage Projects ........................................................................ 7-45
Table 8-1. Annual Project Cost Summary for 6-Year CIP ....................................................................... 8-2
Table 8-2. Cost Summary for 20-Year CIP .............................................................................................. 8-4
Table 8-3. Proposed Flow Monitoring Sites ............................................................................................ 8-5
Table 8-4. Proposed Water Level Monitoring Sites ................................................................................ 8-7
Table 8-5. Future Engineering Services Staffing Needs ...................................................................... 8-10
Table 8-6. Future Maintenance and Operations Staffing Needs ......................................................... 8-11
Table 9-1. Statement of Revenues, Expenses and Changes in Fund Net Position .............................. 9-2
Table 9-2. Statement of Net Position ...................................................................................................... 9-2
Table 9-3. Outstanding Debt .................................................................................................................... 9-5
Table 9-4. Current System Development Charge Schedule .................................................................. 9-6
Table 9-5. Drainage CIP ......................................................................................................................... 9-13
Table 9-6. Capital Financing Plan .......................................................................................................... 9-14
Table 9-7. Financial Forecast ................................................................................................................ 9-16
Table 9-8. Cash Balance Summary ....................................................................................................... 9-17
Table 9-9. Projected Rate Schedule ...................................................................................................... 9-18
Table 9-10. Affordability Test ................................................................................................................. 9-19
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List of Abbreviations
§ section
ACC Auburn City Code
BAB Build America Bonds
BMP best management practice
CCTV closed-circuit television
CEMP City’s Emergency Management Plan
CERB Community Economic Revitalization Board
cfs cubic foot/feet per second
CIP Capital Improvement Program
CMMS computerized maintenance management
system
Comp Plan Comprehensive Plan for the City of
Auburn (Land Use Plan)
CWA Clean Water Act
DEM Digital Elevation Model
Drainage Plan Comprehensive Storm Drainage Plan
Ecology Washington State Department of Ecology
Engineering Engineering Services (division within
Community Development and Public
Works)
EPA Environmental Protection Agency
ESA Endangered Species Act
ESU equivalent service unit
EWE Energy and Water Efficiency
FEMA Federal Emergency Management Agency
FIRM Flood Insurance Rate Map
FIS Flood Insurance Study
FTE full-time equivalent
GASB Governmental Accounting Standards Board
GIS geographic information system
GMA Growth Management Act
GO general obligation
HDPE high-density polyethylene
H&H hydrologic and hydraulic
HPA Hydraulic Project Approval
IDDE illicit discharge detection and elimination
KCFCD King County Flood Control Zone District
LFC local facilities charge
LID low-impact development
LOS level of service
LOMR Letter of Map Revision
MACP Manhole Assessment and Certification
Program
MEP maximum extent practicable
M&O maintenance and operations
MS4 municipal separate storm sewer system
NASSCO National Association of Sewer Service
Companies
NAVD88 North American Vertical Datum 1988
NFIP National Flood Insurance Program
NOAA National Oceanic and Atmospheric
Administration
NPDES National Pollutant Discharge Elimination
System
NPDES Permit Western Washington Phase II
Municipal Stormwater Permit
NRCS Natural Resources Conservation Service
NSF non-single-family
PACP Pipeline Assessment and Certification Program
PWB Public Works Board
RCW Revised Code of Washington
ROW right-of-way
R&R repair and replacement
RSI required supplementary information
SCADA supervisory control and data acquisition
SDC system development charge
SEPA State Environmental Policy Act
SFAP Stormwater Financial Assistance Program
SFHA Special Flood Hazard Area
SR State Route
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SRS software requirement specification
SWIF System Wide Improvement Framework
SWMM Surface Water Management Manual
SWMP Stormwater Management Program
TMDL total maximum daily load
ULID utility local improvement district
USACE U.S. Army Corps of Engineers
VRFA Valley Regional Fire Authority
WAC Washington Administrative Code
WRCC Western Regional Climate Center
WSDOT Washington State Department of
Transportation
ES-1
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Executive Summary
This Comprehensive Storm Drainage Plan (Drainage Plan) for the City of Auburn (City) updates the
previous plan, which was completed in 2009. The update was done to address new regulatory
requirements, refine and document maintenance and operations (M&O) practices and assess staffing
needs, update the list of projects for the Capital Improvement Program (CIP), and develop a current
financial plan. This new Drainage Plan is intended to guide future activities and improvements for the
storm drainage system based on an asset management approach.
This Drainage Plan was developed through the following steps:
• Review relevant information regarding the Storm Drainage Utility organizational structure, funding
mechanisms, and regulatory drivers (Chapter 2).
• Review and update the level-of-service (LOS) goals in light of current Storm Drainage Utility
responsibilities and new regulatory requirements (Chapter 3). LOS goals are policy- and community-
based objectives for capital facility infrastructure development, operation, maintenance, and other
Storm Drainage Utility activities.
• Characterize the current and expected future conditions of the natural and constructed drainage
systems (Chapter 4) and identified drainage problems. The constructed drainage system requires a
detailed system inventory for use in analyses and asset management.
• Evaluate the Storm Drainage Utility to identify potential gaps between the LOS goals and current or
expected future service levels (Chapter 5). Evaluations included hydraulic analyses of the drainage
system, asset life-cycle analyses, environmental investigations, and review of M&O activities
(Chapter 6).
• Evaluate alternatives to reduce or eliminate identified gaps in service (Chapter 7) and select the
measures to be included in the Drainage Plan based on detailed hydraulic modeling, estimated
costs, and other factors.
• Establish the implementation plan, which is the future work plan for the Storm Drainage Utility
(Chapter 8). Capital improvement projects from Chapter 7 were prioritized and placed into 6-year
and 20-year CIP time frames. Non-capital works recommendations such as flow monitoring,
regulatory compliance, future staffing needs improvements, additional asset management best
practices, and additional programs and analysis are also included in the implementation plan.
• Prepare a financial plan (Chapter 9) to support the costs associated with proposed improvements.
This Drainage Plan contains implementation for future actions and decisions. These time frames could
change depending on factors such as scheduling of project work, funding, and future opportunities to
coordinate with non-Storm Drainage Utility projects such as road improvements. Therefore, the time
frames are intended as guidance only and do not represent actual commitments by the City.
The following sections summarize the development of the Drainage Plan and outline the
recommendations contained in the implementation plan and a summary of the financial plan.
ES-1 LOS Goals
LOS goals provide a framework for the Storm Drainage 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 for evaluating Storm Drainage Utility performance. LOS goals are based on existing City
Executive Summary Comprehensive Storm Drainage Plan
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policies as presented in the Comprehensive Plan for the City of Auburn (Comp Plan). LOS goals and
associated City policies are summarized in Table ES-1.
Table ES-1. Level-of-Service Goals
Item Policy description 2015 Drainage Plan LOS goal
Policy category: business practices
1
The City desires to employ recognized best business
practices that result in the efficient and cost-effective
operation of the utility. See proposed new policy CF-XX.
The City shall identify the key business functions within the utility (e.g., billing,
permitting, asset management, and planning) and develop supporting best
business practices for each. The utility will conduct a performance audit every 6
years in conjunction with its capital projects planning cycle to evaluate how well
best business practices are being implemented and how effective they are.
2
The City shall seek to employ the best practices for
asset management by systematically basing choices on
an understanding of asset performance, risks, and
costs in the long term. See proposed new policy CF-XX.
The City shall begin implementing the following best practices for all stormwater
facilities during the next planning period and report progress annually:
• Have knowledge about assets and costs (i.e., detailed inventories and
condition assessments)
• Maintain desired levels of service confirmed by customers
• Take a life-cycle approach to asset management planning
Implement the planned solutions to provide reliable, cost-effective service
Policy category: protection of public safety and property
3
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% (i.e., an average recurrence interval of 100 years).
4
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% (i.e., an average recurrence
interval of 25 years).
5
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).
6
The City shall seek to prevent erosion and landslides
related to construction, operation, and maintenance of
the publicly owned drainage system. See policies CF-
48 and EN-3.
No erosion or landslides resulting from public drainage infrastructure
construction, operation, or maintenance.
7
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, CF-
42, and EN-17.
The City will continue to 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. All activities will be documented within the City’s Cartegraph
computerized maintenance management system (CMMS).
Policy category: reliability of the storm drainage infrastructure
8
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 the 2008 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 Cartegraph CMMS.
9 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 all
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 all condition
assessment activities will be documented in the City’s Cartegraph CMMS.
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Table ES-1. Level-of-Service Goals
Item Policy description 2015 Drainage Plan LOS goal
10
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.
11
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 catch basins). The experience of
M&O staff should be incorporated into the criticality database (see item 8
above). All inspection activities will be documented in the CMMS.
12
The City shall seek to maintain storm drainage
infrastructure to ensure proper function of drainage
facilities in accordance with Ecology requirements. See
policies CF-40, CF-42, and EN-15.
The City will develop a ditch maintenance program. The City will secure proper
permits as well as coordinate with other agencies for work in the associated
ROW. The ditch maintenance program will consist of inspecting and maintaining
all ditches within the permit cycle and then on an as-needed basis.
13
The City shall seek to manage stormwater runoff from
the public ROW with City-owned facilities located in the
public ROW or on City-owned property. The City shall
maintain or seek access to City-owned facilities for
necessary maintenance and operation. See policy EN-
17.
The City’s Storm Drainage Utility will be responsible for maintenance and
operation of the City’s drainage system. The City shall seek to have access to all
City-owned drainage infrastructure. The City shall seek to obtain easements or
relocate infrastructure as necessary to maintain access.
Policy category: protection of the environment
14
The City shall seek to comply with all federal and state
regulations applied to stormwater management
activities. See policy GP-23.
Meet all requirements of the Western Washington Phase II Municipal Stormwater
Permit with no enforcement actions of the CWA for violations as a result of City
stormwater operations.
15
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.
All 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.
16
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.
17
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.
18
The City shall seek to comply with all federal, state, and
local regulations to reduce runoff volumes and
pollutant loads associated with new development and
redevelopment. See policies CF-51 and EN-15.
The City will comply with the elements of the Western Washington Phase II
Municipal Stormwater Permit and will adopt or implement the Ecology manual or
equivalent for new development and redevelopment.
19
The City shall place emphasis on onsite approaches
such as LID as the first consideration for runoff and
pollutant load reduction for new development and
redevelopment. See policy EN-17A.
The City will identify feasibility criteria and provide guidance for the
implementation of LID drainage management measures for new development
and redevelopment (including City-owned properties).
20
The City shall seek to evaluate Storm Drainage Utility
activities to emphasize sustainability. See policy GP-
28a.
City staff will identify specific areas to measure sustainability by examining how
Storm Drainage Utility operations affect energy resources, natural resources,
and the community. City staff will benchmark practices and log changes over the
next planning period.
21
The City shall continue to participate in regional storm
drainage, water resources, and water quality planning
efforts. See policies CF-48, CF-50, 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. The City will participate
in the state’s water quality monitoring program.
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Table ES-1. Level-of-Service Goals
Item Policy description 2015 Drainage Plan LOS goal
22
The City shall comply with all federal, state, and local
regulations in the inspection of the City’s publicly
owned storm drainage infrastructure and privately
owned LID facilities. See policy CF-42.
For all new LID systems constructed after 2016, the City will develop authority
and an inspection frequency for stormwater facilities developed in compliance
with the NPDES Phase II Stormwater Permit. The City will develop an inspection
assessment database to monitor and schedule facility maintenance for all
publicly owned storm drainage infrastructure and privately owned LID facilities.
This database will provide maintenance information for the criticality database
in the City’s Cartegraph CMMS.
Policy category: Storm Drainage Utility financial performance
23
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, with a goal of 100%
of the cost of drainage service delivery recovered via Storm Drainage Utility fees.
Seek opportunities to provide public drainage benefits through grant funding
and/or development partnerships where applicable.
24
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 all 6-year CIP updates.
25 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 evaluate methods to reduce the risk of claims
and measure its progress at reducing the overall cost of claims.
26
The City shall seek to track elements of capital
improvement project 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 capital improvement project
implementation to create a baseline (e.g., schedule and costs) against which
future improvements can be evaluated.
Policy category: customer satisfaction
27
The City shall seek to evaluate and strive to maintain
customer satisfaction with Storm 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 Western Washington Phase II
Municipal Stormwater Permit requirements for public education and outreach.
28
The City shall seek to build, operate, and maintain
storm drainage 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 Storm Drainage Utility
A series of analyses were conducted to evaluate the Storm Drainage Utility and identify gaps between
existing service levels and the desired LOS goals. The following evaluations were completed as:
• Hydraulic: Hydraulic evaluations consisted of using hydraulic models covering locations of existing
problems to evaluate problems and develop capital improvement projects. Existing hydraulic models
were updated based on recent geographic information system (GIS) data, design drawings, and
record drawings. Some model updates also included calibration to flow monitoring data that were
collected in 2010 and 2011. For problem areas that had not been previously modeled, new models
were developed to estimate flow for capital improvement project sizing.
• Asset management: Asset life-cycle evaluations require detailed system information. System data
(e.g., pipe material, pipe age, and proximity to critical facilities), which are stored in the City’s
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Cartegraph CMMS, are used for such an analysis. This Drainage Plan includes a recommendation for
implementing the economic life model using the data in Cartegraph.
• Environmental: Environmental evaluations centered on regulatory compliance for the 2013–18
National Pollutant Discharge Elimination System (NPDES) Western Washington Phase II Municipal
Stormwater Permit (NPDES Permit). The permit was compared to the previous permit to identify
additional requirements that could affect City regulations, facilities, and activities. The results were
used to identify gaps and develop potential actions to comply with the NPDES Permit conditions over
the permit period. The results of that effort, including as they affect Storm Drainage Utility staffing
needs, are summarized in this Drainage Plan. The Compliance Work Plan, which outlines and guides
compliance activities over the current permit term, was also updated based on the results of the
analysis and is provided as an appendix to this Drainage Plan.
• Maintenance and operations: Existing M&O activities were evaluated to establish a baseline
understanding of the preventive and responsive maintenance procedures currently performed by
City Storm Drainage Utility M&O staff. The results were compared to LOS goals in order to estimate
Storm Drainage Utility staffing, data collection, computerized record-keeping, and other Storm
Drainage Utility needs. This plan identifies recommendations for improving existing services or work
productivity and for regulatory compliance.
ES-3 Implementation Plan
The implementation plan is intended to serve as the work plan for the Storm Drainage Utility. The
implementation plan consists of 6-year and 20-year CIPs, 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. The capital improvement projects are designed to mitigate flooding
in these areas and are expected to provide immediate benefits. The 6-year CIP also contains ongoing
programmatic efforts, such as the Storm Drainage Utility’s participation in the Street Utility
Improvements 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 and replacement (R&R) 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. The 20-
year CIP includes R&R. Table ES-2 lists the 12 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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Table ES-2. Project Cost Summary for 6- and 20-Year CIP
Project
number Project name Priority Repair/
Replacement
Upgrade/
Expansion
6-year CIP 2022–35 Total project
costs, $a 2016 2017 2018 2019 2020 2021
1 West Main Street Pump Station
Upgrade 1 100% 2,968,000 2,968,000
2 37th and I Streets NW Storm
Improvements 1 100% 291,000 291,000
3 Hillside Drainage Assessment 1 100% 139,000 150,000 289,000
4A 30th Street NE Area Flooding, Phase 2 2 100% 896,000 896,000
4B 30th Street NE Area Flooding, Phase 3 3 100% 2,124,000 2,124,000
5A West Hills Drainage Improvements at S
330th St. and 46th Pl. S 2 100% 317,000 317,000
5B West Hills Drainage Improvements near
S 314th St. and 54th Ave. S 3 100% 408,000 304,000 712,000
6 North Airport Area Improvements 2 100% 218,000 218,000
7 D St. SE Storm Improvements 2 100% 1,827,000 1,827,000
8 23rd St. SE Drainage Improvements 3 100% 316,500 316,500 633,000
9 Comprehensive Storm Drainage Plan
update 1 35% 65% 300,000 300,000
10 Composting Facility 1 100% 750,000 22,000 23,100 24,300 25,600 533,800 1,379,000
11 Storm Drainage Infrastructure Repair &
Replacement Program 1 100% 100,000 1,000,000 100,000 1,000,000 100,000 1,000,000 7,700,000 11,000,000
12 Street Utility Improvements 1 100% 100,000 100,000 100,000 100,000 100,000 100,000 1,400,000 2,000,000
Total CIP cost for priority 1 projects 3,598,000 2,000,000 222,000 1,123,100 524,300 1,125,600 9,633,800 18,227,000
Total CIP cost for priority 2 projects 535,000 896,000 1,827,000 0 0 0 0 3,258,000
Total CIP cost for priority 3 projects 0 0 724,500 2,124,000 304,0000 316,500 0 3,469,000
Total CIP cost $4,133,000 $2,896,000 $2,707,000 $3,247,100 $828,300 $1,442,100 $9,633,800 $24,954,000
a. Project costs are in 2014 dollars.
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ES-3.2 Monitoring
Precipitation, stormwater flow, and water level data are needed to simulate rainfall-runoff processes with
hydrologic and hydraulic (H&H) models. Precipitation is the source of stormwater runoff, and
precipitation intensity and duration data are needed to drive H&H models. The City currently collects
rainfall data with a rain gauge at City Hall. Stormwater flow data, such as flow rates, runoff volumes, and
flooding elevations, are needed to calibrate models to assess the current capacity of the storm drainage
system and develop potential capital improvement projects. Water level data can be useful for
evaluating the performance of stormwater ponds and assessing the risk of overtopping. Water level
monitoring in creeks to which the City’s system discharges can be helpful to evaluate water level
changes due to restoration and culvert replacement activities, and their impacts on the storm drainage
system.
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 flow monitoring data collection
for two potential problem areas. Table ES-4 summarizes specific recommendations for ongoing water
level data collection at existing creek and pond locations, as well as additional pond locations.
Table ES-3. Proposed Flow Monitoring Sites
Site numbera Location Purpose Measurement Start
year Approx. durationb
Potential problem area: Riverwalk Drive and Howard Road (increasing the tributary area to 17th and 21st street ponds)
P1012-
C690_C689
Intersection of
Auburn Way S and
Riverwalk Dr. SE
Quantify flow from upstream areas tributary to
flow control device in CB1012-C688 Depth and velocity 2016 1 to 2 wet seasons
CB1012-C688
Intersection of
Auburn Way S and
Riverwalk Dr. SE
Estimate flows to high flow ditch on Riverwalk Dr.
SE Depth 2016 1 to 2 wet seasons
C1111-
C1469_C1470
Intersection of
Howard Rd. and
Riverwalk Dr. SE
Quantify flows to support modeling flows that
may be connected to the City’s system at
CB1011-C1474
Depth and velocity 2016 1 to 2 wet seasons
P1011-
C1452_C1453
Howard Rd. between
21st St. SE and
Riverwalk Dr. SE
Quantify flows to support modeling flows that
may be connected to the City’s system at
CB1011-C1474
Depth and velocity 2016 1 to 2 wet seasons
P1011-
C1086_C1137
Howard Rd. between
21st St. SE and
Riverwalk Dr. SE
Quantify flows to support modeling flows that
may be connected to the City’s system at
CB1011-C1474
Depth and velocity 2016 1 to 2 wet seasons
P1010-C3_C29 Howard Rd. near
Auburn Way S
Provide data for H&H model calibration
(subbasin C) Depth and velocity 2016 1 to 2 wet seasons
P1010-
B220_B221
21st and K Streets
SE
Provide data for H&H model calibration
(subbasin C) post-CIP (AWS Phase 2)c Depth and velocity 2016 1 to 2 wet seasons
Potential problem area: 2nd and G streets SE
P909-
C122_C121
Auburn Way S, near
9th St. SE
Quantify flows upstream of flow split (at MH 909-
C12) between subbasins B and C, and provide
data for H&H model calibration
Depth and velocity Post-AWS
Phase 2c,d
1 to 2 wet seasons
P809-
C113_C112
F St. SE, north of SR
18
Quantify flows upstream of sewer crossing, and
provide data for H&H model calibration Depth and velocity Post-AWS
Phase 2c,d
1 to 2 wet seasons
P810-
C701_809-C18
G St. SE and E Main
St.
Provide data for H&H model calibration
(subbasin C) Depth and velocity Post-AWS
Phase 2c,d
1 to 2 wet seasons
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Table ES-3. Proposed Flow Monitoring Sites
Site numbera Location Purpose Measurement Start
year Approx. durationb
P810-C698_C16 M St. SE, south of E
Main St.
Provide data for H&H model calibration since M
St. Grade Separation and Well 1 Transmission
Projects implementation
Depth and velocity Post-AWS
Phase 2c,d
1 to 2 wet seasons
P810-C15_C241 E Main St. and N St.
SE Estimate backwater effects on drainage system Depth and velocity Post-AWS
Phase 2c,d 1 to 2 wet seasons
a. P = pipe, C = culvert, CB = catch basin, MH = manhole.
b. Data to support CIP need 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. Monitoring period and duration within a potential problem area should be
the same.
c. Relieve Auburn Way S Flooding; Phase 2 (AWS Phase 2) is planned for construction in 2015.
d. Detailed survey of the flow split at MH 909-C12 should be completed prior to flow monitoring, to understand system hydraulics at this
location.
Table ES-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 Ongoing since 2011 10 yearsa
WL-Mill-02 Mill Creek at 29th St. NW Evaluate stages in Mill Creek and assess backwater
effects on drainage system Ongoing since 2011 10 yearsa
WL-Mill-03 Mill Creek at 15th St. NW Evaluate stages in Mill Creek and assess backwater
effects on drainage system Ongoing since 2011 10 yearsa
WL-Mill-04 Mill Creek at West Main St. Evaluate stages in Mill Creek and assess backwater
effects on drainage system Ongoing since 2011 10 yearsa
WL-Pond-17thSt 17th and A streets SE Monitor pond performance (water levels and infiltration
rates) Ongoing since 2010 Indefiniteb
WL-Pond-21stSt 21st and D streets SE Monitor pond performance (water levels and infiltration
rates) Ongoing since 2011 Indefiniteb
WL-Pond-RiverN Riverwalk Dr. SE and U St. SE
Monitor pond performance (water levels and infiltration
rates) and evaluate capacity in support of analysis for
potential problem area at Riverwalk and Howard Road
2015 Indefiniteb
WL-Pond-LakeS1 Lakeland South Pond 1 Monitor water level to evaluate hazard risk (dam safety) 2015 Indefiniteb
WL-Pond-LakeS2 Lakeland South Pond 2 Monitor water level to evaluate hazard risk (dam safety) 2015 Indefiniteb
WL-Pond-LakeEP Lakeland East Pond Monitor water level to evaluate hazard risk (dam safety) 2015 Indefiniteb
WL-Pond-Mill Mill Pond (Oravetz Rd. SE) Monitor water level to evaluate hazard risk (dam safety) 2015 Indefiniteb
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. To be continually reevaluated; if data indicate that stormwater pond is performing adequately or has low risk of failure, then monitoring
could cease.
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ES-3.3 Programmatic Measures for NPDES Compliance
As part of NPDES, the City of Auburn is covered by the NPDES Permit, which regulates stormwater
discharges from the City’s municipal separate storm sewer system (MS4). The City is actively engaged in
stormwater management activities to comply with the Permit, including the following:
• Stormwater management plan administration
• Public education and outreach
• Public involvement and participation
• Illicit discharge detection and elimination (IDDE)
• Control of runoff from new development, redevelopment, and construction sites
• Municipal operations and maintenance
• Monitoring and assessment
The compliance schedule for key NPDES Permit requirements is included in Figure ES-1. The City of
Auburn 2015 Stormwater Management Program Plan (City of Auburn, March 2015) provides additional
details regarding the City’s NPDES compliance activities.
Figure ES-1. NPDES Compliance Schedule
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ES-3.4 Future Staffing and Equipment Needs
Current Engineering Services (Engineering) and M&O staff and equipment were reviewed in light of
anticipated NPDES Permit requirements as well as existing and future M&O responsibilities. Based on
this evaluation, the following additional staff and equipment are recommended:
• 1.15 full-time equivalent (FTE) Engineering Services
• 3.3 FTE M&O Services
• Closed-circuit television (CCTV) inspection equipment
• Excavator for ditch and stormwater pond maintenance
ES-3.5 Assessment Management
Additional recommendations were made for activities to support asset management and ongoing M&O:
• Continue system inventory: The City should continue its comprehensive system inventory and the
inventory should be continually updated to reflect additional data collected during maintenance
activities (i.e., condition assessment and frequency of maintenance activities) and drainage system
changes through capital improvement projects.
• Implement economic life model using Cartegraph data: The City should implement the economic life
model for the pipes in its stormwater collection system using Cartegraph CMMS as a primary data
source. Improvements to the model should also be implemented including incorporating City data on
costs and failure rates, as well as adding catch basins and manholes to the model.
• Optimize M&O program: The City should continue to use the economic life model to optimize M&O
activities. Model results can be used to prioritize M&O activities and R&R for the assets for which the
City is carrying most of its risk. The City should continue the implementation of the National
Association of Sewer Service Companies (NASSCO) Pipeline Assessment and Certification Program
(PACP) and Manhole Assessment and Certification Program (MACP) certified inspection programs to
allow integration of inspection and condition assessment results with Cartegraph. The City should
also provide staff training to ensure assessment consistency.
ES-3.6 Recommendations for Additional Activities
Additional recommendations were made for activities that will support the Storm Drainage Utility in
meeting its LOS:
• Develop easement review and acquisition program: Parts of the City’s drainage network, particularly
in areas annexed from King County, are located outside of the right-of-way (ROW) and cross private
property without easements. The City should develop a process to ensure that it can meet the LOS
goal related to having access to City-owned facilities for M&O activities.
• Conduct 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, hospitals, fire stations, M&O, City Hall, and City
Hall Annex. 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.
• Incorporate sustainability: The City should take steps toward incorporating sustainability into Storm
Drainage Utility activities. Recommended actions include developing specific and measurable
sustainability goals for the Storm Drainage Utility and establishing standards that incorporate
sustainability into project and activities.
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A timeline (Figure ES-2) was developed to illustrate how each of the recommended activities in the
implementation plan fit together within the 6-year and 20-year time frames.
ES-3 Financial Plan
A financial plan was developed to identify the total cost of providing storm drainage service and to
provide a financial program that allows the Storm Drainage Utility to remain financially viable during
execution of the CIP. The viability analysis considered the historical financial condition of the Storm
Drainage Utility, sufficiency of utility revenues to meet current and future financial and policy obligations,
and financial impact of executing the CIP. The plan also provides a review of the Storm Drainage Utility’s
rate structure with respect to rate adequacy and customer affordability.
The financial analysis indicated that the adopted rates should be sufficient to meet the predicted Storm
Drainage Utility financial obligations through 2018 with minimal bonds. An average rate increase of 2.6
percent is required to meet Storm Drainage Utility financial obligations for 2019 through 2021. The
evaluation also found that the projected rates would remain well within the defined threshold of
affordability
2016 2017 2018 2019 2020 2021 2022 2035
1. West Main Street Pump Station Upgrade
2. 37th and I Streets NW Storm Improvements
3. Hillside Drainage Assessment
4A. 30th Street NE Area Flooding, Phase 2
4B. 30th Street NE Area Flooding, Phase 3
5A. West Hills Drainage Improvements at S 330th St. & 46th Pl. S
5B. West Hills Drainage Improvements near S 3114th St. & 54th Ave. S
6. North Airport Area Improvements
7. D St. SE Storm Improvements
9. Composting Facility
10. Storm Drainage Infrastructure Repair & Replacement
11. Street Utility Improvements
Q1Q2Q3Q4
Pipe 1011-C1086_1011-C1137
Pipe 1011-C1452_1011-C1453
Culvert 1111-C1469_1111-C1470
Catch basin 1012-C688
Pipe 1012-C690_1012-C689
Pipe 1010-C3_1010-C29
Pipe 1010-B220_1010-B221
WL-Mill-01,02,03,04. Mill Creek Profile
WL-Pond-17thSt. 17th and A Streets SE
WL-Pond-21stSt. 21st and D Streets SE
WL-Pond-RiverN. Riverwalk Dr. SE and U St. SE
WL-Pond-LakeS1, -LakeS2, -LakeEP& -Mill
Detailed 6-year CIP Time Frame
Annual inspections of City-approved facilities constructed under
terms of permit
Adopt 2012 Ecology Manual or equivalent manual
Measure effectiveness of public outreach
En
d
o
f
N
P
D
E
S
Pe
r
m
i
t
Establish specific sustainability goals and standards
Continue system inventory
Conduct new economic life-cycle analyses
Implement economic life-model using Cartegraph data
Implement additional M&O activities
Develop easement review and acquisition program
Remaining 20-year CIP Summary
Q1Q2Q3Q4Q1Q2Q3Q4Q1Q2Q3Q4Q1Q2Q3Q4Q1Q2Q3Q4
IMPLEMENTATION PLAN ACTIVITIES TIMELINE
City of Auburn Comprehensive Storm Drainage Plan
Additional Activities (Section 8.5)
NPDES Compliance (Section 8.3)
Monitoring (Section 8.2)
CIP (Section 8.1)
Data feed
Activity (may start before 2016)
K E Y
Risk assessment/asset vulnerability analysis
Complete one inspection of each catch basin
Review & update operations, maintenance & inspections standards
8. 23rd St. SE Drainage Improvements
Phase 1 Phase 2
Pipe 809-C113_809-C112
Pipe 909-C122_909-C121
Pipe 810-C701_809-C18
Pipe 810-C15_810-C241
Pipe 810-C698_810-C16
Complete field screening for 40% of storm drainage system
Complete field screening for 12% of storm drainage system annually
Revise ACC to reflect IDDE changes
Compile and submit a summary of LID review and revision process
Post SWMP documents to website annually
Review, revise & adopt local development codes, standards, &
policies to require LID
Phase 1 Phase 2
Timing dependent on project to
be implemented in 2015
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Chapter 1
Introduction
This Comprehensive Storm Drainage Plan (Drainage Plan) for the City of Auburn, Washington, updates
the previous plan that was completed in December 2009 and amended in 2011. An update to the 2009
Drainage Plan is 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), need to be addressed.
• Continued growth and development, especially in areas annexed from King County, requires new
and revised evaluations of the storm drainage system to maintain an understanding of existing and
potential problems throughout the utility service area.
• The system inventory has been updated and is 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 2009 Drainage Plan needs to be
reevaluated to account for completed projects, changes in system conditions, and new
development, as well as to incorporate new financial information.
• Additional capital improvement projects need to be developed for problems identified since the
2009 Drainage Plan.
This comprehensive plan contains time frames that 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.
Purpose and Objectives 1.1
The purpose of this Drainage Plan is to guide the City’s Storm Drainage Utility with respect to future
activities and improvements. The Drainage Plan’s objectives are to:
• Evaluate environmental, social, and regulatory drivers to update the level-of-service (LOS) goals for
capital facility infrastructure development, operation, maintenance, and other key elements of utility
management
• Incorporate updates to the stormwater drainage system inventory into the hydraulic models used for
analyzing the system
• Perform hydraulic modeling analysis to evaluate system capacity focusing on known problems and
areas where data are available for model development and calibration
• Identify monitoring needs for evaluating the performance of system assets, as well as for calibrating
hydraulic models in future modeling efforts
• Develop a CIP that meets required customer service levels, effectively managing risks, and
minimizing the City’s costs of drainage asset ownership
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• Document maintenance and operations (M&O) activities and develop recommendations for
improving the M&O program
• Prioritize capital improvement projects to accommodate both 6- and 20-year funding frameworks
• Incorporate information and activities from concurrent NPDES compliance planning
• Identify additional staffing needed based on NPDES requirements and future M&O activities
• Develop programmatic recommendations to address utility needs
Approach and Document Organization 1.2
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, identified problems were analyzed with respect to LOS goals, and
recommendations were developed for achieving those goals.
This Drainage Plan is organized in a way that focuses on the actions the utility will take while
implementing the plan. In most cases, supporting documentation and background information is
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 Storm Drainage 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 Drainage System: describes the existing conditions of the City’s drainage system
Chapter 5 Evaluation of the Storm Drainage Utility: describes methodologies used to evaluate existing
problems and develop capital improvement projects
Chapter 6 Maintenance and Operations: documents existing Storm Drainage Utility M&O activities
Chapter 7 Capital Improvements: describes recommended capital improvement projects including
cost estimates and conceptual figures
Chapter 8 Implementation Plan: prioritizes capital improvement projects and lays out a future work
plan
Chapter 9 Finance: 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 10 Limitations
Chapter 11 References
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Chapter 2
Background
This chapter provides a brief description of the Storm Drainage 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.
Storm Drainage Utility 2.1
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 system 1.
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 210 miles of pipe, 40 miles of ditches, more than
11,000 catch basins and manholes, 293 storage and water quality facilities, and 7 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 Storm Drainage Utility and
funding mechanisms, respectively.
2.1.1 Organizational Structure
The City’s Storm Drainage Utility is organized under the larger umbrella of the Community Development
and Public Works Department. This department covers six basic areas of responsibility:
• Water Utility Program
• Sanitary Sewer Utility Program
• Storm Drainage Utility Program
• Transportation Program
• Maintenance and Operations Program
• Community Development Services
1 A public utility for stormwater management was established by City of Auburn Ordinance 4193 on December 15, 1986.
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Under these programs the Community Development and Public Works Department carries out long-term
planning, budget management, interaction, and regulation of development; management of capital
improvements; and maintenance and operation for the associated City facilities. Given these program
responsibilities, the Community Development and Public Works Department is divided into three
divisions: Engineering Services, Maintenance and Operation (M&O) Services, and Community
Development Services (see Figure 2-1). Planning and construction of storm drainage facilities is provided
by Engineering Services. Maintenance of storm drainage facilities is provided by a dedicated stormwater
division within M&O.
Figure 2-1. Community Development and 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 stormwater and surface waters
that benefit the service area but do not presently exist
Director of Community
Development and Public Works
Planning Services
Manager
Development Engineer
Building Official
Utilities Engineering
Manager
Transportation
Manager
General Engineering
Assistant City Engineer
Administration
Engineering Services
Assistant Director of Engineering/
City Engineer
Maintenance & Operations Services
Assistant Director of Public Works
Operations
Community Development Services
Assistant Director of Community
Development
Street/Vegetation
Manager
Water Distribution &
Operations
Manager
Sewer/Storm
Manager
Fleet/Central Stores
Manager
Administration
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• 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 that 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 that are reasonably
required for proper and adequate management of stormwater 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 that are reasonably required for the proper and adequate
implementation of the City’s stormwater and surface water policies
2.1.2.1 Rates
The currently established rates for the storm drainage service are provided in Table 2-1 below, which
lists rates for 2015 and 2016. 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 development or 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. 2015 and 2016 Utility Rates for Storm Drainage Service
Single-family parcel types Effective as of January 1, 2015 Effective as of January 1, 2016
Monthly charge Monthly charge
Single-family residential parcelsa $19.25 $19.73
Two-family residential parcelsb 19.25 19.73
Non-single-family parcels Base rate per month, $ ESUs per month Base rate per month, $ ESUs per month
Non-single-family (NSF)c $11.97 $15.32 $12.27 $15.71
NSF with detentiond 11.97 12.31 12.27 12.62
NSF with retentione 11.97 7.61 12.27 7.80
NSF with water quality treatmentf 11.97 9.21 12.27 9.44
NSF with detention and water quality treatment 11.97 6.95 12.27 7.13
NSF with retention and water quality treatment 11.97 4.35 12.27 4.46
a. Any parcel of land having on it a single detached dwelling unit that 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 stormwater and surface water runoff with provisions for the controlled offsite surface release of the
stored water.
e. Retention means the storage of stormwater and surface water runoff with no provisions for offsite 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 a
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, stormwater, garbage, sewer, and water. Payment for stormwater
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 taxes 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 and provide for future improvements to serve new
customers. As with Storm Drainage Utility rates, SDCs are based on the relative amount of impervious
surface added to the system. In 2014, SDCs were estimated to be $1,162 per ESU (see Section 2.1.2.1
for a definition of ESU).
Development Code and Design Standards Updates 2.2
In compliance with the requirements of the 2007–12 NPDES Permit (as discussed in Section 2.3.2), the
City conducted substantive updates to its development regulations and design standards contained
within the ACC, including the City’s Zoning Code, Subdivision Code, and Engineering Design Standards.
The City also revised related stormwater standards, policies, and practices, and adopted a stormwater
manual as required by the Permit. Specifically, the City adopted the Auburn Surface Water Management
Manual (SWMM), which is a modified version of the City of Tacoma’s 2008 Surface Water Management
Manual (approved by the Washington State Department of Ecology [Ecology] as an equivalent manual).
In August 2012, Ecology issued an updated NPDES Permit to comply with requirements of the federal
Clean Water Act (CWA). The new NPDES Permit became effective on August 1, 2013, and is effective
through July 31, 2018. In January 2015, a modified version of the NPDES Permit was issued to
incorporate outcomes from the permit appeals process, which were not significant for the City. To comply
with updated requirements of the reissued NPDES Permit, the City will be required to pursue further
updates to the ACC and stormwater standards.
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Updates to City codes, standards, and policies are anticipated to:
• Incorporate low-impact development (LID) principles, making LID the preferred way of managing
stormwater runoff from future development and redevelopment
• Reflect updated stormwater facility requirements for new development and redevelopment
• Accommodate new and more frequent inspections of permanent stormwater infrastructure,
including public and private stormwater facilities
• Incorporate required changes to other City stormwater program elements, including illicit discharge
detection and elimination (IDDE), public outreach and education, and monitoring
Development regulations related to stormwater and drainage design standards will also be reviewed for
potential revision consistent with current policies and LOS goals.
See the following section for an overview of the City Stormwater Management Program (SWMP) and
Chapter 8 for specific steps needed to maintain compliance with updated NPDES Permit requirements.
Regulatory Considerations 2.3
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 Storm Drainage Utility
Title Regulation
or program Application to the City
Federal
Clean Water Act (CWA): §402 NPDES
Permit Regulation The NPDES Permit includes 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 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 capital improvement project costs
and schedules.
Endangered Species Act (ESA) Regulation
Stormwater capital improvement projects that involve 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 The 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 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.
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Table 2-2. Federal, State, and City Regulations and Programs Relevant to the Auburn Storm Drainage Utility
Title Regulation
or program Application to the City
Puget Sound Partnership Program
In 2007, the Washington State Legislature created a State agency for the purpose of
developing and overseeing the implementation of a 2014/2015 “Action Agenda” to
clean up, restore, and protect Puget Sound by 2020. The Partnership’s “Action Agenda”
identified three priorities, one of which is to prevent pollution from urban stormwater
runoff.
GMA and City Comprehensive Plan Regulation This Drainage Plan is required by the GMA. GMA is discussed in Section 2.3.1 below.
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 capital improvement project 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 NPDES Permit requirements.
Shoreline Master Program 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, capital improvement projects 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 in 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. 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. Parks and recreation
facilities shall be included in the capital facilities plan element.
To facilitate meeting the above requirements, Washington Administrative Code (WAC) Section 365-196-
415 recommends:
• An inventory of existing capital facilities showing locations and capacities, including the extent to
which existing facilities have available capacity for future growth. The inventory should be
periodically reviewed and updated.
• A forecast of capital facilities (including general location and capacity) needed during the planning
period, 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 at least a 6-year capital facilities plan for financing capital facilities needed within
that time frame. Projected funding capacities based on revenues available under existing laws and
ordinances, 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 if the
probable funding for capital facilities is insufficient to meet development needs. If the reassessment
identifies a lack of public facilities, a variety of strategies may be implemented including reducing
LOS and increasing revenue.
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. Auburn is a Phase II permittee.
Ecology issued the initial Western Washington Phase II Municipal Stormwater Permit (NPDES Permit) in
February 2007, a subsequent updated NPDES Permit in August 2012, and a further modified version in
January 2015 (Appendix A). The Permit requires the City to submit a SWMP Plan by March 31 of each
year, in which the City identifies activities to be completed in compliance with the Permit requirements.
The Permit also requires submittal of an annual report that looks back on SWMP activities for the prior
year.
Implementation of updated NPDES Permit conditions is staggered throughout the 5-year Permit term
from August 1, 2013, through July 31, 2018. The NPDES Permit will again be revised and reissued at the
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end of this period. The NPDES Permit and associated requirements are described in detail in the City’s
current SWMP Plan available on the City’s website.
The NPDES 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 stormwater management activities specified in the NPDES
Permit are collectively referred to as the SWMP and grouped under the following program components:
• SWMP administration
• Public education and outreach
• Public involvement and participation
• IDDE
• Control of runoff from new development, redevelopment, and construction sites
• Municipal operations and maintenance
• Monitoring and assessment
The NPDES Permit also requires compliance with established total maximum daily loads (TMDLs)2. The
current NPDES Permit requires the City to monitor discharges to the White River, in association with the
Puyallup River watershed fecal coliform TMDL. Ecology has identified several other water bodies in the
vicinity of Auburn that do not appear to meet the water quality standards, and additional TMDL
requirements are possible in future Permits.
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 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 that include information on net assets (e.g., storm
drainage infrastructure) and a statement of activities.
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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− Fund financial statements that 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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Chapter 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 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:
• Business practices
• Protection of public safety and property
• Reliability of the storm drainage infrastructure
• Protection of the environment
• Financial performance of the utility
• Customer satisfaction
Policies for each of these six categories are presented in Section 3.2.2. The remainder of this section
introduces the concept of LOS goals in storm drainage utilities and proposes specific LOS goals for the
City.
Level-of-Service Goals within Storm Drainage Utilities 3.1
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
NPDES Permit is mandating that the City implement measurable LOS criteria.
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,
ratepayers, 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;
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communities should be willing to periodically revisit LOS goals to make sure that they are still
appropriate.
Comp Plan Policies and Levels of Service 3.2
This section reviews elements of the City’s current Comp Plan that apply to the 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 Policies Related to Storm Drainage
The City’s Comp Plan contains numerous goals, presented as policies, that relate to the operation and
management of storm drainage assets. The City policies below have been used in developing specific
LOS for this Drainage Plan. These policies are taken from the Comp Plan. The items named with “GP,”
“CF,” and “EN” prefixes appear in the General Approach, Capital Facilities and Environment chapters,
respectively.
GP-23 The City should continue its participation in the various State and Federal agencies and
organizations concerned with land use planning and development and the protection of
cultural resources and critical areas.
GP-28a Auburn’s character as a “family” community will be a priority consideration in the City’s land
use management decisions. This priority must be balanced, however, with the following:
a. City policy will address various related community needs. This includes nurturing and
managing the other roles necessary for maintaining a healthy community, recognizing the
importance of sustainability in the City and responding to regional needs. Such roles include
ensuring the expansion of employment opportunities, providing a full range of commercial,
retail and service opportunities, providing recreational and cultural opportunities, managing
traffic, encouraging energy and resource efficiency and maintaining a balance with the
natural environment.
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-42 The City’s storm drainage utility shall ensure that all private and public storm drainage
improvements are designed, constructed, operated, and maintained in accordance with the
Comprehensive Storm Drainage Plan and Comprehensive Plan. Drainage facilities serving
the larger community should be owned, operated, and maintained by the City’s storm
drainage utility. Drainage facilities serving individual properties or maintenance-intensive
drainage facilities designed to serve as a multifunctional private resource (e.g., private
parks, wetland mitigation) should be owned, operated, and maintained by the property
owner in accordance with a recorded maintenance agreement approved by the City.
CF-45 The City shall promote policies that seek to maintain the existing conveyance capacity of
natural drainage courses.
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CF-48 In selecting the preferred Comprehensive Storm 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 Storm 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.
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 degree to which the alternative preserves and enhances existing native vegetation
and existing drainage courses.
9. The alternative’s ability to reduce flood hazard impacts resulting from the 25-year design
storm event.
CF-50 The Storm Drainage Utility shall work with other jurisdictions and agencies to address
regional water quality issues.
CF-51 The City shall seek opportunities where feasible to reintroduce treated urban runoff back
into groundwater system as new and redevelopment occurs to minimize urbanization
impacts to the hydrology of natural river systems.
CF-XX
proposed
new
policy
The City shall seek best business practices for capital facilities through asset management.
Asset management is the manner by which to maintain assets in good working order to
minimize future costs of maintaining and replacing them, especially to avoid costly deferred
maintenance. Given that the utility is made up largely of physical assets that have the
greatest value and represent the greatest cost to operate and maintain, the City shall
address the business practice of asset management first.
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.
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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 in
accordance with the Western Washington Phase II Municipal Stormwater permit.
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, while
protecting public health and welfare.
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.
Table 3-1. LOS Goals
Item Policy description 2015 Drainage Plan LOS goal
Policy category: business practices
1
The City desires to employ recognized best business
practices that result in the efficient and cost-effective
operation of the utility. See proposed new policy CF-XX.
The City shall identify the key business functions within the utility (e.g., billing,
permitting, asset management, and planning) and develop supporting best
business practices for each. The utility will conduct a performance audit every 6
years in conjunction with its capital projects planning cycle to evaluate how well
best business practices are being implemented and how effective they are.
2
The City shall seek to employ the best practices for
asset management by systematically basing choices on
an understanding of asset performance, risks, and
costs in the long term. See proposed new policy CF-XX.
The City shall begin implementing the following best practices for all stormwater
facilities during the next planning period and report progress annually:
• Have knowledge about assets and costs (i.e., detailed inventories and
condition assessments)
• Maintain desired levels of service confirmed by customers
• Take a life-cycle approach to asset management planning
Implement the planned solutions to provide reliable, cost-effective service
Policy category: protection of public safety and property
3
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% (i.e., an average recurrence interval of 100 years).
4
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% (i.e., an average recurrence
interval of 25 years).
5
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).
6
The City shall seek to prevent erosion and landslides
related to construction, operation, and maintenance of
the publicly owned drainage system. See policies CF-
48 and EN-3.
No erosion or landslides resulting from public drainage infrastructure
construction, operation, or maintenance.
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Table 3-1. LOS Goals
Item Policy description 2015 Drainage Plan LOS goal
7
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, CF-
42, and EN-17.
The City will continue to 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. All activities will be documented within the City’s Cartegraph
computerized maintenance management system (CMMS).
Policy category: reliability of the storm drainage infrastructure
8
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 the 2008 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 Cartegraph CMMS.
9 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 all
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 all condition
assessment activities will be documented in the City’s Cartegraph CMMS.
10
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.
11
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 catch basins). The experience of
M&O staff should be incorporated into the criticality database (see item
8above). All inspection activities will be documented in the CMMS.
12
The City shall seek to maintain storm drainage
infrastructure to ensure proper function of drainage
facilities in accordance with Ecology requirements. See
policies CF-40, CF-42, and EN-15.
The City will develop a ditch maintenance program. The City will secure proper
permits as well as coordinate with other agencies for work in the associated
ROW. The ditch maintenance program will consist of inspecting and maintaining
all ditches within the permit cycle and then on an as-needed basis.
13
The City shall seek to manage stormwater runoff from
the public ROW with City-owned facilities located in the
public ROW or on City-owned property. The City shall
maintain or seek access to City-owned facilities for
necessary maintenance and operation. See policy EN-
17.
The City’s Storm Drainage Utility will be responsible for maintenance and
operation of the City’s drainage system. The City shall seek to have access to all
City-owned drainage infrastructure. The City shall seek to obtain easements or
relocate infrastructure as necessary to maintain access.
Policy category: protection of the environment
14
The City shall seek to comply with all federal and state
regulations applied to stormwater management
activities. See policy GP-23.
Meet all requirements of the Western Washington Phase II Municipal Stormwater
Permit with no enforcement actions of the CWA for violations as a result of City
stormwater operations.
15
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.
All 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.
16
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.
17
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.
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Table 3-1. LOS Goals
Item Policy description 2015 Drainage Plan LOS goal
18
The City shall seek to comply with all federal, state, and
local regulations to reduce runoff volumes and
pollutant loads associated with new development and
redevelopment. See policies CF-51 and EN-15.
The City will comply with the elements of the Western Washington Phase II
Municipal Stormwater Permit and will adopt or implement the Ecology manual or
equivalent for new development and redevelopment.
19
The City shall place emphasis on onsite approaches
such as LID as the first consideration for runoff and
pollutant load reduction for new development and
redevelopment. See policy EN-17A.
The City will identify feasibility criteria and provide guidance for the
implementation of LID drainage management measures for new development
and redevelopment (including City-owned properties).
20
The City shall seek to evaluate Storm Drainage Utility
activities to emphasize sustainability. See policy GP-
28a.
City staff will identify specific areas to measure sustainability by examining how
Storm Drainage Utility operations affect energy resources, natural resources,
and the community. City staff will benchmark practices and log changes over the
next planning period.
21
The City shall continue to participate in regional storm
drainage, water resources, and water quality planning
efforts. See policies CF-48, CF-50, 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. The City will participate
in the state’s water quality monitoring program.
22
The City shall comply with all federal, state, and local
regulations in the inspection of the City’s publicly
owned storm drainage infrastructure and privately
owned LID facilities. See policy CF-42.
For all new LID systems constructed after 2016, the City will develop authority
and an inspection frequency for stormwater facilities developed in compliance
with the NPDES Phase II Stormwater Permit. The City will develop an inspection
assessment database to monitor and schedule facility maintenance for all
publicly owned storm drainage infrastructure and privately owned LID facilities.
This database will provide maintenance information for the criticality database
in the City’s Cartegraph CMMS.
Policy category: Storm Drainage Utility financial performance
23
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, with a goal of 100%
of the cost of drainage service delivery recovered via Storm Drainage Utility fees.
Seek opportunities to provide public drainage benefits through grant funding
and/or development partnerships where applicable.
24
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 all 6-year CIP updates.
25 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 evaluate methods to reduce the risk of claims
and measure its progress at reducing the overall cost of claims.
26
The City shall seek to track elements of capital
improvement project 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 capital improvement project
implementation to create a baseline (e.g., schedule and costs) against which
future improvements can be evaluated.
Policy category: customer satisfaction
27
The City shall seek to evaluate and strive to maintain
customer satisfaction with Storm 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 Western Washington Phase II
Municipal Stormwater Permit requirements for public education and outreach.
28
The City shall seek to build, operate, and maintain
storm drainage 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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Chapter 4
Drainage System
Chapter 3 lays out clear LOS goals for the Storm Drainage Utility. The next step toward developing a
future work plan is to collect and organize information describing the current conditions of the storm
drainage system. This information provides the basis for investigations (Chapter 5) designed to evaluate
the Storm Drainage 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 Storm Drainage Utility service, drainage,
and surrounding areas. These figures are presented at the end of the chapter.
Natural Drainage 4.1
The City of Auburn encompasses approximately 30 square miles; the central portion of the city lies along
the bottom of a 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 30 miles of rivers and streams and more than 1,000 acres of floodplain area
associated with these water features. There are over 1,500 acres of wetlands, including forested/shrub
and freshwater emergent wetlands.
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 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, the Howard A. Hanson Dam was built on the Green River to control flooding in the valley.
From 1960 to 2007, the City of Auburn participated in Green River flood management activities as part
of the Green River Flood Control District. In 2007, the Green River Flood Control District was phased out
as flood control and management efforts for the Green River are now included in the King County Flood
Control District (KCFCD), which was established in 2007. These efforts are reflected in the 2006 King
County Flood Hazard Management Plan. The KCFCD goals and objectives include maintaining and
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repairing levees and revetments and acquiring at-risk floodplain properties. Auburn elected officials and
staff serve on advisory committees for the KCFCD such as the Green River System Wide Improvement
Framework (Green River SWIF). The goal of the Green River SWIF is to recommend and prioritize a set of
capital projects and programs for flood protection for the Lower Green River.
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 by 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 the 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 (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. It crosses under SR 167 several times as it
flows through the valley floor. Approximately 1 mile 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, channel straightening, degradation of water
quality, and aggradation from increased stormwater inflows with high sediment loads. In many areas the
stream is straight and shallow, and exhibits a lack of quality riparian habitat for Endangered Species Act
(ESA)-listed species such as Chinook salmon and bull trout (USACE, April 2009). Aggradation along Mill
Creek has also contributed to flooding and drainage problems in the city. The City’s drainage outfalls to
Mill Creek can become submerged, thereby reducing the hydraulic capacity of the system.
The USACE and the City have initiated a restoration project, called the Mill Creek 5K Reach Restoration
Project, for the reach of Mill Creek on the west side of SR 167 extending from Main Street to north of the
15th Street NW culvert. The project includes constructing a new creek channel and replacing the culvert
at 15th Street NW. In addition to improving fish passage and flow conveyance through the culvert, the
project will reduce flood elevations along Mill Creek.
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4.1.4 Drainage Areas
The city’s drainage can be described by dividing the city into six general sub-areas3 and their discharge
location (Figure 4-2):
• 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 that 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 North Central portion of the city lies along the valley floor and is located north of 27th Street SE.
This is part of the central and most developed area of the city. The topography in this area is so flat
that roadways and storm drainage infrastructure largely determine the receiving water to which
runoff is diverted. Runoff from this area is generally split between Mill Creek and the Green River.
• The South Central portion of the city also lies along the valley floor and is located south of 27th
Street SE. This area is also part of the most developed area of the city. The topography in this area is
so flat that roadways and storm drainage infrastructure largely determine the receiving water to
which runoff is directed. This area, plus the Boeing property drains to the White River.
The above-described areas can be divided into smaller drainage subbasins. For the 2002 Comprehensive
Drainage Plan (Tetra Tech, 2002) subbasins were delineated such that the entire Storm Drainage Utility
was covered, resulting in a total of 61 drainage subbasins covering approximately 34 square miles. Each
subbasin is identified by a series of one, two, or three letters (Figure 4-2).
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 (Western Regional
Climate Center [WRCC], 2014a). Mean annual precipitation in the Puget Sound lowlands varies from 32
inches (north Seattle) to approximately 47 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 (with missing data filled in from the nearby King County Lakeland
Hills gauge) from 1995 to 2014 was approximately 38 inches. This is very similar to 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 457473), has a mean annual precipitation of approximately 38
3 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 subbasin, 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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inches based on 74 years of recorded data (WRCC, 2014b). The Seattle-Tacoma Airport gauge is
located approximately 8 miles northwest of Auburn.
• Kent, Washington (NOAA Co-op Station 454169) has a mean annual precipitation of approximately
39 inches based on 57 years of recorded data (WRCC, 2014c). The Kent 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
4.1.6 Geology and Groundwater
Topography and geology in the Auburn region has been influenced largely 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
consist 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 Auburn’s 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 Resources 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
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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 is 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 is 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.
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 Lakeland Hills areas are
predominantly Group C soils, which have low infiltration rates and moderate to high runoff potential. The
Southeast area, Bowman Creek area, and valley area located generally between SR 18 and the White
River have Group A soils, which are characterized by high infiltration rates and low runoff potential. See
the NRCS maps (http://www.nrcs.usda.gov/) for mapped soils within the city.
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 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 by 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. The Washington State
Office of Financial Management indicates that Auburn’s population in 2014 was approximately 74,600
(approximately 65,300 in King County and 9,300 in Pierce County).
4.1.8.2 Future Growth
The City’s goals, objectives, and policies for growth and development are described in detail in the 2015
Comp Plan. These goals, objectives, and policies are applied to different areas of the city through land
use designations (see Figure 4-4). 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.
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4.1.8.3 Development Regulations and Drainage Design Standards
The City implements state and federal stormwater regulations through the stormwater code, the Auburn
SWMM, and related stormwater management programs and policies. City stormwater regulations
contain specific requirements for managing stormwater quality and quantity in areas subject to new
development and redevelopment. For example, the SWMM provides guidance for implementing LID
measures that are designed both to improve water quality and to control peak flows and durations of
runoff. The City is in the process of updating its local development regulations and drainage standards in
accordance with updated NPDES Permit requirements.
City 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).
FEMA established flood hazard zones from a Flood Insurance Study (FIS) for King County conducted in
2013, 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. Updates to the flood hazard zones are
continually being made at local levels (King County and Pierce County) and represented in Preliminary
FIRMs or Letters of Map Revision (LOMR). Preliminary FIRMs for all of King County were reissued on
February 1, 2013. The most recent flood hazard mapping for Pierce County is presented in the County’s
“Rivers Flood Hazard Management Plan” adopted in 2013 and also in LOMR files located on the FEMA
Map Service Center Web page (Pierce County, 2013). 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 5301380213C
53033C1235K 53033C1254K 53033C1266K 5301380375C
53033C1242K 53033C1261K 53033C1267K 5301380220C
53033C1251K 53033C1262K 53033C1268K 5301380351C
53033C1252K 53033C1263K 53033C1269K
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Stormwater Drainage Infrastructure 4.2
As part of the development of the 2009 Drainage Plan, the City embarked on a substantial effort to
update its inventory of drainage system infrastructure owned or operated by the Storm Drainage Utility.
Since that plan, the City has continued to update its inventory through dedicated field staff conducting
surveys. This effort will continue until field surveys have been completed citywide. A comprehensive
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 repair and replacement (R&R)
activities
• Support the City’s M&O activities through the computerized maintenance management system
(CMMS)
Table 4-3 provides a summary of stormwater infrastructure inventory.
Table 4-3. Stormwater Drainage Infrastructure Summary
Infrastructure element GIS data type GIS feature class name Quantitya Unit
Pipes, all sizes Polyline Storm pipes 1,108,000 Linear feet
Pipes, all sizes (excluding force mains) Polyline Storm pipes 11,500 Count
6–10 in. diameter Polyline Storm pipes 2,300 Count
162,300 Linear feet
12–15 in. diameter Polyline Storm pipes 6,400 Count
547,500 Linear feet
16–18 in. diameter Polyline Storm pipes 1,100 Count
129,300 Linear feet
21–24 in. diameter Polyline Storm pipes 700 Count
96,900 Linear feet
27–36 in. diameter Polyline Storm pipes 400 Count
69,500 Linear feet
42–48 in. diameter Polyline Storm pipes 100 Count
32,700 Linear feet
54–72 in. diameter Polyline Storm pipes 10 Count
1,600 Linear feet
Force mains Polyline Storm pipes 23 Count
2,500 Linear feet
Open channels Polyline Storm channels 217,100 Linear feet
Culverts Polyline Storm culverts 38,400 Linear feet
Manholes Point Storm manholes 2,330 Count
Catch basins Point Storm catch basins 8,880 Count
Weirs Point Storm auxiliary equipment 1 Count
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Table 4-3. Stormwater Drainage Infrastructure Summary
Infrastructure element GIS data type GIS feature class name Quantitya Unit
Orifices Point
Storm manholes or storm
catch basin data,
where attribute flow control = yes
203 Count
Outfalls Point Storm outfalls 127 Count
Detention ponds Point Detention sites 139 Count
Infiltration ponds Point Detention sites 12 Count
Vaults Point Vault 17 Count
Pump stations Point Storm pumps 7 Count
a. Quantities are based on current inventory and 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 4-5 shows an overview of the city’s stormwater
drainage infrastructure.
Critical Facilities 4.3
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 ROW 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 3). Eleven 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 8–11). 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, repair history
of the asset, condition of the asset, and financial consequences of a failure. The consequences of a
system failure impacting a hospital or school are considered more serious than one affecting a residence
or unoccupied property, and are thus assigned as critical assets. The City has identified 11 city facilities
(Table 4-4) and seven stormwater pump stations (Table 4-5) as critical assets. 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 8). The locations of these critical facilities are shown
in Figure 4-6.
Table 4-4. Critical City Facilities
Facility Address
City Hall 25 W Main Street
City Hall Annex 1 E Main Street
Justice Center 340 E Main Street
Maintenance and Operation Facility 1305 C Street SW
Regional Hospital 201 N Division Street
Senior Center 808 9th Street SE
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Table 4-4. Critical City Facilities
Facility Address
Valley Regional Fire Authority (VRFA) Station 31 1101 D Street NE
VRFA Station 32 1951 R Street SE
VRFA Station 33 500 182nd Avenue E
VRFA Station 34 31290 124th Avenue SE
VRFA Station 35 2905 C Street SW
Table 4-5. Critical Stormwater Facilities
Storm drainage facility Year
constructed Address
A Street Pump Station 1973 404 A Street SE
Auburn Way S Pump Station 1994 405 Auburn Way S
Brannan Park Pump Station 2001 1302 30th Street NE
Emerald Park Pump Station 1999 499 42nd Street NE
M Street Pump Station 2014 410 M Street SE
West Main Street Pump Station 2008 1410 W Main Street
White River Pump Station 2012 4640 A Street SE
Water Quality 4.4
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 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 (Appendix A of this plan) describes water bodies that have been
assessed as impaired and have additional requirements based on established TMDLs. A fecal coliform
TMDL for the Puyallup River watershed is included in the current NPDES Permit. As part of the TMDL, the
City is required to conduct wet weather sampling of discharges to the White River at Auburn Riverside
High School. Details of the required activities are included in Appendix 2 to the NPDES Permit.
The Green River has a TMDL for temperature that was approved by EPA in 2011. The TMDL report
indicated that implementation will depend on the support and participation of Auburn; however, the
water quality improvement plan has not been developed yet and the TMDL is not in Appendix 2 of the
NPDES Permit (Ecology, 2011).
The Green River is also being evaluated for a potential TMDL for dissolved oxygen, and Ecology is
currently evaluating Mill Creek, White River and Little Soosette Creek within the city. Mill Creek is being
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examined for potential TMDLs for temperature, fecal coliform, dissolved oxygen, and copper, and the
lower White River currently is under evaluation for TMDLs for pH and temperature. Soos Creek
watershed, which is partially in the city and includes the tributary Little Soosette Creek, has TMDLs under
development for aquatic habitat, dissolved oxygen, temperature, and fecal coliform. One or more new
TMDLs could be included in a future NPDES Permit.
4.4.2 Regulatory Compliance
The City has a well-developed MS4 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 stormwater management BMPs in its municipal activities. BMPs include 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.
The current NPDES Permit includes provisions for monitoring and assessment of water quality.
Permittees have the option of paying annual fees to participate in statewide monitoring programs, or
developing individual monitoring programs to meet the requirement. The City notified Ecology in 2013
that it intends to participate in the statewide monitoring programs. Fees totaling $47,710 are due
annually, beginning in August 2014.
The City is in full compliance with its NPDES Permit, with programs, codes, processes, and procedures
that meet all of the NPDES Permit requirements currently in effect. The City’s SWMP Plan contains a
summary of the NPDES Permit requirements and descriptions of the City’s current and planned activities
for NPDES Permit compliance.
However, the City will need to make several changes to comply with updated requirements of the NPDES
Permit that phase in during the permit term. The City is conducting a process to identify and implement
needed updates to codes, standards, and programs by the relevant due dates. As part of the process,
the City developed a Compliance Work Plan to outline and guide compliance activities over the current
permit term. A copy of the Compliance Work Plan is included as Appendix B.
A schedule of relevant due dates to comply with updated NPDES Permit requirements is provided in
Section 8.3.
Existing Drainage Problems 4.5
Members of the City staff working within the Storm Drainage Utility are experienced and familiar with the
condition of the drainage system. Existing drainage problems have been observed by the staff and are
known to cause frequent flooding of roadways. The most apparent problems were identified for analysis
(see Hydraulic Evaluation, Section 5.1). Additionally, a severe storm event occurring in November 2007
caused substantial flooding in several locations that were identified during the development of the 2009
Drainage Plan. Many high-priority capital improvement projects were implemented to address these
problems. Capital improvement projects, which were developed for some lower-priority locations, have
yet to be implemented. For this planning effort, unimplemented capital improvement projects were
revised based on current conditions and available information. Existing drainage problems are described
in Table 4-5 and locations are mapped in Figure 4-7. Capital improvement projects developed to address
these problems are described in Chapter 7.
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Table 4-6. Existing Drainage Problems
No. Priority Location Description Approximate frequency
or last noted occurrence
P1 1 West Main Street dead
end near SR 167
The dead-end portion of Old West Main Street near SR 167 has a history of
observed flooding. The City installed a temporary pump station to dewater
the gravity pipe, flowing on the south side of Old West Main Street, in the
effort to protect local businesses from flooding. Since its installation in
2008, the pump station has eliminated flooding at the observed location.
The pump station, however, does not meet the City’s LOS guidelines
regarding pump redundancy, and may be insufficient to convey the 25-year
flow rate.
The City’s gravity pipe on the north side of Old West Main Street
experiences flooding, at one catch basin, approximately once per year.
Portions of this gravity pipe are full and water has been observed at catch
basin rims during summer months.
The pump station and gravity pipe discharge to a Washington State
Department of Transportation (WSDOT) ditch along the east side of SR
167. WSDOT has recently cleaned this ditch segment, and the impacts of
this maintenance work are still being determined.
Catch basin flooding once
per year and system
surcharging
P2 1 37th and I Streets NW
Recurring flooding in the vicinity of 37th Street NW and I Street NW causes
several nuisance problems including slow or impeded traffic on 37th Street
NW, driveway damage and/or impeded access to the nearby power
substation, and impeded pedestrian and bicycle access to the Interurban
Trail south of 37th Street NW (east of the substation).
A couple times a year, after
heavy rain prolonged wet
periods following storm
events
P3 1 Hillsides throughout the
city
The existing drainage system includes pipes that discharge over hillsides.
While a preliminary inventory and mapping of locations has been
completed, field-locating and detailed inspection is warranted to define
deficiencies.
Periodic
P4A 2
East of I Street NE
between 32nd Street NE
and 35th Street NE
The residential development east of I Street NE between 32nd Street NE
and 35th Street NE discharges flows into a City-owned infiltration area. The
infiltration area commonly experiences prolonged periods of standing
water due to high groundwater from extended high flows in the Green River,
which is adjacent to the infiltration area. The drainage system on I Street
NE currently lacks infrastructure to collect and convey stormwater away
from the infiltration area as well as residential roadways and parking areas.
Ponding occurs within the parking of the developments and presents a
nuisance and potential hazard to local residents.
Once every few years
P4B 3
C Street NE between
30th Street NE and 37th
Street NE
The December 3, 2007, storm (approximately a 50-year storm) produced
extensive flooding along C Street NE northward toward 37th Street NE,
which required sandbagging to protect local businesses. Deposition of
sediment within Mill Creek has raised the water levels within the creek and
diminished the capacity of the gravity system in C Street NE and
downstream in 37th Street NE. In addition to the influence of Mill Creek,
modeling efforts demonstrate that the system’s capacity is limited by low
pipe gradient and shallow inverts and that flooding would continue even
with sediment removal within Mill Creek.
December 2007
P5 1 West Hills
Flooding has been reported along the S 330th Street roadway. Surface
water from the ROW is conveyed through a ditch and set of pipes located on
private properties. The portion on private property had previously been
conveyed in a ditch. In an attempt to reclaim the front yard, a previous
property owner filled the ditch with two parallel pipes.
A City-owned pipe daylights to the backyard of a residential parcel and
discharges runoff onto the northern adjacent property located on S 312th
Street.
Once in last 5 years
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Table 4-6. Existing Drainage Problems
No. Priority Location Description Approximate frequency
or last noted occurrence
P6 2 North Airport area
The inlet and outlet of Airport Pond I do not allow the pond to operate as
designed; the pond fills from its outlet when the storm line in 30th Street
NE surcharges. In the north hangar area immediately east of Airport Pond I,
surcharging flows from the storm line in 30th Street NE backwater to the
airport’s 30-inch-diameter storm drain and causes flooding to the north
and west of the most northerly hangar.
December 2007
P7 2 D Street SE at 25th
Street
The western dead-end portion of 25th Street SE has a history of observed
flooding. An existing dry well has inadequate infiltration. The dry well floods
after heavy rain, several times a year. Floodwater fills the adjacent section
of 25th Street SE to the curb. Numerous dry wells also do not meet
discharge standards.
Floods after heavy
prolonged rain
P8 3 23rd Street SE
A new 12-inch-diameter stormwater gravity drain was installed along K
Street SE, south of 23rd Street SE, in 2014 to address localized flooding.
This piping increased the tributary area to the 8-inch-diameter gravity drain
along 23rd Street SE. Modeling results indicate that the existing 8-inch-
diameter gravity drain along 23rd Street SE does not meet the LOS.
None reported; potential
flooding simulated through
modeling
In addition to the problem locations listed in Table 4-6, the City identified two potential problem areas
described below.
Riverwalk Drive SE and Howard Road. Roadside ditches along the north and east side of Howard Road,
between Riverwalk Drive SE and R Street SE overtop and flood portions of Howard Road and the mobile
home park along the south side of the road. The Muckleshoot Indian Tribe has development plans for
the property between Howard Road and Auburn Way S. As part of the development, storm drainage
infiltration areas will be expanded northward of the existing facilities in the vicinity of the City’s water
treatment facility. Proposed facilities will include an overflow to the City’s storm drainage system, which
flows to the 21st Street Pond. The proposed modifications may address the observed flooding.
2nd and G Streets SE. The 2009 Drainage Plan described a problem at this location as roadway flooding
during large rain events due to manhole surcharging in the intersection. The manhole is located in a
local low point, and water encroaches on private property. In addition, a King County regional sewer line
crosses the storm drainage line at this manhole reducing conveyance capacity at this location. A project
to address this problem was included in the 2009 Drainage Plan, but has not been implemented.
Flooding has not been reported at this location since the development of the 2009 Drainage Plan. With
the implementation of the project Auburn Way S Flooding, Phase 1 in 2012 and planned construction of
Auburn Way S Flooding, Phase 2 in 2015/2016, the tributary area to this reported problem location will
be reduced. The lack of recent reported flooding and the reduced tributary area may indicate a project is
not warranted for this location.
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W
4TH AVE SW
14
8
T
H
A
V
E
E
7TH ST SE
13
7
T
H
A
V
E
E
26
T
H
S
T
E
13
6
T
H
A
V
E
E
SE 310TH ST
S 3RD AVE
TH
O
R
T
O
N
A
V
E
S
W
2
0
0
T
H
A
V
E
E
17TH
S
T
E
RIVE
R
D
R
BOUNDARY BLVD
LEA HIL
L
R
D
S
E
32ND ST E
11
8
T
H
A
V
E
S
E
58
T
H
A
V
E
S
10
4
T
H
A
V
E
S
E
S 372ND ST
J
S
T
N
E
ROY RD SW
4TH ST NE
PA
C
I
F
I
C
A
V
E
S
11
0
T
H
A
V
E
S
E
14TH ST NE
SE 281ST ST
16
0
T
H
A
V
E
S
E
12
6
T
H
A
V
E
E
5TH ST SE
72
N
D
A
V
E
S
56
T
H
P
L
S
25TH ST E
BR
I
D
G
E
T
A
V
E
S
E
57
T
H
A
V
E
S
S 328TH ST
DO
G
W
O
O
D
S
T
S
E
SE 376TH ST
2ND AVE SW
8TH ST SE
S 279TH ST
L
S
T
S
E
T
S
T
S
E
F
S
T
S
E
FR
O
N
T
A
G
E
R
D
C
O
T
T
A
G
E
R
D
E
FO
S
T
E
R
A
V
E
S
E
52
N
D
A
V
E
S
SE 274TH ST
16
6
T
H
A
V
E
E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
49TH ST NE
S 362ND ST
I
S
T
N
W
32ND PL NE
54
T
H
A
V
E
S
A
S
T
S
W
57
T
H
P
L
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
47TH
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
S
T
S
E
R S
T
N
W
27TH ST E
15TH ST E
28TH ST E
MI
L
I
T
A
R
Y
R
D
S
13TH ST E
K
S
T
S
E
OL
I
V
E
A
V
E
S
E
10TH ST E
31ST ST NE
SE 323RD PL
54
T
H
P
L
S
B
S
T
S
E
WY
M
A
N
D
R
26TH ST SE
S 336TH ST
ST
P
A
U
L
B
L
V
D
S 340TH ST
C
S
T
S
E
B S
T
N
E
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
V
S
T
N
W
2ND ST SE
23RD ST SE
4TH AVE S
3RD ST SE
QU
I
N
C
Y
A
V
E
S
E
21ST ST NE
1
5
6
T
H
A
V
E
E
14
0
T
H
A
V
E
E
HE
M
L
O
C
K
S
T
S
E
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
S
T
N
E
LU
N
D
R
D
S
W
S 324TH ST
PI
K
E
S
T
N
W
21ST ST E
31ST ST E
42ND ST NW
6TH AVE SW
11
9
T
H
A
V
E
E
SE 286TH ST
9TH ST SE
55
T
H
P
L
S
SE 276TH PL
65
T
H
A
V
E
S
SE 295TH PL
G
S
T
N
E
27TH ST SE5TH AVE N
SK
I
N
N
E
R
R
D
12
8
T
H
A
V
E
E
S 354TH ST
S 344TH ST
SE 364TH ST
SE 290TH ST
10TH ST SE
D
S
T
S
W
SE 280TH ST
2
1
1
T
H
A
V
E
E
NA
T
H
A
N
A
V
E
S
E
HI
C
R
E
S
T
D
R
B PL NW
SE 294TH ST
72ND ST SE
S 285TH ST
6TH ST NW
14
6
T
H
A
V
E
S
E
SE 293RD ST
3RD ST NW
12
6
T
H
A
V
E
S
E
I
S
A
A
C
A
V
E
S
E
S 312TH ST
EL
M
S
T
S
E
CLAY ST
S 370TH ST
52
N
D
P
L
S
7TH ST E
19TH DR NE
SE 307TH PL
51ST
S
T
S
E
10TH AVE N
S 364TH ST
14
0
T
H
A
V
E
S
E
28TH ST SE
15TH ST SE
13
3
R
D
A
V
E
S
E
10
8
T
H
A
V
E
S
E
73RD ST SE
SE 295TH ST
26TH ST NE
S 366TH ST
SE 3
8
0
T
H
P
L
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
AL
D
E
R
L
N
S
11
7
T
H
A
V
E
S
E
U
S
T
S
E
19TH ST SE
6TH ST SE
11
0
T
H
P
L
S
E
A ST E
15
6
T
H
A
V
E
S
E
21ST ST SE
R PL NE
11
7
T
H
A
V
E
E
33RD ST SE
7TH ST
5TH ST NE
53
R
D
A
V
E
S
HE
A
T
H
E
R
A
V
E
S
E
F
S
T
N
E
11
2
T
H
P
L
S
E
51
S
T
P
L
S
SE 292ND ST
D PL SE
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
63
R
D
P
L
S
2ND CT NW
1ST ST NE
R
S
T
N
E
12
9
T
H
P
L
S
E
O
C
T
S
E
S 342ND ST
26TH ST NW
SE 321ST PL
11
4
T
H
P
L
S
E
8TH ST NE
51
S
T
A
V
E
S
9TH ST E
55T
H
P
L
S
SE 288TH ST
SR
1
6
7
SE 272ND ST
51
S
T
A
V
E
S
11
0
T
H
A
V
E
S
E
C S
T
N
W
SE 282ND ST
S 277TH ST
55
T
H
A
V
E
S
SE 296TH ST
53
R
D
A
V
E
S
SE 282ND ST
11
8
T
H
A
V
E
S
E
8TH ST E
SR 1
8
SE 272ND ST
SR
1
6
7
M
S
T
N
W
1ST AVE N
SR
1
6
7
14
2
N
D
A
V
E
E
S 277TH ST
SE 274TH ST
56
T
H
A
V
E
S
SR
1
6
7
23RD ST SE
H
S
T
N
E
SR
1
6
7
8TH ST E
16TH ST E
SR
1
6
7
10
8
T
H
A
V
E
S
E
SR
1
6
7
12TH ST E
M
S
T
N
E
10
4
T
H
A
V
E
S
E
2ND ST E
SE 301ST ST
SR
1
6
7
SR 18
21ST ST E
R
S
T
N
W
32ND ST E
14
4
T
H
A
V
E
S
E
12
4
T
H
A
V
E
S
E
32ND ST E
14
8
T
H
A
V
E
S
E
D
S
T
S
E
24TH ST E
SR 1
8
2ND ST SE
17TH ST SE
SE 368TH PL
20
0
T
H
A
V
E
E
51ST
S
T
S
E
R
S
T
N
W
COMPREHENSIVE STORM DRAINAGE PLAN
1 inch = 4,000 feet
April 2015
LEGEND
Roadway
Watercourse
Water Body
Wetland
Auburn City Boundary
P:
\
A
u
b
u
r
n
\
1
4
5
2
9
5
A
u
b
u
r
n
S
t
o
r
m
w
a
t
e
r
C
o
m
p
P
l
a
n
\
G
I
S
\
M
X
D
\
P
r
e
l
i
m
i
n
a
r
y
D
r
a
f
t
P
l
a
n
\
A
u
b
u
r
n
S
t
o
r
m
_
F
i
g
4
-
1
(
n
a
t
d
r
a
i
n
)
.
m
x
d
0 4,000 8,000
Feet
Figure 4-1Natural Drainage Features of the City of Auburn¯
L a k eT a p p s
Bi 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
ill
Creek
CreekMill
G
r
e
e
n
R
i
v
e
r
White
G
r
e
e
n
River
Soosette
Creek
River
Whit
e
Bow m an C
re
e
k
W
h
i
t
e
River
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
White
Lea Hill
Southern
North Central
West Hill
Southeast
South Central
COMPREHENSIVE STORM DRAINAGE PLAN
1 inch = 4,000 feet
LEGEND
Roadway
Watercourse
Water Body
Wetland
Drainage Subarea
Auburn City Boundary
Major receiving water
Green River
Mill Creek
Mullen Slough
Soosette and Big Soos Creeks
White River
Outfalls
Green River
Mill Creek
White River
Other Stream
Wetland
P:
\
A
u
b
u
r
n
\
1
4
5
2
9
5
A
u
b
u
r
n
S
t
o
r
m
w
a
t
e
r
C
o
m
p
P
l
a
n
\
G
I
S
\
M
X
D
\
P
r
e
l
i
m
i
n
a
r
y
D
r
a
f
t
P
l
a
n
\
A
u
b
u
r
n
S
t
o
r
m
_
F
i
g
4
-
2
(
s
u
b
b
a
s
i
n
s
)
.
m
x
d
0 4,000 8,000
Feet
Figure 4-2Drainage Subareas for the City of Auburn Storm Drainage Utility¯April 2015
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
Mill
Creek
CreekMill
G
r
e
e
n
R
i
v
e
r
G
r
e
e
n
River
White
G
r
e
e
n
River
Soosette
Creek
River
W
hit
e
Bow man
C
re
e
k
W
h
i
t
e
River
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
White
S
R
1
6
7
SR 1
8
A
S
T
S
E
C
S
T
S
W
A
U
B
U
R
N
W
A
Y
S
B
S
T
N
W
I
S
T
N
E
AU
B
U
R
N
W
A
Y
N
R
S
T
S
E
13
2
N
D
A
V
E
S
E
WE
S
T
V
A
L
L
E
Y
H
W
Y
N
W
M
S
T
S
E
8TH ST E
E MAIN ST
24TH ST E
12
4
T
H
A
V
E
S
E
EA
S
T
V
A
L
L
E
Y
H
W
Y
S
E
JOVITA BLVD
12
2
N
D
A
V
E
E
C
S
T
N
W
BU
T
T
E
A
V
E
S 384TH ST
11
0
T
H
A
V
E
E
15TH ST SW
SE 288TH ST
2ND ST E
C
S
T
N
E
SE 312TH ST
S 277TH ST
W MAIN ST
15TH ST NW
19
8
T
H
A
V
E
E
53RD ST SE
9TH ST
E
29TH ST SE
GREEN VALLEY RD
1
7
9
T
H
A
V
E
SE 320TH ST
11
4
T
H
A
V
E
E
11
6
T
H
A
V
E
S
E
EDWARDS RD E
LAKE TAPPS PKWY SE
41ST ST SE
WE
S
T
V
A
L
L
E
Y
H
W
Y
S
W
STUCK
R
I
V
E
R
D
R
16TH ST E
K
E
R
S
E
Y
W
A
Y
S
E
14
7
T
H
A
V
E
S
E
4TH ST E
18TH ST E
M
S
T
N
E
12TH ST E
SE 304TH ST
1
9
0
T
H
A
V
E
E
11
2
T
H
A
V
E
E
3RD AVE SE
ELLINGSON RD SW
37TH ST SE
PE
R
I
M
E
T
E
R
R
D
SE 272ND ST
4
6
T
H
P
L
S
8TH ST NE
18
2
N
D
A
V
E
E
37TH ST NW
AC
A
D
E
M
Y
D
R
S
E
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
ORA
V
E
T
Z
R
D
S
E
VA
L
E
N
T
I
N
E
A
V
E
S
E
C
U
T
O
F
F
51
S
T
A
V
E
S
SE 282ND ST
14
4
T
H
A
V
E
S
E
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
55
T
H
A
V
E
S
1
8
5
T
H
A
V
E
E
21
4
T
H
A
V
E
E
D
S
T
S
E
1ST AVE SE
TA
C
O
M
A
B
L
V
D
D
S
T
N
W
A
S
T
N
E
4TH ST SE
CE
L
E
R
Y
A
V
E
30TH ST NE
10
8
T
H
A
V
E
EA
S
T
B
L
V
D
(
B
O
E
I
N
G
)
11
2
T
H
A
V
E
S
E
SE 316TH ST
14
8
T
H
A
V
E
S
E
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
EM
E
R
A
L
D
D
O
W
N
S
D
R
N
W
D
S
T
N
E
M
S
T
N
W
O
S
T
N
E
S
E
3
6
8
T
H
P
L
W
S
T
N
W
1
6
9
T
H
A
V
E
E
S 287TH ST
3RD AVE S
5TH AVE SW
E
S
T
N
E
37TH ST NE
14
2
N
D
A
V
E
E
S 316TH ST
H
A
R
V
E
Y
R
D
S
C
E
N
I
C
D
R
S
E
H
S
T
N
W
M
A
I
N
S
T
S 292ND ST
WE
S
T
B
L
V
D
(
B
O
E
I
N
G
)
44TH ST NW
3RD AVE SW
11
8
T
H
A
V
E
E
10TH ST NE
CL
A
Y
S
T
N
W
4TH AVE SW
14
8
T
H
A
V
E
E
7TH ST SE
13
7
T
H
A
V
E
E
26
T
H
S
T
E
13
6
T
H
A
V
E
E
SE 310TH ST
S 3RD AVE
TH
O
R
T
O
N
A
V
E
S
W
2
0
0
T
H
A
V
E
E
RIVE
R
D
R
BOUNDARY BLVD
LEA HIL
L
R
D
S
E
32ND ST E
11
8
T
H
A
V
E
S
E
58
T
H
A
V
E
S
AL
G
O
N
A
B
L
V
D
N
10
4
T
H
A
V
E
S
E
S 372ND ST
J
S
T
N
E
ROY RD SW
4TH ST NE
PA
C
I
F
I
C
A
V
E
S
11
0
T
H
A
V
E
S
E
14TH ST NE
D
R
I
V
E
W
A
Y
SE 281ST ST
12
6
T
H
A
V
E
E
5TH ST SE
72
N
D
A
V
E
S
56
T
H
P
L
S
25TH ST E
BR
I
D
G
E
T
A
V
E
S
E
57
T
H
A
V
E
S
S 328TH ST
DO
G
W
O
O
D
S
T
S
E
2ND AVE SW
8TH ST SE
S 279TH ST
L
S
T
S
E
T
S
T
S
E
F
S
T
S
E
FR
O
N
T
A
G
E
R
D
C
O
T
T
A
G
E
R
D
E
FO
S
T
E
R
A
V
E
S
E
52
N
D
A
V
E
S
SE 274TH ST
1ST ST E
16
6
T
H
A
V
E
E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
49TH ST NE
S 362ND ST
NO
R
M
A
N
A
V
E
S
E
I
S
T
N
W
32ND PL NE
54
T
H
A
V
E
S
A
S
T
S
W
57
T
H
P
L
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
47TH
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
S
T
S
E
R S
T
N
W
27TH ST E
15TH ST E
28TH ST E
MI
L
I
T
A
R
Y
R
D
S
13TH ST E
K
S
T
S
E
OL
I
V
E
A
V
E
S
E
10TH ST E
10
8
T
H
A
V
E
E
31ST ST NE
SE 323RD PL
54
T
H
P
L
S
B
S
T
S
E
WY
M
A
N
D
R
26TH ST SE
S 336TH ST
ST
P
A
U
L
B
L
V
D
S 340TH ST
C
S
T
S
E
B S
T
N
E
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
S
T
N
W
2ND ST SE
23RD ST SE
4TH AVE S
3RD ST SE
QU
I
N
C
Y
A
V
E
S
E
29TH ST NW
21ST ST NE
1
5
6
T
H
A
V
E
E
HE
M
L
O
C
K
S
T
S
E
1
8
4
T
H
C
T
E
5
6
T
H
A
V
E
S
10
6
T
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
S
T
N
E
LU
N
D
R
D
S
W
S 324TH ST
PI
K
E
S
T
N
W
21ST ST E
31ST ST E
42ND ST NW
6TH AVE SW
17TH
S
T
E
11
9
T
H
A
V
E
E
SE 286TH ST
9TH ST SE
55T
H
P
L
S
SE 276TH PL
65
T
H
A
V
E
S
SE 295TH PL
G
S
T
N
E
27TH ST SE5TH AVE N
SK
I
N
N
E
R
R
D
1
0
2
N
D
A
V
E
S
E
12
8
T
H
A
V
E
E
S 354TH ST
S 344TH ST
SE 364TH ST
SE 290TH ST
10TH ST SE
D
S
T
S
W
SE 280TH ST
2
1
1
T
H
A
V
E
E
NA
T
H
A
N
A
V
E
S
E
V
S
T
S
E
HI
C
R
E
S
T
D
R
B PL NW
SE 294TH ST
S 285TH ST
6TH ST NW
14
6
T
H
A
V
E
S
E
SE 293RD ST
PE
A
R
L
A
V
E
S
E
3RD ST NW
12
6
T
H
A
V
E
S
E
I
S
A
A
C
A
V
E
S
E
S 312TH ST
EL
M
S
T
S
E
CLAY ST
S 370TH ST
20TH ST E
52
N
D
P
L
S
7TH ST E
19TH DR NE
SE 307TH PL
51ST
S
T
S
E
10TH AVE N
S 364TH ST
14
0
T
H
A
V
E
S
E
28TH ST SE
72ND ST SE
15TH ST SE
13
3
R
D
A
V
E
S
E
10
8
T
H
A
V
E
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
AL
D
E
R
L
N
S
11
7
T
H
A
V
E
S
E
U
S
T
S
E
19TH ST SE
6TH ST SE
11
0
T
H
P
L
S
E
A ST E
15
6
T
H
A
V
E
S
E
21ST ST SE
R PL NE
11
7
T
H
A
V
E
E
10
5
T
H
A
V
E
S
E
7TH ST
5TH ST NE
53
R
D
A
V
E
S
HE
A
T
H
E
R
A
V
E
S
E
F
S
T
N
E
11
2
T
H
P
L
S
E
51
S
T
P
L
S
SE 292ND ST
D PL SE
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
12
3
R
D
A
V
E
E
63
R
D
P
L
S
TH
O
R
T
O
N
P
L
S
W
2ND CT NW
1ST ST NE
12
9
T
H
P
L
S
E
6TH ST NE
3RD ST NE
O
C
T
S
E
S 342ND ST
10
5
T
H
A
V
E
E
26TH ST NW
SE 321ST PL
11
4
T
H
P
L
S
E
26TH ST NE
55
T
H
A
V
E
S
SE 301ST ST
54
T
H
A
V
E
S
56
T
H
A
V
E
S
51
S
T
A
V
E
S
M
S
T
N
E
14
4
T
H
A
V
E
S
E
SE 292ND ST
32ND ST E
SR 18
24TH ST E
21ST ST E
S 277TH ST
11
0
T
H
A
V
E
S
E
SE 282ND ST
SR
1
6
7
20
0
T
H
A
V
E
E
SE 272ND ST
SR 18
DRIVEWAY
2ND ST SE
R
S
T
N
W
SE 274TH ST
8TH ST E
10
8
T
H
A
V
E
S
E
32ND ST E
SE 288TH ST
9TH ST E
51
S
T
A
V
E
S
23RD ST SE
16TH ST E
SR
1
6
7
12TH ST E
SR
1
6
7
12
4
T
H
A
V
E
S
E
SR
1
6
7
DRIV
E
W
A
Y
8TH ST NE
SE 272ND ST
14
8
T
H
A
V
E
S
E
SE 282ND ST
SR
1
6
7
V
S
T
S
E
17TH ST E
8TH ST E
SR 1
8
SR
1
6
7
SR
1
6
7
SE 296TH ST
H
S
T
N
E
R
S
T
N
W
13TH ST E
SR
1
6
7
51ST
S
T
S
E
SR
1
6
7
10
4
T
H
A
V
E
S
E
1ST AVE N
SE 284TH ST
D
R
I
V
E
W
A
Y
SR 1
8
D
R
I
V
E
W
A
Y
S 277TH ST
10
8
T
H
A
V
E
E
D
S
T
S
E
SE 304TH S
T
10
6
T
H
A
V
E
E
17TH ST SE
55T
H
P
L
S
COMPREHENSIVE STORM DRAINAGE PLAN
1 inch = 4,000 feet
April 2015
LEGEND
Roadway
Watercourse
Water Body
Wetland
Subbasins
Auburn City Boundary
Surficial Geology
Qa
Qc
Qf
Qga
Qgd
Qgl
Qgo
Qgp
Qgp(s)
Qgp(st)
Qgpc
Qgt
Qls
Qp
Qvl(o)
P:
\
A
u
b
u
r
n
\
1
4
5
2
9
5
A
u
b
u
r
n
S
t
o
r
m
w
a
t
e
r
C
o
m
p
P
l
a
n
\
G
I
S
\
M
X
D
\
P
r
e
l
i
m
i
n
a
r
y
D
r
a
f
t
P
l
a
n
\
A
u
b
u
r
n
S
t
o
r
m
_
F
i
g
4
-
3
(
g
e
o
)
.
m
x
d
0 4,000 8,000
Feet
Figure 4-3Surface Geology inthe Vicinity of theCity of Auburn
Geologic UnitLithologyQaAlluvium
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 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
ill
Creek
CreekMill
G
r
e
e
n
R
i
v
e
r
G
r
e
e
n
River
White
G
r
e
e
n
River
Soosette
Creek
River
W
hit
e
Bow m an
C
re
e
k
W
h
i
t
e
River
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
White
S
R
1
6
7
A
S
T
S
E
C
S
T
S
W
A
U
B
U
R
N
W
A
Y
S
B
S
T
N
W
I
S
T
N
E
AU
B
U
R
N
W
A
Y
N
SR 1
8
R
S
T
S
E
13
2
N
D
A
V
E
S
E
WE
S
T
V
A
L
L
E
Y
H
W
Y
N
W
M
S
T
S
E
8TH ST E
E MAIN ST
24TH ST E
12
4
T
H
A
V
E
S
E
JOVIT
A
B
L
V
D
EA
S
T
V
A
L
L
E
Y
H
W
Y
S
E
12
2
N
D
A
V
E
E
BU
T
T
E
A
V
E
S 384TH ST
11
0
T
H
A
V
E
E
15TH ST SW
SE 288TH ST
2ND ST E
C
S
T
N
E
SE 312TH ST
S 277TH ST
W MAIN ST
15TH ST NW
C
S
T
N
W
19
8
T
H
A
V
E
E
53RD ST SE
9TH ST
E
29TH ST SE
GREEN VALLEY RD
1
7
9
T
H
A
V
E
SE 320TH ST
11
4
T
H
A
V
E
E
11
6
T
H
A
V
E
S
E
EDWARDS RD E
LAKE TAPPS PKWY SE
41ST ST SE
WE
S
T
V
A
L
L
E
Y
H
W
Y
S
W
STUCK
R
I
V
E
R
D
R
16TH ST E
K
E
R
S
E
Y
W
A
Y
S
E
14
7
T
H
A
V
E
S
E
4TH ST E
18TH ST E
M
S
T
N
E
12TH ST E
SE 304TH ST
1
9
0
T
H
A
V
E
E
11
2
T
H
A
V
E
E
3RD AVE SE
ELLINGSON RD SW
37TH ST SE
PE
R
I
M
E
T
E
R
R
D
SE 272ND ST
4
6
T
H
P
L
S
8TH ST NE
18
2
N
D
A
V
E
E
37TH ST NW
AC
A
D
E
M
Y
D
R
S
E
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
ORA
V
E
T
Z
R
D
S
E
VA
L
E
N
T
I
N
E
A
V
E
S
E
C
U
T
O
F
F
51
S
T
A
V
E
S
SE 282ND ST
14
4
T
H
A
V
E
S
E
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
55
T
H
A
V
E
S
1
8
5
T
H
A
V
E
E
21
4
T
H
A
V
E
E
D
S
T
S
E
1ST AVE SE
TA
C
O
M
A
B
L
V
D
D
S
T
N
W
A
S
T
N
E
4TH ST SE
CE
L
E
R
Y
A
V
E
30TH ST NE
10
8
T
H
A
V
E
EA
S
T
B
L
V
D
(
B
O
E
I
N
G
)
11
2
T
H
A
V
E
S
E
SE 316TH ST
14
8
T
H
A
V
E
S
E
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
S
T
N
E
M
S
T
N
W
O
S
T
N
E
S
E
3
6
8
T
H
P
L
W
S
T
N
W
1
6
9
T
H
A
V
E
E
S 287TH ST
3RD AVE S
5TH AVE SW
E
S
T
N
E
37TH ST NE
14
2
N
D
A
V
E
E
S 316TH ST
H
A
R
V
E
Y
R
D
S
C
E
N
I
C
D
R
S
E
H
S
T
N
W
M
A
I
N
S
T
S 292ND ST
WE
S
T
B
L
V
D
(
B
O
E
I
N
G
)
44TH ST NW
3RD AVE SW
11
8
T
H
A
V
E
E
10TH ST NE
CL
A
Y
S
T
N
W
4TH AVE SW
14
8
T
H
A
V
E
E
7TH ST SE
13
7
T
H
A
V
E
E
26
T
H
S
T
E
13
6
T
H
A
V
E
E
SE 310TH ST
S 3RD AVE
TH
O
R
T
O
N
A
V
E
S
W
2
0
0
T
H
A
V
E
E
17TH S
T
E
RIVE
R
D
R
BOUNDARY BLVD
LEA HIL
L
R
D
S
E
32ND ST E
11
8
T
H
A
V
E
S
E
58
T
H
A
V
E
S
AL
G
O
N
A
B
L
V
D
N
10
4
T
H
A
V
E
S
E
S 372ND ST
J
S
T
N
E
ROY RD SW
4TH ST NE
PA
C
I
F
I
C
A
V
E
S
11
0
T
H
A
V
E
S
E
14TH ST NE
DRIVEWAY
SE 281ST ST
12
6
T
H
A
V
E
E
5TH ST SE
72
N
D
A
V
E
S
56
T
H
P
L
S
25TH ST E
BR
I
D
G
E
T
A
V
E
S
E
57
T
H
A
V
E
S
S 328TH ST
DO
G
W
O
O
D
S
T
S
E
2ND AVE SW
8TH ST SE
S 279TH ST
L
S
T
S
E
T
S
T
S
E
F
S
T
S
E
FR
O
N
T
A
G
E
R
D
C
O
T
T
A
G
E
R
D
E
FO
S
T
E
R
A
V
E
S
E
52
N
D
A
V
E
S
SE 274TH ST
16
6
T
H
A
V
E
E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
49TH ST NE
S 362ND ST
I
S
T
N
W
32ND PL NE
54
T
H
A
V
E
S
A
S
T
S
W
57
T
H
P
L
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
47TH
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
S
T
S
E
R S
T
N
W
27TH ST E
15TH ST E
28TH ST E
MI
L
I
T
A
R
Y
R
D
S
13TH ST E
K
S
T
S
E
OL
I
V
E
A
V
E
S
E
10TH ST E
10
8
T
H
A
V
E
E
31ST ST NE
SE 323RD PL
54
T
H
P
L
S
B
S
T
S
E
WY
M
A
N
D
R
26TH ST SE
S 336TH ST
ST
P
A
U
L
B
L
V
D
S 340TH ST
C
S
T
S
E
B S
T
N
E
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
S
T
N
W
2ND ST SE
23RD ST SE
4TH AVE S
3RD ST SE
QU
I
N
C
Y
A
V
E
S
E
21ST ST NE
1
5
6
T
H
A
V
E
E
14
0
T
H
A
V
E
E
HE
M
L
O
C
K
S
T
S
E
1
8
4
T
H
C
T
E
5
6
T
H
A
V
E
S
10
6
T
H
A
V
E
E
SE 298TH PL
30TH ST SE
S 318TH ST
24TH ST SE
2ND AVE S
14TH ST E
H
S
T
N
E
LU
N
D
R
D
S
W
S 324TH ST
PI
K
E
S
T
N
W
21ST ST E
31ST ST E
42ND ST NW
6TH AVE SW
11
9
T
H
A
V
E
E
SE 286TH ST
9TH ST SE
55T
H
P
L
S
SE 276TH PL
65
T
H
A
V
E
S
SE 295TH PL
G
S
T
N
E
27TH ST SE5TH AVE N
SK
I
N
N
E
R
R
D
12
8
T
H
A
V
E
E
S 354TH ST
S 344TH ST
SE 364TH ST
SE 290TH ST
10TH ST SE
D
S
T
S
W
SE 280TH ST
2
1
1
T
H
A
V
E
E
NA
T
H
A
N
A
V
E
S
E
V
S
T
S
E
1
0
4
T
H
P
L
S
E
HI
C
R
E
S
T
D
R
B PL NW
SE 294TH ST
72ND ST SE
S 285TH ST
6TH ST NW
14
6
T
H
A
V
E
S
E
SE 293RD ST
3RD ST NW
12
6
T
H
A
V
E
S
E
I
S
A
A
C
A
V
E
S
E
S 312TH ST
EL
M
S
T
S
E
CLAY ST
S 370TH ST
20TH ST E
52
N
D
P
L
S
7TH ST E
19TH DR NE
SE 307TH PL
51ST
S
T
S
E
10TH AVE N
S 364TH ST
14
0
T
H
A
V
E
S
E
28TH ST SE
15TH ST SE
13
3
R
D
A
V
E
S
E
10
8
T
H
A
V
E
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
AL
D
E
R
L
N
S
11
7
T
H
A
V
E
S
E
U
S
T
S
E
19TH ST SE
6TH ST SE
11
0
T
H
P
L
S
E
A ST E WA
R
D
A
V
E
S
E
15
6
T
H
A
V
E
S
E
21ST ST SE
R PL NE
11
7
T
H
A
V
E
E
10
5
T
H
A
V
E
S
E
7TH ST
5TH ST NE
53
R
D
A
V
E
S
HE
A
T
H
E
R
A
V
E
S
E
F
S
T
N
E
11
2
T
H
P
L
S
E
51
S
T
P
L
S
SE 292ND ST
D PL SE
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
12
3
R
D
A
V
E
E
63
R
D
P
L
S
2ND CT NW
1ST ST NE
R
S
T
N
E
12
9
T
H
P
L
S
E
O
C
T
S
E
S 342ND ST
10
5
T
H
A
V
E
E
26TH ST NW
5TH ST E
SE 321ST PL
11
4
T
H
P
L
S
E
1ST AVE N
SE 282ND ST
SE 296TH ST
M
S
T
N
W
12TH ST E
55T
H
P
L
S
2ND ST SE
8TH ST E
SR 1
8
10
4
T
H
A
V
E
S
E
9TH ST E
SE 282ND ST
16TH ST E
R
S
T
N
W
8TH ST E
SE 272ND ST
11
8
T
H
A
V
E
S
E
32ND ST E
14
8
T
H
A
V
E
S
E
SE 272ND ST
SR 18
SE 284TH ST
14
2
N
D
A
V
E
E
V
S
T
S
E
10
6
T
H
A
V
E
E
SR 1
8
54
T
H
A
V
E
S
56
T
H
A
V
E
S
C S
T
N
W
SR
1
6
7
SR
1
6
7
10
5
T
H
A
V
E
E
8TH ST NE
D
S
T
S
E
21ST ST E
20
0
T
H
A
V
E
E
26TH ST NE
R
S
T
N
W
51
S
T
A
V
E
S
DRIVEWAY
SE 274TH ST
SR
1
6
7
51ST
S
T
S
E
D
R
I
V
E
W
A
Y
S 277TH ST
SE 301ST ST
12
4
T
H
A
V
E
S
E
SR
1
6
7
24TH ST E
14
4
T
H
A
V
E
S
E
51
S
T
A
V
E
S
SR
1
6
7
DRIV
E
W
A
Y
13TH ST E
SR
1
6
7
SR
1
6
7
55
T
H
A
V
E
S
H
S
T
N
E
10
8
T
H
A
V
E
E
D
R
I
V
E
W
A
Y
11
0
T
H
A
V
E
S
E
10
8
T
H
A
V
E
E
10
8
T
H
A
V
E
S
E
SR 18
SR
1
6
7
M
S
T
N
E
S 277TH ST
17TH ST SE
32ND ST E
COMPREHENSIVE STORM DRAINAGE PLAN
1 inch = 4,000 feet
April 2015
P:
\
A
u
b
u
r
n
\
1
4
5
2
9
5
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-
4
(
l
a
n
d
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s
e
)
.
m
x
d
0 4,000 8,000
Feet
Figure 4-4Land Use Designationsfor the City of Auburn
LEGEND
Roadway
Watercourse
Hydrography
Subbasins
Auburn City Boundary
Existing Land Use
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
Special Plan Area - Adopted
Special Plan Area - Proposed
¯
[Ú
[Ú
[Ú[Ú
[Ú
[Ú[Ú
[Ú
[Ú[Ú
[Ú[Ú[Ú[Ú[Ú
[Ú
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
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ver
Mill
Creek
CreekMill
G
r
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e
n
R
i
v
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r
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r
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e
n
River
White
G
r
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e
n
River
Soosette
Creek
River
W
hit
e
Bow man
C
re
e
k
W
h
i
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e
River
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
White
"
West Main PS "
A Street PS
"
Auburn Way South PS
"
Emerald Park PS
"
Brannan Park PS
"
White River PS
"
M Street PS
COMPREHENSIVE STORM DRAINAGE PLAN
1 inch = 4,000 feet
April 2015
LEGEND
[Ú Pump Station
Infiltration Pond or Swale
Detention Pond
Stormwater Vault or Tank
Storm Pipe
Open Channel (Ditch)
Roadway
Watercourse
Water Body
Wetland
Auburn City Boundary
P:
\
A
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\
1
4
5
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5
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)
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m
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d
0 4,000 8,000
Feet
Figure 4-5Drainage Infrastructure for the City of Auburn Storm Drainage 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
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n
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l
o
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h
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Lake Meridian
White
¬«S7
S
R
1
6
7
SR 1
8
A
S
T
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C
S
T
S
W
A
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R
N
W
A
Y
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B
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W
I
S
T
N
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AU
B
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R
N
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A
Y
N
R
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13
2
N
D
A
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E
S
E
WE
S
T
V
A
L
L
E
Y
H
W
Y
N
W
M
S
T
S
E
8TH ST E
E MAIN ST
24TH ST E
12
4
T
H
A
V
E
S
E
EA
S
T
V
A
L
L
E
Y
H
W
Y
S
E
12
2
N
D
A
V
E
E
BU
T
T
E
A
V
E
11
0
T
H
A
V
E
E
15TH ST SW
SE 288TH ST
2ND ST EJOVITA BLVD
C
S
T
N
E
S 384TH ST
SE 312TH ST
S 277TH ST
W MAIN ST
15TH ST NW
C
S
T
N
W
19
8
T
H
A
V
E
E
53RD ST SE
9TH ST E
29TH ST SE
GREEN VALLEY RD
1
7
9
T
H
A
V
E
SE 320TH ST
11
4
T
H
A
V
E
E
11
6
T
H
A
V
E
S
E
EDWARDS RD E
LAKE TAPPS PKWY SE
41ST ST SE
WE
S
T
V
A
L
L
E
Y
H
W
Y
S
W
STUCK
R
I
V
E
R
D
R
16TH ST E
K
E
R
S
E
Y
W
A
Y
S
E
14
7
T
H
A
V
E
S
E
4TH ST E
18TH ST E
M
S
T
N
E
12TH ST E
SE 304TH ST
1
9
0
T
H
A
V
E
E
11
2
T
H
A
V
E
E
3RD AVE SE
ELLINGSON RD SW
37TH ST SE
PE
R
I
M
E
T
E
R
R
D
SE 272ND ST
4
6
T
H
P
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S
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18
2
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D
A
V
E
E
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AC
A
D
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M
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D
R
S
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SE LAKE HOLM RD
22ND ST NE
L
A
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L
A
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D
H
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L
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W
A
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F
F
51
S
T
A
V
E
S
SE 282ND ST
14
4
T
H
A
V
E
S
E
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
55
T
H
A
V
E
S
1
8
5
T
H
A
V
E
E
21
4
T
H
A
V
E
E
D
S
T
S
E
1ST AVE SE
TA
C
O
M
A
B
L
V
D
A
U
B
U
R
N
-
E
N
U
M
C
L
A
W
R
D
D
S
T
N
W
A
S
T
N
E
4TH ST SE
TB
D
CE
L
E
R
Y
A
V
E
30TH ST NE
10
8
T
H
A
V
E
EA
S
T
B
L
V
D
(
B
O
E
I
N
G
)
11
2
T
H
A
V
E
S
E
SE 316TH ST
14
8
T
H
A
V
E
S
E
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
S
T
N
E
M
S
T
N
W
O
S
T
N
E
S
E
3
6
8
T
H
P
L
W
S
T
N
W
1
6
9
T
H
A
V
E
E
S 287TH ST
3RD AVE S
5TH AVE SW
E
S
T
N
E
37TH ST NE
14
2
N
D
A
V
E
E
S 316TH ST
H
A
R
V
E
Y
R
D
S
C
E
N
I
C
D
R
S
E
H
S
T
N
W
M
A
I
N
S
T
S 292ND ST
WE
S
T
B
L
V
D
(
B
O
E
I
N
G
)
44TH ST NW
3RD AVE SW
11
8
T
H
A
V
E
E
10TH ST NE
CL
A
Y
S
T
N
W
4TH AVE SW
14
8
T
H
A
V
E
E
7TH ST SE
13
7
T
H
A
V
E
E
26
T
H
S
T
E
13
6
T
H
A
V
E
E
SE 310TH ST
S 3RD AVE
TH
O
R
T
O
N
A
V
E
S
W
2
0
0
T
H
A
V
E
E
17TH
S
T
E
RIVE
R
D
R
BOUNDARY BLVD
LEA HIL
L
R
D
S
E
32ND ST E
11
8
T
H
A
V
E
S
E
58
T
H
A
V
E
S
AL
G
O
N
A
B
L
V
D
N
10
4
T
H
A
V
E
S
E
S 372ND ST
J
S
T
N
E
ROY RD SW
4TH ST NE
PA
C
I
F
I
C
A
V
E
S
11
0
T
H
A
V
E
S
E
14TH ST NE
D
R
I
V
E
W
A
Y
SE 281ST ST
16
0
T
H
A
V
E
S
E
12
6
T
H
A
V
E
E
5TH ST SE
72
N
D
A
V
E
S
56
T
H
P
L
S
25TH ST E
BR
I
D
G
E
T
A
V
E
S
E
57
T
H
A
V
E
S
S 328TH ST
DO
G
W
O
O
D
S
T
S
E
2ND AVE SW
8TH ST SE
S 279TH ST
L
S
T
S
E
T
S
T
S
E
F
S
T
S
E
FR
O
N
T
A
G
E
R
D
C
O
T
T
A
G
E
R
D
E
S 358TH ST
FO
S
T
E
R
A
V
E
S
E
52
N
D
A
V
E
S
SE 274TH ST
16
6
T
H
A
V
E
E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
49TH ST NE
S 362ND ST
I
S
T
N
W
54
T
H
A
V
E
S
A
S
T
S
W
57
T
H
P
L
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
13
5
T
H
A
V
E
S
E
47TH
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
S
T
S
E
R S
T
N
W
27TH ST E
15TH ST E
28TH ST E
MI
L
I
T
A
R
Y
R
D
S
13TH ST E
K
S
T
S
E
OL
I
V
E
A
V
E
S
E
10TH ST E
10
8
T
H
A
V
E
E
SE 323RD PL
B
S
T
S
E
WY
M
A
N
D
R
26TH ST SE
S 336TH ST
ST
P
A
U
L
B
L
V
D
S 340TH ST
C
S
T
S
E
B S
T
N
E
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
S
T
N
W
2ND ST SE
23RD ST SE
4TH AVE S
3RD ST SE
QU
I
N
C
Y
A
V
E
S
E
21ST ST NE
1
5
6
T
H
A
V
E
E
14
0
T
H
A
V
E
E
HE
M
L
O
C
K
S
T
S
E
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
S
T
N
E
LU
N
D
R
D
S
W
S 324TH ST
PI
K
E
S
T
N
W
21ST ST E
31ST ST E
42ND ST NW
6TH AVE SW
11
9
T
H
A
V
E
E
SE 286TH ST
9TH ST SE
55T
H
P
L
S
SE 276TH PL
65
T
H
A
V
E
S
SE 295TH PL
G
S
T
N
E
27TH ST SE5TH AVE N
SK
I
N
N
E
R
R
D
12
8
T
H
A
V
E
E
S 354TH ST
S 344TH ST
SE 364TH ST
SE 290TH ST
10TH ST SE
D
S
T
S
W
SE 280TH ST
2
1
1
T
H
A
V
E
E
NA
T
H
A
N
A
V
E
S
E
V
S
T
S
E
1
0
4
T
H
P
L
S
E
HI
C
R
E
S
T
D
R
B PL NW
SE 294TH ST
72ND ST SE
S 285TH ST
6TH ST NW
14
6
T
H
A
V
E
S
E
SE 293RD ST
3RD ST NW
12
6
T
H
A
V
E
S
E
I
S
A
A
C
A
V
E
S
E
S 312TH ST
EL
M
S
T
S
E
CLAY ST
S 370TH ST
20TH ST E
52
N
D
P
L
S
7TH ST E
19TH DR NE
SE 307TH PL
51ST
S
T
S
E
10TH AVE N
S 364TH ST
14
0
T
H
A
V
E
S
E
28TH ST SE
15TH ST SE
13
3
R
D
A
V
E
S
E
10
8
T
H
A
V
E
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
AL
D
E
R
L
N
S
11
7
T
H
A
V
E
S
E
U
S
T
S
E
19TH ST SE
6TH ST SE
11
0
T
H
P
L
S
E
A ST E WA
R
D
A
V
E
S
E
15
6
T
H
A
V
E
S
E
21ST ST SE
R PL NE
11
7
T
H
A
V
E
E
10
5
T
H
A
V
E
S
E
7TH ST
5TH ST NE
53
R
D
A
V
E
S
HE
A
T
H
E
R
A
V
E
S
E
F
S
T
N
E
11
2
T
H
P
L
S
E
51
S
T
P
L
S
SE 292ND ST
D PL SE
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
12
3
R
D
A
V
E
E
63
R
D
P
L
S
2ND CT NW
1ST ST NE
R
S
T
N
E
12
9
T
H
P
L
S
E
O
C
T
S
E
S 342ND ST
26TH ST NW
SE 321ST PL
11
4
T
H
P
L
S
E
53
R
D
A
V
E
S
M
S
T
N
W
17TH ST E
SE 292ND ST
SR 18
SE 282ND ST
SE 272ND ST
SR
1
6
7
10
8
T
H
A
V
E
S
E
10
4
T
H
A
V
E
S
E
D
R
I
V
E
W
A
Y
TBD
TBD
TB
D
12
4
T
H
A
V
E
S
E
14
8
T
H
A
V
E
S
E
SR
1
6
7
14
4
T
H
A
V
E
S
E
51ST
S
T
S
E
SR
1
6
7
20
0
T
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A
V
E
E
2ND ST SE
DRIVEWAY
SE 284TH ST
55
T
H
A
V
E
S
TB
D
H
S
T
N
E
C S
T
N
W
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V
S
T
S
E
SR 1
8SR 1
8
SE 288TH ST
9TH ST E
56
T
H
A
V
E
S
SR
1
6
7
14
2
N
D
A
V
E
E
26TH ST NE
SE 282ND ST
17TH ST SE
TB
D
SR
1
6
7
51
S
T
A
V
E
S
TBD
S 277TH ST
SE 272ND ST
T
B
D
16TH ST E
TB
D
SE 274TH ST
TB
D
21ST ST E
TBD
24TH ST E
TBD
10
8
T
H
A
V
E
E
TB
D
M
S
T
N
E
8TH ST E
SR
1
6
7
TB
D
R
S
T
N
W
8TH ST E
1ST AVE N
51
S
T
A
V
E
S
S 277TH ST
32ND ST E
SR
1
6
7
TBD
R
S
T
N
W
D
R
I
V
E
W
A
Y
32ND ST E
12TH ST E
SR
1
6
7
D
S
T
S
E
8TH ST NE
SE 296TH ST
13TH ST E
DRIVEWAY
SR 18
55T
H
P
L
S
TBD
OPC8
OPC4
OPC11
OPS1
OPC9
OPC1 OPC3
OPC6OPC7
OPC5OPC2
OPC10
OPS2
OPS3
OPS4
OPS5
OPS6
COMPREHENSIVE STORM DRAINAGE PLAN
1 inch = 4,000 feet
April 2015
P:
\
A
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b
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.
m
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Feet
Figure 4-6City and Storm DrainageCritical Facilities forthe City of Auburn
LEGEND
!(S1 Storm Critical Facility
!(C1 City Critical Facility
Roadway
Watercourse
Water Body
Wetland
Auburn City Boundary
OPC1 OPC3
OPC5
OPC2
A
S
T
S
E
C
S
T
S
W
E MAIN ST
C
S
T
N
W
SR 18
4TH ST NE
E
S
T
N
E
4TH ST SE
I
S
T
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D
S
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S
E
AU
B
U
R
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W
A
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S
2ND ST NE
F
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H
S
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G
S
T
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E
D
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W
A
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T
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W
A
S
T
N
E
7TH ST SE
W MAIN ST
8TH ST SE
B
S
T
N
E
1ST ST NE
3RD ST NE
A
S
T
N
W
H
S
T
N
E
D
S
T
S
W
3RD ST NW
S
D
I
V
I
S
I
O
N
S
T
6TH ST SE
PARK AVE NE
6TH ST NE
5TH ST SW
SR 18
6TH ST SE
8TH ST SE
D
S
T
S
E
7TH ST SE
SR 18OPS1OPS2
SEE INSET
INSET
¯
CITY CRITICAL FACILITIES C1 City Hall 25 W Main Street C2 City Hall Annex 1 E Main Street C3 Justice Center 340 E Main Street C4 Maintenance and Operations 1305 C Street SW C5 Regional Hospital 210 N Division Street C6 Senior Center 808 9th Street SE C7 VRFA Station 31 1101 D Street NE C8 VRFA Station 32 1951 R Street SE C9 VRFA Station 33 500 182nd Avenue E C10 VRFA Station 34 31290 124th Avenue SE C11 VRFA Station 35 2905 C Street SW
STORM CRITICAL FACILITIES S1 A Street PS 404 A Street SE S2 Auburn Way S PS 405 Auburn Way S S3 Brannan Park PS 1302 30th Street NE S4 Emerald Park PS 499 42nd Street NE S5 West Main Street PS 1410 W Main Street S6 White River PS 4640 A Street SE S7 M Street PS 410 M Street SE
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ver
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11
0
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C
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LAKE TAPPS PKWY SE
19
8
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53RD ST SE
9TH ST
E
29TH ST SE
GREEN VALLEY RD
1
7
9
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11
4
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11
6
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14
7
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18TH ST E
M
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1
9
0
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11
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37TH ST SE
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M
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4
6
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18
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14
4
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55
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1
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5
T
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E
21
4
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A
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10
8
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U
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14
8
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6
8
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1
6
9
T
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5TH AVE SW
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2
N
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T
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N
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T
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S
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(
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E
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N
G
)
44TH ST NW
3RD AVE SW
11
8
T
H
A
V
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E
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CL
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Y
S
T
N
W
4TH AVE SW
14
8
T
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A
V
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7TH ST SE
13
7
T
H
A
V
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E
26
T
H
S
T
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13
6
T
H
A
V
E
E
SE 310TH ST
S 3RD AVE
TH
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R
T
O
N
A
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W
2
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11
8
T
H
A
V
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S
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58
T
H
A
V
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S
AL
G
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N
A
B
L
V
D
N
10
4
T
H
A
V
E
S
E
S 372ND ST
J
S
T
N
E
ROY RD SW
4TH ST NE
PA
C
I
F
I
C
A
V
E
S
11
0
T
H
A
V
E
S
E
14TH ST NE
D
R
I
V
E
W
A
Y
SE 281ST ST
12
6
T
H
A
V
E
E
5TH ST SE
72
N
D
A
V
E
S
56
T
H
P
L
S
25TH ST E
BR
I
D
G
E
T
A
V
E
S
E
67TH S
T
S
E
57
T
H
A
V
E
S
S 328TH ST
DO
G
W
O
O
D
S
T
S
E
2ND AVE SW
8TH ST SE
S 279TH ST
L
S
T
S
E
T
S
T
S
E
F
S
T
S
E
FR
O
N
T
A
G
E
R
D
C
O
T
T
A
G
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R
D
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S
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R
A
V
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S
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52
N
D
A
V
E
S
SE 274TH ST
1ST ST E
16
6
T
H
A
V
E
E
1ST AVE N
SE 299TH ST
SE 316TH PL
SE 284TH ST
49TH ST NE
S 362ND ST
NO
R
M
A
N
A
V
E
S
E
54
T
H
A
V
E
S
A
S
T
S
W
57
T
H
P
L
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
2
0
4
T
H
A
V
E
E
28TH ST NE
8
6
T
H
A
V
E
S
S 356TH ST
J
S
T
S
E
R S
T
N
W
27TH ST E
15TH ST E
28TH ST E
MI
L
I
T
A
R
Y
R
D
S
13TH ST E
K
S
T
S
E
OL
I
V
E
A
V
E
S
E
10TH ST E
10
8
T
H
A
V
E
E
SE 323RD PL
54
T
H
P
L
S
B
S
T
S
E
26TH ST SE
S 336TH ST
ST
P
A
U
L
B
L
V
D
S 340TH ST
C
S
T
S
E
B S
T
N
E
32ND S
T
S
E
S 300TH ST
1ST AVE S
36TH ST SE
ELM LN
64TH ST S
E
SE 301ST ST
2
0
8
T
H
A
V
E
E
SE 287TH ST
V
S
T
N
W
2ND ST SE
23RD ST SE
4TH AVE S
3RD ST SE
QU
I
N
C
Y
A
V
E
S
E
29TH ST NW
21ST ST NE
1
5
6
T
H
A
V
E
E
HE
M
L
O
C
K
S
T
S
E
1
8
4
T
H
C
T
E
5
6
T
H
A
V
E
S
31ST ST SE
10
6
T
H
A
V
E
E
SE 298TH PL30TH ST NW
S 318TH ST
24TH ST SE
2ND AVE S
14TH ST E
H
S
T
N
E
LU
N
D
R
D
S
W
S 324TH ST
PI
K
E
S
T
N
W
21ST ST E
31ST ST E
42ND ST NW
6TH AVE SW
17TH
S
T
E
11
9
T
H
A
V
E
E
SE 286TH ST
9TH ST SE
55
T
H
P
L
S
SE 276TH PL
SE 295TH PL
G
S
T
N
E
O
S
T
S
E
27TH ST SE5TH AVE N
SK
I
N
N
E
R
R
D
1
0
2
N
D
A
V
E
S
E
12
8
T
H
A
V
E
E
S 354TH ST
S 344TH ST
SE 364TH ST
SE 290TH ST
10TH ST SE
D
S
T
S
W
SE 280TH ST
2
1
1
T
H
A
V
E
E
NA
T
H
A
N
A
V
E
S
E
V
S
T
S
E
HI
C
R
E
S
T
D
R
B PL NW
SE 294TH ST
S 285TH ST
6TH ST NW
14
6
T
H
A
V
E
S
E
SE 293RD ST
V
C
T
S
E
PE
A
R
L
A
V
E
S
E
3RD ST NW
16TH ST SE
I
S
A
A
C
A
V
E
S
E
L
S
T
N
E
EL
M
S
T
S
E
CLAY ST
S 370TH ST
20TH ST E
52
N
D
P
L
S
7TH ST E
19TH DR NE
SE 307TH PL
10TH AVE N
SE 314TH ST
S 364TH ST
14
0
T
H
A
V
E
S
E
72ND ST SE
15TH ST SE
13
3
R
D
A
V
E
S
E
10
8
T
H
A
V
E
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
AL
D
E
R
L
N
S
11
7
T
H
A
V
E
S
E
U
S
T
S
E
19TH ST SE
6TH ST SE
11
0
T
H
P
L
S
E
A ST E
15
6
T
H
A
V
E
S
E
21ST ST SE
R PL NE
11
7
T
H
A
V
E
E
10
5
T
H
A
V
E
S
E
7TH ST
5TH ST NE
53
R
D
A
V
E
S
HE
A
T
H
E
R
A
V
E
S
E
F
S
T
N
E
11
2
T
H
P
L
S
E
51
S
T
P
L
S
SE 292ND ST
D PL SE
S 320TH ST
SE 272ND PL
8TH ST SW
6TH AVE N
22ND ST E
12
3
R
D
A
V
E
E
TH
O
R
T
O
N
P
L
S
W
2ND CT NW
1ST ST NE
12
9
T
H
P
L
S
E
6TH ST NE
3RD ST NE
O
C
T
S
E
S 342ND ST
SE 315TH PL
26TH ST NW
SE 321ST PL
11
4
T
H
P
L
S
E
SR 18
SR
1
6
7
17TH ST E
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COMPREHENSIVE STORM DRAINAGE PLAN
1 inch = 4,000 feet
April 2015
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Figure 4-7Drainage Problem Locations forthe Storm Drainage Utility¯
ID Location P1 South of West Main Street east of the SR 167 overpass P2 Intersection of 37th Street NW and I Street NW P3 Hillsides throughout the city P4A East of I Street NE between 32nd Street NE and 35th Street NE P4B C Street NE between 30th Street NE and 37th Street NE P5 West Hills P6 Northern extent of airport property near 30th Street NE P7 Western end of 25th Street SE near D Street SE right-of-way P8 23rd and K Streets SE
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Chapter 5
Evaluation of the Storm Drainage
Utility
This chapter presents analyses conducted to evaluate the Storm Drainage Utility and identify gaps
between existing service levels and the desired LOS described in Section 3.2.2. The following types of
evaluations were completed to identify Storm Drainage Utility future activities to address the range of
LOS goals:
• Hydraulic: gather system data, update or develop computer models, assess hydraulic performance,
and develop capital improvement projects with respect to LOS and associated system design criteria
• Asset management: develop system requirements specification for integrating the City’s pipe
criticality database, which is the basis of the City’s pipe repair and replacement asset management
model, into the City’s Cartegraph CMMS
• Environmental: determine differences between the 2013–18 permit and previous NPDES Permit,
and evaluate how the differences could affect City regulations, facilities, and activities; conduct an
NPDES program gap analysis; update the existing Compliance Work Plan; and estimate the time and
costs for NPDES Permit compliance
• Maintenance and operations: assess process performance, equipment, and personnel with respect
to LOS for M&O
These evaluations were conducted to develop capital improvements for the 6- and 20-year horizons, as
well as identify future M&O needs. The following sections summarize the hydraulic, asset management,
and environmental evaluations. The M&O evaluations are described in Chapter 6.
Hydraulic Evaluation 5.1
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. For the 2009 Plan,
models were developed to assess the system on a per basin or problem area scale in MIKE URBAN4
software. Subsequent to the 2009 Drainage Plan, the City converted the existing hydraulic models to the
PCSWMM5 software platform and updated the models with new survey data, and construction and
record drawings. Additionally, some models were updated by calibrating to flow monitoring data collected
in 2010 and 2011.
4 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 PCSWMM is a GIS-based hydraulic and hydrologic modeling platform developed by Computational Hydraulics International
(CHI). The software fully supports the EPA SWMM5 hydrology and hydraulics engine, thus providing comparable computation
between EPA SWMM and PCSWMM models. Information about PCSWMM software can be found at
http://www.chiwater.com/Software/PCSWMM/index.asp.
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Hydraulic modeling efforts for the 2015 Drainage Plan focused on updating those models covering
locations of existing problems as described in Chapter 4. The model updates were based on recent GIS
data, design drawings, and record drawings. Some model updates also included calibration to flow
monitoring data collected in 2010 and 2011. For problem areas that had not been previously modeled,
new PCSWMM models were developed or WWHM 6 was used to estimate flow for capital improvement
project sizing.
The following sections describe the steps used to update existing models or develop new models.
5.1.1 Updating Existing Models
The hydraulic components of existing models were updated with recent GIS data. The following model
data were verified against the GIS data:
• pipe size
• pipe invert elevations
• pipe material (for estimating pipe roughness)
• node rim elevation
• system connectivity
Where the GIS data did not accurately describe the existing system, technical reports, record drawings,
or construction drawings were used to update the model. Where data were available, models were given
more detail with respect to pump and storage facility information.
For model hydrology, subcatchment delineations within problem areas were reviewed and revised based
on recent GIS data, topographic data, and 2012 aerial photography. Total impervious area was
estimated with the City’s impervious area coverage. Subcatchment slope was estimated as the average
slope based on a digital elevation model. Where available, flow monitoring data were used to calibrate
modeled flow by adjusting effective impervious area and soil conductivity parameters.
5.1.2 Creating New Models
The following is a general description of steps followed to develop new PCSWMM models:
1. Infrastructure data from existing GIS databases were used to build drainage networks in problem
areas. Drainage network models consist of catch basins, manholes, pipes, junctions, ditches, control
structures, vaults, storage ponds, pump stations, and outfalls. GIS data were validated and
augmented as necessary based on record drawings and City-conducted field investigations.
2. The drainage network was developed to a level of detail that is sufficient for analyzing conveyance
on a subbasin-wide or problem-specific scale. In general, 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 unless they provided an important link within the system.
3. Subbasin areas were divided into smaller drainage area delineations called subcatchments, 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 subcatchment. Subcatchment
slope was estimated as the average slope based on a digital elevation model (DEM). Total
impervious area was estimated with the City’s impervious area coverage.
6 WWHM is a western Washington-specific hydrology model developed for the Washington State Department of Ecology. The
software is based on HSPF continuous-simulation hydrology methodologies and uses regional HSPF parameters and long-term
recorded precipitation data. Information about WWHM software can be found at
http://www.ecy.wa.gov/Programs/wq/stormwater/wwhmtraining/index.html.
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4. Models were calibrated using either pump runtime data or flow monitoring data where available.
5. Long-term simulations were performed to determine the 2 percent and 4 percent exceedance
storms (one in 50-year and one in 25-year flows, respectively). These storms were used as design
storms to identify ways to alleviate existing drainage problems through capital improvements, which
meet the LOS (see Chapter 7 for a description of proposed capital improvements).
The following is a general description of steps followed to develop new WWHM models:
1. Subcatchments within subbasins were delineated with existing GIS information including 2012
aerial photography, roadway extents, contours, and drainage network (catch basins, manholes,
pipes, ditches, infalls, and outfalls).
2. Existing GIS information was used to determine hydrologic parameters, per subcatchment, used by
WWHM such as hydrologic soil type, slope, and impervious area. Since subbasins were relatively
small, slope was estimated from City 2-foot contour data, instead of the coarser DEM. Total
impervious area was estimated with the City’s impervious area coverage. 2012 Aerial photography
was used to estimate vegetation.
3. WWHM model results provide annual peak flows, and determines the 2 percent and 4 percent
exceedance storms (one in 50-year and one in 25-year flows, respectively). These flows were used
as design storms to identify ways to alleviate existing drainage problems through capital
improvements, which meet the LOS (see Chapter 7 for a description of proposed capital
improvements).
Appendix C provides a detailed description of the hydrologic and hydraulic (H&H) modeling
methodologies.
Asset Management Evaluation 5.2
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, asset management is a systematic approach
to maintaining assets in good working order to minimize future costs of maintaining and replacing them,
especially to avoid costly deferred maintenance. The best practices for asset management involve
systematically basing choices on an understanding of asset condition and performance, risks, and costs
in the long term. Asset best practices include:
• having knowledge about assets and costs (i.e., detailed inventories)
• maintaining desired LOSs
• taking a life-cycle approach to asset management planning
• implementing the planned solutions to provide reliable, cost-effective service
• establishing funding levels and rates to support ongoing infrastructure rehabilitation or replacement
projects
The first step to effectively managing 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 second step is preparing a
comprehensive inventory of the assets. 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.
Asset management evaluations completed for the 2009 Drainage Plan focused on pipes and pump
stations. A pipe criticality database and an economic life model were developed. The pipe criticality
database contained data (i.e. pipe diameter, age, length, material, depth of bury, condition) describing
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the current conditions of the pipe network. The data in the database were the basis for the economic life
model. The economic life model was used to evaluate the life-cycle costs and risk for the City’s drainage
pipe assets. The model estimated a risk cost associated with each asset by multiplying a probability of
failure in a given year by the cost (including capital, social, and environmental costs) of that asset failing.
Then the risk cost associated with each asset was compared to the life-cycle cost of owning the asset to
estimate the timing for repair or replacement.
The results of the economic model are only as good as the input data describing the pipes. For the 2009
planning effort, the pipe inventory was incomplete and pipe data for many pipes were missing. Since
then, the City has systematically been inventorying the system, and collecting necessary pipe data which
are stored in GIS for future link to Cartegraph. A quarter of the system, however, is still missing pipe
material and/or installation date data, which are needed for the economic life model (Figure 5-1). The
City are in the process of collecting these data.
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Figure 5-1. Drainage Pipe Summary
Unknown
4%
< 12 inches
21%
12–22 inches
65%
24–30 inches
7%
36–51 inches
3%
>= 54 inches
< 1%
Unknown
< 12 inches
12–22 inches
24–30 inches
36–51 inches
>= 54 inches
Pipe Diameter
Unknown
27%
ADS
2%
CMP
7% Concrete
23% Ductile iron
6%
HDPE
1%
Other
< 1%
PVC
34%
Unknown
ADS
CMP
Concrete
Ductile iron
HDPE
Other
PVC
Pipe Material
Unknown
24%
1960s
4%
1970s
4% 1980s
15% 1990s
22%
2000s
25%
2010s
6%
Unknown
1960s
1970s
1980s
1990s
2000s
2010s
Pipe Installation Date
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Evaluations completed for this Drainage Plan consisted of developing a system requirements
specification for implementing the economic life model using the data in the City’s asset management
system, Cartegraph (Brown and Caldwell, 2014). Once the pipe inventory is complete, and the economic
life model is implemented, the model can be rerun and used to inform future R&R priorities. Currently,
the economic life model includes only collection system piping, and there is an opportunity to expand the
model to include the catch basins and manholes, as described in Chapter 8.
Environmental Investigation 5.3
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 has an established municipal SWMP that complies with all
Permit requirements currently in effect. Updates to the City’s codes, programs, and standards are being
developed to comply with the requirements of the updated 2013 NPDES Permit.
The City’s SWMP Plan identifies activities that will be implemented by the City to comply with NDPES
Permit requirements. The SWMP Plan is updated annually to reflect new requirements that phase in
during each year, including one-time and new ongoing activities. An updated SWMP Plan is submitted to
Ecology in March of each year. The City’s current SWMP Plan is accessible on the City website.
To plan for upcoming requirements of the new NPDES permit, the City formed a project team consisting
of staff from the City Attorney’s office, the City Community Development and Public Works, and Brown
and Caldwell.
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 updated section of the Permit. Interviews were then conducted with appropriate
staff (e.g., stormwater M&O staff) to discuss the potential implications of Permit changes for existing City
codes, programs, and standards. The information on existing City practices and programs was then
compared to the updated Permit requirements 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 5-year Compliance Work Plan (see Appendix B). Recommended
future activities from the Compliance Work plan are summarized in Chapter 8.
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Chapter 6
Maintenance and Operations
An evaluation of existing Storm Drainage Utility M&O activities was conducted in support of this Drainage
Plan. This chapter documents existing Storm Drainage Utility M&O activities with the primary purpose of
establishing a baseline understanding of the proactive and responsive maintenance procedures
performed by City Storm Drainage Utility M&O staff. This baseline understanding is used herein to
evaluate utility staffing, data collection and computerized record-keeping needs, and other utility needs
necessary to continue to meet LOS goals.
The information provided in this chapter is a summary of information collected during City Storm
Drainage Utility staff interviews, review of computerized records, and existing utility forms/checklists.
Utility Responsibility and Authority 6.1
This section provides an overview of the Storm Drainage Utility organization and basic information
related to utility staffing, training, and education.
6.1.1 Organizational Structure
The City Storm Drainage Utility is operated as a utility enterprise under the direction of the Director of
Community Development and Public Works. The Department of Community Development and Public
Works is responsible for planning, design, construction, operation, maintenance, quality control, and
management of the storm drainage system. The City has a mayor-council form of government; therefore,
the Director of Community Development and Public Works reports to the Mayor, with input from Council
through Council study sessions and meetings. The Mayor and the City Council provide oversight for the
implementation of policies, planning, and management for the Storm Drainage Utility.
Engineering Services (Engineering) within Community Development and Public Works is the lead group
for comprehensive storm drainage system planning; development of a CIP; and the design, construction,
and inspection of projects related to the storm drainage system. The Assistant Director of
Engineering/City Engineer oversees Engineering and reports directly to the Community Development and
Public Works Director.
Maintenance and Operations Services is the group responsible for the day-to-day maintenance and
operation of the storm drainage system. The Sewer/Storm Drainage Operations Manager reports to the
Assistant Director of Public Works Operations, and oversees nine storm drainage employees including a
field supervisor.
The overall Community Development and Public Works Department organizational structure is shown in
Figure 2-1.
6.1.2 Staffing Level
The Storm Drainage Utility currently includes eight full-time M&O field staff, two seasonal staff, plus a
field supervisor and an M&O manager, who perform administrative duties. This chapter does not include
an evaluation of utility management, including regulatory compliance, planning, and coordination with
other City departments. Position titles and the primary functions of the M&O staff working within the
Storm Drainage Utility are shown in Table 6-1.
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Table 6-1. Storm Drainage Utility M&O Personnel
Position Primary function(s)
Sewer/Storm Manager Management of sewer and storm M&O staff
Storm field supervisor Supervision of field staff
Maintenance worker II Six full-time staff dedicated to field inspection and maintenance
Maintenance worker I Two full-time staff dedicated to field inspection and maintenance
Seasonal employee Two seasonal staff, for four months of the year, for field inspection and
maintenance
In addition to the M&O field staff identified in Table 6-1, full-time and seasonal staff support the
following Storm Drainage functions:
• Management and administration: A full-time manager performs administrative duties for both the
Sewer and Storm Divisions. Management and administrative tasks include general oversight of the
Sewer and Storm Drainage utilities M&O staff, regulatory compliance, planning, and coordination
with other City departments. Field work is supervised by a full-time field supervisor.
• Vegetative maintenance: Six full-time and nine seasonal Street/Vegetation Division staff support the
Storm Drainage Utility M&O field staff with vegetative control, catch basin leaf removal, grounds
maintenance, and landscaping duties.
• Contracted services: The Storm Drainage Utility contracts with other City departments or external
contractors for some services, as discussed in Section 6.3.
Vegetative maintenance staff and other contracted services are financed by the Storm Drainage Utility.
M&O activities are discussed in Sections 6.2 and 6.3, respectively. The staffing plan presented in
Section 6.6 considers only M&O activities provided by the Storm Drainage Utility.
6.1.3 Level of Service
The Storm Drainage Utility operates in accordance with the LOS criteria outlined in Chapter 3, and
internally adopted goals integral to meeting those levels. These goals are generally based on the current
staffing level and tasks deemed most critical to the City and its residents. However, the existing staffing
requirements discussed in Section 6.6 herein include near-term goals, which may not be met by existing
staff.
6.1.4 Training and Education
The City recognizes the value of having a knowledgeable and well-trained staff operating the storm
drainage system, and encourages employees to obtain the highest level of training available. At this
time, the State of Washington does not require certification for stormwater maintenance operators but
the City would support any effort to establish certification for these positions. Seminars, conferences,
and college coursework have become tools to advance knowledge for maintenance staff.
Many M&O staff are specialized in specific job functions, which can promote expertise through
specialization but also has the potential to limit the ability of the utility to absorb absences due to
vacation, sickness, retirement, resignation, and termination. To mitigate this limitation, the City has
broadened the scope of the Storm Drainage Utility’s education system by initiating a cross-training
program.
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Routine Operations Provided by the Storm Drainage Utility 6.2
This section discusses routine operations provided by the Storm Drainage Utility M&O staff shown in
Table 6-1. Each sub-section provides a brief description of the M&O activity, City goals with respect to
proactive maintenance, and the estimated Storm Drainage Utility staff effort to achieve the proactive
maintenance goal.
6.2.1 Catch Basin and Manhole Inspection, Cleaning, and Repair
The storm drainage system includes approximately 8,880 catch basins and 2,330 manholes. Catch
basin and manhole maintenance includes initial inspection and potential follow-up cleaning and/or
repair. Inspection is performed by one person using utility mapping to locate the targeted facilities. M&O
staff use an inspection checklist to identify which facilities require further cleaning or repair. The
checklist includes items such as observation of trash, debris, sediment, or vegetation blocking or within
the catch basin/manhole; structural damage; evidence of contamination or pollution; and the integrity of
catch basin grates, manhole covers, and ladders. Follow-up cleaning and maintenance work orders are
generated based upon the results of initial inspection and typically include a two-person crew. Based
upon recent maintenance history, it is assumed that approximately one in five catch basin/manhole
inspections leads to further cleaning. The City assumes that a total of 50 catch basins and manholes per
year require some level of maintenance/repair.
Catch basin inspection is required as part of the City’s NPDES Phase II Municipal Stormwater Permit,
recently updated in August 2013. Beginning in 2015, the City is required to inspect and maintain all
catch basin facilities every 2 years. To achieve this permit requirement, the City goal is to inspect 60
catch basins per day. Manhole inspection frequency is not mandated by the permit, but the City’s goal is
to complete inspection of all City manholes on a 4-year rotating schedule.
In the future, the City intends to demonstrate (through maintenance records) that catch basins do not
require inspection every 2 years. The City will use Cartegraph software (see Section 6.5) to record and
track results of catch basin inspection, cleaning, and maintenance efforts.
6.2.2 Stormwater Pipeline Cleaning and CCTV
The storm drainage system includes approximately 210 miles of collection system piping. Cleaning and
inspection of the storm drainage system is performed using City-owned vactor/jet truck and closed-
circuit television (CCTV) equipment. Cleaning and CCTV inspection are typically performed in tandem
from structure to structure (i.e., catch basin or manhole) by a two-person crew for each task.
Jetting of stormwater pipelines and subsequent vactor truck suction is the principal means of removing
debris or obstructions from the storm drainage system. A hose with a special end fitting is inserted into a
pipe and high-pressure water (up to 2,500 pounds per square inch) is sent through the hose. The high-
pressure water exits the small hole at the tip of the nozzle, breaking down and/or scouring obstructions.
Debris is then removed via suction by the vactor truck equipment at each manhole.
Following cleaning, CCTV inspection is performed to identify structural defects and potential pipeline
leaks. “Lamping” inspections, where the camera is inserted into the manhole or catch basin but not
advanced through the pipe system, are typically performed as a first step of the CCTV process. Although
the visual range is limited, lamping can identify structures and piping in very good condition. In these
cases, no additional CCTV inspection is completed. Lamping is generally limited to areas of newer pipe or
low-priority facilities.
Routine CCTV inspection of the storm drainage system is an essential component of the M&O program
as it can identify trouble spots before larger failures occur and can provide the City with accurate
information about the condition of the storm drainage system. Since the end of 2007, inspection reports
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and digital video captured by the CCTV crews have been stored within the City’s computer network
(flexidata software). While the ability to edit information in flexidata is limited to licensed machines, the
flexidata reader is available for all City staff. Currently, the City does not have the ability to transfer the
data stored in flexidata, specifically a summary of pipe condition, to the more comprehensive data
stored within Cartegraph, the utility CMMS software. A primary goal of the utility in the near future is to
use the results of CCTV inspection to populate pipe conditions fields within Cartegraph in order to
provide a more accurate planning tool based upon the known condition of storm drainage system
assets.
The City’s goal is to clean and inspect all stormwater collection pipes within the system on a 10-year
cycle. On average, a two-person crew can clean approximately 1,500 feet of pipe per day and inspect
approximately 500 feet of pipe per day.
6.2.3 Stormwater Outfall Inspection, Cleaning, and Maintenance
The storm drainage system includes 65 outfalls, or discharges from localized collection systems to rivers
or streams. Outfall maintenance includes initial inspection and potential follow-up corrective actions.
Outfall inspections are performed to identify excessive vegetative growth that could obstruct flow, outfall
erosion protection, structural damage to the pipe itself, and abnormal discharge from the pipe that might
be indicative of contamination (i.e., color/sheen or odor). Follow-up cleaning and maintenance work
orders are generated based upon the results of initial inspection. The City goal is to inspect each outfall
seasonally (four times per year) and to perform maintenance at least annually, or at a greater frequency
depending upon inspection results. On average, inspection and maintenance activities require 0.75 hour
and 1.0 hour, respectively, for a two-person crew.
6.2.4 Drainage Ditch Maintenance and Restoration
The storm drainage system includes approximately 40 miles of drainage ditches. Drainage ditch
maintenance is required to preserve the original line and grade, hydraulic capacity, and purpose of the
ditch. Routine maintenance activities include re-grading and removal of sediment; nuisance vegetation;
and isolated obstructions such as trash, trees, and accumulated debris. Because vegetation is important
for erosion control, the City strives to minimize the removal of beneficial vegetation.
Drainage ditch maintenance efforts are time-consuming for the Storm Drainage Utility. Up to six M&O
staff are required for a single ditch maintenance crew to operate the City-owned excavator, control traffic
(as necessary), and manually re-grade or remove obstructions. The City assigns a six-person ditch
maintenance crew approximately 15 days per year (3 days per week for 1, out of 4, month in the
summer). On average, these crews can complete 200 feet of ditch maintenance per day. The City’s goal
is to maintain all ditches within the system on a 20-year cycle.
6.2.5 Stormwater Pond and Swale Inspection, Maintenance, and Restoration
Inspection of the approximately 150 City stormwater ponds and 75 swales is performed by a two-person
crew using an inspection checklist to identify conditions that require correction. The checklist includes
items such as observation of trash, debris, sediment, and animal or insect infestation that could impact
pond function or future maintenance; structural damage or erosion; evidence of contamination or
pollution; and the integrity/function of emergency overflow spillways. On average, inspection activities
require 1.0 hour for a two-person crew per location. Follow-up maintenance and restoration is scheduled
during the summer months. The City assigns a six-person stormwater pond/swale crew approximately 45
days per year (3 days per week for 3, out of 4, months in the summer).
The City goal is to inspect each pond/swale twice per year. Maintenance and restoration are performed
as necessary. After major storms (greater than 10-year events), it is recommended that some
stormwater ponds be inspected briefly to verify proper function and identify damage, if any. It is
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recommended that the City develop a list of ponds that should be inspected following these major
storms. Some larger City ponds have been maintained by King County staff, as discussed in Section 6.3.
6.2.6 Culvert Inspection and Cleaning
Culvert maintenance includes inspection and cleaning of the approximately 800 culverts within the
storm drainage system. Culverts are typically inspected by a two-person crew, with corrective actions and
cleaning performed during the inspection when possible. On average, inspection and cleaning activities
require 0.75 hour for a two-person crew. Culvert inspection focuses on the assessment of free flow
within the culvert and identifying any structural defects. Any debris that cannot be removed during the
initial inspection or any noted structural concerns result in a work order for corrective action. The City
goal is to inspect (and clean as necessary) each culvert twice per year.
6.2.7 General Facility Maintenance and Other Field Tasks
Storm Drainage Utility M&O staff perform a number of duties that do not readily fall into the categories
previously listed, and often support other City departments. Examples of these additional storm drainage
tasks include:
• General facility maintenance: Maintenance may include detention vault cleaning and sediment
removal, weir cleaning, filter inspection and cleaning, and maintenance of oil/water separators.
• Engineering support: Storm Drainage Utility M&O staff often provide facility inspection services for
Engineering projects and support Engineering through visual observation in the field. M&O staff also
make small repairs such as replacing catch basins or failed culverts, or minor drainage pipe
replacement. See Section 6.7 for recommendations related to documenting M&O repair projects.
It is difficult to quantify in terms of full-time equivalent (FTE) the general inspection and field tasks
performed by Storm Drainage Utility staff. Many of the activities occur outside of a regular maintenance
schedule. FTE assumptions are summarized in Section 6.6.
Routine Operations Provided to the Storm Drainage Utility 6.3
This section discusses routine operations performed by City Storm Drainage Utility M&O staff or by other
contracted services. Each sub-section provides a brief description of the M&O activity. FTE efforts for
these activities are funded by the Storm Drainage Utility, but are not included in existing staffing
requirements discussed in Section 6.6.
6.3.1 Vegetative Maintenance
Vegetative maintenance is performed by Street/Vegetation Division full-time and seasonal staff that
support City Storm Drainage Utility M&O staff. Vegetative maintenance includes mowing, herbicide
application, seeding and re-planting, and removal of nuisance vegetation or vegetation that impairs the
function of storm drainage facilities. In the fall, vegetative maintenance also includes removal of leaves
that can accumulate and block flow to catch basins.
Full-time Storm Drainage Utility staff may also perform limited vegetative maintenance as part of the
routine operations discussed in Section 6.2.
6.3.2 Stormwater Pump Station Maintenance
Maintenance of the seven pump stations within the City storm drainage system is performed by Sewer
Utility staff since they have pump specialists whom perform all pump station maintenance. Sewer Utility
staff perform scheduled weekly and monthly maintenance inspections as described in the City of Auburn
Sewer Comprehensive Plan Update and summarized below:
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Weekly pump station maintenance activities include the following tasks:
• Perform a general visual inspection of grounds and pump station structure or vault
• Check equipment for abnormal vibrations
• Check lubrication of all pumping equipment
• Check and clean, as needed, seal filters
• Check ultrasonic level sensor
• Check pump run times
• Bleed lines of moisture
• Inspect control valves
• Check wet well for debris
• Manually run pump and observe wet well level
Monthly pump station maintenance activities include the following tasks:
• Inspect and test engine-generators
• Inspect pump station mechanical bypass pumping
• Flush sump pit and manually run sump pump
• Clean pump station interior and, at a minimum, wipe down control panels and pumps, and wash
down/disinfect floor
• Inspect fall restraint system
• Spot-check control system and telemetry alarms
6.3.3 Stormwater Pond Maintenance by King County
The City has contracted with King County to provide stormwater pond maintenance of two to five larger
stormwater ponds per year because the County can more efficiently provide this service using County-
owned equipment and property for disposal of sediment materials. The City seeks to phase out the use
of County resources by adding personnel and procuring additional equipment. Maintenance activities
and frequency of maintenance as discussed in Section 6.2.5 applies to those facilities maintained by
King County.
6.3.4 Stormfilter Maintenance
Stormfilters are designed to remove sediment, metals, and other stormwater pollutants from wet
weather runoff via filter cartridges. The City currently has eleven stormfilter cartridge facility locations.
The stormfilter vaults are inspected by city staff quarterly to identify conditions that require additional,
unscheduled maintenance. Such conditions could include excess sediment accumulation, damaged
piping, or vault and access cover damage. The stormfilters and vaults are maintained (cartridges
replaced) annually by a private contractor.
Non-Routine and Emergency Operations 6.4
The intent of the routine inspection and maintenance activities discussed in Sections 6.2 and 6.3 is to
minimize, through proactive management of the stormwater facilities, the potential for conditions that
could lead to emergencies. This section discusses unscheduled activities performed by Storm Drainage
Utility M&O staff, and describes a response plan for emergency conditions.
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6.4.1 Customer Service Requests
Customer service requests, typically related to a local drainage complaint, trigger creation of a work
order to inspect the affected area or stormwater facility and identify potential solutions. In some cases,
relatively simple solutions, such as removal of blockages, can alleviate the issue. However, other cases
require coordination with Engineering or other City departments. On average, City Storm Drainage Utility
staff respond to approximately two customer service/complaint-related work orders per week. The effort
required to resolve these complaints varies considerably.
Good record-keeping can help in complaint resolution by ensuring that all relevant data are gathered and
by serving as a reminder to resolve the complaint and notify the complainant. When a complaint is
received, the following information should be recorded to the extent possible:
• Name and contact information of the person making the complaint
• Brief description of the nature of the complaint
• Time and date the complaint was received
• Storm drainage staff assigned to respond
Following initial response, the complaint record should be updated to include the results of inspections
and corrective actions taken, if any. If the complaint cannot be resolved internally within the Storm
Drainage Utility, the complaint record should be forwarded to Engineering for further investigation.
Notification of any system investigation and/or action should be provided to the customer making the
complaint.
6.4.2 Emergency Response Program
The Storm Drainage Utility, in conjunction with the other utilities divisions, has prepared a Public Works
Emergency Response Manual as a guide on how to handle emergency situations. While the manual is by
no means all-inclusive for every type of disaster, it is a valuable tool for dealing with many of the
emergency situations that municipalities face. Copies of the Emergency Response Manual are available
at the M&O Building, at City Hall Annex with the City Engineer, and with the Valley Regional Fire Authority
(VRFA) Station.
The Emergency Response Manual is one element of the City’s overall Emergency Operations Plan. The
primary objectives of the Emergency Operations Plan are to ensure public safety, restore essential
services as quickly as possible, and provide assistance to other areas as required. There is also a master
response program for the entire City as documented in the City’s Emergency Management Plan (CEMP).
The material in the CEMP provides guidance for mitigation, preparedness, responsibilities, recovery
operations, training, and community education activities. Copies of the Emergency Operations Plan are
located in each City department, the M&O Building, and with the VRFA.
The utility has implemented a standby program whereby one on-call employee is designated to be the
first to receive after-hours emergency calls. Most storm drainage system problems that occur outside of
normal working hours are reported through the City’s 911 emergency response system or a non-
emergency response number. An emergency call-out list is provided to the emergency operator in order
to contact utility staff in case of an emergency. The primary responder to those after-hours calls is the
on-call employee. Storm Drainage Utility M&O staff have been trained to respond to system
emergencies. The contacted staff assesses the situation, contacts additional staff as necessary, and
then responds in accordance with established emergency response procedures.
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Data Collection and Record-Keeping 6.5
Data collection and record-keeping functions for the Storm Drainage Utility are performed using
Cartegraph, a Web-based commercial software package provided by Cartegraph Inc. Cartegraph
integrates GIS data with utility M&O records, providing managers with overview information about system
and operational performance and field crews with information related to the condition and failure history
of specific stormwater facilities. The City currently uses Cartegraph to plan field staff activities (work
orders), record results of both routine and non-routine maintenance, and compare actual maintenance
efforts to City goals. The City recently upgraded its Cartegraph system and plans to transition toward the
use of Cartegraph as an asset management tool, through which the City would optimize staffing and
capital resource planning.
In recent years, the City has made considerable progress in adding asset information to Cartegraph,
specifically GIS data, physical information related to size and material, and installation date. However, to
fully utilize the asset management function of Cartegraph, additional information related to risk, asset
criticality, and condition is also necessary. To assist the City’s transition to an asset management
program, the attributes listed below should be used within Cartegraph to define each of the City
stormwater assets (catch basin, pipe segment, stormwater pond, etc.).
Asset-Specific Attributes. The following asset-specific attributes are related to the asset and remain
relatively unchanged over time:
• Asset ID: The unique asset number that is used by all business systems to identify an asset.
• Location: Where the asset is located (GIS).
• In-service date: The date the asset was placed into service.
• Replacement cost: The cost to replace the asset and the year that the cost data were calculated.
• Useful life: The average life expectancy of the asset.
• Asset criticality: A value assigned to each asset that indicates how essential it is to maintaining a
defined LOS. Typically it is defined as a combined score based on the consequence of failure and
the likelihood of failure.
− Consequence of failure: The social and economic cost if the asset fails
− Likelihood of failure (condition): The estimated time until the asset fails, usually based on
condition
• Asset class: A group of assets that share the same characteristics (e.g., ponds, pipe segments).
Asset class is used to estimate replacement costs and useful life of groups of assets.
• Nameplate information and asset specifications: Important information that is used to uniquely
describe an asset such as the manufacturer name, type of asset, serial number, size, material, etc.
This information is used for asset identification, replacement, and repair.
Maintenance and Operation Attributes. The following M&O attributes are captured as part of the
operations, maintenance, and repair history associated with each asset:
• Asset ID: The unique asset number that is used by all business systems to identify an asset. Work
orders should be associated with one or more assets.
• Issue, cause, action: These codes are used to classify historical M&O activities associated with
corrective actions or unplanned maintenance.
− Issue: What is the problem observed in the field?
− Cause: What is the underlying cause of the problem?
− Action: What was done to address the cause?
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• Target hours and actual hours: Recording the estimated hours and actual hours to complete a work
order can help in determining efficiency, planning workloads, and assessing repair costs.
• Target start/stop date and actual dates: Recording the estimated and actual start and stop dates for
a work order can help in determining efficiency, planning workloads, and assessing repair costs.
• Work order costs: Work order costs include labor, parts, materials, and equipment, and should be
accurately recorded for each work order.
• Work order type: Work order types are used to group and compare different types of work activities.
Typical work order types include:
− Capital improvement: Work associated with a capital improvement project
− Corrective maintenance: Work associated with an unplanned repair
− Preventive maintenance: Work associated with a planned preventive maintenance activity
− Predictive maintenance: Work associated with predictive measures (usually for critical assets)
• Warranty information: Helps to determine assets that are under warranty and the warranty
maintenance requirements.
M&O Staffing Requirements 6.6
This section outlines existing and future staffing requirements for M&O staff.
6.6.1 Existing Staffing Requirements
Existing staffing requirements for M&O activities discussed in this chapter were compiled and evaluated
to determine the M&O staffing level needed to efficiently operate, maintain, repair, and collect and
report the information necessary to properly operate the storm drainage system. Table 6-2 evaluates the
estimated time to conduct storm drainage system M&O tasks in the manner currently performed.
Calculated days for each M&O activity are for a single person performed over an 8-hour “day.” Therefore,
an activity that is performed quarterly and that requires 4 hours and two M&O staff to complete would
result in an annual requirement of 4 days.
Table 6-2. Existing Storm Drainage System Maintenance and Staffing Requirements
Work activity FTE days
required annually Assumptions/City goal
Catch basin and manhole inspection, cleaning, and repair
Catch basin inspection 74 Inspect once every 2 years, total of 8,880 catch basins. Perform 60
inspections per day with one-person crew.
Manhole inspection 15 Inspect once every 4 years, total of 2,330 manholes. Perform 40
inspections per day with one-person crew.
Catch basin cleaning 222 One cleaning is required for every five inspections. Two-person crew, 1
hour each.
Manhole cleaning 29 One cleaning is required for every five inspections. Two-person crew, 1
hour each.
Catch basin/manhole repair 25 50 repairs per year. Two-person crew, 2 hours each.
Stormwater pipeline cleaning and CCTV
Pipeline cleaning 147 City goal is 110,000 ft per year (entire system in 10 years). Two-person
crew can clean 1,500 ft of pipe per day.
CCTV 220 City goal is 55,000 ft per year (entire system in 20 years). Two-person
crew can CCTV 500 ft of pipe per day.
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Table 6-2. Existing Storm Drainage System Maintenance and Staffing Requirements
Work activity FTE days
required annually Assumptions/City goal
Stormwater outfall inspection, cleaning, and maintenance
Inspection 49 City goal is four times per year (65 total outfalls). Two-person crew, 0.5
hour each.
Maintenance 16 City goal is one time per year (65 total outfalls). Two-person crew, 1
hour each.
Drainage ditch, stormwater pond, and swale inspection, maintenance, and restoration
Drainage ditch maintenance and
restoration
90 Six-person crew for 15 days (approximately 3 days per week for a
month in the summer).
Stormwater pond and swale inspection 113 City goal is twice per year for each of 225 ponds/swales. Two-person
crew, 1 hour each.
Stormwater pond and swale maintenance
and restoration
270 Six-person crew for 45 days (approximately 3 days per week for 3
months in the summer).
Culvert inspection and cleaning
Culvert inspection and cleaning 300 City goal of twice per year for each of 800 culverts. Two-person crew,
0.5 hour each.
Other stormwater M&O activities
General facility maintenance and other
field tasks
26 One day per week. Two-person crew, 2 hours each.
Customer service requests/complaints 26 Two requests per week.a Two-person crew, 1 hour each.
Data entry 130 20 hours per week total (8 people at 0.5 hour per day).
Subtotal 1,751
Total 1,926 Assumes 10% unquantified work
Total number of working days available
per FTE
221 365 minus weekends (104), holidays (12), vacation (15), sick (12),
and training (1).
Number of FTEs required 8.7 1,926 days required divided by 221 days per FTE year.
Current funded FTEs 8.7 8 FTE and 2 seasonal staff
Note: FTE days are defined as 8 hours.
a. Many customer service requests are related to maintenance needs for privately owned drainage systems.
Table 6-2 shows that the Storm Drainage Utility, including two seasonal staff, is appropriately staffed
with respect to meeting current City proactive goals for M&O activities, with the exception of drainage
ditch maintenance and restoration. Based upon discussions with City staff, they are unable to meet the
goal of performing ditch maintenance of all ditches within the system on a 20-year cycle with the
available M&O staff. In addition, the City would like to maintain all their stormwater ponds and no longer
rely on King County’s assistance with the larger ponds. Additional staffing needs required to more
consistently meet the current LOS goals, additional pond maintenance responsibilities, future regulatory
requirements, and anticipated system growth are discussed in Section 6.6.2.
6.6.2 Future Staffing Requirements and Equipment Needs
The M&O activities discussed in Section 6.2 and summarized in Table 6-2 are current efforts and do not
include additional activities that will be required as part of the revised NPDES Phase II Municipal
Stormwater Permit. Furthermore, additional staffing is required to more consistently meet LOS goals with
respect to stormwater pond and drainage ditch maintenance. Future staffing requirements are
summarized in the sections below and Table 6-3.
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6.6.2.1 Drainage Ditch and Stormwater Pond Maintenance and Restoration
The City intends to increase overall Storm Drainage Utility staffing in order to dedicate more staff to
drainage ditch maintenance and restoration during the summer months (see Table 6-3). In order to meet
the City’s goal to maintain all ditches within the system on a 20-year cycle, existing ditch maintenance
frequency will be increased by approximately 36 days (with a six-person crew), or 1 FTE per year.
As identified in Section 6.3.3, the City desires to phase out current King County maintenance of City
storm ponds. It is estimated that existing pond maintenance frequency will be increased by
approximately 55 days (with a six-person crew), or 1.5 FTE per year, to replace current King County
maintenance activities. A new excavator will also be necessary and is estimated to cost $180,000.
6.6.2.2 Other Stormwater M&O Activities
The City intends to hire one full-time staff member for Cartegraph maintenance tracking and reporting
functions. This staff member would support the City Storm Drainage, Sewer, and Water utilities and
would be a liaison with the City Information Services (IS) division.
Many of the new requirements of the NPDES Permit emphasize implementation of LID practices, such as
minimizing impervious surfaces, native vegetation loss, and stormwater runoff. A majority of new
development and redevelopment projects will be required to construct new types of onsite LID facilities,
which will need to be inspected and maintained to ensure proper function moving forward.
An estimate of FTE effort for LID facility inspection and maintenance based upon review of the new
NPDES Permit requirements was prepared separately from the Storm Drainage Utility planning process.
Through that effort it was estimated that 0.5 FTE of Storm Drainage Utility M&O staff will be required for
LID inspection and maintenance activities. Additional inspectors from Engineering would also be
dedicated to LID facilities and other requirements of the NPDES Permit.
Table 6-3. Future Storm Drainage System Maintenance and Staffing Requirements
Work activity FTE days
required annually Assumptions/City goal
Drainage ditch and stormwater pond maintenance and restoration
Drainage ditch maintenance and restoration 216 Six-person crew for 36 days during the summer months.
Stormwater pond restoration 330 Six-person crew for 55 days during the summer months.
Other stormwater M&O activities
Cartegraph tracking and reporting 74 Approximately 0.33 FTE (1 FTE shared with sewer and water utilities).
LID inspection and maintenance 104 One day per week. Two-person crew.
Total 724
Total number of working days available
per FTE 221 365 minus weekends (104), holidays (12), vacation (15), sick (12), and
training (1).
Number of FTEs required 3.3 724 days required divided by 221 days per FTE year.
6.6.2.2 Equipment Needs
New and updated Storm Drainage Utility equipment needs identified via consultation with City staff
include CCTV inspection equipment and an excavator for ditch and stormwater pond maintenance. New
equipment would increase M&O field staff efficiency and may reduce the need for additional staff.
Estimated costs, based on recent vendor quotes, for the equipment are summarized below.
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• CCTV inspection equipment: $250,000
• Excavator: $180,000
Potential Improvement Opportunities and Capital Needs 6.7
The Storm Drainage Utility has a positive track record for M&O, as evidenced by the limited need for non-
routine maintenance and few customer service complaints about the city’s drainage system. Routine
facility cleaning, regular inspections, experienced staff, and a well-planned storm drainage system
contribute to that success. However, the need to comply with the new NPDES Permit and the growing
backlog for drainage ditch and stormwater pond/swale maintenance should be addressed by the City by
adding to the current M&O staff. An additional 3.3 FTE (Table 6-3) are required to achieve current City
proactive M&O goals plus future NPDES permit LID requirements.
Based upon discussions with City staff and analysis of M&O activities discussed in this chapter, the
following improvement opportunities are available to the Storm Drainage Utility. These opportunities are
based on improving existing services, regulatory compliance, and improving work productivity:
• Obtain or upgrade the following utility equipment to improve M&O efficiency:
− CCTV inspection equipment
− Excavator for ditch and stormwater pond maintenance
• Continue to integrate asset management with existing utility management software (Cartegraph and
GIS).
− Continue to add GIS attributes to known Storm Drainage Utility assets.
− Perform and document condition assessments. Use defined criteria (such as leaks/cracks
observed, cleanliness, and other specific measures) and provide staff training to ensure
assessment consistency. Use National Association of Sewer Service Companies (NASSCO)
Pipeline Assessment and Certification Program (PACP) certified inspection programs to allow
integration of inspection results with Cartegraph.
− Over time, use results of condition assessments to move toward risk-based maintenance to best
utilize staff resources. For example, consistently high assessment scores would result in a lower
risk or need for maintenance, allowing M&O staff to be diverted to more essential activities.
− Over time, demonstrate (through maintenance records) that a subset of city catch basins do not
require inspection, cleaning, and maintenance every 2 years per the new NPDES Permit.
• All M&O repair projects (see Section 6.2.7) should be constructed to established City engineering
standards. It is recommended that the City develop a more formal procedure for tracking M&O repair
projects to ensure that as-built and GIS records are updated when repairs are completed.
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Chapter 7
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 longer-term capital
planning goals (see Chapter 8). This comprehensive plan contains time frames that 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. The framework does
not represent actual commitments by the City of Auburn, which may depend on available funding
resources.
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 Storm Drainage 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 and by working collaboratively with City staff. This focused and collaborative
approach was based on the practical consideration that the City can implement only 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 Storm Drainage Utility to meet LOS goals. The following basic steps are
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 development.
• Modeling was completed for the historical 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 assess the
extent and severity of the drainage problem. Results from the design event were used to size
infrastructure improvements to mitigate drainage problems.
• Hydraulic modeling was completed using PCSWMM, a software package that uses GIS technology to
import and export data, allowing a seamless transition between the system inventories and
modeling input files. For smaller basins for which a PCSWMM model did not exist or was not created,
Manning’s n equations were used to determine pipe sizing.
• Recommendations were developed for flow and water level monitoring in the vicinity for some of the
proposed projects or other locations where future modeling may be warranted.
• Members of the City’s staff have a thorough understanding of the storm drainage system and
firsthand experience with existing drainage problems. The project team worked with City staff to
identify the most viable mitigation alternative.
• Once the projects were defined, the project team developed concept-level cost estimates.
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An overview of project locations is shown in Figure 7-1. Section 7.1 describes a tiered method for
establishing project priorities. Section 7.2 presents detailed descriptions of new proposed projects.
Section 7.3 describes programmatic drainage projects. Section 7.4 examines the need for repair and
replacement of existing pipes.
Project Prioritization 7.1
Storm Drainage Utility staff prioritized capital improvement projects by grouping them into one of three
tiers. Projects in the top tier, or highest priority, are classified as tier 1; projects with medium priority 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 be larger 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, or other utility or
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- and 20-year CIPs (see Chapter 8).
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LEGEND
!(Project Location
Roadway
Watercourse
Water Body
Wetland
Auburn City Boundary
¯0 5,000 10,0002,500
Feet
COMPREHENSIVE STORM DRAINAGE PLAN
April 2015 Figure 7-1Project LocationsStormwater Drainage UtilityCapital Improvements Program
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ID Project Name 1 West Main Street Pump Station Upgrade 2 37th and I Streets NW Storm Improvements 3 Hillside Drainage Assessment (*see Figure 7-4 for project locations) 4A 30th Street NE Are Flooding, Phase 2 4B 30th Street NE Are Flooding, Phase 3 5A West Hills Drainage Improvements near S 330th St. and 46th Pl. S 5B West Hills Drainage Improvements at S 314th St. and 54th Ave. S 6 North Airport Area Improvements 7 D St. SE Storm Improvements 8 23rd St. SE Drainage Improvements 9 Comprehensive Storm Drainage Plan update 10 Composting Facility (location to be determined)* 11 Storm Drainage Infrastructure Repair & Replacement* 12 Street Utility Improvements* *Project not mapped; multiple locations or location to be determined
Chapter 7 Comprehensive Storm Drainage Plan
7-4
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Proposed Drainage Projects 7.2
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 and design. Project
descriptions are organized into summaries containing the following information:
• Project number: CIP numbers were generally assigned by priority.
• Project name: A short, descriptive name was assigned to each project.
• Location: A simple description of the project location, such as the cross streets, is provided.
• 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 8.
• Problem summary: 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. 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 C.
• Description: A description of the proposed project is provided, including major project elements and
sizes.
• LOS goal(s) addressed: The LOS goal(s) addressed by the project is provided.
• Recommended predesign refinement: In some cases, pre-project data collection and monitoring is
proposed.
• Recommended post-construction monitoring: In some cases, post-project monitoring is proposed.
• Planning-level cost estimate: A list of estimated costs is provided including construction costs,
engineering and administrative costs, taxes, and contingency costs. The estimate was developed
based on the conceptual design, preliminary quantity take-offs, and estimated unit costs. Estimated
unit costs were based on the City of Seattle Unit Cost Report (SPU, 2012), WSDOT Unit Bid Tab for
the Northwest region (2012–2014), King County’s Tabula conveyance system cost estimating
software, vendor quotes, and escalated project costs from recent projects with similar components.
• Project map: A figure showing the conceptual design and location of project elements is provided.
Proposed project summaries and maps are presented on the following pages.
Comprehensive Storm Drainage Plan Chapter 7
7-5
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 1
Project name West Main Street Pump Station Upgrade
Location South of West Main Street east of the SR 167 overpass
Priority 1
Schedule Begin construction 2016
Problem summary
The dead-end portion of Old West Main Street near SR 167 has a history of observed flooding. The City
installed a pump station to dewater the gravity pipe, flowing on the south side of Old West Main Street, in
an effort to protect local businesses from flooding. Since its installation in 2008, the pump station has
eliminated flooding at the observed location. The pump station, however, does not meet the City’s LOS
guidelines regarding pump redundancy, and modeling indicates that the pump station does not have
capacity to convey the 25-year flow rate.
The City’s gravity pipe on the north side of Old West Main Street experiences flooding, at one inlet,
approximately once per year. Portions of this gravity pipe are now inundated because of high water
elevations associated with the water surface elevation in Mill Creek, which is downstream.
The pump station and gravity pipe discharge to a WSDOT ditch along the east side of SR 167. The ditch
flows north to a WSDOT 24-inch-diameter culvert under West Main Street. Approximately 1,150 feet north
of West Main Street, the WSDOT ditch discharges to Mill Creek via a 24-inch-diameter culvert under SR
167.
During a field visit on April 30, 2014, approximately 5 feet of standing water was observed in the WSDOT
system as well as in portions of the City’s gravity system. Sediment and vegetation accumulation in the
WSDOT downstream conveyance (north of West Main Street) prevent the City’s system from draining. Also,
when Mill Creek’s water surface elevation is high, it backflows into the WSDOT ditch and inundates the
adjacent wetland area north of West Main Street. WSDOT has recently completed cleaning of the ditch
segment. The impact of this maintenance work on water elevations in the WSDOT system and in the City’s
gravity system should be evaluated to determine the timing for construction.
Modeling results show that some sections of the gravity portion of the system are capacity-limited (for the
25-year flow rate), primarily along West Main Street near Clay Street.
Description
This project consists of building a new pump station sized to convey the peak 25-year flow rate with
multiple pumps to meet the pump redundancy LOS (Figure 7-2). The new pump station would convey all
flows from the gravity pipe on the north and south sides of Old West Main Street. The pump station wet
well should be low enough to adequately drain the lowest catch basin in the basin.
The force main from the new pump station would be routed to the City ditch on the north side of West Main
Street. The 30-inch-diameter force main will be constructed within or near the alignment of the existing
culvert with trenchless construction technologies (e.g. pipe-bursting). The force main will discharge to a
riprap rock splash pad constructed in the ditch at the current culvert discharge location.
A backflow preventer should be installed on the 24-inch-diameter WSDOT culvert under West Main Street
to prevent backflow from the north side of the overpass to the south. A backflow preventer may need to be
installed at the 12-inch-diameter culvert crossing at West Main Street, near Lund Road SW, to prevent flow
from the north side of West Main Street to the south side. Post-project monitoring should be conducted to
confirm that the pump station discharges are not causing backups in the City’s ditch, warranting a
backflow preventer at this location.
Model calibration was limited to pump station supervisory control and data acquisition (SCADA) data from
October 2013 through April 2014. Although the existing pump station tributary area is approximately 15%
of the total basin area, the observed flow characteristics from the pump station were used to characterize
flow from the entire basin. Because of the limited calibration data, the proposed pump station should
include SCADA/telemetry capabilities to provide additional flow information, and allow for additional
capacity, if necessary.
Key components include:
• Pump station (estimated capacity 25 cubic feet per second [cfs] with multiple pumps) with wet well and
SCADA/telemetry
• Gravity system conveyance to new pump station:
− 150 feet of 12-inch-diameter pipe
− 113 feet of 24-inch-diameter pipe
• 200 feet of 30-inch-diameter force main installed with trenchless construction technologies
• Riprap rock splash pad at existing culvert outfall in ditch
Chapter 7 Comprehensive Storm Drainage Plan
7-6
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 1
• Backflow preventers to prevent stormwater recirculation to WSDOT ditch or the City’s system (if
necessary)
Recommended
predesign
requirement
• Evaluate the impact of the WSDOT maintenance work on water elevations in the WSDOT system and
the City’s gravity system, to determine construction timing and future needs for ditch cleaning.
• Coordinate with WSDOT on installation of the backflow preventer on the WSDOT culvert.
Recommended post-
construction
monitoring
Conduct periodic site inspections during storm events to confirm that the pump station discharges are not
causing backups in the City’s ditch to the 12-inch-diameter culvert crossing West Main Street near Lund
Road SW. If backups do occur, a backflow preventer on the north end of the 12-inch-diameter culvert may
be warranted.
LOS goal(s)
addressed
• Flooding disruption that inundates the roadways to an impassable level no more than once every
25 years. (LOS Goal 4)
• Flooding (surface water from ROW runoff entering premises and damaging building structures) no more
than once every 50 years. (LOS Goal 5)
• 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 15)
Cost estimate
Stormwater pump station with SCADA/telemetry: 25 cfs pump station located in Old
West Main Street ......................................................................................................... $750,000
Gravity piping: 150 feet of 12-inch-diameter pipe and 113 feet of 24-inch-diameter
pipe from existing manholes to new pump station .................................................... $85,000
Force main: construct 200 feet of 30-inch-diameter force main below underpass
(from south to north side through existing culvert) using trenchless technology,
abandon 18-inch-diameter culvert, and install riprap rock splash pad at existing
culvert outfall in ditch outfall ......................................................................................
$257,000
Ancillary improvements: decommission existing pump station; install backflow
preventer on WSDOT culvert ....................................................................................... $40,000
Wetland permitting and mitigation (20% of construction subtotal) .......................... $227,000
Subtotal line-item costs ............................................................................................... $1,359,000
Contractor overhead, profit, and mobilization (18% of subtotal of line-item costs) . $245,000
Construction contingency (30% of all above construction costs) ............................. $481,000
Washington State and King County sales tax (9.5% of all above construction costs)
...................................................................................................................................... $198,000
Subtotal construction costs ........................................................................................ $2,283,000
Administration, engineering design, and permitting (30% of construction costs) ... $685,000
CIP 1 project cost $2,968,000
Install backflow preventer, if necessary
Install pump station
Install 200 lf 30-inch-diameter force main
within existing culvert alignment using
trechless construction techniques
Decommission existing
pump station
Install 150 lf 12-inch-diameter
drainage pipe
Install riprap rock splash pad
Install 113 lf 24-inch-diameter
drainage pipe
Mi
l
l
C
r
e
e
k
Abandon existing gravity pipe
Install backflow preventer
OLD W MAIN ST
wetlands
W MAIN ST
SR
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LEGEND
Pump Station
%,Proposed Facility
Proposed Force Main
Proposed Drainage Pipe
!(Storm Node
Storm Channel
Storm Pipe
Storm Culvert
¯0 400 800200
Feet
COMPREHENSIVE STORM DRAINAGE PLAN
April 2015 Figure 7-2Project 1: West Main Street Pump Station Upgrade
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Comprehensive Storm Drainage Plan Chapter 7
7-9
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 2
Project name 37th and I Streets NW Storm Improvements
Location Intersection of 37th Street NW and I Street NW; Interurban Trail approximately 300 feet east
Priority 1
Schedule Begin construction 2016
Problem summary
Recurring flooding in the vicinity of 37th Street NW and I Street NW causes several nuisance problems
including slow or impeded traffic on 37th Street NW, driveway damage and/or impeded access to the
nearby power substation, and impeded pedestrian and bicycle access on the Interurban Trail south of 37th
Street NW (east of the substation). Flooding problems occur relatively frequently and can result from large
storm events as well as prolonged wet periods following storm events. Observations and anecdotal
information suggest that floodwaters originate from Mill Creek and/or drainage system backups caused by
high water levels in Mill Creek, particularly at the north side of 29th Street NW. Although high water levels
in Mill Creek at 37th Street could also be a source of flooding and/or reduce the conveyance capacity of
the drainage ditch along 37th Street, it has been observed that there is typically a positive flow gradient
leading from the flooded areas back toward Mill Creek.
There appear to be at least two flow paths between overflows at 29th Street NW and flooding at 37th
Street NW:
1. Backflow along 29th Street NW is diverted into a remnant channel of Mill Creek that flows north
toward the power substation. The remnant channel appears to be blocked by the substation and
does not have a clear path back to the main channel. It appears that, when discharges in the
remnant channel are high, at least a portion of the flow goes northeast and becomes impounded on
the east side of the power substation driveway.
2. Backflow along 29th Street NW can extend as far as the Interurban Trail crossing, causing backflow
through the culverts into the area between the trail embankment and the railroad embankment.
Water can then flow north along the embankments until it ponds on the south side of 37th Street
NW. When the ponding gets high enough, water floods over the Interurban Trail and into the
impounded water on the east side of the power substation driveway. In 2013, a small berm was
constructed between the trail embankment and the railroad embankment to try to prevent water
from flowing north; however, it is not known whether this modification sufficiently addressed the
problem.
The impounded water on the east side of the power substation driveway can lead to flooding when water
surface elevations rise to roughly 51 feet elevation (NAVD88). Specifically, the substation driveway is
overtopped and areas of 37th Street NW are flooded because of backflow through an existing storm drain
catch basin, and perhaps also because of direct flow over the sidewalk and curb.
City maintenance crews completed a small works project in 2012 to try to mitigate the flooding. Two 8-
inch-diameter ductile iron culverts were installed under the power substation driveway near 37th Street
NW at a higher invert elevation than the existing 12-inch-diameter culvert. The intention was to provide
additional conveyance capacity to drain the water that ponds on the east side of the driveway back to Mill
Creek. However, reports from the City suggest that this modification has not been sufficient to eliminate
the flooding problems.
Description
This project will increase the conveyance capacity of the drainage along 37th Street NW by replacing the
existing culverts under the power substation driveway and installing a new culvert under the Interurban
Trail (Figure 7-3). A drainage ditch should be constructed to convey water from the Interurban Trail culvert
to the existing ditch along the south side of 37th Street NW. The trapezoidal ditch should have a bottom
width of 4 feet, 3:1 side slopes, and a depth of 2 feet. In addition, the existing ditch along 37th Street NW
should be cleaned out (remove sediment, vegetation, obstructions, and accumulated debris) to maximize
conveyance capacity and minimize the tail water effects on culvert outlets.
The magnitude and frequency of flows emanating from Mill Creek backflows are difficult to quantify without
a hydraulic study of the Mill Creek main channel, as well as a detailed survey of the drainage flow paths
leading to the flooded areas at 37th Street NW. Therefore, the proposed new culverts were not sized to
pass a specific design discharge. Alternatively, a hydraulic analysis of the ditch and culvert system was
performed to examine the potential for reducing water surface elevations by installing larger culverts.
The project includes two new 3-foot (span) by 2-foot (rise) reinforced concrete box culverts: the first would
be installed under the power substation driveway at an invert elevation of approximately 46.5 feet
(NAVD88), and a second would be installed under the Interurban Trail embedded by approximately 1 foot
because of likely cover limitations. Installation of these culverts would reduce upstream water surface
elevations by roughly 2 feet during high flow conditions that currently result in flooding at approximately 51
Chapter 7 Comprehensive Storm Drainage Plan
7-10
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 2
feet NAVD88.
The proposed culverts are the smallest standard box culvert. If additional data are collected (see predesign
recommended predesign refinements), culvert sizes could be refined, and a larger size could be installed if
warranted.
Recommended
predesign
refinements
• Perform additional site reconnaissance and survey, including a stream walk during high flow conditions
(to estimate high water elevations) and confirm flow paths assumptions
• Conduct a detailed topographic survey of the drainage system including the ditch, road and trail
crossings, and nearby flooded areas; in addition, conduct a ground survey of key structures such as
culvert invert elevations and dimensions
• Conduct a revised hydraulic analysis of the drainage system using new survey data, high water mark
estimates, and confirmed flow paths; refine culvert sizing given needed conveyance capacity, spatial
constraints, and project costs
LOS goal(s)
addressed
Flooding disruption that inundates the roadways to an impassable level no more than once every 25 years
(LOS Goal 4)
Cost estimate
Interurban Trail culvert: construct 60 feet of 3-by-2-foot precast concrete box culvert including
inlet and outlet headwalls and riprap rock splash pad at outlet…. ........................................... $40,000
Power substation driveway culvert: construct 60 feet of 3-by-2-foot precast concrete box
culvert including inlet and outlet headwalls and riprap rock splash pad at outlet, and drainage
bypass .........................................................................................................................................
$50,000
Ancillary improvements: construct 50-foot-long ditch to connect Interurban Trail culvert to
roadside ditch; clean 1,000-foot-long existing ditches along south side of 37th Street NW .. $33,000
Wetland permitting and mitigation ............................................................................................. $22,000
Subtotal line-item costs ............................................................................................................... $145,000
Contractor overhead, profit, and mobilization (18% of subtotal of line-item costs) ................. $26,000
Construction contingency (20% of all above construction costs) ............................................. $34,000
Washington State and King County sales tax (9.5% of all above construction costs) ............. $19,000
Subtotal construction costs ........................................................................................................ $224,000
Administration, engineering design, and permitting (30% of construction costs) ................... $67,000
CIP 2 project cost $291,000
INTERURBAN
TRAIL
POWER
SUBSTATION
M
i
l
l
C
reek
High water levels cause
backflow into the drainage
system, including diverted
flow into the remnant
Mill Creek channel
Water continues
to flow north along
remnant channel
Remnant channel
terminates but does
not have clear path
back to main channel;
some water appears to
flow to the east side of
the power substation
Backflow from Mill
Creek could result
in surcharging at
inlet to Interurban
Trail culverts; berm
constructed in 2013
to prevent water
from flowing north
Flooding over
Interurban Trail
Flooding of 37th
Street NWFlooding over
driveway
Remove Remove sediment, debris, & vegetation
from 1,000 lf of drainage ditch
SR
1
6
7
37TH ST NW
29TH ST NW
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¯
COMPREHENSIVE STORM DRAINAGE PLAN
April 2015 Figure 7-3Project 2: 37th and I Streets NWStorm Improvements
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Replace existing culvert with
30-inch x 24-inch reinforced
concrete box culvert
37TH ST NW INSET A
LEGEND
!(Storm Node
Storm Pipe
Storm Channel
Storm Culvert
Proposed Culvert
Proposed Ditch
0 400 800200
Feet
1 inch = 400 feet
!(
Install new 30-inch x 24-inch
concrete box culvert
Construct new drainage
ditch and connect to
existing roadway ditch
INSET B
BA
Comprehensive Storm Drainage Plan Chapter 7
7-13
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 3 (Phases 1 and 2 described jointly)
Project name Hillside Drainage Assessment
Location Hillsides throughout the city
Priority 1
Schedule Begin assessment 2016 (Phase 1) and 2017 (Phase 2)
Problem summary
The existing drainage system includes pipes that discharge over hillsides. While a preliminary inventory
and mapping of locations has been completed, field-locating and detailed inspection is warranted to
define deficiencies.
Description
This project would entail compiling and reviewing existing documentation (GIS, record drawings,
Cartegraph) on piped stormwater discharges to hillsides throughout the city (Figure 7-4).
Some pipes may be located on private property or may be accessed only through private property. The
project would include reviewing property legal descriptions to determine where easements may be
lacking and working with property owners to obtain temporary access for the CIP work.
Field visits would be conducted for all identified pipes. Field crews would locate, perform a detailed
inspection, and define outfall deficiencies (e.g., poor access, damaged pipe, insufficient slope protection
at the outfall, structural support of pipe). Special equipment (e.g., pipe video cameras) may be necessary
based on site conditions (e.g., heavy vegetation, steep slope).
Last, the field visit and the necessary actions would be documented. Necessary actions could include:
• Obtaining permanent easements for ongoing inspection and maintenance
• Constructing an access road or trail
• Pipe replacement or repair
• Repair or replacement of slope protection
• Engineering services for pipe or slope protection replacement
This project would be completed in a phased approach. Phase I would consist of completing the
assessment for all non-high-density polyethylene (HDPE) pipes, as there is less information about these
pipes and they tend to be older. Phase 2 would consist of completing the assessment for all HDPE pipes.
HPDE pipes tend to be newer, have more information, and are easier to locate as many are aboveground
installations. The cost estimate includes a placeholder for implementing drainage assessment
recommendations. Actual implementation costs will be estimated after the assessment is complete.
LOS goal(s)
addressed
No erosion or landslides resulting from public drainage infrastructure construction, operation, or
maintenance. No direct stormwater discharge will be permitted on steep slopes. (LOS Goal 6)
Recommended
predesign
refinements
This project is for an assessment that will help define the predesign requirements.
Cost estimate
Collect and review available documentation on pipes (28 locations) ..................................... $10,000
Coordinate access with private landowners (18 locations) ...................................................... $4,000
Conduct field visit and assess the pipe(s) and outfall, Phase 1: Non-HDPE Pipes
Medium vegetation on a medium slope (12 locations) ..................................................... $21,000
Medium to dense vegetation on a steep slope (2 locations) ............................................. $5,000
Conduct field visit and assess the pipe(s) and outfall, Phase 2: HPDE Pipes
Medium to dense vegetation on a mild slope (4 locations) ............................................... $7,000
Medium to dense vegetation on a medium slope (8 locations) ........................................ $14,000
Medium vegetation on a steep slope (2 locations) ............................................................ $6,000
Document results of assessment .............................................................................................. $14,000
Implement drainage assessment recommendations $88,000
Subtotal line-item costs .............................................................................................................. $169,000
Construction contingency (20% of all above construction costs)............................................. $34,000
Washington State and King County sales tax (9.5% of all above construction costs) ............ $19,000
Subtotal construction costs ....................................................................................................... $222,000
Chapter 7 Comprehensive Storm Drainage Plan
7-14
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 3 (Phases 1 and 2 described jointly)
Administration, engineering design, and permitting (30% of construction costs) .................. $67,000
CIP 3 project cost $289,000
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GreenRiver
Academy
Johansen
Mill Pond
River Rim
West Beverly
Cobble Creek
Olsen Canyon
Forest Ridge
Pacific Ridge
Vista Heights
Kendall Ridge
Leah Hill Road
Jovita Heights Auburn Way S #1
Amberview Apts.
Auburn Way S #2
Scenic Drive #1
East View Vista
High Crest Drive
Rainier Ridge #1
Rainier Ridge #2
Lakeland Hills #2
Scenic Drive #2-5
Lakeland Hills #1
East Hill Estates
Hidden Valley Vista
Lake Tapps Parkway East #1
Lake Tapps Parkway East #2
LEGEND
Auburn City Boundary
!HDPE Pipe
!Other Pipe
¯0 5,000 10,0002,500
Feet
COMPREHENSIVE STORM DRAINAGE PLAN
April 2015 Figure 7-4Project 3: Hillside Drainage Assessment
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Comprehensive Storm Drainage Plan Chapter 7
7-17
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 4A and 4B (described jointly)
Project name 30th Street NE Area Flooding, Phases 2 and 3
Location East of I Street NE between 32nd Street NE and 35th Street NE, and at C Street NE between 30th Street NE
and 37th Street NE
Priority 2 (4A) and 3 (4B)
Schedule Phase construction with Project 4A (Phase 2) in 2017 and Project 4B (Phase 3) in 2019
Problem
summary
The north-central area of Auburn has a history of surface flooding with street flooding occurring once every few
years.
The residential development east of I Street NE between 32nd Street NE and 35th Street NE discharges flows
into a City-owned infiltration area. The infiltration area commonly experiences prolonged periods of standing
water due to high groundwater from extended high flows in the Green River, which is adjacent to the infiltration
area. The drainage system on I Street NE currently lacks infrastructure to collect and convey stormwater away
from the infiltration area, as well as residential roadways and parking area. Ponding occurs within the parking
areas of the developments and presents a nuisance and potential hazard to local residents.
The December 3, 2007, storm (approximately a 50-year storm) produced extensive flooding along C Street NE
northward toward 37th Street NE, which required sandbagging to protect local businesses. Deposition of
sediment within Mill Creek has raised the water levels within the creek and diminished the capacity of the
gravity system in C Street NE and downstream in 37th Street NE. In addition to the influence of Mill Creek,
modeling efforts demonstrate that the system’s capacity is limited by low pipe gradient and shallow inverts
and that flooding would continue even with sediment removal within Mill Creek.
Although the two problems are not hydraulically connected, the proposed projects are described jointly as they
will connect the problem areas to the 30th Street NE system.
Description
These projects are Phases 2 and 3 of a three-phased capital improvement project (Relieve 30th Street NE
Area Flooding) from the 2009 Comprehensive Stormwater Drainage Plan. The goal of the 2011 capital
improvement project was to increase the capacity of the 30th Street NE system to reduce flooding along 30th
Street NE and to provide capacity to connect other flooding drainage systems (C Street NE and I Street NE).
The implementation of this capital improvement project is occurring in phases, as funding, staff availability,
and priorities allow. The first phase (30th Street NE Area Flooding, Phase 1) is scheduled for construction in
2015/2016. The subsequent phases, referred to as Projects 4A and 4B in this Drainage Plan, are scheduled
for construction in 2017 and 2019, respectively.
Project 4A would address the flooding adjacent to I Street NE (Figure 7-5). This project would locate a storm
drain line to capture stormwater from the two residential developments currently discharging stormwater to
the City’s infiltration area. In addition, this project would construct a new storm drain within I Street NE
southward to connect into the 42-inch-diameter storm drain (which will be constructed as part of the 30th
Street NE Area Flooding project, Phase I, from the 2009 Plan) near the intersection at I Street NE and 30th
Street NE. The 42-inch-diameter line will have sufficient available capacity to convey the I Street NE flows. Key
components of Project 4A include:
• 1,850 feet of 15-inch-diameter gravity storm drain
• Catch basin and incidental grading to collect stormwater at the upstream end of the system
Project 4B would address flooding along C Street NE (Figure 7-6). Currently stormwater flows along C Street NE
are conveyed north to the 37th Street NE storm conveyance line and discharge to Mill Creek. This project
would reduce flooding in C Street NE by increasing capacity in the line by lowering inverts and upsizing the
pipe diameter of a portion of the system, and by redirecting the high wet weather flows southward to the 42-
inch-diameter storm drain (to be completed in 2016) in 30th Street NE. Flows are redirected with a diversion
to a new pump station and force main connection to 30th Street NE. Key components of Project 4B include:
• Backflow preventer to isolate the C Street NE system from Mill Creek backwater
• Diversion structure in C Street NE for pump station
• Pump station (estimated capacity of 5 to 7 cfs)
• 850 feet of 24-inch-diameter drainage pipe (replace existing pipe with larger and steeper pipe)
• 1,730 feet of 15-inch-diameter force main
Upon completion, City staff should consider lowering the level settings for Brannan Park pumps 4 and 5,
because the hydraulic improvements associated with this project 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 4)
Chapter 7 Comprehensive Storm Drainage Plan
7-18
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 4A and 4B (described jointly)
Flooding causing property damage no more than once every 50 years (LOS Goal 5)
Project 4B
recommended
predesign
refinements
Pump station design capacity and control strategy should consider the potential impacts to the downstream
conveyance systems along 30th Street NE and the airport. Pump station real time control at the airport
stormwater ponds could be included, where the pond outflow is restricted when the pump station is operating.
Cost estimate
Project 4A
Gravity storm drain: install 1,850 feet of 15-inch-diameter pipe (along I Street NE to 30th
Street NE storm drain) ............................................................................................................ $481,000
Subtotal line-item costs .......................................................................................................... $481,000
Contractor overhead, profit, and mobilization (18% of subtotal of line-item costs) ............ $87,000
Construction contingency (20% of all above construction costs) ........................................ $114,000
Washington State and King County sales tax (9.5% of all above construction costs) ........ $65,000
Subtotal construction costs ................................................................................................... $747,000
Administration, engineering design, and permitting (20% of construction costs) .............. $145,000
CIP 4A (Phase 2) project cost $896,000
Cost estimate
Project 4B
Flow diversion structure ......................................................................................................... $4,000
Install backflow preventer for 24-inch-diameter pipe ........................................................... $10,000
Gravity line: replace 850 feet of pipe with 24-inch-diameter pipe at steeper grade .......... $289,000
Stormwater pump station: 5 to 7 cfs pump station located C Street NE to the south of 37th
Street NE ................................................................................................................................. $300,000
Force main: install 1,730 feet of 15-inch-diameter pipe (connect to 30th Street NE storm
drain) ....................................................................................................................................... $450,000
Subtotal line-item costs .......................................................................................................... $1,053,000
Contractor overhead, profit, and mobilization (18% of subtotal of line-item costs) ............ $190,000
Construction contingency (20% of all above construction costs) ........................................ $249,000
Washington State and King County sales tax (9.5% of all above construction costs) ........ $142,000
Subtotal construction costs ................................................................................................... $1,634,000
Administration, engineering design, and permitting (30% of construction costs) ............. $490,000
CIP 4B (Phase 3) project cost $2,124,000
Total CIP 4A and 4B project cost $3,020,000
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Install 1,850 lf 15-inch drainage pipe
I
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30TH ST NE
28TH ST NE
31ST ST NE
32ND ST NE
32ND PL NE
L
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32ND ST NE
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LEGEND
Pump Station
!(Storm Node
Storm Pipe
Storm Channel
Storm Culvert
Storm Pond
Proposed Drainage Pipe
¯0 300 600150
Feet
COMPREHENSIVE STORM DRAINAGE PLAN
April 2015 Figure 7-5Project 4A: 30th Street NE Area Flooding, Phase 2
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AU
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30TH ST NE30TH ST NW
35TH ST NE
LEGEND
!(Storm Node
Storm Pipe
Storm Channel
Storm Culvert
Storm Pond
%,Proposed Facility
Proposed Force Main
Proposed Drainage Pipe
¯0 300 600150
Feet
COMPREHENSIVE STORM DRAINAGE PLAN
April 2015 Figure 7-6Project 4B: 30th Street NE Area Flooding, Phase 3
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New pump station in C St. NE
New 1,730 lf force main in C S.t NE
Force main connection to
30th St. NE drainage pipe
Replace existing gravity pipe
with larger, steeper pipe
Install backflow preventer
Flow diversion structure
Comprehensive Storm Drainage Plan Chapter 7
7-23
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 5A
Project name West Hills Drainage Improvements at S 330th St. and 46th Pl. S
Location Southwest corner of S 330th Street and 46th Place S
Priority 2
Schedule Begin construction 2016
Problem summary
Flooding has been reported along the S 330th Street roadway. Surface water from upstream of the flooding
location including the City’s ROW is conveyed through a ditch and pipes, located on private property
adjacent to the problem area. The pipes located on private property had previously been conveyed in a
ditch. In an attempt to reclaim the front yard, a previous property owner filled the ditch with two parallel
pipes. The existing system discharges to a ravine outfall south of S 330th Street. Flows from the ravine
eventually discharge to Mill Creek.
Description
This project would re-route flows upstream of the private property including those flows from the City ROW
into a new piped system. The proposed 24-inch-diameter pipe would be aligned in the 46th Place S and S
330th Street ROWs. The project includes three connection structures: a tie-in to the existing system at the
upstream end, a manhole where the pipe alignment turns onto S 330th Street, and a manhole where the
pipe alignment turns toward the outfall. This manhole also connects the adjacent private system to the new
pipe system.
The project results in a single 24-inch-diameter pipe discharging to the existing outfall. The east side of the
existing outfall is a brick retaining wall and will be rebuilt as part of this project. The outfall will also be
reinforced with riprap.
LOS goal(s)
addressed Maintain or seek access to City-owned facilities for necessary maintenance and operation. (LOS Goal 13)
Recommended
predesign
refinements
Flows to the project area were estimated using WWHM12, assuming existing conditions for the current
subbasin contributing area. Prior to detailed design, the basin contributing area should be refined by
accounting for any changes due to new or re-development.
Obtain easement from one property owner.
Cost estimate
Extend existing (12-inch-diameter) culvert 18 feet to new tie-in connection .......................... $4,000
Gravity storm drain: install 220 feet of 24-inch-diameter pipe in ROW under power line ..... $70,000
Gravity storm drain: install 105 feet of 24-inch-diameter pipe in ROW .................................. $34,000
Gravity storm drain: install 22 feet of 24-inch-diameter pipe in easement ............................ $8,000
Gravity storm drain: install 34 feet of 12-inch-diameter pipe in easement from existing catch
basin to new manhole ................................................................................................................ $7,000
Install three connecting structures ............................................................................................ $10,000
Rebuild outfall and reinforce discharge area ............................................................................ $5,000
Obtain easement ........................................................................................................................ $20,000
Subtotal line-item costs .............................................................................................................. $158,000
Contractor overhead, profit, and mobilization (18% of subtotal of line-item costs) ............... $28,000
Construction contingency (20% of all above construction costs) ............................................ $37,000
Washington State and King County sales tax (9.5% of all above construction costs) ............ $21,000
Subtotal construction costs ....................................................................................................... $244,000
Administration, engineering design, and permitting (30% of construction costs) .................. $73,000
CIP 5A project cost $317,000
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Parcels
Proposed Easement
%,Proposed Facility
Proposed Drainage Pipe
¯0 100 20050
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COMPREHENSIVE STORM DRAINAGE PLAN
April 2015 Figure 7-7 Project 5A: West Hills Drainage Improvements S 330th St. and 46th Pl. S
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S 330th St
Connect existing 18-inch pipe
to new manhole
Install 105 lf
24-inch pipe
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Inset
Connect existing catch basin
to new manhole with
34 lf 12-inch pipe
Rebuild existing outfall
and reinforce with riprap
Obtain easement
Replace existing 18-inch pipe
with 22 lf 24-inch pipe
Comprehensive Storm Drainage Plan Chapter 7
7-27
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 5B (Phases 1 and 2 described jointly)
Project name West Hills Drainage Improvements near S 314th St. and 54th Ave. S
Location S 314th Street and 54th Avenue S
Priority 2
Schedule Begin construction 2018
Problem summary
A City-owned pipe daylights to the back yard of a residential parcel on S 314th St and discharges runoff
onto the northern adjacent property. Although the northern property reports water under the home, there is
no record of nuisance ponding or flooding. The discharging pipe is the outfall for a 25-acre subbasin roughly
spanning S 316th and 314th streets and 52nd and 55th avenues S. The residential area surrounding the
25-acre subbasin (to the west and north) is served by a grass ditch and culvert system that conveys flows to
a culvert crossing at S 312th Street. The discharge continues through a series of open channels and
culverts and eventually drains to Mill Creek.
Description
Phase 1: The project’s first phase is to implement LID BMPs in the ROW to provide infiltration and reduce
flows into the existing and proposed piped system (Figure 7-8. The ROW areas in this neighborhood are
good candidates for roadside bioretention cells over gravel trench based on gentle consistent slope of the
existing grass-lined ditches, existing infall and outfall infrastructure, and lack of street/shoulder parking.
The gravel trench provides storage and detention time for infiltration in areas of low infiltration rates.
Phase 2: Given that LID BMPs do not significantly reduce high flows, the project also includes installing 385
feet of 18-inch-diameter pipe through easements and ROW to connect the existing discharge point to the
downstream system on S 312th Street (Figure 7-8). Pipe conveyance was selected over a ditch to minimize
the risk of flooding impacts to private premises and to ensure future conveyance maintenance. The pipe
alignment includes upgrading the ditch and culvert system on S 312th Street to a piped system. The
existing 12-inch-diameter culvert crossing S 312th Street will be increased to a 24-inch-diameter culvert.
The culvert discharges to an open channel that traverses three private properties. The culvert outfall will be
reinforced with riprap.
LOS goal(s)
addressed
Flooding (surface water from ROW runoff entering premises and damaging building structures) with an
annual chance of occurrence of no more than once every 50 years (LOS Goal 5)
Maintain or seek access to City-owned facilities for necessary maintenance and operation. (LOS Goal 13)
Recommended
predesign
refinements
Confirm infiltrative capacity of proposed bioretention sites with infiltration tests. Soils in the area are listed
as NRCS hydrologic soil group “C,” which has a low infiltration rate (0.15 to 0.05 inch per hour), but there
may be localized areas with higher infiltration rates.
Confirm that grades and existing culvert and pipe inlets are sufficient for LID BMP drainage design.
Confirm the open channel downstream of S 312th Street culvert crossing has the capacity for the 100-year
flow (based on City open-channel design standards).
The King County culvert crossing 51st Avenue S is the next culvert downstream of the project area. The
infall to this culvert is partially blocked by a living tree root wad. With more surface flow directed to this
infall, the root wad should be removed. This effort will need to be coordinated with King County.
Obtain easements from two property owners.
Cost estimate
Phase 1
Install 7 gravel trench draining bioretention cells with infall and outfall connection to the
existing drainage system ............................................................................................................ $210,000
Subtotal line-item costs ............................................................................................................. $210,000
Contractor overhead, profit, and mobilization (18% of subtotal of line-item costs) ............... $38,000
Construction contingency (20% of all above construction costs) ............................................ $50,000
Washington State and King County sales tax (9.5% of all above construction costs) ............ $28,000
Subtotal construction costs ....................................................................................................... $326,000
Administration, engineering design, and permitting (25% of construction costs) .................. $82,000
CIP 5B (Phase 1) project cost $408,000
Cost estimate Gravity storm drain: install 385 feet of 18-inch-diameter pipe ................................................ $100,000
Chapter 7 Comprehensive Storm Drainage Plan
7-28
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 5B (Phases 1 and 2 described jointly)
Phase 2 Upsize existing 12-inch-diameter culvert to 24-inch-diameter (36 feet) and reinforce culvert
outlet with riprap ........................................................................................................................ $15,000
Install five connecting structures .............................................................................................. $16,000
Easement acquisition ................................................................................................................. $20,000
Subtotal line-item costs ............................................................................................................. $151,000
Contractor overhead, profit, and mobilization (18% of subtotal of line-item costs) ............... $27,000
Construction contingency (20% of all above construction costs) ............................................ $36,000
Washington State and King County sales tax (9.5% of all above construction costs) ............ $20,000
Subtotal construction costs ....................................................................................................... $234,000
Administration, engineering design, and permitting (30% of construction costs) .................. $70,000
CIP 5B (Phase 2) project cost $304,000
Total CIP 5B project cost $712,000
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!(Storm Node
Storm Pipe
#Storm Infall
#*Storm Outfall
Storm Channel
Storm Culvert
Parcels
Proposed Easement
Proposed Bioretention
%,Proposed Facility
Proposed Drainage Pipe
¯0 250 500125
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COMPREHENSIVE STORM DRAINAGE PLAN
April 2015 Figure 7-8Project 5B:West Hill Drainage Improvements S 314th St. and 54th Ave. S
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Replace existing 12-inch culvert
with 24-inch culvert
Reinforce outfall with riprap
Install 385 lf of 18-inch pipe from
existing discharge point to
new manhole at S 312th St culvert infall
Obtain easement for
existing and new pipe
Comprehensive Storm Drainage Plan Chapter 7
7-31
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 6
Project name North Airport Area Improvements
Location Northern extent of airport property near 30th Street NE
Priority 2
Schedule Begin construction 2016
Problem summary
Pond I: The current configurations of the inlet and outlet of airport Pond I do not allow the pond to operate as
designed. The inlet is intended to receive primary flows from the airport drainage system, but instead is
configured to take only high flows. The pond does not fill from its inlet because the inlet elevation is higher
than designed. The inlet is made further ineffective by an inverse grade or high point along its alignment.
Rather than accepting primary or low flows through its inlet and releasing detained water through a flow
control riser to the storm system in 30th Street NE, the pond fills from its outlet because of a disconnected
riser when the storm line in 30th Street NE surcharges. This surcharging usually occurs prior to the high
flows entering the pond.
North Hangar Area: In the north hangar area immediately east of Pond I, surcharging flows from the storm line
in 30th Street NE backwater to the airport’s 30-inch-diameter storm drain and causes flooding to the north
and west of the most northerly hangar. Historically, the flooding extends to part of the taxiway and into the
hangar. The grate inlets in 30th Street NE are higher than the ground elevation of the northern airport area,
which allows the airport area to flood before street flooding occurs in 30th Street NE. In addition, given that
onsite runoff is not being diverted to or retained by Pond I, onsite flows contribute to the north hangar area
surcharging.
Description:
Pond I: This project would provide Pond I with more detention volume and allow the pond inlet and outlet to
operate as intended, collecting and detaining surface water generated on airport property with high flows
discharging to the 30th Street NE system. The project would excavate portions of the pond to provide more
storage capacity, replace the existing inlet pipe at a lower invert and consistent positive slope to capture the
primary flow, reconnect the flow control structure to the outlet, and install a backflow preventer at the
outlet.
North Hangar Area: The project for the north hangar area consists of installing a backflow preventer at the
connection to the 30th Street NE system. Pond I upgrades need to be completed first because the north
hangar area is at a lower elevation and receives flow from both the airport drainage and the 30th Street NE
system. Because portions of the airport area have lower elevations than the adjacent 30th Street NE
system, the north hangar area may experience some localized flooding, even with the Pond I upgrades and
installation of backflow preventers, because the 30th Street NE is higher. This project would be constructed
as shown in Figure 7-9.
LOS goal(s)
addressed
Flooding disruption that inundates the roadways to an impassable level no more than once every 25 years
(LOS Goal 4)
Flooding (surface water from ROW runoff entering premises and damaging building structures) no more
than once every 50 years (LOS Goal 5)
Recommended
predesign
refinements
None
Cost estimate
Pond I:
Excavate portions of the pond .............................................................................................. $46,000
Replace and lower pond inlet pipe ...................................................................................... $25,000
Upgrade diversion manhole ................................................................................................. $4,000
Replace flow control manhole at pond outlet ..................................................................... $4,000
Install backflow preventer .................................................................................................... $7,000
North Hangar Area:
Install backflow preventer for 30-inch-diameter pipe .......................................................... $14,000
Subtotal line-item costs ......................................................................................................... $100,000
Contractor overhead, profit, and mobilization (18% of subtotal of line-item costs) ........... $18,000
Construction contingency (30% of all above construction costs) ........................................ $35,000
Chapter 7 Comprehensive Storm Drainage Plan
7-32
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 6
Washington State and King County sales taxes (9.5% of all above construction costs) .... $15,000
Subtotal construction costs $168,000
Administration, engineering design, and permitting (30% of construction costs) $50,000
CIP 6 project cost $218,000
Repair flow control connection
and install backflow preventer
Replace pipe at new slope
Adjust pond inlet invert
Install backflow preventer
Excavate portions of the pond
Pond
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!(Storm Node
Storm Pipe
Storm Channel
Storm Culvert
Storm Pond
%,Proposed Facility
Proposed Drainage Pipe
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COMPREHENSIVE STORM DRAINAGE PLAN
April 2015 Figure 7-9Project 6: North Airport Area Improvements
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Comprehensive Stormwater Drainage Plan Chapter 7
7-35
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 7
Project name D St. SE Storm Improvements
Location Western end of 25th Street SE near D Street SE right-of-way
Priority 2
Schedule Begin construction 2018
Problem summary
The western dead-end portion of 25th Street SE has a history of observed flooding. An existing dry well has
inadequate infiltration. The dry well floods after heavy rain, several times a year. Floodwater fills the
adjacent section of 25th Street SE to the curb. There are also numerous dry wells not meeting discharge
standards in this area.
Description
This project consists of installing a new gravity drain to convey the peak 25-year flow rate from the flooding
location to the 21st Street stormwater pond (Figure 7-10). New piping consists of a 24-inch-diameter
gravity drain from the existing dry well location (at the intersection of D Street SE ROW and 25th Street SE)
north along D Street SE to the intersection of 23rd Street SE. New 30-inch-diameter gravity drain would be
installed from 23rd Street SE to the existing junction with the 48-inch-diameter gravity pipe in 21st Street
SE.
The existing dry wells at 23rd Street SE and 22nd Street SE would be removed. Conveyance piping to these
dry wells would be connected to the new 30-inch-diameter gravity drain.
The conveyance piping, along 25th Street SE, to the problematic dry well will be replaced with a new 12-
inch-diameter gravity drain because the existing conveyance is lower than the proposed conveyance piping
along D Street SE.
Additional dry wells at 26th Street SE and 27th Street SE would be removed. Conveyance piping along 26th
Street SE will also be replaced with a 12-inch-diameter gravity drain, because the existing conveyance
flows to the east.
A sixth dry well system, located at 27th Street SE and F Street SE, will be replaced with a gravity drain. A
12-inch-diameter gravity drain will be installed along F Street SE and connect to the existing manhole at the
intersection at 26th Street SE.
Recommended
predesign
requirement
None
LOS goal(s)
addressed
Flooding disruption that inundates the roadways to an impassable level no more than once every 25 years
(LOS Goal 4)
Cost estimate
Gravity piping: 990 feet of 30-inch-diameter pipe, 630 feet of 24-inch-diameter pipe,
and 1,610 feet of 12-inch-diameter pipe ................................................................... $906,000
Subtotal line-item costs ............................................................................................... $906,000
Contractor overhead, profit, and mobilization (18% of subtotal of line-item costs) . $163,000
Construction contingency (20% of all above construction costs) .............................. $214,000
Washington State and King County sales tax (9.5% of all above construction costs)
...................................................................................................................................... $122,000
Subtotal construction costs......................................................................................... $1,405,000
Administration, engineering design, and permitting (30% of construction costs) .... $422,000
CIP 11 project cost $1,827,000
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Install 990 lf 30-inch-diameter
drainage pipe
Install 1,230 lf 12-inch-diameter
drainage pipe
Install 630 lf 24-inch-diameter
drainage pipe
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!(Storm Node
!(Storm Node with flow control
!(Dry Well
Storm Pipes
Storm Pond
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¯0 300 600150
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COMPREHENSIVE STORM DRAINAGE PLAN
April 2015 Figure 7-10Project 7: D St. SE Storm Improvements
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Comprehensive Stormwater Drainage Plan Chapter 7
7-39
DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the end of this document.
Auburn Drainage Plan Draft.docx
Project number 8
Project name 23rd St. SE Drainage Improvements
Location 23rd and K streets SE
Priority 3
Schedule Begin construction 2018
Problem summary
A new 12-inch-diameter stormwater gravity drain was installed along K Street SE, south of 23rd Street SE,
in 2014 to address localized flooding. This piping increased the tributary area to the 8-inch-diameter
gravity drain along 23rd Street SE. Modeling results indicate that the existing 8-inch-diameter gravity drain
along 23rd Street SE does not meet the LOS.
Description
This project has a phased approach. Phase 1 consists of installing a new 15-inch-diameter gravity drain
along K Street SE from the intersection of 23rd Street SE to the intersection of 21st Street SE (Figure 7-
11). The new pipe would connect to the existing 24-inch-diameter system along 21st Street SE, which
eventually discharges to the 21st Street Pond. The existing 8-inch-diameter gravity drain pipe conveying
flow west from the intersection of K Street SE and 23rd Street SE would be plugged so that all runoff on K
Street SE would be conveyed north.
Phase 2 consists of installing a new 18-inch-diameter gravity drain along 23rd Street SE from H Street SE
to F Street SE. The new pipe would connect to the existing 24-inch-diameter system along 23rd Street SE.
This system eventually discharges to the 21st Street Pond. After completion of Phase 1 and prior to
implementing Phase 2, the storm system along 23rd Street SE should be monitored during large events to
confirm that water levels in pipe are surcharging. An existing detention system in the tributary area was not
explicitly modeled during project development, and may manage flows such that simulated surcharging
does not occur. If this is the case, then Phase 2 would not be required to meet the City’s LOS.
Recommended
predesign
requirement
Periodic site inspections by the maintenance crews during storm events to observe water levels in pipes
along 23rd Street SE
LOS goal(s)
addressed
Flooding disruption that inundates the roadways to an impassable level no more than once every 25 years
(LOS Goal 4)
Cost estimate
Phase 1: Gravity piping: 600 feet of 18-inch-diameter pipe, plug existing 8-inch-
diameter pipe ............................................................................................................... $157,000
Phase 2: Gravity piping: 560 feet of 21-inch-diameter pipe ..................................... $157,000
Subtotal line-item costs ............................................................................................... $314,000
Contractor overhead, profit, and mobilization (18% of subtotal of line-item costs) . $57,000
Construction contingency (20% of all above construction costs).............................. $74,000
Washington State and King County sales tax (9.5% of all above construction costs)
...................................................................................................................................... $42,000
Subtotal construction costs ........................................................................................ $487,000
Administration, engineering design, and permitting (30% of construction costs).... $146,000
CIP 8 project cost $633,000
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Phase 2:
Install 560 lf 18-inch-diameter
drainage pipe
Phase 1:
Install 600 lf 15-inch-diameter
drainage pipe
Phase 1:
Disconnect drainage pipe
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25TH ST SE
23RD ST SE
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24TH ST SE
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LEGEND
!(Storm Node
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Storm Pond
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¯0 300 600150
Feet
COMPREHENSIVE STORM DRAINAGE PLAN
April 2015 Figure 7-11Project 8: 23rd St. SE Drainage Improvements
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Comprehensive Stormwater Drainage Plan Chapter 7
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Project number 9
Project name Comprehensive Storm Drainage Plan update
Location City-wide
Priority 1
Schedule Begin development 2020
Problem summary The Storm Drainage Utility is responsible for the maintenance, operations and improvements of the storm
drainage system.
Description
The Comprehensive Storm Drainage Plan would include an update to the capital projects in the existing
plan. Projects not completed, but still required to address a problem would be reevaluated and updated
based on recent information, such as drainage system inventory, system changes, flow monitoring,
flooding, and recent unit costs.
It would also include capital projects to address newly identified problems, including projects resulting from
the Hillside Drainage Assessment (project number 3) and the flow monitoring proposed in the
Implementation Plan (Chapter 8).
The plan would include additional activities required to address new regulatory requirements.
The plan would include cost-of-service studies to reassess the monthly service fees and SDCs.
LOS goal(s)
addressed
The Comprehensive Storm Drainage Plan guides the City’s Storm Drainage Utility with respect to future
activities and improvements in order to meet established LOS goals.
Cost estimate Update Comprehensive Storm Drainage Plan ............................................................ $300,000
CIP 9 project cost $300,000
Comprehensive Stormwater Drainage Plan Chapter 7
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Programmatic Drainage Projects 7.3
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. Table 7-1 lists programmatic
projects 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- and 20-year CIPs in Chapter 8.
Table 7-1. Summary Programmatic Drainage Projects
CIP
number Project or program name and description Priority Total project cost
(2014 dollars)
10
Composting Facility. This project addresses the need for a new site to store and
process materials removed from drainage ditches, swales, and ponds during
maintenance and restoration activities necessary to maintain the storm drainage
system. The current site is on Parks Department property, and the Parks Department
has plans to use the property, precluding its use for ongoing M&O activities. This
project includes the purchase of property (preferably located central to maintenance
and restoration sites) and yearly costs associated with processing the materials for
disposal.
LOS Goal Addressed: Goal 12. “The City shall seek to maintain storm drainage
infrastructure to ensure proper function of drainage facilities in accordance with
Ecology requirements.”
2 $1,379,000
11
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 R&R
should be developed by adhering to LOS Goals 8–9 and 11 regarding the
maintenance of a criticality database and the prioritized assessment of critical
infrastructure.
LOS Goal Addressed: Goal 10. “The City shall seek to repair or replace system assets
before they exceed their economic lives.”
1 $11,000,000
12
Street Utility Improvements. The Storm Drainage Utility will seek opportunities to
incorporate drainage improvements into transportation and pavement projects on city
roads. The majority of storm drainage costs related to projects that bring streets to
current design standards are incurred by the City’s Transportation Program.
LOS Goal Addressed: Goal 23. “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.
1 $2,000,000
8-1
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Chapter 8
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 Storm Drainage Utility. The information in this
chapter serves as a road map to the Storm Drainage Utility staff. This road map outlines the critical
elements of plan implementation (e.g., CIP implementation, stormwater monitoring, NPDES Permit
compliance, future staffing, and asset management) and links them into a schedule of utility activities.
The implementation plan is divided into six main sections:
• Section 8.1 presents the CIP for both 6-year and 20-year time frames. Section 8.2 describes
recommendations for future monitoring and data collection to support future planning activities.
• Section 8.3 contains a summary of activities for NPDES Permit compliance.
• Section 8.4 presents recommendations for future staffing.
• Section 8.5 describes recommendations for continuing the implementation of best practices for
asset management.
• Section 8.6 makes recommendations for additional activities that help the Storm Drainage Utility
achieve the LOS goals.
The foldout chart (Figure 8-4) at the conclusion of this chapter shows the proposed implementation
timeline. Appendix D provides the SEPA determination for the implementation plan.
6-Year and 20-Year CIP 8.1
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 7. In addition to site-specific projects, the 6-year CIP contains
ongoing programmatic efforts, such as the Storm Drainage Utility’s participation in the Street Utility
Improvement program. Table 8-1 lists all 11 capital improvement projects described in Chapter 7 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 Table 8-1 and Figure 8-1).
Chapter 8 Comprehensive Storm Drainage Plan
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Table 8-1. Annual Project Cost Summary for 6-Year CIP
Project
number Project name Priority Repair/
Replacement
Upgrade/
Expansion 2016 2017 2018 2019 2020 2021 6-year project
cost, $
1 West Main Street Pump Station Upgrade 1 100% 2,968,000 2,968,000
2 37th and I Streets NW Storm
Improvements 1 100% 291,000 291,000
3 Hillside Drainage Assessment 1 100% 139,000 150,000 289,000
4A 30th Street NE Area Flooding, Phase 2 2 100% 896,000 896,000
4B 30th Street NE Area Flooding, Phase 3 3 100% 2,124,000 2,124,000
5A West Hills Drainage Improvements at S
330th St. and 46th Pl. S 2 100% 317,000 317,000
5B West Hills Drainage Improvements near S
314th St. and 54th Ave. S 3 100% 408,000 304,000 712,000
6 North Airport Area Improvements 2 100% 218,000 218,000
7 D St. SE Storm Improvements 2 100% 1,827,000 1,827,000
8 23rd St. SE Drainage Improvements 3 100% 316,500 316,500 633,000
9 Comprehensive Storm Drainage Plan
update 1 35% 65% 300,000 300,000
10 Composting Facility 1 100% 750,000 22,000 23,100 24,300 25,600 845,000
11 Storm Drainage Infrastructure Repair and
Replacement Programa 1 100% 100,000 1,000,000 100,000 1,000,000 100,000 1,000,000 3,300,000
12 Street Utility Improvementsa 1 100% 100,000 100,000 100,000 100,000 100,000 100,000 600,000
Total 6-year CIP cost for priority 1 projects 3,598,000 2,000,000 222,000 1,123,100 524,300 1,125,600 8,593,000
Total 6-year CIP cost for priority 2 projects 535,000 896,000 1,827,000 0 0 0 3,258,000
Total 6-year CIP cost for priority 3 projects 0 0 724,500 2,124,000 304,000 316,500 3,469,000
Total 6-year CIP cost $4,133,000 $2,896,000 $2,773,500 $3,247,100 $828,300 $1,442,100 $15,032,000
a. Additional project costs included in 20-year CIP.
Comprehensive Storm Drainage Plan Chapter 8
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Figure 8-1. 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 development
and redevelopment projects will be subject to the City’s development standards for onsite stormwater
control. Local stormwater detention and integrated LID stormwater features should control stormwater
flows to maintain approximately 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 R&R, where the R&R schedule is based on asset conditions and prioritizes assets that
are nearing the end of their economic life. Table 8-2 summarizes the program expenditures and
forecasts total CIP costs for the years 2022 to 2035.
$0
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$1,000,000
$1,500,000
$2,000,000
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2016 2017 2018 2019 2020 2021
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Table 8-2. Cost Summary for 20-Year CIP
Project
number Program name Priority Project costs for 2022–35
(2014 dollars)
10 Composting Facility 1 $533,800
11 Storm Drainage Infrastructure Repair and Replacement Program 1 7,700,000
12 Street Utility Improvements 1 1,400,000
Total 2022–35 CIP cost for priority 1 projects 9,633,800
Total 2022–35 CIP cost for priority 2 projects 0
Total 2022–35 CIP cost for priority 3 projects 0
Total CIP cost (2022–35) $9,633,800
Total 20-year CIP cost (2016–35) $24,954,000
In addition to the identified projects and programs, the City identified two potential problem areas that
may warrant a project in the future (see Section 4.5). Projects were not developed for this these areas
for the following reasons: (1) existing data were inadequate to understand the potential problem, or (2)
stormwater routing to the area may be changing (because of implementation of an upstream City or
private project), which could affect the need, sizing, and timing of a project. These potential problem
areas require additional data to obtain a better understanding needed to develop a capital improvement
project, if warranted. Section 8.2 provides recommendations for activities that will assist with
understanding and addressing the potential problems.
Monitoring 8.2
Evaluating the adequacy of the storm drainage system and analyzing potential capital improvements
require extensive data. This includes not only infrastructure data such as pipe sizes, invert elevations,
and outfall locations, but also stormwater data such as runoff volumes, flow rates, 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 for identified potential problems, as well as summarizing ongoing monitoring efforts.
8.2.1 Precipitation
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 a Texas Electronics
Model TE525 gauge to record precipitation data with network connectivity allowing for data downloading
by City staff. The City also has a manual rain gauge where data are collected weekly. These data are
used to back up and validate the TE525 gauge data. The City should continue to monitor precipitation at
City Hall using this equipment or updated equipment.
8.2.2 Flow
Flow data are used to gain a better understanding of the H&H 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. Two potential problem locations require newly collected flow data to perform
model development and calibration, which will support the analysis of problem area (see Section 4.5 for
discussion on potential problem areas). Table 8-3 lists each of the recommended flow monitoring sites,
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purpose, type of measurement, recommended start year, and approximate duration of monitoring. Figure
8-2 shows the proposed monitoring locations.
Table 8-3. Proposed Flow Monitoring Sites
Site numbera Location Purpose Measurement Start year Approx.
durationb
Potential problem area: Riverwalk Drive and Howard Road (directing tributary area to17th and 21st Street ponds)
P1012-
C690_C689
Intersection of
Auburn Way S and
Riverwalk Dr. SE
Quantify flow from upstream areas tributary to
flow control device in CB1012-C688
Depth and
velocity 2016 1 to 2 wet seasons
CB1012-C688
Intersection of
Auburn Way S and
Riverwalk Dr. SE
Estimate flows to high flow ditch on Riverwalk Dr.
SE Depth 2016 1 to 2 wet seasons
C1111-
C1469_C1470
Intersection of
Howard Rd. and
Riverwalk Dr. SE
Quantify flows to support modeling flows that
may be connected to the City’s system at
CB1011-C1474
Depth and
velocity 2016 1 to 2 wet seasons
P1011-
C1452_C1453
Howard Rd. between
21st St. SE and
Riverwalk Dr. SE
Quantify flows to support modeling flows that
may be connected to the City’s system at
CB1011-C1474
Depth and
velocity 2016 1 to 2 wet seasons
P1011-
C1086_C1137
Howard Rd. between
21st St. SE and
Riverwalk Dr. SE
Quantify flows to support modeling flows that
may be connected to the City’s system at
CB1011-C1474
Depth and
velocity 2016 1 to 2 wet seasons
P1010-C3_C29 Howard Rd. near
Auburn Way S
Provide data for H&H model calibration
(subbasin C)
Depth and
velocity 2016 1 to 2 wet seasons
P1010-
B220_B221
21st and K Streets
SE
Provide data for H&H model calibration
(subbasin C) post-CIP (AWS Phase 2)c
Depth and
velocity 2016 1 to 2 wet seasons
Potential problem area: 2nd and G streets SE
P909-
C122_C121
Auburn Way S, near
9th St. SE
Quantify flows upstream of flow split (at MH 909-
C12) between subbasins B and C, and provide
data for H&H model calibration
Depth and
velocity
Post-AWS
Phase 2c,d
1 to 2 wet seasons
P809-
C113_C112
F St. SE, north of SR
18
Quantify flows upstream of sewer crossing, and
provide data for H&H model calibration
Depth and
velocity
Post-AWS
Phase 2c,d
1 to 2 wet seasons
P810-
C701_809-C18
G St. SE and E Main
St.
Provide data for H&H model calibration (subbasin
C)
Depth and
velocity
Post-AWS
Phase 2c,d
1 to 2 wet seasons
P810-C698_C16 M St. SE, south of E
Main St.
Provide data for H&H model calibration since M
St. Grade Separation and Well 1 Transmission
Projects implementation
Depth and
velocity
Post-AWS
Phase 2c,d
1 to 2 wet seasons
P810-C15_C241 E Main St. and N St.
SE Estimate backwater effects on drainage system Depth and
velocity
Post-AWS
Phase 2c,d 1 to 2 wet seasons
a. P = pipe, C = culvert, CB = catch basin, MH = manhole.
b. Data to support CIP need 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. Monitoring period and duration within a potential problem area should
be the same.
c. Auburn Way S Flooding, Phase 2 (AWS Phase 2) is planned for construction in 2015.
d. Detailed survey of the flow split at MH 909-C12 should be completed prior to flow monitoring, to understand system hydraulics at this
location.
!A
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!A
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!R CB512-AZ476
CB1012-C688
P1010-C3_C29
WL-Pond-Mill
P810-C15_C241
P810-C698_C16
WL-Pond-LakeE
WL-Pond-RiverN
P909-C122_C121
P809-C113_C112
WL-Pond-LakeS2
WL-Pond-LakeS1
P1010-B220_B221
P1012-C690_C689
P513-AZ519_AZ520
P810-C701_809-C18
C1111-C1469_C1470
P1011-C1452_C1453P1011-C1086_C1137
RG-01
WL-Mill-03
WL-Mill-04
WL-Mill-02
WL-Mill-01
WL-Pond-17thSt
WL-Pond-21stSt
LEGEND
!A Proposed Monitoring Site
!R Existing Monitoring Site
XW City Rain Gauge
Storm Pipe
Watercourse
Water Body
Wetland
Auburn City Boundary
¯0 4,000 8,0002,000
Feet
COMPREHENSIVE STORM DRAINAGE PLAN
April 2015 Figure 8-2Proposed MonitoringLocations
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8.2.3 Stream and Pond Water Level
Water level data can also be useful for evaluating the performance of stormwater ponds and assessing
the risk of overtopping. Monitoring also will enable the City to identify changes in performance that may
indicate excessive sedimentation and the need for active maintenance. Additionally, continued water
level monitoring will help the City evaluate changes in Mill Creek water elevations that may occur
because of restoration and culvert replacement activities along Mill Creek.
The City should continue its 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
telemetry system, wherever continuous power and data lines are available. Table 8-4 lists each of the
recommended water level monitoring sites, purpose of the monitoring, recommended start year, and
approximate duration of monitoring.
Table 8-4. 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 Ongoing since 2011 10 yearsa
WL-Mill-02 Mill Creek at 29th St. NW Evaluate stages in Mill Creek and assess backwater
effects on drainage system Ongoing since 2011 10 yearsa
WL-Mill-03 Mill Creek at 15th St. NW Evaluate stages in Mill Creek and assess backwater
effects on drainage system Ongoing since 2011 10 yearsa
WL-Mill-04 Mill Creek at West Main St. Evaluate stages in Mill Creek and assess backwater
effects on drainage system Ongoing since 2011 10 yearsa
WL-Pond-17thSt 17th and A streets SE Monitor pond performance (water levels and infiltration
rates) Ongoing since 2010 Indefiniteb
WL-Pond-21stSt 21st and D streets SE Monitor pond performance (water levels and infiltration
rates) Ongoing since 2011 Indefiniteb
WL-Pond-RiverN Riverwalk Dr. SE and U St. SE
Monitor pond performance (water levels and infiltration
rates) and evaluate capacity in support of analysis for
potential problem area at Riverwalk and Howard Road
2015 Indefiniteb
WL-Pond-LakeS1 Lakeland South Pond 1 Monitor water level to evaluate hazard risk (dam safety) 2015 Indefiniteb
WL-Pond-LakeS2 Lakeland South Pond 2 Monitor water level to evaluate hazard risk (dam safety) 2015 Indefiniteb
WL-Pond-LakeEP Lakeland East Pond Monitor water level to evaluate hazard risk (dam safety) 2015 Indefiniteb
WL-Pond-Mill Mill Pond (Oravetz Rd. SE) Monitor water level to evaluate hazard risk (dam safety) 2015 Indefiniteb
c. Based on need to examine backwater effects on system; if new capital improvements are identified for Mill Creek, additional years may be
needed.
d. To be continually reevaluated; if data indicate that stormwater pond is performing adequately or has low risk of failure, then monitoring
could cease.
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8.2.4 Water Quality
The current NPDES Permit, which is effective through 2018, includes provisions for monitoring and
assessment of water quality. Permittees have the option of paying annual fees to participate in statewide
monitoring programs, or developing individual monitoring programs to meet the requirement. The City
notified Ecology in 2013 that it intends to participate in the statewide monitoring programs. By opting to
participate in statewide monitoring programs, the City has agreed to pay program fees to Ecology. Fees
totaling $47,710 are due annually, beginning in August 2014. Refer to Section S8 of the current NPDES
Permit (Appendix A) for additional information.
Programmatic Measures for NPDES Compliance 8.3
The City of Auburn is covered by the Western Washington Phase II Municipal Stormwater Permit (NPDES
Permit). The Permit regulates stormwater discharges from the City’s MS4 (see Section 2.3.2). The
current version of the Permit will remain in effect through July 2018, when a new version is due to be
issued.
The City is actively engaged in stormwater management activities to comply with the Permit, including
the following:
• SWMP administration
• Public education and outreach
• Public involvement and participation
• IDDE
• Control of runoff from new development, redevelopment, and construction sites
• Municipal operations and maintenance
• Monitoring and assessment
The City maintains and annually updates its SWMP Plan, which documents new and ongoing stormwater
management activities planned for the upcoming year. The current SWMP Plan is available on the City’s
website.
Updates to City codes, programs, and standards are required by the end of 2016 to comply with the
current NPDES Permit. The City is engaging in a process to evaluate, plan, and implement necessary
updates to City regulations and programs. The process will engage staff across City departments, the
public, and elected officials to evaluate and determine updates. As part of the process, the City
developed a Compliance Work Plan to outline and guide compliance activities over the current NPDES
Permit term. A copy of the Compliance Work Plan is included as Appendix B. The compliance schedule
for key requirements under the current NPDES Permit is shown in Figure 8-3.
One of the key NPDES Permit requirements is adoption of an updated stormwater manual. To meet this
requirement, the City may opt to update the Auburn SWMM to maintain equivalency with the 2012
Ecology Stormwater Management Manual for Western Washington. Alternatively, the City could adopt the
Ecology manual or an approved equivalent stormwater manual developed by an NPDES Phase I
jurisdiction (e.g., City of Tacoma). Potential updates to the SWMM represent a major effort for City staff,
and would need to be planned for accordingly.
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Figure 8-3. NPDES Compliance Schedule
Future Staffing and Equipment Needs 8.4
During this planning effort, current Engineering and M&O staffing were reviewed in light of future
activities that will need to be performed to maintain compliance with the NPDES Permit. M&O staffing
and equipment were also reviewed in light of existing maintenance goals and future, additional M&O
responsibilities. The following sections summarize the additional staffing, staffing responsibilities, and
equipment needs for the Storm Drainage Utility.
8.4.1 Engineering Services
This section discusses additional Engineering staffing responsibilities necessary to address
requirements of the revised NPDES Permit and other identified storm drainage system deficiencies.
Many of the new requirements of the NPDES Permit emphasize implementation of LID practices, such as
minimizing impervious surfaces, native vegetation loss, and stormwater runoff. A majority of new
development and redevelopment projects will be required to construct new types of onsite LID facilities,
which will need to be inspected and maintained to ensure proper function.
Under an NPDES Compliance planning effort, an estimate of the additional efforts required by the City to
address NPDES Permit requirements was prepared (Appendix B). The need and timing of additional
Engineering staff is summarized as follows:
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• In 2016, existing staff will need to accomplish the following NPDES compliance activities:
− Update public guidance material and checklists to align with new City/NPDES Permit
requirements
− Develop procedures for public LID facility maintenance and oversight of private facilities
− Update or adopt the Stormwater Manual to meet requirements
− Develop City planning methods and update ACC to meet new Permit requirements for
stormwater, including new runoff control requirements thresholds, BMP performance standards,
and LID requirements
− Update the City Comprehensive Plan related to implementation of LID principles that could
affect elements beyond stormwater management implementation such as LOSs, setbacks,
zoning densities, etc.
• By 2017, it is estimated that additional staff (1.15 FTEs) will be needed for NPDES compliance
activities:
− Inspect new LID facilities regularly, and purchase and maintain associated field instruments
required to perform inspections (1 FTE). Depending on the level of future development,
additional staff beyond 1 FTE may be required.
− Define and organize LID asset classification, coordinate/update maintenance tracking methods,
and track and record maintenance of stormwater assets (0.1 FTE).
− 0.05 FTE to update public education and outreach materials to include additional target
audiences, evaluate program effectiveness, and conduct regional coordination (0.05 FTE).
Additional staffing needs described above and their associated costs, assuming an FTE annual
salary and benefits are $93,000, are summarized in Table 8-5.
Table 8-5. Future Engineering Services Staffing Needs
Additional Engineering Services activity Staff needs (in
2017) Cost
LID facility inspector to inspect new LID facilities regularly, and purchase
and maintain associated field instruments required to perform
inspections. Depending on the level of future development, additional
staff beyond 1 FTE may be required.
1 FTE $93,000
Define and organize LID asset classification, coordinate/update
maintenance tracking methods, and track and record maintenance of
stormwater assets.
0.1 FTE $9,300
Update public education and outreach materials to include additional
target audiences, evaluate program effectiveness, and conduct regional
coordination.
0.05 FTE $4,650
2017 total cost $106,950
8.4.2 M&O Services
The M&O staffing required to efficiently manage, operate, and maintain the storm drainage system was
evaluated in Chapter 6. The analysis indicates that the Storm Drainage Utility is appropriately staffed
with respect to meeting proactive City goals for current M&O activities. Additional staff and equipment,
however, will be needed to meet NPDES Permit requirements and other anticipated future work (see
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Section 6.6.2). Future M&O staffing requirements are described in Section 6.6.2 and summarized in
Table 8-6.
Table 8-6. Future Maintenance and Operations Staffing Needs
Additional M&O activity FTE days
required annually Assumptions/City goal
Drainage ditch and stormwater pond maintenance and restoration
Drainage ditch maintenance and restoration 216 Six-person crew for 36 days during the summer months.
Stormwater pond restoration 330 Six-person crew for 55 days during the summer months.
Other stormwater M&O activities
Cartegraph tracking and reporting 111 Approximately 0.5 FTE (1 FTE shared with Sewer and Water utilities).
LID inspection and maintenance 104 One day per week. Two-person crew.
Total 761
Total number of working days available
per FTE 221 365 minus weekends (104), holidays (12), vacation (15), sick (12), and
training (1).
Number of additional FTEs required 3.4 761 days required divided by 221 days per FTE year.
Based upon discussions with City staff and analysis of M&O activities discussed in Chapter 6, the Storm
Drainage Utility should obtain or upgrade the following utility equipment to improve M&O efficiency:
• CCTV inspection equipment
• Excavator for ditch and stormwater pond maintenance
Continue Implementation of Best Practices for Asset Management 8.5
The 6-year CIP focuses mainly on existing flooding problems where recent storm events have revealed
deficiencies in the drainage system. The capital improvement projects are designed to mitigate flooding
in these areas and are expected to provide immediate benefits. As current problems are addressed in
the near term, the focus of the CIP can begin 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.
The following sections present recommendations for future and ongoing asset management activities for
the Storm Drainage Utility. Section 8.5 is divided into the following five sub-sections:
• Section 8.5.1 discusses the continued development of the system inventory.
• Section 8.5.2 provides a discussion about ways to optimize the M&O program through criticality-
based strategies and use of the CMMS.
• Section 8.5.3 discusses economic life model improvements
• Section 8.5.4 provides a discussion about ways to optimize the M&O and R&R programs with the
economic life model.
• Section 8.5.5 summarizes additional M&O activities identified during the M&O evaluations
8.5.1 Continue System Inventory
A comprehensive system inventory is needed for many reasons, including:
• Understanding existing problems
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• Developing strategies to address existing problems
• Conducting analysis to support detailed design of capital improvement projects
• Prioritizing maintenance activities
• Budgeting and developing a schedule for R&R
A system inventory includes documenting at a minimum the location, size, length, material, depth,
condition, and maintenance history of all drainage assets. The magnitude of the system inventory effort
is quite large and the City has made great strides in updating its inventory through dedicated survey
staff. Staff have been working throughout the city, quarter section by quarter section. Even though
significant progress has been made, of the 137 quarter sections covering the City’s storm drainage
system, only 32 (about 25 percent) have been inventoried. An additional 11 (8 percent) are in progress.
Therefore, it is recommended that the data inventory task be continued as part of future activities, and
that the inventory be continually updated to reflect additional data collected during maintenance
activities (i.e., condition assessment and frequency of maintenance activities) and drainage system
changes through capital improvement projects.
8.5.2 Implement Economic Life Model Using Cartegraph Data
An economic life model containing data for the City’s stormwater drainage pipes was developed as part
of the 2009 Drainage Plan. The model predicts a probability and a cost of failure for each pipe segment.
The model calculates the risk cost of an asset by multiplying the probability of the asset failing by the
cost of that asset failing. By comparing the risk cost of each segment to the minimum annualized cost of
ownership for an intervention, the optimal economic timing for either rehabilitation or replacing each
segment is calculated. A detailed description of the economic life analysis is provided in the 2009
Drainage Plan.
Evaluations completed for this Drainage Plan consisted of developing a software requirement
specification (SRS) describing the requirements and calculations required to implement the economic
life model for the City’s stormwater collection system using Cartegraph CMMS as a primary data source
(Brown and Caldwell, 2014). Following the SRS, the City should implement the economic life model as
well as the mode improvements described in Section 8.5.3. With continual updates of the internal data
into Cartegraph (as described in Section 8.5.1), the model will continue to improve and become more
useful for guiding maintenance and R&R activities, as described in Section 8.5.4.
8.5.3 Economic Life Model Improvements
The results from the economic life model are only as accurate as the inputs. Therefore, after
implementing the model, improving the accuracy of the information on which the model is built is the
focus for future efforts. The data input improvements can be organized into the following three groups of
information:
• Need for additional infrastructure information: The economic life model is based on data describing
the current conditions of stormwater infrastructure. The completeness and accuracy of these input
data (see Section 8.5.1) are crucial to the usefulness of the economic life-cycle analysis results.
• Cost assumptions: Continually verifying and customizing cost information for spot repairs costs (as a
function of depth of bury and pipe location), as well as social and environmental costs (i.e., impact of
a pipe failure on traffic) will ensure that the model calculates accurate intervention timings and that
cost projections represent an accurate spending program for the Storm Drainage Utility.
• Failure assumptions: 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 (i.e.
asset age, pipe material); however, verifying the parameters used to describe the distribution will
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require information on actual failure rates. With this information, the probability function can be
customized specifically to the Storm Drainage Utility and will better predict optimal intervention
timing.
In addition to updates to the pipe model, the model could be expanded to include catch basins and
manholes. Including catch basins and manholes in the economic life model will allow M&O staff to
identify those facilities with the highest potential cost of failure and that represent the greatest risk to
the City, and to better identify which catch basins and manholes are nearing the end of their useful life,
allowing M&O staff to better focus their maintenance activities. The information provided by the model
(through maintenance records) may help to confirm to Ecology that less frequent catch basin
inspections, cleaning and maintenance are sufficient, as compared to the biennial inspections required
by the NPDES Permit.
Generally, the approach and calculations used by the model apply equally to catch basins and manholes.
However, additional work, as described in the SRS, must be performed to determine the values for some
model parameters.
8.5.4 Maintenance and R&R Prioritization
Once the data inventory is complete, and the economic life model is implemented, the City can use the
model to estimate and evaluate the risk cost associated with each of its drainage pipe segments, catch
basins, and manholes. The model can be used to evaluate the condition of this infrastructure and
identify predictive maintenance and R&R needs.
Maintenance activities can be prioritized to focus on the assets for which the City is carrying the majority
of its risk. The risk provides justification for focused conditional assessment activities (e.g., CCTV
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, less-frequent, or even a “run-to-
failure” approach for low risk assets.
R&R budget and long-term rate forecasting can be developed, and a business case validation can be
made for each segment intervention. The model results can be sorted in multiple ways to develop
specific R&R needs such as a prioritized intervention list. The model’s benefit/cost ratio can be used to
identify interventions that would result in the greatest savings for the lowest price. As multiple segments
become due for intervention, the benefit/cost ratio can be used as a means to prioritize where finite
R&R funds are spent. As 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 (e.g., short, small-
diameter segments), using cost of failure for segments due for intervention would provide an alternative
project priority list. Model results will identify intervention timing for all segments, but high-cost of failure
segments (e.g., larger pipes that are expensive to replace) could potentially show lower on an R&R
priority list using only benefit/cost.
8.5.5 M&O Activities
In addition to the identified staffing and equipment needs described in Section 8.4, the following M&O
opportunities are available to improve existing activities:
• M&O staff are integral to the continual update to the system inventory described in Section 8.5.1. As
they perform maintenance activities they should continue to update infrastructure attributes stored
in Cartegraph.
• The City should continue the implementation of the NASSCO PACP MACP certified inspection
programs to allow integration of inspection and condition assessment results with Cartegraph. The
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City should provide staff training to ensure assessment consistency including documentation using
defined criteria such as leaks/cracks observed, cleanliness, and other specific measures.
• All M&O repair projects should be constructed to established City engineering standards to ensure
best practices are being used. It is also recommended that the City develop a more formal
procedure for tracking M&O repair projects to ensure that as-built and Cartegraph records are
updated when projects are completed.
Recommendations for Additional Activities 8.6
The following sections present recommendations for additional activities for the Storm Drainage Utility.
Section 8.6 is divided into the following three sub-sections:
• Section 8.6.1 prescribes an easement review and acquisition program.
• Section 8.6.2 presents a recommendation that a risk assessment be conducted to evaluate the
vulnerability of Storm Drainage Utility assets.
• Section 8.6.3 presents recommendations for developing and incorporating sustainability goals with
utility activities.
8.6.1 Develop Easement Review and Acquisition Program
As the City implements this Drainage Plan, it needs to develop a process to ensure that it can meet the
LOS goal related to having access to City-owned facilities for M&O activities. While developing this plan, a
number of drainage issues were evaluated in the West Hill area, which was annexed from King County in
2008. The City’s drainage network in this area consists mostly of ditches and culverts. Some of these
are located outside of the right-of-way and cross private property without easements. As the data
inventory for the annexation areas is completed, the City will likely identify more potential easement
gaps. The City should develop a program to identify where easements are needed, and work with the
property owners to obtain easements.
8.6.2 Risk Assessment/Asset Vulnerability Analysis
Asset life-cycle analyses described in Section 8.5 examine risk to individual assets, which focus on small-
scale modes of failure (e.g., pipe breakage). However, Storm Drainage 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 storm 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. The proposed
mitigation measures should be documented in a plan and should be weighed alongside other capital
commitments for prioritization.
8.6.3 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
Storm Drainage Utility activities to emphasize sustainability. The goal associated with this policy is to
identify specific areas to measure sustainability by examining how Storm Drainage Utility operations
affect energy resources, natural resources, and the community. The examples provided include items
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such as weighing energy consumption impacts and costs during capital project development, selecting
biodegradable and locally produced cleaning and maintenance products, protecting or restoring native
soils and vegetation, structuring maintenance and other activities to minimize vehicle miles traveled,
and improving communication with stakeholders and the public. However, quantifying these goals and
effectively using 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 the “hard” costs of capital and M&O are the overriding decision criteria. By more rigorously
including environmental and community benefits and costs in the decision process through sustainability
analyses, projects and utility operations 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 Storm Drainage Utility.
Define Sustainability. Sustainability means different things to different people and organizations. The
United Nations World Commission on Environment and Development defined sustainable development
as “development that meets the needs of the present without compromising the ability of future
generations to meet their own needs.” Sustainable Seattle defines sustainability as the long-term health
and vitality of a region, including the cultural, economic, environmental, and social aspects as one whole.
Sustainability is often described as the careful and efficient use of natural, cultural, and financial
resources in ways that improve the quality of life for communities without depleting the environment. To
develop specific and actionable goals around sustainability, it is important for the Storm Drainage Utility
to develop its own definition of the concept.
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 specific metrics around the specific sustainability
goals it would like to accomplish (e.g., for a goal of minimizing vehicle miles traveled, a specific metric
would be to reduce vehicle travel by 20 percent; or for a goal to protect native vegetation, a specific
metric would be retain and protect 40–60 percent of open space on new development sites).
Establish a Method of Evaluation. Once LOS metrics are defined, projects and activities can be
evaluated, compared, and prioritized. The City should develop or adopt 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, of environmental and community impacts to determine the full cost of
a specific alternative. Such a quantitative approach considers environmental and community risks and
costs, which provides economic support for a decision at the management and policy level.
Other evaluation options could include a sustainability checklist, measuring a project or operations
capacity to meet individual sustainability goals, or tools such as the Institute for Sustainable
Infrastructure Envision rating system, which is a planning and design framework for measuring and
incorporating sustainability into infrastructure projects, or SalmonSafe, which assesses and certifies
projects for water quality protection. These types of tools look beyond monetized costs and benefits to
provide both quantitative and qualitative assessments of the environmental and community impacts of
infrastructure projects. Other sustainability tools and project certification or evaluation processes are
also available, or the City could develop its own evaluation process specific to its sustainability goals and
the Storm Drainage Utility’s projects and operations.
The above-described actions provide a mechanism for incorporating sustainability into Storm Drainage
Utility projects and activities. Investigations are conducted to evaluate projects and activities with
respect to LOS criteria and metrics. Gaps are identified and alternatives are developed for reducing or
eliminating those gaps. Alternatives can be evaluated, compared, and ranked through a life-cycle
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present value benefit/cost analysis, considering not only budgetary impacts but also risks,
environmental considerations, and societal costs and benefits. By applying a repeatable, defensible
process that includes environmental and community factors, the City can prioritize projects and activities
based on both full costs of ownership and a project’s ability to meet or exceed LOS sustainability
requirements.
2016 2017 2018 2019 2020 2021 2022 2035
1. West Main Street Pump Station Upgrade
2. 37th and I Streets NW Storm Improvements
3. Hillside Drainage Assessment
4A. 30th Street NE Area Flooding, Phase 2
4B. 30th Street NE Area Flooding, Phase 3
5A. West Hills Drainage Improvements at S 330th St. & 46th Pl. S
5B. West Hills Drainage Improvements near S 3114th St. & 54th Ave. S
6. North Airport Area Improvements
7. D St. SE Storm Improvements
9. Composting Facility
10. Storm Drainage Infrastructure Repair & Replacement
11. Street Utility Improvements
Q1Q2Q3Q4
Pipe 1011-C1086_1011-C1137
Pipe 1011-C1452_1011-C1453
Culvert 1111-C1469_1111-C1470
Catch basin 1012-C688
Pipe 1012-C690_1012-C689
Pipe 1010-C3_1010-C29
Pipe 1010-B220_1010-B221
WL-Mill-01,02,03,04. Mill Creek Profile
WL-Pond-17thSt. 17th and A Streets SE
WL-Pond-21stSt. 21st and D Streets SE
WL-Pond-RiverN. Riverwalk Dr. SE and U St. SE
WL-Pond-LakeS1, -LakeS2, -LakeEP& -Mill
Detailed 6-year CIP Time Frame
Annual inspections of City-approved facilities constructed under
terms of permit
Adopt 2012 Ecology Manual or equivalent manual
Measure effectiveness of public outreach
En
d
o
f
N
P
D
E
S
Pe
r
m
i
t
Establish specific sustainability goals and standards
Continue system inventory
Conduct new economic life-cycle analyses
Implement economic life-model using Cartegraph data
Implement additional M&O activities
Develop easement review and acquisition program
Remaining 20-year CIP Summary
Q1Q2Q3Q4Q1Q2Q3Q4Q1Q2Q3Q4Q1Q2Q3Q4Q1Q2Q3Q4
IMPLEMENTATION PLAN ACTIVITIES TIMELINE
City of Auburn Comprehensive Storm Drainage Plan
Additional Activities (Section 8.5)
NPDES Compliance (Section 8.3)
Monitoring (Section 8.2)
CIP (Section 8.1)
Data feed
Activity (may start before 2016)
K E Y
Risk assessment/asset vulnerability analysis
Complete one inspection of each catch basin
Review & update operations, maintenance & inspections standards
8. 23rd St. SE Drainage Improvements
Phase 1 Phase 2
Pipe 809-C113_809-C112
Pipe 909-C122_909-C121
Pipe 810-C701_809-C18
Pipe 810-C15_810-C241
Pipe 810-C698_810-C16
Complete field screening for 40% of storm drainage system
Complete field screening for 12% of storm drainage system annually
Revise ACC to reflect IDDE changes
Compile and submit a summary of LID review and revision process
Post SWMP documents to website annually
Review, revise & adopt local development codes, standards, &
policies to require LID
Phase 1 Phase 2
Timing dependent on project to
be implemented in 2015
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Chapter 9
Finance
The objective of the financial plan is to identify the total cost of providing storm drainage service and to
provide a financial program that allows the Storm Drainage Utility to remain financially viable during
execution of the identified CIP. This viability analysis considers the historical financial condition of the
Storm Drainage Utility, the sufficiency of Storm Drainage U tility revenues to meet current and future
financial and policy obligations, and the financial impact of executing the CIP. Furthermore, the financial
plan provides a review of the Storm Drainage Utility’s rate structure with respect to rate adequacy and
customer affordability.
Past Financial Performance 9.1
This section includes a historical (2008–13) summary of financial performance as reported by the City of
Auburn on the statement of revenues, expenses, and changes in net position and the statement of net
position, specific to the Storm Drainage Utility.
9.1.1 Statement of Revenues, Expenses, and Changes in Net Position
Table 9-1 shows a consolidated statement of revenues, expenses, and changes in net position for the
period 2008–13.
Operating income (including depreciation expense) was positive in 2010, 2011, and 2013. Operating
income grew from an operating loss of $29,000 in 2008 to an operating income of $863,000 in 2013.
Furthermore, from 2008 to 2013 operating revenues grew by over $3 million, which represents a 59
percent increase. This increase outpaced operating expenses by 18 percent. Depreciation is a non-cash
expenditure, so even though operating income has been negative in some years, operating cash flow
was positive every year.
A few key financial ratios are discussed below. Unless otherwise noted, the stated benchmarks are
based on industry standards.
• M&O coverage ratio (operating revenues divided by operating expenses):
− Benchmark: A ratio of 1.0 or higher is a desirable result, indicative of sufficient revenues to
meet cash operating expenses as well as to cover depreciation expense.
− Results: From 2008 through 2013, the ratio has ranged from 0.9 to 1.1, which is a positive
result overall.
• Operating ratio (total operating expenses excluding depreciation divided by total operating
revenues):
− Benchmark: A ratio greater than 90 percent indicates that there is little room for new debt
service and capital replacement without additional rate increases. A ratio greater than 100
percent indicates that cash operating expenses exceed operating revenues and is indicative of
an unsustainable financial condition.
− Results: From 2008 through 2013, the ratio has ranged from 71 percent to 86 percent, which is
a positive result in every year.
• Debt service coverage ratio (operating and interest revenues less M&O expenses excluding
depreciation, divided by annual debt service):
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− Benchmark: Revenue bonds typically have a legal minimum coverage requirement of 1.25.
− Results: From 2008 through 2013, the coverage ratio has ranged from 3.2 to 10.8, each year
well above the benchmark. The Storm Drainage Utility has used revenue bond debt only in this
historical period; state loans have not been used.
Table 9-1. Statement of Revenues, Expenses and Changes in Fund Net Position
9.1.2 Statement of Net Position
Table 9-2 shows the consolidated statement of net position for the period 2008–13.
Table 9-2. Statement of Net Position
Table 9-1. Statement of Revenues, Expenses and Changes in Fund Net Position
200820092010201120122013
OPERATING REVENUES:
Charges for services 5,159,389$ 6,000,761$ 6,441,726$ 6,938,375$ 7,479,580$ 8,184,303$
Other Operating Revenue 997 102 272 - - -
Total Operating Revenues 5,160,386 6,000,863 6,441,998 6,938,375 7,479,580 8,184,303
OPERATING EXPENSES:
Operations and Maintenance 1,551,406 2,186,976 1,727,711 1,923,604 3,123,618 2,113,050
Administration 1,979,083 2,298,330 2,428,345 2,746,980 2,641,157 2,919,570
Depreciation/Amortization 1,241,980 1,087,555 1,088,529 1,278,402 1,456,342 1,529,701
Other Operating Expenses 417,130 535,284 585,743 646,871 704,221 759,178
Total Operating Expenses 5,189,599 6,108,145 5,830,328 6,595,857 7,925,338 7,321,499
OPERATING INCOME(LOSS)(29,213) (107,282) 611,670 342,518 (445,758) 862,804
NON OPERATING REVENUE (EXPENSES)
Interest Revenue 295,975 60,479 47,875 20,865 18,299 20,944
Other Non-Operating Revenue 77,300 1,047,703 172,791 511,617 803,570 356,010
Interest Expense (37,224) (25,120) (271,964) (133,448) (99,496) (351,913)
Other Non-Operating Expenses - (1,141,807) (892,089) (22,716) (895) (53,055)
Total Non-Operating Revenue (expenses)336,051 (58,745) (943,387) 376,318 721,478 (28,014)
INCOME(LOSS) BEFORE CONTRIBUTIONS AND
TRANSFERS 306,838 (166,027) (331,717) 718,836 275,720 834,790
CAPITAL CONTRIBUTIONS 920,944 750,141 1,727,140 6,193,834 1,966,564 1,033,128
TRANSFERS IN - - - - -
TRANSFERS OUT (159,100) (138,000) (59,580) (96,800) (50,000) (124,000)
Changes in Net Position 1,068,682 446,114 1,335,843 6,815,870 2,192,284 1,743,918
Net Position, January 1, as Previously Reported 38,105,695 39,174,377 39,620,491 40,956,334 47,772,204 49,964,488
Change in Accounting Principle (21,471)
Net Position, January 1, as Restated - - - - - 49,943,017
Net Position, December 31 39,174,377 39,620,491 40,956,334 47,772,204 49,964,488 51,686,935
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Table 9-2. Statement of Net Position
2008200920102011 20122013
ASSETS
Current Assets
Cash and Cash Equivalents 6,328,751$ 3,902,561$ 2,783,583$ 6,693,599$ 7,954,723$ 8,894,035$
Investments 1,052,500 1,017,813 2,510,325 - - 997,290
Restricted Cash
Bond Payments 442,329 95,746 348,279 357,864 473,264 829,406
Customer Deposits - - - - - -
Other 479,991 425,608 4,451,444 2,128,832 1,413,688 5,726,428
Customer Accounts 720,823 733,644 795,710 855,486 923,999 931,782
Other Receivables 4,521 4,521 4,627 - - 955
Due From Other Governmental Units - 1,019,200 90,608 444,779 705,853 222,677
Inventories 8,764 11,831 7,880 7,299 5,533 7,566
Total Current Assets 9,037,679 7,210,924 10,992,456 10,487,859 11,477,060 17,610,139
Non Current Assets
Long Term Contracts and Notes - - - - - -
Capital Assets
Land 5,686,254 5,686,254 5,686,254 5,686,254 5,686,254 5,686,254
Buildings and Equipment 201,255 297,853 201,254 201,254 201,254 219,214
Improvements Other Than Buildings 38,271,397 38,697,313 44,739,930 50,815,888 55,581,417 56,162,320
Construction in Progress 808,357 4,027,852 755,866 3,403,168 1,083,761 2,922,064
Less: Accumulated Depreciation (12,887,006) (13,974,561) (15,057,455) (16,335,857) (17,792,199) (19,321,900)
Total Capital Assets ( Net of A/D)32,080,257 34,734,711 36,325,849 43,770,707 44,760,487 45,667,952
Total Non-Current Assets 32,080,257 34,734,711 36,325,849 43,770,707 44,760,487 45,667,952
Total Assets 41,117,936 41,945,635 47,318,305 54,258,566 56,237,547 63,278,091
LIABILITIES
Current Liabilities
Current Payables 218,480 931,383 333,818 522,001 393,826 657,995
Current Deposits - - - - - -
Loans Payable-Current - - - - - -
Employee Leave Benefits-Current 92,777 143,232 122,244 136,131 149,928 168,396
Revenue Bonds Payable-Current 398,500 71,500 75,400 79,300 198,705 405,186
General Obligation Bonds Payable-Current - - - - -
Accrued Interest 43,829 24,246 272,879 278,564 274,559 424,221
Deposits - - - - - -
Total Current Liabilities 753,586 1,170,361 804,341 1,015,996 1,017,018 1,655,798
Non Current Liabilities
Unearned Revenue 597,204 597,204 597,204 597,204 597,204 597,204
Employee Leave Benefits 11,443 47,338 63,911 61,793 52,017 50,214
Loans Payable - - - - - -
Revenue Bonds Payable 581,326 510,241 4,896,515 4,811,369 4,606,820 9,287,940
General Obligation Bonds Payable - - - - - -
Total Non Current Liabilities 1,189,973 1,154,783 5,557,630 5,470,366 5,256,041 9,935,358
Total Liabilities 1,943,559 2,325,144 6,361,971 6,486,362 6,273,059 11,591,156
NET ASSETS
Invested In Capital Assets, Net of Related Debt 31,100,432 34,152,970 34,942,276 40,145,011 40,504,264 35,974,826
Restricted for:
Debt Service 179,991 221,354 800,751 810,336 925,485 1,605,820
Capital Projects - - - - - 4,537,224
Rate Stabilization - 300,000 410,629 411,386 412,165 412,791
Unrestricted 7,893,954 4,946,167 4,802,678 6,405,471 8,122,574 9,156,274
Total Net Position 39,174,377$ 39,620,491$ 40,956,334$ 47,772,204$ 49,964,488$ 51,686,935$
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This statement shows that the City’s net storm drainage assets, which measures the cost of assets (net
of depreciation) remaining after liabilities are paid, increased from $39.2 million to $51.7 million over
the 2008–13 time period; this represents a 32 percent increase. This includes an overall increase in the
current assets from $9 million in 2008 to $17.6 million in 2013, which represents a 95 percent
increase. Cash and cash equivalents have increased by $2.6 million over this same period.
Non-current assets, which represent assets required for use or consumption beyond 1 year, have seen a
42 percent increase, from $32.1 million in 2008 to $45.7 million in 2013. A more detailed look at the
change in capital assets over this period reveals that improvements other than buildings have increased
by nearly $18 million, which represents a 47 percent increase. Construction in progress has increased
by $2.1 million during this same time period.
A few key financial ratios are discussed below. Unless otherwise noted, the stated benchmarks are
based on industry standards.
Liquidity
• Current ratio (unrestricted current assets divided by current liabilities):
− Benchmark: A ratio of 2.0 or higher is considered good in terms of healthy liquidity. The current
ratio is a measure of short-term financial strength and answers the question: Are current assets
able to cover expected current liabilities in the coming year?
− Results: From 2008 through 2013, the current ratio has ranged from 4.2 to 9.8, well above the
recommended benchmark in each year.
Efficiency
• Accounts receivable collection period (customer receivables on balance sheet x 365 days then
divided by annual sales):
− Benchmark: Generally, less than 30 days is considered very good.
− Results: Decreased from 51 days in 2008 to 42 days in 2013. This is a positive trend.
Capital Structure
• Debt to net capital assets ratio (total outstanding debt divided by capital assets net of accumulated
depreciation):
− Benchmark: For utilities, having a capital structure of at least 40 percent equity and less than
60 percent debt is considered a healthy capital structure, with adequate future borrowing
capacity and a manageable debt service burden. The City’s capital structure policy is even more
conservative: 50 percent debt and 50 percent equity.
− Results: Increased from 3 percent debt in 2008 to 21 percent debt in 2013. The ratio increased
from 11 percent in 2012 to 21 percent in 2013 resulting from the 2013 CIP Revenue Bond.
Despite this increase, this ratio is still well within both the industry and City benchmarks for
maximum outstanding debt.
9.1.3 Outstanding Debt Principal
Table 9-3 outlines the City’s outstanding debt principal as of the end of 2013.
The Storm Drainage Utility has three outstanding revenue bonds. The total outstanding principal on
these bonds is $9.2 million.
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Table 9-3. Outstanding Debt
Available Capital Funding Resources 9.2
Feasible long-term capital funding strategies should be defined to ensure that adequate resources are
available to fund the CIP identified in this Plan. In addition to the Storm Drainage 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 other debt financing. The following is a
summary of internal Storm Drainage Utility resources, government programs and resources, and public
debt financing.
9.2.1 Internal Utility Resources
Storm Drainage Utility resources appropriate for funding capital needs include accumulated cash in the
capital “account,” bond proceeds, and capital revenues, such as SDCs. Capital-related revenues are
discussed below.
9.2.1.1 Utility Funds and Cash Reserves
User charges (rates) paid by the Storm Drainage Utility’s customers are the primary funding source for all
Storm Drainage Utility activities. The rates cover total annual costs associated with operating and
maintaining the system. Rates can pay for capital improvement projects in two ways: either paying for
debt service or directly paying for capital projects. Although funding the capital costs directly through
rates does not result in the additional interest expense associated with issuing debt, this approach can
cause large and/or volatile rate increases.
9.2.1.2 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 Storm Drainage Utility system. The purpose of the SDC is twofold: (1) to
promote equity between new and existing customers, and (2) to provide a source of revenue to fund
capital projects. Equity is served by providing a vehicle for new customers to share the cost of
infrastructure investment. SDC revenues provide a source of cash flow used to support Storm Drainage
Utility capital needs; revenue can be used only to fund Storm Drainage 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 Storm Drainage 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.
Table 9-4 summarizes the City’s current SDC schedule.
Table 9-3. Outstanding Debt
Debt Description Principal
Outstanding Maturity Year
2005 Refinance Revenue Bond 265,200$ 2016
2010 CIP Revenue Bonds 4,255,888$ 2030
2013 CIP Revenue Bonds 4,653,600$ 2032
Total 9,174,688$
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Table 9-4. Current System Development Charge Schedule
9.2.1.3 Local Facilities Charge
While an SDC is the manner by which new customers pay their share of general facilities costs, local
facilities funding is used to pay the cost of local facilities that connect each property to the system
infrastructure. Local facilities funding is often overlooked in a rate forecast because it is funded up front
either by connecting customers or 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, a discussion of these charges is included in this chapter because of their impact on new
customers.
Several mechanisms can be considered toward funding local facilities. One of the following scenarios
typically occurs:
• The Storm Drainage 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 its development and turns those facilities over to the
Storm Drainage 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, as such, can accumulate up to 10 years of interest. It
typically applies in instances where no developer-installed facilities are needed through developer
extension because of 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.
Latecomer charges are a variation of developer extensions whereby a new customer connecting to a
developer-installed improvement makes a payment to the city based on their share of the developers
cost (RCW 35.91.020). The city passes this on to the developer that 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 is in effect
for a period of 20 years, unless a longer duration is approved by the city.
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 process relatively expensive, and there are mechanisms by which a ULID
Table 9-4. Current System Development Charge Schedule
Type SDC
Single Family Residences & Duplexes (on Individual Parcels)$1,162 per Parcel
Other Parcels $1,162 per Equivalent Service Unit
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can be rejected by a majority of property ownership within the assessment district boundary. These
instruments are not often used to finance storm drainage facilities because it has proved difficult to
demonstrate required special benefit to properties to be assessed.
9.2.2 Government Programs and Resources
This section outlines government programs and resources potentially available for financing.
9.2.2.1 Grants and Low-Cost Loans Overview
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, even the benefit of low-interest loans
makes the effort of applying worthwhile. Grants and low-cost loans for Washington State utilities are
available from various Washington State departments. Several grant and loan programs for which the
City might be eligible are described in greater detail below.
9.2.2.2 Department of Commerce
A September 2014 document from the Washington State Department of Commerce summarizes various
loan and grant programs available for storm drainage projects (“Summary of Some Grant and Loan
Programs for Drinking Water and Wastewater Projects,” found at
http://www.commerce.wa.gov/Documents/9-2-14_multi-program_funding_program_summary.pdf.
A few of those programs are described below.
Community Economic Revitalization Board (CERB). CERB, a division of the Washington State
Department of Commerce, offers primarily 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 for job creation and retention. Priority criteria include
unemployment rates, number of jobs created and/or retained, wage rates, projected private investment,
and estimated state and local revenues generated by the project. According to its website, “CERB funds
a variety of projects that create jobs including (but not limited to) domestic and industrial water, storm
and sewer water projects, telecommunications and port facilities.” Eligible applicants include cities,
towns, port districts, special purpose districts, federally recognized Indian tribes, and municipal
corporations.
Funding details for the 2013–15 Program are as follows per the Washington Commerce Department
website: “$9 million was appropriated to CERB for the 2013–15 Biennium. By state law, CERB must
award 75 percent of this funding to projects in rural counties. The Board has also allocated $2,182,500
to be available for construction and planning grants on a first-come, first-served basis.”
Program Funding Limitations
Committed Private Sector Partner
Construction
• $2 million per project load award limit
• Up to $300,000 or 50% of total award, whichever is less, may be grant funds.
• 20% cash match required (minimum, percent of total project cost)
Prospective Development
Construction
Available to rural communities only.
• $2 million per project load award limit
• Up to $300,000 or 50% of total award, whichever is less, may be grant funds.
• 20% cash match required (minimum, percent of total project cost)
Planning/Economic Feasibility
Studies
• $50,000 grant per project award limit
• 25% cash match required (minimum, percent of total project cost)
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Further details are available at:
• http://www.commerce.wa.gov/commissions/CommunityEconomicRevitalizationBoard/
• http://www.commerce.wa.gov/Documents/2013-15_Policies.pdf
• http://www.commerce.wa.gov/commissions/CommunityEconomicRevitalizationBoard/Pages/CERB-
Traditional-Programs.aspx
Public Works Board (PWB) Financial Assistance. The PWB’s goal is to provide community access to
financial and technical resources that help sustain local infrastructure. Cities, towns, counties, and
special-purpose districts are eligible to receive financial assistance for qualifying projects. When funding
is available, the following tools are accessible:
• Construction Loan Program (http://www.pwb.wa.gov/financial-
assistance/Construction/Pages/default.aspx):
− Funding cycle: Per the PWB website, the governor’s proposed 2015–17 budget offers $69.7
million for 19 projects.
− Program description: Low-interest loans for local governments to finance public infrastructure
construction and rehabilitation. Eligible projects must improve public health and safety, respond
to environmental issues, promote economic development, or upgrade system performance.
− Terms: For non-distressed communities, a term of 5 years or less has an interest rate of 1.28
percent and a term from 6 to 20 years has an interest rate of 2.55 percent.
• Pre-Construction Loan Program (http://www.pwb.wa.gov/financial-assistance/Pre-
Construction/Pages/default.aspx):
− Funding cycle: No funding has been allocated to the pre-construction loan program for the
2013–15 biennium.
− Program description: Local governments may apply for low-interest loans to finance pre-
construction activities to prepare a project for construction.
− Terms: Terms are limited to a 5-year repayment period (the loan term may be converted to 20
years once the project has secured construction funding) with a 1 percent interest rate.
• Emergency Loan Program (http://www.pwb.wa.gov/financial-assistance/Emergency-
Loan/Pages/default.aspx):
− Funding cycle: No funding has been allocated to the Emergency Loan Program for the 2013–15
biennium.
− Program description: The Emergency Loan Program provides funding to address public-works
emergencies, thereby helping to provide immediate restoration of critical public-works services
and facilities.
− Terms: Funds are limited to $500,000 per jurisdiction per biennium, and come with a 20-year
term (or the life of the project), and a 3 percent interest rate. No local match is required.
• Energy and Water Efficiency (EWE) Loan Program (http://www.pwb.wa.gov/financial-
assistance/Energy-Water/Pages/default.aspx):
− Funding cycle: No funding has been allocated to the EWE Loan Program for the 2013–15
biennium.
− Program description: The EWE Loan Program is designed to encourage energy, water, and
efficiency upgrades to existing infrastructure by providing low-cost loans.
− Terms: The maximum loan amount is $1 million. The interest rate is dependent upon the term of
the loan. Loans less than 5 years receive a 0.50 percent interest rate. Loans between 5 and 10
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years receive a 1 percent interest rate. Loans between 11 and 20 years receive a 1.50 percent
interest rate.
• Further general resources are available at:
− http://www.pwb.wa.gov/financial-assistance/Pages/default.aspx
− http://www.pwb.wa.gov/Documents/FINAL-MASTER-GUIDELINES.pdf
− http://www.commerce.wa.gov/Documents/9-2-14_multi-
program_funding_program_summary.pdf
9.2.2.3 Department of Ecology: Integrated Water Quality Funding Program
This year, Ecology received 227 applications requesting more than $352 million in financial assistance.
Ecology is proposing grant and loan funding for 165 projects totaling approximately $229 million.
• State Water Pollution Control Revolving Fund and Centennial Clean Water Program
− Design projects associated with publicly owned wastewater and stormwater facilities. The
integrated program also funds planning and implementation of nonpoint source pollution control
activities. Terms for State fiscal year 2016 include either 2.4 percent interest for 6–20-year
term or 1.2 percent for 5-year term loans. Forgivable loan principal terms are available for
distressed communities.
− Further general resources are available at:
http://www.ecy.wa.gov/programs/wq/funding/cycles/FY2016/index.html
• Stormwater Financial Assistance Program (SFAP)
− Stormwater grant assistance is available for projects not required by permit. The SFAP is
available for both cities and counties. The maximum grant award per jurisdiction is $250,000.
− Further general resources are available at:
• http://www.ecy.wa.gov/programs/wq/funding/FundPrgms/OthPrgms/StWa12a/FY12aStW
a.html
• http://www.ecy.wa.gov/programs/wq/funding/Training/FY2016/SFY16ApplicantStormwate
rSession.pdf
9.2.3 Public Debt Financing
This section describes potentially available public debt financing tools.
9.2.3.1 General Obligation Bonds
General obligation (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:
(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.
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(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.
9.2.3.2 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.
9.2.4 Capital Resource Funding 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 Storm Drainage Utility’s available cash
resources. GO bonds may be useful for special circumstances, but because bonding capacity limits are
most often reserved for other City (non-Storm Drainage Utility) purposes, revenue bonds are a more
secure financing mechanism for Storm Drainage Utility needs. The capital financing strategy developed
to fund the updated CIP follows the funding priority below:
1. Available grant funds and/or developer contributions
2. Interest earnings on allocated fund balances
3. Other miscellaneous capital resources
4. Annual revenue collections from SDCs
5. Annual transfers of rate-funded capital or excess cash (above minimum balance targets) from
operating accounts
6. Accumulated capital cash reserves
7. Revenue bond financing
Financial Plan 9.3
The Storm Drainage Utility is an enterprise fund that is responsible for funding all of its related costs. It is
not dependent upon general tax revenues or General Fund resources. The primary source of funding for
the Storm Drainage Utility is collections from service charges. The City controls the LOS charges by
ordinance and, subject to statutory authority, can adjust user charges as needed to meet financial
objectives.
The financial plan can provide a qualified assurance of financial feasibility only if it considers the “total
system” costs of providing service—both operating and capital. To meet these objectives, the following
elements are completed:
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• Capital funding plan: The capital funding plan identifies the total CIP obligations for the capital
planning period 2014–35, although the Storm Drainage Utility’s capital plan in this Drainage Plan
begins in 2016. 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 use of debt financing (resulting in annual debt service) and the
assumed rate revenue resources available for capital funding. The capital funding plan is discussed
in Section 9.3.3.
• Financial forecast: This forecast identifies annual non-capital costs associated with the operation,
maintenance, and administration of the 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 Storm Drainage Utility revenues in meeting all obligations, including operating
expenses, debt service, and reserve contributions, as well as any debt service coverage
requirements associated with long-term debt. The financial forecast analysis is discussed in Section
9.4.
9.3.1 Utility Fund Structure
The City tracks the Storm Drainage Utility’s revenues and expenditures in a single fund: Fund 432.
Conceptually, Storm Drainage Utility expenditures can be divided into three main types of costs:
operating, capital, and debt service. For modeling purposes, it was assumed that the single fund for the
Storm Drainage Utility is split among three “accounts”: operating, capital, and debt reserves). Municipal
utilities commonly maintain separate operating, capital, and debt reserves. The initial allocation of the
beginning fund balance is discussed in Section 9.4.
• Operations: Serves as an operating account where operating revenues are deposited and operating
expenses are paid.
• Capital projects: Serves as a capital account where capital revenues are deposited and capital
expenditures are paid. Examples of capital revenues include SDCs, grant proceeds, debt proceeds,
and contributions from rates.
• Restricted bond reserve: Serves as a restricted account set up to comply with revenue bond
covenants.
Splitting a single fund into three separate “accounts” allows the City to apply the City’s and industry
standard reserve targets to each account. Minimum balance thresholds for these accounts are
discussed in Section 9.3.2 below.
9.3.2 Financial Policies
A brief summary of adopted or recommended financial policies for the Storm Drainage Utility is provided
below. Adopted policies are drawn from the “Process/Policies” section within the City’s Adopted 2015–
16 budget.
9.3.2.1 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.
• Operating reserve: An operating reserve is designed to provide a liquidity cushion; it protects the
utility from the risk of short-term variation in the timing of revenue collection or payment of
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expenses. Like other types of reserves, operating reserves also serve another purpose: they help to
smooth rate increases over time. Target funding levels for an operating reserve are generally
expressed as a certain number of days of M&O expenses, with the minimum requirement varying
with the expected revenue volatility. Industry practice for utility operating reserves ranges from 30
days (8 percent) to 120 days (33 percent) of M&O expenses, with the lower end more appropriate
for utilities with stable revenue streams and the higher end of the range more appropriate for
utilities with significant seasonal or consumption-based fluctuations.
The City’s adopted policy states that the Storm Drainage Utility’s target operating reserves should be
approximately 60 days (page 36, “Process/Policies”). This is the target assumed in the financial
forecast. Based on the City’s 2015 budgeted expenditures (excluding depreciation), a 60-day target
equates to $1.2 million.
• Capital contingency reserve: A capital contingency reserve is cash set aside in case of an emergency
should a piece of equipment or a portion of the Storm Drainage Utility’s infrastructure fail
unexpectedly. The reserve could also be used for other unanticipated capital needs, including capital
project cost overruns. Various approaches are used in the industry to set an appropriate level for this
reserve, such as (1) choosing a percentage of a utility system’s total fixed assets, or (2) determining
the cost of replacing highly critical assets or facilities. Following common industry practice, this
analysis assumes a minimum capital fund balance equal to 1 percent of the original cost of plant in
service.
• 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. A reserve amount equal to
annual debt service is targeted.
9.3.2.2 System Reinvestment Policies
The purpose of system reinvestment funding is to provide for the ongoing rate funding for the
replacement of system facilities. Each year, the Storm Drainage Utility assets lose value, and as they lose
value they are moving toward eventual replacement. That accumulating loss in value and future liability
is typically measured for reporting purposes through annual depreciation expense. This is based on the
original cost of the asset divided by 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, after factoring in inflation and construction conditions. Therefore, the added annual
replacement liability is often even greater than the annual depreciation expense. It is prudent to
establish a system reinvestment policy that attempts to recover at least a portion of the annual
depreciation expense from rate funding. Providing a certain amount of rate-funded capital reinvestment
is an approach to ensure that the system does not become too heavily dependent on debt.
The City’s adopted policy is to phase in system reinvestment funding over 10 years in 10 percent
increments beginning in 2012. To keep rates at their currently adopted levels through 2017, the system
reinvestment strategy for the financial plan begins in 2015 at 40 percent and increases by 10 percent
per year until 100 percent of the target is funded.
9.3.2.3 Debt Policies
Revenue bond covenants typically establish a minimum debt service coverage as a way to protect
bondholders against the risk of nonpayment. City policy and the City’s current bond covenants both
require bonded debt service coverage of 1.25.
The City also has another debt-related policy, which is to maintain a capital structure that does not
exceed 50 percent debt. This is more conservative than the typical industry standard of 60 percent debt
and 40 percent equity. The City’s capital structure from the 2013 financial statement was well below the
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threshold at 21 percent debt and 79 percent equity. This forecast projects that the debt level will be 13
percent by 2021, remaining well within the industry-standard limit of 60 percent debt and 40 percent
equity.
9.3.3 Capital Funding Plan
The CIP developed for this Drainage Plan contains 14 different projects valued at $25 million ($34
million in inflated dollars) over the 2016–35 planning period (excluding the 2014 estimated and 2015
budgeted capital figures). Costs are stated in 2014 dollars and are escalated to the year of planned
spending at an annual inflation rate of 3.5 percent per year.
Table 9-5 summarizes the expected annual capital expenditures, using 2014 estimated and 2015
budgeted capital expenditures.
Table 9-5. Drainage CIP
A capital funding plan is developed to identify the total resources available to pay for the CIP and
determine if new debt financing is required. After allocating the estimated beginning 2015 fund balance
first to the debt reserve and secondly to the operating reserve, more than $8.6 million was available for
capital.
The SDC is projected to generate an average annual revenue stream of roughly $800,000. This is based
on an assumed ESU growth rate of 1 percent per year. The growth percentage is drawn from a 2012
analysis provided by the City’s storm drainage engineer, who projected ESUs through 2018. An account
growth of 1.8 percent is used in the rate revenue projection in the financial forecast. Using an ESU
growth rate that is lower than customer account growth is a reasonable and conservative assumption
after evaluating historical SDC revenues.
The SDC revenue projection assumes the current SDC of $1,162 plus an annual Construction Cost Index
adjustment starting in 2016.
Table 9-6 summarizes the capital funding plan.
Table 9-5. Drainage CIP
Year 2014 $Inflated $
20149,154,705$ 9,154,705$
20154,964,848$ 5,138,618$
20164,133,000$ 4,427,373$
20172,896,000$ 3,210,847$
20182,773,500$ 3,182,655$
20193,247,100$ 3,856,536$
2020828,300$ 1,018,192$
20211,442,100$ 1,834,754$
8 Year Total 29,439,553$ 31,823,680$
2022-20359,633,800$ 16,197,872$
Grand Total 39,073,353$ 48,021,552$
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Table 9-6. Capital Financing Plan
Financial Forecast 9.4
The financial forecast, or revenue requirement analysis, forecasts the amount of annual rate revenue
needed throughout the 2014–21 planning horizon. The analysis incorporates operating revenues, M&O
expenses, debt service payments, rate-funded capital needs, and any other identified revenues or
expenses related to Storm Drainage 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 Storm Drainage Utility. For this analysis, two
revenue sufficiency “tests” have been developed to reflect the financial goals and constraints of the
Storm Drainage Utility: (1) cash needs must be met, and (2) debt coverage requirements must be
realized. In order to operate successfully with respect to these goals, both tests of revenue sufficiency
described below must be met.
9.4.1 Cash Test
The cash flow test identifies all known cash requirements for the Storm Drainage 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 Storm Drainage Utility are then compared to total operating
revenues (under current rates) to forecast annual revenue surpluses or shortfalls.
9.4.2 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 Storm Drainage 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 revenues must be sufficient to pay M&O
Table 9-6. Capital Financing Plan
Year Capital
Expenditures
Capital
Expenditures
Inflated
Revenue Bond
Financing Cash Funding Total Financial
Resources
20149,154,705$ $ 9,154,705 $ - 9,154,705$ $ 9,154,705
20154,964,848 5,138,618 - 5,138,618 5,138,618
20164,133,000 4,427,373 - 4,427,373 4,427,373
20172,896,000 3,210,847 - 3,210,847 3,210,847
20182,773,500 3,182,655 492,824 2,689,831 3,182,655
20193,247,100 3,856,536 1,858,962 1,997,574 3,856,536
2020828,300 1,018,192 - 1,018,192 1,018,192
20211,442,100 1,834,754 - 1,834,754 1,834,754
8-Year Total 29,439,553$ 31,823,680$ 2,351,786$ 29,471,893$ 31,823,680$
2022-20359,633,800$ 16,197,872$ -$ 16,197,872$ 16,197,872$
Grand Total 39,073,353$ 48,021,552$ 2,351,786$ 45,669,766$ 48,021,552$
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expenses, 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 Storm Drainage Utility purpose, including funding capital projects. The existing coverage
requirement policy 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.
The financial forecast projects the amount of operating and capital expenditures to determine the
annual amount of revenue required. The objective of the financial forecast is to evaluate the sufficiency
of the current level of rates in meeting the total revenue requirements of the system. In addition to
annual operating costs, the revenue of the Storm Drainage Utility must also meet debt covenant
requirements and minimum reserve level targets.
9.4.3 Financial Forecast Assumptions
The financial forecast is developed from the City’s adopted 2015–16 biennial budget documents along
with other key factors and assumptions to develop a complete portrayal of the Storm Drainage Utility’s
annual financial obligations. The forecast covers the 2014–21 planning period. The following is a list of
the key revenue and expense factors and assumptions used to develop the forecast:
9.4.3.1 Revenue and Fund Balance
The following revenue and fund balance assumptions are used to develop the forecast:
• Customer growth: Based on a review of 5 years of historical data, annual customer account growth
has been 1.8 percent per year.
• Adopted rate increases: The City adopted annual rate increases through 2017 of roughly 2.5
percent, which are incorporated into the revenue figures in the forecast. The analysis shows that
through 2017, no additional rate increases are needed above the adopted levels.
• Miscellaneous revenues are conservatively assumed to stay at their currently budgeted levels.
Miscellaneous revenues include late penalties, applications, etc. The Build America Bonds (BAB)
subsidy for the 2010 Revenue Bond is expected to gradually decline in proportion to the annual
decline in interest expense.
• Fund balances are based on the budgeted beginning balance in 2015. Depending on resource
availability, the balance was allocated to the “accounts” using the following methodology:
− Debt reserve: amount equal to highest annual debt service on existing debt
− Operating reserve: amount equal to the operating reserve target of 60 days
− Capital reserve: remaining funds
The estimated beginning fund balance in 2015 was approximately $10.6 million, which is enough to
fully fund the debt reserve, provide 60 days in the operating reserve, and provide over $8.6 million in
the capital reserve.
• Interest earnings initially assume a rate of 0.09 percent applied to the beginning of year cash
balances based on existing Local Government Investment Pool rates, phasing toward 0.25 percent
over the long term.
9.4.3.2 Expenditures
The following expenditure assumptions are used to develop the forecast:
• General operating expenses are escalated from the budgeted figures at 2.5 percent per year, labor
costs at 2.5 percent per year, and benefits at 5.5 percent per year.
• State taxes are calculated based on prevailing tax rates.
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• Existing debt service schedules were provided by the City and include three existing revenue bond
issues. These obligations represent nearly $795,000 in annual debt service principal and interest
payments in 2015.
• This Drainage Plan identifies additional staffing levels and equipment purchases needed above the
2015 and 2016 budgeted levels. The additional staff is needed for NPDES compliance activities,
which include LID facility inspection, maintenance tracking, and public education and outreach.
− Full-time engineering staff with salaries plus benefits totaling $107,000 starting in 2017 and
continuing throughout the study period.
− Full-time system maintenance staff with salaries and benefits totaling $320,000 starting in
2017 and continuing throughout the study period. This includes a 50 percent share of the asset
management specialist to be shared with the Sewer Utility.
− One-time equipment purchases in 2017 consisting of CCTV inspection equipment for $250,000
and an excavator for $180,000.
• Future debt service has been added as outlined in the capital funding plan. The forecast assumes a
revenue bond interest rate of 4.30 percent based on prevailing rates, as well as an issuance cost of
1 percent with a 20-year term. City policy dictates a minimum debt service coverage requirement of
1.25.
The City should review the proposed rates and rate assumptions annually to ensure that the rate
projections developed remain adequate. Any significant changes should be incorporated into the
financial plan and future rates should be adjusted as needed.
Table 9-7 summarizes the annual revenue requirement for the 2014–21 planning horizon based on the
forecast of revenues, expenditures, fund balances, fiscal policies, and capital funding.
Table 9-7. Financial Forecast
Table 9-7. Financial Forecast
Revenue Requirements 20142015201620172018201920202021
Assuming Existing Rates:
Revenue
Rate Revenues 8,727,224$ 9,106,422$ 9,502,096$ 9,914,962$ 10,093,431$ 10,275,113$ 10,460,065$ 10,648,346$
Non-Rate Revenues 2,133,878 960,113 176,479 173,808 171,731 169,614 167,462 164,803
Total Revenue 10,861,102$ 10,066,535$ 9,678,575$ 10,088,770$ 10,265,162$ 10,444,727$ 10,627,527$ 10,813,149$
Expenses
Cash Operating Expenses 7,000,356$ 7,323,914$ 7,249,903$ 8,342,836$ 8,151,980$ 8,399,583$ 8,656,021$ 8,921,664$
Existing Debt Service 796,781 795,239 777,111 774,579 776,275 776,413 774,467 774,396
New Debt Service - - - - 40,716 194,299 194,299 194,299
Rate-Funded System Reinvestment - 550,558 734,017 940,032 1,120,686 1,268,271 1,479,931 1,646,473
Additions to Operating Reserve - - - - 120,221 40,702 38,266 47,555
Total Expenses 7,797,136$ 8,669,711$ 8,761,031$ 10,057,448$ 10,209,877$ 10,679,269$ 11,142,985$ 11,584,387$
Cash Surplus / (Deficiency) Before Rate Increases 3,063,965$ 1,396,824$ 917,544$ 31,322$ 55,285$ (234,542)$ (515,458)$ (771,238)$
Annual Rate Adjustment 0.00%0.00%0.00%0.00%2.49%2.82%2.40%
Cumulative Annual Rate Adjustment 0.00%0.00%0.00%0.00%2.49%5.39%7.92%
After Rate Increases:
Rate Revenues 8,727,224$ 9,106,422$ 9,502,096$ 9,914,962$ 10,093,431$ 10,531,443$ 11,023,407$ 11,491,230$
Cash Surplus / (Deficiency) After Rate Increases 3,064,000 1,396,800 917,500 31,300 175,500 40,700 38,300 47,600
Debt Service Coverage - Revenue Bonds 5.694.343.993.253.543.173.403.61
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The last row of Table 9-7 shows the projected debt service coverage for bonded debt. Bonded debt
service coverage—which legally cannot drop below 1.25—is projected to stay at or above 3.17 throughout
the life of the forecast.
In 2012, the City Council adopted annual rate increases of 2.5 percent in 2015, 2016, and 2017. This
analysis shows that the adopted rates will generate sufficient revenue to meet operating expenses and
the Storm Drainage Utility policy goals as discussed herein for the 2015–17 period. Based on the
assumptions in the forecast, no incremental rate increases (above adopted amounts) are needed
through 2017.
Based on the financial forecast, no rate increase is needed in 2018. Rate increases averaging about 2.6
percent per year are needed in 2019 and beyond to cover projected M&O expenses, debt service
payments, system reinvestment funding, and other stated financial policy objectives. While no rate
increase is projected in 2018, it may be prudent to adopt a smaller set of increases over 4 years (2018–
21) rather than adopt a higher set of increases over 3 years (2019–21).
9.4.4 City Funds and Reserve Balances
Table 9-8 shows a summary of the projected ending City operating, capital, and debt reserve balances
through 2021. The operating reserve ends at 60 days of operating expenditures; the capital reserve
ends at over $4 million, which is above the minimum target of about $1 million; and the debt reserve
ends at nearly $1 million, which is enough to cover 1 year of annual debt service.
Table 9-8. Cash Balance Summary
Existing Rate Structure and Projected Schedule 9.5
The City’s existing rate structure is composed of a single-family rate class and six non-single-family rate
classes. The rate schedule for the single-family customer class consists of a base monthly charge. The
rate schedule for non-single-family customers consists of a base monthly charge and an additional
charge per ESU based on the characteristics of a customer’s parcel.
Low-income, single-family residential customers are provided a 50 percent discount to the rates
presented. To qualify for a low-income discount, a customer must be 62 years old or older and meet low-
income guidelines as defined by the U.S. Department of Housing and Urban Development (ACC 13.24
and 13.24.030).
A recent detailed review of the City’s rate structure has been completed in the 2014 Retail Rate Study
and recommends incorporating cost-of-service adjustments among various rate classes.
Table 9-9 presents the City’s existing rate schedule for each customer class under the adopted rates
through 2017. No rate increases above adopted levels are necessary through 2017. The table then
incorporates necessary rate increases starting in 2018 and continuing through 2021.
Table 9-8. Cash Balance Summary
Ending Reserves 20142015201620172018201920202021
Operating 1,150,743$ 1,203,931$ 1,188,509$ 1,219,831$ 1,340,051$ 1,380,753$ 1,419,020$ 1,466,575$
Capital 8,362,881 6,169,948 4,170,692 2,689,831 1,997,574 2,125,099 3,482,614 4,233,887
Debt 796,781 795,239 776,414 776,414 817,130 970,712 970,712 970,712
Total 10,310,405$ 8,169,117$ 6,135,614$ 4,686,075$ 4,154,755$ 4,476,564$ 5,872,347$ 6,671,174$
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Table 9-9. Projected Rate Schedule
Affordability 9.6
The Washington State Department of Health and the PWB have historically used an affordability index to
prioritize low-cost loan awards. The typical threshold looks at whether a system’s rates exceed 1.5 to 2.0
percent of the median household income for the demographic area. As a result, if monthly bills are less
than 1.5 percent of the median household income for the demographic area, they are generally
considered affordable.
According to City staff, the median household income for the City of Auburn in 2012 was $49,996. This
figure was inflated to $51,810 at 2014 levels assuming annual Consumer Price Index adjustments.
Table 9-10 presents the City’s estimated single-family rate with the projected rate increases for the
forecast period. The affordability mark (monthly bill * 12 ÷ median income) averages 0.4 percent
throughout the study period. As shown in the following table, the City’s rates remain well within the
affordability range throughout the planning horizon.
Table 9-10 below presents the results of the affordability test.
Table 9-9. Projected Rate Schedule
Monthly Rate Schedule AdoptedAdoptedAdoptedAdopted ProjectedProjectedProjectedProjected
20142015201620172018201920202021
Annual:0.00%0.00%0.00%0.00%2.49%2.82%2.40%
Cumulative:0.00%0.00%0.00%0.00%2.49%5.39%7.92%
Single Family $18.78$19.25$19.73$20.22$20.22$20.72$21.31$21.82
Non-Single Family
Base Charge $11.68$11.97$12.27$12.58$12.58$12.89$13.26$13.58
ESU Charges
Non-Single-Family $14.95$15.32$15.71$16.10$16.10$16.50$16.97$17.37
NSF w/Detention $12.01$12.31$12.62$12.93$12.93$13.25$13.63$13.95
NSF w/Retention $7.42$7.61$7.80$8.00$8.00$8.20$8.43$8.63
NSF w/Water Quality Treatment $8.98$9.21$9.44$9.67$9.67$9.91$10.19$10.44
NSF w/Detention and Water Quality Treatment $6.78$6.95$7.13$7.31$7.31$7.49$7.70$7.89
NSF w/Retention and Water Quality Treatment $4.25$4.35$4.46$4.57 $4.57$4.68$4.82$4.93
Low Income Discount: 50%
Rate Increases Applied "Across the Board"
Rate increases shown in 2015, 2016, and 2017 reflect already-adopted annual increases of 2.5%
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Table 9-10. Affordability Test
Conclusion 9.7
The financial analysis indicates that the adopted rates in 2015, 2016, and 2017 are sufficient to meet
the Storm Drainage Utility financial obligations as presented in this forecast. No additional rate increases
are proposed for 2015–17. Based on the forecast, no rate increase is required in 2018. Rate increases
for 2019–21 average about 2.6 percent per year, for a cumulative increase of 7.9 percent.
This evaluation also finds that the rates with projected rate increases would remain well within the
defined threshold of affordability.
Table 9-10. Affordability Test
Year Inflation Median HH
Income
Projected
Monthly Bill
% of Median HH
Income
20142.50%$51,810$18.780.43%
2015 2.50%$53,106$19.250.43%
2016 2.50%$54,433$19.730.43%
2017 2.50%$55,794$20.220.43%
2018 2.50%$57,189$20.220.42%
2019 2.50%$58,619$20.720.42%
2020 2.50%$60,084$21.310.43%
2021 2.50%$61,586$21.820.43%
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Chapter 10
Limitations
This document was prepared solely for City of Auburn in accordance with professional standards at the
time the services were performed and in accordance with the contract between City of Auburn and
Brown and Caldwell dated December 6, 2013. This document is governed by the specific scope of work
authorized by 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
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.
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Chapter 11
References
Auburn City Code (ACC). 2009. http://www.codepublishing.com/wa/auburn/.
Booth. 1991. Glacier physics of the Puget lobe, southwest Cordilleran ice sheet: Geographie Physique et Quaternaire, v.
45, pp. 301–316.
Brown and Caldwell. 2014. Draft Cartegraph Economic Life Model System Requirements Specification.
City of Auburn Comprehensive Plan (Comp Plan). Amended 2011. City of Auburn.
http://www.auburnwa.gov/business/Planning___Development/Comprehensive_Plan.asp.
City of Auburn 2015 Stormwater Management Program Plan. March 2015. City of Auburn.
King County. 2010. Tabula conveyance system cost estimating software. Version 3.1.2.
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.
Pierce County. February 2013. Pierce County Rivers Flood Hazard Management Plan, Adopted February 19, 2013,
Ordinance 2012-53s. Pierce County Public Works & Utilities Surface Water Management.
SPU, 2012. City of Seattle Unit Cost Report (for APWA Standard Bid Items).
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.
Troost, K.G. and Booth, D.B, 2008. Geology of Seattle and the Seattle area, Washington. The Geological Society of
America, Reviews in Engineering Geology XX, 2008.
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.
Washington State Department of Ecology. June 2011. Green River Temperature Total Maximum Daily Load Water Quality
Improvement Report June 2011, Publication No. 11-10-046.
Western Regional Climate Center (WRCC). 2014a. “Climate of Washington.”
http://www.wrcc.dri.edu/narratives/WASHINGTON.htm
Western Regional Climate Center (WRCC). 2014b. “Period of Record Monthly Climate Summary for Seattle Tcoma Wscmo
Ap, Washington.” http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?waseat
Western Regional Climate Center (WRCC). 2014c. “Period of Record Monthly Climate Summary for Kent, Washington.”
http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?wakent
WSDOT, 2012–2014. Unit Bid Tab for the Northwest region.
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Appendix A: Western Washington Phase II Municipal
Stormwater Permit
Comprehensive Storm Drainage Plan
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Appendix B: Phase II NPDES Stormwater Permit
Compliance Work Plan
Comprehensive Storm Drainage Plan
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Appendix C: Hydrologic and Hydraulic Modeling and
Evaluation
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Appendix D: SEPA Compliance