HomeMy WebLinkAboutDRAFT City of Auburn 2016 Comprehensive Sewer Plan
2016 Comprehensive Sewer Plan
(General Sewer Plan)
Prepared for
City of Auburn, Washington
December, 2015
701 Pike Street, Suite 1200
Seattle, WA 98101-2310
Phone: 206-624-0100
Fax: 206-749-2200
2016 Comprehensive Sewer Plan
(General Sewer Plan)
Prepared for
City of Auburn, Washington
December, 2015
v
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Table of Contents
List of Figures ............................................................................................................................................... ix
List of Tables ................................................................................................................................................ x
List of Abbreviations .................................................................................................................................... xi
Executive Summary ..................................................................................................................................... 1
ES.1 LOS Goals ................................................................................................................................... 2
ES.2 Evaluation of the Sewer Utility .................................................................................................. 3
ES.3 Implementation Plan ................................................................................................................. 3
ES.3.1 6-Year and 20-Year CIP ............................................................................................... 3
ES.3.2 Monitoring .................................................................................................................... 6
ES.3.3 Asset Management and Maintenance and Operations ............................................ 6
1. Introduction .........................................................................................................................................1-1
1.1 Purpose and Objectives ..........................................................................................................1-1
1.2 Document Organization ..........................................................................................................1-2
2. Background .........................................................................................................................................2-1
2.1 Previous Auburn Comprehensive Sewer Plans .....................................................................2-1
2.2 City Comprehensive Plan........................................................................................................2-1
2.3 Sanitary Sewer Service Area ..................................................................................................2-1
2.4 Existing Land Use Plans .........................................................................................................2-1
2.4.1 King County Comprehensive Plan ...........................................................................2-1
2.4.2 King County Regional Wastewater Services Plan ...................................................2-2
2.4.3 City of Auburn Water Resources Protection Report ...............................................2-7
2.5 Neighboring Sewer Utilities ....................................................................................................2-7
2.5.1 Soos Creek Water and Sewer District and City of Kent .........................................2-7
2.5.2 City of Pacific ............................................................................................................2-7
2.5.3 Muckleshoot Indian Tribe Reservation ...................................................................2-7
2.5.4 Lakehaven Utility District .........................................................................................2-8
2.5.5 City of Algona ............................................................................................................2-8
2.5.6 City of Bonney Lake ..................................................................................................2-8
2.5.7 King County ...............................................................................................................2-8
3. Wastewater System Policies ..............................................................................................................3-1
3.1 Sewer Comprehensive Plan Policies, Standards, and Guidelines .......................................3-1
3.2 City Comprehensive Plan and Auburn City Code Goals and Policies ...................................3-1
3.3 Sanitary Sewer Level of Service .............................................................................................3-1
3.4 Business Practices Policy .......................................................................................................3-1
4. Description of Existing System ..........................................................................................................4-1
4.1 Overview ..................................................................................................................................4-1
Table of Contents 2016 Comprehensive Sewer Plan
vi
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
4.1.1 Valley Sewer Basin ...................................................................................................4-1
4.1.2 West Hill Sewer Basin ..............................................................................................4-1
4.1.3 Lea Hill Sewer Basin .................................................................................................4-2
4.1.4 Auburn Way South Sewer Basin ..............................................................................4-2
4.1.5 South Hill Sewer Basin .............................................................................................4-2
4.2 Sanitary Sewer Facilities ........................................................................................................4-2
4.2.1 Critical Infrastructure ...............................................................................................4-7
4.2.2 Pump Stations ..........................................................................................................4-7
4.2.3 Gravity and Force Main Collection System .............................................................4-8
4.2.4 Side Sewer Laterals..................................................................................................4-8
4.2.5 River Crossings .........................................................................................................4-8
4.3 King County Conveyance ..................................................................................................... 4-12
4.4 Infiltration and Inflow ........................................................................................................... 4-12
4.5 Industrial Waste Discharges ............................................................................................... 4-12
4.6 Water Reclamation and Reuse ........................................................................................... 4-13
4.6.1 Regulatory Framework .......................................................................................... 4-14
4.6.2 Potential Reclaimed Water Sources ..................................................................... 4-14
4.6.3 Potential Reclaimed Water Users ......................................................................... 4-15
4.6.4 Reclaimed Water Summary .................................................................................. 4-15
5. Wastewater System Analysis .............................................................................................................5-1
5.1 Hydraulic Capacity Analysis ....................................................................................................5-1
5.1.1 Hydrologic and Hydraulic Model ..............................................................................5-1
5.1.2 Assessment Criteria .................................................................................................5-1
5.1.3 Existing-Conditions Evaluation ................................................................................5-2
5.1.4 Future-Conditions Evaluation ..................................................................................5-4
5.2 Inflow and Infiltration ........................................................................................................... 5-11
5.2.1 Initial Inflow and Infiltration Assessment ............................................................. 5-11
5.3 Sewer Extensions ................................................................................................................. 5-15
5.4 Asset Management .............................................................................................................. 5-21
6. Maintenance and Operations ............................................................................................................6-1
6.1 Utility Responsibility and Authority ........................................................................................6-1
6.1.1 Organizational Structure ..........................................................................................6-1
6.1.2 Staffing Level ............................................................................................................6-2
6.1.3 Level of Service ........................................................................................................6-3
6.1.4 Operator Training and Education ............................................................................6-3
6.2 Routine Operations .................................................................................................................6-3
6.2.1 Pump Station Maintenance .....................................................................................6-3
6.2.2 Collection System Maintenance ..............................................................................6-5
6.2.3 Field Operations .......................................................................................................6-6
6.3 Fats, Oils, and Grease Reduction Program ...........................................................................6-6
2016 Comprehensive Sewer Plan Table of Contents
vii
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
6.4 Non-Routine and Emergency Operations ..............................................................................6-7
6.4.1 Customer Service Requests ....................................................................................6-7
6.4.2 Emergency Response Program ...............................................................................6-8
6.5 Communications, Data Collection, and Record-Keeping .....................................................6-8
6.5.1 Telemetry and Pump Station Controls ....................................................................6-8
6.5.2 Data Collection and Record-Keeping ......................................................................6-9
6.6 Existing Staffing Requirements ........................................................................................... 6-10
6.7 Potential Improvement Opportunities and Capital Needs ................................................ 6-11
7. Recommended Plan ...........................................................................................................................7-1
7.1 Capital Improvement Program ...............................................................................................7-1
7.1.1 Project Priority...........................................................................................................7-2
7.1.2 Project Cost ...............................................................................................................7-2
7.2 Project Summary.....................................................................................................................7-2
8. Finance ................................................................................................................................................8-1
8.1 Past Financial Performance ...................................................................................................8-1
8.1.1 Statement of Revenues, Expenses, and Changes in Net Position ........................8-1
8.1.2 Statement of Net Position ........................................................................................8-2
8.1.3 Outstanding Debt Principal ......................................................................................8-5
8.2 Available Capital Funding Resources ....................................................................................8-5
8.2.1 Internal Utility Resources .........................................................................................8-5
8.2.2 Government Programs and Resources ...................................................................8-7
8.2.3 Public Debt Financing ..............................................................................................8-9
8.2.4 Capital Resource Funding Summary .................................................................... 8-10
8.3 Financial Plan ....................................................................................................................... 8-10
8.3.1 Utility Fund Structure ............................................................................................ 8-11
8.3.2 Financial Policies ................................................................................................... 8-11
8.3.3 Capital Funding Plan ............................................................................................. 8-12
8.4 Financial Forecast ............................................................................................................... 8-14
8.4.1 Cash Flow Test ....................................................................................................... 8-14
8.4.2 Coverage Test ........................................................................................................ 8-14
8.4.3 Financial Forecast ................................................................................................. 8-14
8.4.4 City Funds and Reserves Balances ...................................................................... 8-17
8.5 Existing Rate Structure and Projected Schedule ............................................................... 8-17
8.6 Affordability .......................................................................................................................... 8-18
8.7 Conclusion ............................................................................................................................ 8-19
9. Implementation Plan ..........................................................................................................................9-1
9.1 6-Year and 20-Year CIP ..........................................................................................................9-1
9.2 Monitoring ...............................................................................................................................9-2
9.3 Asset Management and Maintenance and Operation .........................................................9-3
9.3.1 Collect Asset Data ....................................................................................................9-3
Table of Contents 2016 Comprehensive Sewer Plan
viii
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
9.3.2 Criticality ...................................................................................................................9-7
9.3.3 Defining Maintenance Strategies ............................................................................9-7
9.3.4 Condition Assessments ............................................................................................9-9
9.3.5 Continual Improvement ........................................................................................ 9-10
9.4 Discharge Quality Control .................................................................................................... 9-10
9.4.1 Control of Fats, Oils, and Greases ........................................................................ 9-10
9.4.2 Industrial Waste..................................................................................................... 9-10
9.4.3 Public Education .................................................................................................... 9-10
9.5 Hazard Planning ................................................................................................................... 9-11
9.6 Maintenance Issues ............................................................................................................ 9-11
9.6.1 105th Place SE and Lea Hill Road SE .................................................................. 9-11
9.6.2 Sewers Crossing Freeway ..................................................................................... 9-11
9.6.3 Sewers within Easements ..................................................................................... 9-11
9.7 SEPA Compliance ................................................................................................................. 9-11
9.8 Schedule............................................................................................................................... 9-11
10. Limitations ................................................................................................................................... 10-1
11. References ................................................................................................................................... 11-1
Inter-local Agreements and Outside Agency Correspondence .......................................... A-1 Appendix A:
Hydraulic Capacity Analysis ................................................................................................ B-1 Appendix B:
Pump Station Information ....................................................................................................C-1 Appendix C:
SEPA Compliance ................................................................................................................ D-1 Appendix D:
2016 Comprehensive Sewer Plan Table of Contents
ix
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
List of Figures
Figure ES-1. Implementation schedule ...................................................................................................... 7
Figure 2-1. Vicinity .....................................................................................................................................2-3
Figure 2-2. Plan study area ......................................................................................................................2-5
Figure 4-1. Sewer service basins .............................................................................................................4-3
Figure 4-2. Existing wastewater conveyance system .............................................................................4-5
Figure 4-3. Critical sewers ........................................................................................................................4-9
Figure 4-4. City of Auburn collection system summary statistics ....................................................... 4-11
Figure 4-5. Potential reclaimed water users within Auburn city limits ............................................... 4-17
Figure 5-1. HGL for surcharged condition ...............................................................................................5-2
Figure 5-2. Wastewater model network and results: existing conditions, 20-year flow .......................5-5
Figure 5-3. Wastewater model network and results: future conditions, 20-year flow ..........................5-9
Figure 5-4. Primary components of an I/I management program ...................................................... 5-12
Figure 5-5. Inflow and infiltration comparative levels ......................................................................... 5-13
Figure 5-6. Existing and proposed sewer facilities .............................................................................. 5-17
Figure 5-7. Sewer extension for unsewered areas estimated costs .................................................. 5-19
Figure 6-1. City of Auburn Department of Community Development and Public Works organizational
chart ...................................................................................................................................................6-2
Figure 7-1. CIP development flow chart ..................................................................................................7-1
Figure 9-1. Sanitary sewers with missing attribute information ............................................................9-5
Figure 9-2. Example of identifying asset criticality .................................................................................9-7
Figure 9-3. Maintenance strategies based on risk .................................................................................9-8
Figure 9-4. City of Auburn Sewer Plan implementation timeline ........................................................ 9-12
Table of Contents 2016 Comprehensive Sewer Plan
x
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
List of Tables
Table ES-1. Utility Level of Service .............................................................................................................. 2
Table ES-2. Annual CIP Project Cost Summary .......................................................................................... 5
Table 3-1. Sewer Comprehensive Plan Policies ......................................................................................3-2
Table 4-1. City of Auburn Sewer Pump Station Inventory .......................................................................4-7
Table 4-2. City of Auburn Industrial Waste Discharge Permits ........................................................... 4-13
Table 5-1. Simulated 20-Year Flows to Pumping Stations, Existing Conditions Scenario ...................5-4
Table 5-2. Simulated 20-Year Flows to Pumping Stations, Future (2020) Conditions Scenarioa .......5-8
Table 5-3. King County I/I Rates ........................................................................................................... 5-11
Table 6-1. Sewer Utility M&O Field Personnel .........................................................................................6-2
Table 6-2. Sewer System Maintenance and Operation Task Summary ............................................. 6-11
Table 7-1. Annual Project Cost Summary for 6-Year and 20-Year CIP ..................................................7-3
Table 8-1. City of Auburn Statement of Revenues, Expenses, and Changes in Fund Net Position .....8-2
Table 8-2. City of Auburn Statement of Net Position ..............................................................................8-4
Table 8-3. City of Auburn Outstanding Debt Principal ............................................................................8-5
Table 8-4. City of Auburn Current System Development Charge Schedule ..........................................8-6
Table 8-5. Funding Programs ...................................................................................................................8-8
Table 8-6. City of Auburn Sewer CIP ..................................................................................................... 8-13
Table 8-7. City of Auburn Capital Financing Plan ................................................................................. 8-13
Table 8-8. City of Auburn Financial Forecast ....................................................................................... 8-16
Table 8-9. City of Auburn Cash Balance Summary .............................................................................. 8-17
Table 8-10. City of Auburn Projected Local Rate Schedule................................................................. 8-18
Table 8-11. City of Auburn Affordability Test ........................................................................................ 8-18
Table 9-1. Annual Project Cost Summary for 6-Year CIP (in millions of dollars) ...................................9-1
Table 9-2. Cost Summary for 20-Year CIP (in millions of dollars) ..........................................................9-2
Table 9-3. Criticality-Based Maintenance Strategy Summary ................................................................9-9
2016 Comprehensive Sewer Plan Table of Contents
xi
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
List of Abbreviations
ac acre(s)
ACC Auburn City Code
AMWA Association of Metropolitan Water
Agencies
APWA American Public Works Association
BAB Build America Bonds
bgs below ground surface
cf cubic foot/feet
ccf 100 cubic feet
CCTV closed-circuit television
CDPW Community Development and Public
Works Department
CERB Community Economic Revitalization
Board
CFP Capital Facilities Program
CIP Capital Improvement Program
City City of Auburn
CMMS computerized maintenance
management system
Comp Plan City of Auburn Comprehensive
Plan
County King County
CSI Conveyance System Improvements
CSWD Criteria for Sewage Works Design
d/D depth to pipe diameter
DOH Washington State Department of Health
Ecology Washington State Department of
Ecology
Engineering Engineering Services Division
EPA U.S. Environmental Protection Agency
FOG fats, oils, and grease
fps foot/feet per second
FSE food service establishment
FTE full-time equivalent
GIS geographic information system
GO general obligation
gpad gallon(s) per acre day
gph gallons per hours
gpm gallon(s) per minute
H&H hydrologic and hydraulic
HDPE high-density polyethylene pipe
HGL hydraulic grade line
I/I inflow and infiltration
IT Innovation and Technology
LACP Lateral Assessment and Certification
Program
LEED Leadership in Energy and Environmental
Design
lf linear feet
LFC local facilities charge
LOS level of service
LUD Lakehaven Utility District
M&O maintenance and operations
MACP Manhole Assessment and Certification
Program
MBR membrane bioreactor
MIT Muckleshoot Indian Tribe
MUD Muckleshoot Utility District
NASSCO National Association of Sewer Service
Companies
PAA potential annexation area
PACP Pipeline Assessment and Certification
Program
PdM predictive maintenance
Plan Comprehensive Sewer Plan
PM preventive maintenance
psi pound(s) per square inch
PSRC Puget Sound Regional Council
PVC polyvinyl chloride
PWB Public Works Board
RCE residential customer equivalent
RCW Revised Code of Washington
R&R repair and replacement
RWSP Regional Wastewater Services Plan
SARA Superfund Amendments and
Reauthorization Act of 1986
SCADA supervisory control and data acquisition
SCAQMD South Coast Air Quality Management
District
SCWSD Soos Creek Water and Sewer District
SDC system development charge
SEPA State Environmental Policy Act
SOS Save Our Streets
SSO sanitary sewer overflow
SSSA sanitary sewer service area
ULID utility local improvement district
Utility Sanitary Sewer Utility
WAC Washington Administrative Code
WSDOT Washington State Department of
Transportation
WWCPA Washington Wastewater Collection
Personnel Association
Table of Contents 2016 Comprehensive Sewer Plan
xii
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
ES-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Executive Summary
This Comprehensive Sewer Plan (Plan) for the City of Auburn, Washington (City) is an update to the
previous plan that was completed in December 2009 (Brown and Caldwell). This Plan is considered a
General Sewer Plan under authority of Washington Administrative Code (WAC) Section 173-240-050.
Within this document, Comprehensive Sewer Plan and General Sewer Plan terminology is considered
the same. Evaluation of the sanitary sewer system for this Plan incorporated a policy review; system-
wide hydraulic modeling; review and documentation of maintenance and operations (M&O)
practices; and evaluation and update of the Capital Improvement Program (CIP) to account for
completed projects, changes in system conditions, and new development, as well as to incorporate
new financial information.
This 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, which may depend on resources available.
The purpose of the Plan is to guide the City’s Sanitary Sewer Utility (Utility) with respect to future
activities and improvements for the Utility. To fulfill this stated purpose, the following objectives were
achieved:
• provide background information regarding development and planning of the Utility, the sanitary
sewer service area (SSSA), and neighboring utilities (Chapter 2)
• evaluate environmental, social, and regulatory drivers to develop level-of-service (LOS) goals for
capital facility infrastructure development, operation, maintenance, and other key elements of
utility management (Chapter 3)
• characterize the current sewer system and facilities (Chapter 4)
• perform a hydraulic modeling analysis to evaluate system capacity, review inflow and infiltration
(I/I), identify possible sewer extensions to provide City sewer service to the entire SSSA, and
provide a means to update the economic life model (Chapter 5)
• establish a baseline understanding of the proactive and responsive maintenance procedures to
evaluate Utility staffing and data collection needs (Chapter 6)
• develop a CIP based on the results of hydraulic and condition analyses by meeting required
customer service levels, effectively managing risks, and minimizing the City’s costs of sewer
asset ownership (Chapter 7)
• develop a funding plan that optimizes use of rates, system development charges (SDCs), and/or
other service fees based on projected Utility spending requirements and a review of funding
sources and City financial policies (Chapter 8)
• prioritize capital improvement projects and repair and replacement (R&R) activities to
accommodate both 6- and 20-year funding frameworks and create an implementation plan to
meet LOS goals (Chapter 9)
The following sections summarize the development of the Plan and outline the recommendations
contained in the implementation plan.
Executive Summary 2016 Comprehensive Sewer Plan
ES-2
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
ES.1 LOS Goals
LOS goals provide a framework for the Utility to assess its staffing levels, prioritize its resources,
justify its rate structure, and document its successes. It is important that LOS goals include clear
criteria to use in evaluating how well those goals are being met. LOS goals for the Utility that were
developed for this Plan are based on relevant City policies. LOS goals and associated City polices are
listed in Table ES-1.
Table ES-1. Utility Level of Service
Item* Policy, standard, or guideline statement
Planning considerations
6 The City will size gravity sewers for peak wet weather flow rates that include I/I flows. Gravity sewers will be sized to convey the
peak hourly flow without surcharging.
7 The City will size pump stations and force mains for peak wet weather flow rates that include I/I flows. Pump stations will be sized
to convey the flow with one pump out of service.
Protection and improvement of the environment and public health
16 The City will comply with all federal, state, and local regulations in operation and maintenance of the City’s wastewater collection
and conveyance infrastructure.
17
The City will evaluate Utility activities to emphasize sustainability practices. City staff will identify specific areas to measure
sustainability. Examples could include weighing energy consumption impacts more heavily during capital project development,
selecting less impactful cleaning and maintenance products, and structuring maintenance activities to minimize vehicle travel
miles. While maintaining minimum flows for efficient operation of the system, water conservation will be practiced whenever
possible. City staff will benchmark practices and log changes.
18 The City will support the use of reclaimed water technologies where economically feasible. City staff will evaluate opportunities for
reclaimed water use and support initiatives where the benefits outweigh costs.
19 The City shall pursue I/I reduction for the purposes of eliminating or reducing required capacity upgrades and reducing
maintenance costs (to include reducing wear and tear on pump stations) when determined to be cost-effective.
Customer satisfaction
21
The City will evaluate and strive to maintain customer satisfaction with Utility service delivery.
• The City will create a baseline against which to evaluate future improvements:
• Annual assessment of complaints/citizen reports
• The City will communicate proactively with the community and stakeholders regarding wastewater service
improvements.
Utility financing
36
Appropriate rates and SDCs shall be assessed to fund the ongoing maintenance, operation, and capital expenditures of the Utility,
in accordance with the Comprehensive Wastewater Plan. Periodic (typically every 5 years) cost-of-service studies shall be
completed to reassess the monthly service and SDCs (both City and King County portions). Updates will coincide with 6-year CIP
updates.
37 The City will track the cost of claims as a metric. The City will create a baseline against which to evaluate future improvements.
38 The City will track schedule and budget accuracy and performance in CIP implementation.
Business practice
42
The City will monitor the frequency and causes of any service disruptions and develop programmatic methods for reducing the
number of disruptions (e.g., backups). The City will investigate all customer service calls within 24 hours and record results in the
computerized maintenance management system (CMMS). The City will develop an M&O plan to set goals for minimizing
blockages, backups, response time, etc.
43
The City will maintain an asset criticality database to be used in prioritizing asset maintenance and R&R. The existing criticality
database will be refined to include more asset age and material information, and will be validated using the results of M&O
inspections. The database will transition from a spreadsheet-based process to an internal process within the City’s CMMS.
44 The City will perform condition assessments of critical assets. The City will develop and implement a condition assessment
schedule for all critical assets.
2016 Comprehensive Sewer Plan Executive Summary
ES-3
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Table ES-1. Utility Level of Service
Item* Policy, standard, or guideline statement
45
The City will assign industry standard design lives for sewage assets. The actual physical assessment will be compared to the
theoretical design life to determine the optimal economic life. The City will attempt to repair or replace system assets before they
exceed their economic life. The number of high-criticality assets beyond their economic life will be minimized.
46
The City will conduct maintenance activities at a level that is consistent with optimizing system reliability, asset economic life, and
system performance. The City will develop schedules for maintenance of wastewater collection and conveyance assets and link its
implementation to system performance; e.g., record instances of missed maintenance and identify inadequate performance
related to maintenance (grease and roots blockages) including missed scheduled maintenance.
47
The City will maintain a level of reliability for pump stations provided by redundancy of critical mechanical and electrical
components. The City will provide backup power generators or dual power feeds and provide a minimum of two pumps at each City
pump station.
48
The City will implement the use of the National Association of Sewer Service Companies (NASSCO) Pipeline Assessment and
Certification Program (PACP) for inspection of all pipelines, Lateral Assessment and Certification Program (LACP) for inspection of
all laterals, and Manhole Assessment and Certification Program (MACP) for inspection of all manholes. The City will minimize the
number of assets with condition grades of 4 and 5.
* Item numbers refer to the policy item number presented in Table 3-1 in Section 3.4.
ES.2 Evaluation of the Sewer Utility
In order to develop a plan for future improvements to the Utility, the existing collection system was
evaluated. This included hydraulic modeling and a review of M&O practices, which are described
below:
• Hydraulic modeling: The existing hydraulic model developed in the 2009 plan was recalibrated
with King County (County) flow monitoring data. The hydraulic capacity analysis of the City’s
sewer conveyance system assessed the capacity for current and projected wastewater flows.
The analysis also provided the basis for identifying improvements that may be necessary for the
City to provide the adopted LOS. The hydraulic model indicated that, based on current planning
and growth assumptions, there are no capacity-related issues for both current and future
conditions.
• Maintenance and operation: The City provided information on its M&O activities to include
ongoing maintenance activities, the number of staff required to undertake the activity, and
frequency of activities. Current staffing levels were compared to anticipated staffing levels
required to meet the City’s desired operation goals listed in Chapter 6. The results of this
analysis indicate that, to meet these goals, two additional M&O staff are required and the
creation of a new position is recommended to facilitate computerized maintenance
management system (CMMS) integration across all three service utilities (Sewer, Water,
Drainage).
ES.3 Implementation Plan
The implementation plan brings together information from the preceding chapters to form a work
plan of future activities for the Utility. The implementation plan consists of the 6-year and 20-year
CIP, recommendations including monitoring and data collection, and recommendations for using
asset management strategies to improve Utility maintenance and operations with an outlook on
long-term sustainability.
ES.3.1 6-Year and 20-Year CIP
The CIP projects consist primarily of ongoing and programmatic capital improvements. Ongoing
projects include projects identified through previous studies. The City has previously allocated
Executive Summary 2016 Comprehensive Sewer Plan
ES-4
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
funding to each of these projects, which are currently in various stages of execution. These projects
must continue to receive funding under the CIP until completion and have been included in this Plan
to provide a complete picture of the program. Programmatic projects are included in the CIP to
provide funding for maintaining and/or improving the LOS. These projects do not address a specific
problem, but allocate budget for addressing LOS goals.
The results of the system evaluation indicated very few new projects to be added to the 6-year CIP.
The system hydraulic analysis indicated no need for capacity-related capital projects.
Table ES-2 lists nine capital improvement projects included in this Plan and lays out annual
expenditures for the 6-year and 20-year CIP time frames.
2016 Comprehensive Sewer Plan Executive Summary
ES-5
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Table ES-2. Annual CIP Project Cost Summary
Project
number Project name Priority 2016 2017 2018 2019 2020 2021 2022–35 Project Cost
CIP
allocations
(repair/
replacement)
CIP
allocations
(upgrade/
expansion)
1
Sanitary Sewer Repair
and
Replacement/System
Improvements
1 $1,873,000 $300,000 $1,500,000 $300,000 $1,500,000 $300,000 $12,600,000 $18,373,000 100% 0%
2 Street Utility
Improvements 1 $200,000 $200,000 $200,000 $200,000 $200,000 $200,000 $2,800,000 $4,000,000 100% 0%
3 Vactor Decant Facility 1 $150,000 $0 $0 $0 $0 $0 $0 $150,000 0% 100%
4
Sewer Pump Station
Replacement/
Improvement 1 $0 $141,000 $500,000 $168,000 $900,000 $141,000 $2,850,000 $4,700,000 100% 20%
5 Siphon Assessment 1 $0 $524,000 $0 $0 $0 $0 $524,000 $1,048,000 100% 0%
6 Pump Station Condition
Assessment 1 $187,000 $0 $0 $0 $0 $0 $187,000 $374,000 100% 0%
7 Manhole Ring and
Cover Replacement 2 $80,000 $80,000 $80,000 $80,000 $80,000 $80,000 $1,120,000 $1,600,000 100% 0%
8 Cleaning and Inspection
of Large-Diameter Pipe 2 $0 $400,000 $0 $0 $0 $0 $400,000 $800,000 100% 0%
9 Inflow and Infiltration
Study 3 $0 $135,200 $135,200 $135,200 $135,200 $135,200 $0 $676,000 100% 0%
10 Plan Update 1 $0 $0 $0 $0 $350,000 $0 $700,000 $1,050,000 50% 50%
Total cost for priority 1 projects $2,410,000 $1,165,000 $2,200,000 $668,000 $2,950,000 $641,000 $19,661,000 $29,695,000
Total cost for priority 2 projects $80,000 $480,000 $80,000 $80,000 $80,000 $80,000 $1,520,000 $2,400,000
Total cost for priority 3 projects $0 $135,200 $135,200 $135,200 $135,200 $135,200 $0 $676,000
Total CIP cost $2,490,000 $1,780,200 $2,415,200 $883,200 $3,165,200 $856,200 $21,181,000 $32,771,000
Executive Summary 2016 Comprehensive Sewer Plan
ES-6
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
ES.3.2 Monitoring
The current and projected future levels of I/I within the City’s collection system do not appear to
cause capacity-related issues. However, high I/I can be indicative of either deteriorating pipe
condition or storm drainage connections to the sewer system so, to be proactive, it is recommended
that the City initiate additional flow monitoring that can be used during the next Plan update to
further assess I/I and add confidence to the hydraulic model.
ES.3.3 Asset Management and Maintenance and Operations
The following additional recommendations were made for activities that will support asset
management and ongoing M&O:
• Continue system inventory: Asset management practices and M&O activities can best be utilized
with a completed inventory of assets owned and maintained by the City. Many of the City’s
assets are currently included in Cartegraph, its CMMS, but not all assets are currently included
and some assets are missing important identifying information (such as age and material of
construction). Completing the asset inventory will help the City continue to best apply its M&O
resources.
• Migrate the economic life model to the CMMS: The economic life model created as part of the
2009 plan should be implemented with the CMMS to facilitate use and most up-to-date model
accuracy.
• Optimize M&O program: Optimizing M&O activities through an asset management-based
program will lead to increased effectiveness in prioritizing M&O resources and managing risk,
public perception, regulatory compliance, and costs to the Utility.
• Discharge quality control: The City should continue its efforts to minimize the impact of harmful
components in the sewage discharged to the City’s collection system. Specifically, the fats, oils,
and grease (FOG) reduction program, industrial waste permitting, and public education programs
support the collection system’s ability to convey and pump sewage effectively and the County
treatment facility’s ability to protect the environment.
• Hazard planning: The City should assess vulnerability of the sewer collection 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.
• Maintenance issues: Three known problem sites did not rise to the level of a CIP project based
on currently available information. It is recommended that the City investigate these known M&O
issues. The issues include odor issues near the 8th Street siphon and access issues with sewers
crossing freeways and those within easements on private property.
A timeline was developed to illustrate how CIP and monitoring activities in the implementation plan
fit together within 6-year and 20-year time frames. This timeline is presented on Figure ES-1.
2016 Comprehensive Sewer Plan Executive Summary
ES-7
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Project
number Project name 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035
6-year CIP 7–20-year CIP
1 Sanitary Sewer Repair &
Replacement/System Improvements
2 Street Utility Improvements
3 Vactor Decant Study
4 Sewer Pump Station
Replacement/Improvement
5 Siphon Assessment
6 Pump Station Condition Assessment
7 MH Ring and Cover Replacement
8 Cleaning and Inspection of Large-
Diameter Pipe
9 Inflow and Infiltration Study
10 Plan Update
Figure ES-1. Implementation schedule
1-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Chapter 1
Introduction
This Comprehensive Sewer Plan Update (Plan) for the City of Auburn, Washington (City) is an update
to the previous plan, prepared in 2009. This Plan is considered a General Sewer Plan under authority
of Washington Administrative Code (WAC) Section 173-240-050. Within this document,
Comprehensive Sewer Plan and General Sewer Plan terminology is considered the same. This Plan
reflects changes in existing and projected land use and population since the previous plan, as well
as sewer capital projects that have been constructed. In addition, since the previous plan, King
County (County) has performed extensive flow monitoring of the City’s collection system that, along
with updated asset information, provides valuable information for updating the hydrologic and
hydraulic (H&H) model used for assessing system capacity.
This 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, which may depend on resources available.
This Plan meets the requirements of the Washington State Department of Ecology (Ecology) as set
forth in WAC Section 173-240-050. The Plan was submitted to Ecology; the Washington State
Department of Health (DOH); King and Pierce counties; the cities of Algona, Bonney Lake, Kent, and
Pacific; Lakehaven Utility District (LUD); Soos Creek Water and Sewer District (SCWSD); and the
Muckleshoot Indian Tribe (MIT). Relevant correspondence with these agencies related to this Plan is
included in Appendix A.
1.1 Purpose and Objectives
The purpose of the Plan is to guide the City with respect to future activities and improvements for the
Sanitary Sewer Utility (Utility). To fulfill this stated purpose, the following objectives were achieved:
• evaluate environmental, social, and regulatory drivers to develop level-of-service (LOS) goals for
capital facility infrastructure development, operation, maintenance, and other key elements of
Utility management
• update the comprehensive sanitary sewer system inventory, based on the City’s geographic
information system (GIS), that incorporates currently available infrastructure data into a digital
database that can be directly linked with the hydraulic model used for analyzing the system
• perform hydraulic modeling analysis to evaluate system capacity
• develop a plan for sewer service extensions, including where extensions will occur and how the
City will serve these areas
• document the City’s existing Maintenance and Operation (M&O) program, and evaluate existing
Utility staffing
• complete a financial analysis of the Utility, including a projection of cost to provide sewer service
and development of a funding strategy for the identified LOS goals
• develop a capital improvement program (CIP) by sustainably meeting required customer service
levels, effectively managing risks, and minimizing the City’s costs of sewer asset ownership
Chapter 1 2016 Comprehensive Sewer Plan
1-2
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
• prioritize capital improvement projects to accommodate both 6- and 20-year funding frameworks
1.2 Document Organization
This Plan is organized to focus on the actions that the Utility will take while implementing Plan
recommendations. Supporting documentation and background information is included in
appendices where appropriate. The Plan is organized into the following chapters:
Chapter 1 Introduction: explains the need for updating previous sewer planning documentation,
and outlines specific objectives of the Comprehensive Sewer Plan Update
Chapter 2 Background: provides background information regarding the Utility and sanitary sewer
service area (SSSA)
Chapter 3 Wastewater System Policies: specifies the Utility policies and LOS goals used to develop
capital improvements and future M&O activities
Chapter 4 Description of Existing System: describes the existing conditions of the City’s sanitary
sewer system
Chapter 5 Wastewater System Analysis: presents methodologies used to evaluate system capacity
and future sewer extensions
Chapter 6 Recommended Plan: describes recommended capital improvement projects including
cost estimates
Chapter 7 Maintenance and Operations: provides an overview of the organization and common
procedures associated with the ongoing M&O program, and evaluates existing Utility
staffing needs based on established LOS goals
Chapter 8 Finance: develops a funding plan that optimizes use of rates, systems development
charges, and/or other service fees based on projected Utility spending requirements and
a review of funding sources and City financial policies
Chapter 9 Implementation Plan: prioritizes capital improvement projects and lays out a future work
plan
Appendix A Inter-local Agreements and Outside Agency Correspondence: provides copies of inter-
local agreements related with sanitary sewer conveyance and disposal
Appendix B Hydraulic Capacity Analysis: provides a detailed review of the hydraulic modeling
completed for near- and long-term modeling scenarios to identify areas of capacity
concern
Appendix C Pump Station Information: provides detailed information related to the pump stations
(pump sizes, wet well size, etc.)
Appendix D SEPA Compliance: provides a letter documenting the “Determination of Non-
Significance”
2-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Chapter 2
Background
This chapter includes background information related to the development of the City’s current
wastewater collection and conveyance system, including changes to the City’s Comprehensive Plan
(Comp Plan) policies that influence the design and operation of the system. Also included is a
description of the City SSSA along with information on adjacent sewer utilities, which will facilitate an
understanding of existing and potential opportunities for collaborative activities with other purveyors
to enhance system reliability or reduce costs. Changes to land use planning efforts affecting the City
SSSA are also discussed.
The city of Auburn vicinity is shown on Figure 2-1.
2.1 Previous Auburn Comprehensive Sewer Plans
The current wastewater planning effort supersedes previous plans prepared in 1968, 1982, 2001,
and 2009. This Plan builds upon concepts established in the four previous plans, modifying or
updating goals, policies, and analyses to account for present conditions.
2.2 City Comprehensive Plan
The City most recently revised its Comp Plan in June 2015. The City Comp Plan incorporates the
Comprehensive Sewer Plan by reference.
2.3 Sanitary Sewer Service Area
The City SSSA has not changed significantly since the 2009 Comprehensive Sewer Plan, which
proposed the extension of service to a small area of unincorporated King County located west of
Algona that abutted the existing SSSA. Service has now been extended to that area. The current
SSSA is shown on Figure 2-2.
As of June 2015, the City currently serves 12,723 single-family residential customers within its SSSA.
In addition, non-residential customers equate to 18,504 residential customer equivalents (RCEs)
based on total water consumption records for non-residential connections. The City tracks total RCEs
and reports to the County quarterly.
The City coordinates service at the boundary of its SSSA with nearby sewer utilities. When the City’s
SSSA extends beyond current corporate limits, a franchise is required by the City of Auburn to own,
maintain, and manage the wastewater facilities within King and Pierce counties’ rights-of-way. This
coordination with other utilities and King and Pierce counties is discussed in Section 2.5.
2.4 Existing Land Use Plans
Various land use plans govern development with the City of Auburn SSSA; these plans are described
in the following sections.
2.4.1 King County Comprehensive Plan
Urban unincorporated areas of the City’s SSSA are subject to the King County Comprehensive Plan,
as most recently updated and adopted in November 2013. This section describes changes in the
Chapter 2 2016 Comprehensive Sewer Plan
2-2
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
King County document affecting policy direction for functional plans, such as this City of Auburn
Comprehensive Sewer Plan Update.
In the updated 2013 King County Comprehensive Plan, policy F-255 states:
In the Urban Growth Area, all new development shall be served by public sewers unless:
a. Application of this policy to a proposal for a single-family residence on an individual lot
would deny all reasonable use of the property; or
b. Sewer service is not available for a proposed short subdivision of urban property in a timely
or reasonable manner as determined by the Utility Technical Review Committee. These on-
site systems shall be managed by one of the following entities, in order of preference:
1. The sewer utility whose service area encompasses the proposed short subdivision; or
2. The provider most likely to serve the area; or;
3. an Onsite Sewage System Maintainer certified by the Seattle-King County Department of
Health.
The onsite system shall meet all state and county approval requirements. The approved short
subdivision shall indicate how additional lots to satisfy the minimum density requirement of the
zoning will be located on the subject property in case sewers become available in the future. There
shall be no further subdivision of lots created under this policy unless served by public sewers.
In conjunction with policy F-255, policy F-256 states:
In the Urban Growth Area, King County and sewer utilities should jointly prioritize the replacement
of on-site systems that serve existing development with public sewers, based on the risk of
potential failure. King County and sewer utilities should analyze public funding options for such
conversion and should prepare conversion plans that will enable quick and cost-effective local
response to health and pollution problems that may occur when many on-site systems fail in an
area.
Chapter 5 discusses potential sewer extensions within currently unsewered areas. The City’s SSSA
currently includes two areas of unincorporated King County, as shown on Figure 2-2.
2.4.2 King County Regional Wastewater Services Plan
In 2007, King County adopted a revised Regional Wastewater Services Plan (RWSP), which outlines
proposed wastewater conveyance improvements. Improvements that impact the City of Auburn
collection and conveyance system include the following:
• Stuck River Trunk: new gravity pipe constructed to convey flow away from the M Street Trunk to
the Auburn West Interceptor
• Pacific Pump Station discharge: new pipe to convey flow north from the Pacific Pump Station to
the Auburn West Interceptor
• Auburn West Interceptor Parallel: new gravity pipe to replace or parallel an existing portion of the
Auburn West Interceptor between 15th Street SW and West Main Street
The Stuck River Trunk was completed in 2013. The Pacific Pump Station discharge and Auburn West
Interceptor Parallel are currently planned for construction in 2016.
In conjunction with the RWSP, the City participated in an inflow and infiltration (I/I) study as a
component sewer agency of King County. I/I is discussed in Section 4.4.
The County is in the process of updating the Conveyance System Improvements Program based on
decennial flow monitoring data and updated land use and population projections.
xxx
GreenRiver
LakeTapps
BigSoos C re e k
MillCreek
167
18
AUB
U
R
N
W
A
Y
S
B
S
T
N
W
37TH ST NE
WE
S
T
V
A
L
L
E
Y
H
W
Y
N
W
15TH ST NW
W MAIN ST
K
E
R
S
E
Y
W
A
Y
S
E
53RD ST SE
A
U
B
U
R
N
W
A
Y
S
SE 304TH ST
SE 312TH ST
11
2
T
H
A
V
E
S
E
C
S
T
S
W
A
S
T
S
E
ELLINGSON RD SW
Algona
Pacific
Sumner
Kent
Area of Bonney Lake served
by Auburn Sewer System
WhiteRiver
Unincorporated King County
Unincorporated
King County
Area of Kent served by Auburn
Sewer System
SE 277TH ST
15TH ST SW
BOUNDARY BLVD SW
L
A
K
E
T
APPSPAR K W A Y S E
Area of Pacific served by Auburn Sewer System
COMPREHENSIVE SEWER PLAN
December 2015 FIGURE 2-2CITY OF AUBURNCOMPREHENSIVE SEWERPLAN STUDY AREA
3,500 0 3,500 7,000
Feet N
P:\Auburn\145308 Auburn Sewer Comp Plan Update\_GIS\Projects\Plan Figures\fig_2-2_AuburnSewer_StudyArea 11x17.mxd
King County
Pierce County
Legend
Auburn SSSA
Area of Kent Served by Auburn
Area of Pierce County Served by Auburn
Area of Pacific Served by Auburn
Area of Bonney Lake Served by AuburnOther Sewer Utilities within City of Auburn
City of Algona
Soos Creek Water and Sewer District
City of Kent
Lakehaven Utility District
Auburn City Boundary
County line
Adjacent Cities
Algona
Kent
Pacific
Sumner
Muckleshoot Indian
Reservation
Water
Streams
Streets
Algona
Pacific
Bonney
Lake
Kent
Federal Way
Sumner
COMPREHENSIVE SEWER PLAN
1 inch = 16,667 feet
December 2015
P:\Auburn\145308 Auburn Sewer Comp Plan Update\_GIS\Projects\Plan Figures\fig_2-1_Vicinity.mxd
FIGURE 2-1VICINITY
0.5 0 0.5
Miles
N
L E G E N D
King County South
Wastewater Treatment Plant
King County collection system
Auburn City Limits
Cities
County Boundary
Muckleshoot Indian
Reservation
Hydrography
Highway
2016 Sewer Comprehensive Plan Chapter 2
2-7
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
2.4.3 City of Auburn Water Resources Protection Report
As identified in the City’s 2009 Sewer Plan, coordination with the Water Utility will be necessary in
the future, as many of the City’s unsewered areas lie within the Water Resource Protection Areas
identified in the Water Resources Protection Report completed in 2000. In particular, planning for
future wastewater infrastructure could include the importance of removing potential contamination
(i.e., onsite sewer systems) from the Water Resource Protection Areas, based on coordination with
the Water Utility.
2.5 Neighboring Sewer Utilities
The communities that surround the city of Auburn administer their own wastewater conveyance and
collection systems. The following sections describe these systems and discuss interlocal agreements
between the City and these communities that establish SSSA boundaries and other conditions of
service. Neighboring sewer utilities are identified in Figure 2-2.
2.5.1 Soos Creek Water and Sewer District and City of Kent
In the northeast corner of the city, within the Lea Hill sewer basin (as shown on Figure 4-1), are small
areas served by the SCWSD and the City of Kent. In 2001, prior to annexation, the City of Auburn
executed interlocal agreements with SCWSD and Kent establishing sanitary sewer service area
boundaries. The agreements enable SCWSD and Kent to provide the most efficient method of
sanitary sewer service to this portion of the city while ensuring that the City’s development standards
are maintained. Copies of these agreements are included in Appendix A.
2.5.2 City of Pacific
An interlocal agreement establishing sanitary sewer service area boundaries between the cities of
Auburn and Pacific was executed in 2008. This agreement allows Auburn to provide sanitary sewer
service to property located on the eastern portion of Pacific’s municipal boundary, which lies in the
vicinity of Auburn’s wastewater infrastructure. The agreement recognizes that Auburn has sufficient
wastewater conveyance capacity to support the SSSA with maximum efficiency in the use of existing
and future facilities, together with orderly and efficient sanitary sewer planning. A copy of this
agreement is included in Appendix A.
2.5.3 Muckleshoot Indian Tribe Reservation
The MIT reservation is located within and to the southeast of Auburn city limits, as shown in Figure 2-
2. In 1997, the MIT, Indian Health Service, and City of Auburn entered into an agreement for the City
to provide wastewater service to the MIT property located outside city limits, outside the potential
annexation area (PAA), and outside the Urban Growth Area. An additional agreement, signed in
2004, outlined improvements to the conveyance system from the south end of the city on Auburn
Way South to the connection to King County’s M Street Trunk. Two outcomes of that agreement were
that (1) the MIT become a component agency of the King County Wastewater Treatment Division,
which officially occurred in July 2004, and (2) the MIT would own a portion of the capacity within the
Auburn Way South sewer line for the conveyance of sewage to King County. Lands owned by the MIT
within the City SSSA are billed as ordinary ratepayers. Development of lands within the MIT
reservation must be in accordance with the agreement approved under Resolution 4902. MIT-
related agreements are included in Appendix A.
Chapter 2 2016 Comprehensive Sewer Plan
2-8
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
2.5.4 Lakehaven Utility District
In 2004, an interlocal agreement was established between LUD and the City of Auburn delineating a
mutual sewer service area boundary within a portion of the West Hill Service Area, an area recently
annexed by the City. It was determined that LUD should continue to provide sewer service to this
area in an efficient, cost-effective way.
An amendment to this agreement was established in 2005, transferring sewer service from LUD to
the City for the area known as Jovita Heights-West Hill. Copies of both LUD agreements are included
in Appendix A.
2.5.5 City of Algona
The city of Algona borders the city of Auburn to the southwest. In 2003, the cities of Algona and
Auburn executed an interlocal agreement establishing sanitary sewer service area boundaries. The
agreement allows Algona to provide sewer service to a small area in southwest Auburn, within the
city limits and adjacent to Algona. Sewer service by Algona provides efficiency in the use of existing
and future facilities. A copy of the Algona agreement is included in Appendix A.
2.5.6 City of Bonney Lake
An addendum to a 1998 interlocal agreement establishing sanitary sewer service area boundaries
between the cities of Bonney Lake and Auburn to roughly coincide with Auburn’s PAA boundaries was
executed in February 2005. The addendum added a single parcel to the City SSSA because the
parcel was partially located in both Auburn’s and Bonney Lake’s service areas as a result of the
previous agreement.
In April 2005, an interlocal agreement was established for Auburn to provide sanitary sewer service
to a parcel within Bonney Lake’s SSSA (and designated within Pierce County’s Urban Growth Area).
The maximum efficiency in the use of existing and future facilities is achieved by having Auburn
provide sewer service to this area within Bonney Lake. A subsequent agreement, executed in August
2005, allows for Bonney Lake to serve the parcel in question once a sewer franchise with Pierce
County has been secured for the area of Pierce County in which this parcel is located. Copies of both
Bonney Lake agreements are included in Appendix A.
2.5.7 King County
In 2002, the City of Auburn was granted a sanitary sewer franchise from King County to operate,
maintain, repair, and construct sewer mains, service lines, and appurtenances in, over, along, and
under County roads and rights-of-way in areas that at that time were located within unincorporated
areas of King County. The legal descriptions of the areas covered by that agreement were updated
through an amendment approved in January 2013. Copies of the agreement and amendment
(Resolution 5027) are included in Appendix A.
3-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Chapter 3
Wastewater System Policies
This chapter presents policies and standards that guide the operation and development of the City’s
wastewater collection and conveyance system. The policies and standards are derived from the
City’s Comp Plan, the Auburn City Code (ACC), and the 2009 Comprehensive Sewer Plan.
3.1 Sewer Comprehensive Plan Policies, Standards, and Guidelines
This Plan presents a number of policies or standards related to system development, maintenance,
funding, and generally how the Utility should operate. Table 3-1 organizes these various policies or
standards within topics related to service area, planning consideration, design standards, protection
of the environment and public health, customer satisfaction, Utility financing, wastewater quality,
business practice, and system performance and reliability. Taken together with the City
Comprehensive Plan and ACC, these policies define limits and outline how the wastewater collection
system shall be operated and maintained.
3.2 City Comprehensive Plan and Auburn City Code Goals and
Policies
The City Comp Plan is the City’s growth management plan and contains policies for protecting critical
areas and natural resource lands, designating urban growth areas, preparing comprehensive utility
plans, and implementing them through capital investments and development regulations. Therefore,
the Comp Plan provides a framework of policies for development, expansion, and maintenance of
the Utility.
The ACC is a collection of all the regulatory and penal ordinances and certain administrative
ordinances of the City. Title 13 of the ACC, Water, Sewers, and Public Utilities, contains the
ordinances most relevant to how the Utility operates.
It is an overarching policy that the Utility will comply and follow the City Comprehensive Plan and
ACC. References to the ACC are included in Table 3-1 where applicable.
3.3 Sanitary Sewer Level of Service
Wastewater utilities have begun to identify and articulate LOSs that define both the public service
they provide and a measurable representation of that service. By defining service in a quantifiable
way, the Utility is better able to determine whether it is meeting its own minimum performance
standards and, conversely, determine whether reallocation of resources or additional funding may be
justified to improve performance. Some LOSs might even be set for internal functions for the same
reason of helping to prioritize spending by recognizing critical activities. Policies that reflect or help
determine the LOS are spread throughout the various parts of Table 3-1, and are annotated with
“LOS” under their item number.
3.4 Business Practices Policy
The City desires to employ recognized best business practices that result in efficient and cost-
effective operation of the Utility. The City shall identify the key business functions within the Utility
Chapter 3 2016 Comprehensive Sewer Plan
3-2
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
(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.
The City understands that defining and implementing best business practices is a long-term effort
and will require a stepwise approach. Given that the Utility is made up largely of physical assets that
have the greatest value and deserve the greatest commitment to operate and maintain, the City
shall address the business practice of asset management first.
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 confirmed by customers
• taking a life-cycle approach to asset management planning
• implementing the planned solutions to provide reliable, cost-effective service
The Utility shall begin implementing the above best practices during the next planning period and
report progress annually. Policy items related to business practice include items 41–48 in Table 3-1.
Table 3-1. Sewer Comprehensive Plan Policies
Item Policy, standard, or guideline statement Related Auburn
City Code
Service Area
1 The City of Auburn comprehensive planning includes the provision for future sewer service to all properties
located within its current city limits and potential annexation area.
2 The Utility will consider, but not encourage, providing sanitary sewer service to properties outside the SSSA.
Property owners outside the SSSA bear the burden of approaching adjacent sewer providers for service.
3 The Utility does not intend to extend sanitary sewer service to or through King County rural zoned property.
4
Development where sewer service is not readily available may be served by individual onsite systems if the
individual lots are suitable for onsite systems per the requirements and approval of King County or Pierce
County Department of Health.
ACC 13.20.060
13.20.080
13.20.090
Planning Considerations
5 Future land use patterns for the SSSA are expected to correspond to existing uses or current designations. 6
LOS The City will size the sewer collection system for peak wet weather flow rates that include I/I flows. Gravity
sewers will be sized to convey the peak hourly flow without surcharging.
7
LOS The City will size pump stations and force mains for peak wet weather flow rates that include I/I flows. Pump
stations will be sized to convey the flow with one pump out of service.
Design Standards
8
The City has the authority to set design standards. The technical criteria used by the City for the design and
construction of its sanitary sewer infrastructure are based on the most recent versions of the Ecology
publication Criteria for Sewage Works Design (CSWD) and Washington State Department of Transportation
(WSDOT)/American Public Works Association (APWA) Standard Specifications. The City’s modifications and
supplements to this criterion are found in the City’s Engineering Design Standards and Construction Standards.
ACC 13.20.270
9 It is the City’s policy to transport sewage by gravity as the most cost-effective method.
10 If public pump stations are required, the City will give preference to the construction of fewer large pump
stations over a greater number of smaller pump stations.
2016 Sewer Comprehensive Plan Chapter 3
3-3
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Table 3-1. Sewer Comprehensive Plan Policies
Item Policy, standard, or guideline statement Related Auburn
City Code
11 The City prefers to serve all properties by gravity sewer. Pumped systems will be allowed only when it is not
feasible to install a total gravity system.
12
Non-gravity services (e.g., grinder pumps, low-pressure force mains, or other onsite pumping facilities) are
prohibited except in extenuating circumstances when service by gravity is infeasible. The cost of installation,
operation, and maintenance of a non-gravity system shall be borne by the property owner, community
association, developer, etc. The City will not install, own, or maintain (outside of emergencies) any part of a
non-gravity system. The property owner shall select the non-gravity system from a list of accepted pump
manufacturers and models. Prior to approval to install a non-gravity system, the property owner shall grant site
access to the City for emergency repairs in circumstances where a prompt repair is necessary to reduce the risk
of overflow (see related Policy 20).
ACC 13.20.500,
13.20.510
13
All work on side sewers shall be completed with City licensed side sewer contractors. Side sewer contractors
shall have adequate financial resources for posting all required bonds commensurate with the size and type of
work.
14 Properties will be required to connect to the public sewer system in accordance with requirements listed in the
ACC. ACC 13.20.060
15
Private sewer systems are allowed within the SSA as long as they are designed and operated per City standards,
including access, and not part of sewer extensions to other parcels. Multiple connections per parcel are
allowed.
ACC 13.20.500
Protection and Improvement of the Environment and Public Health
16
LOS
The City will comply with all federal, state, and local regulations in operation and maintenance of the City’s
wastewater collection and conveyance infrastructure.
17
LOS
The City will evaluate Utility activities to emphasize sustainability practices. City staff will identify specific areas
to measure sustainability. Examples could include weighing energy consumption impacts more heavily during
capital project development, selecting less impactful cleaning and maintenance products, and structuring
maintenance activities to minimize vehicle travel miles. While maintaining minimum flows for efficient
operation of the system, water conservation will be practiced whenever possible. City staff will benchmark
practices and log changes.
18
LOS
The City will support the use of reclaimed water technologies where economically feasible. City staff will
evaluate opportunities for reclaimed water use and support initiatives where the benefits outweigh costs.
19
LOS
The City shall pursue I/I reduction for the purposes of eliminating or reducing required capacity upgrades and
reducing maintenance costs (to include reducing wear and tear on pump stations) when determined to be cost-
effective.
20
To protect public health and the environment, the City will require a property owner to promptly repair any non-
gravity system failure. If the property owner fails to do so, the City will take such action as it deems necessary to
prevent or rectify an overflow, including but not limited to temporarily suspending occupancy of the premises or
repairing the non-gravity system at the property owner’s expense.
ACC 13.20.500,
13.20.510
Customer Satisfaction
21
LOS
Utility service delivery. The City will create a baseline against which to evaluate future improvements and
comparing to an annual assessment of complaints/citizen reports. The City will communicate proactively with
the community and stakeholders regarding wastewater service improvements.
Utility Financing
ACC 13.20.044,
13.20.048,
13.20.410,
13.20.440
22 Capacity issues within the existing system created by future development should be funded by future
developers.
23 The Utility shall implement an adequate system of internal financial controls and shall adopt an annual budget.
24 The Utility shall remain a self-supported enterprise fund; however, grants and other alternative financing may be
sought and used.
25 The funding for the CIP shall be sustained at a level sufficient to maintain system integrity. 26 The Utility shall establish fees and charges to recover all Utility costs related to development.
Chapter 3 2016 Comprehensive Sewer Plan
3-4
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Table 3-1. Sewer Comprehensive Plan Policies
Item Policy, standard, or guideline statement Related Auburn
City Code
27 Sewer rates shall be established at a level sufficient to pay expenses and maintain adequate reserves. 28 Sewer rates shall be evaluated as part of the budgeting process. 29 The sewer rate structure shall allocate costs fairly among different customer classes. 30 Rates charged shall be uniform for all Utility customers of the same class throughout the SSSA.
31 Rate assistance programs may be provided for qualified specific low-income seniors or totally or permanently
disabled citizens.
32
The Utility should maintain adequate reserves for operation and maintenance, capital improvement, and Sewer
revenue bond obligations in order to ensure that the Utility can provide continuous, reliable service and meet its
financial obligations under reasonably anticipated circumstances.
33
The City shall require new customers to substantially pay for the costs of improvements designed to
accommodate growth, while the costs to operate, maintain, repair, and improve the existing system capacity
are paid by all sewer system customers.
34 The City will reinvest in Utility capital assets in order to ensure that the integrity of the existing Utility plant and
equipment is maintained. This reinvestment is generally referred to as repair and replacement (R&R).
35
In addition to projects designed to maintain and replace existing facilities, the City shall seek to invest annually
in system improvements designed specifically to upgrade the system in order to meet State regulations and the
City’s standards and criteria. These improvements may include upgrades to the sanitary sewer supervisory
control and data acquisition (SCADA) and data management systems, and upgrades to increase safety for both
City personnel and the public, bring noncompliant infrastructure into compliance, and reduce environmental
impacts.
36
LOS
Appropriate rates and SDCs shall be assessed to fund the ongoing maintenance, operation, and capital
expenditures of the Utility, in accordance with the Comprehensive Wastewater Plan. Periodic (typically every 5
years) cost of service studies shall be completed to reassess the monthly service and SDCs (both City and King
County portions). Updates will coincide with 6-year CIP updates.
37
LOS
The City will track the cost of claims as a metric. The City will create a baseline against which to evaluate future
improvements.
38
LOS The City will track schedule and budget accuracy and performance in CIP implementation.
Wastewater Quality
39
The City, in cooperation with King County, shall seek to maximize compliance with limits established in the ACC
that designate prohibited discharges to the public sanitary sewer. Waters and wastes including, but not limited
to, industrial process chemicals; pharmaceuticals; grit; and fats, oils, and greases (FOG) are limited or
prohibited from discharge to the public sewer according to the code.
ACC 13.20.140,
13.20.156,
13.20.158,
13.20.160
40 The City will actively discourage discharge of “flushable” wipes and other non-dispersible products to the
wastewater collection system. ACC 13.20.140
Business Practice
41
The City will develop and implement system improvements, infrastructure renewal (repair, rehabilitation, or
replacement), and M&O programs for the wastewater system according to asset management principles that
address LOSs, address the triple bottom line (economic, social, and environmental benefits and costs),
minimize asset life-cycle costs, and incorporate risk management into decision making.
42
LOS
The City will monitor the frequency and causes of any service disruptions and develop programmatic methods
for reducing the number of disruptions (e.g., backups). The City will investigate all customer service calls within
24 hours and record results in the computerized maintenance management system (CMMS). The City will
develop an M&O plan to set goals for minimizing blockages, backups, response time, etc.
43
LOS
The City will maintain an asset criticality database to be used in prioritizing asset maintenance and R&R. The
existing criticality database will be refined to include more asset age and material information, and will be
validated using the results of M&O inspections. The database will transition from a spreadsheet-based process
to an integral process within the City’s CMMS.
44
LOS
The City will perform condition assessments of critical assets. The City will develop and implement a condition
assessment schedule for all critical assets.
2016 Sewer Comprehensive Plan Chapter 3
3-5
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Table 3-1. Sewer Comprehensive Plan Policies
Item Policy, standard, or guideline statement Related Auburn
City Code
45
LOS
The City will assign industry standard design lives for sewage assets. The actual physical assessment will be
compared to the theoretical design life to determine the optimal economic life. The City will attempt to repair or
replace system assets before they exceed their economic life. The number of high-criticality assets beyond their
economic life will be minimized.
46
LOS
The City will conduct maintenance activities at a level that is consistent with optimizing system reliability, asset
economic life, and system performance. The City will develop schedules for maintenance of wastewater
collection and conveyance assets and link its implementation to system performance; e.g., record instances of
missed maintenance and identify inadequate performance related to maintenance (grease and roots
blockages) including missed scheduled maintenance.
47
LOS
The City will maintain a level of reliability for pump stations provided by redundancy of critical mechanical and
electrical components. The City will provide backup power generators or dual power feeds and provide a
minimum of two pumps at each City pump station.
48
LOS
The City will implement the use of the National Association of Sewer Service Companies (NASSCO) Pipeline
Assessment and Certification Program (PACP) for inspection of all pipelines, Lateral Assessment and
Certification Program (LACP) for inspection of all laterals, and Manhole Assessment and Certification Program
(MACP) for inspection of all manholes. The City will minimize the number of assets with condition grades of 4
and 5.
System Performance and Reliability
49 The City shall create, update on a routine basis, and use an emergency response plan for critical facilities.
50
The City may work on private property on private assets when the private asset is negatively impacting the public
system. If the condition requiring such work is the responsibility of the owner, the City shall seek to recover the
costs for the work.
ACC 13.20.182,
13.2.510
51
LOS
The City may replace or repair private side sewers as part of a City initiated project to reduce I/I of extraneous
water into the sanitary sewer system where shown to be cost-effective versus capacity improvements.
52
The City will monitor the frequency, location, and details of all odor-related complaints. At a minimum, the City
will respond, research the cause of, and propose control methods once three complaints per month at a site are
documented.
53
Adequate measures shall be taken to ensure system security. At a minimum, the City shall maintain security at
pump stations by using the SCADA system (motion detection, intrusion alarms) to alert City personnel when
unauthorized access is occurring.
54
The City encourages employee participation in workshops, seminars, and other education programs to improve
job skills. The City may pay fees and employees’ time for the required certification testing, as well as required
annual renewal fees if such certification is a job requirement.
4-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Chapter 4
Description of Existing System
This chapter describes the existing wastewater collection and conveyance system and SSSA. The City
provides wastewater collection service to city residences and businesses through a variety of
facilities including gravity sewers, pump stations, and force mains. The wastewater flow is conveyed
to the King County Regional Wastewater System for treatment and disposal. The City’s system
consists of 15 sewer pump stations 1, approximately 5,200 manholes, and approximately 200 miles
of sewers and force mains. The City’s system is intended to collect and convey only sanitary flow, but
the flow also includes rainfall-derived I/I. According to City staff, there are no known sanitary sewer
overflows (SSOs) in the system.
4.1 Overview
For purposes of discussion, the City’s wastewater collection system is divided geographically into five
major sewer basins. The descriptions of the five major sewer basins (Valley, West Hill, Lea Hill,
Auburn Way South, and South Hill) are presented below and shown on Figure 4-1.
4.1.1 Valley Sewer Basin
The Valley Sewer Basin is located on the valley floor and contains the oldest portions of the City’s
sewer collection system. Three primary King County trunk sewer lines (Stuck River Trunk Sewer, M
Street Trunk Sewer, and Auburn West Interceptor Sewer) convey flow from south to north along this
sewer basin, providing the backbone for service to Auburn. The Valley Sewer Basin receives flows
from the other four sewer basins and conveys these flows to the King County sewer trunk lines. The
topography of the valley is very flat with a minor incline, sloping down from the south end of Auburn
(elevation 109 feet) to the north end of Auburn (elevation 53 feet). Seven pump stations are located
within the Valley Sewer Basin to serve areas unable to reach the King County trunk lines by gravity.
The City provides service to two small areas of unincorporated King County, located within the sewer
basin. The Valley Sewer Basin is bounded by the Lea Hill and Auburn Way South sewer basins to the
east, the South Hill Sewer Basin and the cities of Algona and Pacific to the south, the West Hill Sewer
Basin to the west, and the city of Kent to the north.
4.1.2 West Hill Sewer Basin
The West Hill Sewer Basin is located on the West Hill above the valley floor. Flows from the West Hill
Basin are conveyed to two King County trunk lines—the Auburn West Valley Interceptor and the
Auburn Interceptor. One pump station, Peasley Ridge, serves a small area within the West Hill Sewer
Basin. The West Hill Sewer Basin is bounded by the Valley Sewer Basin to the east, city of Algona to
the south, LUD to the west, and city of Kent to the north.
The western boundary of the West Hill Sewer Basin, which is also the western boundary of the
service area, was established by interlocal agreements with LUD in 2004 and 2005 (see
Appendix A).
1 Utility staff also maintain five sewer pump stations owned by and serving other City agencies (see Chapter 7).
Chapter 4 2016 Comprehensive Sewer Plan
4-2
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
4.1.3 Lea Hill Sewer Basin
The Lea Hill Sewer Basin is the portion of the city located to the east of the Green River. Sewer flows
exit the basin into the Valley Sewer Basin by river crossings at the 8th Street Bridge or the Green
River Siphon (see Section 4.2.4). There is a significant unsewered area in the north portion of the
Lea Hill Sewer Basin. A portion of the city of Kent lies within this sewer basin, and is served by City
sewer infrastructure, including the new Verdana Pump Station. The northwest area of the sewer
basin is served by SCWSD and the City of Kent (see Figure 4-1).
The north and east boundaries of the Lea Hill Sewer Basin are defined by a 2001 interlocal
agreement with the City of Kent and by a 2006 interlocal agreement with the Soos Creek (see
Appendix A).
4.1.4 Auburn Way South Sewer Basin
The Auburn Way South Sewer Basin is located east of the Valley Sewer Basin along Auburn Way
South on the Enumclaw Plateau. It is geographically bounded by State Route 18 to the north and the
White River to the south. The southeast portion of the Auburn Way South Sewer Basin borders the
MIT reservation sewer service area. The City and the Muckleshoot Utility District (MUD) jointly own a
major trunk line that discharges to King County’s newly constructed Stuck River Trunk Line at the
northwest edge of the sewer basin.
4.1.5 South Hill Sewer Basin
The South Hill Sewer Basin is bounded by the White River to the north and east, city of Pacific to the
west, and city of Sumner and Pierce County to the south. The western half of the South Hill Sewer
Basin has been developed as a residential area. Although most of the major sewer infrastructure
serving the residential area is already in place, several significant developments are currently being
constructed. The eastern half (east of Kersey Way) of the sewer basin is currently developed as low-
density rural area and is unsewered. Three pump stations (Area 19, Terrace View, and North Tapps)
serve the southern extent of the sewer basin. All of the flow from the South Hill Sewer Basin is
conveyed to King County’s Lakeland Hills Pump Station, from where it is pumped to King County’s
Lakeland Hills Trunk sewer located in the Valley Sewer Basin.
4.2 Sanitary Sewer Facilities
The following sections provide information regarding the City’s wastewater facilities. Locations of the
pumping facilities, river crossings, King County trunk lines, and other key system elements are
shown in Figure 4-2. Ownership of interceptor and collection system pipelines is indicated on the
figure by line color. Figure 4-2 also shows the City’s potable water pumps, wells, and reservoirs. The
City of Auburn draws its potable water from deep aquifer wells located throughout the city. While no
sewage treatment facilities are located within the city, portions of the conveyance system are located
in the vicinity of some of those wells. Most of the sewer lines are located more than the 100 feet
from the wellheads as stipulated for new sewer works by Ecology’s Criteria for Sewage Works Design
(CSWD) (G2-1.5.3), two wellheads are located less than 100 feet from existing sanitary sewers, as
shown on Figure 4-2.
GreenRiver
LakeTapps
BigSoos C re e k
MillCreek
167
18
AUB
U
R
N
W
A
Y
S
B
S
T
N
W
37TH ST NE
WE
S
T
V
A
L
L
E
Y
H
W
Y
N
W
15TH ST NW
W MAIN ST
K
E
R
S
E
Y
W
A
Y
S
E
53RD ST SE
A
U
B
U
R
N
W
A
Y
S
SE 304TH ST
SE 312TH ST
11
2
T
H
A
V
E
S
E
C
S
T
S
W
A
S
T
S
E
ELLINGSON RD SW
Algona
Pacific
Sumner
Kent
WhiteRiver
15TH ST SW
PE
R
I
M
E
T
E
R
R
D
S
W
CL
A
Y
S
T
N
W
Pacific
Dogwood
Verdana
Safeway
Area 19
R Street
F Street
Auburn 40
Riverside8th Street
North Tapps
22nd Street
Auburn Jail
Terrace View
Rainier RidgePeasley Ridge
Lakeland Hills
Valley Meadows
Ellingson Road
Issac Evans Park
Auburn Golf Course
Auburn Justice Center
Auburn Valley Humane Society
COMPREHENSIVE SEWER PLAN
December 2015 FIGURE 4-2EXISTING WASTEWATERCONVEYANCE SYSTEM3,500 0 3,500 7,000
Feet N
P:\Auburn\145308 Auburn Sewer Comp Plan Update\_GIS\Projects\Plan Figures\fig_4-2_ExistingWastewaterConveyanceSystem11x17.mxd
King County
Pierce County
L E G E N D
Auburn Sewers
Bonney Lake Sewers
King County Sewers
Kent Sewers
Lakehaven Sewers
Auburn/MIT Joint Sewers
MIT Sewers
Private Sewers
Major Roads
Street
Auburn Pump Station
King County Pump Station
Private Pump Station
City Water Pump Stations
City Water Reservoirs
City Water Wells/Springs
Private Water Wells*
City Water Well Within 100 Feet of Sewers
Area of Pacific served by Auburn
Area of Bonney Lake served by AuburnOther Sewer Utilities within City of Auburn
City of Algona
Soos Creek Water and Sewer District
City of Kent
Lakehaven Utility District
Auburn City Boundary
County line
Muckleshoot Indian
Reservation
Streams/Rivers/Ponds
Political Boundaries
West HillSewer Basin
Lea HillSewer Basin
Auburn Way SouthSewer Basin
South Hill Sewer Basin
Valley SewerBasin
River Crossing
River Crossing
* Per Department of Ecology Well Log database
xxx
GreenRiver
LakeTapps
BigSoos C re e k
MillCreek
167
18
AUB
U
R
N
W
A
Y
S
B
S
T
N
W
37TH ST NE
WE
S
T
V
A
L
L
E
Y
H
W
Y
N
W
15TH ST NW
W MAIN ST
K
E
R
S
E
Y
W
A
Y
S
E
53RD ST SE
A
U
B
U
R
N
W
A
Y
S
SE 304TH ST
SE 312TH ST
11
2
T
H
A
V
E
S
E
C
S
T
S
W
A
S
T
S
E
ELLINGSON RD SW
Algona
Pacific
Sumner
Kent
Area of Bonney Lake served
by Auburn Sewer System
WhiteRiver
Unincorporated
King County
textUnincorporated King County
Unincorporated
Pierce County
text
Area of Kent
served by Auburn
Sewer System
Area of Pacific servedby Auburn Sewer System
COMPREHENSIVE SEWER PLAN
December 2015 FIGURE 4-1SEWER SERVICE BASINS3,500 0 3,500 7,000
Feet N
P:\Auburn\145308 Auburn Sewer Comp Plan Update\_GIS\Projects\Plan Figures\fig_4-1_AuburnSewer_SewerServiceArea 11x17.mxd
King County
Pierce County
L E G E N D
Sanitary Sewer Basins
Auburn Way South
Lea Hill
South Hill
Valley
West Hill
King County Collection System
Major Roads
Street
Area of Pacific Served by Auburn
Area of Bonney Lake Served by Auburn
Other Sewer Utilities within City of Auburn
City of Algona
Soos Creek Water and Sewer District
City of Kent
Lakehaven Utility District
Auburn City Boundary
County line
Water
Streams
Streets
Political Boundaries
M StreetTrunk Sewer
Auburn
Interceptor
Auburn West ValleyInterceptor
Auburn West
Interceptor Sewer
Stuck RiverTrunk Sewer
Lakeland HillsTrunk Sewer
West HillSewer Basin
Lea HillSewer Basin
Auburn Way SouthSewer Basin
South Hill Sewer Basin
Valley SewerBasin
2016 Sewer Comprehensive Plan Chapter 4
4-7
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
4.2.1 Critical Infrastructure
For planning purposes, the City considers all sewer pump stations, force mains, river crossings, and
major trunk lines (pipes greater than or equal to 12 inches in diameter) to be critical infrastructure.
Also, all gravity sewer lines serving the hospital, city hall, City maintenance facility, Justice Center,
and fire stations are considered critical. These critical assets are shown in Figure 4-3.
4.2.2 Pump Stations
Since preparation of the 2009 Comprehensive Sewer Plan, the City has constructed, replaced, or
decommissioned several sewer pump stations. Recently constructed or replaced pump stations
include Auburn 40 (new), Dogwood, Ellingson, and Verdana (new). Three decommissioned facilities
include the D Street, Rainier Shadows, and White Mountain Trails pump stations.
The City currently has 15 pump stations within its SSSA. The pump stations are listed in Table 4-1
along with their location and year of construction or most recent replacement. More detailed
information regarding the pump stations is provided in Appendix C.
Table 4-1. City of Auburn Sewer Pump Station Inventory
Pump station Year
constructed/replaced Cross streets Approximate address
South Hill Sewer Basin
Area 19 2006 Lake Tapps Pkwy. E & west of 72nd St. SE 800 71st Street SE
North Tapps 2007 Lake Tapps Pkwy. SE & west of 176th Ave. E 2610 Lake Tapps Pkwy. SE
Terrace View 2007 East Valley Hwy. E & north of Terrace View Dr. SE 6005 East Valley Highway
Valley Sewer Basin
Auburn 40 2010 42nd St NE & O Pl. NE 4159 O Pl. NE
Ellingson 2011 41st St. SE, East of A St. SE 40 41st St. SE
F Street 1980 F St. SE & 17th St. SE 1700 F St. SE
R Street 1977 R St. NE & 6th St. NE 600 R St. NE
Valley Meadows 1992 4th St. SE & V St. SE 2022 4th St. SE
8th Street 1974 J St. NE & 8th St. NE 900 8th St. NE
22nd Street 1967 22nd St. SE & Riverview Dr. 1950 22nd St. NE
Auburn Way South Sewer Basin
Dogwood 2010 Dogwood St. SE & 15th St. SE 1423 Dogwood St. SE
West Hill Sewer Basin
Peasley Ridge 2001 S. 320th St. & 53rd Ave. S 5225 S 320th St.
Lea Hill Sewer Basin
Rainier Ridge 1980 125th Pl. SE & south of SE 318th Way 31809 125th Pl. SE
Riverside 1981 8th St. NE & 104th Ave. SE 31902 104th Ave. SE
Verdana 2011 118th Ave SE & SE 296th Pl. 11807 SE 296th Place (Kent)
Chapter 4 2016 Comprehensive Sewer Plan
4-8
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
4.2.3 Gravity and Force Main Collection System
The City sewer collection system includes approximately 195 miles of gravity and 5 miles of force
main pipe. The collection system consists primarily of polyvinyl chloride (PVC) or concrete pipe with a
diameter of 8 inches. Older areas of the collection system consist of clay pipe, which the City has
been replacing with other material when repairs are required. The City is continually updating its
digital geographic and record-keeping systems to include pipeline information such as age, diameter,
and installation date. Figure 4-4 provides a visual representation (by overall system percentage) of
pipeline characteristics, including unknown and/or unrecorded data. The largest current data gap is
the installation date of collection system facilities. As part of the City’s asset management efforts,
City staff will verify collection system information during routine inspections.
Additional conveyance facilities, primarily owned by King County, are also located within the Auburn
SSSA. King County conveyance facilities are discussed in Section 4.3.
4.2.4 Side Sewer Laterals
The Utility is responsible for the maintenance and repair of the portion of side sewer laterals within
the right-of-way or public sewer easement.
4.2.5 River Crossings
The City of Auburn collection system contains two crossings of the Green River. The crossings are
located at the 8th Street NE bridge and near 26th Street NE, and are shown in Figure 4-2. Detailed
descriptions of each river crossing are provided below.
4.2.5.1 Green River Crossing (via 8th Street NE)
The first crossing of the Green River was constructed in 1965. The crossing consists of a cast-iron
pipe mounted on the 8th Street NE bridge. Because the bridge is at a higher elevation than the bank
on either side, the pipe does not have a positive downhill slope across the bridge and must rely on
upstream pressure developed in the line as it comes down Lea Hill to force the flow across the
bridge. For this reason, the pipe on the bridge and continuing up Lea Hill approximately 900 linear
feet, is constructed of 14-inch-diameter cast-iron pressure pipe. At the bottom of the hill, just
upstream of the bridge, a valve chamber houses a mechanically operated control valve. The valve
was designed to remain closed until pressure, as caused by the upstream pipe filling, opens the
valve, and releases the flow across the bridge. Flow within this sewer segment is sufficiently high to
maintain continuous scouring flow along the flat portion of the pipeline.
4.2.5.2 Green River Crossing (via Inverted Siphon at 26th Street NE)
The inverted siphon across the Green River near 26th Street NE was constructed in 1986 and
includes parallel 8- and 12-inch-diameter siphon pipelines. The 8-inch-diameter siphon is typically in
use. When increased flows occur, wastewater will be redirected to the 12-inch-diameter siphon. If
needed, both siphons are capable of operating together. The siphon facility includes a flushing
manhole, located in Isaac Evans Park.
GreenRiver
LakeTapps
BigSoos C re e k
MillCreek
167
18
AUB
U
R
N
W
A
Y
S
B
S
T
N
W
37TH ST NE
WE
S
T
V
A
L
L
E
Y
H
W
Y
N
W
15TH ST NW
W MAIN ST
K
E
R
S
E
Y
W
A
Y
S
E
53RD ST SE
A
U
B
U
R
N
W
A
Y
S
SE 304TH ST
SE 312TH ST
11
2
T
H
A
V
E
S
E
C
S
T
S
W
A
S
T
S
E
ELLINGSON RD SW
WhiteRiver
CITY HALL
AUBURN JUSTICE CENTER
CITY MAINTENANCE FACILITY
DOGWOOD
VERDANA
AREA 19
R STREET
F STREET
AUBURN 40
RIVERSIDE8TH STREET
NORTH TAPPS
22ND STREET
TERRACE VIEW
RAINIER RIDGEPEASLEY RIDGE
LAKELAND HILLS
VALLEY MEADOWS
ELLINGSON ROAD
COMPREHENSIVE SEWER PLAN
December 2015 FIGURE 4-3CRITICAL SEWERS3,500 0 3,500 7,000
Feet N
P:\Auburn\145308 Auburn Sewer Comp Plan Update\_GIS\Projects\Plan Figures\fig_4-3_Critical Sewers11x17.mxd
King County
Pierce County
River Crossing
River Crossing
L E G E N DCritical Facilities
Critical Service
Fire Station
Hospital
Pump Stations
Critical Sewers
County line
King County Sewers
Sewers
Major Roads
Street
City of Auburn Sewer Service Area
Streams/Rivers/Ponds
2016 Sewer Comprehensive Plan Chapter 4
4-11
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Figure 4-4. City of Auburn collection system summary statistics
0.9% 1.6%
70.7%
10.2%
8.1%
8.5%
Pipe Diameter
UNKNOWN
< 8 inches
8 inches
10 inches
12 inches
> 12 inches
NOT CURRENTLY
COMPILED IN
CMMS DATABASE
56.5%
1.5% 0.9%
3.1%
11.4%
19.5%
7.2%
Pipe Installation Date
UNKNOWN
1960s
1970s
1980s
1990s
2000s
2010s
NOT CURRENTLY
COMPILED IN
CMMS DATABASE
13.5%
1.5%
8.7%
1.4% 1.7%
73.2%
Pipe Material
UNKNOWN
CLAY
CONCRETE
DUCTILE IRON
HDPE
PVC
NOT CURRENTLY
COMPILED IN
CMMS DATABASE
Chapter 4 2016 Comprehensive Sewer Plan
4-12
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
4.3 King County Conveyance
The King County wastewater conveyance facilities serving the City include the Auburn Interceptor,
Auburn West Valley Interceptor, Auburn West Interceptor, M Street Trunk sewer, the newly
constructed Stuck River Trunk sewer, the Lakeland Hills Trunk sewer, and the Lakeland Hills Pump
Station. As shown on Figure 4-2, the King County facilities convey wastewater from the south to the
north, collecting flow from the Auburn SSSA. The Auburn West Valley Interceptor begins in Algona
and flows through the West Hills sewer basin. The Lakeland Hills Trunk sewer and Auburn West
Interceptor carries flow from the Lakeland Hills Pump Station north. The M Street Trunk sewer lies
mainly on the eastern side of the Valley basin. The Stuck River Trunk sewer extends from the south
end of the M Street Trunk sewer in a westerly direction, where it intersects the Lakeland Hills Trunk
sewer. All flows are conveyed to the King County South Treatment Plant in Renton, Washington.
King County recently proposed several modifications to its conveyance system, to be completed in
two phases, to address projected capacity limitations. Phase A consisted of constructing a new
sewer, called the Stuck River Trunk sewer, to convey wastewater flow from the south end of the
existing M Street Trunk sewer and route it west to the Lakeland Hills Trunk sewer. Phase A
construction was completed in 2013. Phase B is currently under design and is planned for
completion in 2016. Phase B consists of constructing a new sewer, called the Auburn West
Interceptor Parallel, which will run parallel to the existing King County Auburn West Interceptor
sewer. This pipe will run north from the intersection of Perimeter Road and 15th Street SW, cross
under State Route 18, and connect to the existing Auburn West Interceptor at West Main Street and
Clay Street in Auburn. Phase B also includes a new pipeline to carry wastewater north from the city of
Pacific to Auburn. The sewer will run from King County’s Pacific Pump Station to the new Auburn
West Interceptor Parallel.
4.4 Infiltration and Inflow
King County has been conducting studies of existing I/I conditions in various local sewer agencies,
including the city of Auburn, since 2000 as part of a Regional I/I Control program within the overall
RWSP. The studies (see www.kingcounty.gov/environment/wastewater/II/Resources/Reports.aspx)
include flow monitoring, modeling, construction of pilot I/I reduction projects, and follow-up analyses
to determine the cost-effectiveness of various approaches. As a result of the study findings, King
County plans to undertake several I/I reduction projects; however, no capital projects are currently
planned for construction in Auburn.
The I/I within the City’s SSSA was assessed as part of the modeling for the RWSP. The simulated I/I
flows for some model basins exceeded the 1,100 gallons per acre day (gpad) King County standard 2,
as discussed in Chapter 5. The City will address I/I through the evaluation of its construction
standards, annual repair and replacement (R&R) projects, and the development of projects to
address large sources of I/I identified by maintenance staff. Furthermore, the City will include a
project as part of the CIP (see Chapters 6 and 9) that will monitor flows within the collection system
over the next 5 years. The data collected will be used for future system capacity modeling and I/I
assessment.
4.5 Industrial Waste Discharges
As part of its conveyance service, the City accepts industrial waste from permitted industrial waste
dischargers. King County staff manage the industrial waste program, including permitting,
2 King County Code (KCC), Section 28.84.050
2016 Sewer Comprehensive Plan Chapter 4
4-13
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
inspection, record-keeping, and enforcement. At present, the City does not project future industrial
expansion; however, a policy is in place to collaborate with King County regarding permitting
processes if expansion should occur. Table 4-2 below identifies the current industrial waste
dischargers within the City SSSA. For updated Industrial Waste Discharge Permit information, contact
King County’s Industrial Waste Program by phone (206.477.5300) or email
(Info.KCIW@kingcounty.gov).
Table 4-2. City of Auburn Industrial Waste Discharge Permits
Company name Business type Address Permit type
Accurate Industries Metal Finishing: CFR 433 233 D Street NW Permit
Aero Controls, Inc. Metal Finishing: CFR 433 1610 20th Street NW Minor Discharge Authorization
American Powder Coating Metal Fabrication 3802 B Street NW Letter of Authorization
Auburn Dairy Products Food Processing: Dairy 702 West Main Street Major Discharge Authorization
Auburn School District: Riverside High
School Ballfield Construction Project Construction Dewatering 501 Oravetz Road SE Letter of Authorization
Auburn, City of: 30th Street NE Storm
Drainage Construction Project Construction Dewatering 30th Street NE and Auburn Way Minor Discharge Authorization
Auburn, City of: Decant Facility Decant Station 1305 C Street SW Major Discharge Authorization
Black Oxide, LLC Metal Finishing: CFR 433 131 30th Street NE, Suite 25 Permit
Boeing Commercial Airplane: Auburn Metal Finishing: CFR 433 700 15th Street SW Permit
ChemStation General Type 3104 C Street NE, Suite 202 Letter of Authorization
Formula Corp.: Auburn General Type 4432 C Street NE Major Discharge Authorization
Hexacomb Corp. General Type 2820 B Street NW, Suite 111 Letter of Authorization
Hospital Central Services Association, Inc. Laundry: Linen 1600 M Street NW Major Discharge Authorization
Merrill Gardens at Auburn Construction
Project Construction Dewatering South Division Street Letter of Authorization
Oldcastle Precast Cement/Readymix 2808 A Street SE Major Discharge Authorization
Ply Gem Pacific Windows Corporation Manufacturing: Misc 5001 D Street NW Minor Discharge Authorization
Safeway, Inc.: Auburn Distribution Center Vehicle Washing 3520 Pacific Avenue South Letter of Authorization
Skills, Inc.: Auburn Facility Metal Finishing: CFR 433 715 30th Street NE Permit
TMX Aerospace General Type 5002 D Street NW, Suite 104 Major Discharge Authorization
Tri-Way Industries, Inc. (Auburn) Metal Finishing: CFR 433 506 44th Street NW Permit
Waste Management: South Sound Container Washing 701 2nd Street NW Minor Discharge Authorization
City maintenance staff manage commercial dischargers in accordance with ACC Chapter 13.22.
Maintenance activities related to commercial pretreatment facilities, specifically the City’s Fats, Oils,
and Grease (FOG) Reduction Program, are discussed in Section 7.3.
4.6 Water Reclamation and Reuse
Reclaimed water is wastewater that has been treated to a level at which it can be used safely and
effectively for beneficial, non-drinking water purposes. The City does not currently use reclaimed
water because there are no nearby sources or transmission pipelines for reclaimed water, and there
Chapter 4 2016 Comprehensive Sewer Plan
4-14
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
are no users within the SSSA with significant volume needs that would drive implementation of reuse
projects.
This section summarizes the regulatory framework surrounding the generation and use of reclaimed
water, potential reclaimed water sources and users, and City planning for near-term reclaimed water
use within the City SSSA.
4.6.1 Regulatory Framework
The state has identified reclaimed water as an important water resource management strategy that
can offer benefits related to potable water supply, wastewater management, and environmental
enhancement. State law supports the beneficial reuse of reclaimed water for consumptive
applications (such as irrigation, commercial and industrial process use, etc.) and non-consumptive
purposes (including groundwater recharge via surface percolation or direct injection, wetland
enhancement, and stream flow augmentation).
DOH and Ecology have developed standards that guide the planning and development of reclaimed
water projects and systems. These standards, summarized in the jointly published Water
Reclamation and Reuse Standards (September 1997), describe the allowable beneficial uses of
reclaimed water and the required levels of treatment appropriate for each use. The Standards
establish four classes of reclaimed water; A, B, C, and D. Class A reclaimed water represents the
highest level of treatment, referring to water that is oxidized, coagulated, filtered, and disinfected to
certain standards. Of all levels of reclaimed water, Class A is acceptable for the widest range of uses.
Additional clarification and guidance related to the design of reclaimed water facilities are provided
in Ecology’s CWSD (Ecology, 2008).
Ecology prepared draft reclaimed water regulations (WAC 173-219) to further define and provide
guidance for reclaimed water facilities and uses. The rule-making process began with legislation in
2006 that amended the Reclaimed Water Use Act, Revised Code of Washington (RCW) Chapter
90.46, and directed Ecology to coordinate with DOH, form a stakeholder Rule Advisory Committee,
and adopt a comprehensive rule for reclaimed water use by December 2010. The overall goal was to
develop a Reclaimed Water Program through rule, guidance, and statute that runs smoothly and
consistently while protecting public health and the environment. Several drafts of the proposed rule
were made available for review by stakeholders, and significant comments were submitted, but the
rule-making process was suspended by executive order before it could be completed. Ecology
reactivated the rule-making process in June 2014 with implementation of the adopted rule
estimated to occur in early 2016.
4.6.2 Potential Reclaimed Water Sources
This section identifies potential sources of reclaimed water in the vicinity of the City SSSA.
4.6.2.1 King County
City of Auburn wastewater is treated at King County’s South Treatment Plant, located in Renton,
approximately 13 miles north of Auburn. Although South Plant does generate reclaimed water for
onsite uses and nearby irrigation and habitat restoration, there are no existing or planned
transmission lines south to the City of Auburn. The status of current King County reclaimed water
comprehensive planning is discussed in Section 4.6.3.
4.6.2.2 City of Sumner
The City of Sumner wastewater treatment plant is located approximately 8 miles south of the city of
Auburn. Sumner does not currently produce reclaimed water for offsite uses, but the City will
continue to monitor Sumner’s plans for reclaimed water use to determine if transmission of
2016 Sewer Comprehensive Plan Chapter 4
4-15
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
reclaimed water from Sumner to the City of Auburn is feasible and cost-effective for potential users
within the City of Auburn SSSA.
4.6.2.3 Lakehaven Utility District
LUD owns and operates two wastewater treatment plants, the Lakota and Redondo facilities, located
approximately 7 miles to the west and northwest of the city of Auburn. LUD does not currently
produce reclaimed water, but has evaluated the feasibility of producing reclaimed water for
landscape irrigation and groundwater recharge. Because the Redondo facility site is limited with
respect to expansion area, reclaimed water improvements, if implemented, would likely occur at the
Lakota facility. The City will continue to monitor LUD planning efforts with respect to reclaimed water
production and reuse.
4.6.2.4 City of Auburn
Although the City of Auburn does not operate a centralized wastewater treatment plant, a smaller,
satellite reclaimed water production facility could feasibly be installed at one of the City’s pump
stations. A satellite facility could be used to capture wastewater flows from a specific basin, and then
generate reclaimed water for uses nearby. While a range of treatment approaches may be employed
at a satellite facility, many utilities are implementing membrane bioreactor (MBR) technology in
these types of applications, because of the small footprint required relative to other, more
conventional forms of wastewater treatment. Solids generated at the satellite facility would be
returned to the collection system and conveyed to King County’s South Treatment Plant.
4.6.3 Potential Reclaimed Water Users
Starting in 2009, King County began development of a Reclaimed Water Comprehensive Plan to
evaluate expansion of its existing reclaimed water program over a 30-year period. The City of Auburn
has supported the County’s planning process by providing non-potable water use data by specific
parcel. City staff and elected officials have also participated in reclaimed water workshops held at
key points in the County planning process. Although the Reclaimed Water Comprehensive Plan is not
complete, the County has identified and recommended policies to be further developed moving
forward. The County recommends optimizing existing reclaimed water infrastructure and
investments, with no further expansion of the reclaimed water program.
Figure 4-5, from King County’s Reclaimed Water Comprehensive Plan, presents the location of
potential reclaimed water users within Auburn city limits, color-coded by use. Most identified uses of
large volumes of water are for irrigation, which is seasonal use (approximately 4 months per year.
The industrial/commercial uses identified could use reclaimed water throughout the year, but none
of the identified users are currently a high-volume water user.
4.6.4 Reclaimed Water Summary
The City of Auburn is not planning any specific capital improvements related to producing and/or
conveying reclaimed water for the following reasons:
• King County sources of reclaimed water are unlikely to be developed for use within the City SSSA
in the near term.
• The City currently has adequate water supply and the need for offsetting potable water demands
is low at this time.
• The capital costs related to design, construction, and permitting of a reclaimed water production
facility and conveyance system to serve identified uses is not justified by generally seasonal
demand and absence of financial benefit.
Chapter 4 2016 Comprehensive Sewer Plan
4-16
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
The City acknowledges the value that a reclaimed water program might offer in the future, especially
if a nearby reclaimed water source with associated conveyance piping is extended to the City’s SSSA.
The City will continue to monitor reclaimed water planning by nearby purveyors, the adequacy of the
City’s water rights to meet current and future potable water demand, and the industrial user base to
evaluate whether reclaimed water is a feasible and economically viable alternative. City staff will also
continue to participate in King County’s reclaimed water comprehensive planning process to
promote the City’s interests in County policies, criteria, and implementation strategies.
!
!
!!
!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!King County
Pierce County
?¦
Aæ
AÆ
?¦
Aã
Aæ
Aæ
Auburn Super MallPIN: 2421049076
Auburn Game Farm ParkPIN: 2921059069
Carpinito FarmsPIN: 0000400001 0006800002 3122059019
Mosby Bros. Farm - AuburnPIN: 2121059145 2121059096
Game Farm Wilderness ParkPIN: 2921059069
Lucio BoscoloPIN: 3522049008 3522049014 3522049040 3522049103
Mt Baker MiddlePIN: 3021059031
Emerald DownsPIN: 1580600152 1221049003 1580600150 0121049020 1221049002
River Mobile Home ParkPIN: 0621059002 0621059001 0004200007
Hazelwood ES/Rainier MiddlePIN: 0921059123
Miles Sand & Gravel Co.PIN: 1921059002 1921059008 1921059010 1921059082 1921059044 1921059276 1921059277
BNSF RRPIN: 2421049006 2421049030 2421049033 2421049035 2421049037
Olympic MiddlePIN: 1921059192
Joseph SchulerPIN: 3622049003 3622049006 3622049010
Lea Hill ElementaryPIN: 0921059005
Cascade MiddlePIN: 5094400080
Issac Evans ParkPIN: 0721059032
BoeingPIN: 2521049105 2521049106 2521049107 2521049108 2521049113 2421049069 2421049089 2421049091 2421049092
Mountainview HighPIN: 0421059051
Les Grove ParkPIN: 1921059181 1921059182
Muckleshoot Reservation CemeteryPIN: 2021059047 2021059041
Ilalko ElementaryPIN: 3121059007
Insulate LLCPIN: 6649600040
Stewart ArdellaPIN: 3622049012
Roegner ParkPIN: 6655000024 6655000030 3021059325 3021059375
Auburndale ParkPIN: 0821059017
FAAPIN: 2021059030
Auburndale IIPIN: 7867000020
Mountain View CemeteryPIN: 1421049011 1421049017 1421049067 9262800341 9662800330
Auburn Golf CoursePIN: 0621059007 0621059004 0521059011
Gildo Rey ElementaryPIN: 3021059195
Pioneer ElementaryPIN: 1921059054
Auburn HighPIN: 1821059082
Meredith Hill ElementaryPIN: 0221049149
Arthur Jacobsen ElementaryPIN: 0421059057 0421059085
Dick Scobee ElementaryPIN: 0001000047
Green River Community CollegePIN: 0921059104 1621059047 1621059006 1621059003 1621059008 1621059026
Evergreen Heights ElementaryPIN: 1121049022
Fulmer FieldPIN: 2648000010
Chinook ElementaryPIN: 2121059038 2121059092
West Auburn HighPIN: 4463400005
Enrique & Clarita Santos JrPIN: 3522049015
Cameron ParkPIN: 1313500310
7th Day Adventist HQPIN: 2721059012 2721059009 2721059072 2721059007 2721059043 2721059021 2721059081 2721059005 2721059006
Cedar Lanes ParkPIN: 3021059044 3021059089 3021049052 3021059080
Universal Brass Inc.PIN: 0004000040
Scootie Brown ParkPIN: 1821059101
Terminal ParkPIN: 8581400530
Kennedy EndeavorsPIN: 0303510090
Pioneer CemeteryPIN: 0721059020
American Powder CoatingPIN: 8855500040
Mary Olson Farm ParkPIN: 0521059006 3222059031 3222059032
Lea Hill ParkPIN: 0921059020
Green Valley AssociatesPIN: 2121059160 2121059010
Holy Family ElementaryPIN: 1921059018 1921059290 1921059201 1921059258
GSA Ballfield ParkPIN: 2421049075 2421049077
Auburn Riverside HighPIN: 6655000020 6655000026
Veterans Memorial ParkPIN: 1821059327
Terminal Park ElementaryPIN: 1921059053
Brannan ParkPIN: 7338001230 0001000081
Muckleshoot CasinoPIN: 2021059001 2021059021 2021059046
Washington ElementaryPIN: 1821059060
Thomas AcademyPIN: 9360000135 9360000140 9360000146
Auburn Regional Medical CenterPIN: 0492500240
Luisito & Lucita CuaresmaPIN: 3522049042
Rotary Park - AuburnPIN: 2597500910 2921059045
Neely FarmPIN: 2121059083 2121059007
East Auburn Athletic FieldsPIN: 0421059060 0421059061 0421059062 0421059071 0421059004
Auburn AcademyPIN: 2721059038 2721059039 2721059011 2721059033 2721059094 2721059067 2721059042 2721059052 2721059014
Indian Tom ParkPIN: 1821059001
North Green River ParkPIN: 0521059119 3022059105 3022059054 3122059011 3222059113 0004200017 0004200016
−
October 2008
2,00002,0001,000
Feet
Major Road
!!!County Boundary
KC-WTD Sewer
KC-WTD Service Area
Auburn City Limits
Open Water
Potential RW Users
Agriculture
Cemetery
Commercial
Golf
Industrial
Irrigation
Lg Scale Res Irr
Nursery/Grnhouse
Park
School
Sports Facility
Potential Reclaimed Water Users
Within Auburn City Limits
The information included on this map has been compiled from a variety of sources and is
subject to change without notice. King County makes no representations or warranties,
express or implied, as to accuracy, completeness, timeliness, or rights to the use of such
information. This document is not intended for use as a survey product. King County shall
not be liable for any general, special, indirect, incidential, or consequential damages including,
but not limited to, lost revenues or lost profits resulting from the use or misue of the information
contained on this map. Any sale of this map or information on this map is prohibited except by
written permission of King County.
File Name: Q:\\WTD\Projects\BW_Reuse\Projects\auburn_users.mxd - Shari Cross
Data Source: King County
5-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Chapter 5
Wastewater System Analysis
This chapter describes the analyses completed as part of this Plan, in support of CIP development.
The specific analyses include hydraulic modeling of the City’s sewer conveyance system, assessing
I/I, identifying sewer extensions needed to provide service to the entire city, and developing system
requirements for incorporating an asset management tool into the City’s computerized maintenance
management system (CMMS). These analyses are described in more detail below.
5.1 Hydraulic Capacity Analysis
The purpose for updating the hydraulic model of the City’s sewer system was to incorporate facilities
constructed since the model was originally built, recalibrate the model with new King County flow
meter data, and provide an assessment of system capacities for current and projected wastewater
flows. The capacity assessment provides the basis for identifying improvements that may be
necessary for the Utility to achieve the adopted LOS discussed in Chapter 3. The capacity
assessment is summarized below and presented in more detail as Appendix B.
5.1.1 Hydrologic and Hydraulic Model
The hydraulic capacity analysis was completed using an H&H model of the City’s collection and
conveyance system. The City provided an existing model using the DHI MIKE URBAN modeling
platform for this analysis. The model was updated with those major sewer facilities not already
included. In addition, sewered areas and population were updated in the model using data provided
by the City, including GIS data, Puget Sound Regional Council (PSRC) population projections, and
updated zoning/land use planning.
The updated model was used to simulate base and wet weather wastewater flow for current and
projected (i.e., 20-year planning period) scenarios. The projected scenario incorporated estimated
future population and sewer area expansion. While future water conservation efforts may reduce the
overall volume of sewage discharged to the system, the effect of the efforts on the ability of the
system to convey wastewater is assumed insignificant and not incorporated in the modeling. The
simulated wet weather flow has a recurrence interval of 20 years, which is the LOS defined for
wastewater collection and conveyance (see Section 3).
The model hydrology was calibrated using data from the King County Decennial Flow Monitoring
Project, which is part of the County’s Conveyance System Improvement (CSI) program. There were 15
County flow monitoring locations in the Auburn system. King County also provided the calibrated
models of their system near Auburn. The resolution (number of flow meters used for the service
area) of these calibrated models was less than the City desired, but the County’s models provided a
useful starting point for calibrating the City’s model.
5.1.2 Assessment Criteria
The ratio of simulated depth to pipe diameter (d/D) for the 20-year flow was used to determine the
adequacy of existing and future conveyance system capacity. In an unpressurized pipe, or a pipe with
open-channel flow characteristics, the hydraulic grade line (HGL) is the elevation of the water surface
within the pipe, or the d value. In a pipe that is surcharged (pressurized flow), the HGL is defined by
Chapter 5 2016 Comprehensive Sewer Plan
5-2
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
the elevation to which water would rise in an open pipe, or manhole, as shown in Figure 5-1. In
hydraulic terms, the HGL is equal to the pressure head measured above the invert of the pipe.
Figure 5-1. HGL for surcharged condition
Pipes that surcharge frequently do not meet the LOS and should be upsized (or the tributary I/I
reduced). Additionally, surcharging can reduce pipe lifespan and cause unexpected failures. If the
surcharge depth is significant, then there is a risk of sanitary sewer overflows (SSOs) or sewers
backing up into basements. Therefore, the freeboard, defined as the distance between the water
surface in the manhole and the ground surface, should be considered when assessing conveyance
system capacity. The amount of freeboard (distance between HGL and ground surface) for the
upstream manhole, in each surcharging pipe, is included in the model output table in Appendix B.
The approach for determining which pipes need to be upsized (to provide additional capacity) was
based on the amount of surcharging. If a surcharged (d/D > 1) pipe was less than 6 feet below the
ground surface, as simulated for the 1-in-20-year evaluation storm event, then the pipe was
identified as requiring an upsize (or capacity reclaimed through reduction of I/I). The depth of 6 feet
was selected because this is considered low enough beneath the ground surface to avoid back up of
sewer flow in basements. This criterion was evaluated for both existing and future (2020) conditions.
As flows increase in the future, City staff will need to monitor water surface elevations during large
storm events throughout the system to determine when pipes should be upsized. If the observed
surcharging increases to the point of risking property or becoming an SSO, then the pipe or pipes
should be upsized (or I/I reduction sought). This approach will help to provide confidence that the
City has adequate capacity for conveying the design flows without spending more capital dollars than
necessary.
New gravity sewers would be designed to convey the once per 20-year peak hour flow without
surcharging. New or modified pump stations would be designed to convey the once per 5-year flow
with one pump out of service and to convey the once per 20-year flow with all pumps in service.
5.1.3 Existing-Conditions Evaluation
The existing-conditions scenario represents the existing conveyance system under current flow
conditions during the 20-year wet weather event. The results of this analysis identify any hydraulic
deficiencies currently within the system. Based on discussions with City staff, the model predictions
generally support their observations of no current capacity problems.
D d
2016 Comprehensive Sewer Plan Chapter 5
5-3
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Highlights of the modeling results are discussed below. The detailed results (i.e., modeled sewer
statistics) for the current (existing) conditions planning scenario are shown in Appendix B.
5.1.3.1 Gravity Sewers
The existing-conditions modeling revealed surcharging throughout the conveyance system with more
than 100 sewer pipes showing mostly minor surcharging. Surcharged sewers include all City-owned
pipes with a modeled d/D ratio of greater than 1.0. In addition, flooding to the ground surface (i.e.,
SSO) was predicted at a single location, along Boundary Boulevard SW on the southwestern limits of
the city. The location of the SSO and surcharged sewer pipes are shown on Figure 5-2, and listed in
Appendix B. The freeboard, predicted by the model, for those pipes with surcharge, is provided in
Appendix B.
The location predicted to have a SSO by the model is adjacent to King County’s Auburn West Valley
Interceptor. King County is currently planning to change the discharge location of the upstream
Pacific Pumping Station from this interceptor to the Auburn West Interceptor. This change will reduce
the hydraulic grade line downstream of the predicted SSO in the City, which would have a positive
effect. In addition, the simulated SSO is not corroborated by City observations. Therefore, no capital
project is proposed for this location.
A majority of the identified surcharging sewer pipes are adjacent to King County sewer pipes. The
surcharging at these locations is due mostly to the hydraulic grade line in the County’s sewer pipes,
and not because of insufficient capacity in the City’s sewer pipes. None of these locations had
surcharge within 6 feet of the ground surface. However, the City should observe these locations
during wet weather in the event the surcharging increases. If chronic surcharging near the ground
surface is observed, then King County should be notified. King County addresses capacity issues of
its assets with its Conveyance System Improvements (CSI) program.
Surcharging in the remaining (City) sewer pipes was minor. The surcharge in each sewer pipe was
more than 6 feet below the ground surface. Therefore, no capital projects are proposed to address
capacity in the City’s conveyance system. Sewer pipes simulated to surcharge should be observed
during wet weather events to determine if, and when, improvements may be required to prevent
basement backups or SSOs.
5.1.3.2 Pump Stations and Force Mains
Pumping station and force main flow statistics are listed in Table 5-1. The locations of the stations
are shown in Figure 5-2. The table shows the model estimates for inflows to the pumping stations.
These flow values are compared to the stations rated flow capacity. The F-Street pumping station is
the only location where the model estimated flow is higher than the rated capacity. The estimated
capacity shortfall is relatively small, about 30 percent, and City staff reported no issues at this
location. This model result should be further confirmed by frequent monitoring of pump run times
(SCADA information), field observations of water levels in the wet well and upstream sewers during
wet weather, or upstream flow monitoring as part of CIP project 9 (see Chapter 7).
The table also shows the maximum force main velocity, based on the pumping station rated capacity.
In general, the maximum velocity should not exceed 7 feet per second to avoid increased pump
power consumption. The only pumping station with an excessive maximum velocity is Ellingson Road.
Pump operating procedures at this pumping station should be evaluated in an effort to address the
excessive force main velocity. However, because of the short length of the force main, approximately
50 feet, this is not a major concern.
Chapter 5 2016 Comprehensive Sewer Plan
5-4
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Table 5-1. Simulated 20-Year Flows to Pumping Stations, Existing Conditions Scenario
Pumping
stationa
Current pumping rated
capacityb,
gallons per minute (gpm)
No. of
pumps
Existing peak 20-year
flow, gpm
Force main size,
inches
Maximum force main
velocityc, fps
Area 19 325 2 22 6 3.7
Terrace View 675 2 21 8 4.3
Ellingson Road 1,527 2 1,054 8 9.7
F Street 400 2 528 8 2.6
Riverside 400 2 54 6 4.5
R Street 100 2 79 4 2.6
Peasley Ridge 275 2 31 6 3.1
Rainer Ridge 200 2 109 6 2.3
Valley Meadows 125 2 63 4 3.2
22nd Street 550 2 167 6 6.2
D Street 400 2 97 6 4.5
8th Street 150 2 9 4 3.8
North Tapps 510 2 55 8 3.3
Verdana 2,000 3 727 12 5.7
Dogwood 300 2 151 6 3.4
a. The Auburn 40 pump station was not modeled for the plan because it is relatively new and serves a small area in the city.
b. The rated pumping capacity, or firm capacity, is based on pump station operation without the use of one (redundant) pump. Use of
all the pumps at a pump station does not provide pumping redundancy as per U.S. EPA requirements.
c. The maximum velocity based on firm pumping capacity. Velocities exceeding 7 feet per second (fps) are generally to be avoided.
Velocities in excess of 7 fps result in significant increases in pump power consumption.
5.1.4 Future-Conditions Evaluation
The results of the future-conditions scenario modeling are described in this section. This scenario
represents the conveyance system with any known, future improvements, and estimated future flows
during the 20-year wet weather event. Future flows for 2020 and 2034, based on projected growth
in the city, were simulated. The detailed results (i.e., modeled sewers) for the future-conditions
scenario are provided in Appendix B.
5.1.4.1 Gravity Sewers
The future model incorporated King County’s planned improvement to the Pacific Pumping Station
force main. As described above, this planned improvement will redirect current pump station
discharge from King County’s West Valley Interceptor to the County’s West Interceptor. This change
in discharge location eliminated the flooding predicted at Boundary Boulevard for existing conditions,
for both 2020 and 2034 future conditions.
There was no predicted flooding in the City’s conveyance system for the future conditions. The
locations of surcharged sewer pipes for the 2020 and 2034 future conditions are shown on Figure
5-2 and listed in Appendix B. The remaining freeboard predicted by the model, for those pipes with
surcharge, is provided in Appendix B.
GreenRiver
MillCreek
167
18
AUB
U
R
N
W
A
Y
S
B
S
T
N
W
37TH ST NE
WE
S
T
V
A
L
L
E
Y
H
W
Y
N
W
15TH ST NW
W MAIN ST
K
E
R
S
E
Y
W
A
Y
S
E
53RD ST SE
A
U
B
U
R
N
W
A
Y
S
SE 304TH ST
SE 312TH ST
11
2
T
H
A
V
E
S
E
C
S
T
S
W
A
S
T
S
E
ELLINGSON RD SW
WhiteRiver
15TH ST SW
PE
R
I
M
E
T
E
R
R
D
S
W
CL
A
Y
S
T
N
W
King County
Pierce County
BOUNDARY BLVD SW
Pacific
Dogwood
Verdana
Safeway
Area 19
R Street
F Street
Auburn 40
Riverside8th Street
North Tapps
22nd Street
Auburn Jail
Terrace View
Rainier RidgePeasley Ridge
Lakeland Hills
Valley Meadows
Ellingson Road
Issac Evans Park
Auburn Golf Course
Auburn Justice Center
Auburn Valley Humane Society
COMPREHENSIVE SEWER PLAN
December 2015 FIGURE 5-2WASTEWATER MODELNETWORK AND RESULTS -EXISTING CONDITIONS, 20-YR FLOW
3,500 0 3,500 7,000
Feet N
P:\Auburn\145308 Auburn Sewer Comp Plan Update\_GIS\Projects\Plan Figures\fig_4-2_ExistingWastewaterConveyanceSystem11x17.mxd
L E G E N D
Simulated surcharge
Simulated flooding
Model sewer pipe
Auburn sewer
King County sewer
Auburn Pump Station
King County Pump Station
Private Pump Station
Major Roads
Street
Auburn City Boundary
County line
Muckleshoot Indian
Reservation
Streams/Rivers/Ponds
2016 Comprehensive Sewer Plan Chapter 5
5-7
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
The future 2034 model results are shown mostly for reference. No capital projects are proposed
based on these model results because the uncertainty associated with predictions this far in the
future is very high. However, the 6-year planning horizon is more certain, and making decisions for
this time period is necessary for sound management of the City’s sewer utility. Therefore, the
discussion here will focus on the 2020 model results.
There were about 125 sewer pipes predicted to surcharge for the future (2020) conditions, which
was not significantly more than the existing-conditions evaluation. Similar to the existing-conditions
scenario, many surcharged pipes were adjacent to King County pipes. These are not considered to
be issues for the City, as described previously. The predicted surcharge in the remaining pipes was
mostly minor with the hydraulic grade line being more than 6 feet beneath the ground surface.
There were two locations where the surcharge was less than 6 feet below ground: upstream and
downstream of the Verdana Pumping Station. Neither of these locations has a simulated water
surface within 4 feet of the ground, so there is minimal risk of SSO, based on the model results. The
surcharge upstream of the pumping station appears to be caused by relatively small (8-inch
diameter) pipes (according to the City’s GIS) entering the station. This information should be field
verified and water levels in the upstream sewer pipes monitored during wet weather prior to a capital
project being developed. The surcharge downstream of the pumping station is also downstream of a
flow diversion manhole installed during construction of the Verdana Pumping Station. This flow
diversion potentially provides the City flexibility in operation to reduce the predicted surcharging by
sending more flow away from the surcharging. Again, no capital project should be developed to
address this surcharging until visual monitoring confirms excessive surcharge, and operational
changes are deemed insufficient to address the surcharge.
As a result of the future-conditions (2020) hydraulic analysis, no sewer pipe replacement capital
projects are proposed.
5.1.4.2 Pump Stations and Force Mains
Pumping station flow statistics are listed in Table 5-2. The locations of the stations are shown in
Figure 5-3. Similar to the existing-conditions modeling, the F-Street Pumping Station is shown to
have insufficient firm capacity. This pumping station is not currently recommended to be replaced,
based on the same reasoning explained in the existing-conditions section. Future flow metering data,
including data developed based on CIP project 9 (see Chapter 7), will help add fidelity to the
hydraulic model and will shape future evaluations of the conveyance system.
Chapter 5 2016 Comprehensive Sewer Plan
5-8
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Table 5-2. Simulated 20-Year Flows to Pumping Stations, Future (2020) Conditions Scenarioa
Pumping stationb Current pumping rated capacityc, gpm No. of pumps Existing peak 20-year flow,
gpm
Area 19 325 2 22
Terrace View 675 2 29
Ellingson Road 1,527 2 1,055
F Street 400 2 535
Riverside 400 2 63
R Street 100 2 82
Peasley Ridge 275 2 42
Rainer Ridge 200 2 116
Valley Meadows 125 2 71
22nd Street 550 2 175
D Street 400 2 102
8th Street 150 2 9
North Tapps 510 2 92
Verdana 2,000 3 953
Dogwood 300 2 154
a. The maximum force main velocity is not provided for future conditions because it is estimated based on the pumping stations firm
capacity, and not modeled flows. So, the maximum force main velocities are the same for existing and future conditions.
b. The Auburn 40 pump station was not modeled for the plan because it is relatively new and serves a small area in the city.
c. The rated pumping capacity, or firm capacity, is based on pump station operation without the use of one (redundant) pump. Use of
all the pumps at a pump station does not provide pumping redundancy as per U.S. EPA requirements.
GreenRiver
MillCreek
167
18
AUB
U
R
N
W
A
Y
S
B
S
T
N
W
37TH ST NE
WE
S
T
V
A
L
L
E
Y
H
W
Y
N
W
15TH ST NW
W MAIN ST
K
E
R
S
E
Y
W
A
Y
S
E
53RD ST SE
A
U
B
U
R
N
W
A
Y
S
SE 304TH ST
SE 312TH ST
11
2
T
H
A
V
E
S
E
C
S
T
S
W
A
S
T
S
E
ELLINGSON RD SW
WhiteRiver
15TH ST SW
PE
R
I
M
E
T
E
R
R
D
S
W
CL
A
Y
S
T
N
W
King County
Pierce County
BOUNDARY BLVD SW
Pacific
Dogwood
Verdana
Safeway
Area 19
R Street
F Street
Auburn 40
Riverside8th Street
North Tapps
22nd Street
Auburn Jail
Terrace View
Rainier RidgePeasley Ridge
Lakeland Hills
Valley Meadows
Ellingson Road
Issac Evans Park
Auburn Golf Course
Auburn Justice Center
Auburn Valley Humane Society
COMPREHENSIVE SEWER PLAN
December 2015 FIGURE 5-3WASTEWATER MODELNETWORK AND RESULTS -FUTURE CONDITIONS, 20-YR FLOW
3,500 0 3,500 7,000
Feet N
P:\Auburn\145308 Auburn Sewer Comp Plan Update\_GIS\Projects\Plan Figures\fig_4-2_ExistingWastewaterConveyanceSystem11x17.mxd
L E G E N D
2020 simulated surcharge
2034 simulated surcharge
Model sewer pipe
Auburn sewer
King County sewer
Auburn Pump Station
King County Pump Station
Private Pump Station
Major Roads
Street
Auburn City Boundary
County line
Muckleshoot Indian
Reservation
Streams/Rivers/Ponds
2016 Sewer Comprehensive Plan Chapter 5
5-11
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
5.2 Inflow and Infiltration
The current levels of I/I in the Auburn sewer system do not appear to be causing capacity-related
issues. However, pipes will continue to degrade, allowing more infiltration into the system, and
populations are expected to rise within the SSSA, both increasing flows to the sewer system. If I/I
capacity-related issues occur in the future, then reducing the amount of I/I in the collection system
can improve the hydraulic capacity of the system such that some pipes may not need to be replaced.
In addition, I/I reduction can help to prevent some types of structural failures and reduce M&O
requirements. It is recommended that Auburn complete an initial I/I investigation to augment
currently available data and prepare a baseline that future studies can be compared against. This
information will help to inform the decision when it is appropriate to fund and implement an actual
I/I management program.
The primary components of an I/I management program are shown in Figure 5-4. This figure depicts
the necessary components to successfully manage the project (Program Charter), identify the issues
(Problem Determination), identify proper corrections (Correction Implementation), evaluate the work
completed (Effectiveness Evaluation), and set a long-range plan (Long-Range Planning).
5.2.1 Initial Inflow and Infiltration Assessment
The King County flow monitoring included 15 flow meter basins that impact City of Auburn sewers.
Two of these basins are located outside of Auburn’s purview: one is located in Algona and in the
other basin, while within city limits, the sewers are owned and maintained by LUD. These basins
were compared to each other and ranked based on high, medium, and low I/I based on the 25-year
I/I rates normalized on inch-diameter/miles of the flow meter basin. The results of this are shown in
Figure 5-5. The two basins located outside of Auburn’s control that were evaluated showed high
levels of I/I. It is recommended that Auburn share the results of this evaluation with Algona and LUD.
King County has an I/I standard of 1,100 gpad based on peak 20-year I/I rates for sewered areas.
Values in excess of 1,100 gpad are considered to be excessive. The area is based on King County’s
GIS layer “sewerland.” This file delineates King County’s service area as sewered or unsewerable
(parks, cemeteries, etc.). The calculated I/I rates for each sewer basin (see Appendix B, Figure 3-1)
are presented in Table 5-3. This shows that all but two basins have excess I/I based on King County
standards.
Table 5-3. King County I/I Rates
Sewer basin Sewered area (ac) I/I (gpad) Sewer basin Sewered area (ac) I/I (gpad)
ABN008 270 1,630 LakelandHills_WW 716 325
ABN022 393 2,809 LKH001A 318 2,067
ABN023 106 4,452 MSTTR02A 1,476 2,186
ABN024 136 833 MSTTR22A 851 6,237
ABN027 397 1,458 MSTTR48 895 4,197
ABN032 175 11,161 WINT003 96 7,996
AUBRN53 255 21,251 WINT038 723 1,452
AUBWV016 1,513 4,561
The U.S. Environmental Protection Agency (EPA) recognizes that many collection system SSOs are
the result of high flows associated with wet weather events. Consequently, in some instances,
language has been added to National Pollutant Discharge Elimination System (NPDES) permits
requiring the permittee to take actions to reduce I/I within the sanitary collection system. To be
proactive, it is recommended that Auburn further evaluate I/I rates with additional flow monitoring
and data evaluation.
Chapter 5 2016 Comprehensive Sewer Plan
5-12
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Figure 5-4. Primary components of an I/I management program
GreenRiver
LakeTapps
BigSoos C re e k
MillCreek
167
18
AUB
U
R
N
W
A
Y
S
B
S
T
N
W
37TH ST NE
WE
S
T
V
A
L
L
E
Y
H
W
Y
N
W
15TH ST NW
W MAIN ST
K
E
R
S
E
Y
W
A
Y
S
E
53RD ST SE
A
U
B
U
R
N
W
A
Y
S
SE 304TH ST
SE 312TH ST
11
2
T
H
A
V
E
S
E
C
S
T
S
W
A
S
T
S
E
ELLINGSON RD SW
Algona
Pacific
Sumner
Kent
WhiteRiver
15TH ST SW
PE
R
I
M
E
T
E
R
R
D
S
W
CL
A
Y
S
T
N
W
Pierce County
King County
Pacific
Dogwood
Verdana
Safeway
Area 19
R Street
F Street
Auburn 40
Riverside8th Street
North Tapps
22nd Street
Auburn Jail
Terrace View
Rainier RidgePeasley Ridge
Lakeland Hills
Valley Meadows
Ellingson Road
Issac Evans Park
Auburn Golf Course
Auburn Justice Center
Auburn Valley Humane Society
COMPREHENSIVE SEWER PLAN
December 2015 FIGURE 5-5INFLOW AND INFILTRATIONCOMPARATIVE LEVELS3,500 0 3,500 7,000
Feet N
P:\Auburn\145308 Auburn Sewer Comp Plan Update\_GIS\Projects\Plan Figures\fig_4-2_ExistingWastewaterConveyanceSystem11x17.mxd
L E G E N D
Flow Meter Locations
Auburn Sewers
Bonney Lake Sewers
King County Sewers
Kent Sewers
Lakehaven Sewers
MIT Sewers
Private Sewers
Auburn Pump Station
King County Pump Station
I/I Level
High
Medium
Low
High/Not COA
Major Roads
StreetOther Sewer Utilities within City of Auburn
City of Algona
Soos Creek Water and Sewer District
City of Kent
Lakehaven Utility District
Auburn City Boundary
County line
Streams/Rivers/Ponds
Political Boundaries
2016 Sewer Comprehensive Plan Chapter 5
5-15
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
5.3 Sewer Extensions
A City goal is to be able to serve every parcel within city limits with sanitary sewer service. Currently
many areas within city limits are served by onsite systems (septic tanks) or are undeveloped.
The City’s GIS information was used to lay out an extension plan and to determine where gravity
service was feasible. This was accomplished by comparing inverts of the existing collection system,
topography, assuming minimal allowable slopes of 0.5 percent, and the location of unserved parcels.
In some locations, gravity service appears to be infeasible and pump stations are required to convey
sewage to existing infrastructure. It is estimated that up to six new pump stations may be required to
have citywide sewer service. While the pump stations were not individually sized, they would all be
small in nature, generally less than 500 gpm. In addition, gravity service is not a viable option for
about 64 parcels within city limits. These parcels will have to use mechanical means, such as
individual grinder pumps, to be connected to the City’s system. The proposed conceptual sewer
extension plan is shown on Figure 5-6.
City wide, the plan estimates the need for the following capital improvements and, for planning-level
construction cost estimates (in 2014 dollars), the following unit costs are recommended:
• 261,250 feet of 8-inch-diameter gravity pipe: $500/foot
• 8,650 feet of 4- to 8-inch-diameter force main: $400/foot
• 6 pump stations: $500,000/each (assuming no property acquisition)
• 64 non-gravity services (grinder pumps or equivalent): $10,000/each
• 7,500 feet of 2-inch-diameter low-pressure force main: $250/foot
The city was subdivided into concentrated groupings of proposed sewer extensions. Estimated
construction costs for sewer extensions were calculated for each basin based on the number of
assets within their area and the above unit costs. The results of this are shown in Figure 5-7. The
total estimated construction cost to extend service to all parts of the city is estimated to be around
$140 million. In general, such future extensions would be constructed by future development or by
the properties benefiting from such extensions.
Pacific
PUMP STATION
Dogwood
PUMP STATION
Verdana
PUMP STATION
Safeway
PUMP STATION
Area 19
PUMP STATION
R Street
PUMP STATION
F Street
PUMP STATION
Auburn 40
PUMP STATION
Riverside
PUMP STATION8th Street
PUMP STATION
North Tapps
PUMP STATION
22nd Street
PUMP STATION
Auburn Jail
PUMP STATION
Terrace View
PUMP STATION
Rainier Ridge
PUMP STATIONPeasley Ridge
PUMP STATION
Lakeland Hills
PUMP STATION
Valley Meadows
PUMP STATION
Ellingson Road
PUMP STATION
Issac Evans Park
PUMP STATION
Auburn Golf Course
PUMP STATION
Auburn Justice Center
PUMP STATION
Auburn Valley Humane Society
PUMP STATION
A
S
T
S
E
B
S
T
N
W
A
U
B
U
R
N
W
A
Y
S
M
S
T
S
E
C
S
T
S
W
SR
1
6
7
-
S
O
U
T
H
I
S
T
N
E
SR
1
6
7
-
N
O
R
T
H
AU
B
U
R
N
W
A
Y
N
R
S
T
S
E
SR 18-EAST
SR 18-WEST
12
4
T
H
A
V
E
S
E
13
2
N
D
A
V
E
S
E
WE
S
T
V
A
L
L
E
Y
H
W
Y
N
E MAIN ST
SE 304TH ST
S 277TH ST
C
S
T
N
W
C
S
T
N
E
15TH ST SW
STUCK RIVER DR SE
2ND ST E
W MAIN ST
15TH ST NW
LAKE TAPPS PKWY SE
53RD ST SE
41ST ST SE
51
S
T
A
V
E
S
29TH ST SE
SE 312TH ST
M
S
T
N
W
K
E
R
S
E
Y
W
A
Y
S
E
SE 320TH ST
M
S
T
N
E
SE 288TH ST
37TH ST SE
8TH ST NE
37TH ST NW
SE 284TH ST
22ND ST NE
L
A
K
E
L
A
N
D
H
I
L
L
S
W
A
Y
S
E
OR
A
V
E
T
Z
R
D
S
E
17TH ST SE
S 296TH ST
25TH ST SE
12TH ST SE
PE
R
I
M
E
T
E
R
R
D
S
W
55
T
H
A
V
E
S
R
S
T
N
E
AC
A
D
E
M
Y
D
R
S
E
11
0
T
H
A
V
E
S
E
D
S
T
S
E
D
S
T
N
W
A
S
T
N
E
10
4
T
H
A
V
E
S
E
PA
C
I
F
I
C
A
V
E
S
4TH ST SE
I
S
T
N
W
11
6
T
H
A
V
E
S
E
A
S
T
N
W
11
8
T
H
A
V
E
S
E
WES
T
V
A
L
L
E
Y
H
W
Y
S
LEA HIL
L
R
D
S
E
SE 299TH ST
D
S
T
N
E
GRE
E
N
R
I
V
E
R
R
D
S
E
EM
E
R
A
L
D
D
O
W
N
S
D
R
N
W
N
S
T
N
E
W
S
T
N
W
E
S
T
N
E
O
S
T
N
E
37TH ST NE
56
T
H
A
V
E
S
69TH S
T
S
E
S 316TH ST
S
C
E
N
I
C
D
R
S
E
S 287TH ST
H
S
T
N
W
44TH ST NW
62ND ST SE
S 300TH PL
14TH ST NE
CL
A
Y
S
T
N
W
SR
1
6
7
-
S
O
U
T
H
R
A
M
P
SE 316TH ST
SR 16
7
-
N
O
R
T
H
R
A
M
P
AUBURN-BLACK DIAMOND RD SE
SR 1
8
-
E
A
S
T
R
A
M
P
11
2
T
H
A
V
E
S
E
RIVERWALK DR SE
14
4
T
H
A
V
E
S
E
EVERGREEN WAY SE
EA
S
T
V
A
L
L
E
Y
H
W
Y
E
4TH ST NE
4
6
T
H
P
L
S
K
S
T
S
E
M
O
N
T
E
V
I
S
T
A
D
R
S
E
4TH ST SW
H
A
R
V
E
Y
R
D
N
E
7TH ST SE
5TH ST SE
S 331ST
S
T
BR
I
D
G
E
T
A
V
E
S
E
I
S
T
S
E
EA
S
T
B
L
V
D
(
B
O
E
I
N
G
)
67TH ST SE
DO
G
W
O
O
D
S
T
S
E
FR
O
N
T
A
G
E
R
D
L
S
T
S
E
8TH ST SE
PI
K
E
S
T
N
E
T
S
T
S
E
F
S
T
S
E
C
S
T
S
E
14
0
T
H
A
V
E
S
E
MIL
L
P
O
N
D
D
R
S
E
FO
S
T
E
R
A
V
E
S
E
H
S
T
S
E
52
N
D
A
V
E
S
G
S
T
S
E
B
S
T
S
E
1
0
5
T
H
P
L
S
E
32ND ST NE
SE 316TH PL
E
S
T
S
E
15TH ST NE
SE 310TH ST
G
P
L
S
E
47TH ST SE
56TH ST SE
RIVE
R
D
R
S
E
54
T
H
A
V
E
S
SE 296TH WAY
A
S
T
S
W
57
T
H
P
L
S
S 305TH ST
U
S
T
N
W
SE 290TH ST
QU
I
N
C
Y
A
V
E
S
E
PEASLEY CANYON RD S
12
7
T
H
P
L
S
E
13
0
T
H
A
V
E
S
E
28TH ST NE
35T
H
W
A
Y
S
E
30TH ST NE
BOUNDARY BLVD SW
J
S
T
S
E
R S
T
N
W
OL
I
V
E
A
V
E
S
E
E
L
I
Z
A
B
E
T
H
A
V
E
S
E
31ST ST NE
65
T
H
A
V
E
S
51ST ST
N
E
26TH ST SE
RI
V
E
R
V
I
E
W
D
R
N
E
SE 323RD PL
O
S
T
S
W
B S
T
N
E
S 300TH ST
SE 301ST ST
29TH ST NW
H
O
W
A
R
D
R
D
S
E
32ND S
T
S
E
SE 287TH ST
36TH
S
T
S
E
10TH ST NE
64TH ST SE
50T
H
S
T
S
E
V S
T
N
W
3RD ST SE
10
8
T
H
A
V
E
S
E
A
S
T
E
21ST ST
N
E
31ST ST SE
HE
M
L
O
C
K
S
T
S
E
2ND ST NW
85
T
H
A
V
E
S
30TH ST SE
FORE
S
T
R
I
D
G
E
D
R
S
E
S 318TH ST
SE 298TH PL
24TH ST SE
AU
B
U
R
N
A
V
E
N
E
H
S
T
N
E
23RD ST SE
22ND ST SE
64
T
H
A
V
E
S
PI
K
E
S
T
N
W
SR 18
-
W
E
S
T
R
A
M
P
G
S
T
N
E
42ND ST NW
58
T
H
A
V
E
S
16TH ST NE
17TH ST NE
S 288TH ST
11
1
T
H
P
L
S
E
24TH ST NE
SE 282ND ST
LU
N
D
R
D
S
W
19TH DR NE
12
6
T
H
A
V
E
S
E
49TH ST NE
1
0
2
N
D
A
V
E
S
E
O
S
T
S
E
SKYWAY
L
N
S
E
TE
R
R
A
C
E
D
R
N
W
HI
C
R
E
S
T
D
R
N
W
ELLINGSON RD SW
D
S
T
S
W
10TH ST SE
17
6
T
H
A
V
E
E
SE 3
2
6
T
H
P
L
SE 295TH ST
20TH ST SE
51ST ST
S
E
V
S
T
S
E
SE 286TH ST
N
A
T
H
A
N
A
V
E
S
E
37TH W
A
Y
S
E
66TH ST SE
F
S
T
S
W
14
8
T
H
A
V
E
S
E
V
C
T
S
E
24TH S
T
N
W
12
8
T
H
P
L
S
E
72ND ST SE
E
S
T
S
W
16TH ST SE
T S
T
N
W
6TH ST NW
S 312TH ST
B PL NW
42ND ST NE
13TH ST SE
11
8
T
H
P
L
S
E
S
D
I
V
I
S
I
O
N
S
T
3RD ST NW
2ND ST SE
SE
3
1
2
T
H
W
A
Y
SE 294TH ST
Z
S
T
S
E
G
S
T
S
W
57TH ST SE
SUMNER-TAPPS HWY E
55
T
H
P
L
S
73RD ST SE
EL
M
S
T
S
E
S 292ND ST
ELM LN SE
L
S
T
N
E
PE
A
R
L
A
V
E
S
E
10
5
T
H
A
V
E
S
E
SE 285TH ST
52
N
D
P
L
S
9TH ST SE
6
7
T
H
L
N
S
E
CH
A
R
L
O
T
T
E
A
V
E
S
E
SE 307TH PL
OUTLET COLLECTION WAY SW
I
S
A
A
C
A
V
E
S
E
28TH ST SE
H
A
Z
E
L
A
V
E
S
E
11TH ST NE
T
S
T
N
E
15TH ST SE
SE 42ND ST
61ST ST SE
J
S
T
N
E
26TH ST NE
SE 299TH PL
45TH
S
T
N
E
14TH ST SE
S 303RD PL
SE 308TH PL
20TH ST NW
SE 281ST ST
22ND ST NW
SE 290TH PL
10
9
T
H
P
L
S
E
HE
A
T
H
E
R
A
V
E
S
E
RA
N
D
A
L
L
A
V
E
S
E
321ST ST S
K
S
T
N
E
MAPLE DR SE
6TH ST SE
S 314T
H
S
T
U
S
T
S
E
30TH ST NW
NO
B
L
E
C
T
S
E
SE 289TH ST
S 302ND PL
19TH ST SE
SE 297TH ST
OU
T
L
E
T
C
O
L
L
E
C
T
I
O
N
D
R
S
W
5
7
T
H
D
R
S
E
WA
R
D
A
V
E
S
E
I PL NE
12
9
T
H
P
L
S
E
N
D
I
V
I
S
I
O
N
S
T
21ST ST SE
SE 307TH ST
33RD ST SE
55TH ST SE
S 324TH ST
11
1
T
H
A
V
E
S
E
SE 323RD ST
11
4
T
H
A
V
E
S
E
14TH ST NW
11
7
T
H
P
L
S
E
WE
S
T
E
R
N
A
V
E
N
W
PI
K
E
S
T
S
E
N
S
T
S
E
SE 292ND ST
11
2
T
H
P
L
S
E
42ND PL NE
OL
Y
M
P
I
C
S
T
S
E
D PL SE
53
R
D
P
L
S
SE 306TH ST
13
4
T
H
P
L
S
E
11
0
T
H
P
L
S
E
5TH ST NE
12TH ST NE
18TH ST NE
35TH ST NE
8TH ST SW
IND
U
S
T
R
Y
D
R
S
W
U
C
T
N
W
SE 302ND PL
SE 286TH PL
S 296TH PL
KA
T
H
E
R
I
N
E
A
V
E
S
E
59
T
H
A
V
E
S
SE 300TH ST
16TH ST NW
13
3
R
D
A
V
E
S
E
JA
S
M
I
N
E
A
V
E
S
E
9T
H
S
T
N
E
63
R
D
P
L
S
2ND ST NE
18TH ST SE
27TH ST SE
66
T
H
A
V
E
S
FI
R
S
T
S
E
6TH ST NE
130T
H
W
A
Y
S
E
CROS
S
S
T
S
E
3RD ST NE
EL
A
I
N
E
A
V
E
S
E
O
C
T
S
E
10
7
T
H
A
V
E
S
E
SE 308TH ST
JA
M
E
S
A
V
E
S
E
SE 305TH PL
S 307TH ST
SE 288TH PL
UD
A
L
L
A
V
E
S
E
56
T
H
P
L
S
SE 314TH PL
KE
N
N
E
D
Y
A
V
E
S
E
SE 313TH ST
AA
B
Y
D
R
N
W
V S
T
N
E
V PL SE
SE 302ND ST
S 297TH PL
SE 45TH ST
SE 318TH PL
12
1
S
T
P
L
S
E
56
T
H
C
T
S
26TH ST NW
SE 293RD ST
37
T
H
P
L
S
E
12
5
T
H
A
V
E
S
E
11
3
T
H
P
L
S
E
12
0
T
H
A
V
E
S
E
F PL NE
SE 304TH PL
S 329TH PL
S 292ND PL
71ST ST SE
S 328TH ST
SE 315TH ST
48TH
C
T
S
E
60
T
H
P
L
S
S 321ST ST
49TH ST SE
SE 321ST PL
54
T
H
C
T
S
67T
H
C
T
S
E
11TH ST SE
SE 282ND W
A
Y
12
4
T
H
P
L
S
E
S
S
T
S
E
S 324TH PL
11
4
T
H
P
L
S
E
VI
C
T
O
R
I
A
A
V
E
S
E
3RD CT SE
SE 322ND PL
13
8
T
H
A
V
E
S
E
16
7
T
H
A
V
E
E
L
P
L
N
E
S 326TH LN SE 325TH PL
SE 315TH PL
SE 309TH ST
12
2
N
D
P
L
S
E
18
1
S
T
A
V
E
E
CEDAR DR SE
12
2
N
D
A
V
E
S
E
13TH ST NE
W
E
S
L
E
Y
P
L
S
E
SE 306TH PL
SE 305TH ST305TH PL SE
23RD ST NE
SE 319TH PL
27
T
H
P
L
S
E
U
S
T
N
E
17
1
S
T
A
V
E
E
PO
P
L
A
R
S
T
S
E
JO
R
D
A
N
A
V
E
S
E
S 294TH ST
13
7
T
H
A
V
E
S
E
SE 304TH CT
87
T
H
A
V
E
S
SE 312TH PL
SE 306TH CT
O
C
T
N
E
14
T
H
P
L
N
E
SE 283RD ST
59
T
H
P
L
S
L
C
T
N
E
SE 324TH LN
S 336TH PL
68TH ST SE
W PL NW
S 344TH CT
C
C
T
S
E
H
S
T
S
E
R
S
T
N
E
50TH S
T
S
E
10
7
T
H
A
V
E
S
E
7TH ST SE
N
S
T
S
E
I
P
L
N
E
SE 290TH ST
18TH ST SE
57
T
H
P
L
S
56
T
H
A
V
E
S
SR
1
6
7
-
N
O
R
T
H
R
A
M
P
SR
1
6
7
-
S
O
U
T
H
R
A
M
P
E
L
I
Z
A
B
E
T
H
A
V
E
S
E
15TH ST SE
10
8
T
H
A
V
E
S
E
29TH ST NW
6TH ST SE
11TH ST SE
E
S
T
S
E
17TH ST NE
19TH ST SE
H
S
T
S
E
O
S
T
S
E
3RD ST NE
D
S
T
S
E
K
S
T
S
E
J
S
T
S
E
O
S
T
N
E
10TH ST NE
17TH ST
S
E
N S
T
N
E
L
S
T
S
E
SR
1
6
7
-
S
O
U
T
H
R
A
M
P
M
S
T
N
E
B
S
T
N
W
SE 282ND ST
A
S
T
S
E
37TH ST SE
D
S
T
S
E
EL
M
S
T
S
E
10
8
T
H
A
V
E
S
E
23RD ST SE
HO
W
A
R
D
R
D
S
E
SR 18-EAS
T
R
A
M
P
SE 286TH ST
72ND ST SE
J
S
T
N
E
SE 288TH ST
SE 315TH PL
C
S
T
S
E
24TH ST SE
11
6
T
H
A
V
E
S
E
SE 293RD ST
SE 290TH PL
G
S
T
S
E
SR
1
6
7
-
N
O
R
T
H
R
A
M
P
61S
T
S
T
S
E
52
N
D
A
V
E
S
K
S
T
S
E
26TH ST SE
H
S
T
S
E
SE 295TH ST
EVER
G
R
E
E
N
W
A
Y
S
E
9TH ST SE
20TH ST SE
57TH ST SE
SE 326TH PL
F
S
T
S
E
28TH ST SE
17TH ST SE
F
S
T
S
E
11
8
T
H
A
V
E
S
E
SE 294TH ST
H
S
T
N
E
28TH ST SE
D
S
T
S
E
SE 302ND ST
E
S
T
N
E
33RD ST SE
16TH ST NE
11
2
T
H
A
V
E
S
E
4TH ST SE
A S
T
N
E
SE 310TH ST
D
S
T
N
E
O
L
I
V
E
A
V
E
S
E
2ND ST SE
10TH ST NE
55
T
H
A
V
E
S
SE 307TH ST
J
S
T
S
E
L
S
T
N
E
PI
K
E
S
T
N
E
4TH ST NE
I
P
L
N
E
SE 288TH PL
R
S
T
S
E
SR 18-WEST RAMP
6TH ST NE
30TH ST NE
8TH ST NE
I
S
T
S
E
D
S
T
N
W
10
8
T
H
A
V
E
S
E
32ND ST SE
10
8
T
H
A
V
E
S
E
1
0
7
T
H
A
V
E
S
E
52
N
D
P
L
S
D
S
T
S
E
29TH ST NW
K
S
T
N
E
51
S
T
A
V
E
S
24TH ST SE
SE 295TH ST
6TH ST SE
12
1
S
T
P
L
S
E
L E G E N D
Proposed Sewers
Proposed Gravity
Proposed LPFM
Proposed Force Main
Proposed Pump Station
Ex. COA Pump Station
Ex. King County Pump Station
Ex. Other Pump Station
King County Sewers
Force Main
Gravity Main
Auburn Sewers
Force Main
Gravity Main
Private Force Main
Private Gravity Main
City of Auburn Sewer Service Area
County line
Buildings
Paved Surfaces
Water Bodies
Wetlands
Parcels
Steep Slopes
FIGURE 5 - 6
CITY OF AUBURN COMPREHENSIVE SEWER PLAN
EXISTING AND PROPOSED SEWER FACILITIES
1,000 0 1,000 2,000Feet
P:\Auburn\145308 Auburn Sewer Comp Plan Update\_GIS\Projects\Plan Figures\fig_5-2_SewerExtensions.mxd
1 inch = 1,000 feet
December 2015
N
King County
Pierce County
SR
1
6
7
SR
1
8
A
S
T
S
E
AU
B
U
R
N
W
A
Y
S
C
S
T
S
W
B
S
T
N
W
AU
B
U
R
N
W
A
Y
N
I
S
T
N
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
51
S
T
A
V
E
S
8TH ST E
12
4
T
H
A
V
E
S
E
24TH ST E
BU
T
T
E
A
V
E
15TH ST SW
12
2
N
D
A
V
E
E
2ND ST E
SE 312TH ST
S 277TH ST
C
S
T
N
E
C
S
T
N
W
198TH
A
V
E
E
AUB
U
R
N
-
B
L
A
C
K
D
I
A
M
O
N
D
R
D
S
E
53RD ST SE
9TH ST E
G
R
E
E
N
R
I
V
E
R
R
D
WE
S
T
V
A
L
L
E
Y
H
W
Y
S
W
EDWARDS RD E
41ST
S
T
S
E
STUCK
R
I
V
E
R
D
R
SE 288TH ST
EA
S
T
V
A
L
L
E
Y
H
W
Y
S
E
16TH ST E
K
E
R
S
E
Y
W
A
Y
S
E
SE 304TH ST
12TH ST E1
9
0
T
H
A
V
E
E
M
S
T
N
E
PER
I
M
E
T
E
R
R
D
8TH ST NE
SE 272ND ST
37TH ST NW
ACADE
M
Y
D
R
S
E
SE LAKE HOLM RD
GREEN VALLEY RD
ORA
V
E
T
Z
R
D
S
E
VA
L
E
N
T
I
N
E
A
V
E
S
E
SE 282ND ST
14
7
T
H
A
V
E
S
E
14
4
T
H
A
V
E
S
E
17TH ST SE
55
T
H
A
V
E
S
1ST AVE SE
18
5
T
H
A
V
E
E
D
S
T
N
W
A
S
T
N
E
JO
V
I
T
A
B
L
V
D
EA
S
T
B
L
V
D
(
B
O
E
I
N
G
)
10
8
T
H
A
V
E
T
A
C
O
M
A
P
O
I
N
T
D
R
E
14
8
T
H
A
V
E
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
169
T
H
A
V
E
E
S 287TH ST
S
C
E
N
I
C
D
R
S
E
S 316TH ST
WE
S
T
B
L
V
D
(
B
O
E
I
N
G
)
H
S
T
N
W
44TH ST NW
14
8
T
H
A
V
E
E
13
7
T
H
A
V
E
E
SE
G
R
E
E
N
V
A
L
L
E
Y
R
D
TH
O
R
T
O
N
A
V
E
S
W
SE 310TH ST
LEA HILL
R
D
S
E
17TH S
T
E
11
8
T
H
A
V
E
S
E
S 3RD AVE
S 3
6
4
T
H
P
L
S 384TH ST
ROY RD SW
J
S
T
N
E
1
2
6
T
H
A
V
E
E
S
2
7
2
N
D
W
A
Y
BR
I
D
G
E
T
A
V
E
S
E
MO
N
T
E
V
I
S
T
A
D
R
S
E
L
S
T
S
E
C
O
T
T
A
G
E
R
D
E
FO
S
T
E
R
A
V
E
S
E
F
S
T
S
E
1ST ST E
G
S
T
S
E
NO
R
M
A
N
A
V
E
S
E
SE 284TH ST
H
O
W
A
R
D
R
D
I
S
T
N
W
14
2
N
D
A
V
E
E
7
8
T
H
A
V
E
S
13
5
T
H
A
V
E
S
E
3RD ST E
8
6
T
H
A
V
E
S
27TH ST E
R
S
T
N
W
85
T
H
A
V
E
S
K
S
T
S
E
S 336TH ST
C
S
T
S
E
SE 301ST ST
SE 287TH ST
2
0
0
T
H
A
V
E
E
Q
U
I
N
C
Y
A
V
E
S
E
29TH ST NW
MI
L
W
A
U
K
E
E
A
V
E
N
56
T
H
A
V
E
S
SKYWAY LN
S
E
32ND PL NE
2
1
1
T
H
A
V
E
E
45TH ST
N
E
7TH ST E
14
0
T
H
A
V
E
S
E
10
5
T
H
A
V
E
S
E
U
C
T
N
W
SE 270TH PL
SE 273RD PL
SE 300TH ST
SR
1
6
7
11
8
T
H
A
V
E
S
E
51
S
T
A
V
E
S
SR
1
6
7
SR
1
6
7
SR 18
SE 284TH ST
SR 18
12
4
T
H
A
V
E
S
E
SR
1
6
7
SE 272ND ST
14
4
T
H
A
V
E
S
E
S
R
1
6
7
S 277TH ST
14
2
15
9
1
5
16
19
8
18
3
4
13
2524
17 6
10
22
21
7
11
20
23
12
COMPREHENSIVE SEWER PLAN
December 2015
L E G E N D
Proposed Gravity Extension
Proposed LPFM Extension
Proposed Force Main Extension
Proposed Pump Station
Existing Pump Stations
King County Sewers
Existing Sewers
Major Roads
Street
County Line
Streams
Water
Parcels
City of Auburn Sewer Service Area
P:\Auburn\145308 Auburn Sewer Comp Plan Update\_GIS\Projects\Plan Figures\fig_5-7_SewerExtensionsCosts.mxd
FIGURE 5-7SEWER EXTENSIONFOR UNSEWERED AREASESTIMATED COSTS
4.050' 8" Pipe - $2,025,000
550' FM - $220,000
1 PS - $500,000
Total - $2,745,000
7,800' 8" Pipe - $3,900,000
6,600' 8" Pipe - $3,300,000
12,200' 8" Pipe - $6,100,000
3,900' 8" Pipe - $1,950,000
5,200' 8" Pipe - $2,600,000
4,800' 8" Pipe - $2,400,000
13 Grinder Pumps - $130,000
1,000' 2" FM - $250,000
Total - $2,780,000
24,000' 8" Pipe - $12,000,000
4 Grinder Pumps - $40,000
1,000' 2" FM - $250,000
Total - $12,290,000
24,200' 8" Pipe - $12,100,000
850' FM - $340,000
1 PS - $500,000
Total - $12,940,000
5,000' 8" Pipe - $2,500,000
7,000' 8" Pipe - $3,500,000
3,100' 8" Pipe - $1,550,000
8,000' 8" Pipe - $4,000,000
2,650' 8" Pipe - $1,325,000
3,200' 8" Pipe - $1,600,000
3,950' 8" Pipe - $1,975,000
4,400' 8" Pipe - $2,200,000
2,250' 8" Pipe - $1,125,000
5,750' 8" Pipe - $2,875,000
2,000' 8" Pipe - $1,000,000
3,950' 8" Pipe - $1,975,000
4,650' 8" Pipe - $2,325,000
2,350' FM - $940,000
1 PS - $500,000
Total - $3,765,000
4,650 8" Pipe - $2,325,000
900' FM - $360,000
1 PS - $500,000
38 Grinder Pumps - $380,000
4,300' 2" FM - $1,075,000
Total - $11,740,000
8,500' 8" Pipe - $4,250,000
2,000 FM - $800,000
1 PS - $500,000
Total - $5,550,000
Rest of City
77,350' 8" Pipe -
$38,675,000
5 Grinder Pumps - $50,000
800' 2" FM - $200,000
Total - $38,925,000
7,900' 8" Pipe - $3,950,000
2,000 FM - $800,000
1 PS - $500,000
Total - $5,250,000
N
3,500 0 3,500 7,000
Feet
2016 Sewer Comprehensive Plan Chapter 5
5-21
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
5.4 Asset Management
All utilities manage their assets in one way or another through maintenance practices, capital
improvement projects, and R&R activities. 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 sewage assets is to establish LOS goals for the City as
described in Chapter 3 of this 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 wastewater assets.
The 2009 Comprehensive Sewer Plan included development of an economic life assessment tool to
help with asset management. An economic life analysis identifies optimal timing for facility
replacement or repair and prioritizes facilities for maintenance attention. The analysis assisted with
achieving the City’s goals for capital program development, which include sustainably meeting
required customer service levels, effectively managing risks, and minimizing the City’s costs of
ownership. The analysis also helped with defining M&O program recommendations and aids the
Utility’s continuing efforts to achieve a proactive maintenance environment. The economic life
assessment tool was a standalone, Excel-based application that required external data to be fed into
the model. Since 2009, the City has migrated to the use of Cartegraph, the City’s CMMS, for systems
operations. With the data in Cartegraph there is the opportunity to migrate the standalone economic
life assessment tool to reside within Cartegraph and run more regularly.
Evaluations completed for this Plan consisted of developing a system requirements specification for
integrating the pipe criticality model into the City’s asset management system, Cartegraph. Once the
pipe inventory is complete (updating GIS to include all required information), and the pipe criticality
model is implemented within Cartegraph, the economic life 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 manholes and pump stations.
Further discussion of asset management, and why and how it can be further used to help manage
the sanitary sewer system, is provided in Section 9.3.
6-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Chapter 6
Maintenance and Operations
This chapter provides an overview of the organization and common procedures associated with the
ongoing maintenance and operation of the City of Auburn sewer utility system, with the primary
purpose of establishing a baseline understanding of the proactive and responsive maintenance
procedures performed by City 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 City sewer system, described in detail in Chapter 4, currently consists of approximately 200
miles of collection system piping, approximately 5,200 manholes, 15 sewer utility pump stations,
and 3 siphons and serves more than 18,000 Utility customers. Utility staff also maintain seven
stormwater pump stations and five sewer pump stations servicing facilities owned by other City
agencies.
6.1 Utility Responsibility and Authority
This section provides an overview of the Utility organization and basic information related to Utility
staffing, training, and education.
6.1.1 Organizational Structure
The Utility is operated as a utility enterprise under the direction of the Community Development and
Public Works Department (CDPW) Director. CDPW is responsible for planning, design, construction,
operation, maintenance, quality control, and management of the sewer system. The City has a
mayor-council form of government; therefore, the CDPW Director reports to the Mayor. The Mayor
and City Council provide oversight for the implementation of policies, planning, and management for
the Utility.
The Engineering Services Division (Engineering) within CDPW is the lead group for comprehensive
sewer system planning; development of a CIP; and the design, construction, and inspection of
projects related to the sewer system. The City Engineer/Assistant Director of Engineering oversees
Engineering and reports directly to the CDPW Director.
The Storm/Sewer Manager oversees the Utility, and is responsible for its day-to-day maintenance
and operation. The Assistant Director of Public Works Operations, who reports to the CDPW Director,
oversees the Storm/Sewer Manager, who in turn oversees 10 employees including a field supervisor.
The location of the Utility within the overall CDPW organizational structure is shown in Figure 6-1.
Chapter 6 2016 Comprehensive Sewer Plan
6-2
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Figure 6-1. City of Auburn Department of Community Development and Public Works organizational chart
6.1.2 Staffing Level
The Utility currently employs nine full-time M&O field staff plus a manager and a field supervisor, who
perform administrative duties. This chapter does not include an evaluation of Utility management,
including regulatory compliance, planning, and coordination with other City departments. The
position titles and primary functions of the full-time M&O field staff working within the Sewer Division
are shown in Table 6-1.
Table 6-1. Sewer Utility M&O Field Personnel
Position Primary function(s)
Sewer/Storm manager Utility administrative duties
Sewer field supervisor Supervision of field staff
Sewer specialist Two full-time staff dedicated to pump station inspection and maintenance
Maintenance worker II Six full-time staff dedicated to field inspection and maintenance
Maintenance worker I One full-time staff dedicated to field inspection and maintenance
2016 Sewer Comprehensive Plan Chapter 6
6-3
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
6.1.3 Level of Service
The 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 include near-term goals, which may not be met by existing
active staff.
6.1.4 Operator Training and Education
The City recognizes the value of having a knowledgeable and well-trained staff operating the Utility,
and encourages employees to obtain the highest level of training available. At this time, the State of
Washington does not require certification for sewer maintenance operators but the City would
support any effort to establish certification for these positions. Seminars, conferences (specifically
the annual Washington Wastewater Collection Personnel Association [WWCPA] conference), and
college coursework have become tools to advance knowledge for maintenance staff with subjects
covered including safety, pumps, generators, forklift training, confined space, first aid, CPR, and
electric and electronic fundamentals.
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, and termination. To mitigate this limitation, the City has broadened
the scope of the Utility’s education system by initiating a formal cross-training program.
6.2 Routine Operations
Routine M&O activities for the Utility can be divided into functional groups by facility type, as
described in the following sections.
6.2.1 Pump Station Maintenance
Utility staff are responsible for maintenance of 27 pump stations, including 15 sewer utility stations
(see Chapter 4), 7 stormwater utility stations, and 5 pump stations serving facilities owned by other
City agencies, at the Auburn Golf Course, Auburn City Hall, Auburn Justice Center, Isaac Evans Park,
and Auburn Valley Humane Society. M&O activities include scheduled weekly and monthly
equipment and grounds maintenance as well as emergency generator testing and maintenance.
Pump station maintenance is a full-time commitment for two Utility staff, including a maintenance
worker and a sewer specialist.
6.2.1.1 Weekly Activities
Weekly pump station inspections are intended as a quick check to ensure proper operation and
performance, and to identify potential non-emergency concerns to be addressed during scheduled
monthly maintenance. Equipment maintenance schedules are based upon manufacturers’
recommendations for preventive equipment maintenance. Depending on the site and time of year,
grounds maintenance may also be performed weekly or postponed for monthly maintenance.
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
Chapter 6 2016 Comprehensive Sewer Plan
6-4
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
• check pump run times
• bleed lines of moisture
• inspect/exercise control valves
• check wet well for debris
• manually run pump and observe wet well level
Weekly inspection activities are intended to be completed in less than 1 hour for each pump station.
6.2.1.2 Monthly Activities
Monthly pump station maintenance activities incorporate weekly activities while allowing more time
for detailed maintenance and to address any concerns identified during previous weekly
maintenance. Monthly maintenance can be particularly important for older pump stations, where
equipment and facilities require more attention. Engine-generators are also inspected and tested on
a monthly basis.
Monthly pump station maintenance activities include the following tasks:
• inspect and test engine-generators (see below)
• 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
Duration of monthly inspection activities varies widely depending upon the age/condition of the
pump station and observations made during previous weekly inspections. On average, monthly
inspections are assumed to be completed within 2 hours at each pump station.
6.2.1.3 Generator Testing and Maintenance
City M&O staff perform limited maintenance on emergency generators serving sewer and stormwater
pump stations, primarily to verify the generator’s ability to perform in an emergency. Emergency
generators are exercised and fuel levels are evaluated during monthly maintenance activities.
Private contracting services are used for detailed generator maintenance. It is recommended that
detailed generator maintenance be performed annually.
Permanent generators are located at all 15 Utility-owned sewer pump stations. Three of the
stormwater pump stations are equipped with permanent engine-generators. During a power outage,
pump stations at City Hall and the Justice Center are run via generators that serve the building.
Those two generators are not maintained by the Utility. Pump stations not served by permanent
generators can be operated using portable generators owned and maintained by CDPW.
6.2.1.4 Wet Well Cleaning and Inspection
Wet well cleaning is performed as needed, but on average is necessary twice annually. Some pump
stations in service areas with a noted high amount of FOG accumulation require cleaning at a higher
frequency (see Section 6.3).
Although the City owns a vactor truck, pump station wet well cleaning is performed by a private
contractor that can more efficiently clean multiple facilities in a single day because of a larger vactor
truck volume. During cleaning, wet wells are drained and the inside is cleaned with high-pressure
water. Accumulated FOG and sludge/sediments are suctioned from the wet well by the contractor
2016 Sewer Comprehensive Plan Chapter 6
6-5
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
and transported to a disposal facility. During cleaning, City staff inspect all floats, sensors, and other
hardware while the wet well is drained and they also visually inspect the wet well structure for
damage.
6.2.2 Collection System Maintenance
Utility staff are responsible for maintenance of approximately 200 miles of collection system piping
and approximately 5,200 manholes. M&O activities include pipe cleaning/jetting, closed-circuit
television (CCTV) inspection, and manhole maintenance.
6.2.2.1 Manhole Maintenance
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. The
inspection includes the following:
• visual confirmation of proper flow conveyance
• assessment of solids buildup in the manhole
• evaluation of structural damage or wear and the integrity/condition of manhole covers and
ladder rungs
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
estimated that approximately 1 in 10 manhole inspections leads to further cleaning. The City
estimates that a total of 50 manholes per year require some repair.
6.2.2.2 Sewer Pipeline Cleaning and CCTV Inspection
Cleaning and inspection of the sewer system is performed using City-owned vactor/jet truck and
CCTV equipment. Cleaning and CCTV inspection are typically performed in tandem from manhole to
manhole by a two- or three-person crew3 for each task.
Jetting of sewer pipelines and subsequent vactor truck removal is the principal means of removing
debris, sludge, FOG, and obstructions from the sewer 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 [psi]) 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. Routine CCTV inspection of the sewer 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 sewer collection system. Since the end of 2007, inspection
reports and digital video captured by the CCTV crews have been stored within the City’s computer
network (PIPELOGIX software). While the ability to edit information in PIPELOGIX is limited to licensed
machines, the PIPELOGIX reader is available for all City staff. Currently, the City does not have the
ability to transfer the data stored in PIPELOGIX, 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
wastewater system assets.
3 Although a three-person crew is assigned to these tasks, work may proceed with a two-person crew (at a slower rate) in
the case of employee absence. The staffing evaluation in Section 6.6 assumes a three-person crew for pipeline cleaning
and CCTV.
Chapter 6 2016 Comprehensive Sewer Plan
6-6
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
The City’s goal is to clean and inspect all sewer collection pipes, using the NASSCO PACP, within the
system on a 5-year cycle 4. On average, a three-person crew can clean approximately 3,000 feet of
pipe per day or inspect approximately 1,500 feet of pipe per day.
6.2.3 Field Operations
In addition to the M&O activities discussed in Sections 6.2.1 and 6.2.2, the Utility typically maintains
a two-person field crew that performs a variety of other ongoing Utility functions. The Utility is also
available to assist other Public Works divisions such as Water, Stormwater, or Transportation during
manpower shortages or emergencies. Sewer staff perform liaison functions with Engineering and
construction inspections for new projects, repairs, or modification of existing lines.
Currently, the services for Utility locates are performed by two designated locators who are under the
supervision of the Water Division Manager.
Examples of field operations activities include:
• Repair: Sewer staff perform repair of minor pipe breaks/leaks and other system infrastructure.
• Engineering: Sewer staff often provide facility inspection services for Engineering projects and
support Engineering through visual observation in the field.
• Vehicle and equipment maintenance: The Utility maintains an extensive inventory of equipment
available to respond to problems or emergencies. The fleet is currently equipped with seven
trucks, one CCTV van, one sewer vactor/jet truck, and one emergency bypass pump. Each
component of this fleet is equipped with valve operators and traffic control equipment.
• Supply inventory: The Utility maintains an inventory of supplies and parts that are available for
use in responding to emergency situations as well as normal Utility operations. Supplies and
parts are tracked in an inventory control system that allows easy identification of available
materials.
It is difficult to quantify the field tasks performed by Utility staff in terms of equivalent staff. Many of
these tasks are performed outside of a regular maintenance schedule. The evaluation of existing
staffing requirements in Section 6.6 assumes that a two-person field operations crew is maintained
for a majority (0.75) of working days, or 1.5 FTE.
6.3 Fats, Oils, and Grease Reduction Program
FOG can cause major blockages in sewer pipes when not properly disposed of at the source. When
FOG enters a sewer, it cools, solidifies, and sticks to the interior of pipes. FOG buildup increases over
time, potentially causing backups in the sewer system and operational concerns within pump
stations. Engineering currently employs a 0.25 FTE water resources technician to implement and
oversee a City FOG Reduction Program. The program focuses on regulation of food service
establishments (FSEs) in order to minimize the amount of FOG entering the City sewer system.
The City currently monitors 170 FSEs within the service area, 76 of which are required to use grease
trap/interceptor pretreatment facilities before discharge to the sewer collection system. FSEs are
identified through the business licensing process, during which all FSEs are required to submit for
approval a FOG control plan per ACC Chapter 13.22. ACC also codifies requirements for installation
of pretreatment facilities (typically grease traps and interceptors), cleaning and maintenance, water
quality testing, and record-keeping. ACC does not have strong language tied to enforcement, nor
4 The frequency goal is specifically intended for all critical areas (serving critical facilities) or piping with a history of repair
or maintenance needs. A lower frequency, approximately every 7 years, for the remainder of the collection system would
not compromise Utility operations.
2016 Sewer Comprehensive Plan Chapter 6
6-7
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
does the City focus on penalties for noncompliance. It is informal City policy to work with FSEs on a
cooperative basis through outreach activities; however, refusal to comply with City requirements can
result in code enforcement action.
The 170 FSEs are grouped informally into 12 geographic areas. The City goal is to concentrate FOG
Reduction Program activities in one area per month, visiting or contacting most FSEs annually.
However, because of limited staffing for the program, inspection and education efforts have focused
on the highest-priority FSEs and areas with noted FOG issues. On average, only 3 of the 12 FSE
areas are inspected or targeted with mailings developed by the City to inform the public and FSEs of
FOG issues. In recent years, maintenance staff has noted, at various times, a high accumulation of
FOG at the Area 19, F Street, Rainier Ridge, Terrace View, and Riverside pump stations. Following
those observations, staff has prioritized those areas for inspections and educational outreach. It is
noteworthy that only one of these stations receives some of its wastewater from FSEs and most
serve areas with high concentrations of multifamily and rental housing. Sewer staff indicate that they
have observed improvements in the accumulation of FOG in the collection system and pump stations
following those efforts, but there is currently no system to quantify FOG reduction.
In addition to efforts to reduce the amount of FOG in the system, education and outreach efforts
include discouraging the flushing of cleaning wipes that may be labeled “flushable,” but that do not
disperse in water. These items can clog sewer lines and get caught in pumps, increasing
maintenance efforts within both the City collection and conveyance system, and King County’s
treatment system.
6.4 Non-Routine and Emergency Operations
This section discusses unscheduled activities performed by sewer M&O staff, and provides a
response plan for emergency conditions. 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
sewer facilities, the potential for conditions that could lead to emergencies.
6.4.1 Customer Service Requests
Customer service requests, such as a localized sewer backup complaint, trigger creation of a work
order to inspect the affected area or sewer facility and identify potential solutions. In some cases,
relatively simple solutions can alleviate the issue. However, other cases require coordination with
Engineering or other City departments. On average, City sewer staff respond to approximately 50
customer service/complaint-related work orders per year. The effort required to resolve 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 greatest extent possible:
• name and contact information of the person making the complaint
• brief description of the nature of the complaint
− if sewer overflow, include estimate of volume and duration of overflow
• time and date the complaint was received
• M&O staff assigned to respond
Following initial response, the complaint record is updated to include the results of inspections and
corrective actions taken, if any. If the complaint cannot be resolved internally within the 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.
Chapter 6 2016 Comprehensive Sewer Plan
6-8
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
6.4.2 Emergency Response Program
The Utility, in conjunction with the other utility divisions, has prepared a Public Works Emergency
Response Manual as a guide on how to handle emergency situations. The manual is by no means all-
inclusive for every type of disaster; however, 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 CDPW M&O Building, at the City Hall Annex with the City Engineer, and at Fire Station
33 with the fire chief.
The Emergency Response Manual is one element of the City’s Comprehensive Emergency
Management Plan. The primary objectives of the Comprehensive Emergency Management 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 Emergency Operations Plan. The material in the Emergency Operations Plan 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 Public Works M&O Building, and the Valley Regional Fire Authority (Station 31).
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 sewer system problems that occur outside
normal working hours are reported through the City’s 911 emergency response system. 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. 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.
6.5 Communications, Data Collection, and Record-Keeping
This section describes the electronic communication, data collection, and record-keeping systems
used by Utility staff.
6.5.1 Telemetry and Pump Station Controls
The Utility uses a computerized system (SCADA) to monitor and operate, as necessary, the sewer and
storm pump stations from a centralized location. SCADA information from all sewer, storm, and water
facilities is routed via radio signals to the M&O control center located at 1305 C Street SW. The
control center monitors wet well levels at all of the sewer pump stations together with pump run
times and cycles.
Logic programming automates the sewer pump station operation via ultrasonic level detectors with
backup high and low float switches. The control center is configured to sound an alarm in the M&O
building if a recognized anomaly is detected. The alarm system is linked to an automatic telephone
dialer that will seek sewer personnel to investigate the anomaly in the event that the problem occurs
during non-working hours. All alarm and pump information is recorded within the computer that
functions as the control center.
The SCADA and telemetry systems were recently updated throughout the sewer system and added to
several previously unserved pump station locations. The completed project provides the City with up-
to-date technology and uniformity throughout the Utility.
2016 Sewer Comprehensive Plan Chapter 6
6-9
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
6.5.2 Data Collection and Record-Keeping
Data collection and record-keeping functions for the 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 wastewater 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 the Cartegraph system and plans to
transition toward its use 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 sewer assets (manhole, pipe segment, pump, etc.).
6.5.2.1 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, as defined below:
− 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., manholes, 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.
6.5.2.2 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: Most work orders should be associated with one or more assets. The asset ID is used
to uniquely associate work with individual 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?
Chapter 6 2016 Comprehensive Sewer Plan
6-10
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
− Cause: What is the underlying cause of the problem?
− Action: What was done to address the cause?
• 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 (PM): Work associated with a planned preventive maintenance
activity
− Predictive maintenance (PdM): Work associated with predictive measures (usually for critical
assets)
• Warranty information: Helps to determine assets that are under warranty and the warranty
maintenance requirements.
6.6 Existing Staffing Requirements
Existing staffing requirements for M&O activities as discussed in this chapter were compiled and
evaluated to determine staffing requirements needed to efficiently operate, maintain, repair, and
collect and report the information necessary to properly operate the sewer system. Table 6-2
evaluates the estimated time to conduct sewer 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.
2016 Sewer Comprehensive Plan Chapter 6
6-11
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Table 6-2. Sewer System Maintenance and Operation Task Summary
Work activity FTE days required
annually Assumptions/City goal
Collection system maintenance
Manhole inspection 22 Inspect once every 4 years, total of 5,200 manholes. Perform 60
inspections per day with one-person crew.
Manhole cleaning 65 One cleaning is required for every 10 inspections. Two-person crew, 2
hours each.
Manhole repair 50 50 repairs per year. Two-person crew, 4 hours each.
Pipeline cleaning 210 City goal is 210,000 ft per year (entire system in 5 years). A three-person
crew can clean 3,000 ft of pipe per day.
CCTV inspection 420 City goal is 210,000 ft per year (entire system in 5 years). A three-person
crew can CCTV-inspect 1,500 ft of pipe per day.
Pump station maintenance
Weekly routine maintenance 263 27 pump stations weekly (52 per year). Two-person crew, 0.75 hour each.
Monthly routine maintenance 162 276 pump stations monthly (12 per year). Two-person crew, 2 hours each.
Wet well cleaning 27 27 pump stations, 2 per year. Two-person crew, 2 hours each.
Other sewer M&O activities
Field operations 330 Two-person field crew for 0.75 of working days (1.5 FTE).
Customer service
requests/complaints 50 50 requests per year. Two-person crew, 4 hours each.
Data entry 260 40 hours per week total.
Subtotal 1,859
Total 2,045 Assumes 10% unquantified work
Total number of working days
available per FTE 200 Based on 10-year average
Number of FTEs required 10.2 2,045 days required divided by 200 days per FTE year.
Current FTEs 9
Table 6-2 shows that the Utility is under-staffed with respect to meeting current City goals for M&O
activities. The analysis confirms the qualitative assessment of staffing adequacy provided by City
staff during workshop discussions. Based upon discussion with City staff, there are portions of the
collection system piping for which there is no CCTV record. Because of limited staff, areas of the
collection system have received higher priority due to frequent need for maintenance (older pipe in
poor condition), relatively flat slopes, or high concentrations of FOG. There will likely be a need for
additional staff to perform more frequent cleaning and CCTV inspection of the entire system and to
account for sewer system expansion with overall city growth. It is recommended that the City
consider hiring two new Utility staff to meet M&O activity goals.
6.7 Potential Improvement Opportunities and Capital Needs
The Utility has a positive track record for M&O, as evidenced by the limited need for non-routine
maintenance and few customer service requests/complaints. Routine facility cleaning, regular
inspections, experienced staff, and a well-planned sewer system contribute to that success.
However, the growing backlog for collection system maintenance (cleaning and CCTV) should be
addressed by the City by adding to the current M&O staff. An additional 2 FTE are required to achieve
current City proactive M&O goals (see Table 6-2).
Chapter 6 2016 Comprehensive Sewer Plan
6-12
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Based upon discussions with City staff and analysis of M&O activities discussed in this chapter, the
following improvement opportunities are available to the Utility. These opportunities are based on
improving existing services and improving work productivity:
• Continue to integrate asset management with existing Utility management software (CMMS and
GIS):
− Continue to add GIS attributes to known 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 NASSCO PACP-certified inspection programs to allow
integration of inspection results with Cartegraph.
− Over time, use the 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.
• Complete inspection of inverted siphons (river crossings, see Section 4.2.4) for which there is no
record of pipe condition. The City does not have the equipment to inspect these facilities;
therefore, contract services will be required.
• Hire one permanent, full-time staff member for CMMS data entry, maintenance tracking, and
reporting. This staff member would support the City Sewer, Stormwater, and Water utilities and
would be a liaison with the City Innovation and Technology (IT) Division.
• Initiate a manhole ring and cover replacement project, targeting a specific percentage of system
assets per year. Results of PM indicate a general deterioration of manhole covers within the
system.
• Based on staff observations regarding the location of maintenance issues caused by FOG
accumulation, continue to manage FSE’s compliance with FOG requirements at its current level,
and increase public education efforts to minimize FOG discharge in residential areas.
7-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Chapter 7
Recommended Plan
This chapter discusses recommended capital projects for the City of Auburn’s sewer system. The
capital projects necessary to meet and maintain the City’s LOS through the 20-year planning period
(2016–35) are presented as a CIP.
This Plan contains time frames, which are the intended framework for future funding decisions and
within which future actions and decisions are intended to occur. However, these time frames are
estimates, and depending on factors involved in the processing of applications and project work, and
availability of funding, the timing may change from the included time frames. The framework does
not represent actual commitments by the City, which may depend on funding resources available.
The identification of projects is an ongoing effort requiring periodic evaluation. This CIP list was
developed based on incorporating the City’s Capital Facilities Program (CFP), identification of
equipment limitations within the M&O group, and identification of areas of improvement.
7.1 Capital Improvement Program
The CIP focuses on addressing known problems in a manner identifying cost-effective solutions that
incorporate the risks associated with underperforming facilities and the uncertainty inherent in
engineering calculations/model simulations. A flow chart depicting the process of CIP development
is shown in Figure 7-1.
Figure 7-1. CIP development flow chart
The CIP places emphasis on projects identified for implementation between 2016 and 2021, which
constitutes the 6-year planning period for utility capital funding requirements and staffing needs.
This period provides a realistic outer limit for accurately forecasting the annual cycle of utility
projects and priorities. This Plan also includes a 20-year CIP that examines long-term capital
requirements, such as the replacement of infrastructure as it exceeds its useful life. All projects in
the CIP are consistent with the LOS described in Section 3 of this document.
Evaluate
system
Define policies and
criteria
Plan capital
projects
Evaluate
costs and
benefits
Complete CIP
Not
Acceptable
Acceptable
Chapter 7 2016 Comprehensive Plan Update
7-2
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
7.1.1 Project Priority
All projects in the CIP have been designated a priority for implementation. Priority was assigned as
one of three designations. Projects in the top tier, or highest priority, are designated priority 1;
projects in the middle tier are designated priority 2; and projects with the lowest priority relative to
the other projects are considered priority 3. The priority levels are based on how the proposed
project impacts LOS. The project descriptions below include the designated priority.
7.1.2 Project Cost
Estimated costs for each project are included in the CIP descriptions below. The costs are planning-
level estimates. Actual costs will depend on various factors at the time of design and construction
including labor and material costs. Estimated costs include an allowance for engineering,
administration, legal fees, construction costs, sales tax, and construction supervision. Permitting and
land, easement, and/or right-of-way acquisitions are not included in the cost estimate. The costs
estimates are in 2014 dollars. CIP projects 1 and 2 are part of the City’s Capital Facilities Program,
where the City developed the costs for these projects.
7.2 Project Summary
The CIP projects mainly consist of ongoing and programmatic capital improvements. Ongoing
projects include projects identified through previous studies. The City has previously allocated
funding to each of these projects, which are currently in various stages of execution. These projects
must continue to receive funding under the CIP until completion and have been included in this
document to provide a complete picture of the program. Programmatic projects are included in the
CIP to provide funding for maintaining and/or improving the LOS. These projects do not address a
problem at a specific location, but allocate budget for addressing LOS goals citywide. As discussed in
Chapter 5, the system hydraulic analysis indicated no need for capacity-related capital projects in the
6-year or 20-year planning period. The next Plan update, scheduled for 2020 and repeating every 6
years, has been included as a cost in Table 7-1; however, there is not a description for the project.
2016 Sewer Comprehensive Plan Chapter 7
7-3
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Table 7-1. Annual Project Cost Summary for 6-Year and 20-Year CIP
Project
number Project name Priority 2016 2017 2018 2019 2020 2021 2022–35 Project Cost
CIP
allocations
(repair/
replacement)
CIP
allocations
(upgrade/
expansion)
1
Sanitary Sewer Repair
and
Replacement/System
Improvements
1 $1,873,000 $300,000 $1,500,000 $300,000 $1,500,000 $300,000 $12,600,000 $18,373,000 100% 0%
2 Street Utility
Improvements 1 $200,000 $200,000 $200,000 $200,000 $200,000 $200,000 $2,800,000 $4,000,000 100% 0%
3 Vactor Decant Facility 1 $150,000 $0 $0 $0 $0 $0 $0 $150,000 0% 100%
4
Sewer Pump Station
Replacement/
Improvement 1 $0 $141,000 $500,000 $168,000 $900,000 $141,000 $2,850,000 $4,700,000 100% 20%
5 Siphon Assessment 1 $0 $524,000 $0 $0 $0 $0 $524,000 $1,048,000 100% 0%
6 Pump Station Condition
Assessment 1 $187,000 $0 $0 $0 $0 $0 $187,000 $374,000 100% 0%
7 Manhole Ring and
Cover Replacement 2 $80,000 $80,000 $80,000 $80,000 $80,000 $80,000 $1,120,000 $1,600,000 100% 0%
8 Cleaning and Inspection
of Large-Diameter Pipe 2 $0 $400,000 $0 $0 $0 $0 $400,000 $800,000 100% 0%
9 Inflow and Infiltration
Study 3 $0 $135,200 $135,200 $135,200 $135,200 $135,200 $0 $676,000 100% 0%
10 Plan Update 1 $0 $0 $0 $0 $350,000 $0 $700,000 $1,050,000 50% 50%
Total cost for priority 1 projects $2,410,000 $1,165,000 $2,200,000 $668,000 $2,950,000 $641,000 $19,661,000 $29,695,000
Total cost for priority 2 projects $80,000 $480,000 $80,000 $80,000 $80,000 $80,000 $1,520,000 $2,400,000
Total cost for priority 3 projects $0 $135,200 $135,200 $135,200 $135,200 $135,200 $0 $676,000
Total CIP cost $2,490,000 $1,780,200 $2,415,200 $883,200 $3,165,200 $856,200 $21,181,000 $32,771,000
Chapter 7 2016 Comprehensive Plan Update
7-4
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Project number 1
Project name Sanitary Sewer Repair and Replacement/System Improvements
Location Throughout the SSSA
Priority 1
Schedule Ongoing, alternating a large project every other year
Problem summary As infrastructure ages, failures begin to appear, causing LOS issues
Description
This project is R&R of existing sewer lines, manholes, public side sewers, and other facilities. These
assets will be identified through closed-circuit television (CCTV) inspection and routine cleaning and
monitoring. This particular program includes proposed projects that do not have an approved Project
Management Plan, or are not associated primarily with the Save Our Streets (SOS) or other
transportation improvements. Anticipated projects include biannual, standalone, R&R projects for sewer
lines that are broken, misaligned, “bellied,” or otherwise require an inordinate amount of maintenance
effort or present a risk of backup or trench failure, and facilities that generate consistent odor
complaints. Improvements identified through this program may be completed as components of larger
projects to gain efficiencies in project costs. Additionally, system improvements that enhance the ability
to maintain service are included here. It is anticipated that the Economic Life model, once developed and
integrated with Cartegraph, will be the source behind planning the R&R program. This project is planned
to occur during both the 6- and 20-year CIPs.
Recommended
predesign
refinements
Refine list as additional information becomes available
Cost estimate Costs developed by the City and carried over from the Capital Facilities Plan
2016 $1,873,000
2017 $300,000
2018 $1,500,000
2019 $300,000
2020 $1,500,000
2021 $300,000
2022–35 $12,600,000
Project Cost $18,373,000
2016 Sewer Comprehensive Plan Chapter 7
7-5
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Project number 2
Project name Street Utility Improvements
Location Throughout the SSSA
Priority 1
Schedule Ongoing
Problem summary As infrastructure ages, failures begin to appear, causing LOS issues.
Description
This project is R&R of existing sewer lines, manholes, and public side sewers located within the project
limits of City arterial transportation projects and within the SOS program. Coordinating sanitary sewer
utility projects with arterial transportation projects can lower the unit cost of pipe replacement by
eliminating the pavement restoration component of the sewer project’s costs. This project is planned to
occur during both the 6- and 20-year CIPs.
Recommended
predesign
refinements
Refine list as additional information becomes available
Cost estimate Costs developed by the City and carried over from the Capital Facilities Plan
2016 $200,000
2017 $200,000
2018 $200,000
2019 $200,000
2020 $200,000
2021 $200,000
2022–35 $2,800,000
Project cost $4,000,000
Project number 3
Project name Vactor Decant Study
Location N/A
Priority 1
Schedule 2016
Problem summary Hauling saturated wastes to County landfills costs operating budget and takes away from crew time,
reducing other work they could be completing.
Description
Currently the City hauls vactored sewage waste to the County landfill on a biweekly basis. The sewage
sludge is considerably wet, thus City funds are paying for the disposal of water. A study is needed to
assess the City’s vactor disposal method and identify a cost-effective alternative to the status quo.
Possible recommendations may include maintaining current operations, constructing a gravity decant
facility, incorporating special equipment into the vactor truck to increase decanting ability, or purchasing
specialized dewatering machinery.
Recommended
predesign
refinements
Identify current City practices, how much sewage waste is vactored, how much liquid can be decanted
from the vactor truck, and the volume and percent water of the waste disposed at the County landfill.
Cost estimate
Engineering services for study $100,000
Subtotal line-item costs $100,000
Project contingency (30% of all above costs) $30,000
Subtotal inspection costs $130,000
Administration (15% of costs) $20,000
Project cost $150,000
Chapter 7 2016 Comprehensive Plan Update
7-6
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Project number 4
Project name Sewer Pump Station Replacement/Improvements
Location Throughout the SSSA
Priority 1
Schedule 2017–22
Problem summary
The 8th Street Pump Station, Valley Meadows Pump Station, and 22nd Street Pump Station have been
identified as needing to be renovated, replaced, and/or relocated based on condition, safety concerns,
and to accommodate growth. This CIP provides for a programmatic program to renovate or replace these
pump stations on a bi-annual basis. The anticipated order for modification/replacement is:
1. 8th Street Pump Station
2. Valley Meadows Pump Station
3. 22nd Street Pump Station
It is anticipated that additional stations will require significant improvements and/or replacement within
the 6 – 20 year planning horizon as well. The sum of the estimated cost for the first three pump stations
is used as a placeholder for project value. Following the results of the systematic pump station
evaluation study scheduled for 2016 (CIP project 6, Pump Station Inspections), the sequence or
identification of pump stations requiring R&R, and detailed scope of improvements for each of these
stations will be developed.
Description This project will renovate or replace the three currently identified pump stations within the 6-year CIP and
allocates money for R&R of unknown pump stations in the 6- to 20-year CIP.
Recommended
predesign
refinements
The Valley Meadows Pump Station is identified as a possible candidate for relocation to allow for future
sewer expansion. The need for relocation should be assessed and planned for prior to 2019. The costs
below for all pump stations do not include provisions for new gravity or force main piping. The costs also
assume that the existing generators on site will be reused and that no additional land or site
improvements are required.
Cost estimate 1. 8th Street Pump Station (2017/2018)
Package pump station $300,000
Project contingency (50% of all above costs) $150,000
Washington State and King County sales taxes (9.5% of all above construction costs) $43,000
Subtotal construction costs $493,000
Administration, engineering design, and permitting (30% of costs) $148,000
Subtotal $641,000
2. Valley Meadows Pump Station (2019/2020)
Package pump station $300,000
Project contingency (50% of all above costs) $150,000
Washington State and King County sales taxes (9.5% of all above construction costs) $43,000
Subtotal construction costs $493,000
Administration, engineering design, and permitting (30% of costs) $148,000
Subtotal $641,000
3. 22nd Street Pump Station (2021/2022)
Package pump station $500,000
Project contingency (50% of all above costs) $250,000
Washington State and King County sales taxes (9.5% of all above construction costs) $72,000
Subtotal construction costs $822,000
Administration, engineering design, and permitting (30% of costs) $246,000
Subtotal $1,068,000
Project cost $2,350,000
2016 Sewer Comprehensive Plan Chapter 7
7-7
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Project number 5
Project name Siphon Assessment
Location Green River crossing near 26th Street NE; Green River crossing over 8th Street NE Bridge; Railroad
crossing near intersection of 6th St. NW and H St. NW
Priority 1
Schedule 2017, positioned in an off year of CIP 1, repeated in 10 years, 2027 or as initial inspection warrants
Problem summary Currently, the City does not have the required equipment to complete inspections of the three siphons
located within its collection system. Their condition is unknown.
Description
This project would inspect each siphon to determine its condition and help set future inspection/cleaning
protocols. The siphons would be inspected prior to cleaning to determine what their in situ condition is,
then if required the lines would be cleaned and re-inspected. Based on the debris level and condition of
the pipes, future activities can be planned. Repeat in 10 years. For cost efficiencies, it is assumed that
all three sites would be completed under one contract. This project is planned to occur during both the 6-
and 20-year CIPs.
Recommended
predesign
refinements
Determine flow rates required for bypass pumping/trucking. Verify the assumption that the Green River
crossing at 26th Street NE can be diverted to each barrel without the need for additional bypass
pumping.
Cost estimate Green River crossing via inverted siphon at 26th Street NE: 488 feet of 8" and 12" HDPE
Initial CCTV $2,500
Cleaning $2,000
Post-cleaning CCTV $2,500
Subtotal $7,000
Green River crossing via 8th Street NE bridge: 1,191 feet of 14" CIP
Traffic control $75,000
Bypass pumping $80,000
Initial CCTV $6,000
Cleaning $4,800
Post-cleaning CCTV $6,000
Subtotal $171,800
Railroad crossing adjacent to H and 6th streets: 287 feet of 18" unknown
Traffic control $20,000
Bypass pumping (trucking) $80,000
Initial CCTV $1,500
Cleaning $1,200
Post-cleaning CCTV $1,500
Subtotal $104,200
Subtotal line-item costs $283,000
Project contingency (30% of all above costs) $85,000
Washington State and King County sales taxes (9.5% of all above construction costs) $35,000
Subtotal construction costs $403,000
Administration, engineering design, and permitting (30% of costs) $121,000
Project cost $524,000
Chapter 7 2016 Comprehensive Plan Update
7-8
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Project number 6
Project name Pump Station Condition Assessment
Location Throughout the SSSA
Priority 1
Schedule 2016 and 2026
Problem summary
The City last completed a pump station condition assessment in 2007. The pump stations have
continued to age, regulations/codes have changed, and the City’s expectations of the pump stations
have changed over time. To adequately plan for future pump station investments, re-inspection is
required.
Description
The assessment will evaluate the apparent physical condition of existing stations and equipment. The
purpose of the assessment is to predict future serviceability and anticipated longevity for development of
future CIPs.
Pump stations must meet the adopted LOS in a safe and reliable manner. Stations must meet current
code conditions, which may differ from those that existed when the stations were originally built. The
assessment would identify requirements necessary to meet the City’s LOS, requirements necessary for
the health and safety of staff and the public, and suggestions that might increase reliability or reduce cost
of operations or maintenance.
Equipment checklists will be prepared for mechanical/hydraulic and electrical/control systems, site visits
to all stations will be made, as-built information and M&O manuals will be reviewed, and M&O personnel
will be asked about known issues at each location. Station operation will be observed, but no detailed
physical testing of equipment, wiring, controls, or structures will be included. To stay up to date on pump
station needs, it is recommended to repeat the inspection within the 20-year CIP.
Recommended
predesign
refinements
None
Cost estimate
Engineering services for condition assessment $125,000
Subtotal line-item costs $125,000
Project contingency (30% of all above costs) $38,000
Subtotal inspection costs $163,000
Administration (15% of costs) $24,000
Project cost $187,000
2016 Sewer Comprehensive Plan Chapter 7
7-9
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Project number 7
Project name Manhole Ring and Cover Replacement
Location Throughout the SSSA
Priority 2
Schedule Ongoing
Problem summary According to M&O staff, there are failing frame and covers on sewer manholes. While the rest of the
manholes are in acceptable condition, the frames and covers need to be replaced.
Description
This project would establish an ongoing CIP to provide funds for continued replacement of frames and
covers. The cost for this effort is based on historical, all-inclusive spending from previous City of Auburn
work. This project is planned to occur during both the 6- and 20-year CIPs.
Recommended
predesign
refinements
None
Cost estimate
Frame and cover replacement $80,000
Subtotal line-item costs $80,000
Project contingency (0% of all above costs) $0
Washington State and King County sales taxes (9.5% of all above construction costs) Included
Subtotal construction costs $80,000
Administration, engineering design, and permitting (0% of costs) $0
Project cost $80,000
Project number 8
Project name Cleaning and Inspection of Large-Diameter Pipe
Location Throughout the SSSA
Priority 2
Schedule 2017, positioned in an off year of CIP 1, repeated in 10 years, 2027 or as initial inspection warrants.
Problem summary According to M&O staff, they are not equipped to efficiently clean pipe larger than 18 inches in diameter.
Description
This project would clean and internally inspect all pipe owned by the City that is larger than 18 inches in
diameter. This is approximately 39,300 feet, ranging in diameter from 20 inches up to 36 inches. This
project is planned to occur during both the 6- and 20-year CIPs.
Recommended
predesign
refinements
Review existing CCTV inspection information to see if any of the large-diameter pipe has been inspected
and determine if it needs cleaning.
Cost estimate
Cleaning $75,000
CCTV $82,000
Disposal $10,000
Traffic control $20,000
Subtotal line-item costs $187,000
Project contingency (50% of all above costs) $94,000
Washington State and King County sales taxes (9.5% of all above construction costs) $27,000
Subtotal construction costs $308,000
Administration, engineering design, and permitting (30% of costs) $92,000
Project cost $400,000
Chapter 7 2016 Comprehensive Plan Update
7-10
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Project number 9
Project name Inflow and Infiltration Study
Location Throughout the SSSA
Priority 3
Schedule Begin 5-year study in 2017
Problem summary
I/I does not appear to be an issue based on capacity. However, little to no work has been done to
actually try and quantify actual I/I rates. This project would assess the City SSSA to determine I/I values.
Excessive localized I/I can also be an indicator of poor sewer main and side sewer condition.
Description This project would monitor flow in the collection system over 5 years. These data will then be used in the
next Comprehensive Sewer Plan for modeling purposes and I/I assessment.
Recommended
predesign
refinements
Analyze existing flow metering and hydraulic model to develop a flow monitoring plan.
Cost estimate
Flow monitoring (four flow meters and two rain gauges for 6 months per year) $365,000
Subtotal line-item costs $365,000
Project contingency (30% of all above costs) $110,000
Washington State and King County sales taxes (9.5% of all above construction costs) $45,000
Subtotal construction costs $520,000
Administration, engineering design, and permitting (30% of costs) $156,000
Project cost $676,000
8-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Chapter 8
Finance
The objective of the financial plan is to identify the total cost of providing sewer service and to
provide a financial program that allows the Utility to remain financially viable during execution of the
identified CIP. This viability analysis considers the historical financial condition of the Utility, the
sufficiency of Utility revenues to meet current and future financial and policy obligations, and the
financial impact of executing the CIP. Furthermore, the plan provides a review of the Utility’s rate
structure with respect to customer affordability.
8.1 Past Financial Performance
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 Utility.
8.1.1 Statement of Revenues, Expenses, and Changes in Net Position
Table 8-1 shows a consolidated statement of revenues, expenses, and changes in net position for
2008–13.
8.1.1.1 Findings and Trends
Operating income (including depreciation expense) has been negative over the entire 6-year
historical period. Operating losses grew from a loss of nearly $556,000 in 2008 to a maximum loss
of $2.3 million in 2011. However, operating income improved significantly in 2012, resulting in a net
loss of only $460,000 and $260,000 in 2012 and 2013, respectively. Depreciation is a non-cash
expenditure, so even though operating income has been negative in every year, cash flow was
positive in most years during the 6-year period.
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 including depreciation 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: Increased from 0.96 in 2008 to 0.99 in 2013, which is a positive trend.
• Operating ratio (total operating expenses excluding depreciation divided by total operating
revenues):
− Benchmark: A ratio greater than 90 percent indicates 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: Decreased from 95 percent in 2008 to 93 percent in 2013, which is a positive
trend overall. However, the operating ratio was at or above 100 percent from 2009 to 2011.
• Debt service coverage ratio (operating and interest revenues less M&O expenses excluding
depreciation, divided by total annual debt service):
Chapter 8 2016 Comprehensive Plan Update
8-2
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
− Benchmark: There are two forms of debt service coverage; one applies to debt service from
revenue bonds only, and the other applies to debt service on total debt, including state
loans. Revenue bonds typically have a legal minimum coverage requirement of 1.25. State
loans usually do not carry a minimum coverage requirement; however, based on industry
standards, it is recommended that debt service coverage on total debt be at least 1.0. To be
conservative, this review of financial statements looks at coverage on total debt.
− Results: Coverage was below industry and City benchmarks from 2009 to 2011, but
increased to 2.4 or above in 2012 and 2013, which is a very favorable trend.
Table 8-1. City of Auburn Statement of Revenues, Expenses, and Changes in Fund Net Position
2008 2009 2010 2011 2012 2013
Operating revenues
Charges for services $13,601,390 $14,902,464 $15,968,231 $16,667,149 $18,585,288 $21,711,948
Other operating revenue 997 102 272 - - -
Total operating revenues 13,602,387 14,902,566 15,968,503 16,667,149 18,585,288 21,711,948
Operating expenses
Operations and maintenance 10,071,648 12,215,275 12,666,971 14,177,079 13,841,985 16,005,927
Administration 1,774,962 2,106,258 1,992,048 1,916,148 1,956,954 2,139,329
Depreciation/amortization 1,282,599 1,390,660 1,372,282 1,603,210 1,746,409 1,886,057
Other operating expenses 1,029,045 1,221,815 1,283,759 1,311,789 1,499,459 1,940,915
Total operating expenses 14,158,254 16,934,008 17,315,060 19,008,226 19,044,807 21,972,228
Operating income (loss) (555,867) (2,031,442) (1,346,557) (2,341,077) (459,519) (260,280)
Non-operating revenue (expenses)
Interest revenue 426,168 137,796 45,053 20,756 32,756 20,442
Other non-operating revenue - 19,820 504,300 843,646 111,224 180,381
Interest expense (20,807) (21,255) (314,931) (156,566) (102,869) (253,574)
Other non-operating expenses (2,177) (2,874) - (1,069) (1,069) (4,782)
Total non-operating revenue
(expenses) 403,184 133,487 234,422 706,767 40,042 (57,533)
Income (loss) before contributions
and transfers (152,683) (1,897,955) (1,112,135) (1,634,310) (419,477) (317,813)
Capital contributions 7,095,833 592,376 4,406,132 7,329,252 1,974,964 3,255,766
Transfers in - 89,425 - - - -
Transfers out (50,000) (50,000) (55,960) (50,000) (50,000) (50,000)
Changes in net position 6,893,150 (1,266,154) 3,238,037 5,644,942 1,505,487 2,887,953
Net position, January 1, as
previously reported 58,764,032 65,657,182 64,391,028 67,629,065 73,274,007 74,779,494
Change in accounting principal (19,250)
Net position, January 1, as restated
74,760,244
Net position, December 31 $65,657,182 $64,391,028 $67,629,065 $73,274,007 $74,779,494 $77,648,197
8.1.2 Statement of Net Position
Table 8-2 shows the consolidated statement of net position for 2008–13.
8.1.2.1 Findings and Trends
This statement shows that the City of Auburn’s net position increased from $65.7 million to
$77.6 million over the 2008–13 time period. This represents an 18 percent increase over the 6-year
2016 Sewer Comprehensive Plan Chapter 8
8-3
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
period. Cash and cash equivalents have grown 13 percent over this period, increasing from $11.3
million in 2008 to $12.8 million in 2013.
Non-current assets, which represent resources required for use or consumption beyond 1 year, have
increased from $54.6 million in 2008 to $71.5 million in 2013. Most of this growth in long-term
assets comes from a $23.4 million increase in improvements other than buildings.
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 an important
question: Are current assets able to cover expected current liabilities in the coming year?
− Results: From 2008 through 2013, this ratio has ranged from 4.8 to 25.4, each year well
above the recommended benchmark. The ratio was 25.4 in 2008, but decreased to 4.8 in
2009 as a result of an increase in current payables and loans payable as well as a decrease
in cash and cash equivalents. The ratio has ranged from 7.4 to 8.8 from 2010 to 2013.
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 44 days in 2008 to 40 days in 2013, which is a positive trend.
Capital
• Debt to net capital assets ratio (total 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 8 percent debt/92 percent equity in 2008 to 12 percent debt/
88 percent equity in 2013. This is well within both the industry and City maximum
benchmark thresholds.
Chapter 8 2016 Comprehensive Plan Update
8-4
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Table 8-2. City of Auburn Statement of Net Position
2008 2009 2010 2011 2012 2013
Assets
Current assets
Cash and cash equivalents $11,337,351 $8,901,147 $8,178,622 $7,855,899 $10,049,455 $12,778,843
Investments 2,003,750 2,023,437 2,009,920 1,996,562 - -
Restricted cash
Bond payments 296,268 307,299 448,108 447,210
Customer deposits 18,471 18,471 16,835 44,053 91,391 95,451
Other 738,017 737,890 4,382,960 1,831,850 514,590 516,972
Customer accounts 1,636,060 1,739,422 2,025,836 1,971,772 2,108,360 2,375,137
Other receivables 37,069 14,217 14,217 100 - -
Due from other governmental units - - - 15,721 - -
Inventories 8,968 8,259 7,414 7,147 6,479 7,009
Total current assets 15,779,686 13,442,843 16,932,072 14,030,403 13,218,383 16,220,622
Non-current assets
Long-term contracts and notes 1,073,400 1,050,900 1,028,400 983,400 938,400 825,900
Capital assets
Land 1,654,958 1,654,958 1,695,023 1,695,023 1,695,023 1,695,023
Buildings and equipment 1,131,744 1,131,744 1,140,893 1,171,259 1,171,259 1,235,992
Improvements other than buildings 65,113,774 65,667,532 73,495,451 80,984,120 87,643,097 88,561,822
Construction in progress 846,620 4,056,688 2,104,633 4,570,300 1,694,876 2,372,710
Less: accumulated depreciation (15,200,016) (16,590,677) (17,962,959) (19,566,169) (21,312,578) (23,198,636)
Total capital assets (net of A/D) 53,547,080 55,920,245 60,473,041 68,854,533 70,891,677 70,666,911
Total non-current assets 54,620,480 56,971,145 61,501,441 69,837,933 71,830,077 71,492,811
Total assets 70,400,166 70,413,988 78,433,513 83,868,336 85,048,460 87,713,433
Liabilities
Current liabilities
Current payables 424,743 1,921,254 473,770 501,844 423,363 627,749
Current deposits 18,471 18,471 16,835 - - -
Loans payable: current - 236,791 288,262 288,262 288,262 288,262
Employee leave benefits: current 69,282 72,952 73,325 90,346 97,848 108,988
Revenue bonds payable: current - - - - 141,162 144,845
General obligation bonds payable: current - - - - - -
Accrued interest 13,183 14,205 309,091 317,569 316,496 311,195
Deposits - - - 44,054 91,391 95,450
Total current liabilities 525,679 2,263,673 1,161,283 1,242,075 1,358,522 1,576,489
Non-current liabilities
Unearned revenue 162,203 162,203 162,203 162,203 162,203 162,203
Employee leave benefits 8,545 24,110 38,336 41,011 33,948 32,500
Loans payable 4,046,557 3,572,974 4,108,241 3,819,979 3,531,717 3,243,456
Revenue bonds payable - - 5,334,385 5,329,062 5,182,577 5,050,589
General obligation bonds payable - - - - - -
Total non-current liabilities 4,217,305 3,759,287 9,643,165 9,352,255 8,910,445 8,488,748
Total liabilities 4,742,984 6,022,960 10,804,448 10,594,330 10,268,967 10,065,237
Net position
Invested In capital assets, net of related debt 53,547,080 52,110,480 54,700,611 60,824,782 61,837,121 61,939,759
Restricted for:
Debt service
720,768 731,596 873,536 964,182
Capital projects 21,398 737,890
-
Unrestricted 12,088,704 11,542,658 12,207,685 11,717,628 12,068,836 14,744,255
Total net position $65,657,182 $64,391,028 $67,629,064 $73,274,006 $74,779,493 $77,648,196
2016 Sewer Comprehensive Plan Chapter 8
8-5
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
8.1.3 Outstanding Debt Principal
Table 8-3 outlines the City’s outstanding debt principal as of the end of 2013.
The City of Auburn has one outstanding revenue bond and two outstanding Public Works Trust Fund
loans. The total outstanding principal on these loans is $8.6 million.
Table 8-3. City of Auburn Outstanding Debt Principal
Debt description Principal outstanding Maturity year
2010 CIP revenue bond $5,086,760 2030
PW-06-962-003 $2,345,433 2026
PW-04-691-001 $1,186,284 2024
Total $8,618,477
8.2 Available Capital Funding Resources
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 Utility’s resources such as
accumulated cash reserves, capital revenues, bond proceeds, and system development charges
(SDCs), capital needs can also be met from outside sources such as grants, low-interest loans, and
bond financing. The following is a summary of internal Utility resources, government programs and
resources, and public debt financing.
8.2.1 Internal Utility Resources
Utility resources appropriate for funding capital needs include accumulated cash in the capital
“account,” bond proceeds, and other capital revenues, such as SDCs. Capital-related revenues are
discussed below.
8.2.1.1 Utility Funds and Cash Reserves
User charges (rates) paid by the Utility’s customers are the primary funding source for all Utility
activities. The rates cover total annual costs associated with operating and maintaining the sewer
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.
8.2.1.2 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 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 utility capital needs;
revenue can be used only to fund utility capital projects or to pay debt service incurred to finance
those projects.
In the absence of an SDC, growth-related capital costs would be borne in large part by existing
customers. In addition, the net investment in the Utility already collected from existing customers,
whether through rates, charges, and/or assessments, would be diluted by the addition of new
customers, effectively subsidizing new customers with prior customers’ payments. To establish
equity, an SDC should recover a proportionate share of the existing and future infrastructure costs
Chapter 8 2016 Comprehensive Plan Update
8-6
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
from a new customer. From a financial perspective, a new customer should become financially
equivalent to an existing customer by paying the SDC.
Table 8-4 summarizes the City’s current SDC schedule.
Table 8-4. City of Auburn Current System Development Charge Schedule
Type Sewer SDC
Single-family parcel $850 per parcel
Other parcels $850 per RCE
An RCE shall be as defined by the King County Department of Natural Resources.
A recent SDC study has been completed and the City Council is currently evaluating the updated
charges.
8.2.1.3 Local Facilities Charge
While an SDC is the manner in which new customers pay their share of general facilities costs, local
facilities funding is used to pay the 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 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 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 to 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.
2016 Sewer Comprehensive Plan Chapter 8
8-7
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
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
developer’s 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 can be rejected by a majority of property ownership within the assessment district
boundary.
8.2.2 Government Programs and Resources
This section outlines government programs and resources potentially available for financing.
8.2.2.1 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. There are many grant and loan programs that
the City might be eligible for, described in greater detail below.
8.2.2.2 Department of Commerce
A September 2014 document from the Washington State Department of Commerce summarizes
various loan and grant programs available (“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, primarily offers low-cost loans; grants are made available only to the
extent that a loan is not reasonably possible. The CERB targets public facility funding for
economically disadvantaged communities, specifically for job creation and retention. Priority criteria
include the unemployment rates, number of jobs created and/or retained, wage rates, projected
private investment, and estimated state and local revenues generated by the project. 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 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 website:
“$9 million was appropriated to CERB for the 2013-2015 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.” (See Table 8-5)
Chapter 8 2016 Comprehensive Plan Update
8-8
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Table 8-5. Funding Programs
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)
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/CE
RB-Traditional-Programs.aspx
Public Works Board (PWB) Financial Assistance. The PWB’s overarching 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.
2016 Sewer Comprehensive Plan Chapter 8
8-9
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
− 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.
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
8.2.2.3 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 a
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
8.2.3 Public Debt Financing
This section describes potentially available public debt financing tools.
8.2.3.1 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.
(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.
Chapter 8 2016 Comprehensive Plan Update
8-10
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
8.2.3.2 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.
8.2.4 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 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-Utility) purposes, revenue bonds are a more secure
financing mechanism for 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
The 20-year CIP is expected to be funded from cash reserves and non-debt capital revenues.
8.3 Financial Plan
The City of Auburn’s Sewer 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 Utility is collections from sewer 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 sewer service—both operating and capital. To meet these
objectives, the following elements are completed:
• Capital funding plan: The capital funding plan identifies the total CIP obligations for the planning
period 2014–35, although the capital plan identified in this Plan begins with 2016. The capital
funding 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 may
impact the financial plan through use of debt financing (resulting in annual debt service) and the
2016 Sewer Comprehensive Plan Chapter 8
8-11
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
assumed rate revenue resources available for capital funding. The capital funding plan is
discussed in Section 8.3.3.
• Financial forecast: This forecast identifies annual non-capital costs associated with the
operation, maintenance, and administration of the sewer system. Included in the financial plan
is a reserve analysis that forecasts cash flow and fund balance activity along with testing for
satisfaction of actual or recommended minimum fund balance policies. The financial plan
ultimately evaluates the sufficiency of Utility revenues in meeting all obligations, including
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 8.4.
8.3.1 Utility Fund Structure
The City tracks the Utility’s revenues and expenditures in two funds: Fund 431 Sewer and Fund 433
Sewer Metro. The revenues and expenditures of both funds are included in the “combined” financial
forecast. Conceptually, Utility expenditures can be divided into three main types of costs: operating,
capital, and debt service. For modeling purposes, the “combined” sewer utility is split among three
“accounts” as is bulleted below: 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 8.4.
• Operating: Serves as an operating account where operating revenues are deposited and
operating expenses are paid.
• Capital: 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.
• Debt reserves: Serves as a restricted account set up to comply with debt covenants.
Splitting the funds 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 the next section.
8.3.2 Financial Policies
A brief summary of the City’s adopted and or recommended financial policies follows below. Adopted
policies are based on the City’s “Process/Policies” section within the 2015–16 budget.
8.3.2.1 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; and meeting utility
debt obligations. 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
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
Chapter 8 2016 Comprehensive Plan Update
8-12
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
appropriate for utilities with significant seasonal or consumption-based fluctuations (such as
most water utilities).
The City’s adopted policy states that the Sewer Utility’s target operating reserves should be
approximately 60 days (page 36, “Process/Policies”). This is the target used in the financial
forecast. Based on the City’s 2015 budgeted local expenditures (excluding depreciation and the
King County Metro remittance), a 60-day target equates to $1.1 million in 2015.
• Capital contingency reserve: A capital contingency reserve is an amount of cash set aside in
case of an emergency should a piece of equipment or a portion of the Utility’s infrastructure fail
unexpectedly. Additionally, the reserve could be used for other unanticipated capital needs
including capital project cost overruns. There are various approaches to identifying an
appropriate level for this reserve, such as (1) identifying a percentage of a utility system’s total
fixed assets, and (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 bonded debt service is targeted.
8.3.2.2 System Reinvestment Policies
The purpose of system reinvestment funding is to provide for the replacement of aging system
facilities to ensure sustainability of the system for ongoing operation. Each year, the Utility’s assets
lose value, and as they lose value they 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.
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 10 percent and increases by
10 percent per year until 100 percent of the target is funded.
8.3.2.3 Debt Policies
Bond covenants often establish a minimum debt coverage ratio as a means of protecting an agency
against the risk of nonpayment. The industry’s standard minimum coverage ratio is 1.25 times
annual revenue bond debt service. The City’s policy matches this industry standard.
The City also identifies another debt level related policy, which is to maintain a capital ratio of
50 percent debt to 50 percent equity. The industry standard is a maximum of 60 percent debt to
40 percent equity. The City’s capital ratio from the 2013 financial statement was well below that
threshold at approximately 12 percent debt to 88 percent equity. The forecast estimates that the
debt level will not exceed 12 percent debt in the 20-year planning period.
8.3.3 Capital Funding Plan
The CIP developed for this Plan contains 10 different projects valued at $33 million ($49 million
inflated) over the 2016–35 planning period. Capital expenditures for 2014 and 2015 are based on
2016 Sewer Comprehensive Plan Chapter 8
8-13
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
estimated and budgeted amounts, respectively. 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 8-6 summarizes the expected annual capital expenditures.
Table 8-6. City of Auburn Sewer CIP
Year 2014 $ Inflated $
2014 $ 2,405,393 $ 2,405,393
2015 $ 2,300,934 $ 2,381,467
2016 $ 2,490,000 $ 2,667,350
2017 $ 1,780,200 $ 1,973,740
2018 $ 2,415,200 $ 2,771,498
2019 $ 883,200 $ 1,048,965
2020 $ 3,165,200 $ 3,890,839
2021 $ 856,200 $ 1,089,326
8-year total $ 16,296,327 $ 18,228,576
2022–35 $ 21,181,000 $ 35,231,899
Grand total $ 37,477,327 $ 53,460,475
A capital funding plan is developed to determine the total resources available to meet the CIP needs
and determine if new debt financing will be required. After allocating the estimated beginning 2015
fund balance first to the debt reserve and secondly to the operating reserve, nearly $9 million was
available for capital.
The SDC is projected to generate an average annual revenue stream of just over $630,000 through
2021. This is based on an assumed customer growth rate of 2 percent per year. The customer
growth percentage is drawn from a review of the previous 8 years of actual customer growth (2008–
15).
The SDC revenue projection assumes the current SDC of $850 plus an annual Construction Cost
Index adjustment starting in 2015. The City Council is currently reviewing an update of the SDCs.
A summary of the capital funding plan is summarized in Table 8-7. The analysis shows that the CIP
can be fully funded using cash reserves and non-debt capital revenue; no new debt is required.
Table 8-7. City of Auburn Capital Financing Plan
Year Capital
expenditures
Capital
expenditures
inflated
Revenue bond
financing Cash funding Total financial
resources
2014 $ 2,405,393 $ 2,405,393 $ - $ 2,405,393 $ 2,405,393
2015 2,300,934 2,381,467 - 2,381,467 2,381,467
2016 2,490,000 2,667,350 - 2,667,350 2,667,350
2017 1,780,200 1,973,740 - 1,973,740 1,973,740
2018 2,415,200 2,771,498 - 2,771,498 2,771,498
2019 883,200 1,048,965 - 1,048,965 1,048,965
2020 3,165,200 3,890,839 - 3,890,839 3,890,839
2021 856,200 1,089,326 - 1,089,326 1,089,326
8-year total $ 16,296,327 $ 18,228,576 $ - $ 18,228,576 $ 18,228,576
2022–35 $ 21,181,000 $ 35,231,899 $ - $ 35,231,899 $ 35,231,899
Grand total $ 37,477,327 $ 53,460,475 $ - $ 53,460,475 $ 53,460,475
Chapter 8 2016 Comprehensive Plan Update
8-14
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
8.4 Financial Forecast
The financial forecast, or revenue requirement analysis, forecasts the amount of annual revenue
that needs to be generated by rates throughout the 2015–21 planning period. The analysis
incorporates operating revenues, M&O expenses, debt service payments, rate-funded capital needs,
and any other identified revenues or expenses related to utility operations, and determines the
sufficiency of the current level of rates. Revenue needs are also impacted by debt covenants
(typically applicable to revenue bonds) and specific fiscal policies and financial goals of the Utility.
For this analysis, two revenue sufficiency “tests” have been developed to reflect the financial goals
and constraints of the 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.
8.4.1 Cash Flow Test
The cash flow test identifies all known cash requirements for the Utility in each year of the planning
period. Capital needs are identified and a capital funding strategy is established. This may include
the use of debt, cash reserves, outside assistance, and rate funding. Cash requirements to be
funded from rates are determined. Typically, these include M&O expenses, debt service payments,
system reinvestment funding or directly funded capital outlays, and any additions to specified
reserve balances. The total annual cash needs of the Utility are then compared to total operating
revenues (under current rates) to forecast annual revenue surpluses or shortfalls.
8.4.2 Coverage Test
The coverage test is based on a commitment made by the City when issuing revenue bonds. As a
security condition of issuance, the City is required per covenant to agree that the revenue bond debt
would have a higher priority for payment (a senior lien) compared to most other Utility expenditures;
the only outlays with a higher lien are M&O expenses. Debt service coverage is expressed as a
multiplier of the annual revenue bond debt service payment. For example, a 1.0 coverage factor
would imply that no additional cushion is required. A 1.25 coverage factor means revenues must be
sufficient to pay M&O 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 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 Utility must also meet debt covenant
requirements and minimum reserve level targets.
8.4.3 Financial Forecast
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 portrayal of the Utility’s annual financial
obligations. The forecast covers the 2015–21 planning period. The following is a list of the key
revenue and expense factors and assumptions used to develop the forecast.
2016 Sewer Comprehensive Plan Chapter 8
8-15
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
8.4.3.1 Revenue and Fund Balance Assumptions
The following revenue and fund balance assumptions are used to develop the forecast:
• Customer growth and demand: Based on a review of historical data from 2008 to 2015, annual
customer account growth has averaged approximately 2 percent. To be consistent with the
Water financial forecast, annual water use per account is projected to decline by 1 percent per
year until 2027. Because the residential rate structure is flat, the decline in usage in that class
would not affect rate revenues. Therefore, the 1 percent decline applies only to the variable
portion of sewer rate revenues. The net effect of 2 percent customer account growth and 1
percent decline in non-residential usage per account results in a composite rate revenue
increase of 1.5 percent per year.
• Adopted rate increases: The City has adopted annual rate increases through 2017 of roughly 2.5
percent, which are incorporated into the revenue figures within 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, sewer 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 estimated beginning balance in 2015 for Fund 431. This
balance was allocated to the “accounts” using the following methodology:
1. Debt reserve: amount equal to highest annual bonded debt service on existing debt
2. Operating reserve: amount equal to the operating reserve target of 60 days
3. Capital reserve: remaining funds
The estimated beginning fund balance in 2015 was approximately $10.8 million, which is
enough to fully fund the debt reserve, and provide 60 days in the operating reserve, leaving
nearly $9 million to fund the capital reserve. The fund balance for Fund 433 (Sewer Metro
reserve) remains in that fund and is not used in this financial forecast.
8.4.3.2 Expenditures and Other Miscellaneous Assumptions
The following expenditures and other miscellaneous assumptions are used to develop the forecast:
• Interest earnings initially assume a rate of 0.09 percent applied to beginning-of-year cash
balances based on existing Local Government Investment Pool rates, phasing toward
0.25 percent over the long term.
• General operating expenses are escalated from the budgeted figures at 2.5 percent per year,
labor costs increase at 2.5 percent per year, and benefits at 5.5 percent per year.
• State taxes are calculated based on prevailing tax rates.
• Existing debt service schedules were provided by the City and include one existing revenue bond
issue as well as two Public Works Trust Fund loans. These obligations represent nearly
$728,000 in annual debt service as of 2015.
• The King County Metro charges were modeled as a “pass through”—revenues equal to
expenditures. Metro Service revenues were calculated using each year’s estimated number of
RCEs and the corresponding year’s monthly service charge. Projected monthly charges were
based on the County’s estimated rate schedule through 2020, with inflationary adjustments
assumed beyond 2020. Industrial surcharges were increased at the same rate as the monthly
service charge.
• This Plan identifies additional staffing needs above the 2015 and 2016 budgeted levels, which
total over $232,000 per year beginning in 2017:
Chapter 8 2016 Comprehensive Plan Update
8-16
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
− Asset management specialist (0.5 FTE): salary and benefits of $46,000 per year (note: the
other 0.5 FTE is to be included within the City’s Storm Drainage Utility)
− Maintenance worker II (1 FTE): salary and benefits of $93,000 per year
− Maintenance worker II (1 FTE): salary and benefits of $93,000 per year
• The rate strategy focuses on the 2015–21 planning period. It is imperative that the City 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 8-8 summarizes the annual revenue requirement through 2021 based on the forecast of
revenues, expenditures, fund balances, fiscal policies, and capital funding.
In 2012, the City Council adopted annual rate increases of 2.5 percent in each of 2015, 2016, and
2017. The financial analysis shows that the adopted rates generate sufficient revenue to meet
operating expenses and the 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.
Rate increases averaging about 3.3 percent per year are needed in 2018 and beyond to cover
projected M&O expenses, debt service payments, system reinvestment funding, and other stated
financial policy objectives.
Table 8-8. City of Auburn Financial Forecast
Revenue requirements 2014 2015 2016 2017 2018 2019 2020 2021
Assuming existing rates
Revenue
Local rate revenues $7,428,178 $7,729,650 $8,042,305 $8,366,484 $8,491,446 $8,618,273 $8,746,995 $8,877,640
Non-rate revenues + King County Metro sewer 15,957,246 16,446,729 16,759,701 18,162,930 18,840,675 19,570,948 20,318,501 21,214,937
Total revenue $23,385,424 $24,176,380 $24,802,006 $26,529,415 $27,332,121 $28,189,221 $29,065,496 $30,092,577
Expenses
Cash operating expenses $22,580,466 $23,073,590 $23,212,150 $25,130,173 $26,032,966 $26,998,699 $27,989,485 $29,146,421
Operating expense per RCE a 739 735 786 805 826 846 868
Existing debt service 730,191 728,283 727,038 817,610 815,874 814,887 813,347 811,255
Debt service per RCE a 23.3 23.0 25.6 25.2 24.9 24.6 24.3
New debt service - - - - - - - -
Rate-funded system reinvestment - 157,565 323,428 471,687 640,778 822,550 992,282 1,203,542
Additions to operating reserve - - - - 36,606 38,226 35,922 45,855
Total expenses $23,310,657 $23,959,438 $24,262,616 $26,419,470 $27,526,224 $28,674,362 $29,831,036 $31,207,072
Cash surplus/(deficiency): before rate increases $74,767 $216,942 $539,389 $109,945 $(194,104) $(485,140) $(765,540) $(1,114,495)
Annual rate adjustment 0.00% 0.00% 0.00% 2.54% 3.62% 3.26% 3.85%
Cumulative annual rate adjustment 0.00% 0.00% 0.00% 2.54% 6.25% 9.71% 13.94%
After rate increases:
Local rate revenues $7,428,178 $7,729,650 $8,042,305 $8,366,484 $8,706,904 $9,156,786 $9,596,757 $10,114,747
Cash surplus/(deficiency): after rate increases 74,800 216,900 539,400 109,900 36,600 38,200 35,900 45,900
Debt service coverage: revenue bonds 5.82 6.72 7.98 6.42 6.72 7.18 7.63 8.20
Debt service coverage: all debt 3.38 3.91 4.66 4.05 4.25 4.55 4.84 5.21
a. Existing 31,230 RCE within the service area, as of June 2015. Assumed RCE growth is consistent with service area population
growth assumed for Hydraulic Capacity Analysis (Chapter 5 and Appendix B).
2016 Sewer Comprehensive Plan Chapter 8
8-17
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
The last two rows of Table 8-8 show the projected debt service coverage for both bonded debt and
total debt. Bonded debt service coverage—which legally cannot drop below 1.25—is projected to stay
at or above 5.8 throughout the life of the forecast. Debt service coverage for total debt (including
state loans) is recommended to be at least 1.0, and throughout the life of this forecast, it is
projected to stay at or above 3.4.
Table 8-8 includes projections of operating and debt service costs per RCE (see Section 2.3). RCE
operating costs are anticipated to increase within the planning period. The increase will occur
primarily because of the need for additional staff, who are needed for existing and anticipated new
system M&O tasks to maintain level of service as identified in previous chapters. Operating costs are
also anticipated to grow at a greater rate than assumed RCE growth. Per RCE debt service is not
projected to vary significantly within the planning period. No new debt service costs are anticipated.
8.4.4 City Funds and Reserves Balances
Table 8-9 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 $3.3 million, which is above the minimum target of $1.1 million; and the debt
reserve ends at $0.5 million, which is enough to cover 1 year of annual bonded debt service.
Table 8-9. City of Auburn Cash Balance Summary
Ending reserves 2014 2015 2016 2017 2018 2019 2020 2021
Operating $1,139,255 $1,132,900 $1,101,349 $1,188,469 $1,225,076 $1,263,302 $1,299,223 $1,345,078
Capital 9,487,763 7,686,286 6,496,031 5,627,941 4,139,325 4,586,275 2,399,129 3,258,276
Debt 516,173 516,173 516,173 516,173 516,173 516,173 516,173 516,173
Total $11,143,190 $9,335,358 $8,113,553 $7,332,583 $5,880,574 $6,365,749 $4,214,525 $5,119,527
8.5 Existing Rate Structure and Projected Schedule
The City’s existing sewer rate structure for inside City customers is composed of two rate classes.
The residential rate schedule consists of a monthly base charge. The non-residential rate schedule
consists of both a monthly base charge and a volume charge based upon the amount of water used
as measured in 100-cubic-foot (ccf) increments above the initial allowance.
Residential sewer utility customers residing outside of the City’s political boundaries are assessed
charges based upon the inside City rate plus a 50 percent premium (ACC 13.06.360). 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).
A recent detailed review of the City’s rate structure has been completed in the 2014 Retail Rate
Study. The review recommended increasing the volume charge while maintaining the current base
charge through 2017. This phases the existing rate structure toward a more standard definition of
7.5 ccf of implicit usage included in the monthly base charge.
Table 8-10 presents the City’s existing sewer 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.
Chapter 8 2016 Comprehensive Plan Update
8-18
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Table 8-10. City of Auburn Projected Local Rate Schedule
Monthly rate schedule Adopted Adopted Adopted Adopted Projected Projected Projected Projected
2014 2015 2016 2017 2018 2019 2020 2021
Annual 0.0% 0.0% 0.0% 2.5% 3.6% 3.3% 3.8%
Cumulative 0.0% 0.0% 0.0% 2.5% 6.2% 9.7% 13.9%
Residential
Base $23.12 $23.69 $24.29 $24.89 $25.52 $26.45 $27.31 $28.36
Non-residential
Base (first 750 cf) $23.12 $23.69 $24.29 $24.89 $25.52 $26.45 $27.31 $28.36
Volume (additional 100 cf) $2.34 $2.39 $2.45 $2.52 $2.58 $2.68 $2.76 $2.87
Low-income discount: 50%.
Outside city multiplier: 1.50.
King County Metro rates not included in rate forecast.
Rate increases shown in 2015, 2016, and 2017 reflect already-adopted annual increases of 2.5%.
8.6 Affordability
The Washington State Department of Health and Public Works Board has 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 8-11 presents the City’s estimated single-family sewer rate with the projected
rate increases for the forecast period. The affordability mark (monthly bill*12 ÷ median income)
averages 0.5 percent throughout the study period. As shown in Table 8-11, the City’s local sewer
rates remain well within the affordability range throughout the planning period. If the County’s
monthly charge is included in this calculation, the affordability mark averages 1.5 percent.
Table 8-11. City of Auburn Affordability Test
Year Inflation Median
HH income
Projected
monthly
bill (local
only)
% of
median
HH income
2014 2.50% $51,810 $23.12 0.54%
2015 2.50% $53,106 $23.69 0.54%
2016 2.50% $54,433 $24.29 0.54%
2017 2.50% $55,794 $24.89 0.54%
2018 2.50% $57,189 $25.52 0.54%
2019 2.50% $58,619 $26.45 0.54%
2020 2.50% $60,084 $27.31 0.55%
2021 2.50% $61,586 $28.36 0.55%
Monthly bill assumes residential local rate only.
2016 Sewer Comprehensive Plan Chapter 8
8-19
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
8.7 Conclusion
The financial analysis indicates that the adopted rates in 2015, 2016, and 2017 are sufficient to
meet the Utility financial obligations as presented herein. No additional rate increases are proposed
for 2015–17. Based on the forecast, required rate increases for 2018–21 average about 3.3
percent per year for a cumulative rate increase of 13.9 percent. The financial forecast shows that no
new debt is expected to be required to fund the identified capital program within this Plan.
This evaluation also finds that the local sewer rates with projected rate increases would remain
within the defined threshold of affordability.
9-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Chapter 9
Implementation Plan
Building upon the M&O activities outlined in Chapter 6 and the projects described in Chapter 7 , this
chapter presents a work plan for future Utility activities. Critical elements of the plan (e.g., CIP
implementation and criticality-based maintenance plans) are presented and a planning-level
schedule is provided to guide the Utility’s activities in the coming years.
For discussion, plan implementation is divided into two sections:
• presentation of the CIP for both 6- and 20-year time frames
• description of the steps forward in order to implement the activities described in this chapter.
Funding for these activities is described in a separate rate analysis study prepared in conjunction
with the overall Sewer Plan.
The timeline at the conclusion of this chapter shows the proposed implementation schedule.
9.1 6-Year and 20-Year CIP
The 6-year CIP contains projects identified by the City as requiring immediate action. The 6-year CIP
also contains general improvement projects allowing for annual R&R of facilities in the next 6 years.
Details regarding these projects are provided in Chapter 7. The 6-year CIP is shown in Table 9-1.
Table 9-1. Annual Project Cost Summary for 6-Year CIP (in millions of dollars)
Project
number Project name Priority 2016 2017 2018 2019 2020 2021
6-year
project
cost
1
Sanitary Sewer Repair and
Replacement/System
Improvements
1 $1.873 $0.300 $1.500 $0.300 $1.500 $0.300 $5.773
2 Street Utility Improvements 1 $0.200 $0.200 $0.200 $0.200 $0.200 $0.200 $1.200
3 Vactor Decant Study 1 $0.150 $0.000 $0.000 $0.000 $0.000 $0.000 $0.150
4 Sewer Pump Station
Replacement/Improvement 1 $0.000 $0.141 $0.500 $0.168 $0.900 $0.141 $1.850
5 Siphon Assessment 1 $0.000 $0.524 $0.000 $0.000 $0.000 $0.000 $0.524
6 Pump Station Condition
Assessment 1 $0.187 $0.000 $0.000 $0.000 $0.000 $0.000 $0.187
7 Manhole Ring and Cover
Replacement 2 $0.080 $0.080 $0.080 $0.080 $0.080 $0.080 $0.480
8 Cleaning and Inspection of
Large-Diameter Pipe 2 $0.000 $0.400 $0.000 $0.000 $0.000 $0.000 $0.400
9 Inflow and Infiltration Study 3 $0.000 $0.135 $0.135 $0.135 $0.135 $0.135 $0.676
10 Plan Update 1 $0.000 $0.000 $0.000 $0.000 $0.350 $0.000 $0.350
Total 6-year CIP cost for priority 1 projects $2.410 $1.165 $2.200 $0.668 $2.950 $0.641 $10.034
Total 6-year CIP cost for priority 2 projects $0.080 $0.480 $0.080 $0.080 $0.080 $0.080 $0.880
Total 6-year CIP cost for priority 3 projects $0.000 $0.135 $0.135 $0.135 $0.135 $0.135 $0.676
Total 6-year CIP cost $2.490 $1.780 $2.415 $0.883 $3.1615 $0.856 $11.590
Chapter 9 2016 Comprehensive Sewer Plan
9-2
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
The CIP after the 6-year time period includes ongoing programmatic efforts to develop projects for
facility repair or replacement, including projects based on the City’s asset management tools. The
projects proposed for expenditures in the years 2022 to 2035, and an estimate of total CIP costs for
the 20-year period from 2014 through 2035, are shown in Table 9-2.
Table 9-2. Cost Summary for 20-Year CIP (in millions of dollars)
Project
number Project name Priority
Project costs for
2022–35
(2014 dollars)
1 Sanitary Sewer Repair and Replacement/System Improvements 1 $12.600
2 Street Utility Improvements 1 $2.800
3 Vactor Decant Study 1 $0.000
4 Sewer Pump Station Replacement/Improvement 1 $2.850
5 Siphon Assessment 1 $0.524
6 Pump Station Condition Assessment 1 $0.187
7 MH Ring and Cover Replacement 2 $1.120
8 Cleaning and Inspection of Large-Diameter Pipe 2 $0.400
9 Inflow and Infiltration Study 3 $0.000
10 Plan Update 1 $0.700
Total 2022–35 CIP cost for priority 1 projects $19.661
Total 2022–35 CIP cost for priority 2 projects $1.520
Total 2022–35 CIP cost for priority 3 projects $0.000
Total 2022–35 CIP cost $21.181
Total 20-year CIP cost $32.771
9.2 Monitoring
The King County flow monitoring and hydraulic modeling completed as part of this Sewer Plan
identified areas with high levels of I/I. As discussed in Section 5.2, the levels of I/I are not currently
problematic. However, it is recommended the City initiate the first steps of an I/I control program
(CIP project 9, Section 6.2) to proactively address potential concerns.
The first step in the program is to select flow metering locations. The budget of CIP project 9
assumed four flow monitors and two rain gauges for six months per year. The suggested initial flow
monitoring locations (manhole IDs) for year 1 of CIP project 9 are:
• 410-77
• 611-34
• 611-08
• 610-30
The hydraulic characteristics of exact locations should be examined prior to placement of flow
meters to maximize flow metering accuracy. The City should also use the recently upgraded SCADA
system to compile pump station pump run times and corresponding wet well levels.
2016 Comprehensive Sewer Plan Chapter 9
9-3
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
9.3 Asset Management and Maintenance and Operation
Asset management is a defined process for managing facilities and activities that will optimize the
life-cycle cost of Utility assets as well as to ensure that the Utility meets defined service levels. The
economic life model developed for the 2009 Comprehensive Sewer Plan and the recently developed
specification to migrate this model to Cartegraph is an example of a criticality-based approach to
deciding the optimal timing for repair or replacement of existing utility facilities. This method can also
be used for managing risks to the performance of sewers and force mains through maintenance
strategies. It is recommended that the City continue the business practice of asset management. To
help accomplish this, the City should fully populate its GIS information and implement the economic
life model within Cartegraph.
9.3.1 Collect Asset Data
The sanitary sewer system is a complex network of pipes and pump stations that collect and convey
wastewater produced within the city to the King County collection system. Not all system attributes
are currently included in the City’s CMMS database or GIS. Static attributes like material, size, and
installation dates can be updated anytime and the condition of each asset should be updated
following inspection. Figure 9-1 shows a map of the City’s sewer system (pipes) that have some of
the static attribute information missing and that need to be updated. Please note that an indication
that asset information is missing indicates that at least one particular attribute is not currently in the
CMMS database. Generally, that information exists elsewhere in City archives (as-built drawings,
etc.), but will be far more useful for managing the Utility’s assets when it has been compiled in the
CMMS.
Chapter 9 2016 Comprehensive Sewer Plan
9-4
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
GreenRiver
LakeTapps
BigSoos C re e k
MillCreek
167
18
AUB
U
R
N
W
A
Y
S
B
S
T
N
W
37TH ST NE
WE
S
T
V
A
L
L
E
Y
H
W
Y
N
W
15TH ST NW
W MAIN ST
K
E
R
S
E
Y
W
A
Y
S
E
53RD ST SE
A
U
B
U
R
N
W
A
Y
S
SE 304TH ST
SE 312TH ST
11
2
T
H
A
V
E
S
E
C
S
T
S
W
A
S
T
S
E
ELLINGSON RD SW
WhiteRiver
15TH ST SW
PE
R
I
M
E
T
E
R
R
D
S
W
CL
A
Y
S
T
N
W
Lea HillSewer Basin
South Hill Sewer Basin
Valley SewerBasin
King County
Pierce County
Auburn Way SouthSewer Basin
West HillSewerBasin
Pacific
Dogwood
Verdana
Safeway
Area 19
R Street
F Street
Auburn 40
Riverside8th Street
North Tapps
22nd Street
Auburn Jail
Terrace View
Rainier RidgePeasley Ridge
Lakeland Hills
Valley Meadows
Ellingson Road
Issac Evans Park
Auburn Golf Course
Auburn Justice Center
Auburn Valley Humane Society
COMPREHENSIVE SEWER PLAN
December 2015 FIGURE 9-1SANITARY SEWERSWITH MISSING ATTRIBUTEINFORMATION
3,500 0 3,500 7,000
Feet N
P:\Auburn\145308 Auburn Sewer Comp Plan Update\_GIS\Projects\Plan Figures\fig_4-2_ExistingWastewaterConveyanceSystem11x17.mxd
L E G E N D
Auburn Sewers with All Populated Information
Auburn Sewers with Missing Information
King County Sewers
Auburn Pump Station
King County Pump Station
Private Pump Station
City of Auburn Sewer Service Area
Major Roads
Street
County line
Streams/Rivers/Ponds
AUBURNSSAMASK
2016 Comprehensive Sewer Plan Chapter 9
9-7
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
9.3.2 Criticality
Criticality is determined based on the consequences of failure and the likelihood of the failure
occurring. Factors that impact criticality include the age of the asset, repair history of the asset, and
consequences, in terms of dollars, should a failure occur. Consequences of a system failure include
such considerations as whether a failure impacts a hospital or school as compared to a residence or
unoccupied property. Each asset is evaluated based on these likelihood and consequence factors
and a numerical weighting assigned. The combination of these factors results in the assignment of a
criticality value. Figure 9-2 depicts an example of assessing asset criticality values to a large
collection system. The data on the figure are not specific to the City’s sanitary sewer system.
Figure 9-2. Example of identifying asset criticality
The points shown above are sample data and do not represent a specific evaluation of Auburn's sanitary sewer system.
9.3.3 Defining Maintenance Strategies
As Figure 9-3 illustrates, an asset’s criticality can be used to determine the best maintenance
strategy for that asset. There are four general maintenance strategies based on the risk carried by
the asset and the specific maintenance strategy used should be assigned on an individual asset
basis to ensure that the appropriate actions are being taken.
Chapter 9 2016 Comprehensive Sewer Plan
9-8
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Figure 9-3. Maintenance strategies based on risk
High-risk assets are identified as having both a high likelihood of failure and a high consequence of
failure. These assets should be modified in order to mitigate this risk. Risk can be mitigated by
adding redundancy to reduce the consequence of failure or by selecting a more robust type of asset
that can perform the same function with a lower likelihood of failure. An example of this would be
adding a redundant pump to a pump station to reduce the consequence of any one pump failing, or
using a different type of pump to reduce the occurrence of clogs.
Moderate-risk assets have been separated into two regions: high-likelihood/low-consequence assets
and high-consequence/low-likelihood assets. The assets with a high likelihood of failure but a low
consequence of failure should receive time-based maintenance care. This maintenance strategy
includes preventive maintenance (PM) including inspection, calibration, oil changes, and tasks
recommended by the manufacturer or other best practices. Corrective maintenance should also be
conducted to address defects as they are revealed and the spare parts strategy should be prepared
for the high incidence of failures. The frequency of these maintenance activities is driven by the
economics of maintaining the asset; the cost of maintaining the asset should be in proportion with
the cost of replacing the asset in order to optimize the life-cycle cost of asset.
An example of a high-likelihood/low-consequence asset would be a ventilation fan in a pump station.
The consequence of the fan failing may be relatively low and, as a result, expensive maintenance
activities should not be performed on an inexpensive fan. Instead, performing routine PM to extend
the life of the fan should be done at a frequency that is cost-effective and the fan should be replaced
upon failure. Spare fans may be kept on hand or an on-call contract with a vendor may be used, if
appropriate.
The second region of moderate-risk assets are assets that have a high consequence of failure but
are not very likely to fail. These assets should receive condition-based maintenance care. This
maintenance strategy includes the same PM identified above but also includes predictive
maintenance (PdM), which includes technologies and practices designed to evaluate assets in
operation and, based on known failure modes, predict failures before they occur. PdM technologies
include vibration monitoring, infrared detection, oil analysis, and other condition evaluative tools.
2016 Comprehensive Sewer Plan Chapter 9
9-9
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Once these measures identify deteriorating condition, corrective maintenance activities should be
taken to prevent a failure and the spare parts strategy should reflect that the high consequence of
failure requires that these assets be non-functional for as short a period of time as possible. The
frequency of these maintenance activities should be based on the condition of the asset; as the
condition declines, more frequent maintenance efforts may be required.
An example of a high-consequence/low-likelihood asset would be a new sewer line serving the City’s
downtown area. The sewer may be relatively unlikely to fail, but the costs of a failure are such that
preventing a failure is worth the cost of PdM activities. Standard PM such as jet cleaning may still be
appropriate, but PdM activities such as monitoring the line via CCTV are appropriate to identify
failures before they occur. Once a failure has been identified, the spare parts strategy should be
such that the time for repair or replacement minimizes the loss of service to the City’s customers.
This may mean keeping spare supplies on hand or having an on-call contract with a contractor for
quick repairs.
The assets with the lowest risk should receive only minimal, routine PM and most maintenance
activities should be reactive. It may be expected to run these assets to failure as the consequences
of failure are low. Because of the low consequence and likelihood of failure, replacements for these
assets should be ordered rather than kept as spare parts in order to minimize costs. A sump pump in
a pump station may have a low likelihood of failing and a low consequence in case of failure.
Occasional routine maintenance may be conducted on sump pumps but in general, they are allowed
to run to failure. Once they have failed, it may be more cost-effective to purchase a new sump pump
“off the shelf” rather than rebuild the existing pump or carry spares.
Table 9-3 summarizes the criticality-based maintenance strategies.
Table 9-3. Criticality-Based Maintenance Strategy Summary
Asset criticality Maintenance strategy Frequency
basis
Spare parts
strategy
Risk
optimization
High Engineer-out: mitigate risk by minimizing the
likelihood and/or consequence of a failure
None None Unacceptable
risk
Moderate
(high-likelihood)
Time-based: routine PM sustains the asset’s
condition and extends its life
Economic Prepare for high
rate of failure
Minimize risk
Moderate
(high-
consequence)
Condition-based: routine PM is supplemented with
PdM to identify failures before they occur
Asset condition Minimize
downtime
No unexpected
failures
Low Reactive: only minimal routine maintenance is done
to sustain the asset’s condition
Economic or as
needed
No spares Run to failure
9.3.4 Condition Assessments
For the City’s roughly 5,500 pipe segments, PdM activities will require condition assessments of
pipes through CCTV inspections. As with the maintenance strategies, the priority and frequency of
CCTV inspections should be related to the relative criticality of the pipe being assessed. High-
criticality pipes (those that are in the top 20 percent of the criticality scoring) should get the first
priority in receiving inspections and subsequent inspections should be more frequent for these pipes
than for less critical pipes. Moderate-criticality pipes (pipes that are in the next 30 percent of
criticality scoring) should also receive inspections when available but should be on a less frequent
recurring schedule than highly critical pipes. Low-criticality pipes should receive inspections only if
the resources are available without hindering the inspection of high- and moderate-criticality pipes.
Chapter 9 2016 Comprehensive Sewer Plan
9-10
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
After condition assessments have been completed, the results should be reentered into the criticality
model to either update or confirm the criticality rating. Entering condition assessment data could
result in some pipes considered highly critical to be downgraded to moderately critical or could result
in some pipes thought to be only moderately critical to become more critical. For example, currently
there are two pipes crossing the Green River that should be included in the City’s next round of CCTV
inspections. If the results of the inspection show that the pipes are in excellent condition, the pipes
may be considered less critical and may not need to be reevaluated for a number of years. However,
if the inspection shows that the pipes are in poor condition, more frequent inspection may be
needed or including a replacement/lining of the pipes in the next CIP may be appropriate.
9.3.5 Continual Improvement
Once asset criticality and the optimal maintenance strategy have been identified, continual
reevaluation is important to ensure that the most appropriate strategy has been identified. This
process includes reevaluating the likelihood and consequence factors to ensure that they accurately
measure the risk an asset carries, recalculating each asset’s criticality to identify any changes since
the last evaluation, and reviewing each asset’s maintenance and spare parts strategy to make
certain that the appropriate level and frequency of activities are being performed. This continual
improvement guarantees that the minimal life-cycle cost is being achieved for each of the City’s
assets while still meeting the City’s desired LOS.
9.4 Discharge Quality Control
The characteristics of sewage discharged to the collection system can have negative impacts on
wastewater treatment and conveyance capability. Such discharges—which include rags, diapers,
harmful chemicals, pharmaceuticals, and FOG—should be minimized to the maximum extent
possible.
9.4.1 Control of Fats, Oils, and Greases
Engineering currently employs a 0.25 FTE water resources technician to implement and oversee the
City FOG Reduction Program. This program seeks to enforce the City’s code prohibiting the discharge
of FOG by restaurants and other FSEs by requiring the submittal of a FOG control plan as a
requirement to obtain a business license. The control plans must outline best management practices
that will be taken by the business, such as dry-wiping plates, installing and/or regularly cleaning a
grease trap or interceptor, and disposing of grease by recycling it or disposing of it with solid waste. It
is recommended (see Section 7.6) that the City continues the current FOG Reduction Program if not
expand it to include proactive inspections and public outreach activities.
9.4.2 Industrial Waste
As applications for discharge permits are reviewed by City staff, activities, mainly industrial, that are
likely to introduce chemicals or other materials to the sanitary sewer system, are identified.
Applicants are directed to coordinate with the King County Wastewater Treatment Division’s
Industrial Waste Program for the required level of discharge authorization for that activity.
9.4.3 Public Education
The City should continue to educate the general public about what is appropriate to put in the sewer
system. Continued use of bill stuffers, posters, general announcements, and other actions to inform
the public about the harmful effects that some discharges have to the system is recommended.
2016 Comprehensive Sewer Plan Chapter 9
9-11
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
9.5 Hazard Planning
Auburn is situated in a geographic area where natural hazards exist. Specifically, the city’s proximity
to the Green and White rivers presents the potential for flooding and nearby Mt. Rainier looms as a
volcanic and lahar hazard. In addition, the numerous faults present in the Puget Sound lowlands
increase the likelihood of an earthquake. The Utility should understand the vulnerability of facilities
to such natural hazards to be prepared for responding if such an event should occur. The City has
prepared a Public Works Emergency Response Manual (see Section 7.4.2) to serve as a guide on
how to handle emergency situations.
An evaluation of sewer facilities for hazard planning purposes should be completed. The evaluation
should identify the potential hazards for Auburn and assess the vulnerability of sewer facilities to the
hazards. As a result of the evaluation, a plan outlining the hazards, facilities vulnerable to hazards,
and activities for mitigating the risk associated with the hazards should be developed.
9.6 Maintenance Issues
Maintenance crews have expressed several areas of concern that did not rise to the level of a CIP
project based on currently available information. However, they merit additional investigations or
research to improve LOS.
9.6.1 105th Place SE and Lea Hill Road SE
The sewer running west down Lea Hill Road SE is very steep and then encounters the 8th Street
siphon at the bottom of the hill. There have been odor issues/complaints at this site and it is
possible that entrapped air is reducing the capacity of the pipe.
9.6.2 Sewers Crossing Freeway
Three City-owned sewers cross underneath State Route 167 with both sides of the sewers located
within wetlands. There is very limited access to these sewers and they have never been inspected.
9.6.3 Sewers within Easements
Sewers that are located within easements, especially ones located in backyards of houses, are
difficult to access. Either the sewers are physically constrained by fences or overgrown vegetation
limits required access to the sewers for proper maintenance.
9.7 SEPA Compliance
The Washington State Environmental Policy Act (SEPA) environmental checklist was completed by
the City as part of this Plan update. A letter documenting the “Determination of Non-Significance” is
located in Appendix D.
9.8 Schedule
Figure 9-4 outlines the general schedule for CIP and monitoring over the next 6 years. Projects
marked as potential activities are tasks that may be needed to address changing conditions or
updated modeling. In cases of funding or resource scarcity, activities should be performed in the
order of their impact on addressing the gap between the City’s expected LOS and the actual LOS
being provided.
Chapter 9 2016 Comprehensive Sewer Plan
9-12
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Project
number Project name 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035
6-Year CIP 7–20-Year CIP
1 Sanitary Sewer Repair & Replacement/System Improvements
2 Street Utility Improvements
3 Vactor Decant Study
4 Sewer Pump Station Replacement/Improvement
5 Siphon Assessment
6 Pump Station Condition Assessment
7 MH Ring and Cover Replacement
8 Cleaning and Inspection of Large-Diameter Pipe
9 Inflow and Infiltration Study
10 Plan Update
Figure 9-4. City of Auburn Sewer Plan implementation timeline
10-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Chapter 10
Limitations
This document was prepared solely for the City of Auburn in accordance with professional standards
at the time the services were performed and in accordance with the contract between the City of
Auburn and Brown and Caldwell dated December 6, 2013. This document is governed by the specific
scope of work authorized by the City of Auburn it is not intended to be relied upon by any other party
except for regulatory authorities contemplated by the scope of work. We have relied on information
or instructions provided by the City of Auburn and other parties and, unless otherwise expressly
indicated, have made no independent investigation as to the validity, completeness, or accuracy of
such information.
Chapter 11
References
Auburn City Code (ACC). 2014. http://www.codepublishing.com/wa/auburn/.
City of Auburn Comprehensive Plan (Comp Plan). Amended 2008. City of Auburn.
http://www.auburnwa.gov/doing_business/community_development/planning/comprehensive_plan.htm
King County, 2002. 2001/2002 Wet Weather Flow Monitoring; Regional Infiltration/ Inflow (I/I) Control Program.
King county Department of Natural Resources and Parks, Wastewater Division. June 2002.
Brown and Caldwell, December 2009. City of Auburn Comprehensive Sewer Plan. Prepared for the City of Auburn by
Brown and Caldwell.
2016 Comprehensive Sewer Plan
A-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Inter-local Agreements and Outside Appendix A:
Agency Correspondence
A1. King County
• Sewage Disposal Service with Metro (Ordinance 2774, and Resolutions 1727 and 2090)
• Franchise Agreement No. 14458
A2. Soos Creek Water and Sewer District
• Service Area Boundaries (Resolution 3321)
A3. City of Kent
• Sewer Service Boundaries (Resolution 3322)
A4. City of Pacific
• Sewer Service Boundaries (Resolutions 4335 and 730)
A5. Muckleshoot Indian Tribe
• Sewer Service Boundaries (Resolution 4902)
• Wastewater Conveyance Cost Sharing (Resolution 3660)
• Temporary Sewage Lift Station Operation (Resolution 3502)
A6. Lakehaven Utility District
• Sewer Service Boundaries (Resolutions 3651, 3824, and 2005-1038)
A7. City of Algona
• Sewer Service Boundaries (Resolution 3589)
A8. City of Bonney Lake
• Sewer Service Boundaries (Resolutions 3760 and 3796)
• Right of Way Use Permits (Resolutions 3873 and 1471)
2016 Comprehensive Sewer Plan
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Appendix A1: Inter-local Agreements and Outside
Agency Correspondence
King County
• Sewage Disposal Service with Metro (Ordinance 2774, and Resolutions
1727 and 2090)
• Franchise Agreement No. 14458
2016 Comprehensive Sewer Plan
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Appendix A2: Inter-local Agreements and Outside
Agency Correspondence
Soos Creek Water and Sewer District
• Service Area Boundaries (Resolution 3321)
2016 Comprehensive Sewer Plan
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Appendix A3: Inter-local Agreements and Outside
Agency Correspondence
City of Kent
• Sewer Service Boundaries (Resolution 3322)
2016 Comprehensive Sewer Plan
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Appendix A4: Inter-local Agreements and Outside
Agency Correspondence
City of Pacific
• Sewer Service Boundaries (Resolutions 4335 and 730)
2016 Comprehensive Sewer Plan
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Appendix A5: Inter-local Agreements and Outside
Agency Correspondence
Muckleshoot Indian Tribe
• Sewer Service Boundaries (Resolution 4902)
• Wastewater Conveyance Cost Sharing (Resolution 3660)
• Temporary Sewage Lift Station Operation (Resolution 3502)
2016 Comprehensive Sewer Plan
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Appendix A6: Inter-local Agreements and Outside
Agency Correspondence
Lakehaven Utility District
• Sewer Service Boundaries (Resolutions 3651, 3824, and 2005-1038)
2016 Comprehensive Sewer Plan
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Appendix A7: Inter-local Agreements and Outside
Agency Correspondence
City of Algona
• Sewer Service Boundaries (Resolution 3589)
2016 Comprehensive Sewer Plan
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Appendix A8: Inter-local Agreements and Outside
Agency Correspondence
City of Bonney Lake
• Sewer Service Boundaries (Resolutions 3760 and 3796)
• Right of Way Use Permits (Resolutions 3873 and 1471)
2016 Comprehensive Sewer Plan
B-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Hydraulic Capacity Analysis Appendix B:
Technical Memorandum
Limitations:
This document was prepared solely for the City of Auburn in accordance with professional standards at the time the services were performed and in
accordance with the contract between the City of Auburn and Brown and Caldwell dated December 6, 2013. This document is governed by the
specific scope of work authorized by the City of Auburn; it is not intended to be relied upon by any other party except for regulatory authorities
contemplated by the scope of work. We have relied on information or instructions provided by the City of Auburn and other parties and, unless
otherwise expressly indicated, have made no independent investigation as to the validity, completeness, or accuracy of such information.
701 Pike Street Suite 1200
Seattle, WA 98101
T: 206.621.0100
F: 206.749.2200
Prepared for: City of Auburn
Project Title: Sanitary Sewer Comprehensive Plan
Project No.: 145308
Technical Memorandum
Subject: Sanitary Sewer Model Development
Date: March 9, 2015
To: Robert Elwell, P.E.
From: Justin Twenter, P.E.
Sanitary Sewer Model Development
ii
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Table of Contents
List of Figures ........................................................................................................................................................... iii
List of Tables ............................................................................................................................................................. iv
List of Abbreviations ................................................................................................................................................. iv
Section 1: Introduction ............................................................................................................................................. 1
Section 2: Modeling Scenarios ................................................................................................................................ 1
Section 3: Flow Monitoring Data ............................................................................................................................. 1
Section 4: Climatic Data ........................................................................................................................................... 4
4.1 Rainfall....................................................................................................................................................... 4
4.2 Evapotranspiration.................................................................................................................................... 5
Section 5: Hydraulic Model Development ............................................................................................................... 5
5.1 Software Platform ..................................................................................................................................... 5
5.2 Model Extent ............................................................................................................................................. 6
5.3 Infrastructure Data ................................................................................................................................... 8
5.3.1 Geographic Information System ................................................................................................. 8
5.3.2 Pump Station ............................................................................................................................... 9
5.3.3 Stuck River Trunk ...................................................................................................................... 12
5.4 Boundary Conditions .............................................................................................................................. 13
Section 6: Hydrologic Model Development ........................................................................................................... 13
6.1 Calibration Period Dry Weather Flow ..................................................................................................... 13
6.2 Development of Subcatchments ........................................................................................................... 16
6.3 Calibration Period Wet Weather Flow .................................................................................................... 18
Section 7: Long-Term Simulations......................................................................................................................... 21
Section 8: Future Conditions ................................................................................................................................. 23
8.1 Future Dry Weather Flow ........................................................................................................................ 23
8.1.1 Dry Weather Flow from Population Expansion ........................................................................ 23
8.1.2 Dry Weather Flow from Sewer Extension ................................................................................. 26
8.2 Future Wet Weather Flow ....................................................................................................................... 28
8.3 Future Hydraulic Improvements............................................................................................................. 29
8.4 Future-Conditions Summary ................................................................................................................... 32
Section 9: Model Results ....................................................................................................................................... 32
9.1 Baseline Conditions ................................................................................................................................ 32
9.2 2020 Conditions ..................................................................................................................................... 35
9.3 2034 Conditions ..................................................................................................................................... 37
Section 10: Conclusions ........................................................................................................................................ 40
References .............................................................................................................................................................. 41
Sanitary Sewer Model Development
iii
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Attachment A: Modifications to Collection System GIS ....................................................................................... A-1
Attachment B: Pump Station Data ....................................................................................................................... B-1
List of Figures
Figure 3-1. Auburn area flow monitors.................................................................................................................... 3
Figure 5-1. Auburn MIKE URBAN model extent ...................................................................................................... 7
Figure 5-2. Example pipe profile with interpolated manhole invert elevation ...................................................... 9
Figure 5-3. Ellingson PS comparison..................................................................................................................... 11
Figure 5-4. Location and flow path of SRT ............................................................................................................ 12
Figure 6-1. AUBRN53 monitor flow data and observed rainfall .......................................................................... 14
Figure 6-2. AUBRN53 monitor DWF calculation ................................................................................................... 15
Figure 6-3. Dry weather flow schematic ................................................................................................................ 16
Figure 6-4. Upstream area of influence example ................................................................................................. 17
Figure 6-5. MIKE URBAN RDI engine schematic .................................................................................................. 19
Figure 6-6. AUBRN53 wet weather calibration ..................................................................................................... 21
Figure 7-1. Citywide peak RDII Cunnane plot ....................................................................................................... 22
Figure 8-1. TAZ polygons within the vicinity of Auburn ......................................................................................... 24
Figure 8-2. Proposed sewer extensions and development percentages ............................................................ 27
Figure 8-3. High and low volume time series comparison example.................................................................... 29
Figure 8-4. Pacific PS re-route ............................................................................................................................... 31
Figure 9-1. Baseline-conditions minimum freeboard ........................................................................................... 33
Figure 9-2. Low-freeboard short manhole ............................................................................................................ 34
Figure 9-3. Flooding along Boundary Boulevard SW ............................................................................................ 34
Figure 9-4. 2020 conditions minimum freeboard ................................................................................................ 36
Figure 9-5. 2020 surcharge of the KC-owned Auburn West Interceptor ............................................................ 37
Figure 9-6. 2034 conditions minimum freeboard ................................................................................................ 38
Figure 9-7. Surcharged line upstream of Verdana PS .......................................................................................... 39
Figure 9-8. Hydraulic profile of KC-owned Auburn West Interceptor at Perimeter Road ................................... 39
Sanitary Sewer Model Development
iv
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
List of Tables
Table 3-1. King County Flow Monitors..................................................................................................................... 4
Table 4-1. Long Term Rainfall Sources and Dates ................................................................................................. 5
Table 5-1. Auburn Area Pump Station Capacities ................................................................................................ 10
Table 5-2. Auburn Area Pump Station Upgrades .................................................................................................. 11
Table 6-1. MIKE URBAN Hydrologic Model Calibration Parameters .................................................................... 19
Table 7-1. Peak RDII Cunnane Estimated Flow Frequency ................................................................................ 22
Table 7-2. Peak RDII per Monitoring Basin ........................................................................................................... 23
Table 8-1. Future Population Estimates by TAZ Polygon ...................................................................................... 25
Table 8-2. Analysis Period Model Modifications ................................................................................................... 32
List of Abbreviations
BC Brown and Caldwell
CIP capital improvement project
City City of Auburn
DHI Danish Hydraulic Institute
DWF dry weather flow
ET evapotranspiration
ft3 cubic foot/feet
GIS Geographic Information System
gpcd gallons per capita per day
HGL hydraulic grade line
H&H hydrologic and hydraulic
ID identification
KC King County
LOS level of service
mgd million gallon(s) per day
MH manhole
PS pump station
RDII rainfall-derived inflow and infiltration
SR State Route
SRT Stuck River Trunk
SSA sewer service area
TAZ Traffic Analysis Zone
WWHM Western Washington Hydrology Model
Sanitary Sewer Model Development
1
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Section 1: Introduction
As part of the 6-year comprehensive planning effort, Brown and Caldwell (BC) developed a hydrologic and
hydraulic (H&H) model of the City of Auburn’s (City) sewer collection system. The objective of the modeling
effort was to characterize the magnitude and volume of rainfall-derived inflow and infiltration (RDII) entering
the sewer system during wet weather events and to evaluate whether that RDII causes surcharge beyond the
established level of service (LOS) and/or surface flooding during a 20-year storm in baseline (year 2014)
conditions as well as future conditions in year 2020 (6-year scenario) and year 2034 (20-year scenario)
conditions. This document describes the analysis periods covered in this effort, driving data used to build the
model, calibration of the model, and hydraulic results from the 20-year storm simulations. In general, the
City’s sewer system infrastructure performs well in a 20-year storm. The modeling analysis indicated that no
capital improvement projects (CIPs) are required to address hydraulic capacity restrictions in City-owned
pipes in the existing or future 6-year conditions. The future 20-year condition indicates an area of hydraulic
restriction upstream of the Verdana Pump Station (PS); however, CIPs are not planned from 20-year condi-
tion simulation results.
Section 2: Modeling Scenarios
Four scenarios were analyzed for this modeling effort. For each case, the model was modified to represent
H&H conditions at a particular point in time. Each of the modeling scenarios are described below:
• Calibration period: Flow data used to calibrate the model were collected between September 2009 and
May 2011. In order to calibrate the model’s hydrology appropriately, the modeled collection system flow
paths needed to be representative of that time period. Trunk line and pump station upgrades made be-
tween the calibration period and current conditions were left out of the model for model calibration.
• Baseline conditions: The major change between the calibration period and baseline 2014 conditions
came from the construction of the Stuck River Trunk (SRT) and four pump station modifications. The SRT
diverts flow east from the intersection of K Street SE and 17th Street SE to the Auburn West Interceptor
along C Street SW (see additional description in Section 5.3.3. Before 2014, the Valley Meadows and
White Mountain pump stations were decommissioned, the Verdnana pump station was constructed, and
the Ellingson and Dogwood pump stations were upgraded. All of these changes were reflected in the
model to represent baseline conditions.
• 6-year planning horizon: Wastewater planners plan 6 years out, so, based on 2014 data, population
growth and RDII increases in the system are projected for 2020. Plans to re-route the discharges from
King County’s (KC’s) Pacific PS are also included in this simulation because it is expected to be re-routed
in the near future.
• 20-year planning horizon: Wastewater planners also plan 20 years out, so, based on 2014 data,
population growth and RDII increases in the system are projected for 2034. The 20-year planning hori-
zon looks for long term changes in the sewer system and the results are used to indicate areas to ob-
serve, rather than inform immediate capital improvement projects.
Section 3: Flow Monitoring Data
The KC Flow Monitoring program deployed between 80 and 120 flow monitors throughout the KC convey-
ance system to measure sanitary sewer flows for system management and capital facilities planning.
Fourteen of those monitors measure flows from KC mainlines that service areas within the city of Auburn.
Sanitary Sewer Model Development
2
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
The data from those monitors are used in this study to characterize dry weather flow (DWF) patterns and to
perform model calibration. The flow monitoring locations are described in Table 3-1. Figure 3-1 presents a
map of the city of Auburn with the flow monitors located and their tributary upstream basins delineated.
These basins are called “monitoring basins.”
Sanitary Sewer Model Development
3
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 3-1. Auburn area flow monitors
Sanitary Sewer Model Development
4
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Table 3-1 provides a location description for each of the flow monitors used in this study and the date
ranges of the monitors’ available data. In general, each flow monitor provided two wet seasons of data.
Table 3-1. King County Flow Monitors
Monitor ID Location Date range
ABN008 20th St. NW at West Valley Hwy. 7/29/2009–5/23/2011
ABN022 37th St. NW east of 1st St. NW 7/30/2009–5/23/2011
ABN023 30th St. NW west of C St. NE 9/1/2009–5/17/2011
ABN027 29th St. NW at Interurban Trail 8/10/2009–5/22/2011
ABN032 Between Clay St. NW and H St. NW south of 6th St. NW 7/28/2009–5/16/2011
AUBRN53 44th St. NW east of I St. NW 9/1/2009–5/16/2011
AUBWV016 Boundary Blvd. SW at O Street SW 9/1/2009–5/18/2011
LAKELANDHILLS_WW Lakeland Hills PS northwest of Oravetz Rd. SE 3/4/2010–7/25/2011
LKH001A 37th St. NW west of 1st St. NW 9/17/2009–5/16/2011
MSTTR02A 23rd Street NE at E Street NE 8/6/2009–5/23/2011
MSTTR22A Henry Rd. NE north of 6th St. NE 8/3/2009–5/16/2011
MSTTR48 K St. SE north of 17th St. SE 9/1/2009–5/18/2011
WINT003 B St. NW north of 16th St. NW 9/1/2009–5/18/2011
WINT038 Interurban Trail north of 15th St. SW 9/28/2009–5/23/2011
Because the model’s hydrologic parameter sets are defined by monitoring basin, the boundaries in Figure
3-1 also define the extent of each of the calibration models. In other words, the portions of the model
defined by the monitoring basin boundaries were calibrated independently of each other as calibration
basins. This is described in further detail in Section 6.3.
Section 4: Climatic Data
Rainfall and evapotranspiration (ET) time series data are required to simulate RDII processes within the
hydrologic model. The following sections describe the development of these data for use in hydrologic model
calibration and long-term model simulations.
4.1 Rainfall
BC developed a rainfall time series with 15-minute time increments based on data from several rain gauges.
Rainfall measurements recorded at the City’s rain gauge located at Auburn City Hall were used for the model
calibration period (August 2009 through May 2011) because the City Hall gauge is located closest in proxim-
ity to the flow monitoring basins.
For the times when the City Hall gauge was uninstalled or malfunctioning, the data gaps were filled with
rainfall collected at the Lakeland Hills PS, which is operated by KC and made available for free at the King
County Hydrologic Information Center (King County, 2014). A comparison of rainfall totals for the Auburn City
Hall gauge and the Lakeland Hills gauge over the period January 1, 2010, through April 30, 2011 (where
data exist for both gauges) indicated that the Lakeland Hills gauge recorded 8.6 percent more rainfall than
Sanitary Sewer Model Development
5
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
the City Hall gauge, which is considered acceptable based on best practices and engineering judgment for
comprehensive planning analysis.
Local rainfall data were appended with 61 years of rainfall from Sea-Tac International Airport to create a
long-term rainfall record that can be used to analyze wet weather frequency. The Sea-Tac data were extract-
ed from the Western Washington Hydrology Model (WWHM 2012). Data priority in the record was given to
the nearest gauges, with gauges farther outside of Auburn used only when necessary to complete the long-
term record. Table 4-1 lists the rainfall data sources, date ranges used to compile the long-term record, and
notes associated with the use of the data.
Table 4-1. Long Term Rainfall Sources and Dates
Gauge location Data source Start date End date Notes
Sea-Tac Airport WWHM 2012 10/1/1948 12/31/2009 15-minute rainfall, used only in long-term simulations
Auburn City Hall City of Auburn 1/1/2010 12/31/2010 15-minute local rainfall
Auburn City Hall City of Auburn 1/1/2011 5/1/2011 5-minute rainfall aggregated to 15-minute time step
Lakeland Hills PS King County Hydrologic
Information Center
5/2/2011 5/31/2011 15-minute rainfall to fill the gap in the Auburn record with
KC rainfall data
Auburn City Hall City of Auburn 6/1/2011 11/13/2012 15-minute local rainfall
Lakeland Hills PS King County Hydrologic
Information Center
11/14/2012 12/5/2012 15-minute rainfall to fill the gap in the Auburn record with
KC rainfall data
4.2 Evapotranspiration
ET data are required to estimate evaporation and transpiration losses from the land surface. The Washing-
ton State University Puyallup, Washington, extension operates the AgWeatherNet website, which is a reposi-
tory for numerous climatological data sets throughout Washington State, including grass reference ET
calculated for Puyallup. Grass reference ET from AgWeatherNet was acquired for the same time period as
the long-term rainfall record (WSU, 2014). Given that the cities of Puyallup and Auburn are situated at
roughly the same elevation in the eastern Puget Sound region, their daily ET values are likely similar; there-
fore, the Puyallup Reference ET data set was considered applicable to the city of Auburn.
Section 5: Hydraulic Model Development
The following sections describe the software platform chosen for this modeling effort, the hydraulic model
extent, as well as the infrastructure data used to create the model.
5.1 Software Platform
Auburn’s sanitary sewer collection system discharges to KC mainlines at various locations throughout the
city. KC has performed sanitary sewer modeling at a coarse spatial resolution in the Auburn area using MIKE
URBAN 1 software, which is the County’s preferred modeling platform. Therefore, the City has chosen to use
1 MIKE URBAN is a software package developed and sold by the Danish Hydraulic Institute (DHI). More information can be found at
http://www.mikepoweredbydhi.com/products/mike-urban.
Sanitary Sewer Model Development
6
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
MIKE URBAN to be consistent with the County’s modeling approach. The latest version of MIKE URBAN
(version 2014) was used.
KC uses the MIKE URBAN Runoff Model A for surface flows and the RDI model for groundwater infiltration to
estimate RDII. KC also uses the MOUSE hydraulic engine within MIKE URBAN to solve the hydraulic flow
routing equations. The MOUSE engine uses the full Saint Venant equations to solve for water levels and
velocities in piped systems. The Saint Venant equations provide more accurate hydraulic solutions in
complicated hydraulic environments that include changing flow rates, pipe surcharging, and back water
effects than simpler calculations such as the Kinematic Wave, which cannot solve flow rates in backwater
conditions. For consistency with KC, Runoff Model A and the RDI model were used in conjunction with the
MOUSE hydraulic engine in this modeling effort.
5.2 Model Extent
The hydraulic extent of the MIKE URBAN model was chosen to be consistent with previous comprehensive
planning modeling efforts. The same pipes, manholes (MHs), and pump stations included in the 2008
Comprehensive Plan (Brown and Caldwell, 2009) model were included in the current model. System modifi-
cations since then (new pump stations, conduits, and force mains) were reflected in the current model as
well.
In general, all pipes 10 inches in diameter and larger within the sanitary sewer service area (SSA) were
included in the model; smaller pipes were included only where needed to connect larger pipes to the main
network and force mains. Pipes smaller than 10 inches in diameter are less likely to be under capacity
because they are located predominantly in neighborhoods at the headwaters of the collection system and
they convey small flows to the mainline system. Ignoring these pipes greatly improves model run times
because of the reduced number of pipes requiring hydraulic calculations. Figure 3-1 provides a map of
Auburn’s collection system, the pipes included in the MIKE URBAN model, and the boundary of the SSA.
Sanitary Sewer Model Development
7
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 5-1. Auburn MIKE URBAN model extent
Sanitary Sewer Model Development
8
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
5.3 Infrastructure Data
Three sources of data were used to develop inputs for the collection and conveyance system: (1) the City’s
sewer utility geodatabase, (2) requested data from the City, and (3) the previous Comprehensive Plan model.
The following sections describe the data hierarchy and assumptions made in hydraulic model development.
5.3.1 Geographic Information System
The City’s Geographic Information System (GIS) Department provided BC with a 2014 sewer utility geodata-
base titled “Sewer.gdb.” The geodatabase contains geospatial locations and attribute data for sanitary sewer
structures such as mainlines, manholes, pump stations, and other appurtenances. The geodatabase was
used as the primary data source for constructing the collection and conveyance system model.
Pipe attributes such as diameter, inlet and outlet elevations, and length, as well as manhole attributes of
invert and rim elevation, are all necessary to build out the hydraulic network. Some gaps existed in the
geodatabase that required an assumption to fill. The following describes the hierarchy of assumptions used
to assign missing data:
• Manholes:
− Invert elevation: If missing or suspect, the inlet invert elevation from the outgoing pipe was used, if
available, as it should be the lowest connecting element to the manhole. Otherwise, invert elevation
of the same node in the 2008 Comprehensive Plan model was used. If the data are not available
from those two sources, straight-line interpolation between the upstream and downstream manhole
invert elevations was used.
− Rim elevation: If missing or suspect, rim elevation of the same node in the 2008 Comprehensive
Plan model was used, if available. Otherwise, the rim elevation was estimated from land surface el-
evation contour data.
− Manhole ID: The “Structure” field was used to uniquely identify each manhole. If missing in the GIS,
the identification number from the 2008 Comprehensive Plan model ID was used.
• Conduits:
− Inlet and outlet elevations: If missing or suspect, the invert elevation from the connecting manhole
was used. Otherwise, the 2008 Comprehensive Plan model value was used. If both of those were
unavailable, straight-line interpolation between the nearest known upstream and downstream ele-
vations was used.
− Diameter: If missing or suspect, the 2008 Comprehensive Plan model value was used. Otherwise, it
was estimated based on the diameters of the adjacent pipes.
− Conduit ID: Identification numbers were verified for all conduits. If an ID was missing, the 2008
Comprehensive Plan model ID was used
Once the gaps in the data fields were filled, the database was imported to the MIKE URBAN model such that
hydraulic profiles could be plotted to inspect for erroneous data through visual inspection. Hydraulic profiles
plots were drawn for the entire modeled collection system and used to find incorrect diameters or invert
elevations by checking for severe and/or adverse slopes. Adjustments were made to correct elevations using
data from the 2008 Comprehensive Plan model where available. Otherwise, straight-line interpolation was
used for elevation data replacement (see example in Figure 5-2). No diameters appeared to require adjust-
ment in this process. In total, 110 manhole invert elevations were adjusted to remove GIS elevation errors
from the hydraulic model. These adjustments are documented in Attachment A.
Sanitary Sewer Model Development
9
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 5-2 below shows a profile of a pipe section requiring elevation adjustment. The manhole in the middle
of the profile likely has an incorrect invert listed in the GIS as a small gravity pipe is unlikely to be so dramat-
ically inclined. Consequently, the manhole was assigned a new invert by interpolating between the two
manholes on either side. The connecting conduits were adjusted to have no inlet or outlet offset from the
adjusted manhole. Figure 5-2 provides the adjusted profile. This adjustment reduces the risk of simulating
system backups that are likely based on unconfirmed GIS data.
Figure 5-2. Example pipe profile with interpolated manhole invert elevation
5.3.2 Pump Station
BC asked the City for updated wet well volume and pump capacity information for the pump stations within
the study area. On March 14, 2014, the City provided an Excel table summary of the requested pump station
information, which is included in Attachment B.
Each pump station is composed of a lead pump and a lag pump. The single pump capacity was provided by
the Cityfor each, but a total combined pump capacity was not given for when both pumps are running. To
account for the reduction in capacity due to higher downstream head conditions from both pumps running,
but without empirical data to inform a reduction factor on the second pump’s capacity, a general assumption
of 50 percent of single pump capacity was assumed for the lag pump. Table 5-1 below provides the pump
station capacity information used in the hydraulic model.
Likely incorrect MH
invert elevation
Adjusted invert
elevation
Sanitary Sewer Model Development
10
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Table 5-1. Auburn Area Pump Station Capacities
Pump station Location Number of
pumps
Single pump capacity
(mgd)
Multiple pump capacity
(mgd)
22nd Street 22nd St. SE & Riverview Dr. 2 0.792 1.188
8th Street J St. NE & 8th St. NE 2 0.216 0.324
Area 19 Lake Tapps Pkwy. E & west of 72nd St. SE 2 0.468 0.702
D Street D St. NE & Auburn Way N. 2 0.576 0.864
Dogwood Dogwood St. SE 1500 & 15th St. SE 2 0.432 0.648
Ellingson Road 41st St. SE, east of A St. SE 2 2.199 3.298
F Street F St. SE & 17th St. SE 2 0.576 0.864
Lakeland Hills Oravetz Rd. SE north of Mill Pond Dr. SE 1* 1.732 N/A
North Tapps Lake Tapps Pkwy. E & west of 176th Ave. E. 2 0.734 1.102
Peasley Ridge S. 320th St. & 53rd Ave. S. 2 0.396 0.594
R Street R St. NE & 6th St. NE 2 0.144 0.216
Rainer Ridge 125th Pl. SE & south of SE 318th Way 2 0.288 0.432
Riverside 8th St. NE & 104th Ave. SE 2 0.576 0.864
Terrace View E Valley Hwy. E & north of Terrace View Dr. SE 2 0.972 1.458
Valley Meadows 4th St. SE & V St. SE 2 0.180 0.270
Verdana 118th Ave. SE & SE 296th Pl. 3** 2.520 3.780
* Lakeland Hills PS pump data not provided by the City as it is KC-owned. Single pump and parameters used from 2008 Comprehensive Plan
model as no new data were available.
**Third Verdana pump is an emergency pump and is not included in the hydraulic model.
The City was unable to provide updated data about the Lakeland Hills PS because it is owned and operated
by KC. Therefore, the 2008 Comprehensive Plan model values for the pump station were reused in this
modeling effort. The data available then were limited to one pump at 1.732 million gallons per day (mgd)
capacity, although the pump station has two discharge force mains and multiple pumps. Only one force main
is included in the model as only one pump capacity is known.
Since the previous Comprehensive Plan update, three pump stations were upgraded, a new pump station
was built, and two pump stations were decommissioned. The Dogwood and Ellingson PSs were upgraded
and are included in the model. The Auburn 40 PS, although upgraded, is not explicitly modeled. Rather, its
flow contribution and signature is accounted for within the model’s hydrologic calibration. Because the
hydraulic network is not extended up to the pump station, flow peaks are created within the hydrologic
model rather than using a pump station to augment the flow signature. The Verdana PS was constructed to
lift water that used to flow to the Valley Meadows and White Mountain PSs, both of which were decommis-
sioned. Table 5-2 below provides a summary of the modeled pump station upgrades since the previous
Comprehensive Plan. Following the table are discussions of how these changes were accounted for within
the model.
Sanitary Sewer Model Development
11
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Table 5-2. Auburn Area Pump Station Upgrades
Pump station Monitoring basin Previous capacity (mgd) New capacity (mgd) Previous wetwell
volume (ft3)
New wetwell
volume (ft3)
Dogwood MSTTR48 0.58 0.65 930 925
Ellingson WINT038 2.9 3.30 500 1,086
Verdana MSTTR02A
Valley Meadows = 0.36
3.78
Valley Meadows = 588
5,395 White Mountain = 0.36 White Mountain 333
Total = 0.72 Total = 921
The Dogwood PS was upgraded to a slightly higher pumping capacity after the monitoring period. The change
in peak discharge attributable to the pump station was assessed by examining the modeled flow at the
nearest downstream flow monitoring location (MSTTR48) given the two pump station capacities. Visual
inspection of the flow hydrograph at the monitor location indicated that the change in pumping capacity
made no appreciable difference in flow rates. Therefore, the new pump capacity was used during model
calibration.
The Ellingson PS, across the river from the Lakeland Hills PS, was also upgraded after the flow monitoring
period. Therefore, the old pump station parameters were used for calibration and adjusted parameters were
used to model baseline conditions. Both the Lakeland Hills and Ellingson PSs discharge to manhole 1208-
38 because they share a force main. The nearest flow monitor downstream is the WINT038 flow monitor,
which accepts flow from both pump stations. Figure 5-3 presents a comparison of discharges from the
Ellingson PS using previous and adjusted parameters. The use of a new constant-speed pump (orange)
produces flow spikes unlike the discharges from the previous variable-speed pump (blue). However, down at
the flow monitoring location, the pump station flows appear to attenuate and, consequently, the change in
flows at the monitor location are negligible (red = new pump parameters, green = old pump parameters).
The change in peak flow at the flow monitoring location for the December 2010 storm (largest storm in the
monitoring period) is nearly 5 percent, suggesting that the changes at the Ellingson PS did not greatly affect
the flow signature at the flow monitor.
Figure 5-3. Ellingson PS comparison
Orange: new constant-speed pump discharge; blue: old variable speed pump discharge;
green: modeled flows at monitor with new pump; red: modeled flows at monitor with old pump
Sanitary Sewer Model Development
12
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
The Verdana PS replaced the Valley Meadows and White Mountain PSs for conveying wastewater from the
northeast portion of the city to the KC interceptor lines. The new Verdana PS has more capacity and wetwell
volume than the two older pump stations combined. Gravity pipe infrastructure in the area was modified to
bring wastewater flows to the Verdana PS; these modifications are reflected in the hydraulic model. Because
the subcatchment areas are a function of the pipe lengths within the system, a reworking of the model’s
hydrology would have been required to run the model in the different pumping conditions. Verdana PS is far
enough upstream from the next downstream flow monitor (MSTTR02A) that much of its flow signature can
attenuate before being observed. Furthermore, the Verdana PS’s discharges are a small proportion of the
total flow at the monitor because the MSTTR02A monitor also observes the MSTTR22A and MSTTR48
monitoring basins upstream. Consequently, reworking the model to run the decommissioned Valley Mead-
ows and White Mountain PSs for the sake of calibration was not pursued as the hydraulic modifications do
not make enough of a change in the flow signature at the monitor to warrant model reconstruction.
5.3.3 Stuck River Trunk
The SRT is approximately 4,000 feet long, with a diameter of 27 inches. Its purpose is to route flows from a
capacity-limited sewer line in southeast Auburn across to the Auburn West Interceptor, which has capacity to
convey additional flows. The SRT was constructed in 2013, which was after the monitoring period. Therefore,
the calibration model did not include the SRT. The SRT was built into the hydraulic model for baseline and
future conditions using design plan sets provided by KC. As-built drawings were not available; however,
Robert Elwell (Elwell, 2014) indicated in an e-mail that constructed conditions did not deviate much from the
original drawing set. Figure 5-4 below indicates the location of the SRT and the new flow path it provides.
Figure 5-4. Location and flow path of SRT
Sanitary Sewer Model Development
13
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
5.4 Boundary Conditions
Boundary conditions at model outfalls can affect the hydraulic performance of a collection system. For a
collection system that discharges to a water body, such as a river, or a treatment plant the elevation of the
river’s water surface can cause backwater in the collection system if the river elevation is high. Knowledge of
the boundary condition is necessary to accurately replicate this phenomenon.
In the case of Auburn’s collection system, a normal depth downstream boundary condition was used, which
assumes that the hydraulic grade line (HGL) in the most downstream link is set by the normal flow depth
rather than a special hydraulic circumstance such as a regulated interceptor where the level is set by
manual or automated controls (thus creating an HGL level that does not correlate with flow rate). In the case
of the Auburn system, the outlet sewer line was modeled beyond the AUBRN53 flow monitor, which is the
most downstream flow monitor, representing the boundary of the calibrated study area. Because the
interceptor line within which the AUBRN53 flow monitor is located is not regulated with controls, normal flow
calculations are adequate in ensuring that the HGL within the model is representative of field conditions. A
normal depth boundary condition also provides a representative downstream hydraulic condition during
long-term simulations where observed depths in the downstream system are not available.
Section 6: Hydrologic Model Development
This section describes the development of the hydrologic model, which produces the two components of
sewer flow:
• DWF, which is composed of wastewater from residential, commercial, and industrial water usage and is
relatively unaffected by climatic conditions
• RDII, which consists of groundwater (infiltration) seeps into sewer pipes through holes, cracks, joint
failures, and faulty connections, as well as runoff (inflow) from roof drain downspouts, foundation drains,
storm drain cross-connections, and through holes in manhole covers.
Subcatchments are created in the model to generate RDII flows to the collection system. The land surface
and subsurface parameters are then calibrated to produce simulated flows that reflect the conditions
observed through flow monitoring. Model simulations provide long-term flow hydrographs that can be
analyzed to quantify the magnitude and frequency of peak flow events for use in conveyance design.
6.1 Calibration Period Dry Weather Flow
DWF can be measured during prolonged dry periods when wet weather flows are relatively small. In the
Pacific Northwest, DWF is best measured in August and September after the aquifers recede and groundwa-
ter baseflows are lowest. Furthermore, these months experience comparatively lower chances of rainfall,
which further improves the likelihood that the observed flow is not influenced by wet weather.
Flow monitoring data across all monitors generally included two dry periods, during the two observed
summers, from which the DWF portion could be calculated. Figure 6-1 below provides the observed flow
data for the AUBRN53 monitor, as an example, with observed rainfall plotted at the top. The brackets
indicate the dry periods that were selected to represent typical DWF patterns. In both of these periods,
rainfall is minimal and the groundwater baseflow is assumed to be minimal as the hydrograph levels off from
its wet season recession. The lack of a recession indicates that the groundwater infiltration has likely ceased
and the only remaining component of the hydrograph is the flow attributable to DWF.
Sanitary Sewer Model Development
14
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 6-1. AUBRN53 monitor flow data and observed rainfall
Calculating DWF for implementation into the model involves assessing an average flow magnitude that can
be scaled on an hourly basis to represent the daily use patterns observed in the flow data. Although an
average amount of DWF is created within the system, it enters the system in peaks and troughs based on
usage patterns that vary throughout the day. Hourly scaling factors multiply against the average flow magni-
tude to represent those troughs and peaks within the model. For example, the average flow magnitude for
the AUBWV016 monitoring basin is 1.15 mgd; however, the peak water usage on a weekday from 8 to 9
a.m. is 1.31 mgd. To account for that hour’s DWF, the model scales the 1.15 mgd average value by a factor
of 1.14 to achieve 1.31 mgd within the model from 8 to 9 a.m. Average flow magnitudes and hourly factors
for weekdays, Saturdays, and Sundays were calculated for each of the flow monitors within the area of study
and built into MIKE URBAN’s “cyclic patterns” engine to simulate Auburn’s DWF.
Flow monitors located downstream of other flow monitoring locations were used to quantify DWF for inter-
mediate areas. For example, flow monitor MSTTR22A is located downstream from the MSTTR48 flow
monitor. The DWF associated with the intermediate MSTTR22A monitoring basin is equal to the total DWF at
the MSTTR22A monitor minus the DWF at the MSTTR48 monitor. Figure 6-2 below illustrates the DWF
pattern calculated for weekday DWF at the AUBRN53 monitor. The observed flow data are presented in blue
and the simulated DWF (given the calculated average DWF magnitude [7.168 mgd] and the daily and hourly
factors) is presented in red.
Dry periods for DWF calculation
Sanitary Sewer Model Development
15
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 6-2. AUBRN53 monitor DWF calculation and hourly pattern
Blue = observed; red = modeled
Figure 6-3Error! Reference source not found. is a schematic of the flow monitors used to calculated DWF
rates and patterns including calculated estimates for the average total and average incremental DWF rates
for each monitor. Note that the PACIFICPS_FM monitor was not used because it is located within a section of
KC-owned pipe that is not included in the hydraulic model. DWF for the area upstream of the PACIFICPS_FM
monitor was captured by the next monitor downstream: AUBWV016.
Sanitary Sewer Model Development
16
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 6-3. Dry weather flow schematic
Total = total observed DWF at meter, Individual = DWF intermediate contribution from the monitoring basin
DWF can be loaded into a MIKE URBAN model in a variety of ways. For this modeling effort, DWF was loaded
as a geocoded network load using the “Load Allocation” tool. The benefit of using this methodology is that
the loads for an entire monitoring basin can be lumped into one network load, which can easily be switched
between active and inactive without having to change the properties of every node in the model to. This
makes for a more organized model and facilitates modeling different scenarios with ease and reduced risk
of error. DWF was loaded proportionally across all modeled nodes within each monitoring basin based on the
upstream pipe length weighting calculations detailed in Section 6.2. For the ABN008 monitoring basin, the
0.15 mgd average DWF flow magnitude was proportionally divided across all 63 of the modeled nodes using
the area factors described in Section 6.2.
As a high-level check, the total DWF for the SSA was used to estimate per capita water usage. In 2010, the
residential population of Auburn was 70,420. The total DWF generated within the City’s SSA was calculated
as the average DWF at the AUBRN53 monitor minus the average DWF at AUBWV016 (monitoring inflows
from KC-owned pipes). This calculates to 6.02 mgd of DWF, which equates to 86 gallons per capita per day
(gpcd) of potable water usage. This value is consistent with Robert Elwell’s understanding of the City’s water
consumption and indicates that the DWF values calculated for this modeling effort are reasonable.
6.2 Development of Subcatchments
The City of Auburn’s collection system is a separated system, which means runoff from land surfaces should
be routed into the stormwater conveyance system rather than into sewer pipes. However, monitoring data
indicate there is a wet weather flow signature in the sewers, indicating either groundwater, surface water, or
some combination of both is present.
Loading the land surface into the model involves the creation of subcatchments, which are model represen-
tations of the land surface that create wet weather flow. Each subcatchment has an assigned area (as well
as other hydrologic parameters) and loads RDII to a collection system node. Every node in the hydraulic
model was assigned a subcatchment representative of the contributing area upstream of each node. The
exception to this rule are dummy nodes, which are fictitious nodes used to connect links in complex hydrau-
Sanitary Sewer Model Development
17
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
lic configurations. To account for the upstream contributing area at a given node, upstream pipe length was
multiplied by an assumed width. Upstream contributing area was calculated as the length of pipe between a
given modeled node and the next upstream modeled node and/or the length of upstream pipes not included
in the hydraulic model, multiplied by 200 feet of width (100 feet on each side of the conduit). For areas of
the collection system that are not included in the hydraulic model (such as a neighborhood with all 8-inch-
diameter pipes as depicted in Figure 6-4 below in red), this weighting system accounts for the proportionally
higher amount of system inflows assumed to be from that area. Conversely, a node along a mainline may
have a small area of influence that is simply representative of the length of one upstream link (the link in
blue in Figure 6-4). In a given wet weather event, proportionally more flow is expected to be loaded to the
mainline at MH 1409-29 than would be expected to enter the collection system at MH 1409-16. This
weighted approach attempts to account for this field process. ArcGIS software was used to calculate up-
stream pipe lengths. Those data were then brought over to Microsoft Excel, where subcatchment area
calculations were made. During calibration, the total area of some monitoring basins was adjusted to match
KC modeling efforts (described in Section 6.3). However, the area proportions defined by this method were
retained.
Figure 6-4. Upstream area of influence example
In addition to assigning areas to model subcatchments, the subcatchment areas can be divided against the
total area of a monitoring basin, for example, to create non-dimensional area factors for use in distributing
Sanitary Sewer Model Development
18
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
other types of loads across the collection system on a monitoring basin basis. Subsequent sections below
describe the use of the area weighting factors to distribute those flows.
The development of the AUBWV016 basin’s hydrologic model deviated slightly from the monitoring basins
wholly within the City’s SSA. The AUBWV016 monitor observes flow entering the SSA within a KC main line
from KC’s collection system upstream. Although the KC pipes in this monitoring basin can be displayed
within a map (see Figure 3-1), elevation data for the pipes are missing in KC’s GIS and these pipes were not
included in the MIKE URBAN hydraulic model. A single model subcatchment instead represents the entire
monitoring basin and its area calculation follows the methodology established above. The KC-owned Pacific
PS within the monitoring basin is consequently not hydraulically modeled. Its flow signature is inherent to the
hydrologic calibration of the subcatchment.
6.3 Calibration Period Wet Weather Flow
Calibrating the RDII module of MIKE URBAN is a process of iteratively adjusting hydrologic modeling parame-
ters to match observed flows from flow monitoring records for each of the calibration basins. This modeling
effort used the MOUSE Time-Area model for surface water discharges in combination with the MOUSE RDI
groundwater modeling routine to calculate RDII flow rates. This combination of hydrologic routines is con-
sistent with the preferred methods used by KC.
The monitoring basin boundaries defined the boundaries for the breaking apart the MIKE URBAN model into
calibration basin models so hydrologic parameters could be assigned specific to the flow characteristics
observed for each flow monitoring basin. Calibration of the MIKE URBAN model was performed by moving
sequentially from the upstream monitoring basins to the most downstream basins. BC contacted KC to
inquire as to whether KC would be willing to share its parameters for this area to expedite our calibration. On
March 28, 2014, King County sent BC MOUSE models for each of the flow monitoring basins within the
Auburn study area. These models provided a set of initial model parameters from which to begin calibration.
In some cases, further calibration was not required as the KC parameters performed adequately within the
calibration basin models. A goal of meeting wet weather peak magnitudes and volumes within 10 percent
was the established calibration criterion for this modeling effort.
The KC MOUSE models assumed different total subcatchment areas for each monitoring basin, so the BC
subcatchment areas within each calibration basin model were scaled until the total area matched the area
in the KC models. This preserved the proportional loading of RDII established by the upstream pipe length
calculations while maintaining the water balance generated by the KC MOUSE models. By maintaining the
same water balance as KC, the calibration effort of the MIKE URBAN model was expedited.
The KC-parameterized MIKE URBAN calibration basin models were run through the calibration period (fall
2009 through spring 2011) to ensure that the KC parameters, once transposed to the new BC models,
performed adequately against the flow monitor data. In most cases, small adjustments were made to the
hydrologic model parameters (indicated in Table 6-1) to refine the calibration. Such adjustments are ex-
pected because the KC MOUSE models were simplified models consisting of one large subcatchment and
one conduit, while the BC models account for the full length of travel throughout the collection system.
Adjustments were sometimes necessary to compensate for the peak flow attenuation effects of the collec-
tion system.
Adjustments were made to both the surface runoff and RDI engine parameters depending on the calibration
needs of the model. The RDI engine accounts for the predominant portion of the collection system’s wet
weather flow because Auburn’s collection systems directly connected inflow is minimal. Consequently,
calibration was focused primarily on the RDI engine’s response. Figure 6-5 below provides a schematic of
the RDI engine indicating the different storage zones and components of the flow hydrograph.
Sanitary Sewer Model Development
19
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 6-5. MIKE URBAN RDI engine schematic
Source: DHI MIKE URBAN User Manual
Table 6-1 below provides the model parameters adjusted in both the surface and RDI engines and what
effect they have on the hydrograph.
Table 6-1. MIKE URBAN Hydrologic Model Calibration Parameters
Model Engine Parameter name Description Effect on calibration
Time Area A – Surface
Runoff
Imperviousness (%) Relative amount of impervious area Rapid inflow response peak and volume
Time of concentration (min) Time for runoff to travel from the distal end
of the subcatchment Rapid inflow response timing and shape
Initial loss (in) Initial abstraction depth before rapid
response can be discharged Rapid inflow peak timing
Sanitary Sewer Model Development
20
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Table 6-1. MIKE URBAN Hydrologic Model Calibration Parameters
Model Engine Parameter name Description Effect on calibration
RDI – Groundwater
Infiltration
Groundwater area (%) Percent of subcatchment area available
for groundwater storage and discharge to
collection system
Duration of groundwater response
Surface storage (in) Storage layer that must be filled before a
rapid response can be discharged and
before infiltration to subsurface zones can
begin
Timing of rapid response peak and volume of
subsurface response
Root zone storage (in) The zone below the surface and above the
groundwater storage layer that transitions
moisture between the two layers
Its depth affects the hydrologic responses of both the
surface and groundwater zones
Overland coefficient A fraction that determines the extent to
which excess rainfall (after the surface
storage is filled) runs off as overland flow
vs. infiltrating to the lower zone. A value of
0 sends all rainfall excess to the lower
zone.
Affects volume of overland flow
Groundwater coefficient The proportion of the groundwater
catchment to the surface catchment. A
value less than 1 makes the groundwater
catchment smaller than the associated
surface catchment.
Affects volume of groundwater response
Tc overland flow (hr) Time constant used to determine how fast
the surface flow responds to rainfall and
the total volume discharged.
Affects overland flow peak timing
Tc interflow (hr) Time constant used to determine how fast
the interflow responds to rainfall and the
total volume discharged.
Affects interflow peak timing.
Tc baseflow (hr) Time constant used to control hydrograph
recession during dry periods. Affects shape of groundwater response
Specific yield Determines the specific yield of the
groundwater aquifer.
Affects aquifer storage volume, and as a function,
volume and shape of groundwater response
Calibration focused on matching the seasonal rise and fall of wet-weather-induced baseflow as well as
matching peak response due to individual storms. Over the course of two wet seasons, there were nine large
storms against which to calibrate the model’s peak runoff response, with the December 12, 2010, storm
providing the largest peak flow. Preference was given to calibrating to the largest storms in the record
because the model’s primary use is to simulate large storms. Two rising baseflow limbs from the falls of
2009 and 2010 and the falling baseflow limb of 2010 provided a sufficient amount of data to calibrate the
baseflow response.
Figure 6-6 below shows the calibration plot at AUBRN53 for the December 12, 2010 storm. The AUBRN53
monitoring basin model is the farthest downstream monitoring basin, so its performance reflects the per-
formance of the entire model upstream, as those monitoring basin models flow into this model. The
AUBRN53 model nearly matches the observed peak of 19 mgd by simulating only 2.4 percent lower. The
recession out of the storm nearly matches and the DWF patterns visually appear to be well represented in
the model. This model slightly overestimates flows in the days leading up to the peak on December 12;
however, the error on the total volume is 6.6 percent, which is well below the 10 percent maximum error
goal for this modeling effort.
Sanitary Sewer Model Development
21
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 6-6. AUBRN53 wet weather calibration
Blue = observed; red = modeled
Section 7: Long-Term Simulations
BC ran hydrologic model simulations to produce long-term flow hydrographs that can be used to analyze the
magnitude and frequency of historical wet weather events. The long-term rainfall record (described in
Section 4.1) provides enough data for the model to be run from January 1, 1949, through December 31,
2012 (64 years), including 3 months of “spin up” time to remove the influence of initial-conditions parame-
ter estimates. Identification of the 20-year storm is necessary as the stated LOS goal for the sewer system is
referenced to a recurrence of 20 years (see Chapter 3 of the 2014 Comprehensive Plan). Running the model
through a 20-year storm will indicate areas of the system that back up or flood, which can help to identify
areas that do not meet the stated LOS.
Each of the calibration basin models were run using the 64-year record and the results were summed to
create a citywide RDII time series, which does not include DWF. The summed time series represents the total
RDII entering the collection system at any moment in the 64-year period. The citywide time series was then
separated into discrete events using a 24-hour inter-event duration to isolate periods when the RDII peaked
above a threshold minimum flow value of 8 mgd. This means that only the events that produced more than 8
mgd of peak RDII were included, and smaller events were removed from the analysis.
The selected events were ordered from largest to smallest and assigned a rank. A rank of 1 was assigned to
the largest storm, 2 to the second-largest, and so on. Cunnane plotting parameters were used to estimate
the recurrence interval for each event in years, as follows (Maidment, 1992): 𝑇𝑅= 𝑖+0.2𝑅𝑅𝑅𝑅−0.4
Where: 𝑖=𝑅𝑛𝑛𝑛𝑛𝑛 𝑜𝑜 𝑠𝑖𝑛𝑛𝑠𝑅𝑠𝑖𝑜𝑅 𝑦𝑛𝑅𝑛𝑠 𝑅𝑅𝑅𝑅=𝑛𝑅𝑅𝑅 𝑜𝑜 𝑠𝑠𝑜𝑛𝑛 𝑤ℎ𝑛𝑛𝑛 1 𝑖𝑠 𝑠ℎ𝑛 𝑠𝑅𝑛𝑙𝑛𝑠𝑠 𝑠𝑠𝑜𝑛𝑛
Sanitary Sewer Model Development
22
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
The above equation will not identify a historical storm event that has exactly a 20-year peak flow recurrence.
For a 64-year record, the third-largest event is estimated to have about a 25-year recurrence and the fourth-
largest event is estimated to have about an 18-year recurrence using Cunnane parameters. The third- and
fourth-largest events from the 64-year simulated record produced peak discharges within ±0.2 mgd of each
other; therefore, either event could be used to approximate a 20-year event recurrence. The larger of the two
events, occurring on February 5, 1996, was selected as the 20-year event to be used to evaluate collection
system capacity and identify deficiencies in the conveyance system that may affect the systems LOS.
Figure 7-1 and Table 7-1 below provide the peak RDII frequency for specific recurrence intervals based on
log-interpolation between plotted events. These flows represent the peak RDII entering the collection system
throughout the entire SSA. The aggregated RDII inflows neither account for system storage, nor do they
include DWF. The aggregated RDII inflow time series does provide a clear distinction between storms in their
hydrologic response as collection system factors such as hydraulic capacity, flooding, and travel time are not
able to distort the peak flow signature of wet weather events.
Figure 7-1. Citywide peak RDII Cunnane plot
Peak RDII frequency values were calculated for each calibration basin to examine the relative contributions
from each basin. Dividing the peak RDII by the total length of the upstream collection system to calculate
unit RDII values provides insight into the relative contribution of infiltration and inflow in each basin. Table
7-2 provides the peak 20-year RDII statistics for each monitoring basin. Peak RDII for monitoring basins
downstream of upland basins does not account for the inflows from the upstream basins. In other words, the
RDII values are specific to the RDII created solely within the monitoring basin regardless of the influence of
upstream basins. Monitoring basins ABN022 and ABN023 illustrate the importance of calculating unit RDII
values. Although ABN022 has a higher 20-year peak RDII than ABN023, the unit RDII per mile of pipe for
ABN023 is higher. This indicates that the pipes within the ABN023 monitoring basin may be in worse
physical condition than those in the ABN022 basin, as ABN023 pipes create more RDII per length of pipe.
0
5
10
15
20
25
30
35
0.1 1.0 10.0 100.0 1000.0
Pe
a
k
R
D
I
I
(
m
g
d
)
Recurrence Interval (years)
Table 7-1. Peak RDII Cunnane
Estimated Flow Frequency
Flow Threshold RDII (mgd)
Q 100 32.77
Q 50 30.25
Q 25 27.19
Q 20 27.03
Q 10 24.69
Q 5 21.76
Q 2 18.75
Q 1 15.36
Sanitary Sewer Model Development
23
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Table 7-2. Peak RDII per Monitoring Basin
Monitoring basin 20-year RDII (mgd) RDII/in.-diam-mile* (mgd/in.-mi) RDII/mi** (mgd/mi)
ABN008 0.44 0.006 0.051
ABN022 1.10 0.010 0.106
ABN023 0.47 0.015 0.171
ABN024 0.11 0.004 0.040
ABN027 0.58 0.003 0.045
ABN032 1.95 0.038 0.367
ABRN53 5.43 0.031 0.969
AUBWV016 6.90 0.030 0.263
LakelandHills 0.23 0.001 0.006
LKH001A 0.66 0.051 0.582
MSTTR02A 3.23 0.006 0.054
MSTTR22A 5.31 0.019 0.195
MSTTR48A 3.76 0.011 0.125
WINT003 0.77 0.008 0.202
WINT038 1.05 0.008 0.088
* RDII per inch-diameter mile is a calculation of peak RDII divided by the sum of the upstream pipe diameters multiplied by
their respective total length of pipe in miles. This accounts for the fact that larger-diameter pipes can provide more pathways
for infiltration to enter the collection system.
** RDII per mile is a calculation of the peak RDI divided by the total length of upstream pipe in miles without regard for the size
of those upstream pipes.
Section 8: Future Conditions
The calibrated model was modified to estimate future flows given anticipated population growth, develop-
ment, and hydraulic modifications within the SSA. In Auburn, it is anticipated that population growth will
contribute additional DWF to the system alongside additional RDII from extension of the sewer system to
previously unsewered and undeveloped areas. Modified modeling simulations were used to identify potential
capacity restrictions that will need to be eventually addressed with capital improvements. The following
sections describe how the baseline model was modified to represent the future conditions of the 6-year
(2020) and 20-year (2034) planning horizons.
8.1 Future Dry Weather Flow
Future increases in DWF are expected to come from two sources: population growth (both new development
and redevelopment) and extending the sewer to areas that are currently using septic systems to treat their
wastewater. The following two sections describe the source data and parameterization of these sources of
DWF for both the 6-year and 20-year planning horizons.
8.1.1 Dry Weather Flow from Population Expansion
The state of Washington is divided into Traffic Analysis Zone (TAZ) polygons to track current populations and
to estimate future populations on a small-area basis. These TAZ polygons are used predominantly to plan
Sanitary Sewer Model Development
24
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
transportation improvements to accommodate increasing populations. The population estimates for each
TAZ can be used to estimate the anticipated populations within the SSA and, consequently, the increase in
DWF from those residents. Table 8-1 maps the TAZ polygons used in this modeling effort against the bound-
ary of the SSA (see the Sewer Comprehensive Plan for more information about the SSA). Note that the TAZ
polygons do not line up directly with the boundary of the proposed SSA.
Figure 8-1. TAZ polygons within the vicinity of Auburn
To account for the differing boundaries between the TAZ polygons and the SSA, an assumption of uniform
population distribution within the TAZ was made in order to perform an area-weighted approach to popula-
tion growth estimation based on the fractional area of the TAZs within the proposed SSA (the exception is
TAZ 748, which is described below). For example, approximately 10.5 percent of TAZ 448 is located within
the proposed SSA. Therefore, only 10.5 percent of the future population projection would be applied to the
estimated increase in DWF to the collection system. The area factor for TAZ 448 then becomes 10.5 per-
cent.
Two exceptions to this method were applied in this effort. The first exception deals with TAZ polygons 432,
444, 445, and 763, which are fully outside of the proposed SSA but whose residents discharge to KC’s
collection system in the southwest corner of the proposed SSA. These polygons use a 100 percent area
Sanitary Sewer Model Development
25
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
factor and are assumed to fully discharge to KC’s pipes. The second exception accounts for the non-
uniformity of the existing population distribution in TAZ 748 in the north Lake Tapps area. Visual inspection
of the TAZ indicated that the population density was non-uniform across the proposed SSA boundary, so the
TAZ’s area factor was increased from 31.4 percent to 62.8 percent, which allowed the 2013 population
estimate within the city boundary using the factored TAZ polygons to equal the 2013 population estimate
from the City provided by the City of Auburn (Chamberlain, 2014). This step provides assurance that the TAZ
polygon area factors method matches the City’s own understanding of its population numbers in the base-
line scenario.
The TAZ calculations were used to estimate population increases both in the proposed SSA and on KC land
(portion that use sewer lines that run through the city) for the 2020 and 2034 planning horizons using linear
interpolation. The TAZ-based City of Auburn population estimates calculated by BC were within 1 percent of
the citywide estimates provided by the City for the two planning horizons, indicating that the TAZ calculations
were corroborating the work the City had already performed within the city’s boundary. Table 8-1 below
provides the population estimates and area factors for each TAZ polygon. Red, underlined text indicates TAZ
polygons outside of the proposed SSA but whose populations use KC sewer lines that run through the City.
Table 8-1. Future Population Estimates by TAZ Polygon
TAZ ID Area factor 2010 population 2013 population 2020 population 2034 population
404 10.2% 811 823 852 937
405 100% 4,678 4,871 5,320 6,240
406 10.2% 516 532 569 640
409 22.1% 2,068 2,122 2,247 2,542
411 100% 4,428 4,718 5,395 6,505
430 8.6% 678 712 790 912
432 100% 3,905 4,138 4,681 5,583
433 100% 1,576 2,589 4,952 7,348
434 100% 136 142 156 181
435 100% 83 86 94 111
436 100% 4,177 4,265 4,469 5,106
437 100% 4,479 4,499 4,546 5,068
438 83.2% 4,330 4,525 4,981 5,869
439 100% 2,376 2,386 2,410 2,686
440 100% 0 0 0 0
441 100% 12 12 12 13
442 100% 9,186 9,248 9,392 10,481
443 100% 1,296 1,307 1,332 1,494
444 100% 4,317 4,348 4,419 4,764
445 100% 4,905 4,889 4,851 5,028
446 100% 3,344 3,511 3,902 4,626
447 79.9% 6,299 6,355 6,484 7,275
448 10.4% 217 223 237 262
Sanitary Sewer Model Development
26
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Table 8-1. Future Population Estimates by TAZ Polygon
TAZ ID Area factor 2010 population 2013 population 2020 population 2034 population
449 1.1% 46 46 47 49
450 100% 7,544 7,930 8,829 10,481
451 71.9% 2,872 2,954 3,144 3,627
748 62.8%* 9,267 9,379 9,641 10,351
763 100% 349 365 402 463
Service area population** 83,896 86,974 94,155 108,642
TAZ calculated city population 70,420 73,235 79,802 92,804
City estimate N/A 73,235 80,532 N/A
Percent difference N/A 0.0% -0.9% N/A
* Area fraction for TAZ 748 (north Lake Tapps) increased to make the TAZ calculated city population match the City’s estimate for 2013.
** Service area refers to the area inside which all collected sewage routes through the city (including inside KC mainlines).
Red, underlined text indicates TAZ polygons outside of the proposed SSA with populations whose sewage is conveyed through the city in KC’s
mainlines.
An assumption of 80 gpcd was used to assign future DWF to the model for the additional future populations,
and all future population expansion is assumed to be connected to the sanitary sewer. By comparison, the
calculated average DWF for the city in 2013 is 86 gpcd (which includes industrial and commercial inputs as
well). Anecdotal information from the City indicates that future DWF estimates are near 60 gpcd. Given that
future development is likely to include higher-efficiency water features that reduce per capita water de-
mands, a planning-level value of 80 gpcd is considered conservative. Industrial and commercial inputs were
assumed to scale proportionally with population growth.
Future DWF from population growth was applied to the model in addition to existing DWF for both the 2020
and 2034 planning horizons. Application of the future DWF was performed using MIKE URBAN’s water load
boundary condition editor, which allows a specified flow magnitude to be loaded at any node and scaled or
manipulated by a factor or pattern. Water loads representing future DWF magnitudes were applied to the
model’s nodes within each TAZ with load distribution based on the upstream pipe length factors described in
Section 6.2. For example, TAZ 405 is estimated to experience population growth of 642 people within the
proposed SSA by 2020, which equates to 0.051 mgd of future DWF. That 0.051 mgd of DWF was then
distributed proportionally across the nodes within TAZ 405 based on the area factors from the upstream
pipe length calculations (described in Section 6.2).
8.1.2 Dry Weather Flow from Sewer Extension
The City plans to extend the sewer system into residential areas that currently use onsite septic systems.
These areas will contribute DWF to the collection system in addition to the DWF increases from population
growth described above. Accounting for the amount and source of the DWF from the sewer extension
involved planning the locations of the future sewers and estimating the chance they will be developed by
each of the planning horizons. BC identified areas where the sewer system was likely to be expanded to
serve both developed and undeveloped areas. Those locations were geocoded as proposed sewer lines
within ArcGIS. The City provided a “percent chance of development” for these sewer lines based on the
2020 and 2034 planning horizons (Table 8-2).
Sanitary Sewer Model Development
27
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 8-2. Proposed sewer extensions and development percentages
Legend: (2020 Percentage, 2034 Percentage)
Sanitary Sewer Model Development
28
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Sewer lines were classified as serving either new development or existing development. To estimate the
magnitude of the DWF from existing development, the existing DWF from eight headwater-monitoring basins
was divided against the total length of pipe in those basins to get a value of 0.52 mgd of DWF per 100,000
feet of pipe. This value provides an estimate of the amount of DWF produced per length of pipe, which can
estimate DWF from sewer line extension to developed areas. DWF from new development is accounted for
in the population expansion statistics.
Applying the percent chance of development to the estimated flow magnitude for the lines to the existing
development adjusts that future DWF down to a value representative of the chance that the DWF will ever
exist in the sanitary system. Flows were loaded into the model at the nearest node located downstream of
the future line. A citywide average diurnal pattern was used to scale the DWF throughout the day.
8.2 Future Wet Weather Flow
The construction of new sewer lines will create additional pathways for RDII to enter the collection system
because of inevitable holes, cracks, joint failures, and faulty connections. Accounting for that future RDII in
the model is important to make a more reasonable estimate of the future HGL when additional RDII enters
the collection system from sewer extension. Figure 8-2 (Section 8.1.2) indicates the locations of the planned
sewer extensions, as well as the percent chance that they will be constructed by the 2020 and 2034
planning horizons. All of these planned lines, whether for new development or to connect existing develop-
ment, are subject to RDII; thus, the development type distinction is irrelevant in the calculation of future wet
weather flow. It is assumed that existing lines will have approximately the same amount of structural defects
in the future, so their RDII loading is unchanged for future conditions.
BC used KC’s planning-level peak RDII value of 1,500 gallons per acre per day (Earth Tech Team, 2005) to
estimate RDII into the new sewer lines for a 20-year storm. Calculating a contributing area to the proposed
sewer lines was performed by multiplying the sewer length by 200 feet of influence width (described in
Section 6.2). To account for the chance that the pipe segment will be in the ground by the planning horizon,
the percent chance of development factor was multiplied by the contributing area to scale it down. Equation
8-1 below describes the flow calculation for RDII from sewer extension.
Equation 8-1. Flow from sewer extension RDII 𝑄𝑖𝑖𝑖𝑖𝑖𝑖−𝑚𝑚𝑚=(1500 𝑙𝑔𝑅𝑔)∗(𝑔𝑖𝑔𝑛 𝑠𝑛𝑅𝑙𝑠ℎ 𝑜𝑠)∗(200 𝑜𝑠 𝑤𝑖𝑔𝑠ℎ)∗(𝑃𝑠𝑅𝑅𝑅𝑖𝑅𝑙 𝐻𝑜𝑛𝑖𝐻𝑜𝑅 𝐷𝑛𝐷𝑛𝑠𝑜𝑔𝑛𝑛𝑅𝑠 𝑃𝑛𝑛𝑃𝑛𝑅𝑠𝑅𝑙𝑛)∗(1 𝑜𝑠243,560 𝑅𝑃𝑛𝑛 )∗(1 𝑀𝑀1,000,000 𝑀𝑅𝑠)
The future wet weather RDII was loaded into the model using a scaled unit RDII time series and an applied
factor. The RDII time series of the ABN032 basin was selected because the hydrograph provides a large
volume of water to the system because of its elongated rising and recession limbs. A high-volume time series
will produce a conservative result when evaluating storage and conveyance.
The ABN032 time series was scaled to a peak value of 1 mgd such that a factor within the model could be
used to multiply the time series to the appropriate value for each loading node based on Equation 8-1
above. For example, if the required flow at a node from a sewer line extension is 0.05 mgd peak, a factor of
0.05 is applied to the RDII time series to produce 0.05 mgd of peak flow to the model. This method provides
a representative hydrograph shape to use within the model as compared to using a constant RDII value at
each node, which would provide an overly conservative flow volume.
Figure 8-3 shows the difference between high and low volume time series. The two time series experience
identical peak flow rates; however, the purple time series puts significantly more water into the collection
Sanitary Sewer Model Development
29
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
system and is more likely to indicate capacity deficiencies in the system than the red time series. Using a
high volume hydrograph within the model ensures that the peak is propagated downstream rather than
allowing for attenuation of the instantaneous peak which could leave downstream bottlenecks unexposed.
Figure 8-3. High and low volume time series comparison example
Red = low-volume storm; purple = high-volume storm
For areas of redevelopment where housing will become denser, an assumption that denser developments
will most likely use the existing sewer lateral rather than install new laterals prevents the need to load future
RDII from those areas. Consequently, RDII from new development was the only type of future RDII included
in the model.
8.3 Future Hydraulic Improvements
After the flow monitoring period between 2009 and 2011, KC embarked on a two-phase project to reduce
flooding risks in capacity-limited sections of its sanitary sewer lines. For Phase I, KC constructed the SRT in
2013, which routes wastewater flow from the MSTTR48 monitoring basin (diversion at the intersection of K
Street SE and 17th Street SE) to the Auburn West Interceptor, thereby alleviating capacity deficiencies in the
diversion area. This was included in the baseline-conditions model. Phase II of the project will route flow
from the Pacific PS to the Auburn West Interceptor, thereby reducing surcharging near the intersection of
Boundary Boulevard SW and O Street SW. This project needed to be included in the future-conditions
scenarios as it is planned but not yet designed or constructed.
At the time of modeling, design drawings were not available for the Pacific PS project. A conceptual layout of
the project indicated that a new force main would be constructed to discharge to an interceptor line that
runs parallel to the Auburn West Interceptor before the two lines join at MH 807-46. Information such as the
pump station’s capacity, operational changes, force main diameter, etc., was not available; therefore,
assumptions were made to fill in these gaps.
Sanitary Sewer Model Development
30
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
In the calibration-conditions model, the Pacific PS was not modeled, nor was KC’s upstream collection
system. The area tributary to the Pacific PS is a part of the AUBWV016 monitoring basin. Because the pump
station belongs to KC, it was not explicitly included in the baseline-conditions hydraulic model but, rather, its
inflow hydrograph was captured in the calibration of the AUBWV016 hydrologic model. As described in
Section 6.2, the AUBWV016 hydrologic model was modeled with one subcatchment to load KC flows into the
City’s collection system without a full collection system model. Although GIS data exist that describe the
layout of the County’s pipes tributary to the AUBWV016 flow monitor, elevation data are lacking such that
the collection system could not be built without additional data. Therefore, the AUBWV016 model subcatch-
ment (representing the hydrology of the monitoring basin) was subdivided to isolate the area contributing to
the Pacific PS.
KC GIS data were used to calculate the total length of pipe upstream of the AUBWV016 flow monitor,
including the areas upstream of the Pacific PS. The ratio of the length of pipe upstream of the Pacific PS to
the total length of pipe within the AUBWV016 monitoring basin was used to divide flows from the AUBWV016
subcatchment into two subcatchments. Figure 8-4 below shows the pipes located within the AUBWV016
monitoring subcatchment and the proposed force main layout and discharge location. The green pipes
upstream of the Pacific PS account for 59 percent of the total pipe length within the monitoring basin.
Consequently, the AUBWV016 subcatchment in the hydrologic model was split and 59 percent of the area
was re-routed to MH 807-46.
Sanitary Sewer Model Development
31
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 8-4. Pacific PS re-route
Existing Pacific PS
discharge location
Monitor
Sanitary Sewer Model Development
32
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
8.4 Future-Conditions Summary
Preparing the MIKE URBAN model to simulate future conditions required adjustments to both the hydrologic
inputs and the hydraulic network. DWF and RDII must be increased to account for population growth and
future development. Hydraulic modifications to the collection system must reflect planned infrastructure
projects. Table 8-2 summarizes the three results-producing periods of analysis and the major changes
associated with them.
Table 8-2. Analysis Period Model Modifications
Scenario Dry weather flow Wet weather flow Hydraulic modifications
Baseline None None Stuck River Trunk (constructed 2013)
2020 (6-year planning horizon) Population expansion = +0.82 mgd
Sewer extension = 0.36 mgd Sewer extension = + 0.56 mgd Pacific PS new discharge location*
2034 (20-year planning horizon) Population expansion = + 1.98 mgd
Sewer extension = +0.78 mgd Sewer extension = + 1.23 mgd None*
*Analysis period includes hydraulic modifications from previous periods.
Section 9: Model Results
The following sections describe the results of the hydraulic capacity evaluations. A 20-year event was
simulated to identify locations where the sewer collection system does not have sufficient capacity to meet
the LOS standard. The City’s LOS standard for new sewers is defined as no surcharging of pipes during the
20-year storm (where surcharging is defined as the HGL rising above the pipe crown). For existing sewers,
the standard is relaxed to allow surcharging below an excessive level, although the magnitude of excess is
not defined. The maps in the subsequent sections identify the minimum freeboard calculated at each
modeled manhole. Minimum freeboard at a manhole is calculated as the depth from the maximum simulat-
ed HGL elevation to the surface elevation. Manholes with maximum HGL elevations that exceed the rim
elevation are considered to be in flooding condition. Assessment of minimum freeboard gives indication of
hydraulic restrictions as the system is forced to back up and surcharge when water cannot pass through
restricted sections. For the purposes of this analysis, manholes with 3 feet of minimum freeboard or less are
indicated as they are surcharged high enough to cause or nearly cause flooding because of hydraulic
restrictions.
Capacity evaluations were run with all manholes set as “sealed.” Sealing the manholes prevents water
losses due to flooded manholes and forces sewer flows to continue downstream. This retains flows for
evaluation of downstream pipe capacities so that the entire collection system can be evaluated for peak flow
capacity.
9.1 Baseline Conditions
Results from the baseline-conditions simulation indicate one area that floods (along Boundary Boulevard SW
west of O Street SW) and 20 additional locations with less than 3 feet of freeboard. Investigation of the 20
locations with less than 3 feet of freeboard indicates that all of the manholes are shallow with depths
between 2.5 and 3.5 feet, which means that even DWF alone will result in 3 feet of freeboard or less. These
minimum freeboard locations are therefore not to be interpreted as indicative of a hydraulic restriction that
causes surcharging induced by high amounts of RDII. Figure 9-1 presents the minimum freeboard at all
manholes within the model in the baseline condition.
Sanitary Sewer Model Development
33
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 9-1. Baseline-conditions minimum freeboard
Boundary Blvd SW
flooding area
Sanitary Sewer Model Development
34
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 9-2 shows MH 409-33 (one of the 20 identified manholes outside of the Boundary Boulevard area
with less than 3 feet of minimum freeboard), which has a calculated freeboard of 2.14 feet. The MH depth is
2.41 feet, which means the depth of flow is only 0.27 foot. Because only 27 percent of the pipe depth (1-
foot diameter pipe) is being used at the peak of the 20-year storm, the calculated minimum freeboard in this
MH is not indicative of a hydraulic restriction. This situation is similar at the 19 other shallow manhole low
freeboard locations throughout the city. (Note: MIKE URBAN’s results viewer displays in metric units.)
Figure 9-2. Low-freeboard short manhole
Figure 9-3 below shows the simulated HGL along Boundary Boulevard SW between State Route (SR) 167
and O Street SW and indicates that MH 906-26 and MH 906-12 would flood during the 20-year event. There
is only 2,400 feet of Auburn sewer upstream of this location (to the left of MH 906-14 in the figure), so the
flooding is induced primarily by RDII from the 139,000 feet of KC line upstream of the AUBWV016 flow
monitor (which discharges into MH 906-06 in the figure) rather than RDII from the Auburn line itself. Flows
from upstream of the AUBWV016 monitoring basin include the existing discharges from the Pacific PS.
Figure 9-3. Flooding along Boundary Boulevard SW
MH Depth = 2.41 ft.
Flooding predicted
Sanitary Sewer Model Development
35
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
The baseline-conditions model run indicates that there is area with flooding and it is due to high flows from
KC. Twenty other locations have calculated minimum freeboard levels of less than 3 feet; however, this
calculation is due to short manhole depths. These 20 locations were inspected and hydraulic results of the
model did not indicate that there were instances of hydraulic restriction during the 20-year storm. These 20
locations can therefore be ignored as they do not represent a risk to LOS.
9.2 2020 Conditions
Results from the 2020 simulation indicate that re-routing flow from the Pacific PS to the Auburn West
Interceptor reduced the HGL along Boundary Boulevard SW such that no manholes show a minimum
freeboard of less than 3 feet. However, the additional flows in the KC-owned Auburn West Interceptor raise
the HGL enough to cause the minimum freeboard to fall below 3 feet in eight manholes between 15th Street
SW and 15th Street NW. Figure 9-4 provides the minimum freeboard map for the 2020 simulation.
Sanitary Sewer Model Development
36
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 9-4. 2020 conditions minimum freeboard
Auburn West
Interceptor
surcharged line
Sanitary Sewer Model Development
37
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 9-5 shows the surcharged segment of the Auburn West Interceptor from MH 907-01 to MH 607-20,
which includes the eight manholes with freeboard less than 3 feet (1 meter in the figure). This line is owned
by KC and is therefore not considered for CIP by the City.
Figure 9-5. 2020 surcharge of the KC-owned Auburn West Interceptor
9.3 2034 Conditions
Results from the 2034 simulation are considered to be more uncertain than the results of the baseline and
2020 scenarios. This is because accurately predicting the pace and location of development and population
expansion 20 years into the future is inherently difficult. Consequently, the following results should be
interpreted as indications of what could happen given best estimates, rather than predictions of what will
necessarily happen. The model results indicated that the area around the intersection of Perimeter Road SW
and 1st Street SW is likely to experience flooding due to increased flows within the Auburn West Interceptor.
Additionally, future sewerage of the existing development upstream of the Verdana PS is likely to produce
surcharge in the line along 118th Avenue SE. Figure 9-6 presents the results of the minimum freeboard
evaluation for the 2034 planning horizon.
Sanitary Sewer Model Development
38
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 9-6. 2034 conditions minimum freeboard
Perimeter Rd.
flooding area
118th Ave SE.
high HGL
Sanitary Sewer Model Development
39
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Figure 9-7 shows the maximum HGL along 118th Avenue SE to the Verdana PS wetwell. MH 313-115 has a
minimum of 0.5 foot of freeboard at the peak of the event. This area, although already developed, is planned
to be sewered to bring the existing development onto the City’s collection system. The model indicates that
when this area is sewered, the shallow sloped section of 8-inch-diameter pipe upstream of the Verdana PS is
likely to surcharge to within 0.5 foot of the lowest manhole (313-116) rim elevation, indicating a high risk of
flooding at that location. This is attributable to both the shallow slope of the 8 inch line as well as a diameter
decrease to 6 inches just upstream of the Pump Station at 413-50. It is recommended that the City verify
this diameter decrease as the GIS database (the source of the diameter information) may be incorrect).
Assuming the diameter information is correct, the modeling results indicate that although the Verdana PS
has been sized and built to handle increased flows associated with future sewerage, the existing sewer lines
may not have enough capacity to convey that sewage to the pump station in 2034.
Figure 9-7. Surcharged line upstream of Verdana PS
Figure 9-8 presents the hydraulic profile of the Perimeter Road flooding area along the Auburn West Inter-
ceptor. The added flows from the SRT, the diversion of Pacific PS, as well as the increased flows from
population growth and new sewer lines all increase the HGL in this line, resulting in flooding at two locations.
Although this flooding violates the City’s LOS, the line is owned by KC and is therefore not considered for CIP
development by the City.
Figure 9-8. Hydraulic profile of KC-owned Auburn West Interceptor at Perimeter Road
0.5 ft freeboard
Verdana P.S. wetwell
flooding predicted
Sanitary Sewer Model Development
40
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Section 10: Conclusions
BC used MIKE URBAN to construct and calibrate a model of the City’s sewer collection system including
outlying areas that drain into the city. The model was used to evaluate conveyance capacity deficiencies for
existing baseline conditions, as well as the future 6-year and 20-year conditions corresponding with the
planning horizons of the Comprehensive Plan. The model was calibrated using 2 years of flow data from 14
KC flow monitoring sites that were within the Auburn vicinity. Calibrating over this long period of time helps
to reduce model calibration uncertainty as a variety of storm sizes and durations are used to adjust the
model parameters.
BC modeled future H&H conditions for the 6-year and 20-year planning horizons using population growth
and sewer extension estimates, which add dry and wet weather flow to the collection system by adding new
users and new pipe. Hydraulic features constructed after the flow monitoring period, such as new pump
stations and a trunk line, were included in the model to accurately represent baseline conditions. A future
modification to King County’s Pacific PS, although still in conceptual design, was modeled in both future
conditions to estimate the effect of that modification on hydraulic conveyance.
BC analyzed long-term hydrographs to identify an event in the 64-year rainfall record that is closest to a 20-
year event. The 20-year event, which took place on February 5, 1996, was simulated in the existing-
conditions, future 6-year, and future 20-year conditions models to evaluate the LOS of the collection system
in all three conditions. Although LOS is defined stringently for new construction as no surcharging of the pipe
crown during a 20-year storm, surcharge below an excessive amount is allowed for the existing system
before LOS is considered to be violated. Modeling results analysis identified manholes with less than 3 feet
of minimum freeboard during the 20-year storm as an indicator of pipe sections with hydraulic restriction
that cause surcharge of the system.
In general, the City of Auburn’s sanitary collection system has no capacity-related issues. Although the
baseline-conditions modeling indicates flooding along Boundary Boulevard, this issue will be alleviated by
the re-routing of discharge from KC’s Pacific PS in the coming years. The 6-year planning horizon simulation,
which accounts for the Pacific PS’s proposed new discharge location, indicates that the Auburn West
Interceptor will experience surcharge as the HGL will rise to within 3 feet of minimum freeboard because of
increased discharge from the pump station. The interceptor is owned by KC and is not considered for CIP.
The 20-year planning horizon simulation indicates that flooding is likely to occur along the Auburn West
Interceptor and surcharge is likely upstream of the Verdana PS. The sewer lines upstream of the Verdana PS
are owned by the City; however, CIP is not planned around results from this scenario because of the uncer-
tainty associated with the assumptions for 20 years into the future.
Sanitary Sewer Model Development
41
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
References
Brown and Caldwell, December 2009. City of Auburn Comprehensive Sewer Plan. Prepared for the City of Auburn by Brown
and Caldwell.
Chamberlain, Elizabeth “RE: TAZ data.” April 18, 2014. E-mail. City of Auburn, Wash.
Earth Tech Team, Regional Needs Assessment Report, Regional Infiltration and Inflow Control Program, Appendix A5 Assump-
tions for Regional I/I Control Program, King County, 2005 (pg. 7)
Elwell, Robert. “County Plans.” June 12, 2014. E-mail. Sewer Utility Engineer, City of Auburn, Wash.
King County,”Hydrologic Data Download Page,” Hydrologic Information Center Home, 2014,
http://green.kingcounty.gov/wlr/waterres/hydrology/ Maidment, David R., ed. Handbook of Hydrology. New York, N.Y.:
McGraw-Hill, 1992. Print.
Washington State University Puyallup Extension, “Historic Data,” AgWeatherNet, 2014, http://weather.wsu.edu/awn.php
Western Washington Hydrologic Model 2012. http://www.ecy.wa.gov/programs/wq/stormwater/wwhmtraining/index.html
Sanitary Sewer Model Development
A-1
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Attachment A: Modifications to Collection System GIS
MH IDIssue
807-28Elevation likely too low, appears to look like a syphon. Rim elevation much lower than nearby contour
908-19Invert likely too high. Profile jumps up for this MH. Interpolate the elevation for a smooth profile
808-80,
708-12
Elevation likely too low, appears to look like a syphon. Interpolate the elevation for a smooth profile. MH elevations in area
do not match 2008 Comp Plan model
508-28 Elevation likely too low, appears to look like a syphon. MH not in 2008 comp plan model. Interpolated to a new elevation for
consistent profile.
1009-91 Elevation too low, appears to look like a syphon. Use invert from 909-56 in 2008 comp plan (same location, name appears to
have changed).
1012-69Elevation was low for outlet node of a forcemain. Use 2008 comp plan model for elevations
1009-95Elevation likely too high. Interpolate to constant slope to match rest of trunk. Node not in 2008 comp plan
1009-44Elevation likely too high. Use 2008 comp plan model value to prevent adverse slopes
1009-101Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value.
909-52Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value.
909-102Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value.
809-91Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value.
709-40Elevation likely too high. Creates adverse slope on inlet pipe. Use 2008 comp plan model value.
709-80 Elevation likely too high. Creates adverse slope on inlet pipe. Use 2008 comp plan model value for invert. Rim elevation was
below pipe crown, so interpolate to rim elevation.
709-28Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
810-20Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
710-25Elevation likely too high. Creates adverse slope on inlet pipe. Use 2008 comp plan model value
710-34Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
710-32Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
610-48Elevation likely too high. Creates adverse slope on inlet pipe. Use 2008 comp plan model value
610-123,
610-125,
310-124
Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
610-12,
610-117 Elevation likely too high. Creates adverse slope on inlet pipe. Use 2008 comp plan model value
610-09Elevation likely too high. Creates adverse slope on inlet pipe. Use 2008 comp plan model value
611-56Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
511-54Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
510-76Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
511-26,
511-27 Elevation likely too high. Creates adverse slope on inlet pipe. Use 2008 comp plan model value
511-41,
511-39,
411-68,
410-77,
410-76
Elevations adjusted to 2008 Comp Plan to remove adverse slopes
509-19,
509-18
Elevation likely too high. Creates adverse slope on inlet pipe. Use 2008 comp plan model value. Set 509-19 Rim to same as
the next MH downstream in the intersection as the comp plan value is illogically high (almost 30 feet higher than same
intersection MH)
509-07Elevation likely too high. Creates adverse slope on inlet pipe. Use 2008 comp plan model value.
908-19Elevation likely too high. Creates adverse slope on inlet pipe. Interpolate the invert as MH does not exist in 2008 comp plan.
708-29Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
808-80Elevation likely too low. Creates adverse slope on outlet pipe. Interpolate a value as MH not in 2008 Comp Plan
1009-100Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value.
1010-91Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
811-13Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
508-28Elevation likely too low. Creates adverse slope on outlet pipe. Interpolate a value as MH not in 2008 Comp Plan
614-90Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
714-05Elevation likely too low. Creates adverse slope on outlet pipe. Interpolate value as MH not in 2008 comp plan
713-18Elevation likely too high. Creates adverse slope on inlet pipe. Use 2008 comp plan model value.
413-66Elevation likely too high. Creates adverse slope on inlet pipe. Invert interpolated as MH is not in 2008 comp plan.
512-91Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
611-07Elevation likely too high. Creates adverse slope on inlet pipe. Use 2008 comp plan value.
709-28Rim elevation much higher than nearby contours. Interpolated value used.
409-40Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
410-78Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
410-01Elevation likely too high. Creates adverse slope on inlet pipe. Use 2008 comp plan value.
410-25Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
409-55Invert likely too high. Creates adverse slope on outlet pipe. Interpolate an invert as MH not in 2008 comp plan model.
606-86MH Depth 1.2', not likely. Rim elevation interpolated
506-07Invert too high. Creates adverse slope on inlet pipe. Use 2008 comp plan value.
906-14,
906-26,
1006-02,
1006-04
Inverts too low, use comp plan values. Otherwise, water would not leave the pipes to travel downstream (steep adverse slope
after 1006-04)
906-05Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
807-28Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
307-07Elevation likely too high. Creates adverse slope on inlet pipe. Use 2008 comp plan value.
409-72,
309-11,
309-10
Elevations incorrect. Use 2008 Comp Plan values
409-01Elevation too low, creates adverse slope outlet pipe. Use 2008 Comp Plan value
309-75,
309-74 Elevations too low, creates adverse sloped mainline. Use 2008 comp plan values
309-68Elevation too low. Use 2008 comp plan value
309-76,
309-49,
309-48,
309-47,
309-46,
309-68
Elevations need adjustment to 2008 comp plan values as pipeline is adverse
207-11,
207-05 Elevations need adjustment down as pipeline is adverse. Use 2008 comp plan values
713-22Invert too high, interpolate a lower value as 2008 comp plan value is integer.
713-14,
713-13 Elevations too high, create adverse slopes. Use 2008 comp plan values
709-84,
709-87,
709-68,
709-67,
709-63
Adjust all values to 2008 Comp Plan values as this section is adverse
710-72,
710-73,
710-74
Adjust all values to 2008 Comp Plan values as this section is adverse
608-32,
508-13 Adjust all values to 2008 Comp Plan values as this section is adverse
509-12Elevation too high, creates adverse slope. Interpolate value as comp plan value is a copy of upstream value.
409-51Elevation too low, creates adverse slope. Interpolate value.
512-10Elevation likely too low. Creates adverse slope on outlet pipe. Use 2008 comp plan model value
407-01Value likely too high, interpolated down so mainline is constant slope.
307-18Value likely too high, interpolated down so mainline is constant slope.
1208-38,
1108-09,
1108-07,
1108-08,
1008-09,
908-24,
908-25,
908-26
Interpolated MH inverts based on 0.002 ft/ft slope upstream of known elevation at 908-15. Rim elevations estimated from
contours
Sanitary Sewer Model Development
B-1
Use of contents on this sheet is subject to the limitations specified at the beginning of this document.
AuburnSewer_ModelTM_Final.docx
Attachment B: Pump Station Data
In
v
e
r
t
El
e
v
a
t
i
o
n
(
f
t
)
Ri
m
E
l
e
v
a
t
i
o
n
(f
t
)
De
p
t
h
(f
t
)
Un
i
t
A
r
e
a
(f
t
3/f
t
)
Vo
l
u
m
e
(
f
t
3
)
Di
a
m
e
t
e
r
,
a
s
s
u
m
i
n
g
ci
r
c
u
l
a
r
(
f
t
)
St
a
r
t
L
e
v
e
l
(
f
t
)
S
t
o
p
L
e
v
e
l
(
f
t
)
S
t
a
r
t
L
e
v
e
l
(
f
t
)
S
t
o
p
L
e
v
e
l
(
f
t
)
16
1
0
A
r
e
a
1
9
2
5
2
2
.
2
1
5
4
0
.
8
1
1
8
.
6
2
8
.
2
7
5
2
5
.
8
2
2
6
5
2
9
.
2
5
2
7
.
5
5
3
0
.
2
5
2
7
.
5
3
2
5
15
0
9
T
e
r
r
a
c
e
V
i
e
w
2
5
8
.
5
7
7
.
6
19
.
1
28
.
2
7
53
9
.
9
5
7
6
64.663.865.663.8675
13
0
9
E
l
l
i
n
g
s
o
n
R
o
a
d
2
72
.
3
93
.
9
21
.
6
50
.
2
7
10
8
5
.
8
3
2
8
77.575.879.075.81527
10
0
9
F
S
t
r
e
e
t
2
80
.
2
1
0
3
.
3
2
3
.
1
28
.
2
7
65
3
.
0
3
7
6
86.785.387.785.3400
61
1
R
i
v
e
r
s
i
d
e
2
41
.
9
6
7
1
.
2
1
2
9
.
2
5
28
.
2
6
82
6
.
6
0
5
6
48.447.049.447.0400
71
0
R
S
t
r
e
e
t
2
53
.
9
8
71
17
.
0
2
28
.
2
6
48
0
.
9
8
5
2
6
60.259.261.259.2100
70
5
P
e
a
s
l
e
y
R
i
d
g
e
2
45
4
.
5
5
4
7
4
.
2
5
1
9
.
7
28
.
2
6
55
6
.
7
2
2
6
460.5458.6461.5458.6275
61
4
R
a
i
n
e
r
R
i
d
g
e
2
38
5
.
2
5
4
0
5
1
9
.
7
5
28
.
2
6
55
8
.
1
3
5
6
391.2389.1392.2389.1200
81
1
V
a
l
l
e
y
M
e
a
d
o
w
s
2
46
.
9
8
7
2
.
5
2
5
.
5
2
28
.
2
6
72
1
.
1
9
5
2
6
51.550.552.550.5125
51
1
2
2
n
d
S
t
r
e
e
t
2
41
57
.
4
3
1
6
.
4
3
28
.
7
47
1
.
5
4
1
6
47.145.848.145.8550
20
9
D
S
t
r
e
e
t
2
33
.
5
50
16
.
5
28
.
2
7
46
6
.
4
5
5
6
39384038400
71
0
8
t
h
S
t
r
e
e
t
2
60
.
2
5
7
8
.
2
5
18
28
.
2
7
50
8
.
8
6
6
64.163.0565.0563.05150
13
0
9
L
a
k
e
l
a
n
d
2
0
0
0
40
0
0
NA
00000
15
1
1
N
o
r
t
h
T
a
p
p
s
2
50
5
5
3
7
.
4
5
3
2
.
4
5
28
.
2
6
91
7
.
0
3
7
6
512510.6513510.6510
12
0
8
S
a
f
e
w
a
y
2
0
0
0
0
0
0
00000
41
3
V
e
r
d
a
n
a
3
36
3
.
1
7
3
9
4
3
0
.
8
3
17
5
53
9
5
.
2
5
15
37
1
.
3
7
3
6
9
.
3
7
3
7
2
.
3
7
369.371750
21
0
A
u
b
u
r
n
4
0
2
23
57
.
4
34
.
4
63
.
6
21
8
7
.
8
4
9
28.526.529.526.5440
91
2
D
o
g
w
o
o
d
2
25
5
2
7
3
.
4
1
8
.
4
50
.
2
6
92
4
.
7
8
4
8
260259260.8259300Single Pump Capacity (gpm)
Nu
m
b
e
r
o
f
P
u
m
p
s
St
r
u
c
t
u
r
e
I
D
P
u
m
p
S
t
a
t
i
o
n
N
a
m
e
Lag Pump
We
t
W
e
l
l
Lead Pump
2016 Comprehensive Sewer Plan
C-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
Pump Station InformationAppendix C:
Ci
t
y
o
f
A
u
b
u
r
n
C
o
m
p
r
e
h
e
n
s
i
v
e
S
e
w
e
r
P
l
a
n
Pu
m
p
S
t
a
t
i
o
n
D
a
t
a
S
u
m
m
a
r
y
In
v
e
r
t
El
e
v
a
t
i
o
n
(f
t
)
Ri
m
El
e
v
a
t
i
o
n
(
f
t
)
De
p
t
h
(f
t
)
Un
i
t
A
r
e
a
(f
t
3/f
t
)
Vo
l
u
m
e
(f
t
3
)
Di
a
m
e
t
e
r
,
as
s
u
m
i
n
g
ci
r
c
u
l
a
r
(
f
t
)
St
a
r
t
L
e
v
e
l
(f
t
)
St
o
p
L
e
v
e
l
(f
t
)
St
a
r
t
Le
v
e
l
(
f
t
)
St
o
p
L
e
v
e
l
(ft)
16
1
0
A
r
e
a
1
9
2
0
0
6
0
9
-
0
7
3
8
3
-
0
0
V
2
5
2
2
.
2
1
5
4
0
.
8
1
1
8
.
6
2
8
.
2
7
5
2
5
.
8
6
5
2
9
.
2
5
2
7
.
5
5
3
0
.
2
5
2
7
.
5
3
2
5
0
.
4
6
8
0
.
2
3
4
15
1
1
N
o
r
t
h
T
a
p
p
s
2
0
0
7
0
9
-
0
7
3
8
2
-
0
0
N
2
5
0
5
5
3
7
.
4
5
3
2
.
4
5
2
8
.
2
6
9
1
7
.
0
6
5
1
2
5
1
0
.
6
5
1
3
5
1
0
.
6
5
1
0
0
.
7
3
4
0
.
3
6
7
15
0
9
T
e
r
r
a
c
e
V
i
e
w
2
0
0
7
0
9
-
0
7
3
8
2
-
0
0
N
2
5
8
.
5
7
7
.
6
1
9
.
1
2
8
.
2
7
5
4
0
.
0
6
6
4
.
6
6
3
.
8
6
5
.
6
6
3
.
8
6
7
5
0
.
9
7
2
0
.
4
8
6
21
0
A
u
b
u
r
n
4
0
2
0
1
0
1
2
-
0
7
2
0
6
-
0
0
2
2
3
5
7
.
4
3
4
.
4
6
3
.
6
2
1
8
7
.
8
9
2
8
.
5
2
6
.
5
2
9
.
5
2
6
.
5
4
4
0
0
.
6
3
4
0
.
3
1
7
13
0
9
E
l
l
i
n
g
s
o
n
R
o
a
d
2
0
1
1
12
-
0
7
2
1
0
-
0
0
-
F
2
7
2
.
3
9
3
.
9
2
1
.
6
5
0
.
2
7
1
0
8
5
.
8
8
7
7
.
5
7
5
.
8
7
9
.
0
7
5
.
8
1
5
2
7
2
.
1
9
9
1
.
0
9
9
10
0
9
F
S
t
r
e
e
t
1
9
8
0
0
8
-
7
8
2
2
-
D
2
8
0
.
2
1
0
3
.
3
2
3
.
1
2
8
.
2
7
6
5
3
.
0
6
8
6
.
7
8
5
.
3
8
7
.
7
8
5
.
3
4
0
0
0
.
5
7
6
0
.
2
8
8
71
0
R
S
t
r
e
e
t
1
9
7
7
0
7
-
7
5
6
3
-
F
2
5
3
.
9
8
7
1
1
7
.
0
2
2
8
.
2
6
4
8
1
.
0
6
6
0
.
2
5
9
.
2
6
1
.
2
5
9
.
2
1
0
0
0
.
1
4
4
0
.
0
7
2
81
1
V
a
l
l
e
y
M
e
a
d
o
w
s
1
9
9
2
1
4
-
1
7
2
3
-
Z
2
4
6
.
9
8
7
2
.
5
2
5
.
5
2
2
8
.
2
6
7
2
1
.
2
6
5
1
.
5
5
0
.
5
5
2
.
5
5
0
.
5
1
2
5
0
.
1
8
0
0
.
0
9
0
71
0
8
t
h
S
t
r
e
e
t
1
9
7
4
1
4
-
1
7
9
5
-
Z
2
6
0
.
2
5
7
8
.
2
5
1
8
2
8
.
2
7
5
0
8
.
9
6
6
4
.
1
6
3
.
0
5
6
5
.
0
5
6
3
.
0
5
1
5
0
0
.
2
1
6
0
.
1
0
8
51
1
2
2
n
d
S
t
r
e
e
t
1
9
6
7
8
0
0
-
5
2
4
1
5
7
.
4
3
1
6
.
4
3
2
8
.
7
4
7
1
.
5
6
4
7
.
1
4
5
.
8
4
8
.
1
4
5
.
8
5
5
0
0
.
7
9
2
0
.
3
9
6
91
2
D
o
g
w
o
o
d
2
0
1
0
0
9
-
0
7
3
9
4
-
0
0
-
F
2
2
5
5
2
7
3
.
4
1
8
.
4
5
0
.
2
6
9
2
4
.
8
8
2
6
0
2
5
9
2
6
0
.
8
2
5
9
3
0
0
0
.
4
3
2
0
.
2
1
6
70
5
P
e
a
s
l
e
y
R
i
d
g
e
2
0
0
1
0
8
-
8
4
7
8
-
K
2
4
5
4
.
5
5
4
7
4
.
2
5
1
9
.
7
2
8
.
2
6
5
5
6
.
7
6
4
6
0
.
5
4
5
8
.
6
4
6
1
.
5
4
5
8
.
6
2
7
5
0
.
3
9
6
0
.
1
9
8
61
4
R
a
i
n
e
r
R
i
d
g
e
1
9
8
0
0
7
-
7
6
9
9
-
C
2
3
8
5
.
2
5
4
0
5
1
9
.
7
5
2
8
.
2
6
5
5
8
.
1
6
3
9
1
.
2
3
8
9
.
1
3
9
2
.
2
3
8
9
.
1
2
0
0
0
.
2
8
8
0
.
1
4
4
61
1
R
i
v
e
r
s
i
d
e
1
9
8
1
0
7
-
7
7
8
4
-
R
2
4
1
.
9
6
7
1
.
2
1
2
9
.
2
5
2
8
.
2
6
8
2
6
.
6
6
4
8
.
4
4
7
.
0
4
9
.
4
4
7
.
0
4
0
0
0
.
5
7
6
0
.
2
8
8
41
3
V
e
r
d
a
n
a
2
0
1
1
19
-
0
1
3
6
8
-
0
0
-
N
3
3
6
3
.
1
7
3
9
4
3
0
.
8
3
1
7
5
5
3
9
5
.
3
1
5
3
7
1
.
3
7
3
6
9
.
3
7
3
7
2
.
3
7
3
6
9
.
3
7
1
7
5
0
2
.
5
2
0
1
.
2
6
0
Pu
m
p
/
P
u
m
p
S
t
a
t
i
o
n
M
a
n
u
f
a
c
t
u
r
e
r
I
n
f
o
r
m
a
t
i
o
n
(A
l
l
p
u
m
p
s
t
a
t
i
o
n
s
e
x
c
e
p
t
2
2
n
d
S
t
r
e
e
t
P
S
)
22
n
d
S
t
r
e
e
t
P
S
Sm
i
t
h
a
n
d
L
o
v
e
l
e
s
s
C
o
r
n
e
l
l
P
u
m
p
s
14
0
4
0
S
a
n
t
a
F
e
T
r
a
i
l
D
r
i
v
e
Le
n
e
x
a
,
K
a
n
s
a
s
6
6
2
1
5
P
o
r
t
l
a
n
d
,
O
R
Ph
o
n
e
:
9
1
3
.
8
8
8
.
5
2
0
1
Lo
c
a
l
E
q
u
i
p
m
e
n
t
R
e
p
r
e
s
e
n
t
a
t
i
v
e
L
o
c
a
l
E
q
u
i
p
m
e
n
t
R
e
p
r
e
s
e
n
t
a
t
i
v
e
AD
S
E
q
u
i
p
m
e
n
t
I
d
e
a
l
P
u
m
p
PO
B
o
x
8
1
0
4
5
8
6
2
5
2
1
9
t
h
S
E
Se
a
t
t
l
e
,
W
A
9
8
1
0
8
W
o
o
d
i
n
v
i
l
l
e
,
W
A
9
8
0
7
2
Ph
o
n
e
:
2
0
6
.
7
6
3
.
3
6
0
0
P
h
o
n
e
:
4
2
5
.
4
8
1
.
7
7
7
7
Le
a
d
P
u
m
p
Au
b
u
r
n
W
a
y
S
o
u
t
h
S
e
w
e
r
B
a
s
i
n
We
s
t
H
i
l
l
S
e
w
e
r
B
a
s
i
n
Le
a
h
H
i
l
l
S
e
w
e
r
B
a
s
i
n
Ye
a
r
Bu
i
l
t
Se
r
i
a
l
N
u
m
b
e
r
La
g
P
u
m
p
Single Pump Capacity (gpm)Single Pump Capacity (MGD)Second Pump Capacity (MGD)
So
u
t
h
H
i
l
l
S
e
w
e
r
B
a
s
i
n
Va
l
l
e
y
S
e
w
e
r
B
a
s
i
n
St
r
u
c
t
u
r
e
ID
Pu
m
p
S
t
a
t
i
o
n
N
a
m
e
Nu
m
b
e
r
of
Pu
m
p
s
We
t
W
e
l
l
Us
e
of
co
n
t
e
n
t
s
on
th
i
s
sh
e
e
t
is
su
b
j
e
c
t
to
th
e
li
m
i
t
a
t
i
o
n
s
sp
e
c
i
f
i
e
d
at
th
e
en
d
of
th
i
s
do
c
u
m
e
n
t
.
C-2
2016 Comprehensive Sewer Plan
D-1
Use of contents on this sheet is subject to the limitations specified at the end of this document.
City of Auburn Comprehensive Sewer Plan.docx
SEPA Compliance Appendix D: