SANITARY SEWER COMPREHENSIVE PLAN...Sanitary Sewer Comprehensive Plan iii October, 2016 Lake Stevens...

SANITARY SEWER COMPREHENSIVE PLAN

Serving the

City of Lake Stevens Urban Growth Area Snohomish County, Washington

October 2016

LAKE STEVENS SEWER DISTRICT

Commissioners

Pam Stevens Frank McDaniel

Brent Kirk

General Manager

Michael Bowers

District Office

1106 Vernon Road Suite A Lake Stevens, WA 98258

Telephone: 425-334-8588

Website: www.lkstevenssewer.org

Engineer

CHS Engineers, LLC 12507 Bel-Red Road, Suite 101

Bellevue, Washington 98005-2500

Telephone: 425-637-3693 Website: www.chsengineers.com

http://www.lkstevenssewer.org/

http://www.chsengineers.com/

Sanitary Sewer Comprehensive Plan i October, 2016 Lake Stevens Sewer District CHS Engineers, LLC

TABLE OF CONTENTS

SUMMARY AND RECOMMENDATIONS BACKGROUND ................................................................................................ S-1 SEWER SERVICE AREA AND ADDITIONAL STUDY AREA ........................... S-1 POPULATION AND GROWTH ......................................................................... S-2 DESIGN CRITERIA ........................................................................................... S-8 SEWER SYSTEM – EXISTING SYSTEM ....................................................... S-11 SEWER SYSTEM – COLLECTION SYSTEM ANALYSIS .............................. S-12 CAPITAL IMPROVEMENT PLAN ................................................................... S-13 OPERATIONS AND MAINTENANCE ............................................................. S-13 FINANCIAL ANALYSIS ................................................................................... S-13 DEVELOPER PROJECT STANDARDS .......................................................... S-16 RECOMMENDATIONS ................................................................................... S-17 CHAPTER 1 – INTRODUCTION GENERAL ......................................................................................................... 1-1 SCOPE OF WORK............................................................................................ 1-2 PROJECTS COMPLETED SINCE THE 2007 PLAN ........................................ 1-3 RELATED PLANNING DOCUMENTS .............................................................. 1-3

Growth Management Act (GMA) Related Plans ..................................... 1-3 Wastewater System Plans And Reports ................................................. 1-5

CHAPTER 2 – SERVICE AND STUDY AREA CHARACTERIZATION INTRODUCTION ............................................................................................... 2-1

Lake Stevens Sewer District ................................................................... 2-1 City of Lake Stevens ............................................................................... 2-2 Service and Study Area .......................................................................... 2-2

PHYSICAL CHARACTERISTICS ...................................................................... 2-3 Topography ............................................................................................ 2-3 Soils And Geology .................................................................................. 2-3 Climate ................................................................................................... 2-4 Critical Areas .......................................................................................... 2-5

UTILITIES ......................................................................................................... 2-6 Water System ......................................................................................... 2-6 Other Wastewater Systems .................................................................... 2-6

CHAPTER 3 – LAND USE AND PLANNING CRITERIA INTRODUCTION ............................................................................................... 3-1 PLANNING PERIOD ......................................................................................... 3-1 GROWTH MANAGEMENT ............................................................................... 3-1 LAND USE AND ZONING ................................................................................. 3-2

City Of Lake Stevens .............................................................................. 3-3 Snohomish County ................................................................................. 3-5

POPULATION ................................................................................................... 3-8 Historical Population ............................................................................... 3-9 Existing Population ............................................................................... 3-10

Sanitary Sewer Comprehensive Plan ii October, 2016 Lake Stevens Sewer District CHS Engineers, LLC

Household Size ......................................................................... 3-10 Existing Population Connected to Sanitary Sewer ..................... 3-11 Schools ................................................................................................. 3-12 Projected Future Population ................................................................. 3-13

SEWER CONNECTIONS ................................................................................ 3-15 CURRENT SEWER SERVICE CONNECTIONS AND ERUS ......................... 3-15

Downtown Subarea Plan ...................................................................... 3-16 Buildout Population ............................................................................... 3-17 Potential RUTA Population ................................................................... 3-18

CHAPTER 4 – DESIGN AND PLANNING CRITERIA INTRODUCTION ............................................................................................... 4-1 DEFINITION OF TERMS .................................................................................. 4-1

Ammonia ................................................................................................ 4-1 Average Annual Flow ............................................................................. 4-1 Average Dry Weather Flow..................................................................... 4-1 Base Flow ............................................................................................... 4-2 Biochemical Oxygen Demand (Bod) ....................................................... 4-2 Chlorine .................................................................................................. 4-2 Domestic Wastewater ............................................................................. 4-3 Equivalent Residential Unit (Eru) ............................................................ 4-3 Infiltration ................................................................................................ 4-3 Inflow ...................................................................................................... 4-3 Maximum Day Flow ................................................................................ 4-4 Maximum Month Flow (Treatment Design Flow) .................................... 4-4 Non-DOMESTIC Wastewater ................................................................. 4-4 Other Contaminants Of Concern ............................................................ 4-4 Peak Hour Flow ...................................................................................... 4-4 Priority Pollutants .................................................................................... 4-5 Suspended Solids ................................................................................... 4-5 Wastewater............................................................................................. 4-6

EXISTING WASTEWATER FLOWS AND LOADING........................................ 4-6 Historical Wastewater Flows And Loadings ............................................ 4-6

EXISTING EQUIVALENT RESIDENTIAL UNITS (ERUS) .............................. 4-10 WINTER WATER CONSUMPTION ................................................................ 4-10

Equivalent Residential Units ................................................................. 4-11 Infiltration and Inflow ............................................................................. 4-12 Infiltration and Inflow Analysis using EPA criteria ...................... 4-14 Infiltration ................................................................................... 4-15 Inflow ......................................................................................... 4-16 Flow Monitoring ......................................................................... 4-16 I/I Summary ............................................................................... 4-16

PROJECTED SEWER SERVICE AREA POPULATION, ERUS AND FLOWS 4-17 EXISTING AND PROJECTED INFLUENT BOD5 AND TSS LOADING .......... 4-18

Existing BOD5 Loading ......................................................................... 4-18 Existing Total Suspended Solids Loading ............................................ 4-18

Sanitary Sewer Comprehensive Plan iii October, 2016 Lake Stevens Sewer District CHS Engineers, LLC

PROJECTED WASTEWATER LOADINGS .................................................... 4-19 DESIGN CRITERIA ......................................................................................... 4-20 CHAPTER 5 – EXISTING COLLECTION SYSTEM INTRODUCTION ............................................................................................... 5-1 WASTEWATER COLLECTION SYSTEM ......................................................... 5-2

GRAVITY SEWERS ............................................................................... 5-3 Campus Park (Old Hewlett-Packard Trunk) ................................. 5-3 Frontier Heights Trunk ................................................................. 5-3 Vernon Road West Trunk ............................................................ 5-3 Glenacres/Meridian Trunk ........................................................... 5-4 91st Avenue Se Trunk .................................................................. 5-4 Davies Road Trunk ...................................................................... 5-4 Stitch Road Trunk ........................................................................ 5-4 South Lake Stevens Road Trunks ............................................... 5-4 Vernon/Lundeen Trunk ................................................................ 5-5 Lake Drive Trunk ......................................................................... 5-5 99th Avenue Ne Trunk .................................................................. 5-5 Callow Road Trunk ...................................................................... 5-5 Vernon Road East Trunk ............................................................. 5-5 26th Street NE Trunk .................................................................... 5-5 Grade Road Trunk ....................................................................... 5-6 East Lake Shore Drive Trunk ....................................................... 5-6 Vernon Road Diversion Trunk ..................................................... 5-6 Southwest Interceptor .................................................................. 5-6 LIFT STATIONS AND FORCE MAINS ................................................... 5-6 LIFT STATION SCADA SYSTEM ......................................................... 5-11 Existing Lift Station SCADA System .......................................... 5-11 SCADA for Newer Lift Stations .................................................. 5-11 WASTEWATER TREATMENT FACILITY (WWTF) .............................. 5-12 Former Wastewater Treatment Plant .................................................... 5-18

INTERLOCAL AGREEMENTS AND MORATORIA ........................................ 5-18 City Of Marysville .................................................................................. 5-19 City Of Lake Stevens ............................................................................ 5-19

CHAPTER 6 – COLLECTION SYSTEM EVALUATION INTRODUCTION ............................................................................................... 6-1

Hydraulic Model ...................................................................................... 6-1 Record Drawings .................................................................................... 6-2 Lift Stations ............................................................................................. 6-3 Basins and Sub-Basins .......................................................................... 6-3 Hydraulic Modeling Analysis ................................................................... 6-4

HYDRAULIC MODELING ANALYSIS ............................................................... 6-4 Existing and Build-Out Population .......................................................... 6-4 Schools ................................................................................................... 6-5 Commercial/Industrial ............................................................................. 6-5

Sanitary Sewer Comprehensive Plan iv October, 2016 Lake Stevens Sewer District CHS Engineers, LLC

Infiltration/Inflow ...................................................................................... 6-5 Flow Monitoring ...................................................................................... 6-5 Hydraulic Modeling Data ........................................................................ 6-5 Other Pipeline Deficiencies .................................................................... 6-7

LIFT STATION CAPACITY ANALYSIS ............................................................. 6-7 FORCE MAIN CAPACITY EVALUATION ......................................................... 6-8 SUMMARY OF COLLECTION SYSTEM DEFICIENCIES ................................ 6-9

BASIN A1.............................................................................................. 6-13 BASIN B1.............................................................................................. 6-13 BASIN B2.............................................................................................. 6-13 BASIN B3.............................................................................................. 6-13 BASIN B4.............................................................................................. 6-14 BASIN B5.............................................................................................. 6-14 BASIN B6.............................................................................................. 6-14 BASIN B7.............................................................................................. 6-14 BASIN B8.............................................................................................. 6-15 BASIN B9.............................................................................................. 6-16 BASIN B10............................................................................................ 6-16 BASIN B11............................................................................................ 6-16 BASIN B12............................................................................................ 6-16 BASIN C1 ............................................................................................. 6-17 BASIN C2 ............................................................................................. 6-17 BASIN C3 ............................................................................................. 6-18 BASIN C4 ............................................................................................. 6-18 BASIN D1 ............................................................................................. 6-18 BASIN D2 ............................................................................................. 6-20 BASIN D3 ............................................................................................. 6-20 BASIN D4 ............................................................................................. 6-21 BASIN D5 ............................................................................................. 6-21 BASIN D6 ............................................................................................. 6-21 BASIN D7 ............................................................................................. 6-21 BASIN D8 ............................................................................................. 6-22 BASIN D9 ............................................................................................. 6-22 BASIN D10 ........................................................................................... 6-23 BASIN E1.............................................................................................. 6-23 BASIN E2.............................................................................................. 6-24 BASIN E3.............................................................................................. 6-25 BASIN E4.............................................................................................. 6-26 BASIN E5.............................................................................................. 6-26 BASIN E6.............................................................................................. 6-26 BASIN E7.............................................................................................. 6-26 BASIN F1 .............................................................................................. 6-27 BASIN F2 .............................................................................................. 6-27 BASIN G1 ............................................................................................. 6-27 BASIN G2 ............................................................................................. 6-28 BASIN G3 ............................................................................................. 6-28

Sanitary Sewer Comprehensive Plan v October, 2016 Lake Stevens Sewer District CHS Engineers, LLC

BASIN G4 ............................................................................................. 6-28

BASIN H1 ............................................................................................. 6-28 BASIN H2 ............................................................................................. 6-29 BASIN H3 ............................................................................................. 6-29 BASIN K1.............................................................................................. 6-29 OTHER COLLECTION SYSTEM PROJECTS AND EQUIPMENT ....... 6-29

CHAPTER 7 – CAPITAL IMPROVEMENT PLAN INTRODUCTION ............................................................................................... 7-1 RECOMMENDED WASTEWATER FACILITY IMPROVEMENTS .................... 7-2

Wastewater Treatment Facility ............................................................... 7-2 RECOMMENDED COLLECTION SYSTEM IMPROVEMENTS ........................ 7-2 CHAPTER 8 – OPERATION AND MAINTENANCE INTRODUCTION ............................................................................................... 8-1 DISTRICT MISSION .......................................................................................... 8-1 RESPONSIBILITY AND AUTHORITY ............................................................... 8-1

Personnel Certification ........................................................................... 8-2 Full-Time Employees .............................................................................. 8-3

NORMAL SYSTEM OPERATION ..................................................................... 8-3 Routine and Preventative Maintenance Criteria ..................................... 8-4 Lift Station and Generator Maintenance ................................................. 8-5 Force Mains ............................................................................................ 8-9 Gravity Sewers and Manholes ................................................................ 8-9 Pipeline Cleaning .................................................................................... 8-9 Hydraulic Cleaning ................................................................................. 8-9 Mechanical Cleaning ............................................................................ 8-10 Chemical Cleaning ............................................................................... 8-10 Video Inspection ................................................................................... 8-10 Cleaning and Inspection Standards ...................................................... 8-11 Developer Extension Administration ..................................................... 8-12 Current Staffing Needs ......................................................................... 8-12 Future Staffing Needs ........................................................................... 8-13 Capacity Management Operation And Maintenance (CMOM) and Future Staffing Needs ........................................................................... 8-13 Capacity Management Operation and Maintenance (CMOM) ... 8-13

CAPACITY MANAGEMENT OPERATION AND MAINTENANCE (CMOM) DRAFT REQUIREMENTS .............................................................................. 8-14 SAFETY .......................................................................................................... 8-16

Confined Spaces .................................................................................. 8-16 Electrical and Mechanical Equipment ................................................... 8-17 Fire Hazards ......................................................................................... 8-17 Health/Safety ........................................................................................ 8-17

EMERGENCY RESPONSE ............................................................................ 8-18 MAINTENANCE PERSONNEL QUALIFICATIONS ........................................ 8-20

Sanitary Sewer Comprehensive Plan vi October, 2016 Lake Stevens Sewer District CHS Engineers, LLC

CHAPTER 9 – FINANCIAL ANALYSIS INTRODUCTION ............................................................................................... 9-1 HISTORICAL FINANCIAL PERFORMANCE .................................................... 9-1 CURRENT RATES and CHARGES .................................................................. 9-4 CUSTOMER GROWTH .................................................................................... 9-4 BUDGET FORECAST ....................................................................................... 9-4

OPERATING REVENUES and EXPENSES........................................... 9-5 Operating Revenues .................................................................... 9-5 Operating Expenses .................................................................... 9-5 Debt Service ................................................................................ 9-6 Summary of Projected Operating Revenues and Expenses ........ 9-6

GENERAL FACILITIES CHARGES ........................................................ 9-6 Existing Cost Basis ...................................................................... 9-7

Future Cost Basis ........................................................................ 9-7 Customer Base ............................................................................ 9-7 GFC Calculation .......................................................................... 9-8

CAPITAL REVENUES AND EXPENSES ............................................... 9-8 Capital Expenses ......................................................................... 9-8 Capital Revenues ........................................................................ 9-9

PROJECTED TOTAL CASH FLOWS ..................................................... 9-9 AFFORDABILITY EVALUATION..................................................................... 9-12 SUMMARY AND RECOMMENDATIONS ....................................................... 9-13 CHAPTER 10 – DEVELOPER PROJECT STANDARDS INTRODUCTION ............................................................................................. 10-1 GENERAL DEVELOPER EXTENSION PROCESS ........................................ 10-1 SEWER SYSTEM EXTENSION DESIGN ....................................................... 10-3

SEWER LIFT STATION DESIGN.................................................................... 10-5 REFERENCES TABLES Table No. Page TABLE S-1 Projected UGA Population to Year 2035 ........................................ S-6

TABLE S-2 Projected ERUs to Year 2035 ........................................................ S-7

TABLE S-3 WWTF Influent Flows (2012-2014) ................................................. S-8 TABLE S-4 Capital Improvement Project Summary ........................................ S-14

TABLE 1-1 District Projects Completed Since 2007 Plan ................................. 1-3 TABLE 2-1 Service and Study Areas ............................................................... 2-3 TABLE 2-2 Precipitation, 1997-2014 ................................................................ 2-4 TABLE 3-1 City of Lake Stevens Land Use and Zoning Designations ............. 3-3

Sanitary Sewer Comprehensive Plan vii October, 2016 Lake Stevens Sewer District CHS Engineers, LLC

TABLE 3-2 Snohomish County Land Use and Zoning Categories ................... 3-6 TABLE 3-3 UGA and Study Area Zoning District Acreage ............................... 3-7 TABLE 3-4 Lake Stevens UGA Historical and Predicted Population ................ 3-9 TABLE 3-5 UGA Population Based on Residential Service Connections....... 3-11 TABLE 3-6 School Staff and Student Population - 2014 ................................ 3-12 TABLE 3-7 Projected UGA Population to Year 2035...................................... 3-13 TABLE 3-8 Projected ERUs to Year 2035 ...................................................... 3-15

TABLE 4-1 Recent WWTP Influent Flows(1) (2012-2014) ................................. 4-6 TABLE 4-2 Summary of Discharge Monitoring Reports (DMRs) WWTP Influent and Effluent Monthly Averages ............................................................. 4-7 TABLE 4-3 WWTF Flow and Loading Summary(1) ........................................... 4-9 TABLE 4-4 Winter Water Use for Commercial Customers ............................. 4-11 TABLE 4-5 Estimated Infiltration and Inflow ................................................... 4-14 TABLE 4-6 Per Capita Infiltration and Inflow Based on EPA Criteria ............. 4-15 TABLE 4-7 Current and Projected Future Wastewater ERUs and Flows ....... 4-17 TABLE 4-8 Current and Projected WWTF Loadings ...................................... 4-19 TABLE 4-9 Wastewater Design Criteria ......................................................... 4-20 TABLE 5-1 Gravity Sewer Inventory............................................................... 5-20 TABLE 5-2 Inventory of Sewage Lift Stations and Force Mains ..................... 5-21 TABLE 5-3 WWTF Influent Limits and Upgrade Thresholds .......................... 5-23 TABLE 6-1 Collection System Information ....................................................... 6-2 TABLE 6-2 Peaking Factors ............................................................................. 6-3 TABLE 6-3 Pipe Capacity Deficiencies ............................................................ 6-6 TABLE 6-4 Local Lift Station Summary .......................................................... 6-10 TABLE 6-5 Main Lift Station Capacity Analysis .............................................. 6-11 TABLE 6-6 Force Main Capactiy Evaluation .................................................. 6-12

TABLE 7-1 Capital Improvement Project Summary ......................................... 7-4

TABLE 8-1 2016 Personnel Certification .......................................................... 8-2 TABLE 8-2 Preventative Maintenance Schedule ............................................. 8-5 TABLE 8-3 Lift Station Maintenance Schedule ................................................ 8-7 TABLE 8-4 Lift Station Inspection and Maintenance Staffing Recommendations ............................................................................................ 8-8 TABLE 8-5 Staffing Requirements for Inspection and Cleaning ..................... 8-12 TABLE 8-6 Emergency Response Actions for Lift Stations ............................ 8-18 TABLE 8-7 Emergency Response Actions for Force Mains ........................... 8-19 TABLE 8-8 Emergency Response Actions for Gravity Sewer ........................ 8-19

Sanitary Sewer Comprehensive Plan viii October, 2016 Lake Stevens Sewer District CHS Engineers, LLC

TABLE 9-1 Summary of Historical Fund Resources and Uses Arising From Cash Transactions ...................................................................................................... 9-1 TABLE 9-2 Summary of Historical Comparative Statements of Net Position ... 9-2 TABLE 9-3 Current Monthly Rate and GFC ..................................................... 9-4 TABLE 9-4 Operating Revenue Forecast ......................................................... 9-5 TABLE 9-5 Projected Annual Debt Expense Less ULID Assessment Revenue9-6 TABLE 9-6 Projected Operating Revenue and Expenses with Existing Rates . 9-6 TABLE 9-7 Updated Sewer GFC Calculation ................................................... 9-8 TABLE 9-8 Projected Capital Expenses ........................................................... 9-9 TABLE 9-9 Projected Capital Funding Strategy ............................................... 9-9 TABLE 9-10 Projected Cash Flows and Reserves (At Existing Rates) ........... 9-10

TABLE 9-11 Projected Cash Flows and Reserves With Rate Adjustments..... 9-11

TABLE 9-12 Summary of Alternative Growth Scenarios ................................. 9-12

TABLE 9-13 Affordability Evaluation ............................................................... 9-12 FIGURES Figure No. (all figures are at the end of each chapter) S-1 Service & Study Area S-2 Land Use S-3 Monthly Average and Peak Day WWTF Influent Flow S-4 Monthly Average Effluent CBOD (Concentration) S-5 Capital Improvement Projects 1-1 Location Map 2-1 Service & Study Area 2-2 Topography 2-3 Critical Areas 2-4 Onsite Sewage Disposal Systems 3-1 Land Use 3-2 Zoning 4-1 Monthly Average and Peak Day WWTF Influent Flow 4-2 Monthly Average Influent BOD & TSS 4-3 Monthly Average Effluent CBOD (Concentration) 4-4 Monthly Average Effluent CBOD (Mass) 5-1 Existing Sewer System 5-2 Existing Lift Stations & Sewer Trunks 5-3 Lift Station System Schematic 5-4 Lift Station & Trunk Basins Sewer Location System Details:

Sanitary Sewer Comprehensive Plan ix October, 2016 Lake Stevens Sewer District CHS Engineers, LLC

A – Vernon Road West B – 91st Avenue/Meridian Crossing C – LS #2 to LS #12 D – LS #14 E – 20th Street SE/107th Drive Area F – LS #5 to LS #15 G – Vernon Road/Lundeen Parkway Trunk H – LS 1C I – 26th Street NE to LS 8C J – LS 7C 6-1 Modeled Existing Sewer System 6-2 Sewer Sub-Basins 7-1 Capital Improvement Projects 8-1 Organizational Chart (In Pocket) Existing Sewer System

APPENDICES A – Approvals B – SEPA Review C – Moratoria Resolution D – WWTF NPDES Waste Discharge Permit E – Hydraulic Model F – Cost Estimates G – Lift Station Condition Assessment

Sanitary Sewer Comprehensive Plan x October, 2016 Lake Stevens Sewer District CHS Engineers, LLC

ACRONYMS

AAF Average Annual Flow ADWF Average Dry Weather Flow BLR Buildable Lands Report BOD Biochemical Oxygen Demand CIAC contributions in aid of construction CIP Capital Improvement Plan CMOM Capacity Management Operation and Maintenance DEA developer extension agreements DMR daily monitoring reports DOE State Department of Ecology ERU equivalent residential units FEMA Federal Emergency Management Agency FOG fats, oil and grease fps feet per second FTE full-time employee GFC general facility charge GIS geographical information systems GMA Growth Management Act GMR Growth Monitoring Report gpd gallons per day gpm gallons per minute HMI human machine interface I/I infiltration and inflow ILA Interlocal Agreement LFC local facility charge L&I State Department of Labor and Industries MBR membrane bioreactor MDF Maximum Day Flow OI operator interface O&M operation and maintenance PHF peak hour flow PLC programmable logic controller PSCAA Puget Sound Clean Air Agency PUD Snohomish County Public Utility District No. 1 PVC Polyvinyl Chloride

Sanitary Sewer Comprehensive Plan xi October, 2016 Lake Stevens Sewer District CHS Engineers, LLC

ACROYNMS (Cont.) RCW Revised Code of Washington RTU remote telemetry unit RUTA rural-urban transition areas SCADA supervisory control and data acquisition SCP Sanitary Sewer Comprehensive Plan SCT Snohomish County Tomorrow SEPA State Environmental Policy Act TESC temporary erosion and sedimentation control TMDL Total Maximum Daily Load UGA urban growth area ULID utility local improvement district UV ultraviolet VFD variable frequency drive WAC Washington Administrative Code WFP wastewater facilities plan WWTF wastewater treatment facility

WWTP wastewater treatment plant

SUM

MA

RY

AN

D R

ECO

MM

END

ATI

ON

S

Sanitary Sewer Comprehensive Plan S-1 October, 2016 Lake Stevens Sewer District CHS Engineers, LLC

Lake Stevens Sewer District Sanitary Sewer Comprehensive Plan

SUMMARY AND RECOMMENDATIONS

BACKGROUND This 2016 Sanitary Sewer Comprehensive Plan for the Lake Stevens Sewer District presents the comprehensive planning needs for wastewater collection, transmission, treatment and discharge for the planning period 2016 through 2035. The Plan has been prepared to meet the requirements of the Washington Administrative Code Section 173-240-050, General Sewer Plan, and Revised Code of Washington Chapter 57.16, Comprehensive Plan. This Plan updates and replaces the District’s 2007 Sanitary Sewer Comprehensive Plan, and Amendment No. 1 to that plan (2010). The Plan has been prepared to be consistent with the Snohomish County Comprehensive Plan, including Appendix D as adopted in July, 2015, and to be consistent with the City of Lake Stevens Comprehensive Plan, September, 2015. The Lake Stevens community is located in central Snohomish County, around the namesake water body, Lake Stevens. Adjacent communities include Marysville immediately north, Everett to the west and Snohomish to the south. The Lake Stevens Sewer District was formed in 1957 in response to bacterial contamination and algal blooms in Lake Stevens. The District’s first treatment facility began operation in 1965, with expansions in 1971 and 1986. The District completed construction of a replacement wastewater treatment facility (WWTF) in 2012. The City of Lake Stevens operated a separate sewer collection and conveyance system, with treatment by the District, from the late 1960s until 2005. At that time, the District and City entered into a long-term unification agreement. Per the agreement, the City transferred its sewer assets to the District to own, operate and maintain, for a period of at least twenty years following completion of the new WWTF. The City and District have shared responsibilities for cooperation for sewer system planning and related matters. This is manifest in the action of a joint Utility Committee consisting of three District commissioners and three City council members. SEWER SERVICE AREA AND ADDITIONAL STUDY AREA The sewer service area is essentially the same as considered in the 2007 Plan and consists primarily of the area designated by Snohomish County as the Lake Stevens Urban Growth Area (UGA). The service area is about 10.9 square miles (not including the area of Lake Stevens) and includes about 10 acres in the Marysville UGA and a plat above Sunnyside Blvd which is immediately outside the UGA, but previously developed with a District sewer collection system. Under this Comprehensive Plan update, the


District did not perform a detailed evaluation of likely land-use scenarios, growth patterns and necessary projects within the RUTA; however, this work may be necessary based on the City of Lake Steven’s expressed desire to propose adding land to the current UGA during the horizon of this Plan. The County has designated land around the north, east and south limits of the UGA as rural-urban transition areas (RUTAs). These are areas where urban develop may be encouraged to occur with future expansion of the UGA, with future County and City comprehensive and land use plan updates. Most of the RUTA area has been designated as Additional Study Area for this Plan, to support an early estimate of the magnitude of potential future growth of the District’s sewer service area. The City has incorporated most of the UGA, with the main unincorporated areas remaining along the eastern margin, particularly south and east of the Lake. The District’s legal boundary is somewhat larger than the City’s incorporated area, with some UGA outside the District south and east of the Lake. The District Boundary also includes the former wastewater treatment plant and adjacent area west of the UGA. Figure S-1 presents a summary of these areas and limits. The topography varies considerably throughout the service area, with the highest ground elevation over 460 feet, Lake elevation about 200 feet and WWTF located at about elevation 80 feet. Principal water bodies in the service area are Lake Stevens, Stitch Lake and Catherine Creek. Water service for the community is provided by the Snohomish County Public Utility District No. 1. The County and City provide roads and stormwater systems in their respective jurisdictions. There are an estimated 1,700 to 1,800 properties served by septic tank and drain field systems in the service area. POPULATION AND GROWTH Land use for the sewer service area is governed by Snohomish County and the City of Lake Stevens. The County is responsible for coordinating and developing county-wide planning policies and efforts, including designation of UGAs consistent with the provisions of the State Growth Management Act, and land use planning for unincorporated areas, including those within UGAs. The City is responsible to coordinate with the County and develop a comprehensive plan and land use regulations consistent with the County and their growth forecasts for the UGA. The planning period for this Plan is 2016 through 2035, consistent with the current City and County comprehensive plans. A foundation for these plans, and this Plan, is the County’s 2012 Buildable Lands Report (BLR) and the 2013-2014 Growth Monitoring Report (GMR), prepared by Snohomish County Tomorrow (a coordinated planning association). The BLR presents the results of detailed analysis, at the parcel level, documenting the estimated land development capacity within the UGA. Capacity is


estimated by considering land use, current development, critical areas, zoning and density requirements, and associated potential for development, redevelopment and infill. The GMR evaluates recent growth trends and develops recommended targets for population and employment in the UGA, through the planning period for the County and City plans. The County’s consideration of the BLR and GMR supported their adoption of an updated Appendix D to the County Plan, effective July 2015. That process resulted in no changes to the UGA area and adopted year 2035 targets for the UGA of 46,380 persons, 17,311 housing units and 7,821 jobs. The City and County have each adopted land use designations and established zoning districts in their respective jurisdictions in the UGA. Each includes a range of single family, multi-family, mixed use, commercial, industrial and public uses, with unique gross residential development density. Figure S-2 depicts the land use designations for the service area. The County reports an estimated Lake Stevens UGA population of 34,477 persons as of 2014. The County growth targets anticipate about 2.6 to 2.9 persons per household. This Plan adopts a service area wide average household size of 2.70 persons. The District served 11,026 equivalent residential units (ERUs) in the UGA in 2014, which corresponds to an estimated residential sewer service population of about 29,823 persons. The County predicts a straight-line population growth of approximately 567 persons per year from 2014 to 2035 to reach their adopted population target. This plan assumes that, as development and infill occurs, about one-half of the parcels served by on-site sewage disposal systems will connect to the sewer system by year 2035. This translates to a forecast of about 252 additional residential ERUs each year, based on the County population target. The forecast of residential ERU growth relative to served population and the UGA target is summarized in Table S-1. The District served 854 commercial ERUs in 2014 (annual average), 728 average commercial ERUs in 2015, and 104 ERUs of schools service. To achieve the County targeted count of jobs, this Plan estimates that commercial ERUs will increase at the rate of three percent annually. Table S-2 presents the total ERU growth forecast for the planning period. A School District construction bond measure was passed by voters in early 2016 and the Library District recently entered into a partnership with the City of Lake Stevens to create a civic center, necessitating its own bond measure in 2017. These factors may precipitate the District’s need to amend growth assumptions for commercial and public facility customers by 2020.

LegendCITY OF LAKESTEVENSSERVICE AREAADDITIONAL STUDYAREALAKE STEVENS UGABOUNDARYDISTRICTBOUNDARYRURAL URBANTRANSITION AREAMARYSVILLE UGA

RUTA

SERVICE AREA

ADDITIONAL STUDY AREA

RUTA

RUTA

Lake Stevens Sewer District2016 Sanitary Sewer Comprehensive Plan

S-1SERVICE & STUDY AREA

NTS£


FORMERWWTP

SUNNYSIDEWWTP

SR 92

SR 204

SR 9

SR 2

Ebey Slough

Pilchuck River

L a k e S t e v e n s

S t i t c h L a k e

L a k e C o n n e r

CITY

RR/5

RCF

CITY

RR/5B

ASIC

RR/5B

ASIC

CITY

LAKE

ULDR

RCF

RR/5B

ASIC

RR/5B

ASIC

RR/5

ROW

ULDR

RR/5B

ASIC

RR/5B

ASIC

ULDR

UI

RCF

ULDR

ULDR

UI

RR/5B

ASIC

ULDR

ULDR

RCF

ULDR

UMDR

RCF

CITY

P/I

ULDR

RI

UCOM

ULDR

ULDR

RI

ULDR

CITY

UMDR

UCOM

UMDR

CITY

RR/5B

ASIC

ULDR

ULDR

RR/5B

ASIC

UCOM

RR/5B

ASIC

UMDR

ULDR

ROW

ULDR

MDR

MDR

MDR

GI

MDR

MDR

MDR

HDR

MDR

COM

MDR

WR

WR

LI

MDR

MDR

MDR

MDR

MDR

MDR

WR

P/SP

MFR

HDR

MFDA

COM

MDR

COM

MDR

MDR

MFR

COM

PBD

P/SP

MDR

LC

P/SP

WR

COM

P/SP

COM

MU

MU

P/SP

MDR

P/SP

HDR

PBD

HDR

MDR

P/SP

MDR

HDR

MDR

MUMDR

P/SP

MU

P/SP

MU

COM

P/SP

P/SP

P/SP

HDR

MU

LC

P/SP

P/SP

MFR

MDR

P/SP

LC

P/SP

PBD

WR

P/SP

P/SP

MFR

MFR

COM

MDR

MDR

MU

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TABLE S-1 Projected UGA Population to Year 2035

Year Population Served(1)

Population Unserved

Residential ERUs(2)

UGA Population(3)

2014 29,823 4,654 11,026 34,477 2015 30,451 4,593 11,278 35,044 2016 31,131 4,480 11,530 35,611 2017 31,811 4,366 11,782 36,177 2018 32,492 4,252 12,034 36,744 2019 33,172 4,139 12,286 37,311 2020 33,853 4,025 12,538 37,878 2021 34,533 3,912 12,790 38,445 2022 35,213 3,798 13,042 39,011 2023 35,894 3,684 13,294 39,578 2024 36,574 3,571 13,546 40,145 2025 37,255 3,457 13,798 40,712 2026 37,935 3,344 14,050 41,279 2027 38,615 3,230 14,302 41,846 2028 39,296 3,117 14,554 42,412 2029 39,976 3,003 14,806 42,979 2030 40,657 2,889 15,058 43,546 2031 41,337 2,776 15,310 44,113 2032 42,017 2,662 15,562 44,680 2033 42,698 2,549 15,814 45,246 2034 43,378 2,435 16,066 45,813 2035 44,059 2,321 16,318 46,380

(1) Current ERUs used to calculate population for 2014 in UGA (excludes 80 ERUs in Valterra and 28 in Ridgewood Park, both outside the UGA).

(2) Begin conversion of unserved customers to sewer service in 2015 at about 48 ERUs (rounded) per year. Excludes 108 ERUs outside of UGA.

(3) County growth rate of 567 (rounded) persons/year used to calculate UGA population from 2015-2035.

(4) All population and ERUs count assumed at end of year, all within UGA.

(5) Assume all population growth will be served by sewer. (6) Some ERU totals are high or low by one ERU due to fraction

in annual population increase.


TABLE S-2

Projected ERUs to Year 2035

Year Residential ERUs(1)

Commercial ERUs(2) Total ERUs

2014 11,134 854 11,988 2015 11,386 880 12,266 2016 11,638 906 12,544 2017 11,890 933 12,823 2018 12,142 961 13,103 2019 12,394 990 13,384 2020 12,646 1,020 13,666 2021 12,898 1,050 13,948 2022 13,150 1,082 14,232 2023 13,402 1,114 14,516 2024 13,654 1,148 14,802 2025 13,906 1,182 15,088 2026 14,158 1,218 15,376 2027 14,410 1,254 15,664 2028 14,662 1,292 15,954 2029 14,914 1,331 16,245 2030 15,166 1,370 16,536 2031 15,418 1,412 16,830 2032 15,670 1,454 17,124 2033 15,922 1,497 17,419 2034 16,174 1,542 17,716 2035 16,426 1,589 18,015

(1) Residential ERU counts for 2014 are December values. See Table 3-7 for residential ERU projections. Values here include Valterra and Ridgewood Park connections outside the UGA. (+108 ERUs)

(2) Commercial counts for 2014 are annual average. Commercial includes schools. Commercial growth is anticipated to increase at 3.0% annually.

(3) Some ERU totals are high or low by one ERU due to fraction in annual population increase.

Alternative growth scenarios are presented in the financial analysis summary below.


The Additional Study Area (RUTAs) includes over 5,400 acres of land presently designated as Rural, with most of that area zoned as R-5. Neither the City nor County have designated future development density for this area. This plan assumes a future gross development density of about 2.6 units per acre (about five percent higher than the current UGA) to estimate the potential future population of the Additional Study Area. These factors suggest a potential future population of about 38,000 persons. DESIGN CRITERIA The wastewater system must have hydraulic capacity to handle all flows anticipated in each segment of the system (gravity and pressure pipes, lift stations and each process in the wastewater treatment facility) and each treatment process must have capacity to adequately treat the anticipated solids and biological constituents in the wastewater. Hydraulic flow originates as the liquid waste stream from connected properties. The District system is a “separated” sewer system wherein it is not designed to receive and handle runoff from precipitation events. Nonetheless, gaps, leaks, defects or inappropriate connections allow groundwater (infiltration) or surface runoff (inflow) into the system. Collectively this additional flow is referred to as “I and I” or simply I/I”. Wastewater flow and loading criteria are reviewed and updated in the 2016 Plan. Flow data for years 2012-2014 is evaluated to understand how flow varies seasonally, monthly, daily and hourly. The data considered includes the final four months of operation of the former WWTP and the first 32 months of operation of the new WWTF. System flow data is summarized in Table S-3.

TABLE S-3 WWTF Influent Flows (2012-2014)

Flow Flow Rate (mgd)

Average Dry Weather Flow(2) 1.96 Annual Average Flow 2.50 Maximum Month Flow(3) 3.61 Peak Day Flow(4) 5.90 Highest Measured Peak Hour Flow(5) 7.68 (1) Based on DMRs reporting WWTP influent (2) Average of July, August, September, 2014 (3) Reported for December, 2012 (4) Reported for January 29, 2013 (5) Actual highest PHF measured - November 19, 2012 (actual peak factor is approximately 3.07`) (7) Ratios:

Max. Month : Annual Average 1.45:1 Peak Day : Annual Average 2.36:1


Figure S-3 depicts monthly average and peak day influent flows at the WWTF for years 2012-2014. Figure S-4 clearly indicates the improvement in discharge effluent quality from the former WWTP (first four data points) and the new WWTF.

0.00

1.00

2.00

3.00

4.00

5.00

6.00

Jan-12 May-12 Sep-12 Jan-13 May-13 Sep-13 Jan-14 May-14 Sep-14

Flo

w (

MG

D)

Figure S-3 Monthly Average and Peak Day WWTF Influent

Flow

Monthly Average Influent Flow

Peak Day Influent Flow

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

Jan-12 May-12 Sep-12 Jan-13 May-13 Sep-13 Jan-14 May-14 Sep-14

Effl

ue

nt

CB

OD

(m

g/l)

Figure S-4 Monthly Average Effluent CBOD (Concentration)

Effluent CBOD (Concentration)


Loading data for biological oxygen demand (BOD5) and total suspended solids (TSS) were evaluated for the same period. The maximum month BOD5 load averaged 0.245 pounds per person per day and TSS maximum month load averaged 0.195 pounds per person per day. Summer and winter flows and commercial water use data was evaluated to estimate the average sanitary flow contribution per person. The estimated discharge was just over 67 gallons per person per day. This Plan continues to use an average of 70 gallons per person per day, as did the 2007 Plan. Summer time low hourly flow records were evaluated to estimate an annual average Base Flow for sanitary discharge to the system. The result is 1.84 million gallons per day (mgd). Comparison of that flow to annual average daily flow, maximum month average daily flow, peak day and peak hour flows at the WWTP reveals estimated amounts of I/I entering the system, for each flow scenario. The amount of I/I in a system is typically expressed a an amount relative to some parameter such as service area acres or miles of pipe adjusted for diameter. For consideration of I/I for the present system and for forecasting I/I for a future, yet to be defined system, the parameter should be readily determined from one point in time to another. This Plan relies on the District billing records data to identify which parcels are presently being served. The combined area of those parcels can be used as the common parameter for expression of the amount of I/I in the system. Parcel area served at full development of the UGA can be reasonably predicted to forecast future I/I associated with an expanded collection system. The current estimated service area is 2,709 acres of served parcels. Using the data from the County BLR, with an adjustment for future land dedications for streets, parks and stomwater systems, the future anticipated service area is approximately 4,060 acres of served parcels. Both estimates ignore the area immediately adjacent to the sewer mains along the road rights of way, but both are estimated on the same basis. The estimated peak hour I/I rate is 2,156 gallons per acre per day. As the collection system continues to age and expand, this value is forecast to increase by 15% over the planning period, to a year 2035 criteria of 2,479 gallons per acre per day. The U.S. Environmental Protection Agency (EPA) prepared a manual many years ago entitled I/I Analysis and Project Certification. This manual presents threshold criteria for excessive inflow and infiltration. Data analysis for this Plan concludes that the estimated District values are about 65 to 70% of the EPA thresholds. The District’s system appears to be subject to low I/I rates, relative to many other jurisdictions with collection system of the same age in the Puget Sound region. However, prudent planning suggests and the WWTF permit requires that I/I rates be regularly monitored and evaluated, to ensure that I/I is not resulting in excessive flows in the collection system and unnecessarily high flows at the treatment facility.


SEWER SYSTEM – EXISTING SYSTEM The District’s sewer system includes the following facilities:

Membrane bioreactor based WWTF 29 lift stations with force mains ranging from 2-inch to 19.4-inch diameter Collection system including over 112 miles of pipe from 6-inch collectors to 36-

inch interceptors. The collection system includes several trunk and interceptor lines, with lift stations sited as needed for pumped conveyance from local low areas in the service area. Lift stations range in capacity from 30 gpm to 5,250 gpm. Seventeen of the lift stations were constructed over 30 years ago, with little to no upgrade attention, other than work immediately necessary to keep them in service, or infrequent replacement of pumps and motors. In support of this Plan, a Lift Station Condition Assessment was completed. This Assessment included preparation of a general inventory of features and elements of each station, based on site visits to select stations and discussions with the collection system superintendent Improvements were identified for each station and budgetary cost estimates have been prepared. The recommended improvements are independent of upgrades necessary for adequate peak flow capacity. A suggested priority and schedule of condition upgrades is presented, for integration in the Capital Improvement Plan summarized below. The Lift Station Condition Assessment included consideration of the existing lift station supervisory control and data acquisition (SCADA) or telemetry system. The existing system consists of three separate systems, two of which are antiquated technology. The Plan recommends a phased conversion to a web-based telemetry system hosted by a third-party vendor. Communication uses a cellular data network and operators can access the system from the office or mobile devices with internet access. Construction of the new WWTF was completed in 2012. It includes a headworks facility with flow measurement and screening, primary clarifiers with grit removal capability, additional effluent screening, aeration basins with anoxic and aerobic zones, membrane bioreactor basins and ultraviolet disinfection. Solids generated in the treatment process are thickened and treated to Class B biosolids standards, then dewatered and hauled to a permitted utilization site for land application. The peak day and peak hour design flows are 7.15 and 11.53 mgd, respectively. The facility is permitted to treat a maximum month average daily flow of 5.01 mgd. The anticipated growth in ERUs and corresponding increase in sanitary and I/I flows and loadings have been forecast over time and compared to the permitted capacity of the WWTF. Based on the growth forecast discussed above, the WWTF will need additional maximum month average daily flow capacity by year 2025. Flow and loading capacity is forecast to be adequate through year 2029.


The City’s economic development program emphasizes increasing the footprint of both industrial and commercial business within the UGA. The District will need to more closely monitor loading factors at the WWTF if Lake Stevens becomes less of a typical “bedroom community”. As such, it will become increasingly important for the District to create a quality pre-treatment program and a FOG (fats-oils-grease) monitoring system. The existing WWTP is being decommissioned in phases. The District has initiated a project to remove much of the accumulated biosolids in the existing lagoon system. A future project will address final vacation of the site. In August 2016, the District completed removal of 80% of the accumulated biosolids in the existing lagoon system. A future project will address the final decommissioning and disposition of the site. SEWER SYSTEM – COLLECTION SYSTEM ANALYSIS The Plan includes analysis, by hydraulic modeling, of the sewer collection system, including consideration of capacity of the existing lift stations and their discharge pressure mains or force mains. The analysis considered nearly 30 percent of the collection system. The remainder of the system serves areas that have relatively low flow contribution. The system was analyzed under two scenarios – Existing Conditions and UGA or Buildout Conditions. The first scenario evaluates the capacity of the system with respect to anticipated sanitary flows from existing customers and current estimated amounts of inflow and infiltration. The second scenario evaluates the capacity of the system as anticipated in year 2035, with the growth in population and commercial development, and I/I contributions as developed in this Plan. The Existing Conditions analysis reveals that 75 pipe segments representing about three percent of the entire collection system are anticipated to be over capacity under the modeled conditions. Based on prior analysis by the District, two sewer connection moratoria remain in place. One is the Lift Station #7 (LS7) Moratorium, on the east side of the Lake. Additional service in this area is limited by the capacity of LS7, which is in-turn limited by downstream facilities. The other is the Stitch Road Moratorium at the south end of the Lake. Projects to address each capacity limitation are included in the projects recommended in this Plan. Where improvements are recommended to address deficiencies identified in the Existing Conditions analysis, those solutions are anticipated to be in place as part of the system considered in the Buildout Conditions analysis. The Buildout Conditions analysis reveals that 55 pipe segments representing less than two percent of the entire collection system are anticipated to be over capacity under the future modeled conditions.


Most of the capacity deficiencies result in only local sewer main surcharging conditions and no action is recommended at this time. Several areas of concern can and will be addressed by previously or presently planned system improvements that will reroute flows to other parts of the system with capacity. In other cases projects are recommended to increase gravity pipe capacity to meet existing and future needs. Project-specific recommendations are included in the Capital Improvement Plan summary below. CAPITAL IMPROVEMENT PLAN The Plan presents a recommended list and schedule of system improvements. The project list is intended to address the substantive project and system needs anticipated over the 20-year planning period of the Plan, and as necessary to serve growth as anticipated by the County and City within the UGA, under present land use and development regulations. The Plan should be reviewed and updated as new information becomes available. The Plan includes projects throughout the 20-year planning period. Table S-4 represents a portion of the capital improvement plan, listing only those projects scheduled for completion over the next ten years. The projects for which District funding has been designated are the projects that make up the future project component of the General Facilities Charge calculation (see discussion below). Future recommended projects are presented on Figure S-5. OPERATIONS AND MAINTENANCE The District is governed by a three member Board of Commissioners, elected from and by the voters residing in the District boundary. The Board leads the District with the authority of and in compliance with RCW 57 regarding special purpose water and sewer districts. Daily operations are lead by a general manager who in turn is supported by managers of the administrative, treatment and collection systems of the District. A total of 23 full time positions are maintained by the District. Personnel are certified as required by the State Department of Ecology as appropriate to their job classification and duties. The Plan addresses a general outline of regular sewer system administration and maintenance activities. The District has relied on contractors for some services such as sewer main cleaning and video inspection but is in the process of acquiring equipment and training to complete such work with current staff. FINANCIAL ANALYSIS The Plan summarizes the general financial condition of the District, includes its recent and forecast annual operation and maintenance costs, cash and investments, debt, debt service and debt service coverage requirements and the capital improvement plan presented in the Plan. The analysis concludes with a forecast of anticipated monthly


service charges and a recommended General Facilities Charge. The General Facilities charge can be considered for adoption once this Plan is adopted by the District. The service charges can be reviewed and updated at the Board’s discretion.

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Baseline – this is the forecast based on the County’s target population and jobs figures for year 2035. As described above, these figures result in an annual average growth rate of 287 ERUs through 2035

Alternative A – Constrained Growth – this is a District forecast targeted at an annual average growth rate of 160 ERUs through 2035. This is based on the general trend in District growth since about 2010.

Alternative B – Low Growth – this is a District forecast targeted at a potential slow growth at an annual average rate of 120 ERU/year through 2035.

For the two alternative growth forecasts, a few projects were deferred as they are directly related to need for increased capacity as a result of District-funded projects. Most notable is the future expansion of the WWTF. This is anticipated as early as year 2025 in the Baseline forecast and as late as 2038 per the Low Growth forecast. Under State law, the District can adopt a connection charge representing a pro-rata share of the cost of the system. This charge, the General Facilities Charge or GFC, is based on the actual cost of the system, less donated facilities, plus up to ten years of market rate interest on the existing eligible facilities, plus the cost of up to ten years of anticipated improvements. The recommended GFC is $9,000 per ERU. The financial analysis supports a charge as high as $9,117. Monthly sewer service charges are calculated as follows, per the three growth forecasts: Forecast 2016 2017 2018 2019 2020 2021 Baseline $83.00 $85.00 $87.00 $89.00 $91.00 $93.00 Constrained $83.00 $86.00 $88.50 $91.00 $93.50 $96.00 Low $83.00 $87.00 $90.50 $93.50 $96.50 $99.00 Actual monthly charges will be determined by the Board as part of the District’s annual financial review process. DEVELOPER PROJECT STANDARDS The District drafted standards in 2009 for completion of sewer system extensions, including lift stations and force mains, by property owners and developers. These draft standards are scheduled for review and update in 2017. The Plan summarizes the general process for completion of a developer extension, including the application, agreement, plan review, inspection, documentation and conveyance requirements. Design criteria is also summarized for gravity mains and lift stations.


RECOMMENDATIONS Recommendations that follow from completion of this Plan are as follows:

Adopt an increased general facilities charge (GFC) per the analysis summarized in Chapter 9. Incorporate in the GFC methodology including regional latecomer basins if possible.

Annually review and update the general facilities charge. Evaluate basis for determination of equivalent residential units for customers and

land uses other than single-family residential and consider refinement of policy and related financial impacts (i.e. commercial GFC calculation method).

Continue past practice of annual review of operation and maintenance and capital budgets, including debt service, and actual and anticipated growth in customers, and evaluate adequacy of forecast rate and general facilities charge revenue, and need for rate increases.

Determine the costs and revenues necessary to implement a District pre-treatment and FOG program along with associated permitting policy and procedures.

Continue coordination with the City of Lake Stevens with respect to integration of land use and utility planning, and for coordinated integration of agency capital improvement plans.

Complete development of and implement an ongoing asset evaluation program to collect data on the condition of the existing collection system, to support future planning for collection system repairs, upgrades and replacements, in the context of monitoring and managing inflow and infiltration and proactive asset management of the collection system.

Implement the projects as identified for District funding per the Capital Improvement Plan, with focus on those necessary to remove existing moratoria determinations.

In response to development and growth patterns, and per District Developer Standards and developer extension agreement policies, implement the projects as identified.

Periodically evaluate staff needs with respect to increase in assets, customers and service area extent and add staff as determined appropriate.

Complete a WWTF capacity rating analysis by year 2020 (anticipated to be part-way through the next NPDES permit period) to determine if existing facility will adequately handle and treat flows greater than presently permitted.

Complete an update of the District Developer Standards, including developer extension agreement policies, standard forms, construction specifications and standard details.

Amend or update the Plan in response to substantive changes to land use designations and/or zoning by Snohomish County or the City of Lake Stevens. The City of Lake Stevens is considering several alternative property annexations within the UGA in late 2016 and 2017. Depending on the impact on land use plans in those annexation areas, the District may need to amend of update the Plan.


Amend or update the Plan in response to changes to the area designated by Snohomish County as the Lake Stevens Urban Growth Area. Should the UGA need to be expanded into part of the RUTA by 2024, amend or update the Plan.

Amend or update the Plan and the capital improvement program, and the general facilities charge calculation, following property annexations which include or result in land use changes, and following UGA expansion.

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System-Wide Projects - Thru 2025 - Misc. Annual Program - Vactor/Clean/TV Equipment - LS Monitoring System - Lift Stations Rehabilitation - Comp. Plan Update - WWTF Eng. Report Update

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Sanitary Sewer Comprehensive Plan 1-1 October, 2016 Lake Stevens Sewer District CHS Engineers, LLC

CHAPTER 1

INTRODUCTION GENERAL This 2016 Sanitary Sewer Comprehensive Plan for the Lake Stevens Sewer District is a general update to the 2007 Plan, and addresses the District’s comprehensive planning needs for wastewater collection, transmission, treatment, and disposal for the next 20 years. This Plan was prepared in accordance with the provisions of the Revised Code of Washington (RCW), Section 90.48, Water Pollution Control, Washington Administrative Code (WAC) Section 173-240-050, General Sewer Plan. Development of the Plan has been coordinated with the City of Lake Stevens and Snohomish County planning efforts and plans. The Plan is intended to be feasible in terms of engineering, economic, regulatory, and political frameworks. Included in the Plan are planning level designs and cost estimates for recommended major improvements to facilities as well as proposed construction years and a financing plan. A State Environmental Policy Act (SEPA) checklist is provided in Appendix A. The projects described in the Plan are consistent with State regulations relating to the prevention and control of discharge of pollutants into State waters, anti-degradation of existing and future beneficial uses of ground waters, and anti-degradation of surface waters. The District’s 2007 Plan and 2010 Plan Amendment were prepared by Gray & Osborne, Inc., in coordination with the District Board of Commissioners and staff. That plan is the basis for this current planning effort and this report. CHS Engineers has used significant elements of the District’s prior reports to develop this updated Plan. CHS Engineers has reviewed or prepared all information presented herein, except where specifically noted. Detailed references are presented at the end of this Plan. The Lake Stevens Sewer District is located within Snohomish County in the state of Washington as shown in Figure 1-1. The District issued a Determination of Non-significance for the action of Plan adoption on April 13, 2016. No comments were received in response to the notice of threshold determination. A public hearing was held on April 28 and continued to May 12, 2016. The only public comment was by email to the Manager recommending a pending lift station project be included in the Plan. A final draft of this Plan dated May 2016 was provided to the City of Lake Stevens, Snohomish County, Snohomish Health District and Washington State Department of Ecology for review. All parties responded with preliminary approval or minor recommended revisions. Those revisions have been incorporated in the final version of


the Plan. Copies of that correspondence are included in Appendix A. A copy of the District’s resolution adopting this final Plan is also included in Appendix A. SCOPE OF WORK This Plan is organized as follows:

Summary and Recommendations: This section is a general overview of the Plan including background, service and study area, population forecasts, existing system description and recommended improvements.

Chapter 1 – Introduction: This chapter contains descriptions of the

purpose and scope of the Plan and provides background information aimed at providing a perspective for the issues discussed in the Plan.

Chapter 2 – Service and Study Areas Characterization: This chapter

provides a brief history of the District and describes the physical characteristics of the Service and Additional Study Areas.

Chapter 3 – Population and Land Use: This chapter defines the planning

period, presents the land use policies of the City of Lake Stevens and Snohomish County, and provides current and projected population.

Chapter 4 – Design and Planning Criteria: This chapter utilizes the

population numbers generated in Chapter 3 and historical treatment plant records (daily monitoring reports – DMRs), water use records, and flow monitoring data to develop existing and future wastewater flows and loadings.

Chapter 5 – Existing Sewer System: This chapter provides an inventory

of the existing collection system, including lift stations, force main, and gravity mains, and a summary of the recently constructed wastewater treatment plant. Also included is a discussion of current interlocal agreements and moratoria.

Chapter 6 – Collection System Evaluation: This chapter presents a

discussion of the computer modeling for the sewer system and also the results of the modeling, and identifies system deficiencies.

Chapter 7 – Capital Improvement Plan: This chapter summarizes the

recommended sewer system capital improvement projects and implementation schedule of those projects.

Chapter 8 – Operation and Maintenance: This chapter describes the

activities and costs associated with the daily operation and maintenance of the sewer system.


Chapter 9 – Financing Plan: This chapter provides an assessment of the

financial status of the District, discusses available and potential revenue sources for the system improvements discussed in the previous chapters.

Chapter 10 – Developer Project Standards: This section summarizes the

process by which property owners and developers complete sewer developer extensions. Sewer design and construction standards are summarized and referenced.

References: Summary of primary sources of information for development

of this updated Plan. Appendices: Additional materials referenced in the Plan are included in

several appendices, including SEPA documentation, interlocal agreements and other materials.

PROJECTS COMPLETED SINCE THE 2007 PLAN Table 1-1 provides a list of completed District projects that were listed in the 2007 Plan.

TABLE 1-1 District Projects Completed Since 2007 Plan

Project Description Year Completed Treatment Plant

New WWTF 2012 Lift Stations and Force Mains

LS 20 Lift Station #20 2014 C2-A1 LS 17 Force Main Extension 2014

Gravity Sewer Mains VRD-A Vernon Road Diversion 2012 VRD-B Vernon Road Diversion 2012 G1-A Southwest Interceptor Ph I 2014 G1-B Southwest Interceptor Ph II 2014

RELATED PLANNING DOCUMENTS The following documents were consulted in the preparation of this Sanitary Sewer Comprehensive Plan update. GROWTH MANAGEMENT ACT (GMA) RELATED PLANS


City of Lake Stevens Comprehensive Plan, September 2015 The City of Lake Stevens Comprehensive Plan, which was prepared by the City of Lake Stevens Planning Department, was originally adopted in 1994 and amended annually thereafter. This document was developed to comply with the State’s Growth Management Act (GMA), and is consistent with the planning policies of Snohomish County and neighboring jurisdictions. Land use, transportation, housing, parks, recreation and open space, cultural and historic resources, environmental resources, economic development, capital facilities and utilities, and an implementation element are all addressed in this document. The City’s Comprehensive Plan has been amended seven times, with the most recent amendment adopted in September, 2014. In late 2006, the City completed a master plan for the Grade Road Planned Business District. There has been no public or private development activity in this area since completion of this plan. The City has also prepared and adopted two subarea plans: one for the Lake Stevens Center area (a.k.a Frontier Village, SR204/SR9 intersection area) and 20th St. SE Corridor. Both subarea plans were adopted in 2012. A combined subarea capital facilities plan was also prepared and adopted by the City in 2012. The City is preparing a subarea plan to support future long-range planning of the original Downtown Lake Stevens and immediate area. A detailed plan has not yet been prepared but the general concepts provided by City staff have been considered in the development of this Plan. Work on a plan for the downtown area was initiated in 2005 under the title Towncenter Concept Plan. That effort took place when the City was much smaller and in different economic conditions. The current downtown framework plan effort began in 2012 as a renewed and broader approach than represented in the previous plan. A new subarea planning process is under development. The subarea plan is scheduled for completion in mid-2017 and will identify uses, development intensity, public improvements and development standards. The City adopted its 2015-2035 Comprehensive Plan in September 2015. Development of this sewer system plan has taken into consideration information available from the City’s update. The City’s 2015-2035 Comprehensive Plan includes numerous goals and policies. In the context of land use, and the need for public facilities to serve the projected land uses, the City plan includes goals and policies to support growth and development consistent with the County Comprehensive Plan and to coordinate land use decisions with capital improvement needs, in a fiscally responsible manner. Snohomish County GMA Comprehensive Plan General Policy Plan, February 2006


The Snohomish County GMA Comprehensive Plan was prepared by the Snohomish County Planning Commission, and approved by the County Council in January 2006. This document includes all mandatory growth management elements including economic development and natural environment, as well as policies and projections on population and employment. In 2013, the County adopted its 2012 Buildable Lands Report (BLR). This Report includes a Supplemental Map Book. The map book includes detailed analysis of then-current land status, zoning and future land use, critical areas and easements, additional housing unit capacity and additional employment capacity, for each urban growth area in the UGA. The BLR report was prepared by County staff in coordination with staff from the many municipal jurisdictions throughout the County through the Snohomish County Tomorrow (SCT) process. SCT is the process under which agencies in the County coordinate on state Growth Management Act issues. The 2012 BLR concludes that there is a net surplus of buildable capacity in urban growth areas (UGAs) County-wide and in the Lake Stevens UGA at year 2025, for population target identified in 2006. The County publishes an annual Growth Monitoring Report (GMR). The latest report is the 2013-2014 GMR dated October, 2014. The County adopted growth targets, including targets for the Lake Stevens UGA, in June, 2015. This adoption is embodied in an updated Appendix D to the County Comprehensive Plan, effective July 2, 2015. The year 2035 targets are 46,380 persons, 17,311 housing units and 7,821 jobs. Lake Stevens School District Capital Facilities Plan, August, 2014 This plan evaluates the District’s existing and forecast enrollment population and existing and forecast capital facilities needs. The current plan considers the 20-year planning horizon through year 2035, with a detailed capital improvement plan for years 2014-2019. The Lake Stevens School District serves all of the City of Lake Stevens, some unincorporated areas of the County and a small area of the City of Marysville. WASTEWATER SYSTEM PLANS AND REPORTS Lake Stevens Sewer District Sanitary Sewer System Comprehensive Plan, Gray & Osborne, Inc., September 1998 The 1998 Sanitary Sewer Comprehensive Plan was a major update to the District’s planning process, as the District had experienced rapid growth since the prior plan, in 1983. The 1998 Plan evaluated the existing wastewater collection and treatment facilities and provided a rate analysis to determine the affect on sewer rates based on the recommended Capital Improvement Plan (CIP). Recommendations from the 6-year


CIP included interim improvements to the treatment plant, lift station and force main upgrades and new facilities, and gravity sewer main projects. Amendment No. 1 Lake Stevens Sewer District Sanitary Sewer System Comprehensive Plan, Gray & Osborne, Inc., September 2002 The 2002 Amendment addressed three major issues. First, the land use proposals considered by Snohomish County since the adoption of the 1998 Plan required the District to review the timing and scope of the CIP. The second change was related to the completion of some projects by developers at the south end of the lake and the subsequent changes to the CIP. Third, it was determined that a new lift station, Lift Station No. 15 was required in lieu of simply upgrading Lift Station No. 5. This new lift station was required to lift a moratorium on development north of the lake. The recommended CIP for the 2002 Amendment was revised to reflect the updated analysis. Recommendations from the 6-year CIP included interim improvements to the treatment plant, lift station and force main upgrades and new facilities, and gravity sewer main projects. Amendment No. 2 Lake Stevens Sewer District Sanitary Sewer System Comprehensive Plan, Gray & Osborne, Inc., November 2003 The 2003 Amendment addresses two specific issues, including recommendations from the wastewater treatment plant (WWTP) upgrade as described in the 2003 Wastewater Facilities Plan (draft, WFP); and a perceived need to provide sewer service to difficult-to-sewer areas within the District through District participation. The WFP generated flow projections based on 2006 Snohomish County land use policy adoptions. Amendment No. 2 updated the CIP with the major change recommended in the WFP to construct a new WWTP at an existing District-owned site approximately one mile south of the current facility. Recommendations from the 6-year CIP included a new treatment plant, lift station and force main upgrades, and gravity sewer main projects. Amendment No. 3 Lake Stevens Sewer District Sanitary Sewer System Comprehensive Plan, Gray & Osborne, Inc., May 2005 The 2005 Amendment provided an update to the 1998 Plan to reflect the District’s decision to construct the new treatment plant using the membrane bioreactor (MBR) process. This process is significantly different than the previously selected activated sludge process. In addition, since the 2003 Amendment, the District and the City of Lake Stevens had entered an Interlocal Agreement (ILA) in which the District assumed all sewer collection, treatment, and disposal operations within the District and the City. Recommendations from the 6-year CIP included approximately a new treatment plant, lift station and force main upgrades, and gravity sewer main projects. Lake Stevens Sewer District Wastewater Facilities Plan, Gray & Osborne, Inc., September 2006


The 2006 Wastewater Facilities Plan (WFP) provided a long-term strategy, over a 20-year planning horizon, to manage the District’s wastewater treatment and disposal systems. The WFP was based on growth assumptions and planning data from the 1998 Sanitary Sewer Comprehensive Plan, and included conceptual designs and cost estimates for major treatment plant facility improvements and a financing plan for those improvements. Lake Stevens Sewer District Sanitary Sewer Comprehensive Plan, Gray & Osborne, Inc., October, 2007 The 2007 Sanitary Sewer Comprehensive Plan (SCP) provided a long-term strategy, over a 20-year planning horizon, to forecast flows and capital improvement needs for the District’s wastewater treatment and disposal systems. The WFP was based on growth assumptions and planning data from the 1998 Sanitary Sewer Comprehensive Plan, updates per the 2006 WFP, and related updated analysis. The basis for the land use plans and population projections were the 2006 comprehensive plans for the City and County. Amendment No. 1, Lake Stevens Sewer District Sanitary Sewer Comprehensive Plan, Gray & Osborne, Inc., July 2010 This amendment updated selected elements of the 2007 Plan, and included updates to the Capital Improvement Plan.

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CHAPTER 2

SERVICE AND STUDY AREA CHARACTERIZATION INTRODUCTION The sanitary sewer service area of the Lake Stevens Sewer District is almost entirely within the Lake Stevens Urban Growth Area (UGA) and includes all of the area within the limits of the City of Lake Stevens. The service area is predominantly within the drainage basin tributary to Lake Stevens, with some portions lying outside of this natural basin. The existing sewer system extends through much of the sewer service area, but there are areas yet to be sewered, particularly in the southern portion of the UGA. The existing system is discussed further in Chapter 5. For purposes of this Sanitary Sewer Comprehensive Plan, the “service area” is established as follows:

includes all area within the Lake Stevens UGA, as presently defined by Snohomish County (except a small area consisting of SR 204 right of way)

includes a previously developed plat outside and west of the UGA includes a small area within the Marysville UGA but in the District Boundary, that

is served by the District by agreement excludes all other areas within the District Boundary outside the Lake Stevens

UGA. The area within the District but excluded from the service area is the rural land between Ebey Slough and the UGA, including the former wastewater treatment plant site and adjacent areas. For purposes of this Plan, the “additional study area” is established as all areas abutting the Lake Stevens UGA designated by the County as “rural-urban transition areas” (RUTAs), and west of a generally defined topographic divide west of, above and roughly parallel with the Pilchuck River. This additional study area is smaller than the study area considered in the 2007 Plan, having removed from consideration the rural lands north of 44th St NE and east of SR 9. The RUTAs are being studied as part of this Plan in order to better define the potential future impacts to the District’s facilities. A general characterization of the service and study area is presented below. LAKE STEVENS SEWER DISTRICT The Lake Stevens Sewer District was formed in 1957 in response to bacterial contamination and algal blooms in Lake Stevens. The primary cause was ineffective on-site sewage disposal systems within the Lake’s drainage basin. The District’s first wastewater treatment facility began operation in 1965. The 1.4-acre oxidation lagoon was created to treat the Frontier Village complex. The District expanded its collection


system through formation of utility local improvement districts (ULIDs). In 1971, the first treatment plant expansion was completed with the addition of an 8.5-acre lagoon constructed in parallel with the existing lagoon. In 1986 that facility was converted to an activated sludge secondary treatment plant including headworks, two aerobic digesters, two clarifiers and a chlorine contact tank. The District recently completed construction of a complete new wastewater treatment facility, at a new location: between Sunnyside Boulevard and State Route 204, immediately south of 9th St. SE. The new Sunnyside Wastewater Treatment Facility (WWTF), a membrane bioreactor (MBR) plant, was completed and began operation in 2012. The District is preparing to complete a project to remove accumulated biosolids from the former treatment lagoons and is considering how best to decommission the existing facility. All wastewater flows have been diverted to the new facility. Until 2005, the District operated and maintained the sewer system within the UGA but outside the City of Lake Stevens, and the City managed their separate sewer system within the City limits. An agreement between the District and the City in 2005 provided for long-term management of a unified sewer collection and treatment system throughout the entire UGA. Under the agreement, the City transferred its entire system to the District to own, operate and maintain, for a period of at least twenty years following completion of the new WWTF. The City and District have mutual responsibilities for cooperation for sewer system planning, annexations and related matters. This cooperation is manifest in regular meetings of a Utility Committee including the three District Commissioners and three City elected officials. CITY OF LAKE STEVENS The City of Lake Stevens is located in west-central Snohomish County. First settled along the east shore of the Lake in 1886, the town began as a main link from the Monte Cristo timber and mining resources to the west. The Rucker Brothers Timber Company built a railroad spur to Lake Stevens in 1905. The mill that opened two years later soon became known as the “world’s largest sawmill” but subsequently burned in 1919. Following another fire in 1925, the mill was permanently dismantled. Through the 1950s, many public and private resort beaches surrounded Lake Stevens. The City was officially incorporated as a city in 1960 with a population of 900. The City grew to a population of nearly 6,400 by the year 2000. Two large annexations in the mid-2000s expanded the City limits around the north and west sides of the Lake. Those expansions and growth lead to a City population of 29,170 as of 2014. SERVICE AND STUDY AREA The service area for this plan is essentially the same as in the 2007 Plan, but the additional study area is significantly reduced. The impact of the recent recession has reduced the anticipated growth rate. The service area is approximately 10.9 square miles. The service and study area includes an area of approximately 19.4 square


miles. The previous plan considered approximately 28 square miles for potential service by the District. The basis for establishment of the service and study area limits is outlined above. Geographically, the service and study area extends from above Ebey Slough on the west to the bluffs overlooking the Pilchuck River on the east; and from SR 2 on the south to 44th St NE to the north. Figure 2-1 shows the sewer service area and the extent of the additional study area, as well as current District and City of Lake Stevens boundaries, the Lake Stevens and Marysville UGA boundaries, and the County-designated RUTAs. Table 2-1 shows a breakdown of the service and study areas.

TABLE 2-1 Service and Study Areas

Location Area

(acres) Service Area City of Lake Stevens 5,696 Unincorporated Snohomish County (UGA) 1,281 In Marysville UGA 10 Total - Service Area 6,987 Study Area Rural Transition Areas 5,411 Total - Service and Study Areas 12,398

PHYSICAL CHARACTERISTICS The physical characteristics within the service and study area are essential elements for considering locations for future sewer service and facilities. The relevant components discussed here include topography, soils and geology, climate and surface water (sensitive areas). TOPOGRAPHY The general topography within the study area is shown in Figure 2-2. The topography is rolling with a maximum elevation of approximately 460 feet, east of Lake Stevens Middle School along SR 9 and a minimum elevation of approximately 20 feet along Sunnyside Boulevard near the previous wastewater treatment facility and Ebey Slough. SOILS AND GEOLOGY


Two major ice flows, the Admiralty and the Vashon, at one time covered the Lake Stevens area. The last glaciation took place approximately 14,000 years ago. The general soil type in the study area is Tokul gravely medial loam, as defined in the National Cooperative Soil Survey, published by the National Resource Conservation Service of the United States Department of Agriculture. Tokul gravely medial loam is a moderately deep, moderately well drained soil formed in glacial till and volcanic ash. The surface layer is dark brown gravely loam about 4 inches thick. The subsoil is brown and dark yellowish brown gravely loam about 18 inches thick and the substratum is light olive brown gravely fine sandy loam about 9 inches thick. A hardpan exists at the depth of about 20 to 40 inches. Permeability of this soil is moderate to the hardpan and very slow through the hardpan itself. The available water capacity is moderate. The main limitations for residential use are the seasonal perched water table and the shallow depth hardpan which limits septic tank/drain field use. CLIMATE The local climate is greatly tempered by the influence of Puget Sound, typical of areas surrounding the Sound. Winters are wet and relatively mild. In general, the prevailing direction of the wind is south or southeasterly in the winter and west or northwesterly in the summer. Normal wind movement is moderate, in the range of two to 20 mph. Local temperatures range from 30 degrees F to 50 degrees F in the winter with brief dips below 30 degrees F. Summers are characteristically cool and relatively dry with temperatures rarely exceeding 80 degrees F. The normal frost-free season ranges from 180 to 200 days. Drainage Improvement District No. 8, previously serving the Lake Stevens area, collected precipitation data on Lake Stevens at 1911 Vernon Road through at least 2005. The Drainage District was assumed by the City in 2008. Precipitation data was thereafter collected by Snohomish County Surface Water Management at 132 – 131st Ave NE. Precipitation data is summarized in Table 2-2.

TABLE 2-2 Precipitation, 1997-2014

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total 1997 5.39 4.53 5.91 5.24 2.79 4.31 1.81 0.63 2.38 4.92 4.22 5.44 47.57 1998 7.61 4.27 6.19 3.38 4.61 2.67 0.48 0.56 1.12 7.06 7.16 7.89 53.00 1999 7.07 7.74 4.62 2.08 4.44 5.17 2.57 1.37 0.66 4.28 11.54 6.15 57.69 2000 4.61 4.23 5.51 3.02 4.65 1.61 3.27 0.67 3.27 3.76 2.65 3.21 40.46 2001 3.44 1.73 4.11 4.23 2.67 4.12 1.56 1.84 1.30 6.49 7.48 6.14 45.11 2002 5.98 3.24 4.48 2.88 3.56 1.51 1.30 0.32 1.28 1.60 2.46 5.48 34.09 2003 6.07 2.25 5.00 3.35 3.00 0.55 0.06 0.23 0.95 7.31 5.65 3.13 37.55 2004 4.89 2.80 2.96 1.36 4.67 0.84 0.48 2.75 2.00 2.78 4.23 4.35 34.11


Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total 2005 1.92 1.23 2.18 5.07 3.22 3.67 0.99 0.52 1.59 2.41 4.92 4.29 32.01 2006 DNA DNA DNA DNA DNA DNA DNA DNA DNA DNA DNA DNA 0.00 2007 DNA DNA DNA DNA DNA DNA DNA DNA DNA DNA DNA DNA 0.00 2008 DNA DNA DNA DNA DNA DNA 0.41 2.77 1.33 DNA DNA DNA 4.51 2009 4.86 1.24 5.77 3.98 3.67 0.68 0.57 1.54 2.53 3.52 7.79 6.10 42.25 2010 5.44 3.07 3.75 5.83 4.87 5.06 0.10 3.26 4.47 8.00 8.90 3.00 55.75 2011 8.69 4.21 8.95 7.24 5.05 4.06 1.97 0.34 1.41 2.90 5.50 5.80 56.12 2012 5.19 7.70 8.50 5.46 4.92 6.30 1.62 DNA 0.41 3.67 7.06 2.17 53.00 2013 9.24 3.77 4.88 6.42 2.32 3.25 0.06 2.01 5.20 7.88 8.11 6.30 59.44 2014 5.75 5.73 8.32 4.64 3.68 2.15 1.50 1.82 3.28 1.93 5.52 3.69 48.01 Avg. 5.87 3.92 5.62 4.50 3.91 3.15 1.18 1.39 2.25 4.58 6.37 4.82 47.41 Min. 1.92 1.23 2.18 1.36 2.32 0.55 0.06 0.23 0.41 1.60 2.46 2.17 32.01 Max. 9.24 7.74 8.95 7.24 5.05 6.30 3.27 3.26 5.20 8.00 11.54 7.89 59.44 Notes:

DNA = data not available

Data is in inches

CRITICAL AREAS The prevalence of critical areas throughout the study area can have significant impact on the amount, type, and timing of development. Figure 2-3 shows areas identified by Snohomish County that may contain sensitive areas. Where areas are so critical to require regulatory protection, these areas may be considered “unbuildable,” and may become parcels specifically designated as such. Other areas that may be impacted by severe topography, challenging soils, etc., will have to wait for development when the time comes such that land values warrant the additional expenditure for developing the necessary infrastructure. The mere presence of topographical or other environmental constraints, however, does not in and of itself prevent development from occurring. Mindful that other types of public facilities must also accompany new development (e.g., roads, utilities, drainage), efficient planning and engineering design can bring the needed sewer facilities to an area by use of a combination of gravity sewers, force mains, and lift stations. In order to appropriately plan for development of the service and study area and future expansion of the sewer system, because of significant amounts of topographical relief throughout the study area, existing land uses, and future land uses designated by Snohomish County and the City of Lake Stevens, this plan makes some broad assumptions regarding housing densities and sewer facility locations. Areas subject to potential flooding, as mapped by the Federal Emergency Management Agency (FEMA) are generally limited to three locations in the study area. The area in the “T”-shaped area of the District Boundary is subject to flooding associated with Ebey Slough. Portions of the shoreline of Lake Stevens, particularly along the north and east


sides, are subject to flooding, as are areas along Catherine Creek in the northeast part of the City and Little Pilchuck Creek east of the City in the unincorporated UGA. UTILITIES WATER SYSTEM Water service within the planning area is provided by the Snohomish County Public Utility District No. 1 (PUD). The distribution system includes four storage tanks, totaling 10,000,000 gallons, and three pump stations. The PUD purchases water from the City of Everett. The water is from Spada Lake, in the Sultan River, 25 miles east of Everett. The Lake Stevens regional water system now has two wells supplying water within the City of Lake Stevens. Previously, these wells were used as back-up wells due primarily to water quality problems from secondary contaminants (iron and manganese). However, following the completion of a new treatment facility in September of 2012, these wells now supply water after it is treated for iron and manganese removal, chlorinated and injected with fluoride. OTHER WASTEWATER SYSTEMS The City of Lake Stevens owned and operated facilities to collect wastewater from within its City limits and convey the wastewater to the District for treatment, from 1971 until 2005. In 2005, through an interlocal agreement between the City of Lake Stevens and the District, the District assumed ownership, maintenance, and operation of the City’s sewer system. The agreement includes terms for an eventual return of the entire sewer system to the City. The City of Marysville has a wastewater collection system northwest of and adjacent to the District. There is an interlocal agreement for sewage conveyance and treatment between the District and the City of Marysville for a small development of less than 30 homes. Marysville maintains a wastewater treatment facility located just over four miles northwest of the District’s facility. The District provides filtrate disposal services for Evergreen Sanitation, Inc. Evergreen is a septage hauling and treatment service company with treatment facilities located northeast of downtown Lake Stevens. The contract limits the discharge to the District system to 50,000 gallons per day of septage filtrate. The City of Everett has a treatment facility located 1.7 miles west of the District’s facility and separated from the District by Ebey, Steamboat, and Union Sloughs. The City of Snohomish operates a wastewater collection system located south of the District’s service area. Snohomish treats their wastewater at a treatment facility located approximately five miles south of the District’s treatment facility.


The City of Arlington operates a wastewater collection and treatment system. That facility is approximately 14 miles north of the District’s treatment facility. The City of Granite Falls operates a wastewater collection and treatment system. That facility is approximately nine miles northeast of the District’s treatment facility. The City of Monroe operates a wastewater collection and treatment system. That facility is approximately 12 miles southeast of the District’s treatment facility. There are approximately 1,800 properties served by septic tank and drain field systems within the service area1. According to the Snohomish County Health Department and WAC 246-272A, the minimum land area requirement for an onsite sewage disposal system is based on the soil type. A general review of soil types in the Lake Stevens area indicates that onsite systems would be limited to lots of 20,000 square feet or larger for lots with public water supply and two acres for lots with onsite wells. A majority of the septic tank and drain field systems are greater than 200 feet from the existing District collection system. About 400 of the subject properties could be served by the existing collection system with sewer extensions or side sewers up to about 200 feet in length. Existing septic tank and drain field systems within the District’s boundaries may be required to connect to the District’s collection system if the on-site system has failed and repair is not possible, in accordance with the rules of the Health Department. See Figure 2-4 for a depiction of the location of onsite systems in the service and study area, including those that are within 200 feet of the existing sewer system.

1 The data to prepare this analysis and Figure 2.4 is based on Snohomish County GIS records, compared to the collection system map and District billing records. A few plats and other parcels were shown by the County data with onsite systems even though there is existing sewer serving those plats. District staff confirmed sewer is available to those lots and those lots have been excluded from the data considered for this analysis. The resulting count of systems in the service area is still slightly higher than is suggested by the comparison of existing population and current residential sewer service connections, as presented in Chapter 3. Given some unusual data points in the County GIS data used for this analysis, it is presumed that this count is less accurate than suggested by the analysis in Chapter 3.

LegendCITY OF LAKESTEVENSSERVICE AREAADDITIONAL STUDYAREALAKE STEVENS UGABOUNDARYDISTRICTBOUNDARYRURAL URBANTRANSITION AREAMARYSVILLE UGA

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CITY OF LAKESTEVENSDISTRICTBOUNDARYSERVICE AREALAKE STEVENS UGABOUNDARYRURAL URBANTRANSITION AREAMARYSVILLE UGA


FIGURE 2-2TOPOGRAPHY

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LegendGROUNDWATER COURSE

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CHAPTER 3

POPULATION AND LAND USE INTRODUCTION Specific land uses, such as residential, industrial, and commercial developments, generate wastewater flows and loadings to the District’s collection, conveyance and wastewater treatment facilities. The configuration of the sewer system is based on growth projections, development trends, political considerations, topography, and the drainage characteristics of the service area. Based on the service area’s growth history and the need to provide wastewater treatment facilities for future growth, and the potential for expansion of service into the study area, the wastewater treatment and sewer systems are in need of continuous evaluation and improvement. This chapter provides information relating to land use and associated zoning designations, the service area’s growth history and existing and projected population for the service and study areas. This information is used in later chapters to evaluate the District’s wastewater facilities and their adequacy to serve future growth and to meet regulatory requirements through the year 2035. PLANNING PERIOD The planning period for the District’s wastewater system should be long enough to be useful for an extended period of time, but not so long to be impractical. This Plan includes 6-year and 20-year planning periods to allow for the implementation of the District’s capital improvement program (CIP). The 6-year planning period extends through the year 2021. The City and County are presently completing updates to their respective comprehensive plans, for a planning period through 2035. This Sanitary Sewer Comprehensive Plan will extend the capital improvement program to the year 2035 consistent with the City and County plans. GROWTH MANAGEMENT The Growth Management Act (GMA) was enacted in 1990 to address the significant population growth that occurred in areas of Washington State during the 1980s. To ensure a continuation of Washington’s high quality of life, officials across the state have addressed growth management within various levels of government. The basic objective of the GMA is to encourage county and city governments to develop and implement a 20-year comprehensive plan that incorporates their vision of the future within the framework of the broader needs of the State. Under the GMA, cities within a county must complete their own planning and coordinate the planning efforts with those of the county and neighboring cities. The planning effort of a city and county includes the establishment of an urban growth area (UGA). The


City of Lake Stevens and Snohomish County established the City’s first UGA in 1994 to accommodate future growth of the City and area around Lake Stevens. In a process concurrent with preparation of the 2012 Buildable Lands Report (BLR), Snohomish County Tomorrow developed population targets for planning through year 2035, to coincide with the end of the County Comprehensive Plan forecast period. Those targets are published in the 2013-2014 Growth Monitoring Report (GMR). The BLR concludes that the Lake Stevens UGA has capacity, under current land use and zoning regulations, for a total residential population of 46,634 persons. The UGA considered for this Plan is the same geographical area as designated at the time of development of the 2007 Plan and 2010 Amendment. The County growth target for year 2025 (46,125 per 2006 City and County comprehensive plans) was nearly the same as the County growth target for year 2035 (46,380) under the current County planning effort. The 2010 Amendment to the 2007 Comprehensive Sewer Plan anticipated a population served by the sewer system, in year 2025, of 42,987. These previous planning targets and the data in Table 3-4 (discussed below) are presented for historical reference only and are not used for development of this Plan. As discussed in Chapter 1, the County adopted growth targets as Appendix D of their Comprehensive Plan, effective July 2, 2015. Forecast population is discussed in more detail later in this chapter. LAND USE AND ZONING The purpose of designating land use is to guide development to meet land use regulations and implement the land use goals identified in the city or county’s comprehensive plan and supporting regulations. The County’s jurisdiction applies in unincorporated areas, including such areas within a UGA associated with a specific city. The City of Lake Stevens and Snohomish County each have established land use and zoning requirements within the City’s corporate boundaries and UGA, respectively. Designated land uses include various densities or types of residential, commercial and industrial development and uses. The land outside the UGA immediately adjacent to the service area is designated predominately for rural and agricultural uses. The specific designations are shown on Figures 3-1 and 3-2, and listed in Tables 3-1 and 3-2. At the time of new development all residential, commercial, and industrial zoning designations must be served by public sewer, water, roads, and other public facilities and services. Changes in land use since the completion of the 2007 Plan include the impacts of annexation of the southwest portion of the UGA by the City, and preparation of two sub-area plans (20th ST SE Corridor and Lake Stevens Center). In the southwest quadrant of the UGA, County land use was predominately medium and low-density residential


whereas the City assigned medium density residential land use throughout much of the annexation area. The 20th ST SE Subarea Plan revised land use along the south side of 20th ST SE to be largely commercial or public/semi-public rather than residential of varying density. The City is working on a subarea plan for the downtown area in the northeast part of the City. This subarea plan is scheduled for completion in mid-2017. The downtown study area is centered on Main Street between 20th Street NE and 16th Street NE and associated areas within ¼ to ½ mile radius. The area includes the current civic center with post office and library and local commercial developments, existing single and multi-family residential development around and north of the current police station. Work completed to date includes identification of general land uses around that area including public/civic uses, open spaces, and a mix of new commercial, retail and residential developments. An economic development strategy was commissioned by the City in 2010 to support development of the concept plan and consider the fiscal impacts of such redevelopment. The strategy report anticipated a long time for redevelopment to occur, with about 50 percent completion by year 2030 and full redevelopment achieved by year 2050. CITY OF LAKE STEVENS The City of Lake Stevens has actively participated in the land use planning of the UGA with Snohomish County and coordinated their land use and zoning designations with those of the County. The land use and zoning designations as adopted by the City in October, 2014, are summarized in Table 3-1. Gross housing density limits for new development are indicated for the residential zones. The boundaries for these areas are shown on Figures 3-1 and 3-2. The land uses as presented herein is anticipated to be the land use as represented in the City’s 2015-2035 Comprehensive Plan, with one minor exception for a parcel near City Hall.

TABLE 3-1 City of Lake Stevens Land Use and Zoning Designations

Land Use Designation(1) Zoning District(2) Gross Residential Density (dwelling

units/acre)

High Density Residential (HDR) HUR, MFR, MFDA, NC, P/SP 12

Medium Density Residential (MDR)

SR, WR, UR, HUR, NC, P/SP 4-12

Waterfront Residential (WR) WR, P/SP 4


Land Use Designation(1) Zoning District(2) Gross Residential Density (dwelling

units/acre)

Downtown/Local Commercial (D/LC or LC) CBD, LB, P/SP N/A

Commercial (COM) UR, HUR, BD, CD, NB, P/SP 4-12

Mixed Use (MU) MU, P/SP, MSD, MUN 12 Planned Business District (PBD) PBD, P/SP N/A

General Industrial (GI) GI, LI, P/SP N/A General Industrial w/ Development Agreement (GIDA)

GIDA, P/SP N/A

Light Industrial (LI) LI, P/SP N/A Public/Semi-Public (P/SP) P/SP N/A

(1) City of Lake Stevens Comprehensive Plan, Amended October 2014. (2) Zoning is further defined per City of Lake Stevens Municipal Code, Title 14.

For areas lying within the City’s corporate limits, the following land uses are available:

High Density Residential (HDR) allows any form of single-family, two-family, and multi-family residential use with no density limits. It also allows limited public/semi-public, community, recreational, and commercial uses. Some zoning districts and development regulations limit residential gross density to 12 dwelling units per acre (du/ac).

Medium Density Residential (MDR) allows single and two-family residential development, including detached, attached, conversion, accessory apartments, townhouses, condominiums, duplexes, tourist homes, special service homes, and some manufactured/mobile structures with a gross density of four to 12 du/ac. It also allows limited public/semi-public, community, recreational, and neighborhood commercial uses.

Waterfront Residential (WR) allows single-family residential uses with a gross density of four du/ac. It includes detached houses, tourist houses, and special service housing. It also allows limited public/semi-public, community, and recreational uses.

Downtown/Local Commercial (D/LC) or Local Commercial (LC) are high intensity land uses including the central business district zone and other dense arrangements of professional offices and retail stores. This designation discourages uses that are land consumptive (i.e., warehouses) or


generate high traffic volumes (i.e., drive through businesses or gas stations). Mixed-use development is allowed.

Commercial (COM) is a high intensity land use that includes both high-intensity retail and employment uses including community and regional retail centers, offices, business parks, and associated uses. Multi-family residential uses could be included above or behind commercial uses. It should be located in areas with direct access to highways and arterials in addition to transit facilities, adequate public services and traffic capacity.

Mixed Use (MU) is a high intensity land use that includes and encourages

both commercial and residential elements. It is intended that this land use designation be placed where a “village atmosphere” is desired, or as a transition from high and low density zones. For the purposes of this plan, it is assumed that the gross housing density is 12 du/ac.

Planned Business District (PBD) allows moderate intensity commercial or mixed-use development. It is intended that this land use designation be placed on lands between high and low intensity uses, or on sites containing sensitive resources. It also allows limited public/semi-public, community, and recreational uses.

General Industrial (GI) and General Industrial with Development Agreement (GIDA) allows a full range of industrial uses which may impact surrounding properties. This category also allows retail sales, public/semi-public, community and recreational uses. It should be located in areas with direct access to truck routes, adequate public services and infrastructure and traffic capacity.

Light Industrial (LI) allows a full range of industrial uses with less impact to surrounding properties than general industrial properties. The City looks to this designation as accommodating the future high-tech industries and family-wage jobs. This category also allows retail sales, public/semi-public, community and recreational uses. It should be located in areas with direct access to truck routes, adequate public services and infrastructure and traffic capacity and be transitional to commercial/mixed-use areas.

Public/Semi-Public (P/SP) includes public buildings, services, and

transportation facilities to support operations of the Sewer District, City, school district, fire district and miscellaneous other governmental functions.

SNOHOMISH COUNTY Similar to the City’s land use and zoning designations, the purpose of designating land use within Snohomish County is to guide development to meet land use regulations and implement the land use goals identified in the County’s Comprehensive Plan. The


Snohomish County GMA Comprehensive Plan, General Policy Plan, as amended effective December 2013, provides land use and zoning designations for Snohomish County in and around the Lake Stevens UGA. These designations are summarized in Table 3-2. Housing density limits used in this plan are indicated for the residential zones. The minimum net density in UGAs may not be less than four dwelling units per net acre, except for limited exceptions related to transportation planning. Minimum net density is determined after gross areas are reduced for roads, stormwater facilities, public uses, critical areas and their buffers. Minimum net density is determined by rounding to the whole unit. Minimum lot size in residential areas shall be 6,000 square feet, except as allowed under the zoning code. The boundaries for County-designated areas are shown on Figures 3-1 and 3-2.

TABLE 3-2 Snohomish County Land Use and Zoning Categories

Land Use Designation(1) Zone Category(2)

Residential Density

(dwelling units/acre)

Urban Medium Density Residential (UMDR) MHP, LDMR, R-7,200 4-11

Urban Low Density Residential (ULDR-L(4)) R-9600, R-20,000 4

Urban Low Density Residential (ULDR-L(6)) R-7200 6

Rural Residential-5 (RR-5) RR5/BASIC R-5, RB 0.2

Urban Industrial (UI) BP, HI N/A Public/Institutional Use (P/I) R-20,000 (3) N/A

(1) Reference Snohomish County General Policy Plan, February 1, 2006, amended 2013. (2) Zoning further defined as described in Snohomish County Code, Title 30. (3) All Public/Institutional uses are shown as being located in the R-20,000 zone. (4) County land uses and zoning districts outside the UGA are not included, other than zoning in the RUTAs.

For areas lying within the Lake Stevens UGA and the surrounding study area, the following brief descriptions of each land use is provided:

Urban Medium Density Residential allows a combination of detached homes on small lots, townhouses, and apartments in medium density, multi-family residential developments. Implementing zones can include mobile home parks (four to eight du/ac), low density multiple residential


(LDMR, four to 11 du/ac) and R-7,200 (four du/ac).

Urban Low Density Residential allows mostly detached housing developments on larger lot sizes. The County plan identifies two densities for this land use designation, in the Lake Stevens UGA. In the unincorporated area along the southeastern lakeshore, a density of four du/ac is identified. For the areas further south and east, a density of six du/ac is identified.

Urban Industrial identifies industrial designations within the UGA and is based on the various light industrial, heavy industrial and industrial park designations. In the Lake Stevens UGA, the implementing zoning is limited to Business Park and Heavy Industrial.

Public/Institutional Use can be applied to existing or planned public and privately owned and/or operated properties including churches, schools, parks, government buildings, utility plants, and other government operations or properties within the UGA. Areas presently zoned for this use in the Lakes Stevens UGA are contained within the R-20,000 zone.

Rural Residential requires a minimum lot size of five acres for one dwelling unit except in the rural/urban transition overlay area (RUTA), where a rural cluster subdivision may be allowed. This designation allows rural cluster subdivisions the option of redeveloping required open space tracts upon inclusion in a UGA. This area can include Rural Business development.

Agriculture includes around the UGA boundary designated for a range of

land-resource based uses. Table 3-3 lists the approximate gross acreage within the service and additional study areas, by similar zoning district. This data is presented to demonstrate the relative areas identified by zoning district.

TABLE 3-3 UGA and Study Area Zoning District Acreage

Zoning District City of Lake

Stevens

County Inside UGA

Marysville /County in Svc. Area

County Outside Service

Area

Gross Total

High Urban Residential 588 588 Multifamily Residential 137 137


Zoning District City of Lake

Stevens

County Inside UGA

Marysville /County in Svc. Area

County Outside Service

Area

Gross Total

Multifamily Development Agreement

80 80

Suburban Residential 1,501 1,501 Urban Residential 1,977 1,977 Waterfront Residential 256 256 Mixed Use 15 15 Mixed Use Neighborhood 71 71

Main Street 33 33 Public/Semi-Public 404 404 Commercial (inc. NC, CBD, PBD, LB, BD, CD and NB)

442 442

Industrial (GI, GIDA and LI) 141 141

R-7,200 793 793 R-9,600/PRD-9.600 321 321 R-20,000 88 88 Mobile Home Park 0 0 Low Density Multiple Residential 10 10

Business Park 24 24 Heavy Industrial 62 62 Marysville - R6.5 10 10 Rural Residential-5 38 38 RUTA - north and east of UGA 3,188 3,188

RUTA - south of UGA 2,223 2,223 Total 5,645 1,298 48 5,411 12,402

(1) Gross total does not match total in Table 2-1 due to some areas mapped as right of way and excluded in this table's supporting data.

POPULATION To evaluate the wastewater system’s existing facilities and to determine requirements for future facilities, the study area’s existing and future population has been estimated


and is used to project future wastewater flows. As seen in the following discussion of population, the population growth rate within the District’s sewer service area has exceeded the predicted growth rate in virtually every report since the District was formed in 1957. HISTORICAL POPULATION The Lake Stevens Sewer District was formed in 1957 due to water quality problems in Lake Stevens. Since that time, the District has completed several planning documents in order to provide effective treatment to new and existing development in the area. Predicting population is difficult due to many variables, which cannot be controlled, but determining trends and extrapolating these trends to estimate future populations can be useful. Table 3-4 compares past population predictions with actual previously estimated population since 1981. The source of the predicted information varies and is identified in the footnotes of the table. The estimated population data is provided by Snohomish County. It should be noted that the “study area” and UGA during these years has not remained the same for every population projection or engineering study. In general, however, these areas have been similar in size and location. Variations in the projections can be attributed to increased growth, changing densities, revisions of study area and UGA boundaries, and other demographic changes. An “A” next to the data in Table 3-4 indicates an actual population estimate at that time; whereas a “P” estimates a previous prediction of future population.

TABLE 3-4

Lake Stevens UGA Historical and Predicted Population

Year

Actual Population

(1)

LSSD WFP

2006(2)

Snoho 2001 & 2006

LSSD 1998(5)

Snoho 1995(6)

LSSD 1983(7)

1981 9,600 9,600-A 1992 14,284 14,284-A 14,284-A(4) 14,284-A 14,284-A 1997 21,605 21,605-A 20,826-A(4) 20,037-P 1999 23,060 23,060-A 23,060-A(4) 2000 24,432 19,000-P 2002 26,828 26,828-A(3) 2007 29,898 27,592-P 2011 33,218-A(8) 2012 33,676-A(9) 30,882-P 30,882-P(4) 31,943-P 26,090-P 2013 34,186-A(9) 2014 34,477-A(9) 2025 46,125-P(3) 2028 40,258-P

Buildout 68,222-P 30,800-P


An “A” next to the data indicates an actual population estimate at that time; whereas a “P” indicates a previous prediction of future population. (1) Estimated population from Snohomish County and City of Lake Stevens (1981-2007). (2) Lake Stevens Sewer District Wastewater Facilities Plan, 2006. (3) Snohomish County GMA Comprehensive Plan, General Policy Plan, February 1, 2006. (4) Snohomish County GMA Comprehensive Plan, Lake Stevens UGA Plan, 2001. (5) Lake Stevens Sewer District Sanitary Sewer System Comprehensive Plan, 1998. (6) Snohomish County GMA Comprehensive Plan, General Policy Plan, 1995. (7) Comprehensive Plan and Engineering Report for Lake Stevens Sewer District, 1983. (8) 2012 Buildable Lands Report for Snohomish County, adopted June 12, 2013 (9) Snohomish County Tomorrow, 2013-2014 Growth Monitoring Report, October 22, 2014.

EXISTING POPULATION The most current population estimate has been provided by the Snohomish County 2012 BLR adopted in June 2013 and the County’s GMR, October 22, 2014. The most recent estimate is for 2014 and identifies a population in the Lake Stevens UGA of 34,477. The sewer service area and the UGA are essentially the same – except for one plat outside the UGA (Valterra) and a plat (Ridgewood Park) in the Marysville UGA and in the District boundary, served by the District since at least 1999. The plat of Valterra was developed and included in the sewer service area in late 2010, and therefore is included in the sewer service area for this Plan. There are about 80 single-family residential lots in this plat. The plat of Ridgewood Park includes 28 single-family residential lots. For discussion purposes, it is assumed that both of these plats outside the Lake Stevens UGA are fully developed and 108 ERUs are already served by the District. The additional population for these two areas is accounted for in the following review of population in the Lake Stevens UGA. Household Size Household size or density is used to relate population to sewer connection units. The City of Lake Stevens previously reported an increase in average household size from 2.91 in 1990 to 2.96 in 2000. This contrasts with the majority of Snohomish County, which experienced a decrease in average household size from 2.68 to 2.65 during the same period. However, considering the rapid drop in the County from 1970 (3.22) to 1980 (2.76) to 1990 (2.68), it appears this trend may be slowing. The average household size in the UGA in 2011 was 2.705 persons, per County estimates of population and total housing units. The UGA population and housing targets for year 2035 as adopted by the County (Appendix D, current Comprehensive Plan) anticipate this average will drop to 2.68. The average for the City portion of the UGA is anticipated to be about 2.64 and for the unincorporated portion of the UGA a density of about 2.90 is anticipated. For the purposes of this Plan, a household size of 2.70


persons has been selected for the existing and future population and related flow estimates, for the entire UGA and sewer service area. The City’s 2015-2035 Comprehensive Plan is based on a current average household density, in the City, of 2.87. This is based on data provided by the State Office of Financial Management for years 2014 and 2015. That data appears to include the impact of an occupancy factor that averages just less than 95% for all types of residential units. Existing Population Connected to Sanitary Sewer Based on 2.70 persons per household, if the population of the District’s residential connections in the UGA (11,134 residential ERUs on December 31, 2014, less 108 outside the UGA) is subtracted from the 2014 UGA population estimated by the County (34,477), there were 29,823 people served by the District in the UGA at the end of 2014, and 4,654 people not served within the UGA, or about 1,721 ERUs. See Table 3-5 for further details of the historical population based on residential service connections. From 2010 to 2014, the annual average growth of Residential ERUs was 1.59% or an average of 169 additional ERUs per year. The annual rate of growth for the same period for all ERUs served by the District was 1.87% or an average of 213 additional ERUs per year.

TABLE 3-5 UGA Population Based on Residential Service Connections

Year Res. Service

Connections(1) Additional

ERUs Served

Population(2) Unserved

Population Total

Population 2002 7,412 N/A 21,576 5,252 26,828 2003 7,507 95 21,852 5,252 27,104 2004 7,754 247 22,568 5,252 27,820 2005 7,889 135 22,959 5,252 28,211 2006 8,742 853 25,433 5,252 30,685 2007 8,984 242 24,300 5,598 29,898 2008 9,300 316 25,155 5,509 30,664 2009 10,140 840 27,427 3,932 31,359 2010 10,352 212 28,000 4,930 32,930 2011 10,433 81 28,219 4,999 33,218 2012 10,691 258 28,917 4,759 33,676 2013 10,859 168 29,372 4,814 34,186 2014 11,026 167 29,823 4,654 34,477


(1) Service connections/ERUs on December 31 of year shown. Excludes 28 ERUs in Ridgewood Park beginning prior to 2002 and excludes 80 ERUs in Valterra beginning in 2011.

(2) Based on 2.9 persons per dwelling through 2006 and 2.705 thereafter. SCHOOLS The Lake Stevens School District serves essentially all of the Lake Stevens UGA, Sewer District service area and sewer additional study area. The only exception is that a small area in the southeast part of the UGA, and adjacent RUTAs are served by the Snohomish School District. The Lake Stevens School District has 12 schools and serves a student population of about 7,815 as of October 2014. Each school facility and its respective population are listed in Table 3-6. Enrollment increased by 56 students (0.7%) from 2013-2014 and is expected to reach 8,331 by year 2019 (about 1.3% annual growth) and 10,656 by year 2035 (37% over year 2013 population, or about 1.55% annually). The District completed its most recent Capital Facilities Plan in August 2014, with a focus on the following six-year planning horizon. That study concluded that one new elementary school was necessary in that near-term horizon. A citizen-supported school Facilities Advisory Committee completed additional evaluations in late 2014 and early 2015 and concluded that two new elementary schools should be added, in the next ten years. Most growth pressure is in the western part of the UGA, at Hillcrest, Sunnycrest and Highland Elementary schools. The School District is searching for suitable school sites in the northwest and southwest parts of the UGA. The School District does own property on the northeast quadrant of the Soper Hill Road/State Route 9 intersection. The School District is currently developing this site to house the Early Learning Center and a new elementary school. Future uses may include an additional middle school and support services.

TABLE 3-6 School Staff and Student Population - 2014

School Staff Students Elementary Schools

Glenwood 57 537 Highland 56 630 Hillcrest 60 668 Home Link (alt. K-12) 13 101 Mt. Pilchuck 60 565 Skyline 57 467 Sunnycrest 64 682 Early Learning Center 29 60 Subtotal 396 3710 Middle Schools


School Staff Students Northlake 58 651 Lake Stevens 69 509 Subtotal 127 1160 High Schools Lake Stevens 155 1,670 Cavalero Mid-High 105 1,275 Subtotal 260 2945 Other Grounds 4 0 Maintenance 8 0 Transportation 90 0 Educational Service Center 46 0 Subtotal 148 0 TOTAL 931 7,815 (1) October 2014, Lake Stevens School District #4. (2) Figures are full time equivalents

PROJECTED FUTURE POPULATION The County predicts a linear growth rate of approximately 567 persons per year from 2014 to 2035, based on a 2035 population growth target of 46,380. The corresponding housing unit target is 17,311. Table 3-7 presents population and residential ERU projections for the UGA through the year 2035. As discussed in the Existing Population section, the 2014 UGA population is 34,477. It is assumed that about half of the presently unserved (i.e., with onsite sewage system) households will convert to sewer service at a linear rate through year 2035. This equates to about 42 existing equivalent housing units connecting to public sewer each year. This value is assumed to be net of new onsite systems, as there are a few new systems approved within the service area each year. Population growth alone equates to 567 (rounded) persons or 210 (rounded) residential ERUs per year increase. The total annual forecast increase in residential ERUs is 252. This forecast anticipates that 2,321 persons will not yet be served by public sewer (about 860 housing units) by year 2035.

TABLE 3-7 Projected UGA Population to Year 2035


Population Unserved

Residential ERUs(2)

UGA Population(3)

2014 29,823 4,654 11,026 34,477 2015 30,451 4,593 11,278 35,044



Population Unserved

Residential ERUs(2)

UGA Population(3)

2016 31,131 4,480 11,530 35,611 2017 31,811 4,366 11,782 36,177 2018 32,492 4,252 12,034 36,744 2019 33,172 4,139 12,286 37,311 2020 33,853 4,025 12,538 37,878 2021 34,533 3,912 12,790 38,445 2022 35,213 3,798 13,042 39,011 2023 35,894 3,684 13,294 39,578 2024 36,574 3,571 13,546 40,145 2025 37,255 3,457 13,798 40,712 2026 37,935 3,344 14,050 41,279 2027 38,615 3,230 14,302 41,846 2028 39,296 3,117 14,554 42,412 2029 39,976 3,003 14,806 42,979 2030 40,657 2,889 15,058 43,546 2031 41,337 2,776 15,310 44,113 2032 42,017 2,662 15,562 44,680 2033 42,698 2,549 15,814 45,246 2034 43,378 2,435 16,066 45,813 2035 44,059 2,321 16,318 46,380

(1) Current ERUs used to calculate population for 2014 in UGA (excludes 80 ERUs in Valterra and 28 in Ridgewood Park, both outside the UGA).

(2) Begin conversion of unserved customers to sewer service in 2015 at about 48 ERUs (rounded) per year. Excludes 108 ERUs outside of UGA.

(3) County growth rate of 567 (rounded) persons/year used to calculate UGA population from 2015-2035.

(4) All population and ERUs count assumed at end of year, all within

UGA. (5) Assume all population growth will be served by sewer. (6) Some ERU totals are high or low by one ERU due to fraction in

annual population increase. The unsewered population and existing onsite sewer system estimate developed in this chapter are different from those reported in Chapter 2. The County GIS onsite system data summarized in Chapter 2 may be overstated. The conversion rate from septic to sewer is based on the data analysis presented in this chapter, based on a review of ERUs, current population and average household density.


SEWER CONNECTIONS Lake Stevens Sewer District keeps records for billing or other purposes based on equivalent residential units (ERUs). Each residential unit, whether a detached single family residence, or a multi-family unit are counted as one ERU, and billed a monthly sewer service rate. Other types of connected land uses, such as commercial and industrial are allocated ERUs based on monthly water use. For every 900 cubic feet of water used per month an ERU (prorated based on actual use) is assigned. All non-residential properties are allocated a minimum of one ERU. Employment data can be used to estimate the rate of growth of commercial connections in the UGA. The actual rate will likely be variable, depending on the mix of business types, water uses in those businesses and economic conditions. The 2012 BLR identifies a year 2011 employment level of 4,003 persons in the UGA and the County has adopted a year 2035 target employment of 7,821 persons. District ERU commercial records were compared to the employment levels for years 2008 through 2011. The average ratio of ERUs to employees is about 0.21:1. Applying the annual rate of growth of employees to commercial ERU count and the increase based on the average ratio yields about the same amount of total additional commercial ERUs. Based on those results, the forecast is based on an annual increase of 3.0 percent, yielding 495 additional commercial ERUs by year 2035. CURRENT SEWER SERVICE CONNECTIONS AND ERUS While the number of non-residential ERUs varies monthly, depending on water use and growth, the number of residential ERUs increases every month as the area continues to grow. The baseline for projection of future ERUs served by the District is connection data for the year 2014. The District served 11,134 residential ERUs at year-end and an annual average of 854 ERUs for commercial connections. The total number of commercial accounts at the end of 2014 was 162. Table 3-8 presents current and projected ERUs. The growth of commercial (non-residential) ERUs is estimated to be 3.0 percent annually.

TABLE 3-8 Projected ERUs to Year 2035



2014 11,134 854 11,988 2015 11,386 880 12,266 2016 11,638 906 12,544 2017 11,890 933 12,823 2018 12,142 961 13,103




2019 12,394 990 13,384 2020 12,646 1,020 13,666 2021 12,898 1,050 13,948 2022 13,150 1,082 14,232 2023 13,402 1,114 14,516 2024 13,654 1,148 14,802 2025 13,906 1,182 15,088 2026 14,158 1,218 15,376 2027 14,410 1,254 15,664 2028 14,662 1,292 15,954 2029 14,914 1,331 16,245 2030 15,166 1,370 16,536 2031 15,418 1,412 16,830 2032 15,670 1,454 17,124 2033 15,922 1,497 17,419 2034 16,174 1,542 17,716 2035 16,426 1,589 18,015

(1) Residential ERU counts for 2014 are December values. See Table 3-7 for residential ERU projections. Values here include Valterra and Ridgewood Park connections outside the UGA. (+108 ERUs)

(2) Commercial counts for 2014 are annual average. Commercial includes schools. Commercial growth is anticipated to increase at 3.0% annually.

(3) Some ERU totals are high or low by one ERU due to fraction in annual population increase.

Downtown Subarea Plan As indicated in Chapter 1, the City will begin work on a subarea plan for Downtown Lake Stevens. This effort will build on and refine concepts considered since 2005 and reflected in a 2010 economic development study. However, there is presently no adopted basis for land use and sewer discharges for the Downtown area, other than current land use and zoning. In support of development of this Plan, City and District staff coordinated in the preparation of an informal, preliminary and non-binding estimate of potential future land uses in the Downtown area. The draft Downtown Framework Plan concept produced as a result of public outreach in 2012 by the City was used as the outline, with areas


generally identified for commercial, retail, residential, public/civic, greenspace and parking. Two thresholds of development were identified: within 10 years, and from 11 to 20 years. The area was divided into three smaller areas as follows:

North of 20th, including the area between 123rd and Hartford, along Grade Road

East of Main Street, south of 20th West of Main Street, south of 20th

District staff documented current development (early 2015) including building square footage and number of sewer ERUs for each area. The total current ERU count is 137. City staff identified potential future land uses anticipated by year 2025 and year 2035, with approximate building square footage. Many of the current development and structures in the immediate downtown area are anticipated to be redeveloped. A preliminary estimate of ERUs for each future land use was made, suggesting 210 new ERUs within 10 years and an additional 332 ERUs within 20 years. That development was estimated to take the place of a total of 125 current ERUs, suggesting an approximate future ERU count of 417 for the downtown subarea. Buildout Population Population projections presented in Table 3-7 address current and future population for the existing Lake Stevens UGA, through the planning horizon. The 2007 Plan included discussion and consideration of impacts of a “buildout” population for the UGA. That buildout population was nearly twice the population estimated by the County, for year 2025. With the impact of the recent recession, the UGA target population is essentially the same for 2035, ten years later. In the context of the detailed analysis of the likely available land for new development, under current land use designations and zoning, on a parcel by parcel basis, it is not reasonable to plan for population in the UGA at a level greater than the capacity identified in the County 2012 BLR. It is recognized that the UGA boundary can be expanded in the future and that the City and County could allow densities higher than presently planned within the current UGA, with future land use actions or comprehensive plan updates. Therefore it remains prudent to include a reasonable contingency in analysis and design of sewer conveyance and treatment facilities. That contingency will be addressed in Chapter 4, Design and Planning Criteria, Chapter 6, Collection System Evaluation, and Chapter 7, Capital Improvement Program, in the form of sewer flow and loading criteria and selection of capital improvement project sizes. It is also recognized that the target population or anticipated number of sewer connections (Table 3-8) may be reached before or after year 2035. As noted above, the recent annual rate of sewer connections is about 213 ERUs, whereas the forecast annual rate of ERU increase is about 287 (35% higher), based on the County adopted targets for population and employment growth, with some onsite sewer system conversions to public sewer. Therefore it is prudent for the financial analysis in Chapter 9 to consider more than one growth rate scenario.


Potential RUTA Population The additional study area includes over 5,400 acres of land presently designated as Rural, with most of the area zoned as R-5. There is a small area of Rural Business and three existing planned residential developments (PRDs) which include smaller lots and open space areas. This unincorporated area is presently designated by the County as a rural/urban transition overlay area (RUTA). This area abuts the UGA and is situated as the likely area of future expansion of the UGA. To prepare an order of magnitude estimate of the potential future population of the additional study area, assuming it was all designated as Urban land, the gross residential density of the current UGA was considered for reference. With a population capacity of 46,634, a gross UGA area of 6,977 acres and a household or ERU density of 2.70, the UGA residential development density is approximately 2.48 units per acre. (This is a gross density, over all lands in the UGA, including rights of way, commercial land, etc., and is not a reflection of density as considered by the GMA.) The present UGA includes several commercial land use areas and those areas are likely a higher share of the area than will be necessary in the additional study area. With a higher share of the area dedicated to residential development, the gross density will likely increase. For purposes of this review, a gross density of 2.6 units per acre is used (about five percent higher than current UGA) to estimate the future population of the RUTA area in the additional study area, under Urban development conditions. The actual future population potential (under Urban land use designation) is a function of numerous variables and factors, including existing platted parcels, rights of way critical areas, local business, parks and related matters all impacting land area available for development. Applying a gross density of 2.6 units to the acre, the potential fully developed and sewered population of the additional study area is nearly 38,000 people (about 82 percent of the target population for the current UGA). Assuming a combined rate of growth and connection to the sewer system of about 800 persons per year (just over the rate of growth forecast in the UGA), it would take an additional 47 years to achieve that additional sewered population.

CITY

RR/5

RCF

CITY

RR/5BASIC

RR/5BASIC

CITY

LAKE

ULDR

RCF

RR/5BASIC

RR/5BASIC

RR/5

ROW

ULDR

RR/5BASIC

RR/5BASIC

ULDR

UI

RCF

ULDR

ULDR

UI

RR/5BASIC

ULDR

ULDR

RCF

ULDR

UMDR

RCF

CITY

P/I

ULDR

RI

UCOM

ULDR

ULDR

RI

ULDR

CITY

UMDR

UCOM

UMDR

CITY

RR/5BASIC

ULDR

ULDR

RR/5BASIC

UCOM

RR/5BASIC

UMDR

ULDR

ROW

ULDR

MDR

MDR

MDR

GI

MDR

MDR

MDR

HDRMDR

COM

MDRWR

WR

LI

MDR

MDR

MDR

MDR

MDR

MDR

WR

P/SP

MFR

HDR

MFDA

COM

MDR

COM

MDR

MDR

MFR

COM

PBD

P/SP

MDR

LC

P/SP

WR

COM

P/SP

COMMU

MU

P/SP

MDR

P/SP

HDR

PBD

HDR

MDR

P/SP

MDR

HDR

MDR

MU MDR

P/SP

MU

P/SP

MU

COM

P/SP

P/SP

P/SP

HDR

MU

LC

P/SP

P/SP

MFRMDR

P/SP

LC

P/SPPBD

WR

P/SP

P/SP

MFR

MFR

COMMDR

MDR

MU

HDR

LC

COMP/SP

GIDA

MU

P/SPLC

MDR

P/SP

MFDA

MFR

COM

HDR

P/SP

P/SP

MFR

P/SP

MU

MDRP/SP

LC

P/SPP/SP

P/SP

P/SP

LegendCITY OF LAKE STEVENSSERVICE AREADISTRICT BOUNDARY

City Land Use 2014COMGIGIDAHDRLCLIMDRMFDAMFRMUP/SPPBDWR

Snohomish County Land UseP/IRCFRIROWRR/5RR/5BASICUCOMUIULDRUMDR


FIGURE 3-1LAND USE

NTS £

Lake S

tevens

UR

SR

SR

SR

UR

UR

SR

GI

CD

SR

SR

HUR

SR

UR

WR

WR

LI

UR

CD

CDBD

UR

HUR

HUR

BD

UR

CD

WR

P/SP

UR

HUR

MFDA

HUR

NB

MS

PBD

P/SP

UR

P/SP

WR

P/SP

HUR

P/SP

P/SP

CBD

HUR

PBD

HUR

CD

HUR

HUR

P/SP

HUR

HUR

MUN

MUN

P/SPP/SP

CD

CD

MU

URCD

P/SP

NB

P/SP

P/SP

HUR

MUN

LB

P/SP

P/SP

P/SP

BD

LB

P/SPPBD

WRCD

P/SP

MUN

P/SP

HUR

HUR

MU

HUR

LB

MUN

P/SP

GIDA

CD

P/SPLB

HUR

P/SP

CD

MFDAMUN

UR

HUR

P/SP

P/SPP/SP

P/SP

LB

MUNP/SPP/SP

P/SP

P/SP

R-5

R-5

A-10

City

R-5

R-7,200

R-5

A-10

HI

R-9,600

R-7,200

PRD SA-1

R-7,200

City

R-20,000

BP

LDMR

MC

R-7,200

R-9,600

R-7,200

R-9,600(PRD)

BP

F and R

PRD SA-1

PRD-7,200

RI

RI

PCB

R-20,000

R-7,200

PRD SA-1

R-9,600

F and R

R-7,200

R-7,200

RB

R-9,600

R-7,200

R-9,600

MHP

LDMR

LDMR

R-9,600(PRD)

R-5

PRD-9,600

R-9,600

RC

RB

R-9,600

PRD-9,600

R-7,200

R-9,600

LDMRR-7,200

Marysville

City LegendCITY OF LAKESTEVENSSERVICE AREADISTRICTBOUNDARYMARYSVILLE UGA

City Zoning 2014Business DistrictCentral BusinessDistrictCommercial DistrictGI DevelopmentAgreementGeneral IndustrialHigh UrbanResidentialLight Industrial

Local BusinessMF DevelopmentAgreementMain Street

Mixed UseMixed-UseNeighborhoodMulti-FamilyResidentialNeighborhoodBusinessPlanned BusinessDistrictPublic / Semi-PublicSuburban Residential

Urban ResidentialWaterfront Residential


FIGURE 3-2ZONING

NTS £

County LegendSnohomish Co ZoningDESCRIPTAgriculture

10 AcreBusiness ParkCityForestry andRecreationHeavy IndustrialLow DensityMultipleResidentialMineralConservationMobile HomeParkPlannedCommunityBusinessResidential20,000 sq. ft.Residential7,200 sq. ft.Residential9,600 sq. ft.Rural BusinessRuralConservationRural IndustrialRural-5 AcreSuburbanAgriculture-1 Acre

Lake S

tevens

CH

APTE

R 4

– D

ESIG

N A

ND

PLA

NN

ING

CR

ITER

IA


CHAPTER 4

DESIGN AND PLANNING CRITERIA INTRODUCTION Adequate design of wastewater treatment and conveyance facilities requires the determination of the quantity and quality of wastewater generated from each of the contributing sources. Typically, wastewater is predominantly domestic in origin with lesser amounts contributed by commercial and industrial businesses and by public use facilities such as schools, parks, hospitals, and municipal functions. Infiltration and inflow (I/I) contributions result from groundwater and surface water entering the sewer system during periods of high groundwater levels and rainfall, respectively. DEFINITION OF TERMS In this chapter, the existing wastewater characteristics for the service area are analyzed and projections made for future conditions. The terms and abbreviations used in the analysis are described below. AMMONIA The Washington State Department of Ecology (DOE) issued a Total Maximum Daily Load (TMDL) Study for the Snohomish River Estuary and included total ammonia nitrogen as a pollutant of concern. Total ammonia, like BOD, exerts an oxygen demand that affects dissolved oxygen levels in the river. Total ammonia includes un-ionized ammonia (NH3) and ammonium ion (NH4

+). Ammonia in its un-ionized state can be toxic to fish. The District’s NPDES prior permit, for the previous WWTP, contained a seasonal mass limit for total ammonia (as NH3-N). Total ammonia was expressed as a concentration in terms of milligrams per liter (mg/L) and as a mass load in terms of pounds per day (lb/day). For the new WWTF NDPES permit, and its Outfall #2 located upstream of the original WWTP Outfall #1, ammonia is addressed in a combined parameter called “NBOD + CBOD”, expressed in lb/day. NBOD is calculated as 2.1 times Ammonia (lb/day). This parameter is monitored from July through October annually. AVERAGE ANNUAL FLOW Average Annual Flow (AAF) is the average daily flow over a calendar year. This flow parameter is used to estimate annual operation and maintenance costs for treatment and pump station facilities. AVERAGE DRY WEATHER FLOW


Average Dry Weather Flow (ADWF) is wastewater flow during periods when the groundwater table is low and precipitation is at its lowest of the year. The dry weather flow period in western Washington normally occurs during July through September. During this time, the wastewater strength is highest, due to the lack of dilution with the ground and surface water components of infiltration and inflow. The higher strength coupled with higher temperatures and longer detention times in the sewer system create the greatest potential for system odors during this time. The average dry weather flow is the average daily flow during the three lowest consecutive flow months of the year. For this study, average daily flows for July, August, and September are used. BASE FLOW Base Flow is a measure of the sanitary wastewater flow. It considers the sanitary sewer portion of the wastewater flow only, without infiltration and inflow. The base flow includes both domestic and non-residential flows. BIOCHEMICAL OXYGEN DEMAND (BOD) Biochemical Oxygen Demand (BOD) is a measure of the oxygen required by microorganisms in the biochemical oxidation (digestion) of organic matter. BOD is an indicator of the organic strength of the wastewater. If BOD is discharged untreated to the environment, biodegradable organics will deplete natural oxygen resources and result in the development of septic (anaerobic) conditions. BOD data together with other parameters are used in the sizing of the treatment facilities and provide a measurement for determining the effectiveness of the treatment process. BOD is expressed as a concentration in terms of milligrams per liter (mg/L) and as a load in terms of pounds per day (lb/d). The term BOD typically refers to a 5-day BOD, often written BOD5, since the BOD test protocol requires five days for completion. The total BOD5 of wastewater is composed of two components – a carbonaceous oxygen demand (CBOD5) and a nitrogenous oxygen demand (NBOD5). The use of CBOD5 as a parameter for evaluating wastewater strength removes the influence of nitrogenous components, including ammonia and organic nitrogen. The NPDES permit for the District WWTF includes effluent limits expressed in terms of CBOD5, and influent limits expressed in terms of BOD5. CHLORINE Chlorine is a chemical element that acts as a strong oxidant when exposed to certain components of organic matter. Chlorine is widely used as a disinfectant in wastewater treatment, and is available both in gaseous (elemental chlorine) and solution forms (hypochlorite). Chlorine is a toxic chemical and is lethal to aquatic biota if present in too high a concentration. Additionally, some organic constituents may react with the chlorine to interfere with chlorination or form toxic compounds, such as chloroform. This can have a long-term adverse effect on the beneficial uses of the waters to which they


are discharged. To minimize the effects of potentially toxic chlorine residuals on the environment, it has sometimes been found necessary to dechlorinate wastewater treated with chlorine or substitute alternative disinfection systems such as ultraviolet disinfection. The new WWTF does not include chlorine in the treatment process. Sodium hypochlorite is used in select process areas for cleaning of the membranes and for the process water system. DOMESTIC WASTEWATER Domestic Wastewater is wastewater generated from single and multi-family residences, permanent mobile home courts, and group housing facilities such as nursing homes. Domestic wastewater flow is generally expressed as a unit flow based on the average contribution from each person per day. The unit quantity is expressed in terms of gallons per capita per day (gpcd). The Domestic Wastewater and Non-Domestic Wastewater together comprise the Base Flow. EQUIVALENT RESIDENTIAL UNIT (ERU) An Equivalent Residential Unit (ERU) is a baseline wastewater generator that represents the average single family residential household. An ERU can also express the average annual flow contributed by a single-family household, in units of gallons per day, or an annual average loading (of 5-day BOD or TSS) contributed by a single-family household, in units of pounds per day. INFILTRATION Infiltration is groundwater entering a sewer system by means of defects in pipes, pipe joints or manhole walls. Infiltration quantities exhibit seasonal variation in response to groundwater levels. Storm events or irrigation trigger a rise in the groundwater levels and increased infiltration. The highest infiltration is observed following significant storm events or prolonged periods of precipitation. Since infiltration is related to the total amount of piping and appurtenances in the ground and not to any specific water use component, it is generally expressed in terms of the total land area being served1. The unit generally used is gallons per acre per day (gpad). INFLOW Inflow is surface water entering the sewer system from yard, roof and footing drains, from cross connections with storm drains and through holes in manhole covers. Peak inflow occurs during heavy storm events when storm sewer systems are taxed beyond their capacity, resulting in hydraulic backups and local ponding. Inflow can be expressed in terms of gallons per capita per day or gallons per acre per day (gpad). 1 See additional discussion of the basis of the area for expressing infiltration and/or inflow under the section “Infiltration and Inflow” prior to Table 4-5.


WWTF flow records are utilized to characterize combined infiltration and inflow in the District’s system in terms of peak hour, peak day, maximum month, dry weather and average annual I/I. MAXIMUM DAY FLOW Maximum Day Flow (MDF) is the highest flow occurring during a one day period in a calendar year. In Western Washington, the maximum day flow typically occurs in the winter due to the presence of more I/I. This winter high flow is composed of the normal domestic, commercial, and public use flows with significant contributions from inflow and infiltration. The maximum day flow at the end of the design period is used to design some wastewater treatment processes. MAXIMUM MONTH FLOW (TREATMENT DESIGN FLOW) Maximum Month Flow is the highest monthly flow during a calendar year. In Western Washington, the maximum month flow occurs in the winter due to the presence of more I/I. This winter high flow is composed of the normal domestic, commercial and public use flows with significant contributions from inflow and infiltration. The predicted maximum month flow at the end of the design period is used as the design flow for sizing treatment processes and selecting treatment equipment. NON-DOMESTIC WASTEWATER Non-Domestic Wastewater is wastewater generated from business activities, such as restaurants, retail and wholesale stores, service stations, office buildings, and industrial operations. Non-Domestic wastewater quantities are expressed in this Plan in terms of equivalent residential units (ERUs). OTHER CONTAMINANTS OF CONCERN Other contaminants of concern in wastewater include nutrients, priority pollutants, heavy metals, dissolved organics, and endocrine disrupting chemicals. The District’s NPDES permit requires the removal of biodegradable organics (CBOD5), ammonia, suspended solids and pathogens. Nutrients such as ammonia, other forms of nitrogen and phosphorus, along with carbon, are essential requirements for growth. When discharged to the aquatic environment, these nutrients can lead to the growth of undesirable aquatic life. When discharged in excessive amounts on land, they can also lead to the pollution of groundwater. Additionally, in too high a concentration, nutrients, particularly ammonia, can be toxic to aquatic life. PEAK HOUR FLOW Peak Hour Flow (PHF) is the highest hourly flow during a calendar year. The peak hour flow in Western Washington treatment facilities usually occurs in response to a


significant storm event preceded by prolonged periods of rainfall, which have previously developed a high groundwater table in the service area. Peak hour flows are used in sizing the hydraulic capacity of wastewater collection, treatment and pumping components. Peak hour flow is typically determined from treatment plant flow records and used to estimate future flows. DOE’s Orange Book also provides a method shown in its Figure C1-1 based on a ratio of peak hourly flow to design average flow as presented below:

Q peak hourly = 18 + square root (P) where: Q design average 4 + square root (P)

Q peak hourly = Maximum rate of wastewater flow Q design average = Design average, or average annual, wastewater flow P = Population in thousands.

The resulting peak factor shall not be less than 2.5, per DOE. PRIORITY POLLUTANTS Priority pollutants are organic and inorganic compounds selected on the basis of their known or suspected carcinogenicity, mutagenicity, teratogenicity, or high acute toxicity. Many of these compounds are found in wastewater. Inorganic constituents, including heavy metals, are often present in wastewater due to commercial and industrial activities and may have to be removed from the wastewater if the presence of the metals will adversely affect aquatic life in the receiving water, or, if the wastewater is to be recharged to groundwater. Some heavy metals (most notably copper) can be present in wastewater due to leaching from drinking water pipes. Organic priority pollutants include volatile organic compounds (VOCs) and organic pesticides, herbicides, and other agricultural chemicals. VOCs are organic compounds that have a boiling point less than 100 degrees C and/or a vapor pressure greater than 1 mm Hg at 25 degrees C. VOCs include vinyl chloride, benzene, and toluene and are a particular concern to the health of collection and treatment system employees. Pesticides and agricultural chemicals are not common constituents of domestic wastewater, but result primarily from surface runoff from agricultural and park lands. SUSPENDED SOLIDS Suspended Solids is the solid matter carried in the waste stream. The Total Suspended Solids (TSS) in a wastewater sample is determined by filtering a known volume of the sample, drying the filter paper and measuring the increase in weight of the filter paper. TSS is expressed in the same terms as BOD; milligrams per liter for concentration and pounds per day for mass load. The amount of TSS in the wastewater is used in the sizing of treatment facilities and provides another measure of the treatment effectiveness. The concentration of TSS in wastewater affects the


treatment facility biosolids production rate, treatment and storage requirements, and ultimate disposal requirements. WASTEWATER Wastewater is waste-carrying water from residential, business and public use facilities, together with quantities of groundwater and surface water which enter the sewer system through defective piping and direct surface water inlets. The total wastewater flow is quantitatively expressed in millions of gallons per day (mgd). EXISTING WASTEWATER FLOWS AND LOADING WWTP and WWTF records for the three-year period from January 2012 through December 2014 have been reviewed and analyzed to determine current wastewater characteristics and influent loadings. Current wastewater flows and loadings are used in conjunction with projected population data to determine projected future wastewater flow and loading rates. This data includes the last four months of operation of the WWTP (January through April, 2012) and data from the WWTF startup in April 2012 through December 2014. HISTORICAL WASTEWATER FLOWS AND LOADINGS Table 4-1 summarizes WWTF influent flows for the three-year period. The reported monthly average influent flows ranged from 1.58 mgd to 3.61 mgd in September 2012 and December 2012, respectively. The ratios of the various rates are summarized below the table.

TABLE 4-1 WWTF Influent Flows (2012-2014)

Flow Flow Rate (mgd)

Average Dry Weather Flow(2) 1.96 Annual Average Flow 2.50 Maximum Month Flow(3) 3.61 Peak Day Flow(4) 5.90 Peak Hour Flow(5) 6.25 Highest Measured Peak Hour Flow(6) 7.68 (1) Based on DMRs reporting WWTP influent (2) Average of July, August, September, 2014 (3) Reported for December, 2012 (4) Reported for January 29, 2013 (5) Calculated using DOE’s Orange Book Figure C1-1: Q peak hourly = 18 + square root (P) = 18 + 5.7 = 2.44


Q design average 4 + square root (P) = 4 + 5.7 Where P = 32,368 population equivalents served ( in 1,000s) (11,998 ERUs served December 2014 x 2.70 persons / ERU) (Peak factor shall be a minimum of 2.5) Peak Hour Flow = 2.50 mgd x 2.5 = 6.25 mgd (6) Actual highest PHF measured - November 19, 2012 (actual peak factor is approximately 3.07`) (7) Ratios:

Max. Month : Annual Average 1.45:1 Peak Day : Annual Average 2.36:1

Monthly discharge monitoring report (DMR) data for this period are summarized in Table 4-2. Graphical representations of average monthly WWTF flows, influent BOD5 and TSS loadings, effluent CBOD5 concentrations and effluent CBOD5 mass for the period from January 2012 through December 2014 are shown in Figures 4-1, 4-2, and 4-3, and 4-4, respectively.

TABLE 4-2 Summary of Discharge Monitoring Reports (DMRs)

WWTF Influent and Effluent Monthly Averages

Flow(1) Influent Effluent Avg. Peak BOD5 TSS CBOD5

Month - Year

mgd Day mgd

mg/L avg.

lb/d avg.

mg/L avg.

lb/d avg.

mg/L avg.

mg/L peak wk

Jan-12 2.61 4.31 251 4,882 216 4,607 4.83 6.63 Feb-12 2.86 4.31 221 5,045 198 4,611 5.58 6.10 Mar-12 3.07 3.93 196 4,863 180 4,565 5.11 5.97 Apr-12 2.28 3.34 328 3,988 230 3,775 5.83 11.67 May-12 2.14 2.84 382 6,957 228 4,121 0.65 0.78 Jun-12 2.14 2.75 312 5,493 221 3,919 0.46 0.68 Jul-12 1.78 2.12 350 5,299 278 4,176 0.55 0.59 Aug-12 1.59 1.73 340 4,512 294 3,902 0.62 0.68 Sep-12 1.58 1.82 391 5,163 377 5,007 2.40 3.00 Oct-12 1.79 2.90 362 5,169 299 4,309 1.57 3.00 Nov-12 3.09 5.58 211 5,233 180 4,443 0.74 2.10 Dec-12 3.61 5.09 172 5,138 154 4,630 0.27 0.39 Jan-13 3.23 5.90 196 5,124 181 4,835 0.31 0.40 Feb-13 2.83 3.40 263 5,889 261 5,750 0.85 2.03 Mar-13 2.89 4.02 217 5,364 227 5,525 0.46 0.62


Flow(1) Influent Effluent Avg. Peak BOD5 TSS CBOD5

Month - Year

mgd Day mgd

mg/L avg.

lb/d avg.

mg/L avg.

lb/d avg.

mg/L avg.

mg/L peak wk

Apr-13 2.81 4.06 265 5,688 227 4,948 0.52 0.58 May-13 2.32 2.55 333 6,440 303 5,891 0.70 1.45 Jun-13 2.25 2.64 375 7,027 333 6,182 0.61 1.24 Jul-13 2.07 2.25 381 6,411 310 5,263 0.81 2.12 Aug-13 2.03 2.21 394 6,547 321 5,353 0.79 2.12 Sep-13 2.29 2.98 333 6,221 292 5,469 2.34 3.00 Oct-13 2.25 2.66 365 6,725 288 5,384 1.59 3.00 Nov-13 2.58 3.13 326 6,880 263 5,559 1.91 3.00 Dec-13 2.53 3.68 306 6,089 260 5,222 0.95 2.12 Jan-14 2.78 4.05 300 6,883 238 5,389 0.51 1.22 Feb-14 2.84 3.57 344 7,743 214 5,046 0.47 1.26 Mar-14 3.36 5.26 236 6,477 175 4,780 0.40 0.45 Apr-14 2.71 3.15 316 7,121 260 5,851 0.49 0.75 May-14 2.57 3.36 288 6,013 254 5,273 1.59 3.00 Jun-14 2.22 2.50 337 6,054 298 5,362 0.66 0.57 Jul-14 2.10 2.44 319 5,500 285 4,927 1.41 3.00 Aug-14 2.06 2.43 319 5,490 299 5,125 0.04 0.09 Sep-14 2.10 2.41 352 6,209 312 5,435 1.60 3.00 Oct-14 2.52 4.28 328 7,111 267 5,566 1.86 3.00 Nov-14 2.96 3.94 282 6,438 224 5,366 1.19 2.11 Dec-14 3.11 4.34 241 6,147 194 4,959 1.23 3.00

Average 2.50 3.39 304 5,926 254 5,015 1.44 2.35 Max. 3.61 5.90 394 7,743 377 6,182 5.83 11.67 Min. 1.58 1.73 172 3,988 154 3,775 0.04 0.09

(1) Flow data is influent for former WWTP and effluent for new WWTF.

Data for January, February, March 2012 is for former WWTP. Data for April 2012 is for both treatment facilities.

Data for May 2012 and later is for new WWTF. Data excludes select, unusually high influent BOD and TSS data for these months:

BOD and TSS - 4/12, 5/12, 10/12, 5/13 and BOD only for 6/12, 2/13, 3/13, 1/14, 2/14. Unusually high readings are not representative due to refinements of influent sampling location at new WWTF


The three-year average concentrations for BOD5 and TSS are 304 mg/L and 254 mg/L, respectively. The annual maximum month concentration for BOD5 covers a range from 352 mg/L to 394 mg/L over the period from 2012 to 2014. Similarly, TSS concentration covers a range from 312 mg/L to 377 mg/L. Average and maximum month concentrations in these ranges is considered medium strength domestic wastewater.

The maximum month BOD5 loading shown in Table 4-2 is 7,743 lb/d, for February, 2014. As discussed below in the “Existing BOD5 Loading” section, use of this maximum month loading value yields a per capita loading value of 0.245 lb/cap/d. The maximum month TSS loading shown in Table 4-2 is 6,182 lb/d, for June 2013. As discussed below in the “Existing TSS Loading” section, use of this maximum month loading value yields a per capita loading value of 0.195 lb/cap/d. The annual average and maximum month influent BOD5 and TSS mass loading, along with annual average influent flows, for 2005 through 2014 are listed in Table 4-3.

TABLE 4-3 WWTF Flow and Loading Summary

Year

Annual Average Flow(1) (mgd)

Annual Average Influent

BOD5 (lb/d)

Annual Average Influent

TSS (lb/d)

Maximum Month Influent Influent BOD5

(lb/d)

Maximum Month

Influent TSS (lb/d)

2005 1.92 4,799 3,872 5,270 4,218 2006 2.08 4,915 3,796 5,548 4,055 2007 2.07 5,276 3,958 5,777 4,433 2008 2.13 5,117 4,299 6,044 4,735 2009 2.16 5,198 4,348 5,807 4,702 2010 2.36 5,868 5,072 7,065 5,744 2011 2.43 5,086 4,573 5,338 4,818 2012 2.38 5,145 4,339 6,957 5,007 2013 2.51 6,200 5,448 7,027 6,182 2014 2.61 6,432 5,256 7,743 5,851

Average 2.26 5,404 4,496 6,258 4,974 (1) Flow data is influent for former WWTP and effluent for new WWTF.

Data for January, February, March 2012 is for former WWTP. Data for April 2012 is for both treatment facilities.

Data for May 2012 and later is for new WWTF. Data excludes select, unusually high influent BOD and TSS data for these months:

BOD and TSS - 4/12, 5/12, 10/12, 5/13 and BOD only for 6/12, 2/13, 3/13, 1/14, 2/14.


Unusually high readings are not representative due to refinements of influent sampling location at new WWTF

EXISTING EQUIVALENT RESIDENTIAL UNITS (ERUS) To determine the per capita sewer flow for residential units with sewer service, water consumption, water billing and sewer billing records were reviewed. WINTER WATER CONSUMPTION Winter water use (consumption) can be used to estimate wastewater volumes entering the collection system because the amount of winter water use typically is equal to wastewater flow except for a minor amount of water that does not enter the sewer system (such as winter irrigation flows). This must be adjusted for seasonal water use, if used to calculate base flow. In this report, typical commercial (including commercial, industrial, and other non-residential) winter water use is subtracted from the WWTF typical dry weather flow to arrive at a base flow, including dry weather infiltration, for calculating per capita wastewater flows for residential uses only. Please note that not all commercial customers have their water consumption measured for calculating sewer charges. Therefore, this method will over-estimate the per capita sanitary sewer flows by a slight amount. Table 4-4 presents the winter water consumption in gallons per day (gpd) for commercial customers only from November 2013 through February 2014, and from November 2014 through February 2015 to establish winter water use. With an average dry weather flow of 2.11 mgd for July, August and September of 2013 and 2014, and a non-residential flow (based on wet weather commercial water use) of 117,255 gallons per day, the base flow equals approximately 1,992,745 gallons per day, or 67.3 gpcd based on an average of 10,967 residential ERUs (end of 2013)2 and 2.70 persons per ERU (see discussion in Chapter 3). Based on this analysis, non-residential flow represents approximately six percent of the total wastewater flow in the District. This per capita flow contains a small portion of year-around infiltration. The 2007 Plan performed a similar analysis and identified a per capita flow of 69 gpcd, and used a per capita flow of 70 gpcd as a somewhat conservative estimate of domestic flow. Throughout this Plan a per capita flow of 70 gpcd will continue to be used. This introduces a potential flow contingency of nearly four percent. That margin may continue to increase with continuing efforts to reduce residential water use through conservation and water use efficiency efforts.

2 See Table 3-5 and add 108 ERUs for the areas served outside the UGA.


TABLE 4-4

Winter Water Use for Commercial Customers

Month/Year Consumption

(CF) Consumption

(gpd) Nov-13 512,835 127,867 Dec-13 378,431 91,312 Jan-14 493,661 119,116 Feb-14 442,922 118,323

Average 456,962 114,154

Nov-14 479,385 128,064 Dec-14 369,588 98,733 Jan-15 476,794 127,372 Feb-15 476,347 127,253

Average 450,529 120,355

Average (both periods)

453,745 117,255

EQUIVALENT RESIDENTIAL UNITS Use of Equivalent Residential Units (ERUs) is a method to express the amount of water or sewer use by non-residential customers as an equivalent number of residential customers. The water consumption ERU value is typically calculated by dividing the total volume of water utilized in the single-family residential (SFR) customer class by the total number of active single-family residential connections. The wastewater ERU value is calculated based on winter water use. For typical wastewater collection systems, it is estimated that, depending on the system, anywhere from zero percent (negligible) to as much as 15 percent of the winter water consumption does not enter the wastewater collection system. The wastewater ERU value is calculated by dividing the winter water use for single-family residential units by the number of single-family units and multiplying by the fraction of winter water estimated to enter the sewer (0.85 to 1.00). The average daily volume of water used by other customer classes can then be multiplied by this factor and divided by the average daily single-family residential water use to determine the number of equivalent residential units consumed by other customer classes. Because the District does not track residential water use, this study did not examine residential water use via water use records. With approximately 10,967 residential ERUs receiving sewer service for end of year 2013, and 1,992,745 gallons per day estimated for dry weather residential base flow (which includes dry weather I/I), each residential unit discharges approximately 182 gallons per day of wastewater (729 cubic


feet per month). The District utilizes 900 cubic feet as a monthly ERU for non-residential customers. King County previously used 900 cubic feet but now uses 750 as the equivalency basis for commercial customers. The District should consider the impacts on water usage and commercial rate revenue associated with a change to 750 cubic feet in its next detailed rate study. INFILTRATION AND INFLOW The amount of infiltration and inflow (I/I) can be estimated on an annual average, dry weather, maximum month, and maximum day basis by subtracting the dry weather flow at the WWTF from the annual average, dry weather, maximum month, and maximum day flows at the WWTF. Peak hourly I/I flow can be calculated by use of peaking factors (either by formula or actual data), or actual peak event flow data from the WWTF. For this Plan, infiltration and inflow is expressed in units of gallons per acre per day (gpad). The area used as the basis for expression of I/I in units of gpad is not explicitly defined or readily determined. The area in which I/I is generated is a function of the geometry and condition of the sewer system, including side sewer laterals, side sewers on private property and the potential presence of inappropriate connections to the sewer system (e.g. onsite drainage basins, or roof, footing or crawlspace drains, etc.) The contribution area is also a function of local topography and soil and groundwater conditions. The same basis must be used for calculation of current I/I rates as will be used for forecasting future I/I flows to the sewer system. The 2007 Plan identified a “developed sewer service area” for calculation of then-current I/I rates. It appears such an approach may include more area than may actually contribute I/I to the pipe network, by including common areas, stormwater pond tracks, parks, etc. that are situated along the existing collection system. This Plan incorporates a modified approach that uses the area of parcels served by sewer as the basis for the I/I contribution area. The estimated area of future developed parcels is added for forecasting future I/I contributions associated with extension of the wastewater collection system.3 This area is more readily defined, for both current and future development conditions, but the approach may underestimate the I/I contribution area, as the area closest to the mainline, the public right of way in most cases, is not included in the I/I contribution area. But this area is not readily measured for the future condition. The total area of parcels served as of 2014 was 2,709 acres. This is a net area as it does not include public right of way or parcels not connected to the system (even if the

3 This modified approach to defining and measuring the I/I contribution area changes the basis used for calculation of I/I rates. The I/I rates presented in this Plan are not directly comparable to the rates presented in the 2007 Plan. Use of a smaller I/I contribution area for the same I/I value will result in a higher rate of I/I in gpad, but that should not be taken as an indication that I/I is increasing. See the I/I discussion using EPA criteria for such a comparison.


parcel is served by a sewer main along its frontage). It may include critical areas if such areas are part of the parcel that is connected to the sewer system. The corresponding density of ERUs per acre of served parcels is 4.44. The Snohomish County Buildable Lands Report (BLR, see Chapter 1) identifies the anticipated gross buildable area for all parcels in the UGA, regardless of current development status. The gross buildable area excludes land anticipated to be not suitable or available for development due to critical areas restrictions or other development constraints. The BLR estimates the total parcels area to be 6,099 acres but only 4,295 acres as available for development. These figures imply that nearly 30% of the gross area is not developable (right of way, common area, critical areas restrictions, etc.). The remaining developable land (for sewer planning purposes) is approximately 1,586 acres (4,295 less 2,709 acres served). This remaining area is a gross amount, as it includes larger parcels without allowance for future rights of way or common areas such as tracts for stormwater management facilities. Therefore this area is reduced by an estimated 15 percent for such non-sewered uses, resulting in a future additional service area (parcels only) of about 1,350 acres. Applying the ERU growth anticipated by year 2035 over this area (6,027 ERUs) results in an estimated growth area density of 4.46 ERUs/acre. This compares reasonably with the current I/I contribution area sewer connection density. The future I/I contribution area is estimated to be 4,060 acres (rounded). The rate of change is anticipated to be linear, generally consistent with the County residential population growth forecast. Table 4-5 summarizes the infiltration/inflow analysis for the three-year period 2012-2014. The data contained in this table is used as a baseline for forecasting infiltration and inflow in the future. In order to find the Base Flow, summer time flow records at the WWTP and WWTF were observed for the summer of 2013. A lowest, hourly low flow was observed on August 25, 2013 of 0.82 mgd during the early morning. It is assumed that 0.70 mgd (about 85%) of this flow represents domestic sewage flows and 0.12 mgd represents dry weather infiltration. Therefore, with a three-year dry weather flow average of 1.96 mgd, and subtracting the dry weather infiltration, the Base Flow is estimated to be 1.84 mgd. Table 4-5 presents I/I data for the total collection system based on WWTP flow data. During dry weather conditions, I/I amounts to 43 gpad. The average annual I/I contribution is 243 gpad. The Peak Hourly value of 2,156 gpad is relatively low when I/I values for systems tributary to the King County wastewater system are considered. As discussed below, a value of 1,100 gpad for peak I/I has been widely used by sewer systems in the Pacific Northwest. Extensive evaluation by King County in the 2000s revealed that many separate sewer systems in the Seattle area, all generally constructed beginning in the 1950s or later, generated several thousand or tens of


thousands of gallons per acre per day of I/I. The ratio of peak day to maximum month flow is about 1.6. The value of maximum month I/I is particularly critical, as the maximum month average daily flow is one of the primary WWTF permit limitations. Maximum month I/I is shown as 653 gpad in Table 4-5, per the historical maximum month flow of 3.61 mgd. As evident from Table 4-2 and Figure 4-1, there were six months with average daily flows exceeding 3.0 mgd. The corresponding I/I values for those six months range from 454 to 653, with an average of 519 gpad. It is clear that the December 2012 value of 653 gpad was unusually high. Therefore, the value to be used as the basis for I/I design criteria will be somewhat lower than the historical value presented in Table 4-5. A value of 600 gpad has been selected for the design criteria baseline. This value represents the approximate 75th percentile of the range of maximum month I/I values for WWTF flows exceeding 3.0 mgd.

TABLE 4-5 Estimated Infiltration and Inflow

Flow

Influent Flow at WWTF (mgd)

Base Flow

(mgd)(1)

I/I (mgd)

Service Area (acre)(2)

I/I (gpad)

Dry Weather Average 1.96 1.84 0.12 2,709 43

Annual Average 2.50 1.84 0.66 2,709 243

Maximum Month(3) 3.61 1.84 1.77 2,709 653

Peak Day 5.90 1.84 4.06 2,709 1,499 Peak Hourly(4) 7.68 1.84 5.84 2,709 2,156

(1) Base flow calculated at end of 2013.

(2) Estimate of I/I contribution area - represented as the sum of the area of parcels served in 2014 (i.e. not including right of way or sewer easement).

(3) See Table 4-9 for criteria used for flow forecasting. (4) Represents the highest flow measured at the treatment plant on November 19, 2012.

Infiltration and Inflow Analysis using EPA criteria Another analysis of infiltration and inflow was performed to compare estimates of per capita I/I to EPA criteria. These infiltration and inflow rates are summarized in Table 4-6. The U.S. EPA manual entitled I/I Analysis and Project Certification provides recommended guidelines for determining if infiltration and/or inflow is excessive.


1. To determine if excessive infiltration is occurring, a threshold value of 120 gallons per capita per day (gpcd) is used. This infiltration value is based on an average daily flow over a seven to 14 day non-rainfall period during seasonal high ground water conditions.

2. To determine if excessive inflow is present in a collection system, the

USEPA uses a threshold value of 275 gpcd. If the average daily flow (excluding major commercial and industrial flows greater than 50,000 gpd each) during periods of significant rainfall exceeds 275 gpcd, the amount of inflow is considered excessive.

TABLE 4-6

Per Capita Infiltration and Inflow Based on EPA Criteria

Parameter

EPA Criteria for

Excessive I/I (gpcd)

Estimated LSSD I/I

Value (gpcd)

EPA Excessive Infiltration

Criteria

120 79

EPA Excessive

Inflow Criteria

275 190

Infiltration The lowest winter daily flow in 2013 and 2014 occurred on January 24, 2014 (2.211 mgd) and the lowest hourly flow around that day occurred the next morning (about 780 gpm or 1.12 mgd). Local precipitation records (see Chapter 2) show essentially no rain during the preceding 12-day period, January 13-25, 2014. This would also be a period of relatively high groundwater due to a total rainfall of nearly 14 inches for the three-month period leading up to January 13. The average daily flow recorded during this time period is 2.54 mgd. Since the intent of the EPA criteria was to only include domestic flows, 0.152 mgd (six percent of the baseflow of 2.54 mgd) of commercial flow was omitted. With a total population of residential sewer users in early 2014 of approximately 30,1154, and a residential flow of 2.388 mgd (equal to 2.54 mgd minus 0.152 mgd) for this period, the peak infiltration is estimated at 79 gpcd. This value is slightly higher than a similar analysis for data from 2005. Because this value is less

4 See Table 3-5, and add 292 persons for the areas served outside the UGA.


than the EPA guideline of 120 gpcd, the District is not considered to have excessive infiltration by EPA criteria. Inflow The maximum day flow at the WWTP over the period of 2013-2014 was 5.90 mgd (recorded in January 2013), as shown in Table 4-2. Since the intent of the EPA criteria was to only include domestic (residential) flows, 0.354 mgd (six percent of the 5.90 mgd) of commercial flow was omitted. With an estimated total residential population of sewer users in late 2012 of 29,2095, and a non-commercial flow of 5.546 mgd (equal to 5.90 mgd minus 0.354 mgd) for this day, the residential peak inflow is estimated at 190 gpcd. This value is about 17 percent higher than for a similar analysis for data from 2003. Because this value is less than the EPA guideline of 275 gpcd, the District is not considered to have excessive inflow by EPA criteria. Condition S4.E of the current WWTF NPDES permit requires the District to complete an I/I evaluation and submit a summary report to DOE by July 1, 2016. If the analysis finds that I/I has increased by more than 15 percent, the District must prepare a plan and schedule to locate the sources of I/I and correct the situation.

Flow Monitoring Flow monitoring was conducted at six locations in the collection system in early to mid 2006. The purpose of that work was to better identify I/I levels within specific areas of the collection system. The details of that work are presented in the 2007 Plan. Some results were not considered to be representative, due to the challenges associated with short-term flow monitoring in manhole channels. Additional flow monitoring has not been conducted since 2006. Based on the system-wide I/I analysis presented above, it appears that while I/I is relatively low, it is increasing and further analysis is warranted. This is supported by the DOE requirement to complete an I/I analysis in the current NPDES permit cycle. I/I Summary An indicator of I/I is related to the concentration of BOD5. The influent BOD5 concentration is medium strength indicating low levels of I/I. High I/I flows will dilute the strength of BOD5 and the DMR data show a significant difference between dry and wet weather concentrations. For the three-year period presented in Table 4-2, the average dry weather (July, August, and September) BOD5 concentration was 347 mg/L, and the average wet weather (December, January, and February) BOD5 concentration was 248 mg/L, a reduction of 29 percent. The following presumptions can be made regarding future I/I flow:

5 See Table 3-5, and add 292 persons for the areas served outside the UGA.


In the existing sewer system, the I/I contribution to the WWTF will tend to increase as the system ages and slowly deteriorates or is impacted by adjacent construction, tree roots, etc. As the system expands, more surface area and joints are added (mainline, manholes and side sewers) thus potentially allowing more extraneous flows. On the other hand, increases in oversight of construction and improved sewer construction materials, a well as separate stormwater, downspout and footing drain systems in new developments will counter that trend. Regular inspection and attention to faults will reduce the rate of increase and periodic I/I evaluation at the basin level will support targeted I/I reduction work.

The I/I rate is forecast to increase by year 2035 by 15 percent over the

current baseline rates. The current forecast I/I rates are those listed in Table 4-5, except for maximum month, which is 600 gpad. I/I ratesare added to the Base Flow. (See Table 4-10 for the specific criteria.) The I/I contribution area is forecast to increase at a linear rate through the forecast period, as described above.

PROJECTED SEWER SERVICE AREA POPULATION, ERUS AND FLOWS As discussed in Chapter 3, an estimated population of 29,823 out of the total population of 34,477 within the UGA was provided sewer service by the District at the end of 2014. The current and projected 5-year, 6-year, 10-year, 15-year and 20-year ERUs and flows are summarized in Table 4-7. The projected flows and ERUs are based on the growth rates and ERU forecast developed in Chapter 3, Table 3-8. As shown in Table 4-7, the projected year 2035 maximum month flow is 6.20 mgd. This value is 2.1percent higher than the same flow forecast for year 2026 in the 2007 Plan (6.07 mgd). As noted in the analysis above, this forecast is influenced by the use of a per capita flow higher than actual recent discharge patterns, and I/I amounts are forecast to increase over time, per Table 4-9. The ratios of forecast maximum month, peak day and peak hour flow to annual average flow are 1.35:1, 2.24:1 and 4.03:1, on average, respectively. The maximum month and peak day ratios are somewhat lower than the historical ratios noted at the bottom of Table 4-1, whereas the peak hour is significantly higher.

TABLE 4-7 Current and Projected Future Wastewater ERUs and Flows

Year 2014 2020 2021 2025 2030 2035 Residential ERUs

11,134 12,646 12,898 13,906 15,166 16,426

Non-residential ERUs

854 1,020 1,050 1,182 1,370 1,589


Year 2014 2020 2021 2025 2030 2035 TOTAL 11,988 13,666 13,948 15,088 16,536 18,015

Sewer Service Area (ac.)

2,709 3,092 3,156 3,411 3,731 4,050

Base Flow(1) 1.84 2.58 2.64 2.85 3.13 3.40

Dry Season Average Flow(2)

2.09 2.72 2.78 3.01 3.30 3.60

Average Annual Flow(2)

2.61 3.36 3.44 3.74 4.13 4.53

Maximum Month(2)

3.36 4.51 4.62 5.05 5.62 6.20

Peak Day(2) 5.26 7.39 7.58 8.35 9.35 10.39 Peak Hour(3) 6.93 13.37 13.70 15.03 16.76 18.55

(1) Base flow based on 189 gallons per ERU per day (70 gpcd x 2.70 P/ERU). (2) Base flow plus corresponding I/I rate (Table 4-9). (3) Base flow x Peaking Factor (2.5) + Peak Hour I&I rate (Table 4-9). (4) All flows are in million gallons per day.

EXISTING AND PROJECTED INFLUENT BOD5 AND TSS LOADING Existing BOD5 Loading Monthly average influent BOD5 loadings ranged from 3,988 lb/d to 7,743 lb/d for the three-year period of analysis as shown in Table 4-2 and Figure 4-2. The average influent BOD5 concentration for the three-year period is 304 mg/L, which would be considered medium strength domestic wastewater. The average loading of 5,926 lb/d (see Table 4-2) and an average sewer service equivalent population of 31,663 (11,727 ERUs at 2.70 persons per ERU) for the three-year time period of 2012-2014 translate to an average BOD5 loading of 0.187 lb/cap/d, or 0.505 lb/ERU/d. This value is slightly below the DOE Orange Book criteria of 0.2 lb/cap/d. To convert the current maximum month BOD5 loading to a per capita and an ERU basis, the service equivalent population of 31,663 and number of ERUs (11,727) and maximum month BOD5 of 7,743 lb/d for the three-year analysis period were used to calculate a maximum month per capita and ERU BOD5 loading of 0.245 lb/cap/d and 0.660 lb/ERU/d, respectively. The ratio of the maximum month BOD5 loading to the annual average BOD5 loading is 7,743:5,926 or 1.31:1. This ratio is used in the development of future loadings to the WWTF later in the chapter. Existing Total Suspended Solids Loading


A review of Table 4-2 shows that monthly average TSS loadings ranged from 3,775 lb/d to 6,182 lb/d. The average month loading of 5,015 lb/d and an average equivalent population and average ERUs of 31,663 and 11,727, respectively, for the three-year time period translate to an average month TSS loading of approximately 0.158 lb/cap/d or 0.428 lb/ERU/d. The maximum month TSS loading is 6,182 lb/d. Using the same population and ERU values as derived for the BOD analysis, this approach results in a current maximum month value of 0.195 lbs TSS/cap/d or 0.527 lb/ERU/d. The ratio of the maximum month TSS loading to the annual average TSS loading is 6,182:5,015 or 1.23:1. This ratio is used in the development of future flow and loadings to the WWTF later in the chapter. PROJECTED WASTEWATER LOADINGS Future WWTF maximum month BOD5 and TSS loadings are estimated by multiplying the projected ERUs by the respective ERU-based loadings. Future annual average BOD5 and TSS loadings are estimated using the ratio of the maximum month to annual average loadings of these parameters. The current maximum month BOD5 and TSS loadings are 0.660 lb BOD5/ERU/d and 0.527 lb TSS/ERU/d. The ratio of the maximum month to annual average BOD5 is 1.31:1. The ratio of the maximum month to annual average TSS is 1.23:1. The ratio of TSS to BOD on an annual average was 0.845 and maximum month was 0.796 for WWTF data from 2012 through 2014. For similar data for 2003-2005 as considered in the 2007 Plan, the ratios were about 0.8 and were about 1:1 prior to 2003. To be somewhat conservative, this Plan will continue to utilize the BOD loading data (0.660 lb/ERU/day) and apply a factor of 0.95 to calculate the TSS loadings (0.627 lb/ERU/day). Table 4-8 provides a summary of projected future WWTF influent BOD5 and TSS loadings.

TABLE 4-8 Current and Projected WWTF Loadings

ERUs/Loading 2014 2020 2021 2025 2030 2035 ERUs 11,988 13,666 13,948 15,088 16,536 18,015 Annual Average BOD5, lb/d

6,432 6,885 7,027 7,602 8,331 9,076

Max Month BOD5, lb/d

7,743 9,019 9,206 9,958 10,914 11,890

Annual Average TSS, lb/d

5,256 6,966 7,110 7,691 8,430 9,183


ERUs/Loading 2014 2020 2021 2025 2030 2035 Max Month TSS, lb/d

5,851 8,568 8,746 9,460 10,368 11,295

(1) Forecast based on criteria in Table 4-9

(2) Ratio of maximum month to annual average BOD and TSS is 1:31 and 1:23 respectively.

DESIGN CRITERIA Based on the preceding analyses, Table 4-9 summarizes the design criteria used in this Plan for estimating wastewater flows and loadings in the District.

TABLE 4-9 Wastewater Design Criteria

Parameter Criteria - 2015 Criteria - 2035 Household density (persons/ERU) 2.70 2.70 Per Capita Domestic Flow (gpcd) 70 70 Peaking Factor Domestic Flow Varies(1) Varies(1) Average Dry Weather Infiltration and Inflow (gpad)

43 49

Annual Average Infiltration and Inflow (gpad)

243 279

Maximum Monthly Infiltration and Inflow (gpad)(3)

600 690

Peak Day Infiltration and Inflow (gpad) 1,499 1,724 Peak Hourly Infiltration and Inflow (gpad)

2,156 2,479

Maximum Monthly BOD5 (lb/ERU/day) 0.660 0.660 Maximum Monthly TSS (lb/ERU/day) 0.627 0.627

(1) Peaking factor varies depending on the population of the subbasin (see Table 6-2). (2) I/I values are forecast to increase by 15% from 2015 (Table 4-5) to 2035. (3) Maximum Month basis adjusted to 600 gpad.

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CHAPTER 5

EXISTING SEWER SYSTEM INTRODUCTION This chapter describes the District’s existing sewer facilities. Detailed information regarding the Capital Improvement Plan for the gravity collection system, lift stations, force mains and the wastewater treatment facility (WWTF) upgrades will be discussed in following chapters. This chapter also describes interlocal agreements the District has with neighboring jurisdictions and current moratoria. The District operates and maintains a gravity collection system including a dosing station, 29 lift stations and a WWTF. The former WWTP ceased treatment operations in April 2012 and is scheduled for full decommissioning in the next few years. Operations are managed from the District office located on Vernon Road and from the WWTF on 9th St SE. The District’s first sewer collection system was constructed to serve the Frontier Village Complex and was financed and built by developers. This system was constructed in 1965. In 1971, the District expanded its collection system through Utility Local Improvement Districts (ULID) 1 and 2. These projects were constructed with the aid of EPA funding. ULID 1 follows the west shoreline of Lake Stevens and extends from the southern tip of the lake to the northwest shore. ULID 2 provides collection service along the corridor of 91st Avenue Northeast (Hillcrest Drive), from Vernon Road to 11th Place Southeast. ULID 3 was formed in 1980 to serve the east side of the lake south of the then-current limits of the City of Lake Stevens. The construction of this ULID, together with the City’s sewer system also largely constructed from the late 1960s to the 1980s, nearly completed the collection system coverage of the perimeter of the lake. In the early 1990s, ULIDs 7 and 8 were formed west of the lake. Both of these ULIDs serve the eastern corridor of State Route 9, between 4th Street Northeast and 12th Place Southeast. Lift Station 12 (LS12) was constructed and placed in operation in the spring of 1998. This allowed service for the southern portions of the Lake Stevens drainage basin, on both the east and west sides. This project was funded by the District though a combination of revenue bonds and a Public Works Trust Fund loan. Since 1998, the District completed large capital projects to improve, enhance, and upgrade the collection system, including the extension of the force main for LS8, construction of LS12 and LS15, and construction of the Vernon Road/Lundeen Parkway Bypass. In 2005, the District assumed ownership, by agreement, of the sewer collection facilities within the City of Lake Stevens. This increased the size of the District’s collection system by approximately 25 percent. Multiple system extensions, some including completion of additional lift stations, have occurred since the formation of the District and initial sewer installation by the City in conjunction with private property development projects to further expand the collection system and service area.


Currently the District operates and maintains over 112 miles of gravity sewer pipe and force mains ranging in size from 8-inch diameter to 36-inch diameter for the gravity sewers and from 2-inch diameter to 19.4-inch diameter for the force mains. The system includes 29 wastewater lift stations and associated force mains. The initial wastewater treatment plant was constructed in 1965 on Ebey Slough and was expanded or upgraded three times from 1971 to 2002. A new treatment facility, located approximately one mile south of the existing facility, was constructed and began operation in April 2012. WASTEWATER COLLECTION SYSTEM The District’s wastewater collection system consists of manholes, gravity sewer mains, lift stations, force mains, tight lines, and one flush or dosing tank. The District’s gravity sewer system is shown in Figure 5-1 and the lift stations and sewer trunks are shown in Figure 5-2. A large fold-out map of the existing system showing pipe size and manholes designations and locations is included at the back of this Plan. Also included at the end of the chapter are individual sheets showing enlarged maps of some portions of the collection facilities. The District’s wastewater collection system is comprised of over 112 miles of pipe varying in size from 6-inch collectors to 36-inch interceptors. Many types of pipe material have been used in the construction of the system including concrete, polyvinyl chloride (PVC), high-density polyethylene (HDPE), and ductile iron. The majority of the system constructed in the 1960s and 1970s is asbestos cement, reinforced concrete, and cast iron pipe. After the mid-1970s, PVC, HDPE, ductile iron, concrete, and reinforced concrete have been used, with the majority of new systems being PVC. Eight-inch pipe comprises approximately 80 percent of the collection system. The District also has a special type of gravity sewer line called a tight line. No gravity side connections are allowed in the tight lines. These pipes have intermediate manholes to allow inspection and maintenance. The tight lines along the Campus Park (Hewlett-Packard) Trunk has a flush tank at the uphill end of the line to ensure that there is sufficient flushing velocity to prevent the settling of solids within the tight line. The wastewater collection system is a “separate” system. There are no intentional combined sewers carrying stormwater and sanitary sewage. Stormwater does, however, enter the sewage collection system as infiltration and inflow, as discussed in Chapter 4. Generally, flows in the wastewater collection system drain from the hills overlooking Lake Stevens down into the depression where the Lake is situated, then through a series of lift stations and gravity trunk lines west to the WWTF. The major lift stations in the District are LS20, LS12, LS15, and LS1C. In addition, there are areas to the west and south of the lake that drain north into the same trunk on Vernon Road or south to


the recently completed Southwest Interceptor. The District operates and maintains 29 lift stations. About one half of these stations serve small development areas (i.e. less than 55 acres), while the rest serve significant portions of the sewer service area. Table 5-1 (at end of chapter) provides an inventory of the gravity sewer lines by length, pipe diameter, and material for all pipe diameters 6-inches and greater. This inventory is based on GIS information maintained by the District. Table 5-2 (at end of chapter) provides a similar inventory of the lift stations and force mains. GRAVITY SEWERS The District’s sewer collection system is organized around a series of lift stations and trunk sewer systems. Each gravity trunk sewer is described briefly below. The lift stations and the areas served by each are described in the next section. Campus Park Trunk In 1985 the Campus Park trunk (8 to 18 inches in diameter) was constructed by the Hewlett-Packard Company to serve their manufacturing facility located at the southwest corner of Soper Hill Road and State Route 9 (SR 9). Developers have extended the line up the west side of the Hewlett-Packard site to Soper Hill Road since 1993. In 2003 the manufacturing facility was sold and the area has been developed as the Campus Park residential subdivision. In addition to Campus Park, this trunk now serves areas to the west and south, all of which are being developed as residential. This pipe has a “belly” where it passes under a creek. A flush/dosing tank was installed to prevent solids from settling and creating clogs by regularly passing high velocity flows through this portion of the pipe. The flow during the “flush” is approximately 700 gpm. This trunk was rerouted as part of the WWTF construction. The segment west of Sunnyside Blvd. was abandoned and flow was diverted south in Sunnyside Blvd. in a new 12-inch trunk extension to LS20. Frontier Heights Trunk This 8 to 12-inch diameter pipe serves the residential area north of State Route 204 (SR 204) between SR 9 and Lundeen Parkway. The area is completely developed with single-family and multi-family residential uses. The trunk was constructed in 1968. Vernon Road West Trunk The Vernon Road West trunk was constructed in 1965 as a 10-inch-diameter pipeline to convey wastewater from Frontier Village to the former treatment plant. As part of ULID 1 in 1971, a parallel line composed of 21- and 24-inch diameter pipes was installed from 91st Avenue SE to the treatment plant. Upstream from 91st Avenue SE, the 10-inch Vernon Road West trunk under SR 9 was replaced with a 21-inch and 18-


inch diameter trunk to pick up the 16-inch-diameter force main discharge from LS5, and now from LS15. The Vernon Road West trunk now conveys almost all of the District’s flows (except for the Campus Park area) to LS20 with direct inputs from LS15 and other major trunks. The Vernon Road Diversion trunk was completed in 2012 and diverts all flow in the 21-inch and 24-inch part of this trunk, at Manhole #101, south to the WWTF. Glenacres/Meridian Trunk The Glenacres/Meridian trunk receives flow from both the 12-inch-diameter pipe along SE 83rd Drive and the 18-inch-diameter pipe from 99th Avenue SE trunk just south of SR 204 and conveys it to the Vernon Road West trunk. This trunk extends from Vernon Road south into the Glenacres subdivisions (SE 83rd Drive) and also branches east underneath 91st Avenue SE and SR 9 (Meridian) to serve the residential subdivisions along 99th Avenue SE. LS12 discharges into the 99th Avenue trunk at Manhole #2535 on Chapel Hill Road. The lower portion of this trunk was constructed as part of ULID 7 in 1993, and development has since extended it. 91st Avenue SE Trunk The 91st Avenue SE trunk sewer consists of 8-, 10-, and 12-inch-diameter pipes and serves single- and multi-family residences, Hillcrest and Skyline Elementary schools, and Lake Stevens Middle School. The trunk also receives flows from LS1 and was mostly constructed as part of ULID 2 in 1968. LS11 previously discharged toward the north end of this trunk but that flow was diverted to the Southwest Interceptor in 2014. Davies Road Trunk The 12- and 18-inch-diameter Davies Road trunk receives flow from LS8 and LS14 as well as gravity flows from adjacent areas to the west, and conveys them to LS12. The majority of these areas are residential, with some small neighborhood commercial development. This trunk was constructed in 1979 with improvements in 2000. Stitch Road Trunk The Stitch Road Trunk serves the residential properties at the south end of Lake Stevens along South Lake Stevens Road between Davies Road and Machias Cutoff and some areas along Machias Cutoff. This 8-inch-diameter trunk discharges to LS2 and was constructed as part of ULID 1 in 1971. In 1999, upgrades to LS8 and construction of a force main extension for LS8 diverted flows around this trunk. The force main extension now discharges LS8 flows into the Davies Road trunk. South Lake Stevens Road Trunks An 8-inch-diameter trunk, constructed as part of ULID 3 in 1982 serves the area draining to LS7, which pumps flows to an 8- and 10-inch-diameter trunk draining to LS8. Lift stations LS9 and LS10 also pump into the trunk to LS8.


Vernon/Lundeen Trunk The Vernon Road/Lundeen Parkway trunk serves the north portion of the District. This 12-, 15-, and 18-inch-diameter trunk, originally constructed as part of ULID 1, was upgraded in 1997 with a parallel trunk of 21 to 24 inches in diameter and receives flows from LS1C, LS7C, LS8C, LS5 and LS6. Land use within this area is predominantly single- and multi-family residential, with some pockets of commercial use and the larger industrial and commercial areas within the City of Lake Stevens. Originally constructed as part of ULID 1 in 1971, this trunk once discharged to LS5. LS5 now discharges to LS15, which also now receives all the flows from the Vernon/Lundeen trunk. Lake Drive Trunk The Lake Drive trunk drains the residential areas adjacent to Lake Drive into the Vernon/Lundeen trunk. This 8-inch-diameter trunk was constructed by developers starting in 1994, with extensions in 1997 and 2000. 99th Avenue NE Trunk The lower portions of this 10-inch-diameter trunk (from Lundeen Parkway to 28th Street NE) were constructed as part of ULID 1 in 1971 and serves the residential areas adjacent to 99th Avenue NE, with a developer extension of 8-inch-diameter pipe serving a large church and Sunnycrest Elementary School. Callow Road Trunk The Callow Road trunk consists of 18-inch diameter pipe and was constructed as part of ULID 1 in 1971. Although this trunk currently extends only about 700 feet from the Vernon/Lundeen trunk, it is expected to be extended north to SR 92 in the future to serve new development. This trunk collects flows from the residential areas lying adjacent to and east of Callow Road, via a series of 8-inch diameter pipes, including inputs from LS7C and LS8C. LS8C serves the northern portion of the original area of the City of Lake Stevens. Vernon Road East Trunk This 15-inch-diameter trunk was constructed by the City of Lake Stevens in 1971, and serves the original area of the City of Lake Stevens. Flows from LS2C and the residential areas north of Vernon Road drain into this trunk, which conveys flows to LS1C. Most of the downtown commercial areas in the City drain to this trunk. Lift Stations LS3C, LS4C, LS5C, LS6C and LS9C all are tributary to LS2C. 26th Street NE Trunk


The 26th Street NE 8-inch-diameter trunk services by gravity the residential areas lying north of 26th Street NE in the original area of the City of Lake Stevens and also Lake Stevens High School. Originally constructed in 1971, with extensions in 1995, flows are now conveyed east to LS8C. Prior to diversion to LS8C in 2004, flows from these areas were conveyed south into the Vernon Road East trunk. Due to capacity problems in that trunk and with LS1C and LS5, these pipes have been plugged at the upstream (north) end with flow now diverted east to LS8C. Grade Road Trunk This 10- and 12-inch-diameter trunk extends from LS8C to almost SR 92 along Grade Road and serves the residential, commercial, and industrial areas along this corridor. The construction of this trunk, in 2005, allowed the City of Lake Stevens to decommission the small temporary lift station located at 34th Street NE and Doe Way, in the 3 Township North subdivision. East Lake Shore Drive Trunk The 8-, 10-, and 15-inch-diameter East Lake Shore Drive trunk provides gravity service to the downtown areas of the City of Lake Stevens, including flows from Lift Stations LS3C, LS6C and LS9C with conveyance to LS2C. Constructed in 1971, this trunk also serves the single- and multi-family residential areas surrounding downtown. Vernon Road Diversion Trunk The 30- to 36-inch diameter trunk, completed in 2012 to divert significant flows to the WWTF, begins on Vernon Road, east of 81st Ave NE, at Manhole #101 of the Vernon Road West trunk. All flow is diverted south at this location to the Vernon Road Diversion trunk. This trunk continues southerly across SR 204 and discharges to the Southwest Interceptor. The area previously served by LS13 now drains by gravity to this trunk. LS13 was removed once this trunk was placed in service. Southwest Interceptor The 21- to 36-inch interceptor begins at the intersection of 20th St SE and 99th Ave SE and continues west along 20th St to about 81st Ave SE. The section along 20th St SE contains a 21-inch pipe from the intersection of 20th St SE and 99th Ave SE to just east of SR 9 for a length of 9,17 feet. From there, a 24” pipe continues along 20th St SE to the east end of Trestle Station, east of 79th Ave SE, for a length of 5,184 feet. From there, a 30-inch pipe continues northerly and westerly for 4,678 feet. It then increases to a 36-inch pipe and turns due west where it collects flow from the Vernon Road Diversion Trunk at 10th St SE west of 77th Dr SE. Finally, it continues west along 10th St SE where it discharges into the WWTF west of SR 204. LIFT STATIONS AND FORCE MAINS


An inventory of the District’s sewage lift stations is included in Table 5-2 (at end of chapter). Table 5-2 also presents information regarding the year installed, standby power, and other features for each station. The lift stations with the highest capacities are LS1C, LS12, LS15 and LS20. The location of each of the District’s lift stations is shown on Figure 5-2. A schematic depiction of the lift stations flow pattern is shown in Figure 5-3 and Figure 5-4 indicates the basins tributary to each station. In support of completion of this Plan, a Lift Station Condition Assessment was prepared by CHS Engineers, LLC, with the support of RJC Engineering, PLLC and the District. The Assessment only conditions age, condition and reliability of the primary elements of each station. Capacity upgrade needs are considered separately, in Chapter 6. See Appendix G for a copy of the Assessment. The location and service area of each lift station is summarized below. LS1 – Lift Station 1 discharges into the 91st Avenue SE gravity trunk and was constructed in 1969 to serve the Cypress Isle subdivision. The service area is approximately 20 acres. This is one of the few stations without a dedicated backup power system. This station can be removed following completion of a gravity connection to the south, to connect this basin to the LS11 service area. LS2 – Constructed in 1969 to serve the predominantly residential areas around the southern portion of the lake, LS2 was downgraded with new pumps in 1998 in conjunction with the construction of LS12. Originally discharging into the collection system for LS3, this station now discharges into the Davies Road trunk, and eventually LS12. The service area is approximately 270 acres. Eventually, a portion of the basin will flow to a new lift station off Machias Cutoff Road and be routed to the Southwest Interceptor. LS3 – Lift Station 3 was constructed as part of ULID 1 in 1970 and serves approximately 44 acres of residential property along the western shore of the lake and discharges into the collection system for LS4. Originally designed to accept flows from LS2, this station has had extra capacity since LS12 and its force main were constructed. At some time in the future, this station will be downgraded to free up capacity in LS5. LS4 – Lift Station 4 was constructed as part of ULID 1 in 1970 and serves approximately 103 acres (plus 44 acres from LS3) of residential property along the western shore of the lake and discharges into the collection system for LS5. It is expected that flows from LS4 will be diverted with a new force main to the Vernon Road West trunk to free up capacity in LS5, sometime in the future. LS5 – Constructed in 1969 and downgraded in 2004 in conjunction with the construction of LS15, LS5 now pumps flows into the Vernon/Lundeen trunk, and eventually LS15 and serves an area of commercial and residential uses of approximately 185 acres, plus area served by LS4 (total of 331 acres).


LS6 – Lift Station 6 serves an approximate area of 47 residential acres along the north shore of the lake. Constructed in 1970, LS6 discharges into the Vernon/Lundeen trunk. This station will be downgraded to suit its peak flow requirements and reduce flow to the downstream trunk, in context of increased discharge from LS2C. LS7 – Lift Station 7 was constructed in 1980 and serves a residential area along the eastern shore of the lake of approximately 83 acres. It receives flow from the LS21 service area (55 acres). This station discharges into the South Lake Stevens Road trunk and the LS8 service area. LS8 – Lift Station 8 was constructed in 1980 and upgraded in 2000. This station serves a residential area of approximately 254 acres, plus flows from LS7, LS9 and LS10 (395 acres total service area). To relieve capacity problems in the Stitch Road gravity trunk, the 8-inch force main was extended in 2000 with a 10-inch force main to the intersection of Davies Road and South Lake Stevens Road, where it discharges into the Davies Road trunk. Eventually LS8 flows will be routed to a new regional lift station and then to the Southwest Interceptor. LS9 – Lift Station 9 was constructed in 1980 and serves a residential short plat located at Rhodora Heights Road and 7th Street SE. This station serves an area of less than two acres and discharges into the South Lake Stevens Road trunk and eventually LS8. This is one of the few stations without a dedicated standby power system. This station will be removed or relocated further east, with future development of adjacent lower elevation land. LS10 – Lift Station 10 was constructed in 1980 and serves a residential short plat located on Rhodora Heights Road. This station serves an area of just over two acres and discharges into the South Lake Stevens Road trunk and eventually LS8. This is one of the few stations without a dedicated standby power system. This station will be removed or relocated further east, with future development of adjacent lower elevation land. LS11 – Lift Station 11 was constructed in 1983 and serves about 180 acres. Originally, this station’s force main discharged into Manhole 55 on 91st Avenue SE. Due to capacity problems in this trunk, the force main was extended to Manhole 45 in order to bypass the flow restriction in the trunk. With the completion of the Southwest Interceptor in 2014, the discharge was diverted to the new interceptor and the existing force main along 91st has been abandoned. LS12 – Lift Station 12 was constructed in 1996 and serves as one of the District’s major lift stations. It has a direct service area of about 312 acres. This station also receives flow from LS2, LS8 and LS14 (1,514 acres total service area). Lift Station 12 discharges into the Meridian trunk collection system on Chapel Hill Road. Eventually the service area of LS12 will be reduced with the diversion of the discharge from LS8 and LS14 directly to the Southwest Interceptor.


LS13 – Lift Station 13 previously served the Skyline Ridge subdivision. This station was removed following completion of the Vernon Road Diversion in 2012. LS14 – Constructed in 2000, this developer-donated station was built to serve several residential developments located on either side of South Lake Stevens Road and north of 20th Street SE. The direct service area is about 168 acres. The station also receives flow from LS17 for a present total service area of 537 acres. It discharges into the Davies Road trunk and eventually LS12. Eventually its discharge will be routed to the Southwest Interceptor. In 2016, the discharge of LS17 will be diverted from this basin to discharge directly to the Southwest Interceptor. LS15 – Lift Station 15 is the largest station in the District and was constructed in 2003 to replace LS5 (except for local service needs). Besides its gravity collection system of about 762 acres, this station receives flows from LS5, LS6, LS1C, LS7C, and LS8C (2,436 acres of total service area). LS15 discharges into the Vernon Road West trunk. LS16 – Lift Station 16 serves the Vernon Road Estates subdivision (approximately nine acres) and was constructed in 2003. This station discharges into the Vernon Road West trunk and eventually to LS20. LS17 – Constructed for the Pasadera subdivision in 2005, Lift Station 17 serves 247 acres plus receives flows from LS18 (total service area of 368 acres) and conveys them to LS14. A project is planned for 2016 to upgrade LS17 and reroute the force main to discharge LS17 flows directly to the Southwest Interceptor. LS18 – Constructed for the Osborne subdivision in 2007, Lift Station 18 serves approximately 121 acres and discharges into the collection system upstream of LS17. It is expected that eventually a gravity-only line will be constructed to connect the Osborne development to the collection system for LS17. LS19 – Constructed for the Westview Ridge development in 2008, Lift Station 19 serves approximately 109 acres and discharges into the adjacent Cavalero Ridge development collection system, upstream of a connection to the Southwest Interceptor. LS20 – This station was constructed as part of the WWTF project in 2012 and is situated to transfer flows to the new WWTF from the Campus Park and Vernon Road West trunks. Its service area is about 676 acres plus the area served by LS16 (total service area of 685 acres). This station discharges flow via a 12-inch force main that was originally a tightline to convey flow from the Southwest Interceptor to the former WWTP site. LS21 – Constructed for the Greenwood Village development in 2006, Lift Station 21 serves approximately 55 acres and discharges into the collection system tributary to LS7.


LS1C –Lift Station 1C was constructed as part of the City sewer system in 1970 and it was upgraded in 2004 from 900 gpm to 1,100 gpm. Draw down tests in 2014 indicated a current capacity of about 650 gpm. The gravity service area for LS1C is a mixture of commercial and residential uses of approximately 332 acres, plus flows from LS2C (788 acres of total service area). A 60,000 gallon equalization vault was constructed by the City in the 1990s just upstream of this station to attenuate peak flows coming into the station. That vault has proven to be challenging to operate relative to its flow management capacity and is not in operation. LS1C discharges into the Vernon/Lundeen trunk. With planned improvements to LS2C and its force main, flow will be diverted from the LS1C tributary area and the station can be derated slightly. LS2C – Lift Station 2C receives flows from LS3C, LS4C, LS5C, LS6C, and LS9C and also a gravity collection area of 360 acres (456 acres total). Constructed in 1970, this station serves the commercial center of the City and pumps flows to the Vernon Road East trunk to LS1C. In 2004, the station was outfitted with new pumps for increased capacity. LS2C will eventually discharge directly to the Vernon/Lundeen trunk. LS3C – Constructed in 1970 and upgraded with a generator in 2006, this station serves the residential area at the northeast corner of the lake, with an area of approximately 34 acres. This station discharges into the collection system for LS2C. LS4C – Constructed to serve the Catherine Creek Park subdivision (approximately 19 acres) in 1979, this small station discharges into the collection system for LS2C. This is one of the few stations without a dedicated backup power system. LS5C – Constructed to serve the Shadow Brook subdivision (approximately 2.5 acres) in 1992, this small station discharges into the collection system for LS2C. This is one of the few stations without a dedicated backup power system. This station can likely be eliminated by extension of 8” gravity sewer to LS4C. A short segment of easement and a wetlands permit may be necessary to complete this connection. LS6C – Serving the Catherine Creek Gardens subdivision, this station was constructed in 1994 and was outfitted with a generator in 2006. The service area for this station is approximately 14 acres. The station discharges into the collection system for LS2C. LS7C – Lift Station 7C serves approximately 25 residential acres and currently discharges into the force main from LS8C. LS7C was constructed in 2007. This station can be eliminated by collection of gravity sewer connection to the west/northwest. LS8C – Lift Station 8C was constructed in 2000, and upgraded with new pumps, flow meter and generator in 2003. Lift Station 8C serves a mixture of commercial and residential land use of approximately 482 acres and discharges into the Callow Road trunk. The 2003 upgrade increased the station capacity and rerouted the force main from the collection system for LS1C to the Callow Road trunk.


LS9C – Serving the Timberline Court development, this station was constructed in 1999 and was outfitted with a new generator in 2006. The service area for this station is approximately 26 acres. The station discharges into the collection system for LS2C. The force mains of LS15, LS17 and LS8C can be injected with liquid oxygen to reduce odors at the discharge points. A long detention time within these force mains encourages anaerobic conditions to develop within the pipes resulting in the formation of hydrogen sulfide. The injection of oxygen reduces odors by maintaining aerobic conditions in the force mains, thereby reducing the formation of hydrogen sulfide. Flow meters are included on the force mains for stations LS5, LS 8, LS12, LS15, LS17, LS20, LS1C and LS8C. LIFT STATION SCADA SYSTEM The District has a system-wide supervisory control and data acquisition (SCADA) system with monitoring panels at the lift stations, except for LS9. The SCADA System provides data, information, and warnings to District personnel for the purpose of preventing the spilling of raw sewage into the Lake or adjacent water bodies or the backup of sewage into residential or commercial properties. The system is a combination of the District system as developed prior to 2005, the City system as assumed in about 2005 and a new element at LS20, completed with the WWTF in 2012. Other than the work in 2012, the system has not been upgraded since at least 2005. Some elements of the system are antiquated and repair components are challenging to find or are obsolete. Existing Lift Station SCADA System The current system calls out alarms from remote sites (lift stations) via a telephone auto-dialer, which calls the District office (or an answering service if during non-business hours). The District then sends an employee to take action to address the alarm. Some stations also have programmable logic controllers (PLCs) which are connected to field devices for sensing and control of the lift stations and the wastewater treatment facility. These do not generally have outputs to auto-dialers or other operator interfaces to allow viewing the information remotely. While the present system notifies the District when an alarm condition exists, it does not provide information on the nature of the alarm. One significant shortcoming of the existing system is that it cannot monitor failures of the auto dialer. Therefore, it is possible that a problem may remain for a long period of time before field staff detects the problem during routine inspection of the lift stations. SCADA for Newer Lift Stations The District included a new SCADA system with the construction of LS20, LS15 and the upgrade of LS5. Similar equipment has been installed at LS8, LS12 and at the WWTF.


This new system includes the software and hardware to monitor the alarms and display certain data at the station and on a computer screen at District Headquarters for the stations equipped with the new PLCs and radio transmitters. The District should plan to complete a comprehensive update of its SCADA system and supporting communication system. The primary objectives would include a single comprehensive and reliable means of communication between all monitoring sites, the WWTF and the Office. Each remote telemetry unit (RTU) should be supported by sensors and equipment suitable for monitoring and indicating, locally and remotely, equipment status and critical or alarm conditions. Power and communication status as well as standby generator operations should be monitored at each site as well. WASTEWATER TREATMENT FACILITY (WWTF)

The original wastewater treatment plant was constructed in 1965 on Ebey Slough and had undergone three expansions, the first in 1971, the second in 1985, and the third in 2002. A new treatment plant, known as the Sunnyside Wastewater Treatment Facility (WWTF), located approximately one mile south of the original facility began operation in April of 2012. The Lake Stevens Sewer District constructed the Sunnyside WWTF to provide additional capacity for future growth, as well as to meet current and anticipated effluent limits and satisfy the Washington State Department of Ecology’s (DOE’s) redundancy requirements. Raw domestic wastewater from the Lake Stevens Sewer District collection system is conveyed to the treatment plant’s headworks through a 42-inch gravity sewer. The headworks structure serves several purposes, including influent flow measurement sampling, screening and primary sludge degritting. Upon entering the headworks structure, the wastewater from the District first passes through a 24-inch Parshall flume for influent flow measurement. After passing through the Parshall flume, the wastewater flows through two mechanical fine screens. The fine screens are perforated plate band screens with 6 mm perforations and remove large solids (rags, plastics, and other inert material) from the wastewater. The fine screens are located in adjacent channels and discharge the screened material into hydraulic flumes. The hydraulic flumes use non-potable water to transport the screenings to the screenings washer/compactor associated with that screen. The screenings washer/compactors utilize high-pressure sprays to break up any fecal matter contained in the screenings and return it to the influent flow stream. The washed screenings then pass through the compaction zone of the washer/compactors where they are dewatered, compacted, and discharged to the screenings dumpster. There is a third channel located between the two channels containing the influent fine screens. Another fine screen will be installed in the third channel in the future as growth in the service area dictates, however until that time the third channel will serve as a bypass channel should flows to the treatment facility exceed the capacity of the in-service


screens. If this were to occur, the secondary screens in the Primary Effluent Screenings Building will provide the necessary screening of the influent wastewater. After screening the influent wastewater is automatically sampled by a refrigerated composite sampler located adjacent to the common channel. This sampler provides a 24-hour composite sample based on a flow paced signal from the Headworks Building PLC. A 24-hour composite sample is required to complete all of the necessary laboratory analyses of the influent water quality. Screened influent wastewater flows by gravity from the headworks structure to the primary clarifier splitter box through a 36-inch pipeline. The primary clarifier splitter box controls the flow split between the two primary clarifiers and ensures that the two clarifiers receive equal flow. Each primary clarifier can be isolated from the flow stream by closing the appropriate slide gate at the splitter box. The primary clarifiers operate in parallel to remove heavier organic and inorganic solids from the screened wastewater. At this facility, the primary clarifiers are also used to remove grit. Grit removal is accomplished by first allowing it to settle out in the primary clarifiers and then pumping it along with the primary sludge, as dilute slurry, to the hydrocyclone in the Headworks Building, where the grit is separated from the primary sludge. The degritted primary sludge is then thickened in a circular gravity thickener, prior to being pumped to the solids treatment system, while the grit is washed and dewatered by the grit classifier prior to being deposited in a dumpster for transport to a landfill. Effluent from both primary clarifiers flows by gravity to the primary effluent screening building where the wastewater is screened again prior to being allowed to enter the aeration basins and membrane filtration system. The secondary screening system is similar to the fine screen system described earlier in both form and function. The major difference between the two is the size of the screen perforations. The secondary screens have smaller (2 mm) perforations to remove any remaining fibrous material, including hair. This second level of screening is critical to the longevity and maintenance of the membrane system. Effluent from the primary effluent screenings building enters primary effluent channel where it is combined with the mixed liquor return exiting the deoxygenation zone. The combined primary effluent and mixed liquor return flow stream passes through a flash mixer that is designed to ensure that a homogeneous mixture of primary effluent and return activated sludge enters the aeration basins. The homogeneous mixture of primary effluent and return activated sludge (mixed liquor) enters each aeration basin via a single influent slide gate. An equal flow split between the in service aeration basins is maintained by controlling the mixed liquor pumps to ensure that mixed liquor is pumped out of each in service aeration basin a equal rates. It is in the aeration basins that the biological removal of both carbonaceous and nitrogenous material occurs, by a consortium of suspended microorganisms. The three


parallel aeration basins each contain anoxic and aerobic activated sludge zones configured in a pre-denitrification (Modified Ludzack-Ettinger) mode of operation. Aeration and mixing of the aerobic zones is accomplished using an air distribution system consisting of fine bubble diffusers, while the anoxic zones are mixed using jet mixing systems. At this treatment plant internal recirculation of nitrified mixed liquor is achieved using the mixed liquor pumps. These pumps lift nitrified mixed liquor from the last aerobic zone up to the membrane basin inlet channel. After passing through the membrane basins the nitrified mixed liquor flows by gravity through the deoxygenation zone prior to being mixed with primary effluent. In the deoxygenation zone the majority of the dissolved oxygen in the mixed liquor is respired via endogenous respiration to reduce the dissolved oxygen concentration of the mixed liquor being recycled to the anoxic zones. Mixed liquor entering each basin first passes through two anoxic zones where nitrate is utilized to oxidize a portion of the organic carbon in the influent wastewater (denitrification), prior to passing through three aerobic zones. Single-stage, centrifugal blowers supply air to the diffusers. Blower output is controlled automatically to maintain a specific dissolved oxygen concentration within each oxic zone, using a cascade loop control system. Waste activated sludge (WAS) and foam is drawn off the surface of each aeration basin at the WAS/Scum box and is then pumped to the thickening centrifuge by two rotary lobe pumps. Alternatively, WAS can also be withdrawn from the mixed liquor return channel. After being lifted to the membrane basin influent channel by the mixed liquor pumps, mixed liquor flows by gravity through the membrane basins and back to the deoxygenation zone as described earlier. The membrane basins provide very effective solids separation and produce very high quality (comparable to Class A Reclaimed Water) final effluent. Each membrane basin is equipped with six membrane cassettes. The cassettes each contain forty-eight modules of hollow fiber membranes that provide a physical barrier for liquid/solids separation. Permeate pumps then draw filtered effluent (permeate) through the hollow fiber membranes and discharge the filtered effluent to the UV channel. The filtered effluent then flows by gravity through the low-pressure, high intensity ultraviolet (UV) disinfection system. This system exposes the pathogenic organisms to ultraviolet radiation, which damages their genetic material, thereby preventing reproduction. The UV disinfection system consists of three banks of lamps in series in a single open channel. The disinfected filtered effluent then passes through a level control gate and cascades into the effluent channel. The effluent then passes through a 24-inch Parshall Flume for effluent flow measurement prior to being discharged by gravity to Ebey Slough via a two-port, submerged diffuser. The effluent flow, non-potable water flow and irrigation water flow are all totalized and used in conjunction with effluent transmittance to control the output of the UV effluent disinfection system. Solids generated by the primary and secondary treatment processes are thickened and are then treated to Class B biosolids standards using anaerobic digestion. After


undergoing anaerobic digestion, the treated biosolids are dewatered and hauled to a permitted utilization site for land application. The anaerobic digestion treatment process consists of two primary mesophilic anaerobic digesters that can be operated either in series or in parallel. Waste primary sludge from the gravity thickener, waste activated sludge from the thickening centrifuge, and scum from the scum holding vault are all pumped to the anaerobic digesters. Prior to entering the digesters, these flow streams are combined with the digested sludge that is being re-circulated through the water-to-sludge spiral heat exchanger to maintain the digesters at a fairly constant temperature within the mesophilic range. This is accomplished by continuously pumping digested sludge and hot water through adjacent counter current channels within the heat exchanger allowing the heat from the hot water to be transferred to the sludge. Hot water to the heat exchanger is supplied by two fire-tube boilers capable of burning either digester gas (biogas/mostly methane) or commercial natural gas. These same boilers also provide hot water for heating for the majority of the building spaces at the WWTP. The boilers operate in a lead-lag configuration with the lead boiler always firing digester gas, when it is available, and the lag boiler always firing natural gas. Under this operating strategy the lag boiler should rarely be required keeping natural gas consumption to a minimum. Excess biogas will be flared at the waste gas burner. In the primary anaerobic digesters, a portion of the organic content of the waste sludge is be broken down and metabolized by methanogenic bacteria, stabilizing the sludge and reducing the overall mass of waste sludge for final disposal. The volume of the primary digesters is sufficient to meet the time and temperature requirements for Class B vector attraction and pathogen reduction. Once the waste sludge has been treated to Class B biosolids standards in the anaerobic digesters, it flows by gravity to the digested sludge holding tank. Digested sludge is then pumped from the sludge holding tank to a high-speed, solid-bowl dewatering centrifuge. After passing through the centrifuge the dewatered sludge is pumped to the sludge truck loading bay for hauling to a land disposal site. Polymer is added to the digested sludge as a flocculent to enhance solids capture and improve dewatering. Centrate from the dewatering operation drains by gravity to the centrate storage tank, where it remains until it is pumped back to the liquid stream treatment process. Odor control is provided for the areas considered to be the main sources of foul air. These odor-generating areas include the headworks, primary clarifiers, primary effluent screenings building, gravity thickener, digester building, plant drain pump station, centrate holding tank, and scum vault. Two centrifugal fans extract foul air from these facilities and discharge it to six biofilters for treatment. Each biofilter consists of a 5-foot-deep bed of shredded root media on top of a limestone air plenum. The shredded root media provides a surface on which the microorganisms that degrade the odor-causing compounds can grow. In order to


ensure that the optimum moisture content and temperature for the microorganisms are maintained, the foul air will pass through three humidification towers (each one serving two biofilters) before entering the biofilters. The Puget Sound Clean Air Agency (PSCAA) has authority to regulate emissions that impact air quality, including objectionable odors. The air containment and treatment measures included at the WWTF effectively control air quality at levels such that regulatory oversight is not required. A permit or other oversight from PSCAA has not been necessary. The treatment process is controlled and monitored by a Supervisory Control and Data Acquisition (SCADA) system. The SCADA system primarily consists of three work station computers and three laptop computers running human machine interface (HMI) software and four programmable logic controllers (PLCs) linked together using Ethernet. There are several other PLCs located in vendor-supplied control panels that are linked to the plant PLCs using Ethernet. PLCs in the vendor-supplied control panels only relay status and alarm conditions to the plant PLCs, and therefore control of these pieces of process equipment is localized to the PLCs in the control panels. Each of these vendor-supplied control panels is equipped with an operator interface (OI). There are also numerous process sensors distributed around the treatment facility that monitor vital process parameters. The individual process sensors communicate with the PLC network, which makes control decisions for the unit processes based on the measured parameters. The PLCs also pass sensor inputs to the HMI computers, where the analog and discrete outputs are displayed for the operator to view. The operators may change some of the parameter set points that the PLCs use to make control decisions via the HMI computer, effectively allowing the operators to modify the process remotely. There are also four different modes in which the HMI computer can communicate alarm conditions to the treatment plant operators. These include:

Detailed alarm messages on the HMI screen. Audible announcements of alarm conditions at the computer. The primary auto dialer, which will contact the operators with a prerecorded

telephone message. A backup alarm dialer that will contact the operators if the primary alarm dialer is

not functioning.

The new WWTF does not have any significant volume of storage for either bypass or reclaimed water. The District’s NPDES Permit does allow for discharge to Ebey Slough. It is possible that the District can meet its NPDES discharge limits and not meet requirements for “Class A” Reclaimed Water. Bypass and reclaimed water storage is not a requirement because the District can utilize the outfall that discharges to Ebey Slough.


Potential reuse options include offsets to existing water rights, irrigation or landscaping use, flushing of sanitary sewers and industrial use. Production of reclaimed water is economically feasible if the cost of producing and distributing reclaimed water is less than the cost of purchasing water. Currently, water reuse is not cost effective for any of the above options with the exception of sanitary sewer flushing. The permit capacity of the new WWTF is summarized in Table 5-3 (at end of the chapter). The Peak Day and Peak Hour design flows are 7.15 and 11.53 mgd, respectively. The permit requires the District to begin planning for upgrades necessary to maintain influent flow and loading capacity once 85 percent of any one parameter is reached, or the maximum flow or loading is anticipated to be reached within five years, whichever is earlier. Forecast flows and loadings are presented in Tables 4-7 and 4-8. As indicated in Table 5-3, the limiting permit criteria is anticipated to be Maximum Month flow, and the 85 percent threshold for planning for additional capacity is forecast to be reached in year 2019. Fortunately, the planning for the next phase of upgrade has been completed (2006 Wastewater Facilities Plan). The work would not need to be completed until year 2025, per the forecast. On the other hand it should be recognized that the flow criteria developed in Chapter 4, and supporting the values in Table 4-7, are purposely conservative. The future flows are based on the County growth forecast and year 2035 target population. As discussed in Chapter 3, the County-based forecast growth rate in ERUs is about 35% higher than the District has experienced over the past several years. The timing of Phase III is sensitive to actual growth, and more sensitive to actual I/I levels. However, it appears that the upgrade should be planned to be completed just within the first ten years of the forecast period, only if growth occurs at a rate close to the County target for 2035 within the Lake Stevens UGA. The District will need to re-evaluate the Phase III WWTF expansion between seven to ten years from the adoption of this Comprehensive Plan update, based on actual growth. The WWTF plans design criteria sheet indicates that a future upgrade will increase maximum month flow capacity to 6.36 mgd, and maximum day and peak hour capacity to 8.96 and 14.43 mgd. The loading capacity with the future upgrade will increase to 13,800 lbs/d and 13,110 lbs/d, for BOD5 and TSS respectively. The future upgrade is designated as Phase III, with Phase I being the construction of the new facility and Phase II being the decommissioning of the former WWTP. The District has applied for grant funding for work to enhance the operational efficiency and life expectancy of the WWTF MBR process and equipment. This would be accomplished with the addition of a new feature available from GE, the membrane supplier. The new feature is known as the LEAPmbr system. The design and permitted capacity of the WWTF is based on the 2006 Wastewater Facilities Plan. The actual capacity may be different than anticipated during the design


phase and following refinements in operation or the addition of the LEAPmbr system. Additionally, there may be capacity limitations that could be more readily implemented to support some additional capacity rating. An update of the WWTF engineering report, including critical evaluation of flow and loading capacity, in the context of several years of operation of the new facility, should be completed several years ahead of the anticipated need for Phase III improvements. A more incremental approach may be the result of that analysis. This is a recommended project in the capital improvement plan. FORMER WASTEWATER TREATMENT PLANT The District operated the former wastewater treatment plant (WWTP) until April, 2012. The former treatment process consisted of fine screening, metering, grit removal, aeration, secondary clarification and UV disinfection. Waste solids were stored in a large humus pond. Digested sludge was removed and hauled offsite for disposal on an infrequent basis. The pond was last removed in the year 2000 and the District has entered into a contract to have the remaining biosolids materials removed in late 2016. The new facility was built in a higher elevation location to move out of the Ebey Slough floodplain. The site is separated from the slough by a levee owned and maintained by others. The levee has required emergency repairs in the past twenty years or less to maintain its integrity. The standby generator and appurtenances have been sold as surplus. Some process equipment remains onsite and will be salvaged or disposed of by the 2015 biosolids removal contractor. The existing basins and ponds will remain intact. The District maintains utility service to the site and operates sump pumps to manage water levels in the basins and pond. The District and DOE are continuing to evaluate options for the final decommissioning and ultimate use of the site. INTERLOCAL AND SERVICE AGREEMENTS AND MORATORIA Over its history, the District has executed several interlocal agreements and contracts including those with the City of Lake Stevens, City of Marysville, Hewlett-Packard Company and Evergreen Sanitation. The Hewlett-Packard Company has ceased operations in the area and their property has since been developed as residential plats. Evergreen Sanitation operates a septage pump, haul and filtration facility in the City industrial area. The filtration facility discharges septage filtrate to the District sewer system, per the terms of this agreement. In addition, the District has issued moratoria on several occasions in order to temporarily limit development where the system was deficient in capacity, and to allow time to plan, finance, and construct sewer collection system improvements to serve additional areas around Lake Stevens. Currently, there are moratoria in place for the service areas for Lift Stations 2 and 7. The moratorium for LS2 was amended with a resolution in 2014 implementing a partial and temporary


lifting of the moratorium, to allow a limited number of additional connections. Copies of moratoria resolutions are included in Appendix B. CITY OF MARYSVILLE In April 1999, the City of Marysville and the Lake Stevens Sewer District entered into a Sewerage Disposal Agreement to address sewer service in a “overlap” area created as a result of prior overlapping planning and service areas. This area is located southeast of the City of Marysville between State Route 9 to the east, 83rd Street to the west, Soper Hill Road to the south, and 44th Street to the north. The District previously annexed an area in the Marysville UGA (Plat of Ridgewood) and continues to serve those properties directly. The City has since completed the Soper Hill Pump Station and a 12-inch gravity pipeline along this road. The Plat of Ridgewood Park Phase 1 is sewered and under this agreement the District will continue to own and operate this sewer system. CITY OF LAKE STEVENS In May of 2005, the District and City of Lake Stevens entered into an agreement entitled “Unified Sewer Services and Annexation Agreement.” This agreement conveyed all of the City’s sewer system, including equipment to operate and maintain the system, to the District for operation and management and lays the ground work for the eventual assumption of the District sewer system by the City in the future.

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TAB

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ewer

Inve

ntor

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Lift Station ID No.

Year Online

Station Type (1) Manufacturer

No. of Pumps Pump Model

Motor (hp) TDH (ft)

Confirmed Capacity

(gpm)Size (2)

(in)Length

(ft) Material (3)Discharge Manhole Generator Data

Telemetry (4)

LS1 1969 W/D Smith & Loveless 2 4B3 7.5 56 59 4 1,120 AC 58-2 None Yes

LS2 1969(5) W/D Fairbanks Morse 2 5432K 7.5 48 239 6 364 AC LS12 15 kW, 18.75 KVA, LP Gas, Kohler 15R72

Yes

LS3 1970 W/D Fairbanks Morse 2 5432K 7.5 40.5 307 6 448 AC 23T 20 kW, 18.75 KVA, LP Gas, Kohler 15R72

Yes

LS4 1970 W/D Fairbanks Morse 2 5432K 20 76.5 580 8 123 AC 35 30 kW, 31.25 KVA, LP Gas, Kohler 30R72

Yes

LS5 1969(6) W/D Smith & Loveless 2 4B2A 15 50 800 9.5 1,050 HDPE LS15 200 kW, 156 KVA, Diesel, Chrysler-Nissan Surge Tank

Yes

LS6 1970 W/D Fairbanks Morse 2 5432K 7.5 77.5 312 6 200 AC 77 30 kW, 31.25 KVA, LP Gas, Kohler 30R72

Yes

LS7 1980 VP Hydronix 181V 2 40MPC 7.5 43 200 6 1,240 PVC 801A 40 kW, 28 KVA, Diesel, Lima Ser R 360

Yes

LS8 1980(7) VP Smith & Loveless 2 4C3B 30 135 570 8-10 2,800/ 3,280

HDPE/DI 2823 100 kW, Diesel, Cummins/Onan 100 DGDB

Yes

LS9 1980 GP Myers 1 WG20-21 2 40 30 2 305 PVC 815 None NoLS10 1980 GP Myers 2 WG20-21 2 40 30 2 560 PVC 811 None YesLS11 1983(8) Recessed VP Hydronix/Paco 2 NCVU-412-11-12 25 30 400 6 65 PVC 3947 60kW, Cummins/Onan DGDB Yes

LS12 1996 W/D Cornell 3 4x4x14T – VC18DR 75 193 2,000 12 3,520 DI 2535 250 kW, Diesel, Caterpillar 3306 DITA

Yes

LS13 2003 GPLS14 2000 VP Smith & Loveless 2 4B2D 10 38 480 6 980 DI 2825 35 kW, Diesel, Cummins/

Onan 35 DGBBYes

LS15 2003(9) W/D Smith & Loveless 4 8D4C 125 170 5,250 19.4 3,360 HDPE 91B 350 kW, Diesel, Cummins/ Onan 350 DFCC

Yes

LS16 2003 VP Smith & Loveless 2 4B2D 7.5 62 155 4 717 DI, CL 52 3027 25 kW, Diesel, Cummins/ Onan 25 DKAF

Yes

LS17 2005 VP Smith & Loveless 2 4D4B 40 150 290 6 3,200 HDPE 3345 250 kW, Diesel, Cummins/ Onan 250 DQDAA

Yes

LS18 2007 VP Smith & Loveless 2 4D4B 25 113 290 6 1,386 DI, CL 53 3342 80 kW, Diesel, Cummins/ Onan 80 DGDA

Yes

LS19 2008 VP Smith & Loveless 2 4D4B 75 226 290 6 2,865 DI 3476 200 kW, 250 KVA, Diesel, Cummins 200 DSHAC

Yes

LS20 2012 VP Smith & Loveless 2 8D4V 100 140 1,650 12 5,588 PVC 3411 400 kW, 500KVA, Diesel, Cummins, 400 DFEH

Yes

Removed

Inventory of Sewage Lift Stations and Force MainsTABLE 5-2

Station Information Pump Information Design Capacity Force Main Information Other (9)

Sanitary Sewer Comprehensive Plan

Lake Stevens Sewer District

October, 2016

CHS Engineers, LLC

LS21 2006 VP Smith & Loveless 2 4B2D 10 66 130 4 3,027 DI C82 35 kW, Diesel, Cummins, DGBB

Yes

LS1C 1970 W/D Smith & Loveless 3 4C2 50 112 650 Two - 8 2870 (each)

AC/AC 79 135 kW, Diesel, Kohler 135ROZJ

Yes

LS2C 1970(10) W/D Smith & Loveless 2 4B28 15 40 700 8 920 CI B14 50 kW, LP Gas, Cummins Yes

LS3C 1970 W/D Smith & Loveless 2 4B2A 7.5 43 200 4 660 DI C32 35 kW, 37.5 KVA, Diesel, Cummins

Yes

LS4C 1979 Submersible Flygt 2 3085 3 27 100 6 1,137 PVC D36 None YesLS5C 1992 Submersible Meyers 2 4VX 50 M4-23 5 30 200 4 145 PVC D34 None YesLS6C 1994 W/D Smith & Loveless 2 4B3A 5 55 100 4 337 DI C36 35 kW, 37.5 KVA, Diesel,

CumminsYes

LS7C 2007 Submersible Flygt 2 NP3102.090 6.5 45 210 4 110 HDPE LS8C FM 40 kW, 44 KVA, Diesel, Cummins

Yes

LS8C 2000(11) W/D Smith & Loveless 2 6D5 100 260 670 10 5,300 DI 1182 230 kW, Diesel, Kohler Yes

LS9C 1999 VP Smith & Loveless 2 4B2B 3 33 150 4 530 DI C102 35 kW, Diesel, Cummins Yes

(1) W/D = Wet Well/Dry Well; W = Wet Well; GP = Grinder Pump; VP = Vacuum Prime.(2) All force mains are inside diameter.(3) AC = Asbestos Cement; HDPE = High Density Polyethylene; PVC = Polyvinyl Chloride; DI = Ductile Iron; CI = Cast Iron.(4) All stations equipped with alarm auto-dialers, except as noted. Three systems in service.(5) In 1998, the pumps and impellers were replaced after LS12 was completed.(6) In 2003, LS5 modified to pump to LS15 in new force main. Pumps replaced to downgrade capacity to 800 gpm.(7) LS8 upgraded in 2000.(8) Originally, force main discharged into MH 55, then MH 45. Connected to MH 3947 with completion of SW Interceptor.(9) LS15, 18 & 8C are equipped for oxygen injection. Flow meters are installed at 5, 12, 15, 17, 20, 1C, 8C.(10) LS2C, modified 2004.

(11) LS8C, New generator, pumps, and flow meter in 2003.

Sanitary Sewer Comprehensive Plan

Lake Stevens Sewer District

October, 2016

CHS Engineers, LLC


TABLE 5-3

WWTF Influent Limits and Upgrade Thresholds

Criteria Permit

Maximum Year

Reached

85% of Permit

Maximum Year

Reached Maximum Month Design Flow (MGD) 5.01 2025 4.26 2019

Monthly Average Dry Weather Flow (MGD)

3.88 Beyond 2035 3.30 2030

BOD5 Influent Loading for Maximum Month (lbs/day)

10,730 2029 9,121 2021

TSS Influent Loading for Maximum Month (lbs/day)

10,190 2029 8,662 2021

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FIGURE 5-1Existing Sewer System

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91st Ave NECampus ParkGlenacresLS 12LS 14LS 15LS 17LS 1CLS 2LS 2CLS 5LS 8LS 8CMeridianVernon Road WestSW Int.VRD

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FIGURE 5-4LIFT STATION & TRUNK BASINS

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3049

3172A3170A

1546A

2637A

2729A 2733A

37203719

3801

38023806

38073808

38093810

3811 3812

38133805

38423817

3816 3815

3713

3314 331338153814 3818

38193820

3821 3822

3827 3826382538243823

3828

3829 38303831 3832 38333833

38343835

3833

3836

3837 38383839

3840

3718 37173716

3715 3714

3743 37443745 37463747

37513748

3753

3764

3765

3766

3767 3768

3769

3770 3771

3772

37733774 3775

3776

LS 20

LS 16

91st

SR 9

SR 204

Verno

n

1st

81st

83rd

Lund

een

Sunn

yside

Market

3rd

10th

87th

2nd

4th

85th

92nd

11th

88th

Frontier

79th

14th

13th

82nd

12th

80th

86th

Acce

ss

8th

Frontage

76th

90th

9th

Meridian

84th

84th

4th

1st

82nd

4th

81st

1st

87th

81st

85th

86th

Verno

n

12th

90th

13th

83rd

84th

12th

Acce

ss

9th

11th

90th

10th10th

9th

85th

10th

Verno

n

9th

Vernon

1st

87th

14th

1st

11th

8th

10th

11th79

th

86th

10th

87th

13th

2nd

11th

90th


SYSTEM DETAIL A

£500 0 500250

Feet

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!91

25

26

3592

91B

91A

25-1

FLOW FULLYDIVERTED

LegendCity of Lake Stevens

! Cleanout! Manhole" Lift Stations

PIPE DIAMETERUnkown68101215161821243036AbandonedForce Main

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91st

SR 9

1st

Market

2nd

90th

Meridian

87th

1st

1st

1st1st

1st

90th

Meridian

41

43

42

44

45

46

42A

43A

3748 3749

37503751

37523753

37463747

374537443743

31723171

3170

1446

25252524

1582

1583

1584

1585

1342

1343

2523

1581

2522

2725

2521

40-1

1586

1587

1588

2520

1450 43-11449

2724

2719

2720

2721

2519

2797

2518

27962793

1448

2794 2795

25162517

1452

1447

2722

2723

1459

1687

1457

1455

1454

1453

1456

1688

1689

16911690 1686

2799

2803

2802

2798

27322728 2730

27312734

3172A

3170A

2523A

2729B2729A

2733B

2733A


SYSTEM DETAIL B

£200 0 200100

Feet

ABANDONEDLS 11 FM




SEWAGE FLOWS IN MANHOLE 42 ARE PRIMARILY DIRECTED TO THE WEST. WHEN FLOWS EXCEED 4 INCHES IN DEPTH, THEN "OVERFLOW" IS SPLIT EQUALY TO THE WEST AND NORTH.

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LS 2

LS 12Davi

es

3rd

2nd

Davie

s Loo

p

12

14L13

546

31573158

31593160

3161

14-3

1603

13-1

1605

14-1

1607

1606

2727

2726

14-2

14-4

1604

1602

14-2-1

14-2-314-2-2


SYSTEM DETAIL C

£100 0 10050

Feet

NO CONNECTION HERE




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LS 1418th

15th

Lake

Stev

ens

Davies

107th

3374

3379

3375

3376

3380

3377 3378

3373

2823

2824

2825

2826

2825A


SYSTEM DETAIL D

£100 0 10050

Feet

10-INCH FMFROM LS 8




6-INCH FM

10-INCH FM NOT IN SERVICE.TO BE EXTENDED FROM LS B7TO SOUTHWEST INTERCEPTOR IN FUTURE.

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108th

18th

106th

107th

19th

Lake

Stev

ens

106th

107th

3342 3341

3241

3242 3243

3244

317631753179

31743173

3177 31783180

32453181

2826

2831

2833

2834

30763075

3077

30743073


SYSTEM DETAIL E

£100 0 10050

Feet

6-INCH FMFROM LS 17




FROM LS 18(FLOW TO LS 17)

TO LS 17GRAVITY CONNECTION FROM 3244 TO 3245 IS FEASIBLE BUT PRESENTLY PLUGGED

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LS 5

Verno

n

Access

16th

Access

53

50

52

49

48

47

46

47-1

12011200

1002

1001

52-2

52-3

46-1

45-245-3

256125622563

L52-1

L45-1

45-3M


SYSTEM DETAIL F

£100 0 10050

Feet

FM ABANDONED




19.4-INCH FM9.5-INCH FM

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LS 15

99th

101s

t

Lundeen

Callow

Lake

28th

Vernon

Alder

Sandy Beach

24th

106th

Lake View

Madrona

104th

25th

Macn

augh

ton

100th

Access

Vernon

Lundeen

72

73

7158

57

63626160

59

83

6869

7067

66

82

8180

6564

56

L84

3275

67-C

60-2

59-1

59-2

59-3

59-4

59-5

58-B

1173

83-A

11721171

1184

1185

1186

1187

1193

1194

1195

1312 1318

1314

1313

1319

1292

59-6

59-7

62-1

62-5

62-4

62-3

62-2

60-1

57-A

1311

1183

1170

68-1

1327

1326

71-B

68-B67-B66-B

65-B64-B62-B 63-B

59-B

58-D

58-C

57-B

12701290

1291

56-B

55-A55-C

54-B

54-A

53-B53-A

68-3A

68-2A

54


SYSTEM DETAIL G

£300 0 300150

Feet




ALL FLOW DIVERTED AT MH 71

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ell

Lakesh

ore

116th

G9

B1

A2A3

G1

A4

A5

A6

A7

A9

G2

G6

G7

A2A

A4A

G10

G11

G13

G14


SYSTEM DETAIL H

£100 0 10050

Feet




8-INCH FM

8-INCH FM

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LS 8C

117th

Grade

26th

32nd

34th

22nd

116th

123rd

114th

25th

29th

28th

30th

121s

t

Catherine

125th

124th

118th

Bryce

Hartfo

rd

24th

120th

21st

23rd

115th

Mead

ow

33rdKelli27th

Access

Lund

quist

113th

122n

d

Doe

Crystal

31st

Mand

olin

33rd

Access

21st

25th

114th

21st

29th

21st

116th

114th

118th

120th

22nd

33rd

29th

21st

117th

116th

28th

30th

118th

22nd

120th

115th

29th

28th

120th28th

30th

32nd

123rd

21st

33rd

H2H3

H4H8

H5

H6H7

M1M2

M3

M4

D9

D7D6

G83 G82

H82H80

HA4

HA9

HA8HA7

HA1HA2

HA3

HA6HA5

H87

H86

H85

H83

H84

H81

BV5 BV4BV3

BV2BV8BV9

G99

G97G98

G94G95

G96

G91

G92

G93

G90 G86G87

G88

G89

BV1 H65 H64

H63H66 H67

H62H61H60

H68

H69

H70

H71H72H73

H74H75

D62

D63

D61D56

D55 D33

D32 D31

D57

D58

G84

G77G78G79

G76

G75

G70

G69

G68G81

G72G73

G74

G71G57G58

G59

G60

G56

G67

G66

G65

G64

G55

G54

G53

G52

G34

G38 G35

G40

G39

G36G37

G42

G43 G44

G45

G48G49

G50

G51 G46

G47

D29

D30

D28 D27 D25

B82

B84B86B85

B87

B88

B89

B83 B81

B80

D23D24

B33

D20D21

D18

D19

H17

H18 H19

H28

H20

H21

H22

H23

H24

H29H38

H39

H30H31

H32

H33H34

H35

H40

H41

H42

D46D47

D48D59

D49D50B29 D45

D43D44B28

B27

D40D51 D39

D41

B76B77B78B79B90

B75B32

B31B34

B30B35B62

B63

B64B67B69B70

B65

B59

B58 B57 B56B61

B60

B49B50B51

B52

B55

B54B53

B41B47 B48

B45

B44

B42B43 B40 B93 B37

B38

B39

B26

B25

B24B36

D12

D11

D10

D37B22B23

B21 B20

D26

D60

39673968

3969

397039603966

39623963

39643965

HA22

D46FD46E D46C

B35A

G31C

G31B

D46B

MH-6

BV18

BV19

BV16

BV17

BV10

BV11BV12

BV13

BV14

G112

G107G108

G110G111G135

G109G134

G115G116G117

G126G127G128

G129

G104G106

G103 G101

BO95

B42A

BV15

H36

D46D

D46A


SYSTEM DETAIL I

£400 0 400200

Feet




WEIR

PLUGSPLUGSPLUGSPLUGS

PLUGS

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LS 7C30th

31st

Ceda

r

29th

28th

109th

112th

31st

CR3

CR2CR4

3267 3268

32703269

32653264

32633262

3261

3271

3260

327232733632

3631A100

A101


SYSTEM DETAIL J

£100 0 10050

Feet




10-INCH FMFROM LS 8C

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SANITARY SEWER COMPREHENSIVE PLAN...Sanitary Sewer Comprehensive Plan iii October, 2016 Lake Stevens...

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