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Sewer Utilities

This page provides general information about sewer utilities in Washington State, including information on statutes and regulations, sewer planning, side sewers, sewer maintenance and public health, permitting and contracting, coordination and mergers, and sewer rates and funding.

Overview

Sewer utilities manage wastewater, protect public health, and ensure treated water is safely returned to the environment. Cities, counties, sewer districts, public utility districts (PUDs), or some combination of the above, may all provide sewer systems to residents.

The definition of a sewer utility can vary by jurisdiction. For instance, on-site septic systems (OSS) are generally regulated by county health departments, and are not typically considered part of a city or town’s sewer system. While cities and counties typically manage sewer collection and maintenance within their boundaries, some counties – such as King and Pierce – operate regional wastewater treatment facilities serving multiple local governments.

This page details the legal authority for the development and maintenance of sewer systems in cities, towns, and counties, including sewer planning, maintenance, rate-setting, contracting, and other relevant topics. 

Statutes and Regulations

Several RCWs grant municipal authority for sewer systems.

City and Town Authority

RCW 35.67.020 grants cities and towns the authority to construct, operate, and maintain sewer systems. It also includes provisions for rate setting, system extensions, and the issuance of bonds for financing improvements.

County Authority

Chapter 36.94 RCW provides counties with the authority to establish and operate sewer systems, adopt general sewer and water plans, and manage related infrastructure. RCW 36.94.140 authorizes counties to charge for the operation and maintenance of county-owned sewerage systems.

Although municipalities have primary responsibility for sewer systems, they are not required to directly provide all services. County governments are given authority to contract with private entities or other jurisdiction “for the establishment, maintenance and operation of all or a portion of a system or systems of sewerage and/or water supply” under RCW 36.94.190.

PUDs

PUDs are authorized to establish local utility districts for provision of utility services, including sewer facilities under RCW 54.16.120.

Tribal Government Authority

Federally recognized tribal nations have authority to provide utilities including sewer utilities in their jurisdictions. The legal authority of tribal nations is found in their retained inherent sovereignty, treaty rights, and federally conveyed rights. The U.S. Environmental Protection Agency (EPA) provides consultation with tribal governments including regarding operation of wastewater utilities. In 1984, the EPA adopted the Policy for the Administration of Environmental Programs on Indian Reservations that established a tribe’s authority to conduct reservation-wide environmental programs similar to those delegated to the states.

In addition, state law in chapter 39.106 RCW authorizes Indian tribes to form joint municipal utility services with state and local governments. Chapter 39.34 RCW, legal authority for Interlocal Agreements (ILAs), also includes tribal governments.

Water-Sewer Districts

A water-sewer district is a type of special purpose district created to provide wastewater collection, treatment, and disposal services within a defined area. Water-sewer districts are governed by elected boards of commissioners and are authorized under Title 57 RCW.

Chapter 35.13A RCW details the process by which cities can assume jurisdiction over water-sewer districts, including provisions for the transfer of assets and liabilities.

List of Water-Sewer Districts

For information on individual sewer providers in Washington State, the following resources are helpful:

Sewer Planning 

Effective sewer planning ensures that sewer infrastructure supports growth and environmental management. Several state laws require local jurisdictions to plan for sewer services as part of broader land use and public facility planning efforts. These laws also authorize local governments and special purpose districts to build, expand, and finance sewer systems.

Statutes within the Growth Management Act (Chapter 36.70A RCW)

  • RCW 36.70A.030 – Defines key terms in the Growth Management Act, including classifying sewer systems as “urban governmental services” that must be provided within designated urban growth areas.
  • RCW 36.70A.110 – Requires local governments designate urban growth areas (UGAs) where public services like sewer systems must be planned for future development.
  • RCW 36.70A.130 – Mandates periodic review and updates of comprehensive plans to ensure sewer and other infrastructure services align with expected growth.

Other Sewer Planning Authority

  • RCW 36.94.020 – Authorizes counties to establish and manage sewer systems in unincorporated areas.
  • RCW 57.16.010 – Permits water-sewer districts to adopt and revise comprehensive sewer system plans, which guide the extension, operation, and financing of sewer infrastructure in areas they serve.

Examples of Sewer Planning

Side Sewers

Side sewers (sometimes known as "building sewers") connect individual buildings to the sewer main. There are no specific statutes or court cases that we are aware of addressing side sewer ownership, but MRSC generally considers side sewers, including the portions within the public right-of-way, to be owned by the private property owners, as side sewers are privately constructed and benefit private property interests, rather than the public sewer system as a whole.

As such, side sewer repair and replacement is generally the responsibility of the property owner, as it could potentially be considered a gift of public funds for a public utility to maintain side sewers benefiting private property interests. However, there are exceptions if the private benefit is incidental to the overall public benefit. See AGO 2009 No. 5.

Some jurisdictions opt to maintain the portion of the side sewer within the public right-of-way and assign responsibility to the property owner for only the portion of the side sewer on private property (from the building to the property line). Others hold property owners responsible for the entire side sewer, all the way from the building to the sewer main, including the portion within the public right-of-way (from the property line to the sewer main).

Side sewer maintenance and repair may come as a surprise to property owners. Repairs can be expensive, and homeowner's insurance usually does not cover the portion of the side sewer between the property line and the sewer main. At least one jurisdiction – Tacoma, see below – requires prospective buyers and sellers to be given a city flyer educating them about side sewers prior to closing.

Below are selected examples of side sewer policies and related documents.

Side Sewer Ownership & Responsibility

  • Bainbridge Island Municipal Code Sec. 13.12.060 – City is responsible for the portion of the side sewer lying within the street right-of-way or easement.
  • Ilwaco Municipal Code Sec. 14.06.120 – Property owner must pay all costs related to side sewer installation and connection. Property owner must pay for all side sewer repairs on the property and must pay to fix any blockages within the public ROW that originate on private property.
  • Kitsap County
    • Code Ch. 13.12 – Distinguishes between "side sewer" (sewer main to property line) and "building sewer" (property line to building).
    • Side Sewer Brochure – Information for property owners about what a side sewer is, how to inspect and maintain it, and how to prevent blockages.
  • Spokane County Code Sec. 8.03.1870 – Property owner is responsible for maintenance and repair of entire side sewer, including the portion within public ROW.
  • Sumner Municipal Code Sec. 13.16.290 – Building sewer (side sewer) located in public ROW is property of the city and shall be maintained, repaired, and replaced by the public works department. Property owners are responsible for side sewer on their property.

Side Sewer Construction, Maintenance & Regulations

Sewer Maintenance and Public Health

Maintaining sewer systems protects public health and prevents environmental contamination. Local governments are responsible for operating public sanitary sewer systems and ensuring that both public infrastructure and private connections, like side sewers, are functioning.

Public Health & Safety

  • Chapter 18.210 RCW – On-Site Wastewater Treatment Systems – Designer Licensing; sets licensing and design standards designers to ensures systems are built correctly.
  • Chapter 70A.115 RCW – Large On-Site Sewage Systems; covers permitting, operation, and penalties for violations.
  • Chapter 70A.212 RCW – Domestic Waste Treatment Plans - Operators; requires certification for operators of wastewater treatment plants.
  • Chapter 90.48 RCW – Water Pollution Control; provides broad authority to prevent and manage water pollution from wastewater. Includes rules for discharges, system upgrades, reclaimed water use, and management of sewer overflows.
  • Chapter 43.20 RCW – State Board of Health; allows the Board of Health to adopt rules for sanitation and wastewater systems.
  • Chapter 70A.300 RCW (formerly RCW 70A.105) – Hazardous Waste Management; regulates hazardous waste to prevent harmful substances from entering wastewater systems.

Examples of Sewer-Related Public Health & Safety Documents

  • Grays Harbor County On-Site Sewage Section – Protects public health by permitting and inspecting septic systems, certifying professionals, investigating complaints, enforcing regulations, and educating homeowners.
  • Issaquah Side Sewers – Protects public health by requiring property owners to maintain their side sewers, preventing sewage leaks and backups. The city manages main sewer lines and offers guidance to residents on maintenance.
  • Kitsap Public Health District Drinking Water & Onsite Sewage (DWOS) Program – Inspects and permits septic systems and small water systems throughout the county. Regular inspections helped identify problems like failing septic systems and expired water system permits.
  • Kittitas County Liquid Waste Program – Manages on-site sewage systems through site evaluations, licensed designs, and permits. Inspections ensure systems meet safety standards.
  • Puyallup City Standards Sec. 400 – Sanitary Sewer System; requirements like minimum pipe size, proper slope for flow, grease interceptors, and regular manholes protect infrastructure and reduce health risks.

Failing Septic Systems

Cities and towns typically defer to county health departments for the regulation of failing on-site sewage systems (OSS), also known as septic systems.

  • RCW 70A.110.020 – Defines a "failing" on-site sewage systems OSS as one that threatens public health by inadequately treating sewage, leading to surface discharge, backups, or contamination.
  • RCW 70A.105.030 – Allows local health officers to identify failing OSS and to apply for administrative search warrants to inspect properties when necessary.
  • RCW 35A.21.390 (Code Cities), RCW 35.21.940 (Non-Code Cities), and RCW 36.01.330 (Counties) – Municipalities must provide an administrative appeals process for homeowners whose repair or replacement permits are denied because of local ordinances requiring connection to a public sewer system.

Examples of Septic System Regulations

  • Entiat Municipal Code Ch. 13.10 – Generally requires properties in the sewer service area to connect to the public system. If a private septic system is no longer used, it must be properly closed following health district regulations.
  • Island County Code Ch. 8.07D – Defines OSS failure and outlines requirements for system repair or replacement.
  • Kent Ordinance No. 4210 (2016) – Repealing and readopting sanitary sewer standards. New topics addressed include fats, oils, and grease (“FOG”) and new enforcement provisions.
  • Shoreline Ordinance No. 780 (2017) – Repealing the city’s water and sewer code and replacing it with a new wastewater utility chapter, as required for city’s assumption of the Ronald Wastewater District.
  • Walla Walla County OSS Failure/Replacement Guidelines – Provides procedures for addressing failing septic systems, including permit requirements and financial assistance options.

Fats, Oils, and Grease ("FOG")

Chapter 90.48 RCW (the Water Pollution Control Act) governs discharges of pollutants, including fats, oils, and grease (FOG), into state waters.

Examples of FOG Regulations

Biosolids

Biosolids are sewage sludge that is primarily an organic, semisolid product resulting from the wastewater treatment process. When properly treated and managed, biosolids can be beneficially recycled—for example, as a soil amendment—provided they meet all applicable regulatory requirements.

In Washington State, the management of biosolids is governed by the following statutes and rules:

  • 40 C.F.R. Part 503 – Standards for the Use or Disposal of Sewage Sludge; establishes national performance standards and management practices for the safe use or disposal of biosolids, including pollutant limits, treatment methods, and site restrictions.
  • RCW 70A. 226.020 – Requires the Washington State Department of Ecology to adopt state rules consistent with federal biosolids standards. Local governments must follow any updates.
  • Chapter 70A.226 RCW – Municipal Sewage Sludge-Biosolids; establishes the state’s framework for biosolids management, including definitions, permitting, enforcement, and compliance with federal regulations. It affirms the beneficial use of biosolids when properly processed and regulated, and now includes provisions for PFAS testing and advisory input.
  • Chapter 173-308 WAC – Biosolids Management; provides detailed rules, including requirements for permitting, monitoring, land application, and pathogen reduction, developed by the Department of Ecology for implementing biosolids programs.

The Washington State Department of Ecology’s Biosolids page provides access to laws and rules, permitting information, forms, guidance documents, annual reporting requirements, FAQs, and contacts for support.

Examples of Biosolids Programs

Permitting and Contracting 

Contractor compliance is a significant component of sewer service projects. For both water and sewer connections, municipalities typically require licensed contractors to perform the work. Specifically, Chapter 39.12 RCW governs prevailing wage laws, which ensure contractors comply with labor and wage standards.

For more information, see MRSC’s page on Prevailing Wages.

Examples of Sewer Permitting and Contracting

Municipal codes lay out specific requirements for side sewer permits, which municipalities use to maintain compliance and safety standards.

Coordination and Mergers 

Effective sewer system management often necessitates coordination across multiple jurisdictions. Local governments and special purpose districts may opt to combine operations for improved efficiency, broader service coverage, or cost savings.

For more guidance, see the “Water/Sewer District Mergers and Consolidations” section on MRSC’s Water Utilities page.

Examples of Sewer Utility Mergers, Annexations, and Acquisitions

  • Lake Stevens and Lake Stevens Sewer District Merger – Merging under a 2005 agreement that sets the official merger date in 2033. In 2020, the city attempted to take over the district early, but a Snohomish County Superior Court judge ruled that the 2005 agreement was legally binding. The merger will proceed on the original 2033 timeline.
  • Shoreline and Ronald Wastewater District Assumption Transition Plan (2016) – In 2017, Shoreline assumed all assets, staff, operations, and debt of the Ronald Wastewater District. The district was dissolved, and the city began managing wastewater services directly.

Sewer Rates

To maintain financially sustainable sewer systems, municipalities need effective billing systems and rate-setting procedures.

  • RCW 35.67.020 – Grants cities and towns rate-setting authority. Rates must be uniform for the same class of customers and can consider factors such as location, cost of service, and conservation goals.
  • RCW 36.94.140 – Authorizes counties to establish and collect rates and charges for sewerage, water, and drainage systems. Rates may vary based on factors like the cost of service, conservation efforts, and capital contributions.
  • RCW 57.08.081 – Water-sewer districts may fix rates based on classifications, usage, and other reasonable considerations.

For more information, see MRSC’s pages on Utility Taxes and Utility Billing, as well as Utility Discounts and Financial Assistance Programs.

Examples of Sewer Rates and Financing

  • Issaquah Municipal Code Ch. 13.70 – Rates, Charges, and Assessments. Sets sewer rates through ordinances passed by the City Council. Rates include a fixed city service charge, a fixed King County treatment charge, and a usage-based fee.
  • Napavine Municipal Code Ch. 13.08 – Sewer Service System. Sets sewer rates through local ordinances and resolutions approved by the city council. Outlines rate categories for different types of users and includes rules for billing schedules, payment deadlines, and penalties.
  • Redmond Municipal Code Ch. 13.16 – Water and Sewer Service Rates. Sets sewer rates through city council decisions. Different users, like homes and businesses, pay different rates.
  • Snoqualmie Municipal Code Ch. 13.08 – Sewer Service Rates and Charges. Rates are based on financial studies and reviewed through a public process. The city also charges one-time fees to support future system capacity. These fees are updated annually using cost indexes.
  • Thurston County Code Ch. 15.12 – Water and Sewer Charges, Rates, and Fees. Sets sewer rates through a yearly process approved by the County Commissioners. New users pay one-time fees to cover infrastructure. Larger projects are funded through utility fees, real estate taxes, or special districts.

Rate Setting 

Local governments must consider financial goals, revenue needs, cost allocation, and rate structure. Rates must cover costs, be fair, and support efficient use, while also reflecting community priorities. Below are selected examples of sewer rate schedules, studies, and RFPs.

For examples of residential wastewater and stormwater utility rates, see the Department of Ecology Washington State Residential Utility Rates Dashboard. Also see the Association of Washington Cities (AWC) Tax and User Fee Survey (member login required).

Rate Studies & Schedules

Rate Studies

Financing Programs

Recommended Resources

Below are some useful resources related to public sewer utilities.

Biosolids

In-State/Regional Resources

Out-of-State/National Resources


Last Modified: April 06, 2026