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Planning and building new wastewater infrastructure is extremely complex. It can easily take a decade or more to go from identifying a project need to cutting the ribbon on a newly completed facility.

System planning is an area in which King County and its sewer utility customers work together closely.

The clean water services provided by King County have protected water quality, public health, and our environment for decades. We are starting work on a wastewater systemwide comprehensive plan that will guide the County’s work for decades to come. We want to have a regional discussion about our wastewater system and protecting our local waterways and health in the future so we can make the right investments at the right time.

We are committed to a fair and inclusive planning process. To do this, we will aim to break down barriers to involvement and hear from all kinds of people — including long-time participants in water quality discussions and new interested parties. We’ll be working with people at each step of the process to make sure we are on the right track to deliver the best water quality, economic, social, and health outcomes.

Click here to learn more about the project.

To sign up to receive future updates or for questions, contact Erika Peterson at or 206-477-5525.

Under the state's Growth Management Act  (Wikipedia), local jurisdictions are required to plan essential public facilities such as wastewater treatment to meet their population growth needs. King County is in turn legally required to build wastewater treatment capacity for the jurisdictions and agencies it serves in the central Puget Sound region.

To ensure planning decisions reflect the interest of the regional ratepayers, who ultimately pay for these investments, King County carefully reviews local comprehensive plans and compares growth projections to census data and population forecasts prepared by the Puget Sound Regional Council . The county also looks at its own wastewater flow and monitoring data, and further truth-tests projections by running the data through sophisticated system models to determine where future system capacity might be needed. King County's modeling data has historically proved highly accurate and reliable.

The 34 local sewer agencies that pay King County for safe, environmentally responsible sewage treatment are represented by the Metropolitan Water Pollution Abatement Advisory Committee, or MWPAAC (pronounced "Mew-Pack").

MWPAAC members help ensure we're making cost-effective decisions based on legitimate, emerging needs by working with the county to develop criteria to prioritize and plan projects.

Once project needs are identified, the county develops plans that it shares with MWPAAC's engineering subcommittee and other stakeholders, which might include local elected officials and jurisdiction staff, business leaders, permitting agencies and community members.

The King County Council and County Executive review the comprehensive plans, and only after the council votes its approval do plans for new projects move forward.

King County is currently in the midst of the Regional Wastewater Services Plan, or RWSP, adopted in 1999 to ensure the system is meeting growth through 2030. The RWSP includes the many projects listed in the RWSP annual report.

Because investments in wastewater infrastructure are significant, the Wastewater Treatment Division's system planning has checks and balances to ensure there is adequate oversight and accountability in carrying out our capital program.

The RWSP requires regular status reports on the projects be delivered to council members. On very large projects, the King County Council might appoint its own independent monitoring consultant to review project plans, schedules, and associated cost trends during construction. Additionally, the King County Council presides over the budget process and votes to set sewer rates, providing additional oversight on financial matters.

Though clean water is our ultimate goal, the Wastewater Treatment Division also defines success in running an agency that is well-managed, fiscally responsible and compliant with its state and federal pollution control requirements.

RWSP list of planned projects through 2030. Source: Ratepayer Report, April 2016

King County plans ahead to make sure its regional wastewater system keeps pace with growth and continues to protect public health, the environment and the economy for both present and future wastewater customers.

The 1999 Regional Wastewater Services Plan, or RWSP, outlined wastewater system investments through 2030. Here’s an overview of planned projects we’re undertaking through 2030.

King County has started work on a new Clean Water Plan to take us to and beyond 2030.