West Point Treatment Plant 2022-2023 Capital Improvement Projects

On this Online Open House, you can navigate between the 6 current projects from the menu at the top of this page. On each project page, you can leave feedback for the project team until October 10th at 1pm. Thank you for your time!

Watch an overview presentation of the 2022-2023 Capital Improvement projects:

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Do you have any general questions, concerns, or feedback on the 2022-2023 Capital Improvement Projects?

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To learn more about each project and leave specific feedback, navigate to each project via the menu at the top of the page. Thank you!

To access this Online Open House in Spanish, go to: https://publicinput.com/wptp2022projects-spanish.

For other languages, navigate to the Translate button above the menu and find your preferred language.

Frequently Asked Questions

Prior to the 1900’s, raw sewage from our region dumped directly into Lake Union, Lake Washington and Puget Sound through a series of uncoordinated cesspools and discharge pipes. By the 1950’s the waters of Elliott Bay and Lake Washington were deemed unsafe for recreational use. Fish and wildlife habitat were suffering, too, and there had been a deadly outbreak of typhoid. To address wastewater pollution and other regional issues, the Municipality of Metropolitan (METRO) was approved by voters in 1958. Over the next 9 years Metro engineers designed the West Point Treatment Plant and South Treatment Plant.

West Point was completed in 1966 and provided primary treatment of up to 125 million gallons a day of raw sewage from Seattle and King County. This process removed about 50 percent of the incoming solids and chlorinated the outflow, resulting in significant improvement to local waters.

In 1972, Congress passed the Federal Clean Water Act requiring secondary treatment at all municipal wastewater plants. Locations for a new County treatment plant were sought, but cost was a barrier. In 1988, Seattle granted a permit to expand West Point to meet the new standard.

To keep the facility within the 32-acre required ‘footprint’, 20 percent of the facility was designed to be underground. Stringent noise and odor controls were also factors. Secondary treatment removes 95 percent of the solids and carries out further processing until the outflow is almost clear. The expansion was also designed to address some of Seattle’s Combined Sewer Overflow issues, where heavy rains and prolonged precipitation events can cause the region’s to overflow, threatening public health and the environment.

Capital improvement projects at West Point Treatment Plant focus on protecting ratepayer investments through:

  • improving system reliability
  • protecting worker and public safety and the environment
  • increasing efficiency and meeting increased demand
  • managing a changing climate

In any given year the treatment plant is undertaking a number of improvement projects. Many of these can last from a year in length to multiple years, because they involve engineering planning and design, budgeting, and timing so that they can get done in conjunction with other projects in what is a very small plant area, with plant systems that are highly integrated. Most projects happen well within the plant and have few impacts on the community during construction. Projects include upgrades, replacements, refurbishments, and retrofits that address structural, mechanical, and electrical processes at the plant.

Many of the mechanical, structural, and electrical components at West Point are nearing the end of their useful life. Some have served the plant since it was built in 1966! A lot has changed in Seattle since then and the treatment plant needs to adapt. These capital improvement projects directly address issues related to earthquake safety, growth in population, and climate change. Completing these projects will make West Point more resilient and meet increased capacity needs for many years to come.


Have additional questions? Contact us!

Ryan Harlow, Project Manager