King County Wastewater Treatment Division

King County Wastewater Treatment Division We protect public health and enhance the environment by treating and recycling wastewater.

In the 1950s, wastewater flowed largely untreated into Lake Washington and Puget Sound and many rivers and smaller lakes, fouling water and making a sullied mess of local beaches. In 1958 the voters created Metro and developed a regional wastewater treatment system based on watersheds as opposed to political boundaries. Shortly after Metro was formed, construction began on the county's two existing regional treatment plants, West Point in Seattle's Magnolia neighborhood and South Treatment Plant in Renton, which were officially up and running by 1966. By the late 1960s, regional water quality began improving dramatically. In 1994, King County assumed authority of Metro and its legal obligation to treat wastewater for 34 local jurisdictions and local sewer agencies that contract with King County.

Join us for a hands-on afternoon of plum tree pruning with City Fruit at CitySoil Farm! We’ll start with a workshop led ...
09/14/2026

Join us for a hands-on afternoon of plum tree pruning with City Fruit at CitySoil Farm! We’ll start with a workshop led by City Fruit staff, then move into guided practice on CitySoil’s plum trees. It’s a great chance to learn new skills, help keep our orchard healthy, and enjoy time outdoors with community members.

Date: Saturday, September 19
Time: 1–3 pm
Location: CitySoil Farm, South Treatment Plant in Renton, WA

This event is fully outdoors — bring what you need to be comfortable. Capacity is limited and registration is required. Parking and site access details will be sent to registered participants.

More info and registration here: https://www.eventbrite.com/e/plum-pruning-workshop-at-citysoil-farm-tickets-1998819506952?aff=oddtdtcreator

Last Friday, we hosted community members at our Elliott West Wet Weather Treatment Station for a behind‑the‑scenes look ...
08/28/2026

Last Friday, we hosted community members at our Elliott West Wet Weather Treatment Station for a behind‑the‑scenes look at what’s ahead.

We shared updates on the ongoing project at the Seattle waterfront facility, including the latest design plans and how we’re incorporating community feedback. Everyone also had a chance to step inside the existing station, which will continue to protect public health and the environment by treating untreated stormwater and wastewater during heavy rain events until the new facility is up and running.

Site preparation is expected to begin next summer, with construction planned from 2028 to 2032.

Learn more at KingCounty.Gov/ElliottWestUpgrade

08/26/2026

At our Brightwater Treatment Plant near Woodinville, innovative membrane filters help clean wastewater every day. By the end of the treatment process, the water is 99% cleaner than when it arrived.

Thanks to the diligent maintenance and care of our staff, the original membrane filters lasted beyond their expected service life. Now, as we retire them and install new ones, the timing is especially fitting for Gary, our recently retired Senior Operator in Charge. Gary joined Brightwater 15 years ago as the plant was coming online and watched over these filters throughout their entire service life.

Here’s to a well-earned retirement for both Gary and the original membrane filters—and to the next chapter ahead!

Visual description: Workers use an overhead crane to lift and replace a large membrane filter filled with long, white, spaghetti-like strands. A worker guides it into place, and a plant employee explains the work in a short interview.

What’s the harm in flushing that one disposable wipe? Imagine thousands of your neighbors doing the same thing. Because ...
08/25/2026

What’s the harm in flushing that one disposable wipe? Imagine thousands of your neighbors doing the same thing. Because these wipes don’t break down like toilet paper, they quickly become a nightmare for our wastewater operators who have to unclog the pumps at least once a week. These "rag balls" also put our health and Puget Sound at risk.

Over the years, our Hidden Lake Pump Station in Shoreline has especially been one of the hotspots for wipe clogs.

Find out how we’re tackling the issue and how you can help: https://kingcountywtd.com/2026/08/18/clogged-not-forgotten-the-hidden-reality-when-you-flush-wipes/

Thank you to everyone who stopped by our booths at Duwamish River Community Coalition's Duwamish River Festival or joine...
08/21/2026

Thank you to everyone who stopped by our booths at Duwamish River Community Coalition's Duwamish River Festival or joined the Lower Duwamish Waterway Group boat tour this month! These annual events give us a chance to connect with neighbors, share updates on our wastewater projects in the area, and talk about our ongoing cleanup of the Lower Duwamish Waterway Superfund site alongside our partners at U.S. EPA Northwest Region, Seattle Public Utilities, and The Boeing Company!

Learn about our wastewater projects at kingcounty.gov/sewer-projects
Learn about the Lower Duwamish Waterway Group at www.ldwg.org

08/20/2026

A 25-ton crane, hours of planning, and plenty of elbow grease — that’s what it takes to retire a massive piece of equipment that’s been pumping wastewater around the clock for the last 60 years. Now in its third year of construction, our Raw Sewage Pump Replacement project at West Point Treatment Plant in Seattle reached a major milestone!

Crews successfully removed the first of four original pumps and engines by taking the spiral-shell structure apart in pieces. They are now prepping for the new electric pump and motor — all before the rainy season returns. As of June, our contractor’s skilled trades workforce alone has logged more than 102,000 hours on this project and the grit classifier replacement work!

Learn more about how replacing these aging, biogas-powered pumps will help keep future operations reliable and efficient at https://kingcountywtd.com/2025/05/08/west-point-readies-for-new-pump-system-to-replace-its-aging-heartbeat/

Visual description: A King County employee speaks on camera as crews use cranes and other heavy equipment to remove and replace large pumps inside a wastewater treatment facility.

While excavating near West Armory Way in Seattle for our Interbay Sewer and Odor Control Upgrade Project, crews uncovere...
08/18/2026

While excavating near West Armory Way in Seattle for our Interbay Sewer and Odor Control Upgrade Project, crews uncovered a surprising piece of the past: Sunday edition of The Seattle Times from June 12, 1955!

Digging underground is a big part of the work we do. Before projects begin, we work with the King County Historic Preservation Program to understand whether historical items might be buried in the area. Some projects may also need additional review to meet state, federal, or tribal requirements.

If crews find something unexpected, work pauses while archaeologists determine whether the discovery is historically significant.

In this case, the newspaper turned out not to be a significant artifact. However, our past wastewater projects have uncovered important historical items, which were donated to local museums to preserve our region’s history.

Learn more about the project at kingcounty.gov/InterbaySewer

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201 S Jackson Street
Seattle, WA
98104

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