Georgetown Wet Weather Treatment Station

The Georgetown Wet Weather Treatment Station is located at the corner of 4th Avenue and South Michigan Street in Seattle’s Georgetown neighborhood. The station earned the coveted “Platinum” designation from the Institute for Sustainable Infrastructure’s Envision rating system. This is the first Platinum-awarded Envision project in Washington and recognizes the County’s commitment to sustainable communities and the environment.

Educational programming and tours

We offer education programing and public tours of Georgetown Wet Weather Treatment Station. Come learn about what a Wet Weather Treatment Station is, how the process works, and the importance of clean water.

Visit our education page to learn more about these programs and view the events calendar to see what else is coming up.

What happens at the Georgetown Wet Weather Treatment Station?

When there are storms, rainwater runs off surfaces like roads, sidewalks, and buildings and picks up pollutants. This water, called stormwater runoff, is the leading threat to Washington’s urban waters. The Georgetown Wet Weather Treatment Station can treat up to 70 million gallons of combined rain and wastewater a day that would otherwise discharge directly to the Duwamish River during heavy storms.

Take a Tour of King County’s new Georgetown Wet Weather Treatment Station

Treatment process

Treatment process at Georgetown Station on rainy days. Learn more about the steps in the process:

1. Entrance gate

Large storms cause the "entrance gates" of the Georgetown Station open when the pipes get too full. This allows the combined stormwater and wastewater from the two main pipes to collect in a tank.

2. Storage tank and pump station

The large storage tank can collect and hold up to 1.1 million gallons of stormwater and wastewater. It will provide a controlled flow of water to the next step for treatment. Metals screens inside the storage tank filter out plastics, flushable wipes, and street litter. The trash is collected and trucked to a landfill. The water is then pumped to the sedimentation tanks.

3. Odor control

Smelly air is collected from the treatment station, cleaned with carbon filters, and then released.

4. High-speed settling tank

To further clean the water, an innovative process is used to remove the solids from the water. Several materials (sand, polymer and coagulant) are added which help the solids particles stick together and sink to the bottom at a rapid speed. The solids are collected and pumped to a holding tank.

5. Solids holding tank

Solids from the bottom of the sedimentation tank are collected and then sent to West Point Treatment Plant where they will be processed into Loop biosolids. Loop is transported to farms and forests and is used to enrich the soil for growing plants and trees.

6. Disinfection

After the solids have been removed from the water, the clean water is disinfected using ultraviolet (UV) light. The ultraviolet light kills any remaining germs in the water.

7. Outflow pipe

The treated water is piped to the Duwamish River where it is released. 

Sustainability at the facility

King County is committed to sustainable construction practices as well as sustainable facilities.

• The construction team recycled and reused project materials during demolition and construction. Five buildings and about 7,000 tons on contaminated soil were removed from the site, and concrete and old growth timber beams from some of the demolished buildings were salvaged for reuse. View this video to learn more.
• King County is using Green Stormwater Infrastructure (GSI) at the Georgetown Station to protect water quality. GSI uses plants, trees, soil, and engineering inspired by nature to manage stormwater and keep pollutants out of our waterways.
• Installation of solar panels on top of the UV treatment areas roof and the administration/education building reduces reliance on the electrical grid. 
• The Georgetown WWTS earned the coveted “Platinum” designation from the Institute for Sustainable Infrastructure’s Envision rating system.

How do green roofs reduce stormwater runoff?

Green roofs help urban areas act more like a forest. The plants absorb pollutants, like dust and smog, from the air. Soil allows the plants to grow while slowing down and absorbing rainwater, keeping it from overwhelming stormwater pipes during heavy rains. Learn more about green roof benefits.