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Wastewater Treatment Division (WTD) operations and projects

WTD operations staff remain on the job 24/7 to ensure the region’s wastewater treatment service continues. More information on how to report a problem you believe may be related to the County’s wastewater treatment system is available here:

The King County Wastewater Treatment Division remains committed to sharing information and gathering feedback from community members about its work and projects. WTD staff remain available to answer questions via email and phone during regular business hours. Project information lines remain available and are being monitored for ongoing construction projects.

Project update

January 2021

In 2017-18, this project studied soil, groundwater, surface water flow, and street conditions in the six square mile project study area to identify the best locations for Green Stormwater Infrastructure to be installed. In 2018, the County conducted public outreach to share information about the project and request input on community values around Green Stormwater Infrastructure benefits and challenges, and the balance of benefits and costs the project will consider when choosing how and where to install Green Stormwater Infrastructure in the area. (See Project library.)

Having conducted a major evaluation of the project study area, we are pausing our next steps to ensure that we are aligning with the County’s Clean Water Plan, a system-wide planning effort, which is currently being developed.

We wish to thank everyone who has taken part in our outreach to the community so far. In the meantime, the County continues to commit to Green Stormwater Infrastructure in the project study area through the RainWise rebate program.

Project description

King County is beginning a green stormwater infrastructure project in north Seattle. This project will install facilities to help control a combined sewer overflow in Portage Bay. In 2017-18, the project team will study soil, groundwater, surface water flow, and street conditions in the project area to identify the best locations for facilities to be installed.

In this first phase of the project the County will consider what types of green stormwater infrastructure it should build, and where within the study area they should be installed. Some options include different types of bioretention and permeable pavement in alleys or streets. Learn more!

Project study area

The project will select sites for installing green stormwater infrastructure from within the area below.

Study area is near Green Lake, Seattle  Click to view more of map .

Approximate boundaries are intended for planning purposes only. Further study and evaluation will be completed prior to selection of any site.

Project need

In the University CSO Basin in Seattle, heavy rains can cause sewers to overflow into Portage Bay approximately six times per year. This project will install facilities to help control these overflows. Learn more about King County’s CSOs.

What is green stormwater infrastructure?

Green stormwater infrastructure—also called natural drainage—mimics nature by slowing or reducing polluted runoff close to its source. It also treats polluted runoff from roads, roofs, and parking lots by capturing and cleaning it before it harms our waterways. Learn more!

Your feedback 

The County will share its evaluation of two to four alternative ways of doing green stormwater infrastructure with the public, and ask for your feedback online and through community events. Visit the public involvement page.


Green stormwater infrastructure installed at a Roosevelt neighborhood church:

The County’s green stormwater infrastructure project in West Seattle:

The big picture:

RainWise rebates:

  • Many residents of this area can install their own green stormwater infrastructure (rain gardens and cisterns) on their own property funded by an average $4,400 rebate. Check your eligibility and learn more .

houseThe County will consider installing different types of green stormwater infrastructure in the public right-of-way, including types of bioretention in planting strips and permeable pavement in alleys or streets.