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King County wants the public’s help in determining future green stormwater infrastructure work in north-central Seattle


Share your priorities with King County to inform how and where to install green stormwater infrastructure investments by attending an upcoming open house or taking an online survey.


To continue protecting public health and the environment, King County’s Wastewater Treatment Division (WTD) plans to construct green stormwater infrastructure in north-central Seattle that will reduce combined sewer and stormwater overflows. 

About six times a year during heavy rainstorms, a mixture of stormwater runoff and sewage from the north-central Seattle area flows into Portage Bay. King County plans to construct natural drainage facilities, known as green stormwater infrastructure, to help address this.

On Oct. 1, 2, 3, and 6, King County’s WTD will host drop-in sessions and an open house to gather community input on green stormwater infrastructure projects in the University CSO Basin area. An online survey is available through Oct. 9.

Online open house and survey

Available through Oct.9

Drop-in sessions – 5:30 to 7:30 p.m.

Monday, Oct. 1 
Phinney Neighborhood Association
6532 Phinney Ave. N.

Tuesday, Oct. 2 
Green Lake Community Center
7201 E. Green Lake Dr. N.

Wednesday, Oct. 3 
University Heights Community Center
5031 University Way N.E. 

Open house – 10 a.m. to 4 p.m.

Saturday, Oct. 6 
Fairview Christian School
844 N.E. 78th St.

As in many cities around the country, the older parts of King County’s sewer system use the same pipes to carry sewage and stormwater to a treatment plant. During storms, sewer pipes that carry stormwater can fill up and be overwhelmed with the runoff from roofs, driveways, and streets. 

The sewer system is designed to allow these combined sewer and stormwater overflows - a combination of 90 percent stormwater and 10 percent sewage - into local water bodies. Although these combined overflows help prevent backups into homes and businesses, they pose public health and environmental risks.

Communities around the country are increasingly turning to “green” infrastructure as an effective way to control stormwater and reduce pollution and overflows. Green infrastructure mimics nature by slowing or reducing polluted runoff close to its source. It also treats polluted runoff by capturing and cleaning it before it harms our waterways. 

By installing green stormwater infrastructure in our public rights-of-way, King County can:

Help reduce pollution entering waterbodies,
Reduce the size of large, industrial water treatment and storage facilities,
Add greenery and beauty to our neighborhoods.

This green stormwater infrastructure project is in the planning stages, and the County project team has completed a detailed data analysis of the study area that will inform development of options for green stormwater infrastructure.

King County wants to hear from community members about their priorities to inform how and where to install green stormwater infrastructure in north-central Seattle. In this first phase of the project, King County will consider what types of green stormwater infrastructure should be built and general locations for these facilities within the study area.

Technical analysis and community input will help shape the number, type, and location of green stormwater infrastructure facilities. The County plans to return to the community with a selected alternative in early 2019, followed by finalized design by early 2021 and construction as soon as 2021.


Doug Williams, 206-477-4543

About the King County Wastewater Treatment Division
King County’s Wastewater Treatment Division protects public health and enhances the environment by collecting and treating wastewater while recycling valuable resources for the Puget Sound region. The division provides wastewater treatment services to 17 cities, 17 local sewer districts and more than 1.7 million residents across a 420-square-mile area in King, Snohomish and Pierce counties.