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Project update

May 2018

In Early May, County outreach representatives surveyed residents at potential locations for early action projects 

While continuing to study soil, groundwater, surface water flow, and street conditions throughout the study area, the project is also planning one to two early action projects. Although construction for this project will take place 2021-23, the project plans to construct these early action projects in 2019. The projects will benefit the overall project design and offer residents a chance to visit and experience green stormwater infrastructure in a neighborhood setting.

April 2018

In February King County crews drilled small wells in public planting strips across the six square-mile Project study area. Crews collected data about soil and water drainage from the wells. This information will help King County find the best places to install green stormwater infrastructure (GSI). Most of the work is complete, but crews will revisit planting strips to take measurements and pictures.

View past updates on the project library page.

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.

Project schedule

4Q 2017 Alternative analysis begins

Early action project schedule

While construction for this GSI project will take place in 2021-23 (see left), the County plans to install early action projects in 2019.

1Q 2019 Alternative analysis complete
3Q 2019 Predesign complete
1Q 2021 Final design complete
2Q 2021 – 2Q 2023 Implementation (bidding, award, construction)


Contact us

Contact Dana West, Community Services, at:

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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.