Skip to main content
King County logo

Project update

June 2017

The North Lake Sammamish Flow Diversions Alternatives Analysis project is not active at this time. The County expects to finalize its selection for a consultant team by late 2017. See the tentative project schedule below. Updates about the project will be provided here when available.

Project description

Currently, flows from the North Lake Sammamish Basin are routed to the South Treatment Plant through the East Side Interceptor (ESI). This project will divert up to 43 million gallons per day of wastewater from the North Lake Sammamish Basin and send them to the Brightwater Treatment Plant. This project is identified in the Regional Wastewater Services Plan (formerly named “York Pump Station Modifications”) as being necessary to maintain the ability of the ESI to convey peak flows during a 20-year storm event. The ESI is expected to reach peak flow capacity in 2021.

North Lake Sammamish Flow Diversion Project: impacted facilities 

Project schedule

3Q 2017 Procure design consultant
1Q 2018 Alternative analysis complete 
3Q 2018 Predesign complete
3Q 2019 Final design complete
1Q 2020 Bidding and award
1Q 2020 – 4Q 2021 Construction


Contact us

Contact Monica Van der Vieren community services lead at:



Project location


Back to the capital projects overview map .