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About the Lake Hills and NW Lake Sammamish Sewer Upgrade

Get information about the Lake Hills and NW Lake Sammamish Sewer Upgrade schedule and design elements, including efforts to protect the Coal Creek Natural Area.

Project history and location

Apartments and condos along the Sammamish River

Apartments and condos along the Sammamish River 

The Lake Hills Trunk and Northwest Lake Sammamish Interceptor were installed in an area that looked a lot different from today, with a much lower population, less commuter traffic, and different values and protections for the natural environment and recreation areas.

The Lake Hills Trunk and Lake Sammamish Interceptor create a system that will be replaced as part of the Lake Hills and Northwest Lake Sammamish Sewer Upgrade Project. The Lake Hills Trunk is the older section of the pipeline, and was built in the 1950s. This includes the portion of the pipeline that runs along West Lake Sammamish Parkway and the Idlywood neighborhood. The Lake Sammamish Interceptor portion of the pipeline was built in the 1970s. This section runs along Marymoor Park and the West Lake Sammamish Trail.

The project team looks at route options that consider constructability, environmental impact, permitting, easements, costs, risk, and community input. On this project, we have limited flexibility with regard to the sewer pipeline’s location. Where possible, the team moved the new sewer location to reduce disruptions. Still, we understand construction in the area will cause inconveniences for the community. The team will work closely with you and your neighbors throughout the entire process to keep you up to date, hear your concerns, and address your questions.

View more photos on our Flickr site.


To sign up for project text alerts:

Click here or text KING REDMONDSEWER to 468-311 

Glossary of terms: King County Wastewater 101