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Lake Hills and NW Lake Sammamish sewer upgrade

The Lake Hills and NW Lake Sammamish Sewer Upgrade Project will upgrade 4.5 miles of sewer pipes serving the growing Redmond and Bellevue areas.

Project update

Fall 2026

Surveying starts in Redmond this fall. Temporary lane closures will begin as early as September 28

Crews will check wetland and soil conditions. They will also confirm the location of existing or new utilities. Surveying will take place throughout the full project area.

Learn more about this work.

Construction planned to begin in 2029

We will continue to gather information, work with nearby property owners, and finalize our project designs until we start construction.

Interested in a project briefing for your community group?

We are happy to meet with you or come to your next community event. We can share the latest project information and answer questions you might have as we get closer to construction. Please contact Annie Plumley at 206-263-3203 or LakeHillsSewerUpgrade@kingcounty.gov for more information.

Past project updates

Project description

Upgrading a vital link in our water system!

King County will replace 4.5 miles of sewer pipes in Redmond and Bellevue. These pipes are more than 50 years old. The new pipes will support the growing community. This regional sewer upgrade will keep service safe and reliable for many years in the future.

If you live or work on the northwest side of Lake Sammamish, these sewer pipes serve you every day. The dirty water you make goes into these pipes. Then it travels to Brightwater Treatment Plant near Woodinville!

 

 

Project location

Map of where King County will build the new sewer pipe for the Lake Hills and Northwest Lake Sammamish Sewer Upgrade project, described in detail below.

The new sewer pipes will be in the same place or parallel to where the pipes are today. The sewer pipe upgrade starts at Northeast 85th Street near Redmond City Hall. It runs south under the Sammamish River Trail. Then it follows West Lake Sammamish Parkway between Marymoor Park and Idylwood. The project ends in Redmond’s Idylwood neighborhood.

Existing pipe location