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Project description 

King County is replacing sewer pipes that serve areas in North Mercer Island, the southwest portion of Bellevue near Enatai Beach Park, and the Town of Beaux Arts Village. This pipeline carries wastewater from the North Mercer Island Pump Station to the Sweyolocken Pump Station in Bellevue. Once installed, the new pipes will provide sewer service for 50 years or more. To learn more about the project overall, including what we are building, construction information, and what to expect, view our StoryMap.

To meet community needs, we broke the project up into 8 project areas, shown on the map. We provide updates about specific areas depending on where work is taking place.


General project updates

April 17, 2024

Project-wide Updates: Crews with unique expertise in underwater construction are placing pipe under the East Channel of Lake Washington. Read the news release and watch the video about this construction activity.

Construction activity in Mercer Island* 

Area 1. North Mercer Pump Station: Work continues at the North Mercer Pump Station. For more details on what to expect over the next few months, check out our recent notification

Area 2. North-central Mercer residential streets: Maintenace hole work was completed at the Pump Station. Check out past Area 2 updates here.

Area 3. North Mercer Way: Single-lane traffic along North Mercer Way as early as April 22 for approximately three weeks. Check our more details here.

Area 4. I-90 Trail: The I-90 trail is closed for pipe installation between Southeast 26th Street and Shorewood Drive and between Southeast 35th Street and Southeast 35th Place. For more information please review our recent Area 4 updates.

Click here for the trail detour map between S.E. 26th St and Shorewood Dr.

Click here for the trail detour map between S.E. 35th St and S.E. 35th Pl.

Area 5. 90th Pl S.E.: Guardrail installation at 90th Pl SE was completed. Check out past Area 5 updates here.

Area 6. NE Mercer Island: As construction activity near East Mercer Way and S.E. 35th Pl. increases, I-90 trail users should continue following our trail detour route off I-90 bridge trail. Drivers, please drive slowly and watch for cyclists on the roadway.

Crews continue installing pipe on S.E. 35th Pl. Starting as early as April 1, S.E. 35th Pl. will be closed between El Dorado Drive and East Mercer Way for approximately one month. Check out our recent notification for more information.

Crews will be moving into Fruitland Landing as early as Wednesday, April 17 to begin construction activities. Initial set-up of the temporary bypass pipe and driveway access ramps is expected to occur April 18-19.  Check out our recent notification for more information.  

As early as April 10, City of Mercer Island will reduce water pressure across several homes on El Dorado Beach Drive, Briarwood Lane, and S.E. 35th Pl. Check out our recent notification for more information.

As early as April 12 and 13, there will be single lane alternating traffic on Frontage Road. Access to the Mercer Island Boat Launch will be maintained. Check out our recent notification for more information

Luther Burbank Park: South Parking Lot currently closed due to construction equipment and material storage. For more details, see the latest update.

Construction activity in Bellevue*

Area 7. Enatai Beach Park/Lake Washington’s East Channel: For more details, check out our recent notification.

Expect single lane traffic near Enatai Beach Park as early as April 10. Crews will begin installing electrical conduits. For more details, check out our recent notification.

Area 8. Sweyolocken/Mercer Slough: Work continues near the Sweyolocken Pump Station and the Mercer Slough Boat Launch. The Mercer Slough connector trail is expected to reopen Spring 2024 with a temporary closure as early as June for repaving. Here is the current Mercer Slough trail detour map. Click here for past Area 8 updates

Construction status

Click for larger view.

This map is updated as construction progresses across north Mercer Island and southwest Bellevue. It shows areas of planned construction, active construction, and post-construction restoration.

If you need this map in another format, please leave a voicemail on the project hotline at 425-305-3578 or call TTY Relay 7-1-1. Reasonable accommodations are available to you for free.

Revised April 1, 2024

Previous general project updates

Project location