2025 AC Water Main Replacement

This project will replace approximately 9,000 feet of asbestos cement (AC) water main along portions of Mercerwood Drive, Shoreclub Drive, and 95^th, 96^th, and 97^th Avenues within the Mercerwood neighborhood. City staff are currently reviewing 90% design plans and specifications. Advertisement for contractor bids is planned for later in the spring. Construction is anticipated to begin in late summer/early fall of 2026. This is the second AC pipe replacement project supporting the City’s goal of eliminating all AC water mains from the water system by 2030.

Project Timeline
Planning/Design: Q1 of 2025 - Q3 of 2026

Construction: Q4 of 2026 – Q3 of 2027

Estimated Budget

$5,700,495

Contact

Lauren Kumle, Utility Engineer, (206) 549-1036, lauren.kumle@mercerisland.gov

Status Updates

November 5, 2026

Construction will begin the week of Nov. 9 to replace 5,700 feet of aging asbestos cement water main in the Mercerwood neighborhood. City and Mercer Island School District staff are working together to maintain safe travel routes during construction. Expect increased traffic congestion along SE 40th Street and Mercerwood Drive, especially during school drop-off and pick-up times. Drivers should allow extra travel time, use caution, and watch for workers and pedestrians. Students should continue using marked crosswalks, and school bus service will continue as usual.

The project location is just east of the City’s Water Supply Pipeline Project, currently under construction on Gallagher Hill Road: https://letstalk.mercergov.org/water-supply-line-replacement The City is coordinating the two projects to minimize traffic disruptions and other construction-related impacts, particularly once the Gallagher Hill Road detour takes effect in early December.

August 21, 2026

The 2025 Asbestos Cement (AC) Water Main Replacement project is officially out for bid! In two weeks, we will hold an on-site pre-bid meeting with interested contractors to walk the site and highlight key aspects of the project. Topics will include the proposed pressure reducing valve (PRV) vault location, eight main water connection points, driveway impacts, and traffic impacts. This project will replace approximately 5,700 LF of AC pipe with ductile iron (DI) pipe and 90 water services. Bids will be accepted until September 17, and the project will be awarded in early October.

February 2, 2026

City staff are currently reviewing 90% design plans and specifications. Advertisement for contractor bids is planned for later this summer. Construction is anticipated to begin in fall of 2026. This is the second AC pipe replacement project supporting the City’s goal of eliminating all AC water mains from the water system by 2030.

September 17, 2024

The City has contracted Consor to design the 2025 AC Main Replacement Project. City staff met with Consor staff to establish tasks and a timeline. The next step is for City staff to provide data to Consor and to conduct a site visit and evaluating the current water system and other utilities in the area.