City of Mercer Island Lake Line and Pump Station No. 4

Project overview

Vanir provided construction management services for the City of Mercer Island. The existing underwater lake line at the Island was prone to damage and badly deteriorated, and the existing pump stations had reached the end of their service lives. This project used two construction contracts to correct these problems and mitigate environmental impacts to Lake Washington. As the construction manager, Vanir managed the replacement of 7,000 linear feet of existing sanitary sewer lines with new gravity and force mains along the northwest shoreline of Mercer Island, development of 42 lateral connections from the underwater line to beachfront properties, construction of a new pump station, decommissioning of two existing pump stations and restoration of the shoreline and property.

Construction challenges included: a) maintaining service to multimillion- dollar homes on the existing gravity sewers and keeping existing force mains active while installing and connecting to the new system in an underwater environment, and b) managing excavation and dewatering issues for the 55-foot deep pump station on the shore of Lake Washington.

Saving the project

When initial bids exceeded the City’s budget, the City retained Vanir tofind a way to save the project. The Vanir team collaborated with the owner, engineer and contractors to refine the design, reallocate risk, reestimate the cost, repackage the scope into two contracts and rebid. New bids came in about $2 million under the new budget and contracts were awarded.



2011 CMAA Pacific Northwest Chapter – Project Achievement Award | 2010 Washington American Public Works Association Northwest Chapter – Project of the Year Award, Environment, $5M to $25M

Mercer Island, Washington
City of Mercer Island

Tetra Tech


Marine Work: Manson Construction Co.

Pump Station: Stellar J Corporation

Construction Cost
$19.7 Million
Start Date
Completion Date