Photo Credit: Ned Ahrens © King County 2013

King County West Point Treatment Plant Influent Screening Improvements

Project overview

Vanir provided construction management services for King County’s West Point Treatment Plant, located about four miles northwest of downtown Seattle on the shores of Puget Sound. It is part of the County’s regional system that treats wastewater for about 1.5 million people and covers 420 square miles in the Puget Sound region.

In 1991, to comply with the 1972 federal Clean Water Act, Metro began an expansion of the Plant to provide secondary treatment. The expansion and upgrade to secondary treatment was completed in 1996. The average capacity for wet weather flow is 133 million gallons per day (mgd) and the maximum capacity is 440 mgd during peak storms.

This project was required under Washington State Department of Ecology biosolids management regulations as outlined under Washington Administrative Code 173-308-205. The regulations require all treatment plants in Washington State to install 3/8-inch (or finer) bar screens somewhere in the treatment process to “significantly remove manufactured inerts” such as plastics, metals, ceramics and other manufactured items from the biosolids.

Vanir was responsible for managing construction of a new screenings handling building, as well as the installation of new conveyors, grinders, washer/compactors and container loading facilities in this new building. The project also required extensive work in the existing Raw Sewage Building, including demolition of the existing bar screens and associated screenings handling equipment and installation of new multi-rake bar screens, conveyors and motorized influent gates.

Seattle, Washington
King County Department of Natural Resources and Parks Wastewater Treatment Division

CDM Smith


MKB Constructors

Construction Cost
$10 Million
Start Date
Completion Date