The West Point Treatment Plant is located about four miles northwest of downtown Seattle on the shores of Puget Sound. It is part of King 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. Expansion and upgrading to secondary treatment was completed in 1996. The average capacity for wet weather flow is 133 mgd and the maximum capacity if 440 mgd during peak storms.
This project was required under recent Washington State Department of Ecology biosolids management regulations as outlined under Washington Administrative Code (WAC) 173-308-205. The regulations require all treatment plants in Washington State to install 3/8″ (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, and 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.