King County's Regional wastewater conveyance and treatment system
King County protects water quality and public health in the central Puget Sound region by providing high quality and effective treatment to wastewater collected from our local sewer agencies. The county's Wastewater Treatment Division (WTD) serves about 1.5 million people within a 420-square-mile service area, which includes most urban areas of King County and parts of south Snohomish County and northeast Pierce County.
Construction on the Brightwater Treatment Plant, the system's third regional treatment plant, began in 2006. Treatment plant operations began in September 2011; conveyance system and outfall began full operations in fall 2012. Final restoration work at construction sites will continue through late 2013.