King County Vashon WWTP - Secondary Treatment Plant on Vashon Island, Washington

King County Vashon WWTP is a municipal wastewater treatment facility located on Vashon Island in King County, Washington, United States. The plant serves a small population of 539 residents and operates as part of the county's wastewater infrastructure. The plant provides secondary treatment, a standard level required by the U.S. Clean Water Act for municipal wastewater. With a designed capacity of approximately 1,968 cubic meters per day and a current discharge volume of about 909 cubic meters per day, the facility operates well within its capacity. Treated effluent is discharged into the surrounding environment near Puget Sound, a major estuary of the Pacific Ocean. The plant's coastal location means its discharge can affect local marine water quality and the diverse aquatic life that depends on this sensitive ecosystem.

The plant discharges into the Puget Sound basin, a large estuarine system connected to the Pacific Ocean via the Strait of Juan de Fuca. Puget Sound supports critical habitats for salmon, orcas, and other marine species. The plant's coastal proximity requires careful management to protect water quality and the ecological health of the sound.