Sumner STP Wastewater Treatment Plant, Sumner, Washington

Sumner STP is a municipal wastewater treatment plant located in Sumner, Pierce County, Washington. The facility serves a population of approximately 26,950 residents, classifying it as a medium-sized agglomeration under U.S. regulatory frameworks. The plant's designed capacity is 1.00 million gallons per day. As a U.S. facility, it operates under the Clean Water Act's National Pollutant Discharge Elimination System (NPDES) permit program, administered by the Washington State Department of Ecology. Treatment requirements are determined based on the receiving water body's water quality standards. The plant discharges treated effluent into the Puyallup River watershed, which flows into Commencement Bay and ultimately Puget Sound. This water body supports diverse aquatic life, including salmon runs, and is an important ecological corridor in the Pacific Northwest.

Sumner STP discharges into the Puyallup River, which flows into Commencement Bay in Puget Sound. The Puyallup River watershed supports critical salmon and steelhead habitats, and the plant's discharge must meet water quality standards to protect these species. Puget Sound is a large estuarine system that provides essential ecosystem services, including nutrient cycling and habitat for marine life.