CHEHALIS STP - Chehalis, Washington Wastewater Treatment Plant

CHEHALIS STP is a municipal wastewater treatment plant located at 468 Northwest Louisiana Avenue in Chehalis, Washington. Serving a population of about 9,591, the plant is part of the city's infrastructure managed under state and federal regulations. As a U.S. facility, the plant operates under the Clean Water Act's National Pollutant Discharge Elimination System (NPDES) permit program, which sets effluent limits to protect water quality. The plant has a designed capacity of 1.00 million gallons per day. The treated effluent is discharged into a local water body that ultimately drains into the Chehalis River basin, which flows to Grays Harbor and the Pacific Ocean. The Chehalis River supports diverse aquatic life, including salmon runs, and the plant's operations are critical to maintaining downstream water quality in this ecologically sensitive watershed.

The plant discharges into the Chehalis River basin, which flows through southwestern Washington to Grays Harbor, an estuary that empties into the Pacific Ocean. The Chehalis River supports important salmon and steelhead populations, and the surrounding watershed provides habitat for diverse wildlife. Proper treatment is essential to protect these aquatic ecosystems from nutrient pollution and other contaminants.