Westport STP - Secondary Wastewater Treatment Plant in Westport, Oregon

Westport STP is a municipal wastewater treatment plant located in Westport, Oregon, a small community along the Columbia River in Clatsop County. The plant serves a population of 355 residents and operates under the regulatory framework of the U.S. Clean Water Act, which requires secondary treatment for municipal discharges to surface waters. The plant provides secondary treatment, a standard biological process that removes organic matter and suspended solids. Its designed capacity is 340.69 million gallons per year, with an actual discharge volume of 102.21 million gallons per year, indicating significant reserve capacity. As a small facility, it is subject to Oregon Department of Environmental Quality oversight and National Pollutant Discharge Elimination System (NPDES) permitting. The treated effluent is discharged into the Columbia River, which flows approximately 1,200 miles to the Pacific Ocean. The lower Columbia River estuary is a critical habitat for salmon, steelhead, and other migratory fish species. The plant's coastal location within 10 km of the Pacific Ocean means its discharge contributes to the broader estuarine ecosystem.

Westport STP discharges into the Columbia River, which drains into the Pacific Ocean via the Columbia River estuary. This estuary is one of the largest in North America and supports diverse aquatic life, including salmon runs and migratory birds. The plant's location within 10 km of the coast means its effluent enters a dynamic tidal environment where nutrient and pollutant impacts are influenced by freshwater and marine mixing.