Grand Coulee STP - Secondary Wastewater Treatment in Grand Coulee, Washington

Grand Coulee STP is a municipal wastewater treatment facility located in Grand Coulee, Washington, along the Coulee Corridor in Grant County. The plant serves a population of approximately 1,884 residents, providing secondary treatment to manage local wastewater. Its designed capacity is 1,135.62 thousand cubic meters per year, with an annual discharge volume of 783.58 thousand cubic meters. As a secondary treatment plant, Grand Coulee STP meets the standard requirements under the US Clean Water Act, which mandates secondary treatment for municipal wastewater to protect water quality. The plant operates under the National Pollutant Discharge Elimination System (NPDES) permit program, administered by the Washington State Department of Ecology, ensuring compliance with effluent limits. The treated effluent is discharged into the local watershed, which ultimately drains into the Columbia River basin. The Columbia River is a major waterway in the Pacific Northwest, supporting diverse aquatic life and providing water for irrigation, recreation, and hydropower. The plant's operations help maintain water quality in this ecologically significant region.

The plant discharges into the Columbia River basin, a vast watershed that flows through Washington and Oregon before reaching the Pacific Ocean. The Columbia River supports critical salmon runs and other native fish species, making water quality management essential for ecosystem health. The region's semi-arid climate and reliance on irrigation further underscore the importance of maintaining clean water in the receiving waters.