Cottonwood STP Wastewater Treatment Plant, Idaho County, Idaho

Cottonwood STP is a municipal wastewater treatment facility located in Idaho County, Idaho, serving a small community of around 900 residents. The plant provides secondary treatment, a standard level for small agglomerations in the United States, ensuring that effluent meets federal and state water quality standards before discharge. As a secondary treatment plant, Cottonwood STP utilizes biological processes to reduce organic matter and suspended solids. The plant has a designed capacity of 1,040.99 and an average daily flow of 984.21, indicating it operates near its capacity. Under the U.S. Clean Water Act, such facilities must comply with National Pollutant Discharge Elimination System (NPDES) permits, which set effluent limits and monitoring requirements. The plant discharges treated wastewater into a local waterway within the Columbia River Basin, which ultimately drains to the Pacific Ocean. Its inland location reduces direct marine impact, but the effluent quality is important for protecting downstream aquatic ecosystems and maintaining water quality in the region's rivers and streams.

Cottonwood STP discharges into a tributary of the Clearwater River, part of the Columbia River Basin that flows to the Pacific Ocean. The local watershed supports diverse aquatic life, including salmon and steelhead, which are sensitive to nutrient loading and pollutants. Proper treatment is essential to protect these species and maintain the ecological health of the river system.