Seneca STP - Secondary Wastewater Treatment Plant in Seneca, Oregon

Seneca STP is a municipal wastewater treatment facility located in Seneca, a small town in Grant County, Oregon. The plant serves a population of approximately 215 residents, reflecting the rural character of the area. As a secondary treatment plant, it provides biological treatment to remove organic matter and suspended solids from wastewater. The plant operates under the regulatory framework of the U.S. Clean Water Act, which requires secondary treatment for municipal wastewater discharges. The National Pollutant Discharge Elimination System (NPDES) permits, issued by the Oregon Department of Environmental Quality, govern the plant's discharge limits and monitoring requirements. The plant's designed capacity of 685.16 volume units matches its current discharge volume, indicating full utilization. The treated effluent from Seneca STP is discharged into a receiving water body within the John Day River basin, which ultimately flows into the Columbia River. The John Day River is a major tributary of the Columbia and supports diverse aquatic life, including salmon and steelhead. The plant's secondary treatment helps protect water quality in this ecologically important watershed.

Seneca STP discharges into a tributary of the John Day River, which flows into the Columbia River and eventually reaches the Pacific Ocean. The John Day River basin is known for its pristine habitats and supports populations of threatened and endangered fish species, such as Chinook salmon and steelhead trout. The plant's secondary treatment reduces nutrient and organic loads, helping to maintain the ecological health of the downstream environment.