Mount Vernon STP - Secondary Wastewater Treatment Plant in Mount Vernon, Oregon

Mount Vernon STP is a municipal wastewater treatment facility located in Mount Vernon, Oregon, a small community in Grant County. The plant serves a population of approximately 695 residents, providing essential sanitation services for the area. The plant operates with secondary treatment, which is the standard level required under the U.S. Clean Water Act for municipal wastewater. With a designed capacity of 378.54 megaliters per year and a current discharge volume of 140.06 megaliters per year, the facility has ample capacity to handle current flows. As a U.S. facility, it operates under an EPA National Pollutant Discharge Elimination System (NPDES) permit, which sets effluent limits to protect water quality. The treated wastewater from Mount Vernon STP is discharged into a local water body that eventually drains into the John Day River basin, a tributary of the Columbia River. This watershed supports diverse aquatic life and is important for regional ecology. The plant's secondary treatment helps reduce pollutants before discharge, contributing to the health of downstream ecosystems.

The plant discharges into a local watercourse that flows into the John Day River, a major tributary of the Columbia River. The John Day River basin is known for its diverse aquatic habitats, including salmon and steelhead runs. The Columbia River downstream supports extensive fisheries and is a vital ecological and economic resource for the Pacific Northwest. The plant's secondary treatment helps protect these downstream environments from nutrient and pathogen pollution.