Riggins Sewage Treatment Facility | Small Community Wastewater Plant in Idaho

The Riggins Sewage Treatment Facility is a municipal wastewater treatment plant located in Riggins, Idaho, along the Salmon River corridor. Serving a population of approximately 1,319, the plant is classified as a small-scale facility under U.S. EPA regulations. It operates under the Clean Water Act, which requires secondary treatment for municipal plants discharging to surface waters. The plant provides secondary treatment, a standard biological process that removes organic matter and suspended solids. With a designed capacity of 586.74 thousand gallons per day and an average discharge volume of 242.27 thousand gallons per day, the facility operates well within its capacity. As a small community plant, it is subject to NPDES permitting through the Idaho Department of Environmental Quality, ensuring compliance with water quality standards. The treated effluent is discharged into the Salmon River, a major tributary of the Snake River, which flows into the Columbia River and ultimately reaches the Pacific Ocean. The Salmon River is known for its cold-water fisheries, including salmon and steelhead, making the plant's treatment performance critical to downstream aquatic health. The facility's secondary treatment helps protect these sensitive species from nutrient pollution and pathogens.

The plant discharges into the Salmon River, a free-flowing tributary of the Snake River, which drains into the Columbia River and the Pacific Ocean. The Salmon River supports critical habitat for anadromous fish such as Chinook salmon and steelhead trout, which are species of conservation concern. The facility's secondary treatment reduces biochemical oxygen demand and suspended solids, helping to maintain water quality in this ecologically sensitive river system.