Diamond Lake STP - Secondary Wastewater Treatment in Pend Oreille County, Washington

Diamond Lake STP is a municipal wastewater treatment facility located in Pend Oreille County, Washington, United States. The plant serves a small community of approximately 1,698 residents, providing secondary treatment to manage local wastewater. Its location in the inland Pacific Northwest places it within a region characterized by forested terrain and numerous lakes and rivers. The plant operates under the U.S. Clean Water Act, which requires NPDES permits for all wastewater discharges. For a facility of this size, secondary treatment is the standard requirement, ensuring that effluent meets federal water quality standards before release. The plant has a designed capacity of 707.87 million gallons per year and currently discharges 276.34 million gallons annually, indicating it operates well below its capacity. The treated effluent from Diamond Lake STP is discharged into a local water body that ultimately drains into the Pend Oreille River, a major tributary of the Columbia River. The Columbia River system supports diverse aquatic life, including salmon and steelhead, and is ecologically significant for the region. The plant's discharge contributes to the overall water quality management of this important watershed.

The plant discharges into a local water body that flows into the Pend Oreille River, which joins the Columbia River before reaching the Pacific Ocean. The Columbia River basin supports critical habitats for anadromous fish species and is a vital ecological corridor in the Pacific Northwest. The plant's secondary treatment helps protect downstream water quality in this sensitive watershed.