LEWIS CO STP 2 - Secondary Wastewater Treatment Plant in Lewis County, Washington

LEWIS CO STP 2 is a municipal wastewater treatment facility located in Lewis County, Washington, United States. The plant serves a small population of 311 residents, reflecting its role in a rural community. As a secondary treatment plant, it provides biological treatment to reduce organic matter and suspended solids before discharge. The plant has a designed capacity of 302.83 cubic meters per day and operates at full capacity based on reported discharge volume. Under the U.S. Clean Water Act, facilities of this scale are typically regulated through National Pollutant Discharge Elimination System (NPDES) permits issued by the Washington State Department of Ecology, ensuring compliance with water quality standards. The treated effluent is discharged into local waterways that ultimately drain into the Columbia River basin and then to the Pacific Ocean. The plant's operations help protect downstream aquatic ecosystems, including salmon habitats that are ecologically and economically significant in the Pacific Northwest.

The plant discharges into tributaries of the Cowlitz River, a major tributary of the Columbia River. The Columbia River basin supports diverse aquatic life, including several salmon and steelhead species that are vital to regional ecology and tribal fisheries. The secondary treatment process reduces nutrient and organic pollutant loads, helping maintain water quality in these sensitive freshwater systems before they reach the Pacific Ocean.