RYDERWOOD STP - Secondary Wastewater Treatment in Ryderwood, Washington

RYDERWOOD STP is a municipal wastewater treatment facility located in Ryderwood, a small community in Cowlitz County, Washington, United States. The plant serves a population of approximately 380 residents, classifying it as a very small agglomeration under typical regulatory frameworks. The plant provides secondary treatment, which is the standard level required by the U.S. Clean Water Act for municipal wastewater facilities. With a designed capacity of 378.54 cubic meters per day and a matching discharge volume, the plant operates at full capacity. As a small facility, it is subject to 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 a local water body within the Columbia River basin, which ultimately drains to the Pacific Ocean. The plant plays a key role in protecting downstream water quality in this ecologically significant region, which supports salmon runs and diverse aquatic habitats.

RYDERWOOD STP discharges into a tributary of the Columbia River, one of the largest river systems in North America. The Columbia River flows into the Pacific Ocean, supporting critical salmon and steelhead populations. The plant's secondary treatment helps reduce nutrient and pollutant loads, protecting downstream ecosystems in the lower Columbia River estuary.