ST MARIES S_T LAGOON Wastewater Treatment Plant, Chat'u'washa'lqs Bluff, Idaho

ST MARIES S_T LAGOON is a wastewater treatment plant located on Shepherd Road in Chat'u'washa'lqs Bluff, Benewah County, Idaho, United States. The facility serves a population of approximately 3,182 people and operates with a designed capacity of 4,542.48 volume units, discharging 681.37 volume units of treated effluent. The plant provides secondary treatment, which is the standard level required under the U.S. Clean Water Act for municipal wastewater facilities. Secondary treatment typically involves biological processes to reduce organic matter and suspended solids, meeting EPA effluent guidelines. As a plant serving a small community, it falls under the regulatory framework of the National Pollutant Discharge Elimination System (NPDES), which issues permits to ensure compliance with water quality standards. The treated wastewater is discharged into the local watershed, which ultimately drains into the Spokane River and then the Columbia River system. This region is part of the larger Columbia Basin, supporting diverse aquatic life and providing water for agricultural and recreational uses. The plant's operations help protect downstream water quality in this ecologically important river network.

The plant discharges into the local watershed that feeds into the Spokane River, a tributary of the Columbia River. The Columbia River basin supports salmon runs and other migratory fish species, making water quality management critical. The plant's secondary treatment helps reduce nutrient and pollutant loads, protecting downstream aquatic habitats and recreational waters.