Carlin Bay Wastewater System - Primary Treatment Plant in Kootenai County, Idaho

Carlin Bay Wastewater System is a small municipal treatment facility located in Kootenai County, Idaho, United States. Serving a population of 210, it provides primary treatment for wastewater from the Carlin Bay area. The plant has a designed capacity of 492.10 megaliters and discharges approximately 151.42 megaliters annually. As a primary treatment plant, it relies on physical processes such as sedimentation to remove solids. Under the U.S. Clean Water Act, smaller plants like this are typically regulated through National Pollutant Discharge Elimination System (NPDES) permits issued by the Idaho Department of Environmental Quality, which set effluent limits to protect water quality. The plant's treated effluent is discharged into the local watershed, which ultimately drains into Lake Coeur d'Alene, a large natural lake in northern Idaho. Lake Coeur d'Alene is part of the Spokane River basin and supports diverse aquatic life, including trout and salmon species. The lake is also a popular recreational area, making water quality protection important for both ecological and human uses.

The plant discharges into the Lake Coeur d'Alene watershed, which flows via the Spokane River to the Columbia River and eventually the Pacific Ocean. Lake Coeur d'Alene is a deep, oligotrophic lake that supports cold-water fish species and provides critical habitat for migratory waterfowl. The surrounding area is forested and sparsely populated, with the lake serving as a key recreational and ecological resource.