Challis Cyprus Lagoon System - Secondary Wastewater Treatment in Custer County, Idaho

The Challis Cyprus Lagoon System is a municipal wastewater treatment facility located in Custer County, Idaho, United States. It serves a small population of 432 residents, typical of rural communities in the mountainous western US. The plant is situated in the Salmon River watershed, an ecologically significant basin that drains into the Snake River and ultimately the Columbia River. The facility provides secondary treatment, a standard level required by the US Clean Water Act for most municipal plants. With a designed capacity of 511.03 megaliters and an annual discharge volume of 302.83 megaliters, the plant operates well within its capacity. As a small agglomeration, it is subject to state-level NPDES permits that enforce effluent limits to protect water quality. The plant's treated effluent is discharged into the local environment, contributing to the Salmon River system. This watershed supports diverse aquatic life, including salmonid species, and is part of the larger Columbia River basin. The plant's performance is critical for maintaining downstream water quality in this sensitive mountain ecosystem.

The Challis Cyprus Lagoon System discharges into the Salmon River watershed, which flows through central Idaho before joining the Snake River and eventually the Columbia River to the Pacific Ocean. This region is characterized by mountainous terrain and cold-water fisheries, supporting species such as Chinook salmon and steelhead trout. The plant's secondary treatment helps protect these downstream ecosystems from nutrient pollution and pathogens.