Mosquito Flat

About Mosquito Flat

Mosquito Flat is a dam in Custer, Idaho. The dam is private-owned. It impounds the Challis Creek Salmon River near Challis.

The dam stands 58 feet tall and stretches 450 feet across, creates a reservoir covering 46 acres, has a storage capacity of 793 acre-feet, and collects water from a drainage area of 16 square miles. Completed in 1950, the structure is well-established, with more than 75 years of service.

This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. Its condition is rated fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 08/31/2017.

At 58 feet, this dam is taller than 95% of all dams in the United States.

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