Thompson Mtis

About Thompson Mtis

The primary purpose of Thompson Mtis is tailings. Tailings dams contain waste material from mining operations — typically a slurry of finely ground rock left over after valuable minerals have been extracted. These structures require ongoing monitoring because tailings can contain heavy metals and other contaminants. The dam is private-owned. It impounds the Bruno Creek Squaw Creek near Clayton.

The dam stands 789 feet tall and stretches 3,960 feet across, creates a reservoir covering 320 acres, has a storage capacity of 895,000 acre-feet, and collects water from a drainage area of 2 square miles. Completed in 1982, the structure is 44 years old.

This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. 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 06/05/2019.

At 789 feet, this dam is taller than 100% of all dams in the United States.

Living Downstream

If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Idaho dam safety program can provide more specific information about emergency planning for this structure.

Search for dams near your address to see all dams in your area with hazard classifications and safety data.