Ambrose

About Ambrose

The primary purpose of Ambrose is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Bia (federal). It impounds the West Fork Elm Creek near Stephan.

The dam stands 21 feet tall and stretches 800 feet across, creates a reservoir covering 40 acres, has a maximum storage capacity of 670 acre-feet, and collects water from a drainage area of 21 square miles. Completed in 1935, the structure is well-established, with more than 75 years of service.

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 poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. An emergency action plan is in place for this dam. The most recent inspection on record was 08/04/2020.

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 South Dakota dam safety program can provide more specific information about emergency planning for this structure.

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