Sylvan Lake Dam

About Sylvan Lake Dam

The primary purpose of Sylvan Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Gf&p (state). It impounds the Tr-spring Creek near Hill City.

The dam stands 37 feet tall and stretches 57 feet across, creates a reservoir covering 17 acres, has a maximum storage capacity of 240 acre-feet, and collects water from a drainage area of 1 square miles. Completed in 1906, the structure is over a century 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. The most recent inspection on record was 10/24/2023.

At 37 feet, this dam is taller than 84% of dams nationwide.

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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