Mountain Lake Dam

About Mountain Lake Dam

The primary purpose of Mountain Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Wa Parks (state). It impounds the Cascade Creek near Olga.

The dam stands 17 feet tall and stretches 172 feet across, creates a reservoir covering 180 acres, has a maximum storage capacity of 3,010 acre-feet, and collects water from a drainage area of 2 square miles. Completed in 1905, 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. An emergency action plan is in place for this dam. The most recent inspection on record was 07/23/2024.

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

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