204th Street Stormwater Detention Basin

About 204th Street Stormwater Detention Basin

The primary purpose of 204th Street Stormwater Detention Basin is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by Seatac Public Works (private). It impounds the Patterson Creek - Of near Des Moines.

The dam stands 9 feet tall and stretches 1,100 feet across, creates a reservoir covering 2 acres, has a maximum storage capacity of 17 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 2001, the structure is relatively new.

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 06/17/2019.

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