Klahanie Stormwater Detention Dam No 1

About Klahanie Stormwater Detention Dam No 1

The primary purpose of Klahanie Stormwater Detention Dam No 1 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 Sammamish City Public Works (local government). It impounds the Tr-laughing Jacobs Lake Outlet near Issaquah.

The dam stands 9 feet tall and stretches 400 feet across, creates a reservoir covering 7 acres, has a maximum storage capacity of 16 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1984, the structure is 42 years old.

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 08/26/2020.

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