Panther Lake Detention Dam

About Panther Lake Detention Dam

The primary purpose of Panther Lake Detention Dam 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 Federal Way Nat' Lit League (private). It impounds the Offstream near Federal Way.

The dam stands 12 feet tall, has a maximum storage capacity of 339 acre-feet, and collects water from a drainage area of 2 square miles. Completed in 1994, the structure is 32 years 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 08/25/2016. That was 9 years ago, which is on the longer end for a high-hazard structure.

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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