Horn School Rest Area Sewage Lagoon

About Horn School Rest Area Sewage Lagoon

Horn School Rest Area Sewage Lagoon is a dam in Whitman, Washington. The dam is owned by Wa Dot (state). It impounds the Offstream.

The dam stands 19 feet tall and stretches 1,200 feet across, creates a reservoir covering 2 acres, and has a maximum storage capacity of 22 acre-feet. Completed in 1996, the structure is 30 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 satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 09/02/2021.

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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