Hog Flat

About Hog Flat

The primary purpose of Hog Flat is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by Lassen Irrigation Company (private). It impounds the Tr Susan River.

The dam stands 15 feet tall and stretches 1,760 feet across, creates a reservoir covering 1,000 acres, has a maximum storage capacity of 8,000 acre-feet, and collects water from a drainage area of 8 square miles. Completed in 1891, 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 satisfactory, indicating no existing or potential dam safety deficiencies are recognized. Notably, no emergency action plan is currently on file for this high-hazard dam. The most recent inspection on record was 08/27/2025.

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

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