Alton Power Dam

About Alton Power Dam

The primary purpose of Alton Power Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Nh Fish And Game Department (state). It impounds the Merrymeeting River near Alton.

The dam stands 16 feet tall and stretches 190 feet across, creates a reservoir covering 719 acres, has a maximum storage capacity of 3,392 acre-feet, and collects water from a drainage area of 35 square miles. Completed in 1923, 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 poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. An emergency action plan is in place for this dam. The most recent inspection on record was 04/26/2022.

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

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