Purity Lake Dam

About Purity Lake Dam

The primary purpose of Purity Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Purity Spring Resort Andnh Auddubon (private). It impounds the Danforth Ponds near Madison.

The dam stands 13 feet tall and stretches 96 feet across, creates a reservoir covering 27 acres, has a maximum storage capacity of 182 acre-feet, and collects water from a drainage area of 6 square miles. Completed in 1750, the structure is one of the older dams in the region, with over a century and a half of service.

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 09/26/2022.

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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