Purity Lake Dam is an earth dam located in Carroll County, New Hampshire, built in 1750. It carries a High hazard potential classification and has a poor condition assessment.
Dam profile
NID height · 13 ft13 ft tall and 96 ft long. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
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.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | New Hampshire |
| County | Carroll |
| Nearest City | Madison |
| River/Stream | Danforth Ponds |
| Coordinates | 43.86110, -71.08880 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 13 ft |
| Dam Height | 13 ft |
| Dam Length | 96 ft |
| Year Completed | 1750 (276 years old) |
Storage & Hydraulics
| NID Storage | 182 acre-ft |
| Max Storage | 182 acre-ft |
| Normal Storage | 162 acre-ft |
| Surface Area | 27 acres |
| Drainage Area | 6 sq mi |
| Max Discharge | 240 cfs |
Ownership & Safety
| Purpose | Recreation |
| Owner | Purity Spring Resort Andnh Auddubon |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 09/26/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NH00284 |
| Federal ID | NH00284 |
| More Info | State Dam Safety Program |