Penacook Lake Dam
Penacook Lake Dam is an earth dam located in Merrimack County, New Hampshire, built in 1873. It carries a High hazard potential classification and has a poor condition assessment.
About Penacook Lake Dam
The primary purpose of Penacook Lake Dam 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 City Of Concord (local government). It impounds the Rattlesnake Brook near Concord.
The dam stands 9 feet tall and stretches 265 feet across, creates a reservoir covering 360 acres, has a maximum storage capacity of 2,210 acre-feet, and collects water from a drainage area of 3 square miles. Completed in 1873, 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 10/25/2022.
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 | Merrimack |
| Nearest City | Concord |
| River/Stream | Rattlesnake Brook |
| Coordinates | 43.24259, -71.57653 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 9 ft |
| Dam Height | 9 ft |
| Dam Length | 265 ft |
| Year Completed | 1873 (153 years old) |
Storage & Hydraulics
| NID Storage | 2,210 acre-ft |
| Max Storage | 2,210 acre-ft |
| Normal Storage | 1,515 acre-ft |
| Surface Area | 360 acres |
| Drainage Area | 3 sq mi |
| Max Discharge | 600 cfs |
Ownership & Safety
| Purpose | Water Supply |
| Owner | CITY OF CONCORD |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 10/25/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NH00360 |
| Federal ID | NH00360 |
| More Info | State Dam Safety Program |