Hopkinton Dam - Dike H-3 is an earth dam located in Merrimack County, New Hampshire, built in 1962. It carries a High hazard potential classification.
Dam profile
NID height · 66 ft66 ft tall and 4,400 ft long, taller than 96% of U.S. dams with a recorded height. Height is drawn to scale against a ten-story building, about 100 ft; the profile is a generic embankment section and the water level is illustrative.
About Hopkinton Dam - Dike H-3
The primary purpose of Hopkinton Dam - Dike H-3 is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by USACE - New England District (federal). It impounds the Cressey's Brook near Hopkinton.
The dam stands 66 feet tall and stretches 4,400 feet across, creates a reservoir covering 220 acres, has a maximum storage capacity of 131,000 acre-feet, and collects water from a drainage area of 382 square miles. Completed in 1962, the structure is well into its service life at over 50 years 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. An emergency action plan is in place for this dam. The most recent inspection on record was 11/02/2021.
At 66 feet, this dam is taller than 96% of all dams in the United States.
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 | Hopkinton |
| River/Stream | Cressey's Brook |
| Coordinates | 43.19600, -71.71012 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 66 ft |
| Dam Height | 66 ft |
| Dam Length | 4,400 ft |
| Year Completed | 1962 (64 years old) |
Storage & Hydraulics
| NID Storage | 131,000 acre-ft |
| Max Storage | 131,000 acre-ft |
| Normal Storage | 700 acre-ft |
| Surface Area | 220 acres |
| Drainage Area | 382 sq mi |
| Max Discharge | 58,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | USACE - New England District |
| Owner Type | Federal |
| Hazard Classification | High |
| Condition Assessment | Not assessed |
| Last Inspection | 11/02/2021 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NH01059 |
| Federal ID | NH00004S002 |
| More Info | State Dam Safety Program |