Poquonnock Reservoir Dam
Poquonnock Reservoir Dam is an earth dam located in New London County, Connecticut, built in 1901. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Poquonnock Reservoir Dam
The primary purpose of Poquonnock Reservoir 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 Groton (local government). It impounds the Great Brook near Groton.
The dam stands 18 feet tall and stretches 290 feet across, creates a reservoir covering 139 acres, has a maximum storage capacity of 1,660 acre-feet, and collects water from a drainage area of 15 square miles. Completed in 1901, 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 satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 02/15/2023.
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 Connecticut 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 | Connecticut |
| County | New London |
| Nearest City | Groton |
| River/Stream | Great Brook |
| Coordinates | 41.35052, -72.03651 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 18 ft |
| Dam Height | 18 ft |
| Dam Length | 290 ft |
| Year Completed | 1901 (125 years old) |
Storage & Hydraulics
| NID Storage | 1,660 acre-ft |
| Max Storage | 1,660 acre-ft |
| Normal Storage | 921 acre-ft |
| Surface Area | 139 acres |
| Drainage Area | 15 sq mi |
| Max Discharge | 1,160 cfs |
Ownership & Safety
| Purpose | Water Supply |
| Owner | City of Groton |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 02/15/2023 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CT00231 |
| Federal ID | CT00231 |
| More Info | State Dam Safety Program |