Grupes Reservoir Dam
Grupes Reservoir Dam is a concrete dam located in Fairfield County, Connecticut, built in 1871. It carries a High hazard potential classification and has a poor condition assessment.
About Grupes Reservoir Dam
The primary purpose of Grupes 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 Norwalk (local government). It impounds the Silvermine River near Pine Hill.
The dam stands 24 feet tall and stretches 235 feet across, creates a reservoir covering 23 acres, has a maximum storage capacity of 311 acre-feet, and collects water from a drainage area of 10 square miles. Completed in 1871, 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 05/10/2021.
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 | Fairfield |
| Nearest City | Pine Hill |
| River/Stream | Silvermine River |
| Coordinates | 41.18968, -73.48875 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 24 ft |
| Dam Height | 24 ft |
| Dam Length | 235 ft |
| Year Completed | 1871 (155 years old) |
Storage & Hydraulics
| NID Storage | 311 acre-ft |
| Max Storage | 311 acre-ft |
| Normal Storage | 171 acre-ft |
| Surface Area | 23 acres |
| Drainage Area | 10 sq mi |
| Max Discharge | 2,900 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | City of Norwalk |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 05/10/2021 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CT00057 |
| Federal ID | CT00057 |
| More Info | State Dam Safety Program |