Mansfield Hollow Dam - Dike C
Mansfield Hollow Dam - Dike C is a gravity dam located in Tolland County, Connecticut, built in 1952. It carries a High hazard potential classification.
About Mansfield Hollow Dam - Dike C
The primary purpose of Mansfield Hollow Dam - Dike C 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 Nachaug River near Willimantic.
The dam stands 78 feet tall and stretches 14,050 feet across, creates a reservoir covering 450 acres, has a maximum storage capacity of 76,000 acre-feet, and collects water from a drainage area of 159 square miles. Completed in 1952, 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 06/01/2020.
At 78 feet, this dam is taller than 97% 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 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 | Tolland |
| Nearest City | Willimantic |
| River/Stream | Nachaug River |
| Coordinates | 41.76500, -72.18167 |
Physical Characteristics
| Dam Type | Gravity |
| NID Height | 78 ft |
| Dam Height | 78 ft |
| Dam Length | 14,050 ft |
| Year Completed | 1952 (74 years old) |
Storage & Hydraulics
| NID Storage | 76,000 acre-ft |
| Max Storage | 76,000 acre-ft |
| Normal Storage | 2,800 acre-ft |
| Surface Area | 450 acres |
| Drainage Area | 159 sq mi |
| Max Discharge | 106,500 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | USACE - New England District |
| Owner Type | Federal |
| Hazard Classification | High |
| Condition Assessment | Not Available |
| Last Inspection | 06/01/2020 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CT00503 |
| Federal ID | CT00503S003 |
| More Info | State Dam Safety Program |