Granville Reservoir Dam
Granville Reservoir Dam is an earth dam located in Hampden County, Massachusetts, built in 1930. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Granville Reservoir Dam
The primary purpose of Granville 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 Westfield (local government). It impounds the Hollister Brook & Tillotson Brook near Granville.
The dam stands 85 feet tall and stretches 850 feet across, creates a reservoir covering 76 acres, has a maximum storage capacity of 2,400 acre-feet, and collects water from a drainage area of 5 square miles. Completed in 1930, the structure is well-established, with more than 75 years 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 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 11/03/2022.
At 85 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 Massachusetts 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 | Massachusetts |
| County | Hampden |
| Nearest City | Granville |
| River/Stream | Hollister Brook & Tillotson Brook |
| Coordinates | 42.08764, -72.84775 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 85 ft |
| Dam Length | 850 ft |
| Year Completed | 1930 (96 years old) |
Storage & Hydraulics
| NID Storage | 2,400 acre-ft |
| Max Storage | 2,400 acre-ft |
| Normal Storage | 1,600 acre-ft |
| Surface Area | 76 acres |
| Drainage Area | 5 sq mi |
| Max Discharge | 6,570 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | City of Westfield |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 11/03/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | MA00707 |
| Federal ID | MA00707 |
| More Info | State Dam Safety Program |