Stony Brook Reservoir Dam
Stony Brook Reservoir Dam is an earth dam located in Middlesex County, Massachusetts, built in 1887. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Stony Brook Reservoir Dam
The primary purpose of Stony Brook 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 Cambridge (local government). It impounds the Stony Brook near Waltham.
The dam stands 32 feet tall and stretches 820 feet across, creates a reservoir covering 72 acres, has a maximum storage capacity of 1,810 acre-feet, and collects water from a drainage area of 23 square miles. Completed in 1887, 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 11/02/2022.
At 32 feet, this dam is taller than 76% of dams nationwide.
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 | Middlesex |
| Nearest City | Waltham |
| River/Stream | Stony Brook |
| Coordinates | 42.35530, -71.26484 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 32 ft |
| Dam Length | 820 ft |
| Year Completed | 1887 (139 years old) |
Storage & Hydraulics
| NID Storage | 1,810 acre-ft |
| Max Storage | 1,810 acre-ft |
| Normal Storage | 1,312 acre-ft |
| Surface Area | 72 acres |
| Drainage Area | 23 sq mi |
| Max Discharge | 2,050 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | City of Cambridge |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 11/02/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | MA00293 |
| Federal ID | MA00293 |
| More Info | State Dam Safety Program |