Upper Flannagan Pond Dam
Upper Flannagan Pond Dam is a dam located in Middlesex County, Massachusetts, built in 1955. It carries a Significant hazard potential classification and has a poor condition assessment.
About Upper Flannagan Pond Dam
The primary purpose of Upper Flannagan Pond Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Town Of Ayer (local government). It impounds the Tributary Of Nonacocus Brook near Ayer.
The dam stands 9 feet tall and stretches 30 feet across, creates a reservoir covering 23 acres, has a maximum storage capacity of 110 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1955, the structure is well into its service life at over 50 years old.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. Its condition is rated poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. The most recent inspection on record was 11/05/2021.
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Location
| State | Massachusetts |
| County | Middlesex |
| Nearest City | Ayer |
| River/Stream | Tributary Of Nonacocus Brook |
| Coordinates | 42.56209, -71.57397 |
Physical Characteristics
| NID Height | 9 ft |
| Dam Length | 30 ft |
| Year Completed | 1955 (71 years old) |
Storage & Hydraulics
| NID Storage | 110 acre-ft |
| Max Storage | 110 acre-ft |
| Normal Storage | 75 acre-ft |
| Surface Area | 23 acres |
| Drainage Area | 0 sq mi |
| Max Discharge | 50 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | Town of Ayer |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Condition Assessment | Poor |
| Last Inspection | 11/05/2021 |
| Emergency Action Plan | No |
Identifiers
| NID ID | MA00810 |
| Federal ID | MA00810 |
| More Info | State Dam Safety Program |