Rapidan is a buttress dam located in Blue Earth County, Minnesota, built in 1910. It carries a Significant hazard potential classification and has a unsatisfactory condition assessment.
Dam profile
NID height · 73 ft73 ft tall and 414 ft long, taller than 96% of U.S. dams with a recorded height. Height is drawn to scale against a ten-story building, about 100 ft; the profile is a generic concrete gravity section and the water level is illustrative.
About Rapidan
The primary purpose of Rapidan is hydroelectric. The dam generates hydroelectric power by channeling water through turbines, converting the energy of flowing water into electricity. It impounds the Blue Earth near Mankato.
The dam stands 73 feet tall and stretches 414 feet across, creates a reservoir covering 415 acres, has a maximum storage capacity of 8,320 acre-feet, and collects water from a drainage area of 2,430 square miles. Completed in 1910, the structure is over a century 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 unsatisfactory, indicating serious safety deficiencies exist that require immediate attention or remedial action. An emergency action plan is in place for this dam. The most recent inspection on record was 05/23/2024.
At 73 feet, this dam is taller than 96% of all dams in the United States.
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Location
| State | Minnesota |
| County | Blue Earth |
| Nearest City | Mankato |
| River/Stream | Blue Earth |
| Coordinates | 44.09300, -94.10800 |
Physical Characteristics
| Dam Type | Buttress |
| NID Height | 73 ft |
| Dam Height | 73 ft |
| Dam Length | 414 ft |
| Year Completed | 1910 (116 years old) |
Storage & Hydraulics
| NID Storage | 8,320 acre-ft |
| Max Storage | 8,320 acre-ft |
| Normal Storage | 8,320 acre-ft |
| Surface Area | 415 acres |
| Drainage Area | 2,430 sq mi |
| Max Discharge | 51,700 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner Type | Not Listed |
| Hazard Classification | Significant |
| Condition Assessment | Unsatisfactory |
| Last Inspection | 05/23/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | MN00512 |
| Federal ID | MN00512 |
| More Info | State Dam Safety Program |