Three Mile Reservoir Dam is an earth dam located in Union County, Iowa, built in 1995. It carries a Significant hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 63 ft63 ft tall and 1,850 ft long, taller than 95% 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 embankment section and the water level is illustrative.
About Three Mile Reservoir Dam
The primary purpose of Three Mile Reservoir Dam 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 Iowa Department of Natural Resources (state). It impounds the Three Mile Creek near Westerville.
The dam stands 63 feet tall and stretches 1,850 feet across, creates a reservoir covering 880 acres, has a maximum storage capacity of 29,950 acre-feet, and collects water from a drainage area of 36 square miles. Completed in 1995, the structure is 31 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 satisfactory, indicating no existing or potential dam safety deficiencies are recognized. The most recent inspection on record was 06/10/2020.
At 63 feet, this dam is taller than 95% of all dams in the United States.
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Location
| State | Iowa |
| County | Union |
| Nearest City | Westerville |
| River/Stream | Three Mile Creek |
| Coordinates | 41.07240, -94.21190 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 63 ft |
| Dam Height | 63 ft |
| Dam Length | 1,850 ft |
| Year Completed | 1995 (31 years old) |
Storage & Hydraulics
| NID Storage | 29,950 acre-ft |
| Max Storage | 29,950 acre-ft |
| Normal Storage | 14,091 acre-ft |
| Surface Area | 880 acres |
| Drainage Area | 36 sq mi |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | Iowa Department of Natural Resources |
| Owner Type | State |
| Hazard Classification | Significant |
| Condition Assessment | Satisfactory |
| Last Inspection | 06/10/2020 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | IA02944 |
| Federal ID | IA02944 |
| More Info | State Dam Safety Program |