Mill Creek 9a
Mill Creek 9a is an earth dam located in Richland County, Wisconsin, built in 1965. It carries a Significant hazard potential classification and has a fair condition assessment.
About Mill Creek 9a
The primary purpose of Mill Creek 9a 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 Richland County (local government). It impounds the Mill Creek Offstream near Boaz.
The dam stands 29 feet tall and stretches 600 feet across, has a maximum storage capacity of 220 acre-feet, and collects water from a drainage area of 4 square miles. Completed in 1965, 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 fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 05/20/2021.
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Location
| State | Wisconsin |
| County | Richland |
| Nearest City | Boaz |
| River/Stream | Mill Creek Offstream |
| Coordinates | 43.44162, -90.57774 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 29 ft |
| Dam Height | 29 ft |
| Dam Length | 600 ft |
| Year Completed | 1965 (61 years old) |
Storage & Hydraulics
| NID Storage | 220 acre-ft |
| Max Storage | 220 acre-ft |
| Drainage Area | 4 sq mi |
| Max Discharge | 572 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | Richland County |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Condition Assessment | Fair |
| Last Inspection | 05/20/2021 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WI00389 |
| Federal ID | WI00389 |
| More Info | State Dam Safety Program |