Thornapple
Thornapple is a gravity dam located in Rusk County, Wisconsin, built in 1909. It carries a Low hazard potential classification and has a satisfactory condition assessment.
About Thornapple
The primary purpose of Thornapple is hydroelectric. The dam generates hydroelectric power by channeling water through turbines, converting the energy of flowing water into electricity. The dam is owned by Northern States Power Co (public utility). It impounds the Flambeau near Holcombe.
The dam stands 14 feet tall and stretches 530 feet across, creates a reservoir covering 295 acres, has a maximum storage capacity of 2,400 acre-feet, and collects water from a drainage area of 1,850 square miles. Completed in 1909, the structure is over a century old.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected 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 06/07/2022.
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Location
| State | Wisconsin |
| County | Rusk |
| Nearest City | Holcombe |
| River/Stream | Flambeau |
| Coordinates | 45.41070, -91.21670 |
Physical Characteristics
| Dam Type | Gravity |
| NID Height | 14 ft |
| Dam Height | 14 ft |
| Dam Length | 530 ft |
| Year Completed | 1909 (117 years old) |
Storage & Hydraulics
| NID Storage | 2,400 acre-ft |
| Max Storage | 2,400 acre-ft |
| Normal Storage | 1,000 acre-ft |
| Surface Area | 295 acres |
| Drainage Area | 1,850 sq mi |
| Max Discharge | 19,000 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | Northern States Power Co |
| Owner Type | Public Utility |
| Hazard Classification | Low |
| Condition Assessment | Satisfactory |
| Last Inspection | 06/07/2022 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | WI00792 |
| Federal ID | WI00792 |
| More Info | State Dam Safety Program |