Union Auxiliary No. 7
Union Auxiliary No. 7 is a rockfill dam located in Alpine County, California, built in 1910. It carries a Low hazard potential classification and has a satisfactory condition assessment.
About Union Auxiliary No. 7
The primary purpose of Union Auxiliary No. 7 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 California Power Agency (private). It impounds the North Fork Stanislaus River - near Dorrington.
The dam stands 7 feet tall and stretches 52 feet across, creates a reservoir covering 215 acres, has a maximum storage capacity of 3,283 acre-feet, and collects water from a drainage area of 15 square miles. Completed in 1910, 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 08/09/2022.
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Location
| State | California |
| County | Alpine |
| Nearest City | Dorrington |
| River/Stream | North Fork Stanislaus River - |
| Coordinates | 38.43480, -119.99450 |
Physical Characteristics
| Dam Type | Rockfill |
| NID Height | 7 ft |
| Dam Height | 7 ft |
| Dam Length | 52 ft |
| Year Completed | 1910 (116 years old) |
Storage & Hydraulics
| NID Storage | 3,283 acre-ft |
| Max Storage | 3,283 acre-ft |
| Normal Storage | 3,130 acre-ft |
| Surface Area | 215 acres |
| Drainage Area | 15 sq mi |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | Northern California Power Agency |
| Owner Type | Private |
| Hazard Classification | Low |
| Condition Assessment | Satisfactory |
| Last Inspection | 08/09/2022 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | CA00426 |
| Federal ID | CA00426S004 |
| More Info | State Dam Safety Program |