Loon Lake Auxiliary is a rockfill dam located in El Dorado County, California, built in 1963. It carries a Significant hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 102 ft102 ft tall and 910 ft long, taller than 98% 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 rockfill embankment section and the water level is illustrative.
About Loon Lake Auxiliary
The primary purpose of Loon Lake Auxiliary 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 Sacramento Municipal Utility District (public utility). It impounds the Gerle Creek near Folsom.
The dam stands 102 feet tall and stretches 910 feet across, creates a reservoir covering 1,450 acres, has a maximum storage capacity of 69,309 acre-feet, and collects water from a drainage area of 7 square miles. Completed in 1963, 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 satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 08/28/2023.
At 102 feet, this dam is taller than 98% of all dams in the United States.
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Location
| State | California |
| County | El Dorado |
| Nearest City | Folsom |
| River/Stream | Gerle Creek |
| Coordinates | 38.98820, -120.33210 |
Physical Characteristics
| Dam Type | Rockfill |
| NID Height | 102 ft |
| Dam Height | 90 ft |
| Dam Length | 910 ft |
| Year Completed | 1963 (63 years old) |
Storage & Hydraulics
| NID Storage | 69,309 acre-ft |
| Max Storage | 69,309 acre-ft |
| Normal Storage | 51,000 acre-ft |
| Surface Area | 1,450 acres |
| Drainage Area | 7 sq mi |
| Max Discharge | 15,300 cfs |
| Spillway Type | None |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | Sacramento Municipal Utility District |
| Owner Type | Public Utility |
| Hazard Classification | Significant |
| Condition Assessment | Satisfactory |
| Last Inspection | 08/28/2023 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00820 |
| Federal ID | CA00820S001 |
| More Info | State Dam Safety Program |