Loon Lake Auxiliary Reservoir Report

Last Updated: December 5, 2025

Loon Lake Auxiliary, located in El Dorado County, California, is a rockfill dam primarily used for hydroelectric power generation and recreational purposes.


°F

°F

mph

Wind

%

Humidity

Summary

Built in 1963 by Bechtel, this dam stands at a height of 90 feet and has a structural height of 102 feet. It has a storage capacity of 69,309 acre-feet, with a normal storage level of 51,000 acre-feet, covering a surface area of 1,450 acres.

Managed by the Federal Energy Regulatory Commission, the dam is inspected annually and is deemed to have a significant hazard potential. The surrounding area is at high risk, according to a risk assessment, with emergency action plans in place. While the dam has not undergone a recent condition assessment, it is regulated and permitted by the California Department of Water Resources, ensuring its safety and compliance with state standards. Overall, Loon Lake Auxiliary serves as a vital resource for water supply, electricity generation, and recreational activities in the region.

Year Completed

1963

Dam Length

910

Dam Height

90

River Or Stream

Gerle Creek

Primary Dam Type

Rockfill

Surface Area

1450

Hydraulic Height

94

Drainage Area

7.96

Nid Storage

69309

Structural Height

102

Hazard Potential

Significant

Foundations

Rock

Nid Height

102
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.