Loon Lake Main Reservoir Report

Last Updated: December 5, 2025

Loon Lake Main in California is a captivating destination for water resource and climate enthusiasts.


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Summary

This hydroelectric facility, completed in 1963, boasts a rockfill dam standing at 100 feet tall and holding a maximum storage capacity of 69,309 acre-feet. The dam's primary purpose is hydroelectric generation, with recreational opportunities also available on the 1,450-acre surface area of the lake.

Located in El Dorado County, Loon Lake Main is regulated by state agencies for permitting, inspection, and enforcement, ensuring the safety and compliance of the dam structure. Managed by a public utility, this facility on Gerle Creek is designed by Bechtel and falls under the jurisdiction of the California Department of Water Resources. With a significant hazard potential and moderate risk assessment, emergency action plans are in place to address any potential threats to the surrounding area.

The dam's operations are overseen by the Federal Energy Regulatory Commission, with a spillway type of uncontrolled and a maximum discharge capacity of 15,300 cubic feet per second. Despite its remote location, Loon Lake Main offers a unique blend of hydroelectric power generation, outdoor recreation, and environmental stewardship that make it a fascinating site for water resource and climate enthusiasts to explore and appreciate.

Year Completed

1963

Dam Length

2330

Dam Height

100

River Or Stream

Gerle Creek

Primary Dam Type

Rockfill

Surface Area

1450

Hydraulic Height

100

Drainage Area

7.96

Nid Storage

69309

Structural Height

108

Hazard Potential

Significant

Foundations

Rock

Nid Height

108
       
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.