Buck Island Auxiliary Reservoir Report

Last Updated: December 5, 2025

Buck Island Auxiliary is a crucial component of California's water resource infrastructure, serving as a hydroelectric facility with a primary purpose of generating electricity and providing recreational opportunities.


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Summary

Built in 1963 by Bechtel, this concrete gravity dam stands at 25 feet high and spans 244 feet in length, with a storage capacity of 1070 acre-feet. Located in El Dorado County, California, along Rockbound Creek in the city of Coloma, this dam is regulated by state agencies and overseen by the Federal Energy Regulatory Commission.

With a low hazard potential and a moderate risk assessment rating, Buck Island Auxiliary has a spillway width of 147 feet and a maximum discharge rate of 13,000 cubic feet per second. The dam is inspected regularly, with the last assessment conducted in August 2019. While the condition assessment is currently listed as not available, emergency action plans have been prepared and updated, ensuring that the dam is equipped to handle any potential risks or emergencies that may arise.

Overall, Buck Island Auxiliary plays a vital role in water resource management and climate resilience efforts in California. As a key contributor to the state's energy production and water supply, this dam exemplifies the intersection of infrastructure development, regulatory oversight, and emergency preparedness in ensuring the safety and sustainability of water resources in the region.

Year Completed

1963

Dam Length

244

Dam Height

25

River Or Stream

Rockbound Creek

Primary Dam Type

Concrete

Surface Area

78

Hydraulic Height

19.5

Nid Storage

1070

Structural Height

25

Hazard Potential

Low

Nid Height

25
       
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.