Lake Spaulding No. 3 Auxiliary Reservoir Report

Last Updated: December 5, 2025

Lake Spaulding No.


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Summary

3 Auxiliary is a concrete gravity dam located in Nevada County, California, near the city of Washington. Built in 1919, this hydroelectric structure stands at 91 feet tall and has a capacity of 74,773 acre-feet, serving as a vital component of the South Yuba River's water resource management system. Managed by a private entity, this dam is regulated and inspected by the California Department of Water Resources for safety compliance.

The dam's spillway type is uncontrolled, with a width of 90 feet, and it has a high hazard potential due to its location and structural components. The dam's emergency action plan was last revised in December 2020, ensuring that proper guidelines are in place for potential risks. Lake Spaulding No. 3 Auxiliary has a moderate risk assessment rating, indicating the need for ongoing monitoring and risk management measures to maintain public safety and environmental integrity in the face of changing climate patterns and water resource demands.

As a crucial part of the Federal Energy Regulatory Commission's oversight, this dam plays a significant role in supporting hydroelectric power generation and water supply for the surrounding area. With its historical significance and engineering ingenuity, Lake Spaulding No. 3 Auxiliary stands as a testament to the enduring importance of sustainable water resource management in the face of evolving climate challenges.

Year Completed

1919

Dam Length

813

Dam Height

91

River Or Stream

South Yuba River

Primary Dam Type

Concrete

Surface Area

698

Hydraulic Height

89.5

Nid Storage

74773

Structural Height

94.5

Hazard Potential

High

Nid Height

95
       
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.