Beardsley Reservoir Report

Last Updated: December 5, 2025

Beardsley Dam, located in Sonora, California, is a key structure along the Middle Fork Stanislaus River designed by Tudor-Goodenough and completed in 1957 for hydroelectric power generation.


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Summary

This earth-type dam stands at a height of 278 feet, with a hydraulic height of 276 feet, and a structural height of 284 feet. With a normal storage capacity of 97,500 acre-feet and a maximum storage of 97,800 acre-feet, Beardsley Dam plays a crucial role in flood risk reduction, hydroelectric power production, and recreation in the region.

Managed by the Federal Energy Regulatory Commission (FERC), Beardsley Dam is under state regulation and inspection by the California Department of Water Resources (DWR) for its safety and compliance with state laws. The dam's spillway, with a width of 174 feet and controlled design, can handle a maximum discharge of 90,000 cubic feet per second. Despite its high hazard potential, the condition assessment for Beardsley Dam is currently not available, indicating a need for further evaluation and risk management measures to ensure its continued safety and functionality.

With its very high risk assessment rating and significant storage and discharge capacities, Beardsley Dam is a critical infrastructure for water resource management and climate resilience in the Tuolumne County region. As a public utility structure serving various purposes, including flood control and renewable energy generation, Beardsley Dam's operation and maintenance are essential for safeguarding the surrounding communities and ecosystems. Ongoing monitoring, inspection, and risk management efforts will be crucial in ensuring the long-term safety and sustainability of this vital water resource facility.

Year Completed

1957

Dam Length

1000

Dam Height

278

River Or Stream

Middle Fork Stanislaus River

Primary Dam Type

Earth

Surface Area

720

Hydraulic Height

276

Drainage Area

310

Nid Storage

97800

Structural Height

284

Outlet Gates

Tainter (radial) - 4

Hazard Potential

High

Foundations

Rock

Nid Height

284
       
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.