Alpine Main Reservoir Report

Last Updated: December 5, 2025

Alpine Main, also known as Alpine No.


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Summary

1, is a privately owned dam located in the picturesque county of Alpine, California. Built in 1891, this rockfill dam stands at a height of 49 feet and serves multiple purposes including hydroelectric power generation, recreation, and water supply. With a storage capacity of 4,300 acre-feet and a drainage area of 5.3 square miles, the dam plays a crucial role in managing water resources in the region.

Managed by the Federal Energy Regulatory Commission (FERC) and regulated by the California Department of Water Resources (DWR), Alpine Main has a high hazard potential and a moderate risk assessment rating. The dam's primary function is to harness the power of Silver Creek for hydroelectricity, while also providing opportunities for recreational activities and supplying water to the surrounding areas. With a structural height of 81.3 feet and a hydraulic height of 78.3 feet, Alpine Main is a key component of the region's water infrastructure.

Despite its age, Alpine Main has undergone regular inspections and is equipped with emergency action plans to ensure the safety of downstream communities in case of a dam failure. With its historical significance and ongoing role in water management, Alpine Main stands as a testament to the enduring importance of dams in balancing the needs of water resource management and climate adaptation in California's diverse landscapes.

Year Completed

1891

Dam Length

400.5

Dam Height

49

River Or Stream

Silver Creek

Primary Dam Type

Rockfill

Surface Area

172

Hydraulic Height

78.3

Drainage Area

5.3

Nid Storage

4300

Structural Height

81.3

Hazard Potential

High

Nid Height

81
       
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.