North Fork Diversion Reservoir Report

Last Updated: December 5, 2025

North Fork Diversion, located in Dorrington, California, is a public utility structure managed by the Federal Energy Regulatory Commission.


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Summary

Constructed in 1989 by Sierra Constructors, this hydroelectric dam on the North Fork Stanislaus River serves as a vital resource for the region. With a dam height of 53 feet and a storage capacity of 340 acre-feet, it plays a crucial role in maintaining water supply and generating hydroelectric power.

Regulated by the California Department of Water Resources and the Safety of Dams, North Fork Diversion boasts a low hazard potential and a moderate risk assessment rating. Despite its age, the dam remains in good condition with regular inspections and safety measures in place. Its uncontrolled spillway, with a width of 120 feet, can handle a maximum discharge of 16,300 cubic feet per second, ensuring effective flood control and water management for the surrounding area.

With its gravity design and rock foundation, North Fork Diversion stands as a testament to sustainable water resource management in Alpine County. As climate change continues to impact water availability and quality, structures like this play a crucial role in ensuring a reliable and resilient water supply for both human consumption and ecological needs. Its history, design, and operational efficiency make it a fascinating subject for water resource and climate enthusiasts alike.

Year Completed

1989

Dam Length

220

Dam Height

53

River Or Stream

North Fork Stanislaus River

Primary Dam Type

Gravity

Surface Area

13

Hydraulic Height

27

Drainage Area

27.8

Nid Storage

340

Structural Height

41

Hazard Potential

Low

Foundations

Rock

Nid Height

53
       
Seasonal Comparison

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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.