Forbestown Diversion Reservoir Report

Last Updated: December 5, 2025

Forbestown Diversion, located in Forbestown Powerhouse, California, is a public utility facility designed by Bechtel for hydroelectric purposes.


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Summary

The dam, completed in 1962, is a concrete structure standing at 81 feet tall with a hydraulic height of 80 feet. It serves multiple purposes including hydroelectric power generation, irrigation, and water supply, with a storage capacity of 352 acre-feet.

The dam, situated on the South Fork Feather River, has a spillway width of 230 feet and a maximum discharge capacity of 45,400 cubic feet per second. Despite its low hazard potential, the facility is subject to state regulation, inspection, and enforcement through the Department of Water Resources and the Safety of Dams program. The Federal Energy Regulatory Commission oversees its operation, inspections, and regulatory compliance.

With a moderate risk assessment rating of 3, Forbestown Diversion is a critical infrastructure for water resource management in Butte County. The facility's emergency action plan was last revised in November 2020, ensuring preparedness for any unforeseen events. Water resource and climate enthusiasts can appreciate the unique design and functionality of this essential water infrastructure, serving both the community and the environment.

Year Completed

1962

Dam Length

268

Dam Height

81

River Or Stream

South Fork Feather River

Primary Dam Type

Concrete

Surface Area

12

Hydraulic Height

80

Drainage Area

87.5

Nid Storage

352

Structural Height

81

Hazard Potential

Low

Foundations

Rock

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.