Folsom Left Wing Reservoir Report

Last Updated: December 5, 2025

Folsom Left Wing is a significant federal-owned structure located in Folsom, California, along the American River.


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Summary

Built in 1955 by the Bureau of Reclamation, this earth dam stands at a towering height of 145 feet, with a primary purpose of flood risk reduction. It also serves as a source for hydroelectric power, irrigation, recreation, and water supply, showcasing its multi-faceted role in managing water resources in the region.

With a storage capacity of 1,120,000 acre-feet, Folsom Left Wing plays a crucial role in water management, particularly during times of high discharge and potential flooding. Despite its high hazard potential, the condition assessment of the dam is currently not available, highlighting the need for ongoing monitoring and maintenance to ensure its structural integrity. The dam lacks a spillway, showcasing the engineering design to mitigate flood risks and manage water levels effectively.

As a key component in the water infrastructure of the region, Folsom Left Wing serves as a vital resource for flood protection and water management along the American River. Its strategic location and multi-purpose design make it a critical asset for ensuring water security and mitigating risks in the face of changing climate patterns and extreme weather events.

Year Completed

1955

Dam Length

2100

Dam Height

145

River Or Stream

AMERICAN RIVER

Primary Dam Type

Earth

Surface Area

11180

Hydraulic Height

140

Drainage Area

1570

Nid Storage

1120000

Structural Height

145

Hazard Potential

High

Foundations

Rock

Nid Height

145
       
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.
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Area Campgrounds

Location Reservations Toilets
Folsom Left WingBP36 Preview BP36
Folsom Left WingBP35 Preview BP35
Folsom Left WingBP37 Preview BP37
Folsom Left WingBP38 Preview BP38
Folsom Left WingBP43 Preview BP43
Folsom Left WingBP44 Preview BP44