Folsom - Mormon Island Auxiliary Dam Reservoir Report

Last Updated: December 5, 2025

The Folsom - Mormon Island Auxiliary Dam, located in Sacramento, California, is a key structure managed by the Bureau of Reclamation for flood risk reduction along the Blue Ravine river.


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Summary

Completed in 1955, this earth dam stands at a height of 110 feet and has a storage capacity of 1,120,000 acre-feet to protect the surrounding area from potential flooding events. Despite its high hazard potential, the dam has not been assessed for its current condition, highlighting the importance of regular inspections and maintenance to ensure its continued safety and effectiveness.

In addition to flood risk reduction, the Folsom - Mormon Island Auxiliary Dam serves multiple purposes such as hydroelectric power generation, irrigation, recreation, and water supply for the region. Its association with 11 other structures further emphasizes its critical role in managing water resources and supporting various activities in the area. The dam's location in Folsom, under the jurisdiction of the San Francisco District of the US Army Corps of Engineers, underscores its significance in the local water infrastructure and climate resilience efforts.

While the Folsom - Mormon Island Auxiliary Dam does not have a spillway, its design and construction by the Bureau of Reclamation demonstrate a commitment to effective water management and flood protection. With a high-risk assessment rating and limited information on its current condition, continued monitoring and risk management measures are essential to ensure the safety and reliability of this vital infrastructure in the face of evolving climate challenges.

Year Completed

1955

Dam Length

4820

Dam Height

110

River Or Stream

BLUE RAVINE

Primary Dam Type

Earth

Surface Area

11180

Hydraulic Height

105

Drainage Area

120

Nid Storage

1120000

Structural Height

110

Hazard Potential

High

Foundations

Rock

Nid Height

110
       
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 - Mormon Island Auxiliary DamBP36 Preview BP36
Folsom - Mormon Island Auxiliary DamBP44 Preview BP44
Folsom - Mormon Island Auxiliary DamBP49 Preview BP49
Folsom - Mormon Island Auxiliary DamBP35 Preview BP35
Folsom - Mormon Island Auxiliary DamBP43 Preview BP43
Folsom - Mormon Island Auxiliary DamBP37 Preview BP37