Lake Alta Reservoir Report

Last Updated: December 5, 2025

Lake Alta, located in Placer County, California, is a captivating water resource nestled in the picturesque city of Folsom.


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Summary

Managed by the local government, this reservoir serves multiple purposes including hydroelectric power generation, irrigation, and water supply. The dam, completed in 1862, stands at a height of 22 feet and has a storage capacity of 270 acre-feet, making it a vital component of the region's water infrastructure.

With a surface area of 23 acres and a drainage area of 0.08 square miles, Lake Alta plays a crucial role in regulating the flow of the Truckee North Fork American River. The dam's hazard potential is classified as high, yet its current condition is assessed as fair. Regular inspections are conducted to ensure the dam's safety and integrity, with the most recent assessment dated back to September 2017. In the event of an emergency, the reservoir's Emergency Action Plan is prepared and regularly reviewed to meet safety guidelines.

Water and climate enthusiasts will find Lake Alta to be a fascinating example of sustainable water management in California. Its historical significance, combined with its essential role in providing water resources for the region, underscores the importance of responsible stewardship and maintenance of this vital infrastructure. As climate change continues to impact water resources, Lake Alta stands as a testament to the resilience and adaptability of water systems in the face of evolving environmental challenges.

Year Completed

1862

Dam Length

955

Dam Height

22

River Or Stream

Tr Nfk American R

Primary Dam Type

Earth

Surface Area

23

Hydraulic Height

20

Drainage Area

0.08

Nid Storage

270

Hazard Potential

High

Nid Height

22
       
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.