San Antonio Dam Reservoir Report

Last Updated: December 5, 2025

San Antonio Dam, also known as San Antonio Reservoir, is a Federal-owned structure located in Claremont, California.


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Summary

Built in 1956 by CESPL, this Earth-type dam stands at a height of 160 feet and spans 3850 feet across San Antonio Creek. With a storage capacity of 11,880 acre-feet, the dam primarily serves the purpose of flood risk reduction along with a maximum discharge capacity of 53,700 cubic feet per second.

Managed by the US Army Corps of Engineers, San Antonio Dam is considered to have a high hazard potential and undergoes regular inspections and risk assessments to ensure its structural integrity. The dam is equipped with an uncontrolled spillway and vertical lift outlet gates to manage water levels and mitigate flood risks effectively. The risk management measures implemented by USACE include continual monitoring, prioritizing activities to reduce risks, and engaging with emergency managers and the public to raise awareness and preparedness for potential dam-related emergencies.

In the face of severe weather events and changing water levels, San Antonio Dam remains a critical structure for flood control in the region. Through proactive risk management strategies and ongoing maintenance efforts, USACE is dedicated to ensuring the safety and functionality of the dam to protect surrounding communities and water resources.

Year Completed

1956

Dam Length

3850

Dam Height

160

River Or Stream

SAN ANTONIO CREEK

Primary Dam Type

Earth

Surface Area

1

Hydraulic Height

130

Drainage Area

27

Nid Storage

11880

Outlet Gates

Vertical Lift - 0

Hazard Potential

High

Nid Height

160
       
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.