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Aerial view of San Antonio Dam.

Aerial view of San Antonio Dam. (Photo by courtesy photo)

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San Antonio Dam

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Location and Description

San Antonio Dam is a flood risk management and water conservation project located in San Bernardino and Los Angeles counties about four miles northeast of Claremont and 38 miles east of Los Angeles.

San Antonio Dam works in conjunction with the San Antonio and Chino Creek Channels Improvements Project and was authorized (as part of the Santa Ana River Basin flood damage reduction program) by the Flood Control Act of June 22, 1936 (PL 74-738) and the Flood Control Act of June 28, 1938 (PL 75-761). Construction of the dam began in April 1952 and ended in May 1956. The construction of the San Antonio and Chino Creek channels occurred between 1956 and 1960.

The Los Angeles District operates and maintains the dam, reservoir and outlet works and for developing the flood risk management plan for San Antonio Dam.

Dam Safety Issues

Public safety is our number one priority. The primary objective of our Dam Safety Program is to maintain public safety by making sure the dams owned and operated by the Corps are safe, and risks to the public are minimized. An integral part of the program is the risk-informed screening process. Dams are classified based upon confirmed or unconfirmed dam safety issues, the combination of life or economic consequences should failure occur and the probability of failure. This process enables us to prioritize dam safety actions to correct deficiencies, which include interim risk reduction measures to be undertaken while further investigations are conducted and remedial actions are implemented.

Current Status

San Antonio Dam received a Dam Safety Action Class II, or DSAC II, rating in December 2008 based on a Screen Portfolio Risk Analysis, or SPRA, conducted in May 2007. A DSAC II rating is given to dams where failure could begin during normal operations or be initiated as the consequence of an event. The likelihood of failure from one of these occurrences, prior to remediation, is too high to assure public safety; or the combination of life or economic consequences with probability of failure is very high.

San Antonio Dam received a DSAC II rating because of the potential for:

  • Failure from foundation seepage and piping
  • Failure of intake or channel walls under MDE
  • Failure from overtopping of a PMF

As a result of San Antonio Dam’s DSAC II rating, the Corps has developed a plan to implement the following Interim Risk Reduction Measures, or IRRMs:

  • Remote monitoring
  • Inspection and monitoring
  • Update Emergency Action Plan
  • Pre-position materials
  • Coordinate with local interests/conduct table-top exercise
  • Improve flood mapping downstream of the dam

What’s next?

  • The Corps will begin an Issue Evaluation Study (IES), based on the national priority list and availability of future funding and staffing, to be completed approximately one year after initiation, in order to reevaluate the San Antonio Dam DSAC Rating.
  • If modifications are needed to address potential failure modes at the dam, the Corps will begin a Dam Safety Modification Study (DSMS) to be completed approximately 36 months after initiation.

Public Safety is Number One Priority

Public safety is our number one priority. While we cannot completely eliminate risk, we can reduce it. Our screening and classification of San Antonio Dam does not mean that failure is taking place. It means we have identified dam safety issues that don’t meet industry standards and the risk to public safety is unacceptable. Routine inspections and operation of the dam will continue and an emergency action plan was developed in coordination with local emergency management officials. Currently, there is no evidence to suggest an emergency situation exists or is about to occur.

Background

The U.S. Army Corps of Engineers owns and operates 694 dams that serve a variety of purposes, including navigation, flood damage reduction, water supply, irrigation, hydropower, recreation, environmental enhancement and combinations of these purposes. As part of our responsibility in managing these dams, the Corps has a comprehensive Dam Safety Program that has public safety as its primary objective. Corps dams are routinely inspected and continually evaluated for safety in compliance with the Federal Guidelines for Dam Safety issued in 1979 and Engineering Regulation ER 1110-2-1156, Safety of Dams – Policy and Procedures.


corps dams engineers flood risk management flood risk reduction USACE