US Army Corps of Engineers
Los Angeles District Website

Fact Sheet

Dam Safety Program

Lopez Dam

Published June 28, 2012
Aerial view of Lopez Dam.

Aerial view of Lopez Dam.

Location and Description

Lopez Dam is a flood risk management project located on the Pacoima Wash in the north central part of the San Fernando Valley, about 22 miles northwest of Los Angeles, two miles northeast of San Fernando and three miles northwest of Hansen Dam. It lies entirely within the city and county of Los Angeles.

Lopez Dam is designed to reduce the risk of damage from debris-laden flood waters for large areas between the dam and the Los Angeles River. It is an integral unit on the Pacoima-Tujunga Wash system of tributaries to the Los Angeles River. Lopez Dam operates under the approved comprehensive plan for flood risk management in the Los Angeles County Drainage Area, or LACDA.

Lopez Dam was constructed Lopez Dam in 1954, authorized by the Flood Control Act, approved 22 June 1936 (Public Law 738, 74th Congress) and extended and amended by subsequent Flood Control Acts of 1937, 1938, 1941, 1944, and 1946. The plan for construction, in accordance with the recommendations contained in the report dated 11 April 1940 by the Chief of Engineers, and submitted in House Document 838, 76th Congress, 3rd session, was authorized by the Flood Control Act, approved 18 August 1941.

The Los Angeles District operates and maintains the dam, reservoir and outlet works and develops the flood risk management plan for Lopez 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

Lopez Dam received a Dam Safety Action Class II, or DSAC II, rating based on a Screening Portfolio Risk Analysis, or SPRA, conducted in July 2009. 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.

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

  • Embankment Seepage and Piping under the Probable Maximum Flood (PMF) event
  • Foundation Seepage and Piping under the Probable Maximum Flood (PMF) event

As a result of Lopez Dam’s DSAC II rating, the Corps has implemented the following Interim Risk Reduction Measures, or IRRMs:

  • Inspection and monitoring
  • Pre-positioning of materials
  • Updating the Emergency Action Plan and coordinating with downstream agencies
  • Conducting a tabletop emergency exercise
  • Updating flood mapping
  • Building a downstream berm

What’s next?

  • The Corps will conduct 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 Lopez 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 Lopez 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.


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.