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Santa Fe Dam

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Location and Description

Santa Fe Dam and Reservoir is a flood risk management project constructed and operated by the U.S. Army Corps of Engineers, Los Angeles District.  Completed in 1949, the project is located on the San Gabriel River about four miles downstream from the mouth of the San Gabriel Canyon. The San Gabriel River originates on the southern slopes of the San Gabriel Mountains.  It flows through precipitous canyons to the base of the mountains, thence across a broad alluvial cone to Santa Fe Reservoir, and through the San Gabriel Valley to Whittier Narrows Reservoir.

Santa Fe Dam is an essential element of the Los Angeles County Drainage Area flood control system. The primary purpose of the dam is to reduce the risk of flood damage for the densely populated area between the dam and Whittier Narrows Reservoir.  The operation of Santa Fe Dam is coordinated with the operation of other Corps dams in the LACDA system.  Santa Fe Dam contains 16 six-foot wide by nine-foot high hydraulically operated slide gates.  The combined maximum capacity of the sixteen outlets is 41,000 cubic feet per second.  During "stand-by" position, one gate is opened at 0.5 feet and the rest are in a closed position.  This gate setting is designed to pass low flows and build a debris pool during high inflows.  Discharge rates within the debris pool range allow the Los Angeles County Department of Public Works to divert the flow to its spreading facilities, thereby enhancing water conservation.  Once the reservoir level reaches 456 feet, flood control releases are initiated.  During recession, the flood pool is drained as rapidly as possible, consistent with the achievement of downstream flood control.  This is done to empty the flood control pool in preparation for the next flood.  As soon as the flood pool is drained, releases are reduced so LACDPW can resume water conservation operations.  Santa Fe Dam's spillway structure is of an overflow concrete ogee type located in the right or northwestern abutment of the dam.  The spillway has a crest length of 1,200 feet and a crest elevation of 496 feet.  Immediately downstream of the overflow section of the spillway structure is a concrete lined stilling basin.  The spillway channel is 1,200 feet wide and extends about 5,000 feet from the end of the stilling basin.  During spillway flow, the gates are closed gradually to maintain the combination of the spillway flow and outlet works flow to 41,000 cfs.

Dam Safety Issues

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

Santa Fe Dam received a Dam Safety Action Class II, or DSAC II, rating based on a Screen Portfolio Risk Analysis, or SPRA, conducted in March 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.

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

  • Failure from embankment seepage and piping at outlet conduit
  • Seepage and piping along the conduit and access gallery
  • Transverse cracking that allows a subsequent high pool event to begin internal erosion leading to head cutting and overtopping resulting from a significant seismic event
  • Internal erosion into open gravel foundation soils under the conduit (suffusion)
  • Saturation of one or more liquefiable layers in the foundation causing liquefaction leading to settlement or deformation and overtopping resulting from a significant seismic event occurring while the pool is of long enough duration
  • Channel jumping and/or overtopping of the levees upstream resulting from the hydraulic capacity of the inlet structure and upstream channel restricting flow into the dam

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

  • Inspection and monitoring
  • Flood mapping
  • Updating the Emergency Action Plan
  • Coordination with local interests/tabletop emergency exercise
  • Installing piezometers adjacent to the outlet conduit

What’s next?

The Corps will conduct an Issue Evaluation Study (IES), based on the national priority list and availability of future funding, to be completed approximately one year after initiation, in order to reevaluate the Santa Fe Dam DSAC Rating.

  • The future studies do not require altering the operations of Santa Fe Dam.
  • Completion of the future studies will confirm concerns and determine the most appropriate method to address them.
  • Potentially, some modification, rehabilitation or repairs may be needed.
  • The evaluation process is expected to take about four years.

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 Santa Fe Dam does not mean 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 emergency action plans have been 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 654 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.

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