ASCE Los Angeles Section

The Eagle Canyon Dam project is located southerly of Canyon Plaza Drive in the City of Palm Springs and is built to protect for homes & businesses in Cathedral City.  Portions of the project site are also located within tribal lands of the Agua Caliente Band of Cahuilla Indians. The Dam is located south of, and protects, Highway 111 which is a major arterial to the desert cities.

During periods of heavy rainfall, floodwaters, mud, and debris have funneled down Eagle Canyon and have damaged structures and properties located immediately downstream of the Canyon and in Cathedral City (most recently on July 20, 2008 and August 30, 2012). 

The Eagle Canyon Dam and Debris Basin is designed to hold 185 acre-feet of water and 40 acre-feet of debris. The Dam provides protection from a 100-year flood event in which the peak inflow rate of water is 720,000 gallons per minute, equivalent to filling 50 swimming pools per minute.

Construction of the $10.6 million Dam began in May 2013. The Dam became functional in June 2014 and was completed in September 2015. Additionally, the project included a $1.2 million remediation of hazardous materials that were present as a result of illegal dumping and other activities that previously occurred on the project site. The environmental cleanup was funded by the Cities of Palm Springs and Cathedral City.

The dam now provides sufficient flood peak attenuation and conveyance to protect public health and safety, reduce potential damage to develop properties located downstream from the project site and prevent sediment and debris from flowing into public streets and private property.

The last dam that was constructed by Riverside County Flood Control and Water Conservation District was in 1993. In 1999, the Metropolitan Water District constructed a three-dam project, Diamond Valley Lake. Since then no other dam was built in Riverside County until Eagle Canyon Dam. The dam design had sustainability in mind as the embankment was constructed of locally available materials obtained primarily from the excavations of the dam foundation. The construction of this facility is a great asset to the community as Eagle Canyon Dam removed 190 acres and around 500 structures from the floodplain. Removing these buildings from the floodplain eliminated the cost of flood insurance to the community and protected them from future flooding.

Obstacle One: Environmental Clean-up needed for Hazardous Material
Remediation of hazardous materials that were present as a result of illegal dumping and other activities that previously occurred on the project site was required prior to construction of Eagle Canyon Dam. The site remediation work took longer than expected as some areas had lead shot mixed more deeply into the streambed than we expected.  A relatively small area required multiple scrape-test-haul cycles but our contractor couldn’t begin the foundation excavation in earnest until these soils tested as clean.  Although time-consuming, the final volume of lead-impacted soils was less than predicted.  As payments to the contractor are based on the actual volume hauled, the cost saving was substantial compared to the approved contract amount ($1.2 million vs. $2 million).

Obstacle Two: Discovery of Earthquake Fault
The discovery of previously unknown earthquake faults during the beginning stages of construction was a terrifying finding. The existence of the faults was not in the Geotechnical Report. The discovery required excavation of investigation trenches outside of the dam’s original footprint. Luckily, the District’s consulting Geologist was able to support a finding that the faults are much older than 35,000 years (35,000 years of dormancy is the State’s threshold of concern).  DSOD’s geologist concurred so the contractor moved forward with construction of the dam.

Obstacle Three: Joints and fractures in the rock near the spillway
The project’s original geotechnical investigation had concluded that the cut slopes in the spillway would be stable under static and seismic conditions.  However, in one area, the joints and fractures in the rock were found to be more extensive than expected and oriented such that seismic loading could cause rockfall onto the right side of the spillway.  The District, in consultation with our onsite geotechnical consultant, determined that the most efficient remedy is additional concrete lining bolstered by rock bolt anchors (also known as tie-backs) to lock down the problematic cut slope.  The approved plans and specifications did not include specialized work of this nature.
District design staff and the geotechnical consultant worked up design drawings and detailed specifications for the additional work.  The revised plans and specifications were reviewed and approved by the State of California Division of Safety of Dam.

Summer thunder storm early morning created flood in desert cities. Eagle Canyon flood waters caused extensive damage in Cathedral City. Driver rescued from vehicle caught in flood waters July 20, 2008
https://www.youtube.com/watch?v=OXNgG1jb070

The construction of Eagle Canyon Dam and Debris Basin is a great asset to the community as the dam removed 190 acres and around 500 structures from the floodplain. Removing these buildings from the floodplain eliminated the cost of flood insurance to the community and protected them from future flooding.

The Eagle Canyon Dam and Debris Basin project is located southerly of Canyon Plaza Drive in the City of Palm Springs and is built to protect for homes & businesses in Cathedral City.  Portions of the project site are also located within tribal lands of the Agua Caliente Band of Cahuilla Indians. The dam is located south of, and protects, Highway 111 which is a major arterial to the desert cities.
During periods of heavy rainfall, floodwaters, mud, and debris have funneled down Eagle Canyon and have damaged structures and properties located immediately downstream of the Canyon and in Cathedral City.
The dam is designed to hold 185 acre-feet of water and 40 acre-feet of debris and provides protection from a 100-year flood event in which the peak inflow rate of water is 720,000 gallons per minute, equivalent to filling 50 swimming pools per minute.
Construction of the $10.6 million Dam began in May 2013. The dam became functional in June 2014 and was completed in September 2015. Additionally, the project included a $1.2 million remediation of hazardous materials that were present as a result of illegal dumping and other activities that previously occurred on the project site.
The dam design had sustainability in mind as the embankment was constructed of locally available materials obtained primarily from the excavations of the dam foundation. The construction of this facility is a great asset to the community as Eagle Canyon Dam removed 190 acres and around 500 structures from the floodplain. Removing these buildings from the floodplain eliminated the cost of flood insurance to the community and protected them from future flooding.