Under the contract, a large excavation on the downstream side of the dam will remove loose and liquefiable foundation soils, and the excavation will be refilled with dense compacted materials. In addition, a large stability berm will be constructed on the downstream side of the dam; the dam’s crest will be raised three feet; and a second stability berm will be added on the upstream side of the dam. The work is scheduled to take place between October 2011 and winter of 2013.
Prior field investigations at Echo Dam indicated that the foundation soils underlying both the dam and spillway are potentially liquefiable during a substantial earthquake, which could cause the dam and spillway to deform. A second contract to modify the spillway is scheduled to be awarded in September 2012. The entire seismic modification project is scheduled to be completed by the end of 2014.
Echo Dam is a 158ft high zoned earthfill structure on the Weber River. Part of the Weber River Project, Echo Dam was constructed between 1927 and 1931 to help supply supplemental irrigation water to approximately 109,000 acres of land west of the Wasatch Mountains. Echo Dam is operated by the Weber River Water Users Association.
