Quest Ventures

Santa Anita Dam

The Santa Anita Dam is a thin arch concrete structure originally constructed in 1927 to prevent seasonal storm floods in the Los Angeles basin. The dam measures 225 feet in height, 628 feet in length, with a base width of 60 feet and a crest width of 10 feet. The dam’s base rests at elevation 1100 and the crest tops off at elevation 1325. The Santa Anita Dam is located on the border of the City of Arcadia, California, in the western San Gabriel Valley in Los Angeles County, approximately 15 miles northeast of downtown Los Angeles. In response to a recent seismic stability analysis, the California Department of Water Resources Division of Safety of Dams (DSOD) has mandated that modifications to the Santa Anita Dam are required in order to comply with current seismic stability standards.

To comply with the DSOD requirements, the Los Angeles County Department of Public Works (LADPW) is required to operate the dam at a maximum reservoir elevation of 1230 which is 28 feet lower than the current operating elevation. The current sediment level in the reservoir is at elevation 1212 which is hindering valve operation at the dam thus impacting drawdown of the reservoir after storm events. In order to operate at the maximum elevation of 1230, a new cast in place concrete riser will be constructed at the face of the dam which will allow water above elevation 1230 to flow freely through the outlet. In addition, sediment will be removed from its current elevation of 1212 to elevation 1175 which will allow normal operation of existing gates and valves to resume and will provide increased flood storage capacity.

Quest’s scope of work consists of draining the Santa Anita Reservoir and excavating approximately 400,000 cubic yards (CY) of sediment and debris. This material will be transported from the reservoir via a conveyor belt system designed and fabricated by Quest. The conveyor system begins upstream of the dam at a 1,500 long tunnel which runs through the left dam abutment and then proceeds overland approximately two miles to the sediment placement sites. The conveyor approach was mandated as the best alternative to mitigate environmental, noise, dust and air pollution impacts associated with transporting the sediment. Approximately 225,000 CY of sediment will be placed at the existing lower sediment placement site and the remaining 175,000 CY of sediment will be placed at a newly constructed middle sediment placement.

Structural modifications to the dam’s inlet / outlet works will also be performed including the removal of an existing sluiceway trashrack, construction of a new cast in place concrete riser structure and installation of one 72” and two 24” hydraulically operated slide gates.

Construction of this $9,500,000 project is scheduled to start in December 2010 and complete in November 2011.