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San Gabriel Reservoir Post-Fire Emergency / Sediment Removal Program

Client: Los Angeles County of Public Works Department

Location: Azusa, CA

Project Value: $93M (approx.)

Project Description:  In 2020, the Bobcat Fire burned approximately 180 square miles of the San Gabriel Mountains and the surrounding area. As a result of this fire, there was increased erosion that added significant amounts of sediments and debris to the San Gabriel Reservoir, reducing its ability to handle storms and retain water. This $93 million project removed 4.9 million cubic yards of sediment from the reservoir. To enable the County to meet and maintain acceptable flood control standards, W.A. Rasic reconstructed the four-mile-long access road from the San Gabriel Reservoir to the sediment placement site and prepared the 15-acre site to receive sediment, all of which required that we establish extensive stormwater prevention and environmental measures. Some 14,000 feet of 36-inch high-density polyethylene (HDPE) pipe we installed was used in conjunction with four, 12-inch pumps to dewater approximately 230 million gallons from the reservoir. At the peak, we had five excavators running, including two Komatsu PC-1250s, along with 32 other pieces of equipment, which excavated and loaded sediment into 60 dump trucks, maintained the haul road, and managed the sediment deposit site. To control erosion, W.A. Rasic revegetated the slopes of the sediment placement site according to the plan approved by the U.S. Forest Service. The work was completed under strict environmental constraints that required daily construction monitoring activities.