Mobilization has begun in Southern California for excavation of the foundation of what authorities are calling the largest raise of a concrete dam in the U.S. and the largest using roller-compacted concrete in the world. A groundbreaking ceremony on July 9 will kick off the project to raise San Vicente Dam, Lakeside, Calif., in the final phase of the San Diego County Water Authority’s Emergency Storage Project.

“It will more than double the capacity of the reservoir,” says Kelly Rodgers, authority project manager. “San Diego relies primarily on imported water.” Water supplies from the Colorado River and from northern California could be disrupted by an earthquake, so increasing San Diego’s storage will help reduce that threat as well as threat from drought.

An RCC dam will be added to the existing 220-ft-tall concrete-gravity dam built in 1943, to add 117 ft of elevation. The reservoir’s capacity, now 90,000 acre-ft, will be increased by 152,000 acre-ft.

Barnard Construction Co. Inc., Bozeman, Mont., on June 9 received notice to proceed on a $23.7-million contract to prepare the foundation for the raised dam. The authority will prequalify contractors for RCC work, estimated at $250 million to $260 million.

Bids will be sought by January and construction will start in July 2010, says Rodgers. MWH Global, Broomfield, Colo., is designer and a joint venture of Parsons Corp., Pasadena, Calif., and Black & Veatch, Overland Park, Kan., is construction manager. Total construction value is $380 million.