San Vicente Dam Raising is Biggest of its Type in the World

San Vicente Reservoir dam is a hive of activity as work progresses on the effort to increase emergency water storage for San Diego county.

"This is the largest dam raise in the United States and the largest roller compacted concrete dam raise in the world," Bill Rose, director of engineering for San Diego County Water Authority (CWA) said Tuesday.

When finished, the reservoir will be able to store 242,000 acre-feet of water. Its current capacity is just over 90,000 acre-feet, said project manager Kelly Rodgers. An acre-foot is enough to supply two average single-family households for a year, she said.

Rock for the concrete is being taken out of a hill by the reservoir and crushed on site, to avoid taking loaded trucks through the community of Lakeside, Rodgers said. Rollers are used to speed the setting of the concrete, rather than using the chemical curing process, which is less efficient for a project this size, she said.

"The process is similar to paving an asphalted road," she said.

The dam will be raised from its current height of 220 feet to a total of 337 feet. Concrete is set in layers in front of the existing dam and will bond to the dam by means of a paste and also through the roughening of the old dam surface to allow for better adherence, Rose said. There is no reinforcing used in the process.

"It's like a layer cake," he said. "We do about one foot a day."

The dam raising is the final stage of a $1.5 billion emergency water storage project undertaken by the CWA in case imported water from the north is cut off. The project began with the construction of Olivenhain Dam, finished in 2003, Rodgers said. It also includes the San Vicente Tunnel, pump station and surge tank, as well as the Lake Hodges pump station and pipeline and a North County pump station off Interstate 15, north of Twin Oaks Valley.

The raised San Vicente dam is being built to withstand a 7.5 magnitude earthquake on the Richter scale, based on the history of San Diego county fault lines, Rose said.

The project is expected to be completed in 2013. Rose said it will take until at least 2017 to raise the water level.

"There is a minor watershed that drains in here, but most of it will be imported water," he said.

San Vicente Reservoir holds untreated water.

Boating, fishing and wakeboard enthusiasts will have a new marina and access road when the reservoir re-opens for recreational use, possibly as soon as 2017.

"This is a dream road," said Rose, as he showed reporters up the hill to where the old marina was located. "The old one was scary."

The new paved road has two lanes and is not as steep as the old one, he said.

Two deer crossed the road as Rose's vehicle descended the hill on Tuesday.

"Obviously they're not concerned about the construction out here," he said, with a chuckle. "We saw a mountain lion the other day."

Click here to see aerial views of the reservoir, by Channel 10 News.

City News Service contributed to this report.