Major construction on the San Diego County Water Authority’s San Vicente Dam Raise project has reached its biggest phase. Concrete placement to raise the main dam at the San Vicente Reservoir by 117 feet is now under way.
Upon completion, the raised dam will create room for an additional 52,100 acre-feet of water for potential emergency use, and an additional 100,000 acre-feet of capacity to store water during wet years, for use in subsequent dry years. (An acre-foot is about 326,000 gallons, or enough to supply two average single-family households of four people for a year.)
“We’ve entered the phase of construction where the new, bigger dam will really take shape,” said Water Authority Board Chair Michael T. Hogan. “This vital regional water infrastructure project will help enhance the reliability of San Diego County’s water supply for generations to come.”
The project is one of the final components of the Water Authority’s $1.5 billion Emergency Storage Project and broader $3.5 billion Capital Improvement Program. The Emergency Storage Project is a system of water conveyance and storage facilities that will ensure San Diego County will have up to a six-month supply of locally stored water and can move that water around the region in case of a natural disaster or other interruption to imported water deliveries.
The roller-compacted concrete process, which was also used to construct the Water Authority’s Olivenhain Dam, is as strong as conventional concrete and can be placed in significantly less time. This method requires minimal formwork and less curing time, allowing workers to place about a one-foot layer of new concrete, called a “lift,” per day.
The city of San Diego completed the San Vicente Dam in 1943. It was the first reservoir in the county to be connected to the Water Authority’s aqueduct in 1947. The existing dam, still owned and operated by the city of San Diego, is 220 feet high. The raised dam will be 337 feet high and will have more than double the volume of the existing dam.
The project requires approximately 650,000 cubic yards of roller-compacted concrete, which is enough to fill a football field more than 28 stories high. The concrete travels approximately half a mile on a conveyor belt from the concrete batch plant in the reservoir’s former marina area to the main dam. It then drops through a chute – currently almost 200 feet high – where it is roller-compacted into place.
Project construction began in 2009. To prepare the dam to receive the new roller-compacted concrete, about two inches of concrete was removed from the downstream face of the dam, using a hydro-demolition process. Approximately one foot of concrete also was removed from the top of the dam.
In August 2011, the Water Authority began construction on a saddle dam that fills in a low point in the hills around the reservoir that will help contain its new, higher water level.
Producing the aggregate on site to make the concrete will prevent more than 100,000 truck trips through the community. The project is helping stimulate the local economy by creating approximately 1,100 jobs per year, with a total of 5,500 jobs over the five-year life of the project.
Once the dam raise is complete and the reservoir is refilled, it will reopen to recreation with a number of enhancements, including an improved access road, an expanded boat ramp and parking area and new shade trees and picnic areas. Refilling the reservoir is anticipated between late 2014 and 2017, depending on rainfall and supply and demand for water.
Major construction of the San Vicente Dam Raise project will be completed in 2013. Additional phases of the project, including building a new marina, a replacement pipeline and restoration of project construction areas, will begin in mid-2013 after the dam raise itself is complete.