Water Authority Makes History at San Vicente Dam

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Construction is in full swing on the world’s tallest roller-compacted concrete dam raise, right here in San Diego County. The San Diego County Water Authority is increasing the height of San Vicente Dam in Lakeside by 117 feet, more than doubling the storage capacity of San Vicente Reservoir. The expansion represents the single biggest increase in water storage in our county’s history. It is also the largest dam raise in the U.S.

Roller-compacted concrete is delivered down the dry side of the existing dam in a chute (upper left). The concrete resembles damp dirt or gravel and is worked much like asphalt during road paving. Each layer is rolled out one foot high and compacted before the next layer is applied.

San Vicente Reservoir already has a distinguished history. Constructed by the city of San Diego in 1943, it was the first reservoir in the county to receive imported water when the Water Authority’s First Aqueduct was completed in 1947. The original dam stood at 220 feet and stored up to 90,000 acre feet for use by the city of San Diego.

When dam raise construction is complete, the dam will be 337 feet high and will hold up to 242,000 acre feet. The additional storage will be owned by the Water Authority, and will be used to maintain water reserves for emergencies. If an earthquake or a severe drought curtails our imported water supplies, water from San Vicente Reservoir will provide emergency supplies for the southern portion of the county.

The Water Authority is using roller-compacted concrete to raise the dam because it is just as strong as conventional concrete but can be placed more efficiently. The Olivenhain Dam, constructed by the Water Authority a decade ago, is also a roller-compacted concrete dam.

Roller-compacted concrete is placed nearly continuously, including at night. Here, the contractor has rolled and compacted a layer for the dam foundation. The haul truck in the background is delivering a new batch of concrete for the next layer. The foot of the existing dam is on the upper right.

Workers placed the first layer of concrete for the foundation of the dam raise in September. Thanks to the efficient construction allowed by roller-compacted concrete, the new dam is rising swiftly. It is expected to reach its full height by spring 2012. Additional work will continue at the reservoir through 2015 to establish a new marina and replacement pipeline required by the city of San Diego.

The city of San Diego has continued to operate the reservoir during construction to supply its customers, and will own its original storage capacity after the dam raise is complete. The two agencies will share the cost of operating the expanded reservoir. The city plans to reopen San Vicente Reservoir to the public as soon as the water level reaches the new boat ramp, between 2014 and 2017 depending on the availability of imported water and local rainfall at that time.

The San Vicente Dam Raise is the largest project of the Emergency Storage Project, a system of reservoirs, interconnected pipelines, and pumping stations designed to make water available to the San Diego region in the event of an interruption in imported water deliveries.

New Web Cam Shows Progress at San Vicente Dam

A new web cam system at San Vicente Dam allows the public to witness progress on the world’s largest roller-compacted concrete dam raise. Two cameras offer different views of construction activities, enabling viewers to see weeks of dam raise work compressed into a brief time-lapse video.

Click on Topside View or Downstream View for two vantage points of construction. These high-resolution photos are updated every 30 minutes, providing a current snapshot of dam raise construction. The time-lapse sequences combine these photos, illustrating the construction process.