On the up – the San Vicente Dam raise project

15 June 2010



Construction is underway at the tallest dam raise in the US which will help drought-stricken San Diego County respond to emergency water needs once complete


Located near Lakeside, an incorporated community of San Diego County, San Vicente Dam was built in 1943. Sixty-six years later, in July 2009, construction began to raise the existing 220ft-high concrete gravity dam by 117ft and add 152,000 acre-feet of water storage.

The project is the largest component of the fourth and final phase of the San Diego County Water Authority’s (SDCWA) $827M Emergency Storage Project (ESP). The ESP, which has been under development for more than a decade, is a system of reservoirs, pipelines, and other facilities that work together to store and move water around the county in the aftermath of a disaster, such as an earthquake. When complete, the entire ESP system will provide more than 90,000 acre-feet of water stored locally for emergency use, enough to supply the region for up to six months.

This new water storage will serve two purposes. About two-thirds of the additional storage will capture surplus water during wet seasons for use in subsequent dry years. The other third of the new reservoir capacity will store water for use in an emergency if the San Diego region’s imported water supply is cut off.

San Diego currently imports about 90% of its drinkable water supply from more than 400 miles away, making this a critical project. “The San Vicente Dam Raise project is a critical part of the Water Authority’s $1.5 billion plan to ensure that our region can call upon locally stored water reserves during emergencies or other periods of limited imported supplies,” said Maureen Stapleton, Water Authority General Manager. “In addition to its importance to regional water supply reliability, this project also brings major economic benefits, creating 5,500 job-years of employment to the San Diego region.”

Construction work

The San Vicente Dam Raise construction is scheduled to run from 2009 to 2012 and is split into several distinct construction phases. The first construction phase, foundation excavation, will not affect the integrity of the existing dam, and has been closely monitored throughout construction. This phase includes all the preparation work before concrete can be applied to raise the dam. The contractor, Barnard Construction Company, Inc, will excavate down to the existing dam’s foundation and will pour concrete in any crevices.

The contractor will also remove about two to three inches of the dry side of the dam to create a good bonding surface for the new concrete. Other work in the first phase includes installing new pipelines and other components near and inside the existing dam.

The next phase of construction will raise the dam with roller compacted concrete (RCC) and is anticipated to begin in the next few months. The downstream side of the existing dam will be completely covered by RCC and will have a new, stair-stepped appearance.

The SDCWA Board of Directors on April 22 approved the award of a $140.2M contract for the application of the RCC to a joint venture partnership of Shimmick Construction Company Inc. /Obayashi Corporation. The JV was selected after a competitive bidding process that drew interest from companies around the globe.

In addition to raising the dam, the construction phase covered by the new contract will include construction of a new saddle dam, a new outlet tower, a new pipeline and control facility and new access roads. Construction is expected to be complete by early 2013.

Later phases of the project will more than double the size of the existing marina facility at the San Vicente Dam, a popular destination for local water sports enthusiasts. A six-lane boat ramp, new docks, additional parking, new service buildings, picnic tables and shade structures will be added. The project is expected to be complete in 2012.

Current situation

Currently, the foundation preparation is more than halfway complete. Barnard Construction has built a small, semicircular steel cofferdam on the upstream (wet) side of the dam. This allows workers to install a new water outlet pipe through the dam. All of this work is being monitored by the State Division of Safety of Dams and will not affect the integrity of the existing dam.

Design, engineering and management

The final design and engineering services for construction of the San Vicente Dam Raise Project was performed by MWH through a $20.4M contract from SDCWA. MWH engineers developed the RCC design, making the San Vicente Dam raise project the tallest of its kind in the world using this method of building concrete dams.

During the three-year construction phase, MWH will provide engineering services, including resident design engineering staff to validate that site features are constructed consistent with design intent and assumptions. MWH engineers will review key submittals for consistency with design requirements and address design-related questions and unexpected issues that may arise during construction. A critical aspect of this review will be the performance of the on-site quarry that will be used for RCC aggregates, which has won awards from American Water Works Association (AWWA) and American Society of Civil Engineers (ASCE) for its environmental stewardship, eliminating thousands of truck deliveries for concrete aggregates from off-site sources.

MWH also engineered SDCWA’s nearby Olivenhain Dam and Reservoir project with the RCC design – which uses no-slump concrete and soil placing techniques to provide an efficient, economical and resilient product. The Olivenhain project, which was completed in January 2005, is a 318ft high dam that added 24,000 acre-feet of reservoir storage as the first phase of the ESP.

The MWH dam design and engineering work for the San Vicente Dam raise project, which was part of the contract awarded in 2006, also included project management, outlet works design, quarry design, value engineering and cost estimating. In addition, MWH scheduled and coordinated quality assurance/quality control reviews with the internal design team technical review committee and owner’s board of senior consultants, as well as coordination and permitting with the State of California Division of Safety of Dams.

A joint venture of consultants Parsons and black-veatch (B&V) will manage the raise project. In an agreement with SDCWA, the JV was contracted to provide pre-construction services through constructability reviews, independent construction management schedules and cost estimates, and contractor pre-qualification. During construction, the construction management staff, working with the Water Authority, are providing construction administration, inspection, change management, schedule monitoring and quality control services for the project, including startup support.

The Parsons/Black & Veatch also has extensive experience with other aspects of the Emergency Storage Project, including work on the state-of-the-art pump station, which will help move water from the San Vicente Reservoir to one of SDCWA’s aqueducts.

Funding

Water Authority construction projects such as the San Vicente Dam Raise are funded through bond sale proceeds. In January 2010, the Water Authority successfully completed a $627M bond sale to provide funds for capital improvement projects for fiscal years 2011 and 2012. Because the bid awarded for this portion of the dam raise construction was significantly below Water Authority estimates, savings derived from the lower bid will allow the funds from the bond sale to be used over a longer period of time.

For further information on the San Vicente Dam Raise Project, please visit: http://www.sdcwa.org/infra/esp-sanvicentedamraise.phtml


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