MWH-designed project will make history as tallest dam raise in U.S., tallest dam raise project in the world using roller-compacted concrete and greatest single increase of water storage in history for San Diego, California.

Broomfield, Colo., July 6, 2009 – Construction is underway at the nation’s tallest dam raise which will help drought-stricken San Diego County respond to emergency water needs once complete. The July 9 groundbreaking ceremony at the City of San Diego’s San Vicente Dam marks the beginning of a three-year construction period to raise the existing 60-year-old, 220-foot-high concrete gravity dam by 117 feet and add 152,000 acre-feet of water storage – enough to help provide a six-month emergency water supply for the county, plus reserves for drought protection.

MWH, the wet infrastructure leader and global provider of environmental engineering services, performed the final design and engineering services for construction of the San Vicente Dam Raise Project through a $20.4 million contract from the San Diego County Water Authority (SDCWA). MWH engineers developed a roller-compacted concrete (RCC) design, making the San Vicente Dam raise project the tallest of its kind in the world using this proven and economical 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 AWWA and ASCE for its environmental stewardship, eliminating thousands of truck deliveries for concrete aggregates from off-site sources.

The dam raise is part of SDCWA’s $827 million, 10-year Emergency Storage Project (ESP) that increases the amount of water available for San Diego County residents in case of emergencies, such as droughts and major earthquakes. San Diego currently imports about 90 percent of its drinkable water supply from more than 400 miles away, making this a critical project.

"MWH is proud to be working with the San Diego County Water Authority and City of San Diego to deliver an effective solution to potential emergency or water storage issues that could impact the region and millions of residents," said Michael Rogers, MWH design manager for the San Vicente dam raise. "Our local design team delivered great expertise and efficiencies thanks to previous experience conducting projects for the San Diego County Water Authority, as well as securing design and construction approvals on more than 100 dams in California."

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 318-foot-high dam that added 24,000 acre-feet of reservoir storage as the first phase of the ESP. The San Vicente Dam Raise is the final ESP storage component.

After its expected completion in October 2012, the San Vicente Dam raise project will:

• Add 152,000 acre-feet of water storage, equivalent to more than 49 billion gallons of water – 52,000 acre-feet of which will be for emergency storage with the remainder for carry-over storage that’s used for prolonged periods of drought.
• Stand 337-foot high – or about 30 stories – making it one of the tallest structures in San Diego.

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 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.