McCarthy Building Companies Inc., one of the nation’s largest commercial construction companies and a leading water treatment facility builder, recently began construction of the Initial Expansion of the Groundwater Replenishment System (GWRS) for the Orange County Water District (OCWD), which manages the large ground water basin that underlies north and central Orange County that provides most of the water for about 2.4 million citizens. Located at the OCWD Advanced Water Purification Facility (AWPF) on Ward Street in Fountain Valley, Calif., the $142.7 million project will create an additional 31,000 acre-feet per year (AFY) of new water supplies to serve north and central Orange County. Once completed, the AWFP’s total production will reach 103,000 AFY, enough water for 850,000 people.

A formal groundbreaking event with local, county and state elected officials, water retail agencies and representatives from the design firm and construction team was held on Jan. 17, marking the start of the project.

“The GWRS established the benchmark for international water projects and water reuse technology,” says OCWD general manager, Mike Markus. “Most importantly, the GWRS has provided a reliable, locally controlled source of water for Orange County during a time when the availability of imported water is decreasing, while its cost is increasing. We live in a naturally arid region. The GWRS Expansion will provide us with the water supply reliability that we need, while creating hundreds of local jobs that will benefit Orange County’s economy through the development, construction and operation of the project. In short, it’s the perfect project at the perfect time.”

The GWRS, a joint project of OCWD and Orange County Sanitation District (OCSD), takes highly treated wastewater that normally would have been discharged into the Pacific Ocean and purifies it through a three-step process that includes microfiltration, reverse osmosis and ultraviolet light with hydrogen peroxide. Thirty-five million gallons of near-distilled quality GWRS water per day are pumped into injection wells where they serve as a seawater intrusion barrier. Another 35 million gallons per day are pumped in a 13-mile long pipe to OCWD recharge basins in Anaheim, Calif. The GWRS water then filters through sand and gravel to replenish the deep aquifers of Orange County’s ground water basin, and ultimately becomes part of the drinking water supply.

Serving as general contractor for the expansion, McCarthy will construct a 30-million-gallon-per-day (MGD) treatment facility, expanding the 70 MGD GWRS that was completed in 2008.  Parsons of Pasadena is construction manager for the project, and Black and Veatch of Irvine is the structural, civil, electrical and mechanical engineer.

The project entails expansion of the existing microfiltration facility by constructing eight new below-grade treatment basins and enlarging the existing basement facility. Other work includes construction of a new 32,000-square-foot reverse-osmosis building, the installation of five new ultraviolet light (UV) treatment trains to match the existing systems, as well as retrofitting the existing post-treatment systems to employ a new lime-feed system. McCarthy also will construct two aboveground steel tanks; each is 215 feet in diameter with a height of 35 feet and a capacity to hold 7.5 million gallons of water.

“The project will be carefully executed in order to mitigate any disruptions to the existing plant while conducting a complex facility expansion with significant construction challenges,” says McCarthy project manager, Curtis Horner. “The microfiltration facility is a very complicated water-bearing structure tucked into an extremely tight footprint. This 30-foot deep structure is bordered on all four sides just beyond the limits of construction by existing structures and piping. The excavations and concrete durations alone will take approximately 14 months to complete.”

The reverse-osmosis (RO) building also provides project challenges, explains Horner. “The RO facility is located in an area bordered by the existing facility, a substation, a pumping area and another building. Furthermore, the structure will sit on more than 200 piles with a long, extensive concrete scope, followed by extensive mechanical work.”

The GWRS is the largest advanced water treatment facility of its kind in the world, and has garnered more than 35 regional, state and international awards, including the prestigious American Society of Civil Engineers (ASCE) 2009 Outstanding Civil Engineering Achievement Award for the year’s most outstanding national engineering project, and the Stockholm 2008 Industry Award for the year’s most outstanding international water project.

“We are proud to be a part of this complex and vital project to mitigate the challenges associated with an otherwise dwindling water supply in Orange County,” says Mark Mardock, McCarthy executive vice president. It’s exciting to not only  be involved with an internationally renowned project, but also helping to provide a environmentally responsible, reliable and safe source of water, which is critical to the public health and economy of Orange County.”

Construction work is scheduled to complete in September 2014.