BE Magazine Volume 5, Issue 2 - (Page 39) PLANT (CDM) to design a low-pressure reverse osmosis (LPRO) water treatment process that will operate in conjunction with the existing lime-softening water treatment process. The LPRO process will rely exclusively on the high-yield Upper Floridian Aquifer, which can provide a long-term water supply. Blending water treated with the two processes will increase the plant’s operational flexibility. In addition, when the maintenance burden associated with operating the lime-softening treatment plant becomes a financial and reliability risk, the city can phase out that process completely. This transition will ultimately conserve the fresh water supply in the surficial aquifer and minimize environmental impacts to wetlands adjacent to the local wells. CDM began design of the $11 million LPRO plant in June 2006 and issued permitting drawings in February 2007. The aggressive BE Award Finalist Purifying Brackish Water Transition to high-yield alternative water supply preserves fresh-water aquifer T he historic city of St. Augustine, Fla., has relied on a surficial aquifer as the primary source of water for its 12,000 residents. Concerns about the city’s future water supply and the impact of aquifer drawdown on wetlands in this coastal community led the city to develop a proactive plan for long-term water resource management. The plan calls for tapping brackish water from the Upper Floridian Aquifer as an alternative source. St. Augustine commissioned its existing water treatment plant in the 1920s and last modified it in 1987. The plant draws water from 10 shallow aquifer wells and four deep aquifer wells. The raw water is blended and treated in a reactor-clarifier for lime softening, a sedimentation basin for solids settlement and recarbonation, dual-media rapid sand filtration for solids removal, and gravity sludge thickener for sludge treatment. v Camp Dresser & McKee’s master 3D model enabled numerous iterations, multiple design reviews, cross checks from other disciplines, and interference detection schedule notwithstanding, CDM developed a costeffective design with future expansion capabilities while providing an aesthetically pleasing facility that met the requirements of the St. Augustine’s Historic Architectural Review Board (HARB). Efficient workflow enhances design The lime-softening process relies on a ready supply of fresh water from the local surficial aquifer. However, the supply is expected to be insufficient to meet the long-term needs of the growing population and tourism industry. The alternative is to draw more water from the deep wells, in which the ample supply is laden with salt and other minerals. With an aging plant nearing the end of its service life, the city capitalized on an opportunity to implement improvements that would address both the water supply issue and the infrastructure management issue. The city retained Camp Dresser & McKee Using the AutoPLANT suite and the ProjectWise collaboration server system enabled 22 technical staff members across multiple offices to work on the project simultaneously. “For CDM, using Bentley’s suite of software—built on providing 3D design and the associated data—is based on the simple principle of providing our clients with a superior and more costeffective project solution,” said CDM Vice President William Nelson. “We’re utilizing state-of-the-art technology in intelligent plant design.” On past projects with a multidiscipline team the 2D approach to producing deliverables proved ineffective at addressing the continuous design iterations during the detail design phase. Bentley’s 3D technology, however, improved CDM’s ability to Volume 5, Issue 2 | BE MAGAZINE 39
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