The 100-million-gallon-per-day water treatment plant is the first to be built and owned by the SDCWA, which is a wholesale distributor of both treated and raw water to its 24 member agencies.
SDCWA awarded the design-build-operate $157 million contract to CH2M HILL in September 2005. The contract includes an annual operation and maintenance fee of $6 million per year. The DBO approach fast-tracked the project allowing concurrent design, procurement, construction and permit approvals to support a very tight construction timetable, saving SDCWA both time and money.
“After more than two years of intensive effort building this facility, it was exciting and rewarding to attend the plant’s opening. It was particularly timely that we held the facility’s grand opening during Drinking Water Week, when the world celebrates the importance of drinking water,” says Mark Lasswell, CH2M HILL President and Chief Group Executive, Civil Infrastructure. “The state-of-the-art submerged-membrane treatment technology applied at the facility and DBO delivery process used to construct the plant make the Twin Oaks facility one of our firm’s landmark projects. We’ll also remain a key member of the Twin Oaks Valley community as we operate this state-of-the-art facility for the next 15 years. My thanks to San Diego County Water Authority for allowing CH2M HILL be a part of this momentous project,” adds Lasswell.
SDCWA selected CH2M HILL’s water treatment plant concept that incorporated the submerged-membrane treatment process because it produces high-quality water, is less expensive than conventional processes, and is more environmentally friendly. The membrane option allowed for a smaller footprint, less concrete, fewer chemicals to store, and fewer solids to dispose of than traditional treatment methods.
The ZeeWeed submerged-membrane technology and equipment for the project was provided by GE Water & Process Technologies.
In addition to submerged-membrane filtration, other treatment processes in the plant include fine screening, ozonation for additional disinfection, ozonation with peroxide for taste and odor control, biologically active carbon contactors, chlorine addition, 15-mgd of treated water storage.
CH2M HILL OMI will operate and maintain the facility for the next 15 years, including providing 24-hour onsite staffing, chemicals, capital maintenance repair and replacement, membrane maintenance and replacement, residual solids disposal, and guaranteed maximum energy usage.
CH2M HILL has completed similar projects around the world including a 72-mgd submerged-membrane water treatment plant in Singapore, and the Regional Municipality of Peel in Toronto has commissioned a 95-mgd plant. Both use different pre- and post-treatment systems because of unique temperature and water quality conditions.