With a population of more than 1.4 million, Phoenix, Ariz., is currently one of the fastest-growing cities in the U.S. When the city decided to construct a new water treatment plant in the early 1990s, government officials needed to plan accordingly. An explosive growth rate, coupled with increasingly stringent potable water regulations, presented the city with a major challenge in providing reliable, high-quality drinking water to its residents.
Construction of the Lake Pleasant Water Treatment Plant (WTP) began after a careful consideration of various design and construction approaches. These included: traditional design-bid-build, with city personnel operating the plant; design-build, also with city personnel operating the plant; and design-build-operate (DBO), a relatively modern delivery method, whereby a third party operates the plant and is involved throughout the design and construction phases.
“The traditional U.S. approach is for a utility to have a plant’s designs made by a consultant and then to hand construction responsibility to the contractor bidding the lowest price,” said Mike Gritzuk, director of the Phoenix Water Services Department.
City officials eventually selected the DBO method for three primary reasons: it allowed construction to begin during the design phase, resulting in a faster delivery process; it projected significant whole life savings when compared to traditional delivery methods; and it maximized the potential for innovative thinking, due to all parties, including the operator, being involved in the layout and design.
“We looked at various project delivery methods very, very extensively,” Gritzuk explained.
After a lengthy, multi-phase procurement process, Phoenix’s Water Services Department awarded American Water the DBO contract. American Water serves as the prime contractor and operator for the first 15 years, with a continuance option for an additional five years subject to city approval.
The raw water source for the Lake Pleasant WTP is the Central Arizona Project’s Waddell Canal. The ultimate planned build-out capacity of the facility is 320 mgd, with the first 80-mgd phase being designed/constructed under this contract. Construction of the first 80-mgd facility began in June 2004 after the detailed design and permitting phase. The facility has been designed to meet the city’s “enhanced water quality standards” and incorporates a unique combination of advanced processes not typically applied in a single facility in North America:
- Chlorine Dioxide for oxidation of natural organic matter and manganese;
- High Rate Actiflo for solids separation and TOC removal;
- Ozone for oxidation of DBP precursors, geosmin, MIB and viruses;
- Deep Bed Filtration for removal of turbidity and biological removal of DBP precursors;
- GAC Contractors for absorption of DBP precursors, Geosmin and MIB;
- UV for Giardia and Cryptosporidium inactivation; and
- Chlorine for Giardia and virus inactivation.
In addition to the 80-mgd treatment plant, 320-mgd intake, 160-mgd raw water pumping station, 2-mile 90-in. diam. raw water pipeline, chemical handling facilities, 40-million gal storage reservoir and full residuals handling/processing facilities, a GAC Regeneration Plant and operations building are being constructed on the 225 acres of desert land. When fully operational, the entire facility will serve approximately 400,000 households.
The desert location of the Lake Pleasant WTP demanded an innovative, yet environmentally sensitive approach to water treatment. American Water and its partners recognized this challenge and have constructed the plant in an architectural style that blends naturally with the desert landscape.
As of December 2005, all design and permitting for the Lake Pleasant WTP is complete, with construction being 70% complete.
Additionally, all major engineering equipment has been procured with only minor subcontract packages to be let. Construction work on the canal intake is nearing completion, and the 69 KV electrical substations, which will supply power to the treatment facility, are now energized. The entire facility is scheduled for start-up in late fall 2006.
To date, the project, which is the largest DBO water project in North America, is meeting all of the city’s requirements regarding expedited delivery, low whole life costs, low risks of litigation and maximum technical innovation.
According to Carlos Padilla, assistant water services director for the city of Phoenix, “The commitment to partnering by all parties has made this critical project a real success to date.”
Total cost of the design and build component of the contract is $227 million, while the 15-year operating contract is valued at approximately $109 million, depending on demand. With major civil/structural construction work nearing completion, mechanical/electrical construction activity will peak over the next nine months. Planning and documentation is well under way for the commissioning, functional testing, start-up and acceptance testing period, which runs May through December of 2006.