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In a desert environment, natural groundwater replenishment typically cannot keep pace with extraction rates. Such is the case in Arizona’s West Valley, a growing—and thirsting—area of Maricopa County west of Phoenix. Underground water levels here have been dropping for years, leaving communities up against a stressed supply and rising pumping costs.
The Central Arizona Project (CAP) has set out to address the region’s water supply challenges via a 336-mile-long system of aqueducts, tunnels, pumping plants and pipelines that deliver Colorado River water to municipal and agricultural customers. Today this system serves as the state’s largest renewable water supply resource. When WESTCAPS, a planning group comprised of West Valley water providers, pooled data and growth projections to establish its 2001 Strategic Plan, members determined that they needed to reduce their reliance on groundwater and begin tapping the CAP supply.
To execute this strategy, utility provider Arizona American Water purchased land in 2002 and commenced construction of the White Tanks Regional Water Treatment Facility (WTF), a central plant designed to provide a sustainable supply of high-quality river water to more than 100,000 customers in Surprise, Waddell, Verrado and unincorporated areas of Maricopa County. Colorado River water, naturally renewed by rain and snow that falls high in the Rocky Mountains, is diverted into the CAP canal at Lake Havasu. The water travels on to the Maricopa Water District’s Beardsley Canal, which delivers it to the White Tanks Regional WTP.
Once it reaches the 13.4-million-gal-per-day (mgd) WTF, raw water is stored in onsite storage basins and pumped out for primary treatment. The primary treatment process clarifies the water using coagulation/flocculation with ferric iron coagulants as well as dissolved-air flotation (DAF). (The use of DAF for clarification here was a first for the state of Arizona, according to Arizona American Water Construction Manager Edward Radwanski, P.E., PLS.) Granular activated carbon and sand filtration processes follow. Then, ultraviolet light and chlorine are introduced to disinfect the water. All the while, central and remote SCADA HMI terminals assist operations staff in monitoring the treatment process.
An onsite reservoir stores the finished product, which eventually is transferred to the Agua Fria District water plants that will deliver it to customers. The facility’s finished water distribution pumps are capable of pumping up to 20 mgd.
Radwanski credits White Tanks Regional WTF’s innovation and success to the collaboration between contractor Garney Construction, designer Black & Veatch Corp. and owner Arizona American Water Co. The new facility was completed on time and with minimal startup issues, he said.
Save to Sustain
“Anyone native to the Phoenix area knows it can go months without any precipitation at all. As groundwater supplies diminish, the need for renewable water supplies continues to increase,” said Joseph G. Cornejo, operations supervisor for Arizona American Water Co. “Many utilities and municipalities in the valley still rely solely on groundwater as their primary water supply. In constructing the White Tanks WTF, Arizona American Water Co. has joined the increased effort to utilize a renewable water source.”
By treating CAP water, the WTF will alleviate demand on groundwater supplies, improve community aquifer levels and reduce pumping requirements—key to maintaining affordable service, as related energy savings have largely offset new treatment costs. The facility keeps more than 3 billion gal of water in the ground annually, and with future expansions that number could jump to 30 billion. In addition to helping stabilize the water table, these savings will protect desert plants’ and animals’ habitat. The saved water also supports Arizona’s goal of achieving safe yield, that is aquifer withdrawals not exceeding the amount of water put back in, by 2025.
White Tanks Regional WTF became operational in November 2009. In April 2010, Arizona American Water President Paul Townsley and Arizona Department of Environmental Quality Director Ben Grumbles, both members of the Governor’s Blue Ribbon Panel on Water Sustainability, led its grand opening celebration.
“Groundwater is Arizona’s most precious liquid asset, and it is very underappreciated,” Grumbles said at the event. “Today is a day that celebrates sustainability that will turn into billions of gallons of groundwater saved for the West Valley.”