To reduce reliance on groundwater, Tucson planned to use Central Arizona Project (CAP) surface water from the Colorado River after filtration and disinfection at the Hayden-Udall water treatment plant (HUWTP). However, adding the treated surface water supply directly to the distribution system caused unanticipated changes in water’s chemical and microbiological characteristics, physical pipe environment, and system hydraulics, and resulted in thousands of customer complaints about water quality, and stopped direct delivery of CAP water in 1994.

To address this problem, we conducted corrosion control studies and extensive evaluations of consumer acceptance, worked with Tucson Water to publish water quality data and update consumers on water quality changes. We then designed and constructed the Central Avra Valley Storage and Recovery Project (CAVSARP) or Clearwater Renewable Resource Facility, including 350 acres of recharge basins, a raw-water pipeline, recovery wellfield, and pipeline to convey recovered water to HUWTP for disinfection and introduction to the City’s potable water system. Recovering a blend of native groundwater and recharged CAP water, the project provides a gradual transition in recharged water quality, avoiding distribution system impacts from abrupt water quality changes. With construction costs $4 million less than originally projected, the Clearwater Facility provides assured capacity of 60,000 acre-feet per year and with additional extraction well capacity up to 80,000 af/yr of supply.