Malcolm Pirnie - Moving Toward Renewable Water Resources

Water Resources Management

SOLUTIONS FOR:

Projects

Moving Toward Renewable Water Resources

Client:	Tucson Water
Project:	Clearwater Renewable Resource Facility
Location:	Tucson, AZ

Issue

Historically, Tucson Water depended on local groundwater supplies as the only potable water resource for delivery to nearly 700,000 customers. As the metropolitan area grew, over-pumping of local groundwater was seriously depleting aquifer levels. An earlier attempt to introduce treated Colorado River water from the Central Arizona Project (CAP) into Tucson’s distribution system had caused significant “red water” problems, public outcry and passage of a local citizens’ initiative prohibiting direct delivery of filtered CAP water. The city initiated the Clearwater program to effectively use its largest renewable water supply, CAP water, to reduce its dependence on mined groundwater and provide residents with high-quality drinking water now and into the future.

Solution

Working with Tucson Water, the project team of Malcolm Pirnie and CH2M Hill developed an innovative design concept: strategic recovery of recharged CAP water blended with local groundwater in the aquifer, changing the blended water supply gradually over the coming decade from over 90% groundwater to approximately 50% Colorado River water.

The Clearwater Renewable Resource Facility is the largest CAP recharge facility in Arizona in terms of land area and the first that includes constructed facilities to recover all recharge credits, with a goal of recharging and recovering up to 60,000 acre-feet per year of CAP water. The project consists of approximately 350 acres of recharge basins, a CAP aqueduct turnout and 4 miles of raw water pipelines, a recovery wellfield and collector piping network, a recovered water reservoir and booster station and a recovered water transmission pipeline.

BenefitS

The successful project avoided abrupt water quality changes and has restored the utility’s credibility with customers. The full-scale recharge facilities replace a 60-acre pilot recharge project, completing an $80 million infrastructure program.