Central Arizona Project, the engineering marvel that delivers water throughout much of Arizona, held a behind-the-scenes tour this week to offer system stakeholders and members of the media a rare opportunity to descend into the temporarily empty canal for an up-close look at preventive maintenance on the Salt River Siphon.
The siphon is an 8,700-foot-long pipe, 21 feet in diameter, that runs as deep as 30 feet beneath a portion of the Salt River, carrying approximately 75 percent of all CAP water deliveries. The siphon sits approximately half-way along the length of the CAP system.
The siphon is responsible for a $90 billion contribution to the Arizona economy, according to CAP.
Gravity carries water through the siphon beneath the Salt River, and the water’s momentum takes it back to the surface as it flows to the Salt Gila Pumping Plant in Mesa.
Maintenance began Oct. 30, 2019 and included a partial recoating of the siphon to help protect against corrosion and erosion — the first recoating since 2001. Similar maintenance is expected to take place again in eight to 10 years.
CAP Board President Lisa Atkins said she thanked Salt River Project and the cities of Mesa, Gilbert, Chandler and Tucson for their assistance and collaboration in preparing for the partial service outage resulting from the maintenance project. Storage was maximized downstream from the Salt Gila Pumping Plant in preparation for the disruption.
“Without them working so closely with us — with CAP staff — on the planning phases of this project, today would not be possible,” Atkins said.
CAP General Manager Ted Cooke said planning for the six-week project began more than three years ago.
“It worked the way it was supposed to,” Cooke said of the steps taken to prepare customers and store enough water to avoid disrupting water delivery during the maintenance. Cooke said CAP’s contractors on the project worked round-the-clock in order to finish the project on schedule.
In addition to the Salt River Siphon, CAP maintains nine other siphons that run beneath the Agua Fria, New, Gila and Santa Cruz rivers.
With Salt River Siphon maintenance complete, regular water deliveries resumed Wednesday.