A new, state-of-the-art dredge has been installed at Granite Reef Diversion Dam in northeast Mesa, Arizona, that will collect sand and silt that builds up at the dam every day and assist Arizona public power utility Salt River Project to efficiently and reliably deliver water to the Phoenix metro area.
When Granite Reef Diversion Dam was installed in 1908, material would float down from the Salt and Verde reservoirs and build up, eventually spilling into the canals. In response, a dredge was put into service in 1954 to help clean up the area in front of the dam and keep it clear of sediment.
The new dredge, which was installed using a 500-ton crane, is significantly larger than its predecessor, measuring 70 feet long by 20 feet wide and weighing approximately 130,000 pounds. The new dredge is also faster, completing in just a few hours what took the old dredge an entire week.
"A dredge features a large auger at the front that dips into the water to stir up material," explained Jeff Conyers, SRP Equipment Operator, Pump Maintenance. He has worked at Granite Reef for over 15 years, eight of which as a dredge operator. "An internal pump transfers the water and material through a pontoon line to the shore into a catch basin pit. It's like a giant vacuum cleaner."
Once the basin is full, a sand plant company extracts the material and separates it. That company then sells the sand and silt to businesses like Home Depot and other concrete companies.
The dredge has historically run on weekdays, but for the past two years, the productive winters of 2022 and 2023 brought in a lot of silt and sand into the reservoir system. This has required the dredge to operate seven days a week.
The new dredge boasts upgraded computer screens and joysticks, replacing the old handles and clutches.
While the old dredge needed extra time to warm up, the new one is ready in minutes and is three to four times more efficient. It also has GPS and a mapping system to show where dredging is still needed.
Unlike most U.S. cities, Greater Phoenix has access to four sources of water.
• Water from in-state rivers and streams – SRP manages seven reservoirs that store water from the Salt and Verde rivers and the East Clear Creek watershed. Over half of the water supply in the Phoenix metro area comes from the SRP water system.
• Colorado River water – The Central Arizona Project (CAP) delivers Colorado River water to the Valley. This represents the area's second-largest water supply.
• Reclaimed water – SRP delivers fresh water to cities and towns throughout the Valley. They then treat the water and deliver it to homes and businesses – but that’s just the beginning. “Waste water” gets a second useful life when it’s recaptured, treated and recycled. This recycled water – called reclaimed water – can be used for farming non-edible crops, landscaping and more.
• Groundwater – SRP utilizes a vast ground water pumping system that includes 270 high-capacity wells. Additionally, Valley cities operate large groundwater supply systems.
