Inside Caterpillar's Arizona Proving Grounds

As we approached Caterpillar's proving grounds outside Tucson, Ariz., we expected to see big yellow iron, but the sign on the gravel road read, "Caution: Desert Tortoise and Reptile Crossings."

We did find a small rattlesnake, but we weren't here to take in nature. We were here to see construction equipment manufacturer Caterpillar's Tinaja Hills Demonstration & Learning Center located deep in the Sonoran Desert. The 6,500-acre site covers a remote area of land south of Tucson along Interstate 19. For those of us who bleed yellow, it is hallowed ground.

Finding your way to this part of Arizona can be tricky, though, and if you reach Nogales, Mexico, you've gone too far. The highway signs along this stretch of I-19 offer directions in kilometers per hour, a holdover from Arizona's unsuccessful push long ago to go metric. Undeterred by the confusing roadside markers and equipped with an old-fashioned paper map courtesy of Caterpillar — it instructs would-be visitors to do things such as "turn left after metal pipe over road" — we recently visited to test-drive Cat's 789D mining truck for PickupTrucks.com.

Based in Peoria, Ill., Caterpillar uses about half of this vast facility for training technicians and operators from all over the world. Last year, Tinaja Hills hosted around 10,000 people looking to become certified in a piece of Caterpillar equipment, learn the latest maintenance practices or even discover tricks to make their machines operate more efficiently.

"Operator training is, by far, the biggest thing we do," said Jim Deputy, the facility manager and our tour guide. Don't think about coming here to take a machinery exam unless you already have experience, he said, adding that professional operators typically have at least eight to 10 years in the seat before they try to get certified. The cost to do so is about $1,200 for each Caterpillar machine family.

"When you come back for certification, we expect you to know the machines," Deputy said.

The other half of the Tinaja Hills property is Cat's proving grounds for large mining equipment. Caterpillar has four main locations it uses for training and testing. In addition to Tinaja Hills, it operates facilities in Illinois, Spain and Panama. In Arizona it employs about 25 people on the marketing side and 300 people on the research-and-development side.

We weren't allowed access the proving grounds — that area includes an active copper mine — because engineers were testing autonomous haul trucks and bulldozers, we were told. But we did come close to the entrance as we drove to the top of a man-made mountain only to find the biggest machine that Caterpillar makes — the Cat 7495 electric rope shovel — waiting at the summit.

"It's for sale," said Deputy, for only $36 million. The nearly 3-million-pound machine can scoop up 110 tons of rock at a time and load Cat's largest mining truck, a 400-ton model 797, in four passes. Seeing the gentle giant sitting there idle was a sobering reminder that the mining industry was — and still is — experiencing a slow period that has Caterpillar forecasting revenue sliding 9 percent this year to $50 billion.

We ventured into demonstration arenas, where Caterpillar shows how its machines work in various scenarios, such as digging, backfilling and grading. About 72 machines representing much of the Caterpillar product line are put to work here.

As we toured the huge property, a water truck regularly sprayed down the dirt road to keep dust in check. The facility maintains an active well mated to a 465,000-gallon water tank for dust suppression. Tinaja Hills is powered by Caterpillar diesel generators and is mostly self-sustaining, Deputy said.

Near a service shop is what looked like a truck-stop fueling station, but this was for heavy equipment exclusively. A 20,000-gallon diesel tank and 800-gallon diesel exhaust fluid tank supplied the necessary reserves to the thirsty earth-moving machines.

In addition to housing big iron, Tinaja Hills also runs a fleet of nearly a dozen pickup trucks — they are all crew cabs — used to shuttle visitors and gear from place to place. With all the rocky roads, truck tires take a heavy beating. Deputy said he recently switched to Goodyears with Kevlar for added protection.

"This is pretty rough terrain," Deputy explained. "These trucks really never see asphalt or highways, so we do go through a lot of tires."

Cars.com photos by Tudor Van Hampton

The hacienda at Caterpillar's Tinaja Hills training and testing facility houses offices, classrooms, a cafeteria and a gift shop.

About half of the 6,500-acre site is used for training and demonstrations, while the rest is a proving grounds for Caterpillar mining equipment.

A material-handler operator sorts rock.

Roads are impeccably maintained but tough on tires. The facility's pickup-truck fleet runs on Goodyears with Kevlar for added durability.

Water is sprayed frequently to keep dust down.

A Cat D7E, an innovative bulldozer with a diesel-electric powertrain, takes a rest.

Trainees from South America learn to service mining trucks in a shop setting.

A fueling station holds 20,000 gallons of diesel and 800 gallons of diesel exhaust fluid.

A giant cable-rope shovel, worth about $36 million, takes a nap.

The road to the proving grounds. The top-secret area includes an active copper mine and is currently testing autonomous mining trucks and bulldozers.

Watch out for rattlers and other vermin at the remote facility, which is deep inside the Sonoran Desert.