By Paul Scott Abbott, AJOT

On Alaska’s North Slope, often more than 100 miles beyond the nearest gravel road, a special breed of all-terrain vehicles transports heavy loads to remote oil exploration sites without damaging the fragile ecosystem.

These aren’t anywhere akin to the kind of ATV that youths take on trail rides. These units, rolling along tundra on a contingent of as many as 14 smooth-tread airbag tires, weigh as much as 25 tons each and can carry payloads of more than 42 tons.

Deployed by the Crowley Alaska Inc. unit of Crowley Maritime Corp., these ATVs are commonly referred to as CATCOs, short for the name of the subsidiary formerly known as Crowley All Terrain Corp.

‘They truly are an amazing piece of equipment, they really are,’ said Michael O’Shea, director of business development for the Anchorage-based Crowley division that operates the CATCO vehicles. ‘Any time you can move 85,000 pounds of cargo over tundra without damaging it, I’d say that’s amazing.’

Crowley has been operating the CATCOs for more than 30 years, but, according to O’Shea, they have drawn little popular attention ’ perhaps because the area in which they run is so remote.

Not only remote, but cold. The day the American Journal of Transportation reached O’Shea by phone outside Prudhoe Bay, the temperature was 30 degrees below zero with wind-chill factor. That day, CATCOs were transporting oil exploration equipment 178 miles beyond the last gravel road at Prudhoe Bay.

The fleet of 20 CATCO ATVs includes six of the largest units, which are tractor-trailer combinations with 14 airbag tires, as well as four units with 12 airbag tires. Both of these models feature 16-by-40-foot cargo decks, according to O’Shea. The remaining 10 CATCOs each have eight airbag tires and have cargo decks that are 16 feet wide and 12.5 feet long.

Built for Crowley by Bechtel Corp., the CATCOs have aluminum structural components that minimize weight and maximize operability in extreme cold.

The airbag tires are driven by dry rollers that rest atop them with pivoted yoke arms, while the flexibility of the tires helps them mold to irregularities of terrain while distributing weight over a large ground area with minimal pressure. Each tire is 54 inches in diameter and 68 inches in width. The air pressure in each tire can be adjusted by the operator in the cab while the unit is in operation.

Each tire costs $5,500 to replace, and, while the CATCOs now in use were built decades ago, the cost to build an entire CATCO ATV today would be more than $1 million, according to O’Shea.

CATCOs’ unique capabilities have enabled such units to be used in sandy Middle East deserts in addition to Alaskan tundra, O’Shea noted.

Customers in Alaska include major oil companies as well as smaller independent energy firms that are entering the market as areas such as the Arctic National Wildlife Refuge (ANWR) are beginning to be opened up for exploration. Various state and federal government entities also have been customers.

When duty takes CATCOs to federal lands, Bureau of Land Management officials first go out across the intended route in one of the smaller ATV units with thermal ice probes to check the status of the tundra and underlying permafrost.

CATCOs not only are used for transporting entire drilling complexes, including rigs, they also transport water, drilling mud, casing and fuel to existing sites. In addition, they have been used to build and maintain ice roads and ice islands, to assist in emergency responses to remote areas and to provide support for engineers performing geotechnical functions with ice drills.

Because of the scope of such projects, a typical move of a rig and accompanying camp may require between 110 and 130 CATCO loads, O’Shea said.

While their top speed is about 17 miles per hour, that would be on a gravel road, according to O’Shea. More typically, the CATCOs move at 10 mph on tundra, slowing to perhaps six mph when transporting a heavy load.

CATCO operators, many of who