Articulated dump trucks have become the standard hauling vehicles at most landfills because their unique design gives them the performance and flexibility needed for landfill operations. And new developments seem likely to extend their utility there.

By Charles D. Bader

When Volvo first introduced the articulated dump truck (ADT) in Europe in the mid-1960s, it was an entirely new concept. With its unique ability to move off-road through practically any terrain and its superior maneuverability for loading and unloading in the most difficult locations, the "artic," as it came to be known, changed the way many companies work.

"We could see that the inherent design of the artic was ideal for landfill operations," relates Buddy Goodman, Volvo's United States product marketing manager for articulated haulers, based in Asheville, NC. "So immediately when the company introduced artics into the US, we aggressively marketed them to the waste industry in general and landfill applications in particular. And very soon the artic became the dominant hauling vehicle at most landfills and continues in that position today.

"The articulated hauler's strong market position is based on its ability to optimize the equation between load-carrying capability and transport speed under the various terrain and underfoot conditions encountered in and around landfills. An artic has great load-carrying capability for its weight, and the body is wide and open to facilitate loading from excavators and wheel loaders. And thanks to their unique maneuverability, these trucks are also well suited for loading from fixed loading facilities. Also, as every landfill operator knows, a hauling truck standing still is an inefficient machine. Therefore, the artic body design is based on the principle that loading and dumping should take place in the shortest possible time."

And under the right conditions, the use of ADTs can accomplish an amazing amount of work in a very short time. Dan Oakes, president of A.W. Oakes & Son in Racine, WI, cites one job where, in just three months, his excavating company had to move 500,000 yd.³ of clay out of a landfill site and stockpile it on a farm 1.5 mi. away. "We had two backhoes loading 15 artics, each of which would haul the clay to the stockpile and return for additional loads throughout each day," he recalls. "Those 40-ton artics were running around like bumblebees, and that fleet moved an average of 12,000 yards a day. On our best day, we actually moved 18,000 yards, so within the three-month deadline, we had excavated that new cell and stockpiled all that clay for future use."

A.W. Oakes is a large excavating company that specializes in landfill work - but not in daily-cover operations. Yet Oakes is equally enthusiastic about the fleet of 40-ton Caterpillar and Volvo ADTs he uses for big jobs and the new Case 25-ton and 30-ton trucks he uses on smaller jobs or in softer underfoot areas. "We work on three to five landfill projects each year," he says, "and we use artics in all of these projects, even cell construction projects, which include subgrading, mass excavation, laying the sub-base, installing the granular drainage liners, and laying the pipes for leachate control. About the only thing we don't do in the construction of a new landfill or landfill cell is to install the plastic liner. We also do capping and closure projects, but we only lay daily cover if we're on-site, perhaps building a new cell. In those cases we have artics on-site, so they are readily available to lay the daily cover on the active cell."

On a more modest scale, Dennis Gehle, site manager for Allied's 1,150-tpd County Environmental–Wyandott Landfill in Carey, OH, reports that his single 30-ton Komatsu ADT, loaded by a Hitachi EX 330 excavator, routinely takes 17-20 loads of dirt from a borrow area and dumps them right at the landfill work face for use as daily cover.

"Usually it's a one-man operation," Gehle states. "The driver gets out of the Komatsu artic, loads it himself with the Hitachi excavator, and then makes his run to the landfill. In our relatively small landfill, it's not beneficial to have a dedicated excavator operator sitting around waiting for the artic to come back for the next load. Even with this one-man operation, though, it takes that driver less than six hours to make those 17 to 20 runs. The rest of the time, we divert him and his artic to jobs for the hauling company we own. And of course we have plenty of work for that man who isn't required to operate the excavator except in very bad weather. All in all it's a very productive operation. It has to be because we only have a four-man crew to handle all the daily operations of this landfill."

Although unusual, this use of an ADT points out the flexibility of the vehicle. And flexibility is a key attribute needed in landfill operations. Dwain Wiseman, landfill operations manager for Keifer Landfill in Sloughhouse, CA, flatly states: "Since they are so easily top-loaded, our Cat 730 artics give us the flexibility to move all kinds of material and take it to where we most need it. I can pick up virtually anything, from greenwaste to large chunks of rubble, and I can dump dirt for landfill cover on sideslopes or a flat-top deck. It's particularly efficient for our operations when we excavate dirt from a borrow with either our Cat 330 excavator or our Cat 980 front-end loader; we truck it either to the daily cell, usually a third of a mile away, or to a stockpile, usually within 100 yards of the active working face, where it will be handy for daily-cover operations in bad weather."

Conversely, Bill Minor, Waste Management's heavy-equipment manager based in Lombard, IL, says his company seldom does its own cell construction any more. Even so, they have found a variety of uses for ADTs over and above hauling and stockpiling daily cover and opening new cells. "For example, we use them for handling industrial sludge in some locations where the landfill is permitted to accept it. First, we place the sludge and fly ash or sawdust in an excavator, which mixes them. Then we load the solidified sludge into the artic, which then trucks it to the working face where it is commingled with the MSW. We also use artics at landfills that have composting operations. After the greenwaste has been shredded, an artic hauls it out and dumps it to build the initial windrows. The artic is just an all-around versatile hauling tool around any landfill."

Replacing Scrapers

The standard vehicle for laying daily cover in landfills used to be the scraper. However, according to Wes Lee, Case Construction's director of marketing for heavy range products, "The market for self-propelled scrapers has been flat for the past few years, while the sales-trend line for articulated dump trucks has been going up every year. Sales of off-highway articulated trucks in North America jumped nearly 300% from 1993 to 1998. Today only Caterpillar and Terex make heavy-duty scrapers."

Scrapers utilize a bottom-loading methodology best suited for cohesive material that can be peeled out in layers; therefore scrapers are very successful in removing topsoil and performing pioneering work. And, as Caterpillar points out on its Web site, "The ability of Cat wheeled tractor scrapers to cut, haul and unload in one cycle makes them efficient on short hauls. A wheeled tractor scraper is well suited for climbing steep grades out of a landfill cell and for traversing poor underfoot clay, sand and moist soil terrain. The wheeled tractor scraper will cut and load a wide variety of materials, a useful characteristic when cell construction encounters a sand, soil or clay seam. Caterpillar scrapers load quickly, have high travel speeds, and compact as they dump and spread on the run."

Wiseman agrees - to a point. "We use scrapers for special situations," he explains. "For example, if I am building a dirt stockpile for winter daily-cover operations, a scraper is more efficient in moving quantities so that I can move more material faster, plus the fact that scrapers can build a path to drop their loads on the pile. Also, we use scrapers to cover daylighting. Since a scraper can lay loads in layers as little as 6 inches, it can efficiently cover exposed waste on the working face. While we have twice as many artics, we will always have a need for a scraper."

But at what cost? And, he reminds us, the disparity will be reflected in lease costs as well since, as Lee points out, a scraper with the same cubic-yard capacity as an articulated truck costs nearly twice as much to purchase and has higher depreciation costs (the depreciation schedule of the two different products will probably be the same number of years).

"Our experience has been that it is far more expensive to own a scraper-and-tractor combination than it is to own an artic-and-excavator combination," relates Minor. "For one thing, the maintenance of the undercarriage will be far greater; there will be hardly any undercarriage maintenance costs with an artic. Moreover, an artic burns 40% to 50% less fuel than a twin-engine scraper." Minor's estimates appear to be well founded. In a study conducted by Govi Kannon of Volvo, it was found that the total hourly cost of an ADT is less than just the hourly operating cost of a scraper.

For most operators, flexibility is as major a consideration as cost in preferring artics to scrapers. For example, Kannon points out, "A scraper typically takes up to three times its length to load, a distance of 100 to 150 feet. Articulated haulers, on the other hand, are not constrained by space. Thanks to top-loading methodology, articulated haulers can be ideally placed for loading by an excavator in most space-starved corners."

Also, longer haul distances increase the disparity between the two types of haul vehicles. Kannon calculates that scrapers represent an economical way of moving dirt for up to 1,500 ft. - all other things being equal. But of course they rarely will be equal. How often is the material going to remain good dirt capable of being loaded by scrapers? Will there be sufficient space for a scraper to load and dump? Will adverse weather affect the job? Answers to these questions will begin to tilt the balance toward artics.

Even disregarding these important operational considerations, longer haul distances will inexorably favor the artic over the scraper. Kannon notes, "Beyond 2,500 feet, the articulated haulers become much more economical compared to the scrapers," adding that, as the haul distances increase, "the proportion of the haul and return times become substantially more than the load time. It also allows the articulated haulers to accelerate to their top speed and maintain that speed over a longer distance. In addition, the higher cost of the scraper is no longer offset by the production."

There certainly are niches where a scraper is a good investment, particularly for short hauls involving shallow cut-to-fill operations. The reason behind the fleetwide preference for artics, however, is the fact that they are economical and useful for a wide range of applications. Moreover, they remain flexible and versatile even under adverse and difficult conditions.

New Articulated Hauler Designs

While enjoying the long-standing popularity of artics among landfill operators, the industry appears to concentrate on just tweaking the design of its models year after year, relying on existing technology and focusing on adding features that add incrementally to comfort and productivity. There are a few exceptions to this pattern, though - most notably Volvo's Container artic and Caterpillar's Ejector artic.

The container hauler is designed to support rail delivery of containerized waste by transferring 20-ft.-long ISO containers from the railhead adjacent to a landfill, hauling it into the landfill, releasing the rear panel of the container, and then dumping its trash at the face. "We designed this unit for Atlantic Waste Disposal in Waverly, Virginia, because they were converting to rail delivery of trash from New York," Goodman relates. "We converted one of our 35-ton artics for testing by removing the dump bed and replacing it with a container frame system we had designed for the purpose. We pinned the container on using twist locks and added a control in the cab so that, without leaving the cab, the driver can release the container's back panel for dumping. Atlantic tested it for 45 days, decided they liked it, and ordered three more production [our A35D] models."

Atlantic moved that quickly because it was facing a delivery schedule of as many as 60 containers a day arriving at its siding. To accept these containers, Atlantic had to lift them off the rail flatbed with a four-wheel stacker and place them on a tractor-trailer, which hauled the load over a mile of unimproved road to the landfill working face. Then they manually dumped the load and returned to the siding. The process was taking as much as 45 minutes per round trip, recalls Billy Furcron, Atlantic's intermodal manager, "and it was eating us alive."

"Now we lift the container off the railcar with a crane that lifts it onto the A35D bed. Tie-down is quick and easy with the truck's self-aligning guide plates and twist locks. With its greater ground clearance, the artic can move quickly into the landfill, and with its rear-view visibility and dumping mechanism, it can back in close to the face. Then the driver just activates the switch to release the back panel of the container and uses his dump lever to dump the load as with any artic. The entire process, including loading, dumping, and round-trip travel, now takes only eight minutes, so those four A35Ds have greatly increased our productivity."

Caterpillar has introduced an artic that features a self-cleaning ejector mechanism that pushes material out the back of the truck, thereby allowing material to be spread and dumped on the go, without raising the body. Rated at 42 tons, the 740 Ejector articulated truck incorporates all the features of Cat's 740 articulated truck, including a new electronically controlled engine and transmission, plus a new suspension system, hitch design, rear-mounted cooling system, and center-mounted cab. The bodies of the two 740 truck models are not interchangeable, however.

According to Caterpillar's Allan Osborne, "The load-ejection concept delivers many benefits. Material can be spread while the truck is moving to cut cycle time, decrease power-train loads, and reduce the amount of support equipment needed for spreading and dozing. The ejector also prevents material from adhering to the inside of the truck body after the dump, so payload can be maximized, thereby improving productivity, reducing fuel consumption, and lowering cost per ton. Also, ejecting a load without raising the body increases stability, so the truck can work on inclines and sideslopes and in very soft underfoot."

Osborne estimates that about 100 of the ejector artics have been sold in the US, primarily in Florida where they work in a very soft underfoot. A number of different landfill operators are evaluating the system for use in landfill operations without making significant purchases yet. Typical of these is Ryan Incorporated Central, headquartered in Janesville, WI. The large excavation contractor does a considerable amount of landfill work, and Ryan's George Kibble regards the ejector truck as a terrific concept. "We tried a D400E ejector truck early on and it seemed to work fine under normal conditions. Our only concern is how well it will operate in winter if the material is wet, slimy, or partially frozen. We're due to test a 740 Ejector artic soon, and we'll find out how it works under adverse conditions."

Jim Griffith, site supervisor of the Monterey Regional Waste Management District in central California, has no doubts. "We use our 740 Ejector for almost everything," he enthuses. "We use it for such diverse tasks as hauling and spreading daily cover and picking up a wide range of materials, including concrete, asphalt chunks, and compost. Our landfill site includes a dirty [materials recovery facility], and we handle [construction and demolition] materials, recycle asphalt and concrete, and even haul sand out of future landfill modules and sell it. That's why the versatility of the ejector artic is so important here. It's done every job we've asked it to and done it better than we expected. Bottom line, it's made a world of difference for us."

An interesting development that might significantly affect the ADT industry is the recent entrance of Komatsu into this business. The Japanese heavy-equipment giant's only participation had been limited for years by its agreement to market Moxy artics. When that agreement was terminated, Komatsu was completely out of the artic market for about two years. That time wasn't wasted though, as Komatsu designed articulated trucks from the ground up. Then in 2001 the firm reentered the market with the latest technology, introducing its 40-ton HM 400 and subsequently the 30- and 35-ton models.

With no installed base of artics that had to be protected, Komatsu was able to apply new technology throughout the vehicles. "We were determined to develop the world's state-of-the-art articulated dump truck to work with what we feel is our state-of-the-art excavator," maintains Komatsu's Steve Moore. "We now offer technology that none of the other artic truck manufacturers has. For example, our artics have fully hydraulic-controlled wet multiple-disc brakes with axle lockups. That provides excellent traction in rough terrain [yet the locks can be turned on and off during travel]. In addition, our artics have limited slip differentials that prevent the tires on either side from slipping on the soft ground that is so typical of landfills.

"Also, our artics have downhill retarder capability. The retarder system works through the brakes by pumping oil into the brakes to cool them. The driver operates the retarder system by pulling a simple lever on the steering column. This activates the service brakes, and that functions as a retarder. On our 40-ton artic, that retarder capability is able to absorb 544 horsepower."

Moore points out how Komatsu had applied new technology throughout each of its artics - the transmission, engine, axles, suspension system, even its center hitch. ("The oscillating center hitch uses tapered roller bearings in a sealed environment, so it is lube-free and requires no maintenance," he explains.)

"These are not 'kit' trucks put together with other people's componentry," Moore continues. "They were designed from the ground up with new Komatsu technology. As a result, Komatsu has changed the ground rules for articulated trucks, just as it did for wheel loaders in the mid-'80s and for excavators in the early '90s."

Those are very strong statements, but user Dennis Gehle echoes that enthusiasm. And if the introduction of new technology makes the difference Moore believes it will, the other truck manufacturers might feel obliged to respond in kind. If so, the next generation of these workhorse trucks might be something to behold.

Charles D. Bader is with Dateline II Communications in Los Angeles, CA.

MSW - March/April 2003