That was the case for North Pine Aggregate Inc. when working the site last season for a housing project in Otsego, MN. The project called for moving nearly 2 million cubic yards of earth, and North Pine owner Dennis Jensen had bid it as a scraper project. “We’re mostly a scraper-oriented company,” he says.

On the Otsego job, he says the firm started out with scrapers but had to pull them out because the wet, expansive clay soil bogged down the big twin-engine machines. “So we brought in excavators, articulated trucks, and wide pad dozers,” says Jensen. “It was wet, fat clay.” His equipment of choice: two Komatsu PC600 excavators, two Caterpillar 345B excavators, and at the peak, 10 articulated trucks—six John Deere 40-ton units and four Volvo A40C trucks. A mixture of John Deere and Caterpillar dozers rounded out the fleet.

“I bid it as a scraper job, and we had pretty good scraper money on it,” says Jensen. “But it was more costly to move with the trucks, because the load count was down so much. It was about a break-even project for us.”

Two of the excavators stripped topsoil and made cuts. “And if there was a fill nearby, we would throw it over and place it with the wide pad dozers,” says Jensen. Two of the excavators loaded trucks; hauls ranged up to 2,500 feet.

The clay was so wet that North Pine had to “farm it” to dry it out. “We had disks going steadily,” Jensen recalls. “We had two John Deere 9400 four-wheel-drive tractors pulling 36-inch offset disks. When we could, we would put the wetter stuff back into a borrow area where we didn’t have to meet compaction specs.

“The dozers worked well,” he says. “We used them a lot making cuts and fills. We would push a lot of the dirt up to 300 feet because it was so hard to get around with the haul units.”

By contrast, scrapers proved to be the answer on a 1.5-million-cubic-yard job that North Pine did in Rogers, MN. “At the peak we had eight Caterpillar 637E scrapers and two 627G units,” says Jensen. “The average haul was 1,200 to 1,400 feet. It was sandy clay—nice stuff to work with.

“We push-pulled the scrapers,” he says. “No push dozers were necessary.” The job did require a number of dozers to strip topsoil or replace it once the area was brought to grade. The dozer fleet included two Caterpillar D8R machines, one Cat D9R, and two Cat D6RXL units. One Cat 815 compactor completed the fleet.

So how was production? “We bid it for 100 loads per day per scraper,” says Jensen. “We actually had a lot of days where we did 140 to 150 loads per day per machine. So on that job, scrapers were the most economical way to get it done.”

High Production
“We just finished moving 8 million cubic yards at the Pittsburgh Mills Mall,” says Rich Doyle, project manager with Trumbull Corp. of Pittsburgh, PA. “Clearing started in April 2003, and dirt moving began that July. We had our first 4 million by November 2003, and the other 4 million by July 2004.

PHOTO: TRUMBULL

“Working double 10-hour shifts, we moved the first 4 million in four months—1 million yards a month,” says Doyle. “They needed the first 4 million completed so that they could start the building in November 2003. It’s a very large mall.”

About half of the job consisted of sandstone. Another quarter of it was shale and a clay-shale blend. The remainder was dirt. “We blasted 6 million yards of the 8 million,” says Doyle.

For Trumbull, it was a $31 million project that included earthmoving, drainage, sanitary lines, and a utility package. The contractor attacked the earthmoving job with two huge Caterpillar 5110 excavators, a Cat 992G wheel loader, eight Cat 777 rigid-frame trucks, one Cat 773 truck, and two 50-ton Payhauler trucks. The big Cat excavators had 10-cubic-yard buckets. Yet another equipment spread added a Caterpillar 365 excavator and four Volvo A35 articulated trucks. Five Cat D8-size dozers, two D9 dozers, one D10, and two Cat 16G blades rounded out the fleet.

“You wouldn’t get much production out of scrapers in that sandstone, blasted or not,” says Doyle. “You can’t load them. You get 2-foot and 3-foot pieces, and you’ve got to push them 300 feet to load them.

“That said, you probably could have done half that job with scrapers,” he adds. “A lot of the shales and clay shales could have been done with scrapers. But we don’t own any scrapers.”

PHOTO: TRUMBULL

At the mall, the deepest cut was about 150 feet, and the biggest fill also measured about 150 feet. The two big Cat excavators and the wheel loader filled about 180 loads in a 10-hour day. “We got between 180 and 200 loads a day, depending on the material we were in,” says Doyle.

Meanwhile the Cat 365 excavator, fitted with a 5-cubic-yard bucket, worked the ponds and the smaller cuts—the low-production dirt. That spread could move about 2,500 yards a day—200 to 250 yards an hour.

Tracks for Wet Soil
When it gets too wet for rubber-tired scrapers, Ryan Inc. Central moves in with its crawler-tractors pulling scrapers. The tracked machines can only move about 6.5 miles per hour, but they can forge through wet and soft conditions that will stop or greatly slow down a rubber-tired scraper. The Janesville, WI–based company has a fleet of John Deere 1050C crawler-tractors, as well as Caterpillar D8T tractors and D8R units, all of which pull Rome tow-behind scrapers. “The D8R machines are a second-life tractor,” says Mike Gabel, a Ryan project superintendent. “We put 8,000 to 10,000 hours on those tractors as dozers, then rebuild the engines and transmissions and use them to pull pans.”

PHOTO: CATERPILLAR

On a recent project in Chicago’s south suburbs, Ryan first stripped the topsoil with John Deere 9520 tractors pulling double pans—then followed with the track-type tractors pulling Rome pans. That project required moving about 1 million cubic yards, and Ryan mobilized six John Deere 1050C tractors as well as five Cat D8T units and one D8R tractor.

“Moisture content was upwards of 25% to 28%,” says Gabel. “It was too wet for rubber-tired scrapers. Once you start stripping the topsoil with rubber tires, it starts pumping water up to the surface and you can’t use scrapers.”

Ryan likes to restrict the tractor-scraper combinations to hauls of 1,500 feet or less. “You don’t want to stretch out a crawler-and-pan combination too far or your production will go down,” says Gabel. “Their maximum travel speed is about 6.5 miles an hour. But the crawler-and-pans don’t require as much support equipment, such as a motor grader, so your overhead goes down. In wet conditions with a long haul, you have to use haul trucks.”

Like Gabel, Rich Keller, a partner in Lake County (Illinois) Grading, likes to restrict the haul length for his tracked-tractor-scraper combinations. He has four John Deere 1050C tractors that pull either a Caterpillar scraper or MRS 100 scrapers made by Mississippi Road Scraper.

“Typically we put a mix of scrapers and crawler-and-pans on our jobs,” says Keller. “We run the 1050C tractors if the ground gets soft, and we run the scrapers if the hauls get longer and the ground gets drier.”

Keller likes the John Deere 1050C tractors for their hydrostatic transmissions. “With the hydrostatic drive, we haven’t been going through torque converters, steering clutches, and brakes,” says Keller. “If we keep the oil clean, these hydrostatic units should last a long, long time. The cost per hour is pretty good; those tractors are working pretty hard. And track wear has been minimal as well.”

For a 1.2-million-cubic-yard job shopping center project in St. Joseph, MO, Clarkson Construction Co. chose a combination of methods—scrapers and an excavator-with-haulers team. “We ran Caterpillar 631E scrapers that were push-loaded with a Cat D9,” says Steve Kellerman, project manager for the Kansas City, MO–based company. “We had packed clay; it was pretty wet.”

Haul lengths for the scrapers ranged from 1,000 to 1,500 feet, and production averaged about 15,000 yards a day, or about 750 loads daily. “Where we had wetter material or had a hard time getting turn-around room for the 631s, we ran a John Deere 600 with five Volvo articulated trucks,” says Kellerman.

“We knew we were going to have wetter material; there were seams of wet material,” says Kellerman. “When we excavated for the retaining walls and ponds, we used the ’hoe. All the material was fairly wet, but some stuff went to slop. We couldn’t move it with the scrapers, and we had a hard time even with the trucks.” The project was bid as a scraper job, and Kellerman says Clarkson “did all right” financially.

In short, success in earthmoving is largely determined before the first wheel or track ever turns—in the planning stage. If you explore and plan for wet material, you can bid for it. If not, your profits can get stuck in the mud.