Dig with Precision

You're likely aware of the advantages grade control systems can offer on finish grade machines such as dozers and motor graders. But less known is the fact that modern technologies that compute the precise position of an excavator bucket promise similar productivity gains and reduced labor costs. To get the inside scoop, we interviewed five contractors who have witnessed these benefits firsthand.

Operator praises precision
Orem, UT-based Kenny Seng Construction performs concrete, utility and earthwork for projects such as elementary schools, high schools and supermarkets. Its Caterpillar-based fleet includes excavator models ranging from a 305 to a 330. We caught up with operator James Bawden on a school construction project in Moab, UT.

For the last year and a half, Bawden has run a Caterpillar 322 excavator equipped with a Topcon 3-D GPS system. "It is really user friendly," he reports. "It is easy to learn, but you still need a skilled operator." The system will give you the starting point, but it is still up to the operator to pull grade.

Bawden admits that a laser system is the most accurate. However, you can get very close with the GPS depending on how much you are willing to slow down. "With the 3-D GPS, you can get to within 15/100ths of a foot. If you want to really slow down and do it yourself, you can pretty much get to grade, but then you are going too slow for production. For everything final, we do use a site laser and a laborer."

The real benefit of GPS has been the reduced staking effort. "It eliminates a surveyor," says Bawden. "You obviously have more production because you are not waiting on a surveyor. You can go ahead and excavate. You have less need for a laborer to check grade with a site laser. Basically, it is better all around. It ups your production and you save money on help."

Consider the school  project Kenny Seng Construction  is currently completing. "Every footing has 3 ft. of over-excavation underneath it, then we are bringing it back up in 1-ft. lifts," Bawden explains. "Rather than having my helper put his laser at 1 ft., then 2 ft. and then a final, I basically do all of that without him and he can be doing something else. I only need him for final."

Speed to grade improves
H&M Excavating of Penticton, British Columbia, has a Hyundai 290 and a Hitachi 330 excavator equipped with Topcon 3-D systems. This setup speeds the time it takes to get projects within the tolerances required.

The company designs its own electronic maps and is well versed in GPS grade control technologies. "It is relatively easy to set up a machine control job," says Don Hayter, who educated himself on the systems before purchase. "We will even use it for a small parking lot job."

Due to mountainous terrain, H&M Excavating performs a lot of slope work. The traditional method for grade checking on slopes is very tedious and labor intensive. "If you are cutting a big slope, or filling a large embankment, there is a lot of checking that goes on to keep it accurate," says Hayter. "You can work with a slope jig and keep carrying the slope, but it is hard for a [grade] checker with a slope jig to stay accurate. They start wandering off and then you have to re-survey and get trued up again."

The process is dramatically simplified with the 3-D excavator system. "With the [system], you can carry a slope a long way - all the way from the top to the bottom," says Hayter.

For example, the system was used on a recent water treatment plant. "We built all of the slopes, all of the containment ponds, everything. It worked really well on that project," he states. "We had some big slopes there." A grade checker with a GPS Rover on a rod was used on one slope. "On others, we just did the whole thing with the machine control on the excavator. That was the efficient way to do it."