In mass excavation, the formula for success is quite simple: You need productive and durable equipment to move as much earth as you can in as little time as possible. And when a project calls for the removal of almost 1.5 million cubic yards of dirt, the equipment you are using had better be up to the task. At least that’s what Jerry Carter of Carter Excavating in Sand Spring, OK, was thinking when he went looking for an excavator for a $6.5-million Oklahoma Transportation Authority (OTA) project.
Jerry and his father, O.N. Carter, founded Carter Excavating and have been in the mass excavation business for more than 20 years. The elder Carter has seen the company grow from a small trucking business in the early 1950s to the size it is today. Employing more than 100 people and operating a fleet in excess of 100 pieces of earthmoving equipment, Carter Excavating’s main area of expertise is site preparation and commercial development projects throughout Oklahoma, Arkansas, and Missouri. However, being a prime contractor and a subcontractor in Oklahoma is how much of Carter Excavating’s state-funded roadwork and commercial development projects have been completed.
Oklahoma Turnpike Project
Carter Excavating earned the bid for the 2.375-mi. Oklahoma turnpike construction in May 1999, signing up for the task of removing 1.4 million cubic yards of dirt in a 310-day span. Among the challenges of the project included the removal of over 500,000 cubic yards of material for the eventual construction of a bridge across nearby Polecat Creek. Carter determined that in order to complete the mass excavation, a 60-ton excavator would be needed to load 35- and 40-ton dump trucks with approximately 5,000 cubic yards of dirt per day. “We had to top-load these trucks, and to get the kind of production the job required, we needed a machine that had the power to dig sandstone and the speed to meet our daily quota,” he explains.
Sandstone Presents a Challenge
The hardness of the sandstone in that area presented a particular challenge for Carter and his crew. “We had to find an excavator that could dig the softer sandstone, but we realized that nothing could dig some of the hardest areas,” he recalls. “For that, we had to bring in a crawler tractor with a ripper on it to rip and push the dirt so it could be loaded out with the excavator.”
Ultimately, equipment planning was the key for success on the project. “When we were bidding on the OTA job, our project estimator Tim Quattrocchi and I sat down and talked about the project, the production needed, the different types of machines available, and what each could offer,” Carter says. “After working with our Komatsu dealer, Kirby-Smith Machinery Inc. [Oklahoma City, OK], we finally decided that the PC600LC-6 would be the most versatile machine for us as far as moving around the site and still providing the necessary production.”
A New Solution
Komatsu’s newest entrant into its line of hydraulic excavators, weighing in at 131,390 lb., is designed for heavy construction, deep trenching, and sewer, water, and pipe-laying applications. Equipped with the most powerful engine in its class, the 384-hp PC600LC-6 provides features to boost productivity and operator comfort under difficult operating conditions—not unlike the conditions Carter Excavating would experience on this project.
“It’s a large machine,” Carter says. “We already owned two Komatsu PC400-6s, but the PC600LC-6 is a bigger, heavier machine capable of handling a larger bucket for mass-production applications. Basically, it operates like our 95,000-pound PC400-6s. It’s just bigger and able to do more work.”
Once brought on the job, the new machine, outfitted with a 6-cubic yard bucket, worked in tandem with Carter’s two crawler dozers on-site, making 30-ft. cuts. “The PC600LC-6 stays in one area when we are making the cuts,” he describes. “After we remove about 10 feet, the dozers come in and rip the sandstone, and the excavator cleans it up.”
According to Carter, the new machine has proved productive. “We have one operator who uses it most often, and I have operated it as well. We’ve been very pleased with it. It’s a nice machine that has good visibility, is easy to operate, and offers big productivity.”
Heavy-Lifting Mode Increases Lifting Capacity
Specifically, one feature on the PC600LC-6 has helped with the challenges presented by the tough sandstone. The PC600LC-6 is equipped with a special DH mode, which helps boost productivity by providing added power and quicker engine response to sudden load changes. In addition to a general operating mode for light-load work, there is an “H” operating mode for normal digging and loading operations. The heavy-lift mode—easily activated via a switch—can increase lifting capacity by 10%, making it especially advantageous in heavy-construction applications.
“The heavy-lift mode helps provide an extra burst of power when digging up some of the hard rock,” Carter points out. “Of course, when the excavator gets into some of the really dense material, that’s when the dozers have to come in.” The 6-yd. bucket has also played an important role in productivity. Normally equipped with a 3.75-yd. bucket, the larger bucket increased production significantly. “With a 4-yard bucket, the PC600LC-6 might load around 2,500 cubic yards a day with no problem,” he says. “But we needed double that production, and with the bigger bucket, it was easy.”
One aspect of the job that could not have been anticipated was Polecat Creek continuously washing out as a result of frequent rains. “During the first two months on the job, the creek washed out five times,” Carter recalls. “We have the excavator on a bluff on the east side of the creek. When the creek washes out, the excavator loads the trucks and we rebuild it. It has handled the task just fine.”
Project complexities aside, Carter believes the Oklahoma turnpike project boils down to one fundamental challenge. “It sounds simple, but basically this project is a large road job that has a great deal of material to be moved. It has some tricky slopes, hard sandstone rock, and a creek to contend with-all with constant production deadlines that must be met. But we are meeting these deadlines, and the new excavator has helped us to do it.”
