Grading and Excavation Contractor

Productivity is the name of the game on this project. Technology, power, and maneuverability are the factors that make it happen for us on this job.

By Gini and Dan Mckain

Tiger Contracting has a contract to build a new 178,000-square-foot Lowe’s Home Improvement Center on a 15-acre site in Indian Harbour Beach, FL, and this must be done in a very limited amount of time. Also, because of the time restrictions and complexity of the job, the company’s management has seen fit to provide it with a new LeeBoy 685B motor grader and a Cat D5G dozer to help with the site work. Additionally, it has outfitted the equipment with the latest global positioning system (GPS) technology. The contractor selected the Trimble Model GCS900 units for both machines. According to Tiger’s Project Manager Scott Smith, Tiger has subcontracted the job from Marcobay Construction Inc. from Lakeland, FL. The work is a challenge because the new center is being built on the site of nine former buildings that were either damaged or destroyed during a recent hurricane season.
The Trimble GCS900 Grade Control System is an automatic control system that puts design surfaces, grades, and alignments inside the cab using GPS technology. The system uses the MS980 smart antenna, a fully integrated GPS receiver and antenna, mounted to each end of the machine blade. The system can operate in a completely stakeless environment and grade to an accuracy of 20 to 30 millimeters (0.1 foot).

Complications on the Lowe's project include the fact that the home improvement center is being built on a site recently ravaged by hurricanes.

On some work sites, the GCS900 uses the horizontal guidance to mark the bonds of pads for other machines, enabling them to do rough work without survey stakes. On other sites, the GCS900 allows large dozers to work much closer to grade finishing pads that previously would have required additional smaller machines for the final work.

On bladed equipment (graders and dozers), the GCS900 can operate in either indicate or automatic mode. In indicate mode, light bars and a graphical color display use the project design information and 3D GPS and cross slope to show the operator what blade elevation and cross slope movement is required to get to grade. The unique, dual GPS antenna system indicates the exact position, slope, and cutting-edge orientation for faster grading of complex designs and maintaining accurate blade cuts.

With the automatic blade control option, the GCS900 system is connected to the machine hydraulics. Using 3D GPS position, cross slope, and design information, the blade is automatically moved to the exact elevation and cross slope. The result: significant improvements in both productivity and accuracy. If large cuts are required, the operator can instantly offset the design surface so smaller amounts are cut on each pass.

The GCS900 is a simple, easy-to-use, rugged machine accessory for the whole fleet. It gives more value and greater return from the machine and operator. Using the GCS900 can help reduce material overages and graphically improve project profitability.

The MS980 smart antenna is an integrated GPS receiver and antenna that is designed to provide maximum portability and flexibility. The rugged, smart antenna has been specifically designed for machine installation at the rough cutting edge and has extensive, field-proven performance in construction applications.

“At the same time we were preparing the site we were crushing, processing, and recycling a significant amount of old onsite concrete material,” says Smith. “This included the old footers, building pads, and paving that was available to us. This has a twofold benefit. It saves money, and recycling is good for the environment. An additional benefit is that we have much of the basefill material that we will need already here. No need to truck it in, no depending on someone else to get it here when we need it and being held hostage to their schedule!

“Equipment utilization and mobility are two of the major factors that help us achieve that. It is incumbent upon us to do the job to the best of our ability. The client expects nothing less. The faster we get the job done, the sooner they can open the store for business and we can go on to our next project. That, however, is a tall order on a 15-acre site.

“That’s where GPS and laser technology come in. At first glance, 15 acres sounds like a large area. However, by the time we have much of the site work done and the building laid out, it shrinks considerably in size. The subcontractors, demolition contractor, the block layers, the underground utility contractor, and the paving contractor all have their materials and equipment here. So the site shrinks significantly.”

The contractor is currently in the exterior wall erection stage and parking area construction of the project. This latter involves a large amount of earthwork for which Tiger relies heavily on the GPS and laser technology. The extension of an existing large retention pond also has required the use of the new Leeboy 685B motor grader and the Cat dozer, both fitted with the high-tech electronics.
According to Site Superintendent Rick Mosley, the powerful LeeBoy motor grader was specifically selected for its size to cope with the tight working area. The 685B, normally fitted with a 10-foot sliding moldboard, was fitted with a longer 12-foot blade because it was felt that the 15,200-pound machine with its 110-horsepower Cummins diesel engine could handle the weight of the onsite sand and processed stone, which weigh approximately 2,600 pounds per cubic yard.

The first physical onsite operation involved the demolition of the structures, done by Cross Environmental. The next phase was the crushing and recycling of the concrete. This also involved the recovery and salvage of the imbedded reinforcing steel. Tiger then brought in a portable crusher and screener to process the salvaged concrete. The material was processed into #57 stone, fines, and #4 aggregate.

The #4 material was used in the construction of an onsite storm vault. The #57 stone was used as bedding and backfill for underground utility lines. The extra #57 stone and the fines were incorporated into the construction of the building pad. The original intent was to employ asphalt pavement for the parking area, which included 40 some traffic delineator islands. This, however, was changed to poured-in-place concrete paving.

Existing onsite underground utilities, including a live 8-inch sewer line, hampered the normally smooth project flow line. Most of the old utility lines had to be removed wherever possible before the new lines could be installed. To reprofile and enlarge the existing stormwater retention pond and reprofile the drainage pattern, the contractor relied on a Komatsu PC200 excavator to outload the stockpiled material into a Case rear dump hauler. Both the Cat dozer and the LeeBoy 685B motor grader, employing the Trimble GPS system, were then used to spread the fill material. A Bomag roller then compacted the new fill. Because of the extremely dry weather, Tiger crews used two water trucks almost constantly to supply moisture to rehydrate the soil to the proper percentage.

One of the most critical aspects of the new Lowe’s Home Improvement Center project has been time. From the day the contractor first began construction of the building’s footers, the contractor had exactly 110 days to complete the project.

This included the modifications of a portion of US Route A1A. The job was to add a 12-foot-wide safe turn lane from the very busy highway into the Lowe’s complex. Tiger Contracting also used a new LeeBoy 685B motorgrader on this to profile the subgrade and add two 6-inch-thick lifts of crushed limerock to work in and around several power poles that had yet to be relocated. The optional, 12-foot-long moldboard was just the right size for the new 12-foot-wide lane, as well as maneuvering easily around the obstructions. In addition, crews used a Bomag roller to obtain the state Department of Transportation–specified compaction density.

With the summer rains and start of the 2007 hurricane season only a few weeks way, Tiger Contracting had its work cut out for it. Everyone was counting on the new LeeBoy 685B motor graders and the small Cat dozer with the new high-tech electronics to come through on time.

Gini and Dan McKain are photojournalists specializing in construction activities.

GEC - March/April 2007

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