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There’s grading and there’s fine grading, but who defines the difference? Some specification writers, public and private, perceive fine grading as a normal part of the excavation and grading operation, and not an advanced level of work that may demand extra compensation. Some contractors see fine grading (usually that vital final step before the building starts) as an optional benefit, appropriate to some projects, but not all. It can be a source of argument between owner and contractor. Before your work begins, make sure to what level of fineness—or should that be finesse?—your grading should go. An acceptable definition of fine grading might call it “the work required to bring the in-place earth materials into their final shape and final compaction level as required in the contract or specification documents.” Fine grading is the final stage of excavation or earthmoving. Be sure that it is included in your bid arithmetic and accurately defined in the contract you sign.
At Basin Construction Co. in Chino, CA, the work includes considerable excavation and grading. Basin has been doing that successfully for 35 years. “Work performed on our projects includes the fine grading for all proposed improvements,” says a spokesperson for the company. “Typically, this work includes the initial rough grading for the whole job site and the fine grading for the new buildings. When the building construction has been completed, we provide additional fine grading for the proposed curbs, asphalt paving, sidewalks, and landscape areas.” That seems to explain well the importance and necessity of fine grading for many grading and excavation contractors.
Some projects do not require that the grading be “fine.” These days, when the city grades the alleys once a year with a motor grader, the grading is impressively accurate, but it is not fine grading as many contractors see it. When the county roads are graded, the results are helpful in making the ride safe and comfortable for drivers and passengers, but the surface could rarely claim to be finely graded; it’s just not in the same class as the ground for the construction of the new school, city hall, church, or private residence. Mind you, we should not underestimate the excellence of road grading or motor graders. Those contractors who are awarded the jobs of grading rural and county roads are held to some tight specifications. Manufacturers tell us that the accuracy of a motor grader can be in the quarter-inch range!
So, how accurate is fine grading, as perceived by the people who do the next stage in the construction project? “My understanding is, typically, that the grade prior to fine grading is plus or minus one-tenth of a foot,” comments Tom Oury of Somero, a company famous for its patented laser screed. Invented in the 1980s by contractor David Somero, the laser screed has changed the way that concrete slabs are placed, and fine grading can play a significant role in the success of that work. “For us, the finer the grading, the better. With concrete we can get to within an eighth of an inch. But concrete grade has to match up to real elevations determined by streets, drains, and curbs at the site, so the contractors’ objective is to provide the prescribed pavement thickness and match up with the real finish elevations. Many bids include 10% extra concrete to account for fine grade imperfection.” The incentive to fine grade, then, may be the savings realized in concrete costs. Yield savings of 8% to 10% are worthwhile and pay off the investment in concrete placing equipment quite quickly. Good communication between the fine grader and the contractor doing the next stage seems practical and cost-effective for both parties.
Simple Grading to a Fine Standard
Some contractors have made their own grading attachments, in much the same way as they made those scrapers that are becoming popular again, pulled behind tractors. They did not want to buy expensive equipment and believed they could design something simple that would produce adequate results. The scrapers are, basically, boxes, and the graders are blades. Can they grade to a fine enough standard? Richard Confoey, in 1995, fabricated a grading device that has become known as the VersaGrader. Talk to Richard and you’ll find that he believes his invention, modified and improved over the decade, can compete with more expensive, more sophisticated equipment, on appropriate sites. The VersaGrader is now manufactured and marketed by VersaGrader Inc., headquartered in New Middleton, OH. That’s a state that seems to have produced many inventions for agricultural and construction use. We are told that an ancestor of the fine grader was a device known as a land plane, used on Ohio’s farmland to even out the chunks and clods of earth to provide a good sowing surface. You could probably find similar inventions in other states, especially in the Midwest. The name John Deere springs to mind, and think of all the attachments and machinery that have originated in Wisconsin, Michigan, and Illinois. There are several patents pending related to the VersaGrader. “We maintain the desired leveling angle even when the vehicle pulling the grading attachment goes over a bump,” says Confoey. “The bumps of the tractor need not affect the blades behind. We call that our Balance Equalizer System. We also have the Double-V Leveling System, where the front blade cuts through high spots and the rear blade levels and redistributes dirt or gravel, leaving a finish grade.”
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PHOTO: BOBCAT |
Who would use this kind of fine grader, pulled behind a tractor? Municipalities? Yes. Contractors? More and more of them, we are told. Traditional uses have been for parks, athletic fields, and paths. It is used today for residential and commercial landscaping, as well as road maintenance. Confoey reminds us the device is used for the maintenance, not the making, of rural roads. It does not crawl along; it can do the maintenance at 7 or 8 miles per hour. It’s a product that does what it claims to do, but don’t try and make it do unscheduled tasks. In Centennial, CO, there are many trails popular with residents and visitors—more than a hundred miles, and they are used constantly in all seasons. “Most of them are made of crusher fine material,” explains Stuart Bunt, for South Suburban Parks and Recreation. “The VersaGrader levels out the trails in one pass. We find it superior to a box scraper for that work. We use a trailer mount and can follow the direction of the trail easily, while the unit stays level regardless of the terrain.”
It’s not just one blade behind a tractor, this VersaGrader, or some of its competitors. It’s sometimes a group of blades, of carefully engineered configurations, and a user will employ different combinations to achieve satisfactory results. Milo George runs Turf Pro LLC in McComb, OH. His company was asked to do the renovation of a local baseball field. How he did it explains well how a pull-along fine grader works. “We started by attaching the sod cutter to the VersaGrader and cut the sod from the infield and also the raised edges around the skinned area,” explains George. “Once our loaders removed the existing sod, our dozer lowered the infield and established a rough grade by laser control. We then attached the regular blades to polish off the rough grade in preparation for establishing the skinned areas and the final grade.” The grading device had the transition grade to within an inch (give or take) without using a laser or another leveling device. Then the contractor’s crew started cutting in the area for the clay mix. “When the topsoil was removed—we used the serrated-teeth blade on the rear for that—we ran the VersaGrader with its regular blades over the excavated area to get a level, smooth base. We did this quickly to within less than a half-inch, without any extra leveling control.”
They spread the clay mix with a loader and used several passes of the fine grading device until they thought they were close to final grade. They then rolled and compacted the area. “We located a spot in the skinned area that was right on grade and adjusted the VersaGrader setting to that point,” continues George. “After several passes, when we realized the grader was moving no more clay mix, we checked for final grade. At nearly every checkpoint we were dead on, and off less than a quarter-inch in the other spots. We always check with a laser.” The final step was polishing with the broom attachment. The job was completed (apart from the hydroseeding) in two days. Milo George points out another advantage. He used to have to transport a box scraper, harrow, rake, and other attachments. Now he takes just the one unit to the site, and nothing is left behind a hundred miles away at the shop. For this kind of grading device, check with your local dealer, remembering that such equipment may be stocked at a construction equipment dealership but also in an agricultural distributor’s yard. The name GradeMaster was also mentioned several times to us, as were Duragrader, Eagle Products, Carver Equipment, and Glenmac/Harley. They are sources you could contact; try for a Web site first.
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PHOTO: GLENMAC/HARLEY |
Excavation and grading are not preparations for only buildings or roadways. For some projects, the final status of the terrain may be a park or, on a smaller but more normal scale, the landscaping for a residence. Fine grading is still important for such jobs. If you are working with new buildings, you may have to clear the surrounding ground of stones and rocks, pieces of construction material, and all that other debris that is a common part of new construction. One of the main reasons that rocks and similar obstacles should be removed is that their presence can affect the efficiency of whatever watering system the property owner installs. Sloping the grading away from foundations is another good practice, for the same reason, as is filling in all low-lying places on the lot. For those residential jobs you may have to use a rake manually for some fine grading, but a box blade or heavy-duty rake can usually do most of the work. Among innovative (and, apparently, successful) fine grading devices for such jobs we have come across bedsprings and short lengths of chainlink fence! What you use can also depend on how much equipment the ground can support. Mini excavators and skid-steers (with attachments) seem popular for fine grading when the work is at a single building or in a confined space.
Tradition Versus Technology?
The proponents of pull-along fine graders tell us that they are as competent and cost-effective as the fine grading systems that rely on new technologies. Our conclusion is that each party may be correct, but it depends on the job—notably on the size of the job. A contractor whose everyday work involves small sites is less willing to make investments in the more expensive instruments of new technologies than the contractor whose grading work often includes highways or building sites for multiple dwellings.
You use what you can afford, and that is not necessarily a reflection on the quality of the product. Automated grade control systems for earthmoving equipment have virtually replaced string lines and stakes on bigger projects, like highways and airport runways. Some of those grading systems will cost the contractor $100,000, so you know there has to be a potential for profit from their use, just as you expect profit from investment in a new loader or excavator. Determination of the profit potential includes calculations about labor costs saved, time saved, and accuracy achieved. With an automated grade control system you can drive the grader across the ground and know that the blade is precisely where it is supposed to be. Some users have pointed out that another saving is in the fact that the operator of the motor grader need not be the most skilled (and most expensive) individual, because the automated system does much of the work. Manufacturers of graders have certainly been trying to make their equipment as simple to use as possible, because reports from both the public and private sectors aver there are not as many skilled, motivated operators available nationwide as there are motor graders for them to run.
We have been assuming that the ground to be graded is fundamentally earth, but machines like trimmers/reclaimers can also provide excellent fine grading on more abrasive materials, such as asphalt. If your fine grading involves road surfaces, you should investigate the merit of a trimmer/reclaimer versus a motor grader. It can produce grade accuracy of plus or minus 3 millimeters (about 0.01 foot) for subgrades and base courses. Trimmers/reclaimers are being used for asphalt paving preparation these days, whereas they were traditionally associated with concrete pavements. Contractors say that the greatest savings are in the cost of paving materials when the base is finely (and accurately) graded. “Fine grading” is something that Commercial Paving & Recycling Co. (CPRC), based in Scarborough, ME, includes in its portfolio of services. “Fine grading is the last step before the paving is done,” notes Marcia Montague, compliance coordinator at CPRC. That confirms what most people think. Fine grading is the last stage before the paving is done, the concrete slabs laid, the houses built. Its quality has a profound impact on the whole project.
Operators and Angles
From regular conversations we perceive that many contractors believe the operator’s knowledge of the machine and what it can and cannot do is crucial to success and profitability at any site. Our operators are as integral to our grading and excavation systems as the machines they drive and the components they control. Some contractors have told us that they cannot find good operators anywhere, at any price, but we are just a little skeptical about that attitude. Of course, nobody runs a machine as I used to in the ’70s! But the corollary of that is that you’d be in big trouble if you did run today’s machines like those of the ’70s. We may think that computer games are juvenile nonsense, but the skills used to run them are quite relevant. Think of the joysticks, pushbuttons, and small finger movements used today where a jolt and shove of the muscular arm and wrist used to be the norm. Before we claim that good operators are not available today, let’s define for ourselves what a good operator should be. He should be productive, care for his equipment, and not require monitoring all day long. The most respected dozer operator we have met in the last two years was only 19 years old; most of those who respected his skills and attitude were twice his age.
Some operators of equipment not usually reckoned as fine grading machines, like big excavators, maintain that they can do fine grading based on their own skills and the configuration of the machine. Wheeled excavators seem to get high marks from operators in this respect, with some of them saying they can not only cut and shape dirt but also bring it to the right level of grading for sidewalks and spreading riprap. Operators of skid-steers and small excavators say they can achieve good results for fine grading, with or without some of the attachments available. There are blades and grading/scraping boxes available as attachments for compact equipment. It all depends on the size of the site, the requirements of the job, and the versatility of the machine/operator combination. “Fine grading at a small, residential site can be achieved with standard equipment and some extra attention to detail” is what contractors are telling us.
If they don’t place the operator as Number One Component for grading, many contractors put the blade in that position. The blades and their geometry have made graders so accurate in recent years. When you add controls that are potentially more accurate than anything human, the grader’s blade becomes the perfect tool for fine grading. To mention just one (and you can probably find details of similar systems from your favorite manufacturer), the AccuGrade GPS control system on Caterpillar’s includes fine grading as one of its targets. It works with the operator. It signals the operator (or the machine’s hydraulic system) to lower or raise the blade to achieve the design requirements at the site by comparing the blade’s position to a three-dimensional, computerized site plan and adjusting accordingly. How close can you get? Down to a quarter-inch, say users and makers. That’s fine by any standards. This system has worked well, we are told, for those sites that have a flat, single- and dual-sloping planar design; those could be pads for buildings, roads, highways, and parking lots—school playgrounds too, and gas station forecourts, if you get into that kind of work. Design engineers can develop quite complex designs and load them into the system for the earthmoving machines.
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PHOTO: GLENMAC/HARLEY |
If you compare the specifications of graders from different manufacturers, you will find they are very close in many aspects. Check the engine power, weight, transmissions, drivetrains, and overall heights and dimensions and you will find the variations are minimal. We did notice differences in blade clearance of 2 inches and wondered how important that would be for some contractors, and the difference in turning radius for similar models from four different manufacturers was as much as 30 inches. For some 20 key features, however, the numbers were remarkably close. This may indicate that manufacturers learn from their customers what is important in the design of a grader and update their models accordingly. All-wheel drive is a feature worth investigating. In two-wheel drive you have only the front wheels of the grader with power, and that’s what you’d use for slow-speed fine grading. With four-wheel and six-wheel drive engaged, you get more power and better traction (for jobs like plowing snow).
There is no doubt that you can produce fine grading. The machines, attachments, and instruments are there to achieve the results specified. The level of your investment will depend on the size and regularity of your projects, but it seems that devices for fine grading are available from the most simple to the most sophisticated. That means there is no excuse today for failing to produce fine grading, when it is needed in preparation for the next stage.
Paul Hull writes on environmental and construction topics for several international magazines.
GEC
- January/February 2006
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