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uch was the case in late 2007when state park officials decidedto rebuild the beach and swim-ming area at Smith Mountain

Lake State Park in Huddleston, VA. Forabout ten years the sand at the beach,which is the only public access beach on

the lake, had been slowly washing away.Some of the finer materials had eroded,leaving behind a coarse material alongthe beach and under the water, accord-ing to the project manager, MarkWomble, Virginia/Carolina Paving, thatwon the bid on the project.Virginia/Carolina Paving is a subsidiaryof W. C. English, Inc.

They wanted us to go in, excavatesome of that coarse material out, andreplace it with a finer sand than they

had used before, Womble said. Weprovided them with a number of sandsamples from different quarries in thearea and they selected one from a quar-ry in Wythville, VA.

Although the beach area was onlyabout two and a half acres, Womblesaid, the problem he faced was that 40percent of the work site was underwater. At first, he said, he thought hewould have to replace the berm under

the water to allow his equipment, a 210Series Komatsu (www.komatsu.com/ce)long-reach track hoe with a 50LF VS60LF boom, to roll further out anddeeper into the water.

As it turned out, however, it wasntnecessary to do that extra underwaterconstruction due to the draught.

The machine was outfitted with spillkits as a protection against any oil leaks,which allowed the excavator to go outuntil the water reached the top of the

tracks, but not the cab.We were lucky with the water lev-

els, Womble explained. Because of thedry conditions in 2007 the machinecould reach everything without us hav-ing to build a dike or any kind of spill-way. If the water level had been higher,the job would have taken longer.

Assisting as back up for the machine

in the water was a D6 LGP Caterpillar(www.govbidspec.com) that worked onthe beach itself, Womble said.

Although low water levels helped thesituation, Womble still faced the prob-lem of knowing where and how much toexcavate underneath the water. He hadpreviously used lasers in grading opera-tions, but he had never worked withGPS before, he said. That was about tochange.

He contacted John McCormick,

branch manager and machine controlspecialist for Atlantic Laser Supply, a

Topcon Positioning Systems (www.top-conpositioning.com) dealer inRichmond, VA. McCormick, alongwith his co-worker Randy Blaine, who isalso a machine control specialist fromAtlantics Chesapeake office, went out tomeet Womble at the beach project.

We had to come up with an idea ofhow to dig through the bottom, putsand in there, and get it packed at theplace where the plans said it was supposeto be, McCormick commented.

In the past Virginia/Carolina Pavinghad been interested in using lasers, butbefore now no project had warranted it,McCormick noted.

After reviewing the work site and itschallenges, McCormick recommendedequipping the excavator with a Topcon

X63 positioning system (formerlybranded as 3DXi). He explained the ter-

Sometimes droughts can be a good thing. By G. C. Skipper

S

Mounted in the cab, the control box includes a monitor that helps the operatormaneuver the bucket.

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minology: X is for excavator, the 6indicates the GX-60 control box, andthe 3 is for three dimensional, he said.

The operator, who controls the exca-vator, said McCormick, sees differentviews of the work site, sort of a birds-eye view, on a control box mounted inhis cab. The monitor has an indicator

on the right hand side that shows youwhere the bucket is going down thegrade. That lets you know where youwant to go and how far to go to getthere, he said.

It was a learning experience, saidWomble. It was my first job withTopcon. We had a surveyor on the jobwho went out and checked the existinggrades to make sure the data on theCAD files were correct. Basically, wetook the engineers CAD files and

downloaded them into the Topcon sys-tem. The work area shows up on ascreen in the excavatoroperators cab. The screenshows the limits of theproject. If the operatorgoes outside those limits,he doesnt have any eleva-tions on the screen. Aslong as he stays inside thelimits, he can take his

bucket and place it any-where on the groundinside the job. The sys-tem tells him if he has tofill three inches of materi-al, for example, or tellshim if he has to cut a footof material out, Wombleexplained.

The excavator operatorlowers the bucket manu-ally, Womble said, digs

out the material, andcontinues to check untilhe has reached the desiredelevation.

System InstallationTo install the Topcon system took

about a day and a half and called for set-ting up a base station on the beach,marking it with a rebar stob so the sameposition could be used every day.Control points also were set up in ran-

dom locations around the job site.The beach was located in a cove,

Womble said, and that enabled us to goaround and set up control points in dif-ferent peninsulas and coves.

As the operator dug the coarse mate-rial out of Smith Mountain Lake, hedumped it into an articulated dumptruck that had been backed out into thewater, said Womble. When the articu-

lated dump was fully loaded, the vehiclehauled the material out of the water.The beach is pretty shallow, he added,with about 170 feet separating the mostdistant point where the water hits thesand on the beach from the point of dis-turbance in the water.

Meanwhile, regular road dump truckswere used on the beach itself to bring insand. The trucks dumped the sand onthe beach, a bulldozer pushed the sanddown to the water level, and the long-

reach turned around, scooped up thesand, turned back around, and dropped

it into the water, Womble said. Oncethe operator got close to where hewanted to be, he would take the bucketand level, or smooth out, the sand underthe water, said Womble.

Because the work site involved a lakebeach, there wasnt much underwatercurrent, Womble said. Over time thewind will stir up a little current. That

probably eroded the sand originally, hesaid.

Nevertheless, to keep the new sandfrom washing away, Wombles crew useda turbidity curtain that acted like afence. The curtain was anchored aroundthe perimeter of the job, where it float-ed, reducing the silt transfer from thejob to outside the job. Its more like aheavy fabric screen that we put around

the worksite, Womble explained.As with any job, the biggest challengein rebuilding the beach at SmithMountain Lake was to come in on timeand under budget. Womble accom-plished both, beating the schedule by 30days. From start to finish, he said, tookabout 60 days.

It was the Topcon PositioningSystem that enabled us to do it. It wasalmost a two-man operation. We had anoperator on the long-reach machine

with the Topcon and an operator in thedozer to push the sand out to the exca-

vator and to dress up thesand on the beach.

Without GPS, heexplained, he wouldhave had to call survey-ors out and manuallymark underwater pointswith buoys.

We would have had

to fill around the buoys,and to verify the work,we would have had tohave a surveyor comeback out and determinehow much fill we hadplaced. Surveyors wouldhave been out there fre-quently.

Topcons system, hesaid, completely elimi-nated the surveying cost

on this particular job.Wombles first experi-

ence with GPS workedso well, in fact, that now he is consider-ing a system for one of his bulldozers.

We will probably stay with Topcon,he said. We think there is good value inthe system we bought and more compa-nies are using Topcon than any othersystem that I know of.

Mr. Skipper is a freelance writer specializingin the construction and trucking industries.He lives in Tuscaloosa, AL.

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Outfitted with spill kits to protect against oil leaks, the excavator waded outuntil water reached the top of the tracks, but not the cab.