O ver the last decade or so, barrels of ink (and, to put it in 21st century terms, perhaps,

terabytes of data) have been spent touting the benefits contractors—even smaller firms—can realize with the addition of GNSS-based equipment to their operations. Every now and then, however, a project comes along that so starkly highlights the advantage GNSS offers, that it simply demands another retelling. A taxiway expansion at a Conroe, TX air-port is one such example, and the degree to which contractor RCD Construction Services made believers out of skeptics

warrants that more ink be spilled, more data be transmitted and more converts join the ranks of the newly-initiated.

Almost IntimidatedThe Lone Star Executive Airport in Conroe is a regional facility that services private flights into and out of the Houston area. Looking to eventually accommodate larger aircraft, the facility recently began an expansion project which called for new taxiways and a number of additional support facilities. The scope of the project was fairly daunting for a smaller contractor—so much so, in fact, that Rodney Downey, owner of RCD Construction Services considered not even bidding on it.

“The job site is about 15 acres and the specs called for bringing in more than 10,000 loads of import fill, some mas-sive excavation for retention ponds and extremely tight specs to accommodate the concrete contractor’s formwork,” said Downey. “We are a small contrac-tor, and we had only fairly recently started using GPS—a Topcon base and rover was all we had—so the idea that we could compete against some of the much larger companies bidding on the airport job seemed ridiculous.”

Downey contacted Scott Bird, machine control specialist for the local branch of Topcon dealer, GeoShack, and had him meet him at the future jobsite to see just what he was facing. By LarryTrojak

Minimal Crew, Maximum Production

Equipped with Topcon’s 3D-MC2, RCD’s John Deere 700K was able to keep pace with a non-stop stream of trucks working 10-hour days to get 120,000 yards of soil placed, compacted and graded.

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“I told Scott that I was really leery of tackling the project with what I had, and reiterated how quickly the GC needed things done; how uncertain I was about it all. While I expected him to agree with my apprehension, he instead looked at it and said: ‘Total machine control could just tear this thing right up.’ It was not what I expected, but it got my attention. We were soon talking about outfitting a pair of John Deere dozers—a 700J and a 750J—with Topcon’s 3D-MC2 machine control, the tools which Scott said could definitely make this all happen.”

Oh, Ye of Little FaithDowney was not the only one with misgiv-ings about taking on such a huge project. He said that almost everyone involved in the preliminary planning had some level of doubt regarding his capabilities.

“At a meeting of the project princi-pals, all the questions centered around

how fast we could get it done, how much equipment could we put on the job, how many men we could bring in? Based on what Scott had assured me—and the economic realities of the job—I told them I was looking at how few men and pieces of equipment I could do it with. We came in with the lowest bid and won the project, but it was obvious that only the developer, Black Forest Ventures, with whom we’d worked many times before, had any faith in us.”

After subcontracting out the clearing portion of the project, RCD’s real “baptism by fire” came in the form of bringing in and grading the more than 120,000 truck yards of fill the job demanded. During that time, said Downey, there was a non-stop stream of trucks into and out of the site.

“We were working 10 hours a day getting about 600 loads a day—literally a load a minute. But as fast as they were dumping we were right behind them

with one of the dozers, putting it in lifts, compacting it, having it tested and mov-ing on. That was where we really started turning some heads. At the outset, people were uncertain if we would be able to keep up, but since starting no one has ever had to wait for us. Truth be told, more often than not, we are waiting on one or more of the other trades.”

A Grade of its OwnBecause the future taxiway and tarmac need to support the significant weight of aircraft and support vehicles, the composition of the subgrade and base is far from normal.

“In order to stabilize the soil, we are first using a Cat RM 300 rotary mixer to mix 30% lime with 70% fly ash and laying down 8-inches of that mixture. Then we come back with 9-inches of cement-stabilized crushed concrete, and then add 8-inches of concrete on top of

An ability to make adjustments on the fly has proven particularly valuable to RCD on the airport job. Instances in which they were getting more vertical compaction one day than the next—once a major issue—were easily dealt with from within the cab.

RCD’s Downey says the tight tolerances needed for the cement-stabilized crushed concrete base—making way for 8-inches of concrete on 8-inch metal forms—presented the biggest challenge on the Conroe Airport job.

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that. Each of those first two steps would have been done using blue tops in the past; instead it is all being done using machine control.”

Getting down the stabilized crushed concrete is actually the most critical part of the process. Because the concrete forms are exactly 8-inches high, a rock in the secondary layer could result in a form being too high. Downey said the GNSS system has risen to the challenge.

“It has been right on the money throughout the project,” he said. “In fact, at one point, the concrete crews had their stringlines out and were preparing to put their forms in, when they called me over to tell me we were four-inches low at one end. My dozer operator drove over there, set his blade down and told them their stringline was wrong. I went to the foreman, he checked the prints and the string was, in fact, wrong. That earned us a whole lot of respect.”

One of the system’s features that has proven particularly valuable to Downey is its inherent ease-of-use. “Our ability to make adjustments on the fly—with the vertical offset, for example—has been a real plus. If, for some reason we are getting more vertical compaction one day than the previous one, it is not like we have to reinvent the wheel. The operator can simply make the adjust-ment in the cab and keep going. That’s really helped keep us moving.”

Making BelieversIn addition to the tarmac and taxiway areas, the Lone Star Executive Airport job was complex, involving massive earthmoving segments to create deten-tion ponds, drainage ditches, assorted sloped areas and more.

“Much of the area in the back of the site has 10-12 feet of fill and we used GPS on every last part of it—we have not put in a stake or a blue top on the entire job. When Scott came out here and looked at it, he promised a lot, but the system has actually outperformed what he promised. Even now I will periodically set up a laser just to check it; it’s hard to believe.”

The value of GNSS has spread throughout the site as well, with other tradespeople seeing the value it brings to the jobsite. Downey jokes that he is GeoShack’s unpaid salesman on the job.

“The concrete contractor is a great case in point,” he said. “To get their forms laid out, they were driving rebar and running string. I told them that they could use our rover to simply walk down the line, and, because we have the surface designed in the model, just do a vertical offset of .66 to get the 8-inch form depth, set the rod down and mark it. They are just loving it and it wouldn’t surprise me to see them owning their own GNSS gear in the future.”

Game ChangerWhen asked how long the project would have taken using traditional methods, Downey is quick to say that he simply would not have even bid on the job without GNSS. The new approach has been that much of a game changer for his business.

“We are in here with five men and five pieces of equipment; in the past, that would have easily been 10 machines and 12 men and I’m sure we still would not be getting 2/3 of the production we are getting now. Getting the base down alone would have involved four or five guys on the ground. This has undoubt-edly been the best project we’ve ever done—but I can definitely see more like it in the future.” MC

Larry Trojak is a communications writer for his own firm, Trojak Communications, in the town of Ham Lake, Minnesota. He is a frequent contributor to construction and survey magazines.

Working alongside a Cat Pulvermixer which mixed 30% lime with 70% fly ash to stabilize the airport’s soil, the machine control-equipped Deere 700K, has been extremely productive. RCD’s crews, once guilty of holding down production, are now typically waiting on other trades.

Downey says they did all the 3:1 sloped ditches (some as long as 3,000 lineal feet) and detention ponds without a stake or bluetop in sight. He anxiously awaited the first rain to confirm they would drain—they worked perfectly.

Displayed with permission • Machine Control Magazine • Vol. 3 No. 3 • Copyright 2013 Spatial Media • www.machinecontrolonline.com