The site is the McCarran International Airport in Las Vegas, Nev., one of the busiest and fastest growing airports in the nation. In 2000, nearly 37 million people flew into and out of this popular entertainment destination, up from just a little over nine million 20 years ago. This unrelenting growth prompted the Clark County Department of Aviation to initiate the multi-year Airport Capital Improvement Program that involves expansion, rehabilitation and overall airport improvements. Current efforts include doubling the size of the new terminal, building new taxiways and aprons, and constructing new jet fuel lines.
VTN Nevada (VTN), a Las Vegas-based engineering design firm, acting as a consultant for the Clark County Department of Aviation, was responsible for a number of project-related baseline controls, design surveys and survey inspections for this effort. It was while working on one of the new jet fuel lines, that VTN surveyors ran into a setback that had them looking to combine a skateboard with the latest in robotic laser technology from Leica Geosystems Inc. of Norcross, Ga.
An Underground DilemmaJet fuel lines typically run along deep trenches situated on airport aprons. Unfortunately, the fuel line contractor ran into a small problem while digging one particular trench—a 180-foot portion of the 1,300-foot trenchline crossed the main exit from the Charter International Terminal. Any above ground digging in this area would have caused major traffic problems. Thus, the contractor opted to bore a 180-foot tunnel. The boring equipment also ran into something hard, probably cemented gravel or caliche common to desert environments, forcing a shift that pushed the bore line seven feet off its original path.
Once the tunnel casing set, it was up to VTN to establish the new fuel line coordinates. The Clark County Department of Aviation required 1/4" accuracy, insuring that the line is properly located for any future expansions. Stephen Pavelka, project manager for VTN who was onsite at the time, recalls “There aren’t very many quick and accurate ways to position a bore line. The most common would be to have one person crawl through the tunnel, stopping at designated spots. This would have been very difficult because of the lack of light in the tunnel.”
Instead VTN opted to use its newly acquired Leica TCRA1103 robotic total station with the remote control RCS1100. Crawling through the tunnel while holding the prism would be difficult and tedious.
“Fortunately, one of our guys happened to mention he had a skateboard onsite,” Pavelka says with a laugh. “We attached the prism to the skateboard, had one of our guys lay on top and sent it through using a rope for safety. Running the robotic telescope on the outside [of the tunnel], we were able to take a shot every five feet.”
The skateboard “scooter,” the crew’s party chief, marked the bottom center of the pipe prior to taking the shot with a special device used for locating the top dead center of a pipe. Because of the curve in the bore, VTN surveyors worked from both ends to get clear shots of the prism moving through tunnel. The job was done in four hours and the final traverse closed .02 foot by .03 foot with .03 foot vertical error. While the vertical error was considered to be slightly out of tolerance, the overall mean worked to the satisfaction of the client.
Building Owner ConfidenceWhile there were few, if any, other options for VTN to handle the bore survey in a timely manner, it’s not always the case. And the client is often wary of new technologies and the resulting information. As federally funded programs, the tolerances at McCarran are very demanding; grades and percentages must be held.
Since purchasing the Leica robotic system in January 2000, VTN has been steadily building client trust in the technology’s versatility, speed and accuracy.
“This often requires that we perform the same job twice—once with conventional equipment and once with the robotic,” Pavelka says. “That’s worked well for both of us. With a fuel line project, we have documented proof that we can, in most cases, achieve the same results, and save time. We find the robotic is more accurate and cuts down on some of the mistakes.”
VTN surveyors used the robotic technology regularly on the Terminal D addition, as well as some ramp rehabilitation adjacent to one of the other terminals, jet fuel pipeline expansions and the construction of new tank farms.
One of the biggest applications has been in the ability to track material quantities. As the client’s site inspector, it is VTN’s job to verify that contractors are within reason when reporting these numbers. On the new expansion, the quantity of dirt work will be in excess of 650,000 yards of dirt. However, contractors are limited to placing certain types of materials in lifts (layers) not to exceed 8-12 inches—again depending on the material type. With the robotic system, it is a one-man job to go down to the site, record the quantities and download them for the client.
Over time, the Leica robotic instrument has proven to be a great help in the design surveys as well. It has allowed the instrument man to take the shot while the party chief takes notes and makes sketches.
“We do surveys faster and with greater clarity [with the Leica device],” Pavelka says. “Another advantage is the ability to create a DTM and then upload that model directly into the instrument. This allows us to verify horizontal position and the elevation in relationship to the planned elevation.”
However, Pavelka is quick to note that VTN did not purchase the robotic technology for its one-man capabilities.
“Working on a busy airport such as this, we don’t want our crews working alone,” he says. “Instead, we’re looking for support. Robotic technology allows us to turn a two-man crew into three providing improved safety, speed and of course accuracy—with or without a skateboard.”