GPS Boosts Road Builders’ Productivity
by Jeff Winke
October 6, 2010
Bob Bergkamp Construction equips its dozer with Trimble GCS900 Grade Control Systems with dual GPS.
System turns skeptical construction workers into technology fans.
Though the city of McPherson lies just
east of the center of Kansas,
it is dead center of a major construction project.
In early summer 2009, officials announced the first
road-building project in Kansas funded by the American Recovery and
Reinvestment Act of 2009—the construction of a new 22-mile stretch of the K-61 Highway
corridor, running diagonally from McPherson southwest to connect with
Hutchinson, Kansas. The new $64 million road project stretches from McPherson County
into Reno County.
The four-lane highway project is a new road alignment just
west of the original two-lane K-61
Highway. One of the reasons for moving the road
from its existing path is to locate it farther away from the railroad tracks in
order to meet new environmental standards and to avoid disruption of the agriculture
for the nearby ranchers. Sections of the project called for incorporating the
footprint of the old road, but much of the planned construction required
purchasing right-of-way rights from farms abutting the new highway.
Starting off with Software
Bob Bergkamp Construction of Wichita, Kan., won the bid for
building an eight-and-a-half-mile section of the new K-61 Highway project.
The company used a 3D model of the project to support the
GPS-enabled heavy equipment, total stations and data collectors used throughout
the jobsite.
“We took the Kansas Department of Transportation’s CAD files
and used Trimble Terramodel and Trimble Business Center-Heavy Construction
Edition office software to convert the files for use on our machines and rovers,”
says Justin Howard, field engineer with Bob Bergkamp Construction.
“The Trimble software gave us all the jobsite and surface
modeling we needed to establish the road parameters.”
Clearing the necessary 200- to 400-foot wide swath for the
new road was a challenge. “This was one of the bigger clearing jobs we’ve had
to do on a highway project,” says Rick Thome, project engineer with Bob
Bergkamp Construction.
“It took a month to cut through the brush, trees and heavily
wooded land. We’d clear a section, start the actual road-building process and
then move down onto a new section.”
After clearing the new roadway swath, the initial push was
to establish the bridge berms so the two bridge contractors could complete the
work. Overpass bridges required pilings be set anywhere from 60- to 200-feet
deep, with footings at 8- to 10-feet. Bergkamp Construction needed to build 18
bridge berms that were about 20- to 25-feet above the road grade.
In its road building, Bergkamp Construction used an
approximate 50/50 soil mix—which was about 1 million yards of on-site dirt and 1
million yards of imported dirt.
“We had to remove the top 6 inches and rework the bottom 6 inches,
and then put that 6 inches back before the finish grading,” Howard says. “The
dirt was tested to 90 percent density until we reached the top of the fill
where it tested for 95 percent density.”
Grading with Precision
The Trimble systems put the site plan—design surfaces, grades and alignments—right inside the cab, helping the operator achieve a plus or minus one-tenth millimeter accuracy.
“The blades have the Trimble MS990 Smart GPS Antenna, which is an integrated GPS antenna and receiver, and we have the most advanced control box available, the Trimble CB430 Control Box, with its very readable screen, even in bright daylight,” Howard says. “We have the technology to reliably achieve grade in one pass.”
For their stretch of the K-61 Highway corridor project, Bergkamp Construction used three Trimble SPS851 Modular GPS Receivers for semipermanent base station setups to support the grade checking, site measurement and stakeout. The combination radio and GPS receivers were set up on both ends and in the middle to ensure adequate coverage of the entire site.
“There’s a configuration function in the SPS851 that allows for multiple base points to run off the same continuous calibration,” Howard says. “This saved me at least a couple of days of setup time since each base station didn’t require the time to establish its location base point.”
Going the Distance
For Bob Bergkamp Construction, the eight-and-a-half mile K-61 Highway
project was one of its longest distance road building projects. At their busiest,
they had four crews amounting to about 30 workers at the site.
It was also the most GPS-based technology they’ve had on one
jobsite. “Having the Trimble technology was a tremendous help, and it saved us
time and increased production,” Howard says.
The company’s foreman was able to walk ahead of the
production crew and establish points using the rover.
“This is far better than having to pull 100 feet of tape up
a hill to stake it, and then run back down the hill to use an eye level,”
Howard says. “Here in Kansas,
a light breeze is 20 miles per hour, so that tape would be blowing around.
“The technology helps
cut production time,” Howard continues. “Most of the time you don’t need
stakes. The GPS-guided machine will do
it for you. We can control the volume of fill with each lift by doing a
vertical offset. It has really helped us maintain proper compaction, especially
when we needed to transition Type A compaction to the Type AA. The inspectors
are a lot tougher on the Type AA, which is that 18-inch zone at the top.”
Unusually wet weather created schedule challenges, but Bob
Bergkamp Construction was able to complete the project on time. The project
also had a bit of a learning curve for Bergkamp’s workers, who were initially
resistant to using GPS grade control systems.
“Some of our employees were pretty old-school,” Howard says.
“But now that they’ve experienced the Trimble technology,
they are confirmed believers in using technology. It didn’t take them long to
see that once we finish something with the GPS-guided machine, 99.9 percent of
the time there is no rework, because when it’s done, it’s done accurately.”
Jeff Winke
Jeff
Winke is an independent construction writer based in Milwaukee. He can be reached through www.jeffwinke.com.
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