Dodging the Curve
May 14, 2008
When Paul Young, project superintendent for Clark Companies, stepped up to the plate last fall to give Alliance Bank Stadium in Syracuse, N.Y., a facelift from AstroTurf to natural grass, he met some unique challenges.
For 30 years, 60-year-old Clark Companies, a Delhi, N.Y.-based engineering and construction firm, has specialized in building sports fields. Its roster of jobs includes field construction at Giants Stadium in East Rutherford, N.J., the National Soccer Hall of Fame in Oneonta, N.Y., and Doubleday Field in Cooperstown, N.Y. But Alliance Bank Stadium was different. This project, Young soon found out, was going to throw him a curve.
With Bases LoadedThe decision by Onondaga County Parks officials to replace the decade-old AstroTurf and go au naturel created a challenging lineup of obstacles for Young and his crew. The drainage system had to be retrofitted, numerous slope changes on the field made the use of laser control equipment difficult and the stadium grandstands blocked GPS signals.
Young knew from experience that baseball fields can be more complex to construct or renovate than other types of sports fields--especially when it comes to grading. Football and soccer fields are flat longitudinally and typically have a half-percent crown from the center to the sidelines. Baseball fields, Young explains, are level on the infield, and then the pitch rises half a percent from the bases up to the pitcher’s mound. After that, he says, the grade usually falls at a constant rate of percentage to the outfield.
Also, because an outfield is not symmetrical--center field could be 400 feet out, while left field and right field might be 330 feet out--there could be as much as 70 to 90 feet of difference between the points. “The field has to be level all the way around,” Young says, “so there is a whole different grade involved in that.”
Stepping Up to the PlateThe design plans provided by Appel Osborne of Syracuse called for him to grade the field with laser technology. In most cases, a cone laser or system of dual lasers can be set up to work for this type of application. But when Young hauled in his laser-based machine-controlled John Deere 650H dozer to the Alliance Bank Stadium site, he found that the outfield didn’t lend itself to this application. And when he tried a GPS system, the satellite coverage wasn’t adequate because the stadium’s structure obscured the skyline. In addition to the home-plate grandstands that blocked consistent satellite signals, another problem with a GPS-only system was that the margin of error was larger than the quarter-of-an-inch tolerance called for in the specs.
Temporarily without proper equipment and technology, Young said he had no intention of muddling through the job. He contacted machine control specialist Tom Krenzer of Admar Supply Company, who had installed the laser-based machine control system on Young’s John Deere dozer.
In just five days after looking at the stadium, Krenzer and his team worked out a solution: a Case 650K series dozer equipped with a Topcon ( www.topconpositioning.com ) Millimeter GPS machine control system, a HiPer Lite+ dual-constellation geodetic receiver and Topcon’s Windows-based Pocket-3D data collection software.
“The millimeter system was the answer,” Krenzer says. “On a regular field you wouldn’t use GPS. You would use a regular laser. But by installing the millimeter system, we were down to precise measurements of up to 1/300th of a foot, which is extremely accurate.”
That degree of precision is possible because the system’s LazerZone fan technique shoots a beam of light 33 feet high in a 360-degree circle up to 2,000 feet in diameter. “Tolerances are put into the laser, and it knows what corrections to make,” Krenzer explains. “As long as you stay in that thirty-three-foot-wide beam, it keeps the laser where it belongs as you move up and down.”
After a 3D model of the field was created, a HiPer Lite+ hand-held rover unit with a reader was set up along with the Case dozer equipped with the 3D machine control system. Although this enabled the equipment to achieve 5/100ths to 7/100ths vertical control, which was fine for the base material, Young needed tighter control for sub-base and remaining layers. The millimeter system was set up to allow 15 feet of elevation change each way from the center.
After calibration, the Topcon GPS+ technology that utilizes signals from both the American GPS and Russian Glonass satellite systems obtained 1/100ths to 3/100ths vertical error with the combination rover-dozer system. That worked especially well on the home-base side of the field where single constellation satellite coverage was limited due to skyline obstruction, Young said.
“GPS control using signals from a single system of satellites is not always used on athletic fields,” Krenzer says. “Because Topcon has the millimeter enhancement and the use of GPS and Glonass satellite signals, which allow plus or minus two millimeters of control, we were able to demonstrate to Clark Companies that 3D GNSS can be used in the installation of playing surfaces that demand special attention and equipment.”
A Line DriveAfter pulling up the AstroTurf, Young discovered it was “old style.”
“It was a shock pad with holes in it,” he explains. “And under that was porous pavement that drains vertically. Then there was a drainage system under that.”
Wanting to use the existing drainage system, Young cut the stone base out and put in a 2-inch drainage layer of pea stone. Eight inches of sand covered the stone so the natural turf could grow. All this changed the grade, he said, making the original asphalt warning track (the strip adjacent to the sod that warns players when they are approaching a wall or fence) level all the way around.
“That is what complicated the grading plane,” Young says. “There were grade changes made when they moved from the AstroTurf to the sand base turf. It had to have a little more pitch on the sand base than on the old asphalt.”
The HiPer Lite+ hand-held unit provided a benefit Young did not expect. “It had a little C card with it, so I was able to quickly install a map of the stadium on it,” he says.
“I was able to plot all my irrigation boxes which are buried in the warning track in such a way that you don’t really know where they are. I was able to identify drainage clean-outs and also locate all the sprinkler heads. The HiPer Lite+ told me the elevation, and that allowed me to put a tag where a clean-out quick coupler or an outbox was located.
“When it came time to give all that information to my CAD guy in the office, I simply downloaded the information from the C card, and he put an overlay on the drawing so the add-fill was done as we went along. That saved a lot of time.”
Not only was it a timesaver, said Admar’s Krenzer, “if they ever have trouble with the irrigation system--for instance, a leak or broken connection--they can take a HiPer Lite, go back out in the field, put the Flash card in the data collector, bring up the files and literally walk to a point within an inch of where the connection is.” He adds, “That’s permanent information always available now or at any time in the future.”
A Home RunDespite the many predevelopment obstacles that threatened the target date, the crew came in ahead of schedule. “We started the project in the first week of September 2007--and that included removing the old AstroTurf, removing the blacktop and removing the subgrade--and actually laid sod the first week in November,” Young says.
Had it not been for the ability to “go to bat” with the combination of surveying technology made available to Young, the conditions of the Alliance Bank Stadium project would have demanded that the work be done the old-fashioned way--lasers, string line and stakes. “That combination of the varying technologies saved me at least a week and a half and maybe even two weeks,” Young says. “It also saved me a lot of manpower. That translates into real savings on the entire job.”