Reconstruction of the 14,572-foot Bay Runway at John F. Kennedy International Airport comes about as close as you can get today to an automated construction project, if you just look at the equipment. Milling, grading, and 280,000 tons of asphalt shoulder paving were supported by Topcon automated machine controls, and Gomaco concrete pavers controlled by Leica Geosystems laid 175,000 cubic yards on the runway with no stringline.
Working under a $204-million contract, Tutor Perini Corp. and subcontractor Intercounty Paving widened JFK's Bay Runway (13R-31L) – one of the nation's longest commercial runways – from 150 to 200 feet. They milled off 6 inches of existing asphalt, built new taxiways, reconstructed numerous intersecting taxiways, and did the shoulder work – notably paving an 80-foot wide asphalt shoulder. Tutor Perini, of Sylmar, Calif., topped off the runway with 18 inches of Portland Cement Concrete.
Grade-control automation was essential to satisfying a very tight schedule. The Port Authority of New York and New Jersey closed the runway from March 1 to June 28, while the contractors completed more than 10,000 feet of runway.
Tutor Perini Project Manager Damon Petrillo says the firm bid the job planning to use machine control in all phases. "There is an initial investment in the equipment," says Petrillo. "And we look at it as a no-brainer in terms of a huge savings in time."
At Intercounty, general manager Frank Lizza says the Topcon machine controls slashed weeks from the milling schedule, compared to using staking and manual controls. "We would never have gotten the job done without it," says Lizza.
"The biggest thing that this project benefited from was that we had one central source for the data," says Steve Thomas, a partner at MESH Consulting LLC, Limerick. MESH provided the contractors with a single digital terrain model to guide all of the grade-control and surveying systems on the project. The terrain model is a digitized 3D model of the runway. "We had numerous subcontractors on the project, but everybody used that same data. It was all run through the surveyors for Tutor Perini. They were the keepers of the data.
"When anything was laid out at the site, it was done using our one central model of the site," says Thomas of MESH. "That is not only surfaces, but it also included the horizontal layout of all the concrete joints, all of the light cans involved, and all the striping and pavement markings.
Thomas says the first step in construction was to build a number of new drainage systems. Those systems were all included in the digital model for all of the pipe crews and surveyors laying out the drainage works. Then some electrical systems were rerouted.
The next step was to mill the existing asphalt to exactly 18 inches below finished grade, which meant shaving off about 6 inches. "They were able to take our finished grade model, put that into the milling machines, and without doing any kind of staking or marking on the existing runway, they were able to mill to exactly 18 inches below finished grade," says Thomas.
To handle the milling, Intercounty brought in six Roadtec RX900 milling machines, each capable of milling 12 feet wide. But cutting 6 inches deep created too much vibration for Topcon's Millimeter GPS system to work accurately.
"When we were cutting 6 inches deep, it would vibrate the milling drum somewhat violently at times because of the hardness of asphalt we were milling," says Lizza. "We would have to stop and reset the machine due to the satellite dishes swaying."
The answer: do the milling in two stages, 4 inches first, then 1.5 to 2 inches in a second stage.
For the 4-inch cut, Intercounty ran three Roadtec RX900 milling machines in "RTK Mode" – without the laser cross-reference for millimeter accuracy – and "bulked out" material to -1.36 foot below finished grade. "We decided to come back later with the Millimeter component and profile mill the remaining 1.5 to 2 inch cut, said Lizza.