In a critical mill-and-fill application, working midnight to before dawn in excruciatingly tight time frames, two to four Wirtgen cold mills spent weeks removing aged asphalt from the main runway of Ronald Reagan Washington National Airport (DCA) in advance of paving.
With cohorts of workers and Wirtgen Group equipment waiting quietly in the middle of the night, the runway would be released only after the last flight had landed, sometimes as late as 1:30 a.m. Only then -- following runway closure by the tower – would the work zone blaze with light and throb to the sounds of engines starting, machines moving and voices shouting.
In late 2011, Mark-Lang was milling Runway 1-19, plus tie-backs into all adjoining taxiways, a total of nearly 300,000 square yards. The job began in mid-June and most of the paving operations had to be completed by November.
“This job is difficult because most airports have parallel runways, and you can shut one runway down and still have access to the others,” said Charles Boswell, secretary/treasurer. “But here, all three runways intersect each other. In order to do the intersections you have to shut down two runways, and one is smaller and can’t handle commercial aircraft.” As a result, much critical work had to take place after the airport closed.
The DCA airfield contains three runways. Runway 1/19, the main north-south runway, is 6,869 feet. In the 1980s, overruns were added to each end of this runway. The other two runways are Runway 15/33 at 5,204 feet and Runway 4/22 at 4,911 feet. When visited Mark-Lang was removing the intersection of runways 1/19 and 15/33.
“The intersection work requires a hard closure,” Boswell says. “We typically will have from 1 a.m. to 6 a.m. to do the work. It’s got to be open to air traffic by 6 a.m., so we really only have until 4:30 a.m. to do any construction. After that we have to be cleaning up the area and getting off the airfield.”
Every night is different, Boswell says. “This job is not as straight cut as a ‘shave-and-pave’ project,” he says. “We’re basically profile-milling, or fine-grading, the runways. Survey teams check elevations and determine what needs to be cut to place 3 inches of asphalt back on top. As a result we will remove anywhere from 1 inch to as much as 7 inches in some areas, but the majority is 3 to 4.5 inches.”
For this work, Mark-Lang was using a W 2200 with a 12.5-foot fine-texture drum, and a W 210 with a fine-texture drum. At times one to two additional W 2000s with fine-texture drums of Mark-Lang were put into action. Cutting tools were spaced at 516 inches. “This project actually requires the fine milling head,” Boswell says. “Because there are no parallel runways at DCA, they can’t shut a runway down for the duration of the project. As a result, some of the runway that has been milled was left open to aircraft movement. Then planes are actually landing on a fine-milled surface.”
Whether the planes are landing on a fine-textured surface, or on a freshly paved surface placed early that morning, the danger exists that small bits of RAP could be sucked into the intake of jet engines. As a result, Mark-Lang was required to meticulously clean operations all during milling.
“The cleaning operation is very important,” Boswell says. “Every night we spend about an hour and a half using multiple vacuum sweeper trucks to remove all traces of millings from the work areas.”
Asphalt paving by Lagan
Mark-Lang was milling subcontractor to Lagan Construction of Belfast. The $13.9-million project was undertaken by Lagan Virginia LLC on behalf of the Metropolitan Washington Airports Authority.
Lagan Construction is an international specialist in airport rehabilitation and improvement projects and has delivered more than 40 such contracts worldwide, including international contracts at Puerto Rico, Hong Kong, Bermuda, Guyana and the British Virgin Islands and numerous United Kingdom projects.