DOVER AIR FORCE BASE -- Jeff Habegger has supervised big runway projects before. Not every worker on the massive refurbishment underway at Dover Air Force Base, however, is as accustomed to earning a day's pay while jumbo cargo jets are flying nearby.
"You can tell somebody that's new to the project. When an airplane lands, they all stop," Habegger said, wincing to mimic someone who's been startled. The old-timers like himself? "We don't even hear 'em anymore."
He laughed. "So it's real, yes sir."
It'll get even more real when workers begin tackling the spot where Dover's two runways intersect, he said – when, down to the use of half of one runway, the base's C-17 cargo jets will land and take off directly over their heads. They'll have a 1,000-foot buffer between the edge of the work and the nearest spot where they'll touch down or lift off.
Dover's C-5M cargo jets won't be joining them. Leaders say the larger aircraft are capable of operating on shorter airstrips but that doing so while laden with cargo is risky. So the jets and their crews will spend up to six months operating out of Joint Base McGuire-Dix-Lakehurst, New Jersey.
Due to unexpected delays, that's not going to start until next spring.
The $98.3 million replacement of the base's 9,600-foot north-south runway began in February. Lead contractor Versar, Inc. expected to start tackling the intersection several months ago. Instead, the project has been slowed by unexpected discoveries under the runway as it was being demolished.
Workers uncovered elements of older runways, such as old manholes and electrical work – "almost like a timeline" of the runway's history, Habegger said, adding that some of this was unanticipated. Those had to be excavated. Another unexpected discovery was prevalent subsurface clay. Habegger said clay has a highly moisture-dependent structural stability, and soft areas had to be removed or stabilized so a stable, dense and uniform subgrade could be built.
Poor drainage led to groundwater accumulation, particularly during March and especially, June. The recent heavy rains nearly filled the huge ditches workers dug to emplace new drainage culverts.
"So this is really a project within a project," said Lt. Col. Charles Throckmorton, director of operations for the 436th Operations Support Squadron. "Because we've got to get to what's under the runway fixed before we can get to what's on top."
"You've got to get this piece right because ... we're gonna pave a runway over this thing," said Col. Mike Grismer, commander of the base and the 436th Airlift Wing. "The last thing we need is for ... the ground to cave in."
The project's scale is impressive.
First, the entire north-south runway, called 01-19, had to be torn up; it turned 70 this year, and vexed pilots with its cracked and spalled surface. It also wasn't level with the longer, intersecting 14-32 runway - as much as two feet lower, in long stretches. (The longer runway, other than the intersection, was refurbished in 2008.) Remnants of the small mountains of debris dot the airfield. Much of the material is being run through a crusher plant and repurposed.
"We're recovering all the stone and sand that was in the original concrete, and we're putting it underneath the shoulders left and right of the runway surface itself," said Harry Labadorf, the onsite representative for the Air Force Civil Engineer Center, which issued the contract to Versar and joint venture partner Johnson Controls Federal Systems. It's heavy-rolled multiple times and tested for maximum compaction, he said.
In addition, two sets of drainage culverts that lead from the base and cross under the runways had to be dug up. Each set's culverts, old concrete or metal piping that were heavily silted, are being replaced with stronger, wider box culverts that will give the base far more drainage capacity. A total of 589 segments are being used, each weighing about 40,000 pounds each and lifted into place by a tall crane. It takes as many as 90 minutes to hook up each segment, Labadorf said.
The runway lanes themselves have to be dug out and layered with cement given an additive to eliminate the moisture buildup and runway cracking. "We had to make sure we had the appropriate mix so that would not happen, and this is going to be an enduring runway," said Tim Sullivan, chief of AFCEC's U.S. project execution.
On site, Habegger sometimes has to shout to be heard over the rumble of excavators, offroad dump trucks and bulldozers. He has the job of bringing all the moving parts together - "coordinating all the different subcontractors, materials deliveries, and the different trades," he said. The work currently requires about 75 workers per shift – between 20 and 30 of them, at various times, from Delaware employers, Habegger said.
Coordination is key. Take the concrete. It isn't poured into forms, as it would be for smaller jobs, such as a home's foundation or street curbs. In segments 37.5 feet wide, 2,000 running feet and much as 22 inches inches thick in the areas where airplanes touch down - an example of 10 hours' continuous work - the concrete is set down in a "monolithic pour" using a huge machine called a slipform paver.
The paver is fed by concrete from the on-site batch plant. The plant produces about 10 yards, or a truckload, every 1 1/2 minutes, Labadorf said. That's how often fresh concrete must be trucked over and dumped in front of the paver to keep up with the rate of paving.
The machine has guides that protrude forward and keep the material from spilling off to the side. It continuously but very slowly moves forward, compressing and forming the cement into a smooth, compacted finish.
To further complicate things, the top of the runway isn't flat, but is crowned to allow for water runoff.
During the warmer months, the runway is generally poured at night, when the temperature is in the range of 75 degrees, Habegger said. As the weather cools, that gets reversed. "We need to be around 35 and rising," Habegger said. "And then we have to maintain temperature for the cure."
The amount of concrete that will have been poured borders on mind boggling. About 77,000 cubic yards of concrete has been poured to date, covering long stretches of 01-19, and the taxiways on both ends. That's about 7,500 truck trips from the batch plant to the paver, Labadorf said. The entire project will require about 130,000 cubic yards.
"This is the largest I've done," Labadorf said. "There probably won't be many this large in the near future."
The intersection work will essentially cut the longer 14-32 cut in half. The base's smaller C-17 jets will have enough room to take off and land on either side of the construction. On the northwest portion of the longer runway, fliers will touch down beyond a 1,000-foot safety buffer zone past the construction. The C-17s will also be able to land on the southeast side, in that direction.
The larger, heavier but more powerful C-5Ms can still take off and land on that shorter stretch. "But you can't carry much cargo on it, and it's more risky on a short field like that," Grismer said.
That matters because Dover continues to fly resupply missions to Afghanistan for Air Mobility Command. "I've got the Super Port," Grismer said. "We've got to move cargo around, right?" Dover operates the Defense Department's largest aerial port and provides about 20 percent of the department's strategic airlift capability, he said.
So the base's C-5M fliers will continue flying those missions – but, during the four to six months the intersection work proceeds, they will do so out of Joint Base McGuire-Dix-Lakehurst. C-5M loads will be built at Dover's Aerial Port facility and taken to McGuire via truck, Grismer said.
"This is really the most critical phase," Grismer said. "I want that time to be as short as possible. And I really don't want it to be over the winter ... when I've got ice on the runway and low [runway condition reading] conditions, that minimizes what kind of performance we can get in and out of here."
If bad weather does become an issue at Dover, some Air Force Mortuary Affairs Operations dignified transfers - the return of the military's dead from overseas - could be diverted to the New Castle Air National Guard Base, Grismer said. A "divert" exercise to test out that scenario was held at the base in March.
About two-thirds of the way through the project, as construction moves further west from the intersection, the shorter runway will reopen, allowing for the C-5Ms' return.
For now, the intersection remains open, giving the base's giant cargo jets a single clear path for takeoffs and landings in both directions on 14-32.
The construction delays have put a crimp in the original 18-month plan. It's going to take longer, and cost more. Higher costs can be remedied when they relate to unforeseen site conditions that fall within the scope of the project and are approved for reimbursement, according to AFCEC's Sullivan. While production continues using prior year funding - in this case, from fiscal year 2014 - AFCEC has to go back and get approval to use additional prior year funding to cover those unforeseen conditions.
At the same time, he said, AFCEC has to negotiate a modification of the contract to cover the cost and length of time for the added work.
Even if this is resolved fairly quickly, colder weather will begin to slow the work. Construction activity will continue although all paving work will likely halt, said Capt. Sarah Bergstein, a base spokeswoman. All other construction on runway 01-19 will probably continue, especially on its electrical components, as the runway is getting new airfield lights and navigation aids. Some shoulder preparation and adjacent grounds grading will also likely get done. While the batch plant and field trailer office will remain, individual subcontractors may opt to move equipment that's not being used, she said.
Meanwhile, the intersection awaits. "We're targeting next spring to do that," Throckmorton said.
- Source: http://www.delawareonline.com
Jeff Habegger
Harry Labadorf
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