“What people have to understand is, it’s a week’s worth of work done in 48 hours,” says Galliford Try senior project manager Craig Lennon.
Lennon was speaking to New Civil Engineer after another gruelling two-day stretch overseeing the laying of up to 13,000t of runway resurfacing material at East Midlands Airport.
The resurfacing requires up to 800 workers at anyone time, with about 30 asphalt wagons running constantly. Managers watch the weather forecasts like hawks.
Meanwhile, aircraft are in a holding pattern above their heads, waiting to touch down and unload cargo, with every extra second costing money. “It can be stressful. All risk is related to the 48 hour window of time,” Lennon says.
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This 50,000t, 2.9km resurfacing assignment has been completed in seven 48-hour possessions, which Galliford Try claims is a UK-first.
On an average day, East Midlands Airport is busy. It operates 24 hours a day, hosts 4M passengers annually and is the UK’s busiest for freight. Each year it handles about 300,000t of freight, with UPS, DHL and Amazon some of its largest clients. Compare this to when it opened as a decommissioned Royal Air Force base. “Castle Donington Airfield” as it was known in 1965 handled 114,000 passengers in its first year.
In future, a massive development nearby is likely to spur further growth at the airport. The East Midlands Gateway project will create 560,000m² in new distribution and storage buildings, with a rail terminal. This inland port would link road, air and rail, with up to 16 trains per day. The Gateway is far from getting planning approval, but a bid has been made to buy the land needed for the scheme.
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And with other infrastructure developments already on their way for the region – High Speed 2, Midland Main Line electrification and smart motorways to name a few – the impetus for future-proofing the runway is clear.
Discussions first began in 2013, four years after the airport’s last resurfacing was completed. But scheduling the work in the traditional manner – every night, over a few weeks – would have impacted the airport’s freight flights, which operate at night. So after negotiations with stakeholders – airlines, cargo operators, ground handlers, caterers – it was agreed to stagger the work over seven weekends from 5 November to 19 December.
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Sub-contractor Colas has supplied such high-output resurfacing jobs elsewhere in Europe. Part of the solution is to use a high performance surface, in this case, BBA (Beton Bitumineux Aéronautique). With BBA, 15% less material is used, compared to a traditional Marshall asphalt. It also produces enough friction with landing gear, without having to cut transverse grooves.
“BBA removes the need for grooving of the runway, which really frees up the programme,” says Colas aviation director Peter Bamfield. “It’s (BBA) up to UK regulations, and it allows us to put large quantities down in a short space of time, lending itself to these weekend possessions.”
“The difference to a grooved Marshall asphalt is you can only lay 10% of your runway, then you have to groove it,” adds Lennon. “Whereas with this, you can do a quarter of your runway at one time. If you were to do this as a Marshall pavement it would have taken months of overnights.”
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Such are the BBA’s structural properties that aircraft could still land safety when the the job was half finished. Not that that has happened in this case. “It’s [BBA] very durable, you could run on binder, which is not something you could do on Marshall,” says Bamfield.
Three mobile asphalt batching plants are required to mix bitumen with materials at about 170°C and pump out the required 750t per hour. “There’s a contingency built into that, so we’re aiming to lay around 500t per hour,” says Bamfield. “In order to do that we need four or five paving machines out on the runway working in tandem in an echelon facility.” The pavers are staggered in a flying-v formation, leading to a higher output and less joints in the surface.
“Having the batching plants on site is a godsend for us… you’re never going to have cool or cooling material that’s difficult to use. It’s always there within 20 minutes,” says Lennon.
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The total 50,000t of aggregate was stockpiled – procured, quarried, manufactured, transported – before the first week, as part of a six month preparation programme, Bamfield says.
New Civil Engineer visited the site halfway through the project, three weekends in. Weekend one 900t was laid; weekend two saw 12,800t go down; weekend three was cut short due to wet weather, with 4,000t.
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An average weekend
- Site gets signed off and handed to contractors 8pm Saturday
- Traffic management head out, covering the 3km strip
- Lighting contractors head out and start removing cables, civils contractors remove lighting pots
- 10pm Colas commences planing operation
- 10am Sunday, surfacing operation starts
- Early Monday, process reverses – civils replace lighting pots, electrical contractors install fittings and commission lights. Site swept and checked
- 8pm Monday, site is signed back over to East Midlands Airport
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For every 48 hour period there are about 2,000 vehicle movements onto and off the runway, including 30 asphalt wagons, 25 planers and further back-ups. Airport security demands that all plant enters and exits the runway area through one small gate.
“Keeping track of people is important,” says Galliford Try aviation director Colin Abbott. The security system works on the Radio Frequency Identification (RFID) system, keeping track in real time of who is on and off site. “It allows you to get a vast amount of people in and out without stopping. And it registers on the system so at any one time we know who’s gone out there and who’s come back.”
The keel section, which is the centre 23m of the runway, was 170mm thick in inlay sections, and 50mm in all other areas. In overlay sections where strengthening occurred, including the two touchdown zones, the runway was skim planed 5mm and then laid up to 160mm in the keel and to the full width. “Obviously when last updated, 17 years ago, aircraft were a lot smaller, lighter,” says Abbott “So this takes into account current requirements for bigger, heavier aircraft, now and into the future.”
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The 1,200 in-runway light fittings have also been future proofed using LEDs that will use 30% less energy, bringing the airport in line with EU standards.
Energy savings have also been made though the compacted schedule. “There’s a saving on plant, because you’ve got such short windows, the cost would be three or four times if delivering over many months,” Lennon says. “There’s also the saving that comes from producing material here instead of hauling to and from site.” And excess material planed off the runway will be recycled into future projects, such as footpaths or car parks.
Seven weekends in the end proved too much time, with surfacing completed over the first five weekends and runway lights reinstated during the remaining two weekends. To boot, the runway was handed back 12 hours early.