Meticulous planning has ensured the contractor overcame tricky materials and difficult weather in the most challenging of working environments.
Project: Heathrow Runway Rehabilitation
Client: Heathrow Airport
Contract value: £31m
Main contractor: Morgan Sindall
Lead designer: Amey
Surfacing subcontractor: Lafarge Tarmac
M&E subcontractor: Allied Infrastructure
M&E subcontractor: ATG Airports
Start date: April 2013
Completion date: September 2013
Anyone observing Morgan Sindall senior project manager Tony Heron at work last winter could be mistaken for thinking he had let a childhood hobby get the better of him.
But the hundreds of model construction machines were spread across his desk for a very good reason.
Mr Heron is the man in charge of resurfacing Heathrow’s runways without causing any disruption to passengers at one of the world’s busiest airports.
His team has only seven hours a night to get on the runway yet, due to weather restrictions, work on phase one – the 3.8 km-long southern runway – must be completed between 1 April and 30 September this year.
A typical night shift involves about 200 workers and 150 pieces of kit. The access period, from 10.30pm to 5.30am, has to include turning the runway into a workable construction site – and back again. Planning took almost military levels of precision.
Dinky Toys’ biggest customer
“For a while we were Dinky Toys’ biggest customer,” Mr Heron says. “We bought 1:50 scale versions of every piece of kit on the runway and conducted desktop exercises moving the people and plant around, handing each other paperwork as we went.
“It was a process of refinement and making sure everyone knew what everyone else was doing.”
This was just one stage in a detailed programme of preparation work. Even before the desktop modelling could be done, weeks were spent writing out processes to find the most efficient ways of working. Then there was the surfacing material itself to get right.
“Marshall Asphalt was specified for the project, but the properties that give its strength and long life also mean it is very difficult to lay,” Mr Heron says. “You have to practise to get it right.”
The contract required a coating plant to be set up on site to enhance the quality of the asphalt produced.
“We knew this was a big challenge. Starting anything from scratch at Heathrow is difficult”
Tony Heron, Morgan Sindall
An airside site had to be located and agreed, a number of utilities moved and the ground stabilised. Foundations were required and the plant took two months to erect.
“We knew this was a big challenge,” Mr Heron says. “Starting anything from scratch at Heathrow is difficult. Every person and piece of equipment went through the same rigorous security process as you do when you board a plane.”
Heathrow has an offsite screening facility as well as processes to allow officials to follow deliveries and plant movements.
Get the material testing right
A series of tests ensured the surfacing material had exactly the right make-up for the job.
This started with small lab-produced batches to get the properties right, then small trials to test the plant, followed by batches of up to 100 tonnes to ensure it worked at scale.
Then came trials of laying the material, at which point all the variables become critical.
Development Heathrow senior project manager Andrew Mitchell says: “When we sign off the trial, it is the materials, the people and the machinery. If you change crew then you need to redo the trials.”
On 1 April this year, the southern runway at Heathrow was reclassified for Category I use only in order to allow the works to begin – meaning it was only for use in clear visibility conditions.
This allowed Morgan Sindall to take out the lights on the centre line, ready for the resurfacing to begin in early May.
Design work on the scheme had begun in late 2011. Amey, which acquired a team of infrastructure designers from Heathrow’s former owner BAA the same year, was asked to offer some informal advice on the options for maintaining the quality of the runways at the airport (see box).
“We advised that the best solution was to take off the top 50 mm and put 50 mm of new material in,” says Amey business manager Rob James. “We were later awarded the contract through Heathrow’s Infrastructure Design Services framework and began design work in January 2012.”
While the design for the surface replacement was straightforward, the electrical work underneath was anything but. More than 1,000 light fittings needed to be changed as part of the aeronautical ground lighting system for the runway.
Each fitting has two cables leading from it to a transformer, which is in turn connected to a power substation, taking the total cabling under the runway to 72 km.
“I was sat happily at a progress meeting saying we had finished our work when I was told that LED lights had been approved. We had two weeks to change it all.”
Rob James, Amey
The airport wanted to use LED lighting but regulating body the Civil Aviation Authority had not approved its use on runways and was still evaluating a trial in Manchester.
“We started design work in January 2012 and had to complete it by the June to allow the tender to go out for a contractor,” Mr James says.
“So we had to design using halogen lights. I was sat happily at a progress meeting saying we had finished our work when I was told that LED lights had been approved. We had two weeks to change it all.”
Not only did this mean different light fittings but it allowed a change from 12amp to 6amp electricity circuits, something the airport had been keen to do to cut maintenance bills.
“We had a very fraught month in May 2012,” Mr James recalls.
The rhythm of the night shift
A year on, Morgan Sindall – having been awarded the contract through an OJEU process – had completed its own preparations and was ready to begin the resurfacing in earnest. The runway is resurfaced gradually, with the same routine carried out night after night.
“At 10.30pm, we take control of the runway and the first thing we do is put traffic management in place,” Mr Heron explains.
“With 200 men and more than 100 pieces of equipment, we need to establish motorway-standard traffic management. We also need lighting towers to allow us to work.”
This set-up phase takes an hour before the planing machines – weighing 40 tonnes each – can be sent out. These remove up to 80 m of runway top surface between about 10.50pm and midnight.
“We have a third paving machine on standby and even a sequence where we can carry on with one if two break down”
Tony Heron, Morgan Sindall
A bitumen coating is applied to help the new surface bond, then the carefully created Marshall Asphalt is laid from 12.15am until 3am. The quality of the material produced is constantly checked and conditions monitored to ensure the strict requirements are met.
Handover work begins at 4am and everything must be off the runway half an hour later, allowing the airport’s operations team to run tests on the surface. Ten roadsweepers drive from one end of the runway to the other, followed by people and other kit to check for the slightest debris.
By 5.15am the runway is cleared ready to hand back to air traffic control at 5.30am. The first planes land from 6am and the runway remains in constant use through to the next night.
How to cover emergencies
“Our objective is to hand the runway back on time every morning,” Mr Heron says. “If we take runway surface off we have to be sure we can cover it.
“We have a process where we know we have the asphalt before we plane. If the coating plant breaks down we have enough material to fill the gap.”
Lists of potential problems have been made and contingencies to deal with them created.
“We have a third paving machine on standby in case one breaks down, and even a sequence where we can carry on with one if two break down,” Mr Heron says. “We have worked with suppliers so we can reconfigure the planing machines to get them off the runway.”
As of late July, although there had been a couple of handovers slightly later than 5.30am, no flights had been affected to or from the airport. Work was due for completion in late September, with resurfacing of the northern runway to take place in the same period next summer.
So next time you are on a plane out of Heathrow, remember the role that model construction vehicles played in getting you away on time.
Why the surface needs replacing
Heathrow’s two runways are each used for 477,000 take-offs and landings per year and they are expected to require resurfacing once a decade to maintain performance.
“Every time a plane lands, it leaves rubber on the surface of the runway,” Mr Mitchell explains. “We get a build-up of rubber that means when it rains you do not have the same friction as before.
“We remove this rubber with water pressure but this process can itself degrade the surface. In the winter you get cold and ice, and in the summer the runways reach up to 50 deg C.
“The surface wears out over time. You lose the binder and get down to aggregate. It is possible to get foreign object debris in gaps.
“We identify the need for maintenance and carry this out between 10.30pm and 5.30am when there are no flights. Only one runway is worked on at a time so we always have one open should aircraft need it.”
Tricky asphalt work
You can spend as many months planning a project as you like but the British weather will always have its say.
“It was very cold when we started in April and very hot in July,” Mr Mitchell says. “There were a couple of evenings when we could not lay asphalt due to the temperature.”
The Marshall Asphalt used to surface the runways is a very dense material to withstand aircraft take-offs and landings. This makes it very sensitive to conditions.
Compounding the problem of time lost to extreme weather is a restriction on the amount you can lay the next day to catch up.
Tiny grooves also have to be cut in the new surface every 25 mm to allow water to drain off and remove the risk of aquaplaning.
The freshly laid asphalt must be left for 72 hours before it can be cut – yet only a limited amount of runway can be left without grooves if planes are to use it.