LIKE VAMPIRES, runway resurfacing teams live in a twilight world. They work frantically through the night, then return to their compounds as the sun comes up.
And, apart from the gradual creeping of the new surface, they leave no calling cards. Not a stone is left on the asphalt by the 6am handover.
For the team members, days are lived back to front. 'I get home after a long night shift and all I can face is cereal, ' says David Bishop, pavement team project supervisor with airport operator BAA. 'I wake up in the afternoon craving curry.'
The 220-strong BAA pavement team carrying out the rehabilitation of Heathrow's northern runway has nine months to train stomachs to this nocturnal existence.
Under international aviation rules runways have to be resurfaced periodically according to their condition. The north runway was last resurfaced in 1989/90. The resurfacing also gives BAA the chance to upgrage the runway to take the new Airbus super-jumbo.
The team is working five nights a week, from Sundays to Thursdays. The military precision of the schedule should allow them to be released by the October completion target.
The entire procedure will be repeated next year, when the southern runway is resurfaced - adding a further £20 million to the cost.
Heathrow has two runways and, with 1,250 flights a day, hands them over sparingly for construction work. The pavement team is squeezing its envelope into seven-and-a-half hours, when all air operations are transferred to the southern runway. In that time (for the nights when the base course is laid), the runway is planed out, base course laid and rolled for a distance of 70 m a night. Not a minute can be lost.
Two variables threaten this operation:
the weather and plant breakdowns. And throughout the day the project is kept ticking over with an eye on both.
Plant mechanics check the equipment and the team gets regular weather updates. By 7pm, having checked with Air Traffic Control that the runway can be released for work, the team has decided to start batching up for asphalting.
'We've had some unlucky nights, ' says Mr Bishop. 'One night we decided not to asphalt, expecting atrocious weather. In the event, Hayes was flooded half a kilometre away, but not a drop fell on the runway.'
But the night Construction News spent with the pavement team was a balmy summer evening, the kind of conditions that are perfect for the job.
A sense of anticipation builds before the team takes possession of the runway at 10.30pm. In the nightly planning meeting at 9pm, the project leaders pore over a map of the runway, which covers the long table. They check the weather, mark crossing points and confirm traffic arrangements.
For safety reasons, the civils (see box, opposite) and asphalt teams are kept in two separate compounds to the north and south of the runway. By 10pm, both are lining up on the taxiway, lights flashing. Leaders - airside operations cars which will guide them on to the runway - circle restlessly in front of them.
'It's a bit like the Wacky Races, when they all line up, ' project manager Duncan Pickard, of Turner & Townsend, says.
Mr Bishop's car is observing this activity on the taxiway, with two radio channels blaring. One is for the air traffic control tower, the other for airside operations. He is also connected by radio channels to the civils and asphalt teams.
'You learn to tune in to the important things, ' he says.
Mr Bishop is unflappable. Calmness, he believes, is what gets his hand-picked team through the night. 'Every night is a project in itself. I always start with the end goal and plan backwards.'
It is 10.30pm. Air operations gives clearance. The runway lights go out. And they're off. First is the truck carrying a giant white cross with high-intensity bulbs, which races to the eastern end (the direction from which the aircraft are landing this evening). The cross is hydraulically raised to show passing aircraft that the runway is closed.
Then, two traffic management teams, working in opposite directions, start blocking off the taxiways with cones and barriers. Within 10 minutes, the runway is closed.
The gangs start trooping out, bringing their own lighting vehicles. From the civils compound come the concrete cutters, pit raisers and lighting engineers. From the asphalting side, the planers are brought out on low loaders, which will later return for the pavers and rollers. All vehicles are moving at the self-imposed maximum speed of 30 kph.
At just under 4 km in length and 50 m wide, the runway swallows up the plant.
In the dark, it is easy to lose sight of the 2 m-wide planers. Little wonder that the pavement team operates a system of signing out tools with each worker, counting them back at the end of shift.
Gerry Fitzgerald, surfacing manager of Lafarge, stands watching the planing. He keeps in radio contact with the batching plant, to check that enough asphalt is being mixed to keep the work flowing.
Lafarge usually mixes 800-840 tonnes of asphalt a night, but tonight the team is cranking up for 900 tonnes, with a target of laying 90 m of runway.
'The thickness of the asphalt we lay determines the length. Today we're targeting 90 m, this is unusual, we usually aim for 70 m, but as the team gets more experienced, we're maximising output and pushing a bit harder, ' says Mr Pickard.
The asphalt team has been batching up since 8pm, at the rate of 110-120 tonnes an hour. 'If the plant breaks down close to the end of the job your heart goes into your mouth, ' he says. 'We can't leave any ramps, ' says Mr Fitzgerald.
Two fitters are on site every night to prevent this horror. The team also has a local crane company on 12-hour nightly call out, should disaster strike.
'If the planers have a hydraulic failure, the only way of moving them out is lifting them, ' says Mr Pickard. 'Luckily we haven't needed the cranes yet.'
Precautions are also taken on the asphalting side: once the planers get to the half-way point, they stop for about an hour to ensure that there is enough asphalt to cover the area already planed.
'We ensure that we never plane out a bigger hole than we've got asphalt to put in it, ' says Mr Pickard.
The team also tries to plan against the second fear - that a sudden deterioration in the weather could halt operations, leaving them with several hundred tonnes of unused asphalt. On these nights, asphalt is laid in the less crucial shoulder areas if the weather does not look promising. So far, the maximum wasted on any night has been 20 tonnes.
Eight lorries work with the planers, removing the waste material which will be recycled and used for road base, and 16 are assigned to asphalt transport.
From 11.30pm they are lining up waiting on the taxiway. On average, base course laying starts at 12.30pm, as the planers, who have been moving longitudinally, reach the half-way mark.
For Mr Fitzgerald, the most critical time is 3am. 'We need to know that we still have enough material to complete the job, and the plant is still going, ' he says.
The final asphalt is laid by 4.30am, and the rollers continue to work for a further 45 minutes. But at 4am, the clean up process kicks into action. Plant and labour is gradually cleared to the north shoulder.
Each team is responsible for clearing the section on which it is working.
A checker team from BAA carries out a preliminary inspection of the runway at 4am, and will return after the final sweep at 5am. This is when 12 sweepers meet at one end of the runway and move forward in line.
Mr Bishop, who has a short debriefing meeting to attend, is the last of the pavement team to leave the runway at 6am. He is stopped by one of the workers on the way out.
'Do you know what time they will be testing Concorde?' he asks. Mr Bishop looks apologetic. 'It's about 10.45am. And yes, your house is directly under the flight path, ' he says.
The worker pulls a face: 10.45am, the time when Heathrow Airport is in full swing, but all good runway resurfacers should be in bed.
THE CIVILS team installs the runway centre lights at a safe distance from the asphalting operation and works to a different rhythm.
The team starts work as soon as the runway is handed over and must complete its work by 2am, leaving time for the concrete to cure.
The nightly target is 16 lights a night, while separate gangs raise the pits for cabling in the shoulders of the runway.
The teams cutting out the pits and cores for the lights are breaking into newly laid asphalt, and have to cut as precisely as possible.
'We take as much care as possible and do a lot of hand breaking of the asphalt, ' says Declan Davis, production agent for Amec.
The team is using pavement quality accelerated (PQA) concrete developed by Amec. It achieves a compressive strength of 25 newtons in four hours.
'We crush cubes at 4am. If the concrete has reached a strength of 18-19 newtons, we know we'll be okay for a 6am handover, ' says Mr Davis. 'We bring in heaters if it is cold.'
The concrete has to be placed within 20 minutes of mixing. 'It has to be carefully controlled and placed. You need the right people to do the job, ' says Mr Davis.
Nearly 1,500 new lights are being fitted into the rehabilitated runway area.
Project: Rehabilitation s northern runway Cost: £20 Project manager: Turner & Townsend/ BAA Design: BAA Principal contractor: Amec Capital Projects Asphalt works: Lafarge Aggregates Electrical works: ABB Light installation: Concrete Cutters Pavement markings and grooving: Jointline Surveying: Crucial