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Taxiway Resurfacing – A night in the life of Taxiway Alpha

Posted: 11 December 2009 | Derek Provan, Operations Director, Glasgow International Airport | No comments yet

The time, 21.45, the date, 19th October 2009. The project report forecast informs me that the team will take possession of the taxiway at 22.00, one hour ahead of plan. The weather, dry, 9-11 degrees Celsius, with light to moderate winds. Details of the planned civils, electrical and asphalting works fill the pages in minute detail, as time is crucial to this team.

The time, 21.45, the date, 19th October 2009. The project report forecast informs me that the team will take possession of the taxiway at 22.00, one hour ahead of plan. The weather, dry, 9-11 degrees Celsius, with light to moderate winds. Details of the planned civils, electrical and asphalting works fill the pages in minute detail, as time is crucial to this team.

Tonight they will continue to resurface the alpha taxiway and replace the airfield ground lighting system (AGL) that lies within it, as part of the ongoing investment in our airport infrastructure.

As I enter the contractors’ compound at Crash Gate 1, I am surprised by the immediate feeling of concern and dread that washes over me. As we drive past, swarms of contractors’ vehicles and personnel are moving deliberately and efficiently around us.

As an international airport, airside security is paramount. The security team spend every hour of the day ensuring the safety and security of the personnel, equipment and aircraft that operate on this airfield. Our security infrastructure includes an electronic security fence, thermal imaging CCTV, and security patrols carried out by our security team, police and other agencies both internal and external, up to the perimeter fence. All to ensure the prevention of unwanted intruders, who may wish to cause harm to the people and property that constitute our airport.

Only 18 months ago, terrorists unsuccessfully attempted to detonate a vehicle borne explosive by driving a jeep through the front doors of the main terminal building.

And yet here I find myself tonight with more than 100 contactors’ personnel, all donned in yellow high visibility clothing and some 50 plus vehicles parked along an airside perimeter road, ready to flow onto the airfield.

22.00 – As the last arriving aircraft taxis to its predetermined stand, the project team get the word that the taxiway is theirs. Like a slow motion version of a Monaco Grand Prix, the articulated lorries carrying the huge surface planers, the 22 tonne tipper trucks and a fleet of cars and vans race onto the taxiway.

They travel along the existing perimeter track that hugs the fence line and then along a new bespoke road that cuts directly to the taxiway.

This bespoke road has been created to reduce travel time for vehicles accessing and egressing the site, to ensure productivity is maximised.

The team now has six hours to lift and relay 120 linear metres of the 22m wide taxiway before the first wave of departures in the morning.

On top of this the team must also remove 10 to 12 centreline lights and replace with a Pyrapatch (rapid hardening concrete) that will provide a solid base, ready for the installation of the new, state of the art, ADB LED light fittings. These fittings will increase ground lighting brilliancy and reduce energy usage, life cycle costs and electrical loads on other areas of the electrical infrastructure that supports the airport. During the entire project over the next 65 days, 150 LED fittings and some 16,000 metres of cabling will also be installed, along with 1,500 cubic metres of concrete to provide additional taxiway fillets.

22.15 – Already the lighting gantries are in position and the taxiway looks like a scene from a science fiction blockbuster movie, with dishes of piercing white light in stark contrast to the darkness that surrounds them. These lighting gantries will once again ensure a safe operation tonight.

22.20 – All vehicles are now in position and Ferrovial/Langans team are preparing the equipment and detailing tasks in a well rehearsed and clearly familiar manner.

22.25 – A line is drawn across the taxiway where last night’s resurfacing concluded and tonight’s will begin. The reason for this becomes obvious as two transporter lorries deliver the huge planer for it to position itself on the starting line.

22.30 – With a planning width of 2.2m and a lifting capacity of 5-7 tonnes/minute, this 30 tonne machine drops its planning plate directly on the line.

After some final checks and confirmation that the teams are ready, the operator flicks the switch and the machine moves forward purposefully, scraping up a pre-programmed 50mm layer of taxiway surface effortlessly.

As it planes, it throws the planings onto a 6.7 metre long conveyer belt that protrudes at a 40 degree angle from the front of the vehicle.

The planings are then deposited into a truck, moving with perfect synchronicity directly below and in front of it.

As it moves forward, it fills the truck to capacity in just four minutes.

As I look to the convoy of trucks and equipment waiting patiently to play their role in the unfolding drama I start to appreciate why this has a £3 million capital investment price tag.

With the first planer now 40 metres down the taxiway, the second positions itself on the start line and replicates the first, both followed by sweeping vehicles in echelon fashion ensuring that no loose debris is left behind.

Within seven minutes the first 120m cut is complete. Two trucks have been loaded and have deposited their loads and the first planer repositions itself at the starting position ready to cut the second 2.2 metre strip. This continues until all 22m width of the 120m section of the taxiway is fully planed to a depth of 50mm and some 300-350 tonnes of planings have been removed. The entire process has taken only 80 minutes.

23.50 – To ensure a correct bonding to the surface takes place, a lorry deposits a poly-modified bitumen emulsion, with a watery tar like appearance, over the cleaned taxiway before the new surface is laid.

Whilst this tack coat is being laid we inspect the AGL works that have been progressing just off the taxiway surface.

Teams from Holemaster are busy pulling cables through cable ducts that run underneath the taxiway surface. Meanwhile other members of the team cut core holes into last night’s new surface, ready for the fixing of the new LED centreline lighting.

The project also incorporates an increase to the taxiway width at strategic points along its length by laying fillets up to 700mm deep of concrete, all in this simultaneous, synchronised activity.

00.10 – With the surface prepared and the planer and all ancillary equipment now removed, it is now time for the paver which will lay the new Marshall Asphalt (MA) surface. This new asphalt will provide a more durable and homogenous surface than the current stone mastic asphalt.

This 35 tonne paver is capable of laying 4.5m width of surface at a rate of four linear metres per minute, and up to 350 tonnes will be laid tonight.

The paver positions itself at the starting line and awaits the arrival of the tipper truck carrying 22 tonnes of Marshall Asphalt, at a temp of 165 degrees.

350 tonnes have been prepared for tonight’s work, with 220 tonnes in the vehicles ready to feed the paver and another 130 tonnes held in hot storage bins at the plant 15 miles away.

There is a long section of steel running the whole length of the vehicle down one side, with cables and sensors to ensure that a precision of +/- 3mm is laid on the surface below.

As the first truck, laden with 22 tonnes of MA, reverses and docks onto the front of the pavers hopper, the Ferrovial/Langans joint venture pavement team position themselves with rakes at the ready, to ensure a seamless connection between last nights surface and that about to be laid. As they stand stooped and poised at the ready, it reminds me of the start of a marathon with the runners pre-empting the lifting of the starting tape or the firing of the starter’s pistol.

Slowly the paver moves down the taxiway at approximately six miles per hour, leaving behind it a perfect layer of new steaming hot asphalt. As it moves off, the team behind it immediately begin to rake the asphalt carefully over last night’s surface to ensure a seamless joint. One team member approaches with a large sieve filled with a mixture of very fine asphalt and commences shaking it, like a baker sifting icing sugar onto a cake, to allow the fine asphalt to fall loosely over the joint surface.

By the time the team are content with the joint covering, the paver has travelled some 20 metres.

One of the team climbs on board the 14 tonne, three pin dead-weight roller to compact the new surface, rolling backwards and forwards, firstly over the joint to ensure it is almost invisible, then progressively following the paver down the newly laid strip of taxiway.

Again, as the three wheeled roller heads down the taxiway, another roller, the pneumatic tyre roller, is started for action.

In front of it is laid a large salvage sheet, which is smothered with vegetable oil. The oil ensures that there is no disruption to the surface from the pneumatic rubber tyres. This roller will knead the small stones even closer together to ensure a strong close surface, reducing risk of surface breakout in future. Once complete, the last roller, the 10 tonne Tandem roller, makes a few slow passes over the surface to remove any final roller marks and provide the surface with a final polish.

As the temperature drops to the forecasted nine degrees Celsius, the process of laying, flattening, kneading and polishing continues for another four hours.

The surface must be complete by 04.15 to ensure that it has the required strength for the first departing aircraft in the morning.

05.00 – With the new surface laid, the airfield duty manager attends the site for inspection and handover prior to morning operations.

With sign off complete, the clear-up begins, and all vehicles and equipment prepare to leave the airfield for another day.

05.33 – the airfield is handed back to airfield operations and 20 minutes later the first aircraft taxis along the new surface, oblivious of the operation that has just ceased.

Tonight, in just seven hours, 350 tonnes of old taxiway has been lifted and transported from the airfield in 15 trucks. One hundred and twenty metres of new taxiway, consisting of 350 tonnes of asphalt, has been laid, along with 500 metres of AGL cabling and 12 AGL cores cut and filled with rapid hardening concrete, awaiting the final fitting of the new LED, AGL lighting system.

As the new day dawns I am left feeling impressed by the efficiency of the teams that I have just witnessed; in their effortless ability, to not only work in their respective areas of expertise, but in their ability to work seamlessly with each other, in challenging working conditions. Once complete, the taxiway will host around 1.5 million taxiing aircraft over the next 15 years.

I think back to that first feeling of concern and dread as I entered the contractors’ compound at 22.00 last night and how the efficiency and professionalism of what I have just witnessed has significantly reduced those concerns.

This was however only day 32 of a 65 day project and tonight’s works will form the content of daily report Number 32.

Tomorrow night this well oiled machine will commence once more, and then again until the project is complete.

Another chapter in the life of an operational airfield.

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