Sustainability is to the fore at Heathrow where, under cover of darkness, the south runway is being reconstructed. Dan Rea reports.
Heathrow's southern runway is undergoing an invisible transformation.
Every night, minutes after the last plane has taxied away, 250 personnel and 260 pieces of equipment are lined up ready to start work.
At the green light, they move out in formation and systematically start preparing sections of runway, digging trenches, fitting ducts and wiring lights.
The year long, £30M project includes resurfacing the main 3.2km long, 200,000m 2runway, and there is no flexibility in the operation. At 6am each day the runway must be ready for up to 50 aircraft landings an hour. Every piece of work in the complex schedule must be completed as assigned.
Under the pressures of tight deadlines and high specification, it would be easy to ignore sustainability issues. But client BAA has worked hard to integrate sustainability into all its construction work.
Previously there has been a focus on improving concrete paving techniques because of the vast quantities of CO 2used to produce every tonne of cement.
Now the joint BAA/contractor Pavement Team (see box) has turned its attention to the asphalt paving process, using experience gained last year on the north runway.
When the south runway was due for resurfacing, BAA took the opportunity to strengthen the wearing course for the new generation of very large aircraft like the A380 Airbus. This has meant planing off the top 40mm, then laying an extra 60mm base course before replacing the top 40mm wearing course. As a result, over 2,000 lights and 1,000 pits now need to be raised.
After trials on the north runway, almost 100% of materials are reused. None of the waste concrete or the 17,000t of asphalt planings goes to landfill.
They are recycled on site and used in an approved base course mix in the widening of the runway shoulders and other construction works.
'This saves on every side, ' says project manager Mike Gywn. 'We buy - and therefore transport - less aggregate, and we do not have to truck the planings away.'
Improvements have been made to the batching plant to significantly reduce emissions and make it more energy efficient. Targets have been set to further reduce asphalt waste pre- and post-mixing , to convert vehicles to LPG and run plant on ultra low sulphur diesel.
The Pavement Team's head of performance improvement Andy Delchar says: 'Our goal is no longer just to cut down on energy use, or send less to landfill but, from a global perspective, to address all our impacts.'
As well as recycling many thousands of light fittings, ducts and 150km of wiring materials, all water used in coring, grooving and sweeping is sourced from the non-potable fire hydrant system. Wherever possible aggregates are delivered by rail - more than 44,000 truck miles have been saved to date.
The team is also trying to minimise social impacts on employees, other airport personnel, and the wider community.
Unfortunately working at night is inevitable, as shutting one of only two runways during the day is not an option. This has taken its toll.
'After three years of working nights I sometimes feel like a mole, ' admits project programme planner John Campbell.
The team has done what it can. Although initial resurfacing projects were done over the winter, when there is less air traffic, for the south runway project the client was persuaded to switch to summer, when conditions for workers are infinitely better.
Use of an innovative bond coat during the overnight runway resurfacing work at Heathrow has maximised output while minimising morning clean up operations.
The non-tacky formulation of Gripclean, jointly promoted in the UK by Ringway Specialist Treatments and Nynas Bitumen, avoids the mess associated with conventional bond coat products.
Overnight possessions and early morning handovers mean there is limited time for resurfacing and clearing up afterwards.
'Strong adhesion between layers of asphalt surfacing is essential to overall pavement performance, and bond coats are often used to achieve this union, ' says Nynas Bitumen special products sales manager Roger Dennison.
'Traditional bond coats are very adhesive and often stick to the wheels of site vehicles tracking over them and are trafficked off site. The loss creates untidy surroundings and weakly bonded areas in the finished pavement, resulting in a less durable finish.'
Gripclean was developed in Europe and launched into the UK through a partnership between Jean Lefebvre UK, Ringway Specialist Treatments and Nynas Bitumen late last year.
The southern runway contract at Heathrow marks its debut in the airport market.
The pavement team
The Pavement Team was formed by BAA and Amec in 1995 in line with BAA's policy of developing long term partnerships and integrated teams.
The team has now resurfaced runways at Southampton, Gatwick and, latterly, Heathrow's north runway, enabling lessons learnt to be integrated in a cycle of improvement.
At the Heathrow south runway site, shifts begin at about 9pm, when team leaders from each contractor cram around a huge detailed plan of the runway to confirm what each is doing and where.
The core principle is to tackle achievable parcels of work. Anything started must be finished in time for the asphalt to be laid and cured.
Initially, great caution was exercised in planning the parcels of work to ensure completion. With such short working windows - from 10.30pm to 6am - 'daily' progress could only be slow.
But productivity, measured as tonnes of asphalt laid per night, has more than doubled from 400t at Southampton to the current target of 838t.