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Watching the waste line

Terminal 5 Waste management

As part of its environmental programme, BAA has set 'world beating' standards for waste recycling at the T5 construction site, discovers Adrian Greeman.

Construction is a messy business. But at Terminal 5, project client BAA has set up a co-ordinated and innovative programme to remove and recycle waste on an unprecedented scale.

'The chance to apply new methods and techniques in a controlled area is a dream come true, ' says waste consultant Nathan Gray, who is working with the T5 environment team. He is enjoying the job like 'a pig in the proverbial', he adds, to the obvious dismay of the BAA public relations lady. She would prefer a more environmental metaphor.

But 'the proverbial' is what has to be cleaned up. Apart from construction debris there is sewage, food waste from the canteens, office detritus and even dust and mud from road cleaning to dispose of.

Like everything else at T5, BAA has made sure waste is handled by its own team, letting the contractors on the scheme's 155 subprojects concentrate on core work. Apart from efficiency and economy of scale this means better control on a tightly packed and logistically difficult site with just one entry and exit point.

The first task was getting a contractor on board, says Gray, and the tender set stringent requirements, including a capacity to recycle a minimum of 80% of the waste. Despite fierce national competition the job went to a local firm, Sweeney, which has a depot in nearby West Drayton. This helped with other T5 targets of minimising local disruption and transport, and supporting the local economy.

Sweeney has a purpose built recycling plant which sieves and separates waste. 'Magnets pull out metal, eddy currents the aluminium, and residue is shredded and separated by density and size, ' says Gray.

Some rubble goes back to site and scrap is sold.

But separation begins on site.

As part of their contract conditions, contractors sort their waste into skips, for metals, timber, general debris, and cardboard and paper.

'Before we began we investigated industry standards and then set a much higher target, ' says Gray. Construction usually manages about 5% onsite separation so T5 went with 15% and is achieving 18%. 'There is a 50:50 profit share incentive on material above target, ' says Gray.

The process of eliminating waste starts high up the supply chain with removal of most packaging from materials before they get to site. Heathrow runs two logistics centres to receive supplies and deliver them to the controlled airport areas, with reusable crates for final delivery, with stillages for glass. Blocks arrive in bulk with reusable pallets for distribution.

Packaging removal helps with another problem, the key issue of preventing 'FODs' or flying object debris. T5 sits right next to the world's busiest runways and nothing can be allowed into the air or aircraft engines. All skips have covers for this reason.

There is an internal web based clearing house for unused materials, for example a surplus drum of concrete additive or paint, which often would go to tip.

'Another contractor can get them free - the project has already paid for it, ' explains David Nowell, head of BAA's environment team.

On site three dedicated rear-end loaders, which constantly circle the site to collect filled skips, are joined by a number of tankers run by Wokingham Wet Waste. These empty the site's 100 cesspits - it has no main drainage yet - and carry the material to a discharge point into Thames Water's sewers.

With 3,000 workers on site this is a big task. To reduce on-road movements a 400m long pipeline connection to the sewer and a small pumphouse were built to allow discharge within the site.

The tankers also collect mud and washings from the constant road cleaning and dust suppression operations. Two loads daily from the 25km of haul roads go to their own onsite processing station with an oscillating screen filter letting water and fines through to a settling tank and a larger sieve taking out stones.

A hydraulic filter press produces a 'cake' from the fines and the water then goes to the sewage discharge point. 'It is too alkaline to keep on site but OK for the sewers, ' says Gray.

Food waste is another organic disposal challenge. Skips from the five major canteens are collected by Sweeney, which has approval from the Department for the Environment, Food & Rural Affairs to run a sealed composting unit - one of the country's first. Concerns about foot and mouth disease mean stringent conditions on use of the product however; it is allowed for landscaping on the airport only if no agriculture is involved.

All this fits with Heathrow's environmental responsibilities, says Nowell finally. 'We are determined not just to hit our minimum target of matching best practice, but to aim for world standards.'

lNCE's conference 'Minimising construction waste' on 21 October will provide state of the art thinking from leading industry practitioners. Details from www. constructionwaste.co.uk, or tel 020 7505 6001.

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