A specialist team ensures that the project has minimum impact on the surrounding environment.
From the beginning of the T5 project, environmental impact has been a major concern, especially for the residents around Heathrow. Without guarantees of strict control on noise, dust, air quality, water pollution and waste, the project would not have gone ahead.
A specialist team was created to monitor and control these and other potential environmental impacts, working both with the design side and the contractors.
David Nowell, who heads the group while its original leader Beverley Lister takes maternity leave, says the five-strong team was drawn mainly from an original Heathrow unit, supplemented by two specialist consultants.
The group operates with both carrot and stick. 'We try to take a proactive stance talking to contractors, briefing, and training their staff and workers' he says.
There are poster awareness campaigns, presentations and practical training at all levels and 'team talk' updates. The T5 newspaper The Site is also mobilised.
Right from the beginning there are discussions with the contractors about how their work will be done and its likely impact.
'Every sub-project - say, building a substation or river diversion in the landscape work - has a nominated environmental coordinator who spends perhaps half his or her time on these issues and liaising with us, ' says Nowell.
Each coordinator must draw up a construction team environmental plan (CTEP) before work begins, assessing in detail how the job is affected by regulations, the law and special requirements set by the inquiry.
Nowell's team must sign off the plan before work can begin.
Periodic audits follow projects to check how they are going, and there is a general monitoring programme throughout the site.
'Dust is a good example. We have monitoring points at 20 places with slides collected weekly and sent for analysis, ' says Nowell. 'If levels exceed threshold, action is taken.'
Surveys of the ecology around the site are also important particularly as there are protected species to think about, both plant and animal.
But specific concerns and residents' complaints must be dealt with too. A vital part of the team's work is to liaise with local authorities, especially Hillingdon, Slough and Spelthorne.
The team also funds an onsite project manager from the Environment Agency, giving it access to valuable advice and planning consultation says Nowell.