28/07/2011 10:48 BST | Updated 27/09/2011 06:12 BST

London 2012 Olympic and Paralympic Games: How green are They Really?

London topped Paris to win the Games in 2005 with a promise to deliver the greenest games ever. Yet how can an event with 10.8 million tickets which mobilises more than 17,000 athletes, 20,0000 journalists and countless spectators from around the world possibly be green? With one year to go until the Opening Ceremony and the last major sports venue handed over yesterday, it's a timely moment to take stock of London 2012's sustainability agenda.

London's organisers have tackled sustainability in its broadest sense, with the economic regeneration of some of the city's most deprived neighbourhoods at the heart of its Olympic programme. Located in a post-industrial area which served the city's busy docks until the 1960s, the east London site of Queen Elizabeth Olympic Park housed a mix of small industries and community activities prior to the Games. Although the heavily contaminated 200-hectare site was a backwater, criss-crossed by the Lea River and utility and transport infrastructure, it was served by excellent transport connections, the first prerequisite for a green games.

The site was scraped clean and more than 200 buildings dismantled. A pioneering soil cleaning operation processed over 1 million cubic metres of soil. Britain's horticultural prowess will be on display in show gardens on the main Olympic concourse, but the majority of the park has been designed as a haven for wildlife and to mitigate chronic flooding. The hydrology and biodiversity of the Lea River valley were the starting point for the design of an ecological parkland which will result in a park almost the size of Kensington Gardens when the Games are over.

Environmental thinking has permeated every aspect of the London 2012 programme, from infrastructure and venue construction through to staging the Games. A site-wide district heating networkwill offer an efficiency of approximately 20% over the conventional approach of separate mechanical plant rooms in each venue. Most far-reaching has been London 2012's relentless preoccupation with 'legacy' - what will happen after the six week period of the Games. In an Olympic first, a legacy masterplan for the site was developed alongside the plan for staging the Games even prior to winning the bid. In Sydney, widely accepted as the greenest games to date in 2000, legacy planning began only well after the Games were over.

London was determined to build new venues only when they could be justified by a clear longterm use. Stretching environmental targets, monitored quarterly, were established for all new construction. The Olympic Stadium is by far the lightest ever built, using a quarter of the steel of Beijing's Birds' Nest, and was designed to shrink from its 80,000 seat capacity for the Games to 25,000 seats afterwards. The Aquatics Centre has two temporary wings which mean that it can accommodate 17,000 spectators for the Games, but this will reduce to 2,500 afterwards.

Temporary and existing venues are being used wherever possible. Temporary stands will host beach volleyball at Horse Guards parade where 3,000 tonnes of sand will be laid opposite St. James Park. Greenwich Park will be transformed to host equestrian events. Wimbledon will host tennis, Lords Cricket Ground archery, and on it goes.

This is not to say that all has been smooth sailing. Disappointments are inevitable when ambition is high. A proposal for a large scale wind turbine had to be dropped due to changes in EU legislation. Zaha Hadid's signature Aquatics Centre could have been leaner had sustainability driven the brief at competition stage, but this building was commissioned prior to winning the bid as a promise to east Londoners that the Games would bring them a community swimming pool as a longterm asset.

One of London 2012's main messages is that if sustainable thinking is integrated early, low carbon design can be delivered without additional costs. This is most evident in the Velodrome's graceful lightweight cable-net roof structure, which shaved 20 weeks off the programme and £1.5 million off the budget. Bespoke lighting masts developed with Philips for the Olympic concourse incorporate a PV panel and a wind turbine. And the PVC industry, long a bugbear of environmentalists, has been pushed to develop non-toxic phthalate-free products, which are being used in the stadium wrap, the Aquatics Centre stands and the Water Polo Arena. When architects and engineers work together with contractors and product manufacturers early on in a project, both cost savings and innovation result.

The burning question is how all this will impact the lives of east Londoners in the longer term. The recent findings of the UK National Ecosystem Assessment recognised the economic value of the natural environment. It is certain that Queen Elizabeth Park will be a tremendous asset for east London. Careful programming of park activities, particularly in the fallow period immediately following the spectacle of the Olympic Games, will determine whether it is also an asset for east Londoners.

Yet clearly a park and new sporting venues alone do not a sustainable community make. Ongoing investment in affordable housing, employment training and job creation, and improved schools and health facilities are needed to ensure that London 2012 leaves behind a vibrant and sustainable community in London's Lea River valley.

London 2012 Sustainable Design: Delivering an Olympic Legacy by Hattie Hartman will be published John Wiley & Sons in October 2011