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COOL THINKING

The collieries of the East Midlands, made famous in the writings of DH Lawrence, are now finding new roles as the sites of shiny new industrial developments.

Transformation of these derelict lands is not always easy, however. Smouldering spoil heaps and large expanses of uneven ground with little bearing capacity are among the challenges.

A team of about 30 environment specialists from Atkins are responsible for improving ground conditions at the 86ha Shirebrook Colliery site. This work forms part of the company's role as design consultant for design and build contractor Webfell.

Throughout the project, which began in summer 2001, Atkins has adopted a sustainable approach, ensuring material on site is reused wherever possible to minimise environmental impact.

The multi-million pound redevelopment forms part of the East Midlands Development Agency's (EMDA) South Shirebrook Regeneration Programme, itself part of the National Coalfields Regeneration Programme.

About 48ha of the development has been earmarked for strategic landscaping alongside 38ha designated for employment use for class B1, B2 and B8 industrial use.

With EMDA already marketing the early plot release areas, the Atkins/Webfell team have had to stay on schedule, with completion expected at the end of the year.

All the parties involved took a strong partnering approach to the scheme, drawing up a 'partners' charter' at the start to confirm their commitment to delivering a successful reclamation.

The team consists of Atkins Environment, Webfell and EMDA as well as the latter's consultant WM Saunders.

The Atkins team, led by project manager Mark Smith, has adopted a sustainable approach to the earthworks and levelling of the land to make it suitable for a multi level business park.

The spoil heaps - amounting to something like 2M. m 3of material - are a loose mixture of coal and colliery waste which contain enough oxygen to permit combustion.

In Shirebrook's heyday, hot metals or ash from the boilers were thrown on to the spoil heaps, probably igniting the fires that have been smouldering for decades.

'When we monitored the spoil heaps we recorded temperatures of up to 350infinityC - so it was quite hot in there!' says Smith, a principal consultant with Atkins Environment.

'We had to investigate the extent of the problem and undertake works to extinguish the burning material.'

The ground clearance team began a slow process in which thin slices of the spoil mounds were taken away to a 3ha clearing area to cool down.

'The spoil material was monitored as it cooled and once it reached an ambient temperature it was reused as fill material within the overall development, ' Smith says.

At Shirebrook, one of the products of the coal and carbonaceous material combustion is red shale, which lends itself to more recycling.

'The red shale has a saleable value in the brick and block making industry, so some of that was removed and fed into the market, ' Smith adds.

The extensive earthworks included general reclamation works.

'Obviously the topography of the site with its spoil heaps does not lend itself to a redevelopment of this type, which calls for relatively flat development plateaux, and the heaps also have poor bearing capacity, ' Smith says.

'The general reclamation aspect of the scheme required turning over all the made ground - or colliery spoil heaps - on the site.

'We had to go right down to the limestone bedrock level which meant anywhere from 2m to over 10m. The material was then re-deposited to an engineering specification appropriate to the multi-level development.'

The Atkins/Webfell team of environmental and civil engineers, landscape architects, ecologists and planners prepared a hierarchy of material classification with the help of risk assessments which defined the soil into three types based on the reclamation and future occupiers' requirements.

The highest quality soil or upper development fill formed the surface layer of the site. It was placed on the lower layer development fill with the final category designated landscape fill.

To date Webfell has only had to remove a very small quantity of material associated with a former sewage works in a corner of the site.

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