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A SHINING FUTURE

GEOENVIRONMENTAL ENGINEERING

Due to the decline of the British steel industry in the late 90s, many production facilities have closed. A West Midlands site is being spruced up to allow redevelopment.

Derelict steel factories provide property developers with a prime opportunity.

This brownfi eld redevelopment can make room for residential or business accommodation. But the former industrial use of the land leaves behind a range of problems that require an in-depth study of the ground and its surroundings before any such plans can be pursued.

One such site is the old Corus steel works at Tipton in the West Midlands. This 6.1ha site is now owned by David Wilson Homes and is undergoing intensive remediation.

GRM, a Midlands based geoenvironmental and structural specialist, is overseeing this work, which will ultimately lead to the building of more than 250 new homes on the site.

Demolition of the old steel works, which was a well known local landmark, began just before Christmas last year, with GRM supervising the removal of all substructures and contaminant sources such as oil storage tanks.

GRM director, Chris Jerram says:

'The site has a number of ground hazards that we needed to investigate and provide solutions for. We have been given a full geotechnical, environmental and structural remit.'

Of primary concern was the possibility of the presence of extensive hydrocarbon and metal contamination at shallow depths, potentially posing a risk to end users and to controlled water.

The fi st phase of the project involved excavating 45 trial pits to assess the near surface ground conditions.

In addition, 30 boreholes were drilled up to a depth of 50m, to determine the presence and concentration of contaminants, as well as the hydrogeological and geotechnical properties of the soil.

To supplement these exploratory holes, GRM used a cone penetrometer fi ted with an infrared probe to detect the presence of hydrocarbons in a further 70 locations. The holes, of up to 15m, also allowed the base of the made ground to be accurately profiled.

The investigation revealed deep made ground across the site that was contaminated with heavy metals and with extensive hydrocarbons.

Leaking storage tanks were the most likely source for the latter.

GRM calculated site specific action levels and remedial targets for the hydrocarbons and designed a capping layer for use within garden areas of the new development.

Remedial targets to protect end users from the hydrocarbon contamination have been compiled by the company's environmental team, using the Contaminated Land Exposure Assessment (CLEA) model.

Testing and risk assessment, using the Environment Agency R&D P20 model, was also carried out to determine the risk to controlled waters.

Up to 50,000m of hydrocarbon contaminated soil will require remediation, using a combination of both insitu and exsitu bioremediation techniques.

An element of the hydrocarbon contamination is present as free product on the perched groundwater present within the made ground.

Site workers will remove this by constructing interception trenches where groundwater will accumulate.

The GRM structures team will design the foundations for the development, which will get a full depth vibro-replacement ground improvement scheme.

Meanwhile, the firm's inspection team keeps a watchful eye over the Tipton site.

Construction manager, Hywel Tidley says: 'If a site manager has discovered some dark material that has a foul odour to it, we are there to sort it out.

'We are linked to GRM's team of technical ground investigation and structural planners, who can provide answers.'

The ground investigation and remediation project at Tipton is part of a multi-million pound redevelopment scheme.

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