Developing Brownfield Sites – Asbestos Contaminated Land

A recent report by the Campaign to Protect Rural England reports that as many as 1.4 million brownfield sites could be suitable for development across England.

There is undoubtedly political will for the development of brownfield sites but the issue is the unknown cost of developing the land.

The finding of asbestos fragments in the ground on brownfield sites where factories and other installations were previously demolished has raised the question of contamination and of the real suitability of the land for development.

Asbestos may have been used within the fabric of any previous building such as insulation, cladding, electrical insulation, wall boards and ceiling and floor tiles. It may have also been used in the production activity which took place there such as the manufacture of building products or other products such as brake-pads or fire blankets.

A staged, sequential, logical gathering of data is recommended. This is following a model of land use suitability mapping and analysis

Stage 1 Carry out a desk top exercise

A Desktop study can be built which can then be the primary assessment tool throughout the project.  It would follow the GIS (Geographic Information System) model. GIS software could be purchased and used for this purpose if deemed cost effective. The process would gather data from published historical, hydrological, geological and environmental information.

Data should also be gathered from the local council Brownfields Land Register and the Contaminated Land Register both normally available online

All the information gathered can be overlayed and a picture beginning to be built up of the make-up of the land. Particularly relevant is previous use of the land and the likelihood that asbestos was used as part of the fabric of any buildings or used in any process within the previous use.

It may be that the land purchase can be halted after this stage if major issues are revealed which will financially unbalance the project

Stage 2 – Topographical Survey and Utility Mapping

Further investigation using OS Mapping such as Mastermap gather detailed and accurate information can identify utilities laying beneath the surface and a topological survey can determine ground levels which may be a key factor in the success of the operation.

Stage 3 – Brownfield Reconnaissance (Geophysical & Topographical Survey)

A further, more detailed profile can be now obtained by carrying out a geophysical survey using electromagnetic conductivity to determine and map the physical and chemical properties of the ground. It should look at areas such as soil and groundwater contamination, mining hazards (coal and other mining), radon (natural radioactivity), landfill and natural hazards, including: landslides shrink–swell clays, running sand, collapsible ground, compressible ground and soluble rocks.

It uses the below techniques to gather in-depth data:-

  • GPR (Ground Positioning Radar) – to identify the depth and extents of buried structures (including historic remains),
  • Microgravity – to establish mine shaft and basement dimensions
  • Resistivity imaging – to pinpoint the depth and extent of contamination

These geophysical investigations will provide a clearer understanding of where intrusive investigation and monitoring or mitigation is needed. If buried structures are found the design can be made around them.

Stage 4 Intrusive investigation.

Obtaining samples, drilling bore holes should then finally reveal the extent of any contamination such as asbestos or soil/groundwater contamination and radon gas.

At each stage the investigations can be abandoned if the risk outweighs the opportunity. As the investigations progress through the stages the more likely the project is to go-ahead, therefore the detailed information gathered can then be presented to any prospective Principal Designer for inclusion in the Pre-Construction Information as required by Law.

Asbestos is still responsible for premature death and incapacitation due to asbestosis, mesothelioma and other asbestos related diseases every year in the UK. It is important that in building new homes we are not building new problems for future generations.

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