Developing Brownfield Sites

01/12/2020

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

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.

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.

Utility mapping will determine the presence and route of utilities crossing the site. Not only is this a legal requirement before breaking ground, but producing an accurate map of the utility infrastructure during the survey stage will help you determine what needs to be avoided, removed, diverted or re-used once construction begins. This may also determine contaminated pathways taking contaminated liquids away from site and possibly into the public network

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. 

Casual picture of martin Blythe

Martin Blythe,

Director

OJ Health and Safety Solutions Ltd

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