Investigating urban and brownfield sites for development

Brownfield sites are preferred by local authorities and regulators for redevelopment. However, many contain a variety of hidden hazards that can pose significant risks for developers and costly delays to the project. Geophysical techniques can provide a useful tool in the investigation of brownfield sites by reducing the risks, with rapid site reconnaissance surveys being utilised to characterise subsurface features prior to any intrusive investigation. With rapid data collection rates (up to 2 ha daily) compiled with specialist data processing techniques, preliminary results can usually be offered at the end of a survey, providing an invaluable tool in the geoenvironmental investigation of the site.

Mapping underground structures

Geophysics can be used to detect and locate a range of buried underground features. These range from recent features such as building substructures, basements and tunnels to historic structures such as culverts, buried air-raid shelters (see case study) and archaeological remains.

Locating buried obstructions

Electromagnetic (EM) mapping is used to offer a quick screening tool, producing site-wide rapid characterisation. We can clearly highlight potentially problematic ground conditions and areas potentially containing buried foundations, utilities and storage tanks.

Mapping the extent of contamination

Mapping variations in the electrical conductivity of the subsurface across a site can highlight anomalously conductive targets such as metallic tanks, pipework and any ground contamination. Although pure water is generally not a good conductor of electricity, groundwater – especially contaminated groundwater – contains dissolved compounds and ions that can greatly enhance its ability to conduct electricity.

Locating buried drums and tanks

Encountering unknown buried objects can significantly increase the cost of developing a site. Geophysics can be used to search for buried features and to reduce the risk of finding unforeseen features during development. Drums and underground storage tanks present as highly conducting discrete features in the ground because of their metallic construction. Their location and depth can generally be detected by time domain EM (TDEM) and ground-penetrating radar (GPR) methods. Plastic tanks and other associated infrastructure can also generally be detected by GPR techniques.

Other geophysical survey applications

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RSK Geosciences is part of the RSK group of companies

The RSK group is a leading integrated environmental, engineering and technical services business offering bespoke end-to-end solutions to a variety of sectors. Headquartered in the UK but with an established presence throughout Europe, Africa, the Middle East, Asia and Australia, RSK helps organisations around the world achieve their business aspirations in a sustainable and efficient manner.