According to recent reports there are over 21,000 landfills across England and Wales. Of these over 1,200 are categorised as containing hazardous waste and a further 7,000+ contain industrial waste.
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The records of former landfill sites are not detailed but it is known that some of the hazardous waste sites are now under farmland, greenspace and even housing. There are a variety of problems associated with landfills, particularly older sites, as they have not been lined, which leaves dangerous substances free to leach out of the ground and contaminate the surrounding areas.
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SUMO’s specialist engineering department uses a wide array of geophysical equipment to obtain the best information about your site, whilst working to your budget.
Step one
For large sites, SUMO would use an Electromagnetic Ground Conductivity system to sample soils to a depth of 4m. This is typically enough to penetrate through any caps or membranes which may be present on site. Survey collection is quick and efficient, meaning large sites can be investigated swiftly and cost effectively.
As most landfills contain a significant number of metallic debris, we would expect to see an increase in the ground conductivity of the areas. For example, the ground conductivity data in the plan below shows a clear definition between the boundary of the landfill and the in-situ ground on site.
Above : Identifying a concealed landfill on a ground conductivity contour plan.
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A gradiometer survey can also help with identifying ferrous features within the ground and areas of up to 10ha can be covered in a day with our ATV towed systems.
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Step two
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Once the Ground Conductivity survey has established the approximate extents of the landfill, we work with our clients to establish what extra information, if any, is needed. Ground Penetrating Radar (GPR) may be able to establish the depth of cover to the landfill, as well as a more precise location of the boundaries.
Above : GPR data showing depth of landfill which has been capped.
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An additional technique, Resistivity Imaging, can penetrate depths of 30m+ providing information to help determine the horizontal extent of the landfill and therefore approximate volumes.