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Ground Probing Radar (GPR) aka Ground Penetrating Radar is the optimum geophysical method for detecting underground storage tanks (USTs) holding petrol, diesel and other volatiles at service stations, transport depots, oil refineries and other types of industrial sites.
When longstanding sites are redeveloped, problems arise where more than one generation of tanks is present. Before the modern era of strict environmental regulation, when new tanks were installed at a petrol station, the defunct tanks may not have been extracted. All too often the USTs were simply abandoned in-situ still containing remnant petrol or diesel, or infilled with concrete or water.
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Surface features associated with the disused tanks such as inspection covers were removed and the surfacing reinstated, hiding the positions of the tanks. Records of the abandoned tank positions were either lost or never kept in the first place. Without accurate information about their locations, abandoned tanks containing volatiles pose a significant hazard to site workers if accidentally disturbed during construction operations. Rupturing of the USTs may also contaminate the soil or groundwater, exposing the developer to serious legal liabilities. The removal of tanks can also be problematic, particularly where later buildings have been constructed in close proximity or even on top of pre-existing tanks.
Ground Penetrating Radar (GPR) offers a solution to the UST problem. Subsurface Geotechnical have a wealth of experience locating buried tanks on dozens of petrol stations, transport depots, chemical works and military bases. GPR can detect steel, plastic and concrete tanks through most types of surfacing. A typical investigation involves surveying a grid of radar profiles at regular intervals over the site. Where a profile transects a cylindrical steel target such as a cylindrical tank at a high angle to its longitudinal axis, the reflections will be curved or hyperbolic in shape (below), where the GPR signal is reflected off the cylindrical surface of the tank.
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