Resistivity surveying uses in landfill monitoring
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There is always a need for new techniques to use in landfill monitoring. Geophysical surveying encompasses a range of techniques that have potential for use over landfills in detecting landfill geometry and interior characteristics. Three geophysical techniques are gravity surveying, magnetic surveying, and electrical resistivity surveying. Resistivity surveys measure the potential difference between electrodes placed in the ground. The electrodes can be arranged in several different arrays, two of which are the Wenner array and the Schlumberger array.' Resistivity data can then be analyzed using computer modeling software. Two such programs in use for resistivity layered-earth modeling are Veslg and Resix Plus. Resistivity surveys have been performed over Argonne National Laboratory's 800 Area Landfill, along its perimeter, and elsewhere on the Laboratory premises. The surveys performed along the landfill perimeter show a basic three-layer model in which the layers represented are different types of clays and some topsoil. The surveys over the landfill itself are more variable but all have a distinctive very low resistivity layer which may repre sent leachate-saturated refuse and fill. This layer has been demonstrated to move over time and does not appear to be related to metallic debris, according to electromagnetic surveying data. The resistivity surveys performed elsewhere on the Argonne National Laboratory premises show a three-layer model which seems comparable to the models of the landfill perimeter surveys. Hence, it seems likely that resistivity surveying can be useful in monitoring landfill interior characteristics and would prove especially useful for leachate detection. However, resistivity surveying should not be done to the exclusion of other monitoring methods; rather, it is useful in conjunction with other techniques which can confirm or clarify resistivity results.