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LANDFILL

Delineation of closed landfill boundary

The accurate determination of factors such as the rate of gas or leachate production or the identification of off-site leachate migration problems can present significant challenges to the landfill engineer or environmental scientist. Geophysics offers a cost-effective means of complementing the information available from monitoring wells or gas sampling surveys.

In this example a combined ground conductivity and electrical resistivity imaging survey was used to determine the lateral extent and geometry of a former domestic landfill site located within a quarry near Bristol. On the apparent ground conductivity map areas of highly conductive fill (yellow / magenta) are clearly distinguished from the resistive bedrock (blue / green). Areas of higher conductivity within the fill were later correlated with areas of elevated leachate concentration.

Electrical resistivity profiles positioned using the conductivity data enabled the depth and geometry of the fill to be ascertained. In the resistivity cross-section (bottom) blues represent the areas of low resistivity (high conductivity) domestic fill whilst hot colours represent the underlying electrically resistive bedrock. A thin high resistivity layer observed from surface to a depth of approximately 2.5m is the capping layer.

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