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Surface geoelectrics for characterizing ground water protective layers and compacted soil liners
Abstract
In order to prevent contamination of ground water resources used for municipal water supplies, the Wellhead Protection Program was initiated by the U.S. Environmental Protection Agency (EPA) in 1987. In accordance with the wellhead protection program, state agencies along with local water suppliers are required to delineate wellhead protection areas around municipal supply wells and to take appropriate control measures. One criteria cited by the U.S. EPA for defining the boundary of a wellhead protection area is the time-of-travel (TOT) to the well from the ground surface. Surface geoelectric methods provide a cost-effective method for estimating the hydraulic properties of geologic layers or soil liners that define protective properties. The geoelectric scenario of an effective protective layer is generally that of a relatively thin, fine-grained conductive layer overlying a more resistive aquifer. With this type of scenario, the longitudinal unit conductance (S) of the protective layer is often a geoelectrically equivalent parameter that can be relatively accurately determined from a geoelectric sounding. For unsaturated protective layers, time-of-travel can be correlated with the longitudinal unit conductance of the protective layer. For a saturated protective layer, time-of-travel can also be correlated with longitudinal unit conductance or even more accurately to S divided by the longitudinal resistivity, $\rho\sb1,$ of the layer. The federal Resources Conservation and Recovery Act cites hydraulic conductivity as an acceptable criteria for characterizing compacted soil liners. Utilizing relationships between hydraulic conductivity and electrical resistivity, resistivity measurements can be used as a fast and cost-effective method for assessing construction quality. Interpretation of resistivity measurements can be used to map the probabilities that liner hydraulic conductivity is below any pre-construction criteria value.
Subject Area
Civil engineering|Geotechnology
Recommended Citation
Kalinski, Robert Joseph, "Surface geoelectrics for characterizing ground water protective layers and compacted soil liners" (1992). ETD collection for University of Nebraska-Lincoln. AAI9314404.
https://digitalcommons.unl.edu/dissertations/AAI9314404