Delineation of contaminant zone through electrical imaging technique

Electrical imaging technique has been found to be a powerful tool to deline ate sub-surface contaminated zone, when there is sufficient resistivity con trast. Electrical tomography (imaging) involves measuring a series of const ant separation traverses with the electrode spacing being increased with ea ch successive traverse. Since increasing separation leads to information fr om greater depths, the measured apparent resistivities have been used to co nstruct a pseudo-section displaying the variation of resistivities, both la terally and vertically over the section. Normally, the pseudosection contai ns geometrical effects, geological noise and the distorting effects of near -surface lateral changes in resistivities, which occur close to the electro des (electrode effects). In order to remove geometrical effects as well as to produce an image of true depths and true formation resistivities, the in version technique is used. This technique was successfully demonstrated nea r Dindigul town, where groundwater was contaminated due to untreated tanner y effluents.