| Surface electrical resistivity successfully defined brine contamination within a glacial drift aquifer in western Michigan. The study site is in a residential area of eastern Ottawa County, in the Walker Oil Field. A Schlumberger array with a maximum current electrode separation (AB/2) of 316 meters (1037 feet) was used. It was possible to detect geoelectric layers to about 30 meters (100 feet) below ground level, with the maximum current penetration of about 1/10 (AB/2). On occasion, thick surficial clay precluded detecting deeper geoelectric layers. Through use of the INVERS computer program, fifty vertical electrical soundings were interpreted and correlated with geological, geophysical and water quality data. Low resistivity zones were identified on several geoelectric sections within the glacial sand aquifers adjacent to water wells in which relatively high levels of chloride and specific conductance had been detected. The conclusion is that these low resistivity layers represent groundwater contamination zones. |
