The application of resistivity and IP-measurements as investigation tools at contaminated sites : a case study from Kv. Renen 13, Varberg, SW Sweden

Abstract: An old industry estate, Kv. Renen 13, is located in central Varberg, southwest Sweden, and is known from previous investigations as highly polluted. Pollution started in the late 19th century with textile manufacturing, and in the 1960´s changed into a precision mechanics industry using chlorinated solvents, primary trichloroethene (TCE) and 1,1,1-trichloroethane (TCA), as well as cyanide and metals. Wastewater was taken out through an es-cape valve to a sedimentation basin, which most likely leaked. With good subsurface conditions for dispersal, both in the sediments and in the highly fractured bedrock, a large area of the subsurface is polluted from contaminants due to the situation at Kv. Renen 13. This thesis investigates the subsurface conditions by using resistivity and induced polarization measurements, geo-physical methods based on different materials’ physical responses to an electrical current. Resistivity (Ωm) is a physical property of the ability to isolate against electrical current. Induced polarization (IP) measures the chargea-bility of a material, i.e. how electrical charges polarize and depolarize when subjected to an electrical current that is turned off after an interval of time. The aim with these geophysical surveys was to create a 3D model of the subsur-face ground conditions. The measurements were made at three occasions, to be able to investigate if it is possible to measure variation through time, and use the method for monitoring of in situ remediation. As a result of the survey, a fracture zone with a southwest-northeast direction crossing the industrial estate, could be identified. This fracture zone was not identified at the estate before and within the zone, there is a possibility of spreading the contamination. Variations in underground conditions through time in the subsurface were measurable using the geophysical methods, and the method shows good potential to be used for in situ monitoring of pollutant remediation. The work is part of the research project TRansparent Underground STructore, TRUST.