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A new tool for investigation of contaminated sites: pre-remediation volume assessment of subsurface structures using a multi-method approach

Abstract:

Zurich Oerlikon has established itself as an exten-sive industrial site close to Zurich city centre. New factories were built in the open countryside and inactive sites were left behind. As long as these sites are not contaminated they can be revitalised economically. With a size of 61 hectares, Zurich Oerlikon is the largest urban reintegration and development project in Switzerland. Unpredictably high costs for site investigation and, if needed, for remediation, justi-fies the advancement of site investigation strategies as well as development of new, more effective in-struments. This paper presents a field study made to implement a new site investigation approach. The task was to investigate the stratigraphic se-quence of the test site and to quantify the volumes of undisturbed subsurface structures and the infill. Based on this data, the volume could be defined and the excavation costs could be calculated. In a further project phase, a chemical analysis will be integrated to assess type and amount of contami-nation. A main aim of the study was to cross-validate different geotechnical and geophysical methods to develop a quick and reliable investigation tool. For this purpose, five Cone Penetration Tests (CPT) and fife drillings were made. It was demonstrated that CPTs are useful to optimise the number of drillings but could not replace them all. Additionally, two geophysical methods for tomo-graphic site characterisation were used. A multi-electrode array measured the electrical resistivity allocation from the surface. Borehole positions were selected to validate the data, and cross-hole-radar measurements were performed between these boreholes. The radar image was compared with the electrical resistivity tomogram and cross-validated with the borehole profiles. The measurements provided a quick and reliable tool to image the subsurface and place the bore-holes in an effective way. The results of these four technologies showed a high degree of similarity and allowed a detailed image of the subsurface. The created image led to a calculation of bedding volumes and excavation costs.

Authors:

Wotschke, Peter and Friedel, Sven and Hermanns Stengele, Rita

Index Terms:

Soil; contaminated sites; SoilGroup; ClayGroup; Friedel, Sven; Hermanns Stengele, Rita; Wotschke, Peter

Further Information:

Date published: 20.06.2003