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Institut für Wasserbau - IWS

Selected Topics and International Network Lectures

11:00 Uhr
Philip Binning, Associate Professor in Subsurface Hydrology and Numerical Modelling, Institute of Environment & Resources, Technical University of Denmark

A catchment scale model for assessing the risk associated with point source contaminated sites

Point sources are one of the main threats to groundwater quality. It is essential that remediation efforts are prioritised to ensure that the point sources which constitute the largest groundwater risk are remediated first. Currently, no systematic procedure is available for evaluating and comparing the contamination risk associated with various point sources within a catchment area. Here a simple method is presented that provides the basis for a ranking of point sources according to their impact on groundwater quality. The method is designed for real catchments where data availability is a major limitation on risk assessment. The model consists of two components: a source model and a large scale transport model. The source model describes the discharge of contaminant from a polluted site where the source of contaminant is located both in the unsaturated zone and in a secondary aquifer. It includes separate phase organics and degradation processes. The transport model applies particle tracking for simulating groundwater flow and residence time in the aquifer. The solute transport description includes sorption effects as well as transformation processes. Degradation is spatially variable and depends on the redox conditions in the aquifer. The risk assessment concept was tested at a contaminated site, Østerparken 5-7, located in Tåstrup, Denmark. The site is heavily contaminated with TCE, where residual phase in a hot spot in the unsaturated zone and the secondary aquifer is present. The simulations performed with the developed models show that the contamination at Østerparken 5-7 poses a large risk for the groundwater resource both locally and at the catchment scale. This risk will be present for an extended period of time. Sensitivity- and scenario analyses were performed to identify the most critical parameters for the risk assessment of Østerparken. Comparisons with existing risk assessment tools were also made.