Janniche, Gry Sander1; Christensen, Anders G.6; Grosen, Bernt4; Kerrn-Jespersen, Henriette5; Broholm, Mette Martina1
1 Department of Environmental Engineering, Technical University of Denmark2 Water Resources Engineering, Department of Environmental Engineering, Technical University of Denmark3 NIRAS A/S4 COWI A/S5 Capital Region of Denmark6 NIRAS A/S
Characterization of the contaminant source zone architecture and the hydraulics is essential to develop accurate site specific conceptual models, delineate and quantify contaminant mass, perform risk as-sessment, and select and design remediation alternatives. This characterization is particularly challeng-ing in deposit types as fractured limestone. The activities of a bulk distribution facility for perchloroe-thene (PCE) and trichloroethene (TCE) at the Naverland site near Copenhagen, Denmark, has resulted in PCE and TCE DNAPL impacts to a fractured clay till and an underlying fractured limestone aqui-fer/bedrock. A wide range of innovative and current site investigative tools for direct and indirect docu-mentation and/or evaluation of dense non-aqueous phase liquid (DNAPL) presence were combined in a multiple lines of evidence approach. One scope of the investigations was to evaluate innovative investi-gation methods for characterization of the source zone hydrogeology and contamination, including FLUTe system hydraulic profiling and Water-FLUTe multilevel groundwater sampling, in fractured bryo-zoan limestone bedrock. High resolution hydraulic profiling was conducted in three cored boreholes, placed within a 970 ft2 (~90 m2) area, and Water-FLUTes were installed with 12-13 sampling screens in each borehole. Hydraulic profilling by FLUTe liner system provided information with highere discretization than other traditionel methods, and supported the individual design of Water-FLUTes for multilevel groundwater monitoring, sampling (under two flow conditions) and analysis. Coring for discrete subsampling was a challenge in the limestone, due to core-loss and potential DNAPL loss caused by high drilling water pressure. Hence, the water-FLUTe data proved to be an essential link in the source zone characterization. The results from the high resolution hydraulic profiling and from the Water-FLUTe multilevel sampling will be pre-sented as well as the experiences obtained.
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NGWA Conference on Groundwater in Fractured Rock and Sediments, 2013