SELECTION AND APPLICATION OF INVESTIGATIVE METHODS FOR A CHLORINATED SOLVENT IMPACTED KARST AQUIFER
Eight bedrock core holes, up to 176 feet deep, were advanced by wire line coring. Rock cores provided a direct assessment of lithology and integrity. Transmissive intervals, inferred by drilling water loss, were isolated by packers or low-flow sampling techniques through the core barrel to obtain vertically discrete groundwater samples. The ColorTec Ground-Water Tester provided semi-quantitative, dissolved cVOC concentrations in real-time to assess the presence of DNAPL, the potential for vertical contaminant transport from continued coring, and the need for a temporary vertical seal upon completion. Confirmation samples, analyzed at a fixed-base laboratory, were evaluated in conjunction with passive groundwater samples obtained from the open core holes using polyethylene diffusion bag (PDB) samplers, resulting in separate vertical cVOC profiles for each core hole. A borehole geophysical tool suite (mechanical caliper, acoustic and optical televiewer, and natural gamma) was deployed at four core holes to evaluate bedrock structure and lithology. Heat pulse flowmeter testing indicated the presence of vertical groundwater flow zones in the core holes, and fluid temperature and resistivity data addressed overall groundwater character.
Collectively, the investigative tools maximized core hole information, minimized vertical cross contamination, and provided vertically discrete data for the design and installation of multi-level Water FLUTe monitoring wells in seven core holes.