Evaluating Sampling Techniques

The objective of the part of the research from September 2000 to January 2001 is to determine if more conventional well sampling techniques (no packers, purging, low-flow sampling) yield similar water sample quality as sampling from an isolated zone in a well (packers in place or DMLS in place). This research will be performed in one to three of our preliminary bedrock wells that has exhibited groundwater contamination. The locations of the fractures in the well will be known based on the borehole geophysics. In low-flow sampling of the well, a 5 cm diameter submersible sampling pump will be set at the locations of fractures, and then a series (between four and seven) of sample will be taken at a low flowrate at that location. When sampling is completed at one location, the submersible pump will be removed from the well, decontaminated, and then lowered to the next fracture.

The sampling and decontamination process will continue until all major fractures in a well are sampled. It is expected that this sampling will take at least one day. On the next full day, after the low-flow sampling, packer sampling will commence. The sample pump will be set between two inflatable packers. As with the low-flow sampling, the pump will be lowered to a location of a fracture. At this point, the packers will be inflated to isolate this fracture from the rest of the well. This zone will then be sampled a variety of times as for the low-flow testing. When sampling of this zone is completed, the packers will be deflated and the pump removed and decontaminated and then positioned opposite another fracture in the well. Then a DMLS will be lowered into the well and allowed to equilibrate for at least one week before removal. The samples from all three networks will be analyzed for the full suite of chemical constituents and the resulting data then statistically analyzed to infer differences in the measured water quality of samples result from each sampling method.




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