APPLICATION OF THE IN-WELL POINT VELOCITY PROBE (IWPVP) IN FRACTURED MEDIA

Point Velocity Probes (PVPs) have been recognized as a relatively low-cost tool for in-situ, direct measurement of groundwater velocity at the centimeter-scale. The In-Well Point Velocity Probe (IWPVP) is a recent modification of the PVP design allowing for use in existing monitoring wells. Utilizing a miniature tracer test within the body of the probe, IWPVPs can accurately determine the magnitude and direction of groundwater flow within an observation well. Various tests have supported the tool’s capabilities when deployed in porous media wells. The often-complex subsurface conditions of porous media that call for the use of the IWPVP may resemble those in aquifers with fractured media. Therefore, we hypothesize that the ability of the IWPVP to produce accurate and precise results will remain consistent when deployed in fractured media. Validation of this hypothesis would allow for the appropriate use of the IWPVP in fractured rock aquifers.

Both laboratory and field work has been carried out to examine the capabilities of the IWPVP in fractured media. A bench-scale laboratory model of a single, horizontal fracture was designed and utilized to determine if there were any immediate shortcomings of the current IWPVP design and to develop a calibration curve, or correction factor, vital to work in the field. Preliminary calibration curve determinations support the hypothesis and suggest that the IWPVP in a single fracture performs comparably to an IWPVP in porous media. Additionally, field work carried out in conjunction with GSI Environmental Inc. in fractured media wells on Edwards Air Force Base supported the IWPVP’s ability to perform in these new fractured settings, producing results qualitatively similar to other methods used at the same site.