A TEST OF THE IN-SITU PERMEABLE FLOW SENSOR AT SAVANNA RIVER, SC

A test of the In Situ Permeable Flow Sensor was conducted in which gro und-water flow velocity measurements made by the flow sensors were dir ectly compared to velocity estimates obtained using standard hydrologi c techniques, Two flow sensors were deployed in a confined aquifer in close proximity to a well which was screened over the entire vertical extent of the aquifer, When the well was pumped at four different pump ing rates, the horizontal component of the flow velocity measured by t he flow sensors was directed toward the pumping well, within the uncer tainty in the measurements, and the magnitude of the horizontal compon ent of the velocity increased linearly with pumping rate, as predicted by theoretical considerations. The measured magnitudes differed from predicted values, calculated with the assumption that the hydraulic pr operties of the aquifer were homogeneous and isotropic, by less than a factor of two, Vertical components of ground-water flow observed with . the flow sensors are qualitatively consistent with the vertical dist ribution of hydraulic conductivity estimated from grain-size analysis but are significantly larger in magnitude than predicted, This is like ly due to the creation of a vertical conduit of increased hydraulic co nductivity during emplacement of the probes, The results suggest that while the flow sensors measured the local ground-water flow velocity v ector during the test quite accurately, care must be exercised to dist urb the formation as little as possible during emplacement. The techno logy has many potential uses, particularly in the area of environmenta l site characterization and remediation process monitoring.