Groundwater flow delineation study at the Massachusetts Military Reservation using the colloidal borescope.

摘要

Observations of colloidal movement under natural conditions using the colloidal borescope were conducted at several sites in the vicinity of the Massachusetts Military Reservation (MM) located on Cape Cod. The purpose of the study was to assess the reliability of the colloidal borescope and provide additional hydrogeologic data for site-characterization work. Because of the variability observed in groundwater flow at other sites, a well-characterized site was needed to test the borescope. Results of this work indicate that existing hydrologic information specific to the various sites tested at the MM compares favorably with the borehole velocity data collected with the colloidal borescope. Direction measurements at the MM, however, appear to be less reliable than at other sites tested. Most significant among factors potentially affecting direction measurements is the relatively flat hydraulic gradient at the MM, which is an order of magnitude less than at other sites. This is due to the gentle topography and the relatively high permeability of the aquifer. Under these conditions, the geometric alignment of preferential flow paths could dominate flow direction. If the gradient is increased, flow will tend to parallel the hydraulic gradient. This report describes the field site and the colloidal borescope and discusses the results and conclusions of the field investigations.