INTEGRATED BOREHOLE LOGGING METHODS FOR WELLHEAD PROTECTION APPLICATIONS

Modeling of ground water infiltration and movement in the wellhead are a is a critical part of an effective wellhead protection program. Such models depend on an accurate description of the aquifer in the wellhe ad area so that reliable estimates of contaminant travel times can be used in defining a protection area. Geophysical and hydraulic measurem ents in boreholes provide one of the most important methods for obtain ing the data needed to specify wellhead protection measures. Most effe ctive characterization of aquifers in the wellhead vicinity results wh en a variety of geophysical and hydraulic measurements are made where geophysical measurements can be calibrated in terms of hydraulic varia bles, and where measurements are made at somewhat different scales of investigation. The application of multiple geophysical measurements to ground water flow in the wellhead area is illustrated by examples in alluvial, fractured sedimentary, and fractured crystalline rock aquife rs. Data obtained from a single test well are useful, but cannot indic ate how conductive elements in the aquifer are connected to form large -scale flow paths. Geophysical and hydraulic measurements made in arra ys of observation boreholes can provide information about such large-s cale flow paths, and are especially useful in specifying aquifer prope rties in wellhead protection studies.