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s <br /> 03/10/2005 15:57 53067GE"195 STRATUS NO CALIF PAGE 04/10 <br /> I loo 2-5.2803 <br />� Battetlo 1n Situ and t5n-Si.#c Biorcmedladon Symposium. • <br /> flux equation. These data needs 'ban be broadly categorized into contaminant data and <br /> hydrogeologic data requirements. <br /> Well Placement and Conta�miant Data. <br /> Each transect Of single or multi-level <br /> 7P} well points should extend sufficiently in distance, <br /> monitoring wells or direct-push <br /> both laterally and vertically, in order to define the width and thickness the plume. If <br /> i the plume is not defined on either end with nondetect concentrations, the end points of <br />`> he transect should be at least two orders of magnitude lower than; the plume core <br /> the tr �tratxans. Time series data its u6ed to make estimates for multiple sampling events. <br /> conData, It is � 0rtant that the site hydrogeolog�y is adequately <br /> i chyaractgerized..ogle Detailed cross seetlons, based on borehole logs/COMpletion data for the <br /> transect wells and groundwater elevations, allow for confident estimates of saturated. <br /> thickness. Mass flux estimates are sensitive to,groundwater velocity(specific discharge, <br /> adient measurements. <br /> which is the product of hydraulic conductivity and hydraulic � <br /> I-lydrautic conductivity should beF derived from reliable pumping or slug tests. Hydraulic <br /> gradient estimates are determined from a groundwater elevation contour reap. <br /> APPLICATIONS OF MASS FLUX ESTTES <br /> Several.applications for mass flux estimates are described below and illustrated <br /> with case studies. <br /> Evaluate Potential Impacts ori Receptor's. At a site where there is the potential for <br /> receptor well impacts, mass flux estimates may be used to predict receptor well <br /> concentrations. This is impoiunt because in-situ contaminant concentrations{monitoring <br /> well data) are not necessarily measured at the supply Well, <br /> I <br /> Case Study 1An active service station in Tahoe City,CA is approximately 200 ft (60. <br /> xn)upgradient of a river. The site is characterized by groundwater velocity of 0.2 ft/day <br />'. (0.06 mfday) and a groundwater flow direction to the southeast, toward the river. Five <br /> monitoring wells were used to construct the transect shown in Figure 2a. <br /> r <br /> f <br /> r <br /> k <br /> k <br /> r <br /> I <br /> it <br /> g <br /> I <br /> I <br />