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3.0 INVESTIGATION METHODS USED <br /> This investigation was performed in accordance with practices recommended by the <br /> California State W .ter Resources Control Board (LUFT Field Manu,-l) and the <br /> RWQCB Tri-Regional Recommendations (August 1990) <br /> 3.1 Well/Piezometers Installation <br /> 3.1.1 Locations <br /> 3.1.1.1 Groundwater Monitoring ",Bell Location <br /> In order to evaluate Shallow groundwater quality underlying the former JSTs <br /> excavation in accordance with the RWQCB guidelines, a monitoring well (MW-1) <br /> was constructed within ten feet of the former USTs in the predetermined gradient <br /> direction The groundwater gradient direction was determined from the Mobil Oil <br /> Distribution site as discussed in Section 2 3 The location of the monitoring well <br /> (MW-1) as shown in Figure 3 is down-gradient and within ten feet of both potential <br /> source areas <br /> 3.1.1.2 Piezometer Location <br /> BAI placed two piezoineters (P-1, P-2) as shown on Figure 3, which were used in <br /> • conjunction with the monitoring well (MW-1), to confirm the gradient information <br /> obtained from off-site The piezometers were located to enhance triangulation for <br /> obt inning gradient information and to provide limits on the lateral extent of soil <br /> contamination. <br /> 3.1.2 Well/Piezometers Design and Installation Methods <br /> Both piezometers and monitoring well were placed according to LUFT guidelines <br /> for monitoring wells All installation procedures were consistent w.th applicable <br /> well standards The difference between a piezometer and monitoring well is only <br /> that the piezometers were not developed for use as wells or sampled for the analysis <br /> for the presence of groundwater contamination <br /> The mon,tormg well was completed using ten-inch diameter hollow stem angers to <br /> advance each boring and to allow for the construction of the four-inch morutoruig <br /> well mside the casing with sufficient annular space to place the sand pack The two <br /> inch diameter piezometers were completed using eight-inch diameter hollow stem <br /> auger borings <br /> The augers were steam-cleaned to remove potential contamination before use <br /> During the drilling, augers were not used on more than a single boring prior to <br /> steam cleaning to eliminate the potential for iaoss boring contamination <br /> 4 <br /> BRUNSING ASSOCIATES, INC /���® <br />