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Diamond Lumber•Lodi Quarterly Groundwater Moniloring Pae 2 Available information indicates that soil samples were collected from the test hole located in the former UST pit at depths of 17 and 18 feet, and one soil sample was collected at a depth of 17 feet from the test hole adjacent to the former UST location. Soil samples were also collected during the installation of the temporary monitoring well at depths of 17, 25, and 30 feet. Analytical parameters for the soil samples collected during the installation of the temporary monitoring well included benzene, toluene, and xylene (BTX) and total lead, while the soil samples collected from the test holes were analyzed for BTX. One groundwater sample was collected from the temporary monitoring well and also analyzed for BTX. The analytical soil results showed non-detectable Ievels of BTX and lead, however the BTX detection limit was 1 ppm, and the lead detection limit was 10 ppm. Furthermore, the analytical groundwater results did not detect BTX (detection limit of 20 ppb). October 1991 In a correspondence dated October 15, 1991, the San Joaquin County Public Health Services/ Environmental Health Department(PHS/EHD)questioned the validityof the analytical data obtained during the subsurface investigation performed by J.H. Meinfelder & Associates. Specific areas of concern were the high BTX detection limits of the soil and groundwater analyses, the sandy soil conditions observed at the base of the former tank location, and the lack of drilling logs/monitoring well construction data for the temporary monitoring well. Furthermore, the PHS/EHD did not feel that the horizontal and vertical extent of contaminant migration had been adequately addressed. November 1991 SRK was retained by Diamond Lumber to address the potential extent of vertical and lateral contaminant migration from the former USTs. During November 1991,an SRK Field Hydrogeologist supervised the placement of three monitoring wells approximately 10 feet into the groundwater aquifer. These monitoring wells are designated as SRK-MW1 through SRK-MW3. Figure 1 contains the monitoring well locations. During SRK's subsurface soil and groundwater investigation, analytical soil samples were selected during the boring of each monitoring well at depths of 30 feet (seasonal high groundwater level) and 50 feet (capillary fringe) and submitted to a California certified laboratory, The analytical soil parameters included total petroleum hydrocarbons as gasoline (TPH-gas), benzene, toluene, ethylbenzene, and xylene (BTEX), and total lead. The constituents of TPH-gas, BTEX and total lead were not detected in any of the analytical soil samples collected at depths of 30 and 50 feet during the installation of the three monitoring wells. Analytical groundwater parameters also included TPH- gas, BTEX and total lead. TPH-gas was not detected in any of the three monitoring wells. The constituents of BTEX were not detected in monitoring well SRK-MW1, while trace levels of toluene were detected in monitoring well SRK-MW2 at 0.82 ppb, and in monitoring well SRK-MW-3 at 0.63 ppb. Lead was not detected in monitoring wells SRK-MW2 and SRK-MW3, however lead was detected in monitoring well SRK-MW1 at 53 ppb. April 1992 Quarterly groundwater samples were collected from the three monitoring wells installed by SRK. Three additional well casing volumes were purged from monitoring wells SRK-MWl and SRK-MW3 before the analytical samples were collected. Monitoring well SRK-MW2 was bailed dry after one Steffen Robertson and rVISTen