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File No 2070 2 30 November 1993 Page 3 ' 5 0 Groundwater Sample Results Groundwater samples from monitoring wells MW-1, MW-6 and MW-8 were submitted to Western ' Environmental Science & Technology for analysis for constituents noted in Section 3 0 The laboratory data indicates that petroleum hydrocarbons as gasoline were detected in the groundwater sample collected from monitoring well MW-1 No petroleum hydrocarbons were detected in the ' groundwater samples collected from monitoring wells MW-6 and MW-8 Lead was detected in all three groundwater samples collected from monitoring wells MW-1, MW-6 and MW-8 Lead has been detected Imi ly consistently in monitoring well MW-1 due to the presence ' of dissolved petroleum hydrocarbon` in this well However, lead has never been detected in monitoring wells MW-6 and MW-8 prior to this current sampling ACG believes the detection of lead in these two wells is a likely a result of the low water levels in the wells The low water levels ' resulted in the introduction of silt in the water samples The detection of lead in the groundwater samples is likely attributable to the pre%L.ncc of silt in the samples ' Table 11: summarizes the results of the loboratoiy analyses Figure 2 illustrates the locations of the monitoring wells A copy of the laboratory data is include-d in Appendix 1 ' 6 0 Disposition of Purged Well W,itL r Groundwater purged from the monitor Ing wells was containci ized in a 55-gallon drum and stored on the site Following receipt of the. analytical data Ramos Environmental Services of West Sacramento collected and disposed of the drummed water on 5 Novembei 1993 The water was disposed under Uniform Hazardous Waste Manifest number 92508114 as a RCRA hazardous waste liquid The ' water was classified as a RCRA hazardous waste since the concentration of benzene exceeded 500 parts per billion per California Code of Regulations, Title 26, Section 6626124 A copy of the Uniform Hazardous Waste MaMIL't Is included as Appendix Il ' 7 0 Conclusions The following conclusions are baud on data obtained during the third quarter 1993 sampling as well ' as prior samplings 1) The local flow direction of th(, groundwater was determined to be toward the east/northeast with a gradient of 0 0016 it/it This is consistent with the east/northeast flow directions calculated for prior samplings ' 2) The groundwater sample collected from monitoring well MW-1, located in the center of the prior tank cluster, had 41,000 parts per billion petroleum hydrocarbons as gasoline No diesel fuel or motor oil .sas detected Gasoline has been detected in this well during prior ' samplings at similar concentrations ANDERSON U CONSULTING ' GRDUP