ARCHIVED REPORTS XR0001266 - Laserfiche WebLink

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Date April 26,2004 Quarter 1s1 Quarter,2004 DISCUSSION: Gasoline range organics (GRO), benzene, toluene, ethylbenzene, total xylenes (BTEX), methyl tert-butyl ether (MtBE),tert-butyl alcohol(TBA),and 1,2-dichloroethane(1,2-DCA)were reported above method detection limits in groundwater samples collected from site wells this quarter Analyte concentrations were generally consistent with historical data with the following exceptions in MW-1, total xylenes concentrations continue to decrease and GRO concentrations increased relative to the previous monitoring event but remain significantly below historic high ranges 1,2-DCA concentrations increased in wells MWAB and MW-1C relative to the previous quarter GRO and BTEX concentrations in MW-2 and GRO,ethylbenzene, and total xylenes concentrations in MW-5 were reported as below method detection limits this quarter Also in MW-5, benzene concentrations decreased to the lowest levels reported historically TBA concentrations in MW-3 were reported at the highest level above method detection limits relative to historic data During the fourth quarter 2003 sampling event,the reported concentrations of GRO,BTEX, and MtBE in samples MW-4 and MW-6 decreased to levels that were inconsistent with historical concentrations During this sampling event, the reported concentrations of GRO,BTEX,and MtBE in wells MW-4 and MW-6 were reported at Ievels more consistent with historical data Consequently,the data from the fourth quarter 2003 sampling event for monitoring wells MW-4 and MW-6 were rejected Benzene and total xylenes concentrations increased in MW-7 relative to previous sampling events A low level concentration of MtBE was reported above method detection limits in MW-8B for the first time since February of 2002 Groundwater elevations across the site increased relative to the previous quarter The inferred direction of groundwater flow across the site was toward the southeast at an average hydraulic gradient of 0 004 ft/ft This report is based on data, site conditions, and other information that are generally applicable as of the date of the report,and the conclusions and recommendations herein are therefore applicable only to that time frame TABLES Table i Groundwater Elevation and Analytical Data Table 2 Fuel Oxygenates Analytical Data Table 3 Groundwater Gradient Data i FIGURES Figure 1 Groundwater Elevation Contours Figure 2 Groundwater Analytical Summary APPENDICES Appendix A Field and Laboratory Procedures Appendix B Laboratory Analytical Reports,Cham-of-Custody Documentation,and Field Data Sheets Appendix C GeoTracker Upload Confirmation K 1WPmcess\15 BP ARCO\02168NQuanerlyll QTR 04\2168 GWMR 1Q04 do Page 2