ARCHIVED REPORTS XR0010001 - Laserfiche WebLink

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Date, October 27,2004 Quarter 3rd Quarter,2004 • • The elevated reporting limits reported in the EPA Method 8260B analysis of samples MS-3B, MW-2, MW-4,and MW-5 were due to sample foaming • The elevated reporting limits were the result of dilutions performed by the laboratory in order to quantitate a target analyte DISCUSSION: GRO, benzene, toluene, ethylbenzene, total xylenes (BTEX), methyl tert-butyl ether (MtBE), TBA and 1,2-DCA were detected above laboratory reporting limits in groundwater samples collected from site wells this quarter Generally, GRO, benzene and MtBE concentrations remained generally consistent to previous quarters in the monitoring wells (MW), microsparge (MS) wells, and, with few exceptions, in the vapor extraction wells (VW) GRO concentrations increased in VW-1 from I00 micrograms per liter(yg/L)to 12,000,ug/L but remains within the historic high concentration reported during May 1997 In VW-8, GRO concentrations increased from 130 µg/L to 51,000µg/L, a historic high concentration reported in this well These were the only significant increases in GRO concentrations reported across the site however, per the previous section,the concentrations for GRO in VW-1 and VW-8 may be biased high Benzene concentrations increased in VW-8 (from 2 6µg/L to 2,400µg/L),VW-10(from <2 5 pg/L to 84 pg/L), and VW-11 (from <0 5 to 27 ILg/L) MtBE concentrations in VW-1 increased to above the secondary maximum containment level (MCL)of 5 ug/L to 27 yg/L The increase in concentrations this quarter is likely the result of decreased groundwater elevations URS will continue to monitor concentrations to evaluate trends If concentrations do not drop in wells VW-8 and VW-11,URS will evaluate these wells for remediation The plume remains localized and not migrating as observed by downgradient wells VW-7 and MW-3 • Depth to water at the site was approximately 48 feet bgs during this quarter Groundwater elevations decreased approximately four feet relative to the previous sampling event The inferred direction of groundwater flow across the site was toward the northeast with an average hydraulic gradient of 0 002 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 1 Groundwater Monitoring and Analytical Data Table 2 Fuel Oxygenates Analytical Data Table 3 Groundwater Gradient Data FIGURES Figure I Groundwater Elevation Contours Figure 2 Groundwater Analytical Summary APPENDICES Appendix A Field and Laboratory Procedures Appendix B Laboratory Analytical Reports,Chain-of-Custody Documentation,and Field Data Sheets Appendix C GeoTracker Upload Confirmation K%Wp,oc 505 BP ARCM21305Quanuly12004\3 QTR 0452130 GWMR 3Q04 doe Page 2