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r Date: May 10,2004 Quarter V'Quarter,2004 GRO concentration is based on a single analyte(i e, a non-TPHg analyte or a single TPHg analyte), the analyte will be identified if possible Based on the review of the electronic and hardcopy data (chain-of-custody records, blanks, dilutions, holding times, LCS/LCSD results, MS/MSD results, and surrogate recoveries), the data are acceptable as reported by the Iaboratory DISCUSSION: GRO, benzene, total xylenes, and methyl tert-butyl ether (MtBE) were reported above method detection limits in groundwater samples collected from site wells this quarter MtBE was reported as below method detection limits in ATR-1 this quarter In ATR-2, MtBE concentrations decreased to the lowest level reported above method detection limts GRO was reported as below method detection limits in ATR-3 for the first time since March 2001 In ATR-4, benzene and total xylenes were reported at 14 micrograms per liter (µg/L) and 3 5 ug/L, respectively In ATR-5, GRO was reported as below method detection limits and MtBE concentrations decreased to 16 jig/I- this quarter MtBE concentraitons in ATR-6 decreased relative to the previous sampling event In ATR-8, GRO concentrations increased, a low concentration of total xylenes was reported above method detection limits for the first time since December 2002, and MtBE was reported as below method detection limits this quarter Other analyte concentrations were generally consistent with historic data Groundwater elevation in site wells generally increased relative to the previous monitoring event The inferred direction of groundwater flow across the site ranged from the northeast to east at an average hydraulic gradient of 0 005 to 0 006 feet/foot 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 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 Mpmc ss\b BP ARC01020931Quarter1yN1 QTR 0412093 GWMR 1Q04 du Page 2