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' GeofogicaTedi ntcs Inc Page 3 Groundwater Monitornig Report Project No 724 2 August 8, 2000 ' A chain of custody document, listing all samples collected and their intended analyses, accompanied the samples from field to the laboratory, thereby providing a means to track their movement and ensure their integrity 1.3 Laboratory Analyses rThe groundwater samples collected on June 28, 2000, were delivered to Sherwood Labs of Hilmar, California (certification 91400) for analysis of ' 0 Benzene, Toluene, Ethyl Benzene, and Xylene (BTEX) by method EPA method 602 • Total Petroleum Hydrocarbons as Gasoline (TPH-G) by EPA method 5030/8015(M) Samples from each well were also sent to Entech Analytical (certification #2346) from Sherwood Labs for the analysis of • MTBE, DIPE, ETBE, TAME, TBA, methanol, ethanol, 1,2-DCA, and EDB by EPA method 8260B The detection limits for the above analyses are listed in Table 2 of Appendix A, while the lab analytical results are presented in Appendix B 2.0 FINDINGS AND DISCUSSION ' The results of the groundwater sample analysis show the following • MW-1 and MW-3 have slight BTEX contamination • NIW-2 and MW-4 have moderate to high benzene contamination and slight to low concentrations of the other BTEX analytes • MW-2, MW-3 and MWA have moderate to low TPH-G contamination • Gasoline oxygenate TBA was detected in wells MW-2 and MW-4, 5 7 and 18 ug/l, respectively Well MW-4 contained 1 7 ug/1 1,2-DCA • Contaminant concentrations are similar to those observed in the last monitoring event in wells MW-l through MW-4 Down gradient well MW-5 was non-detect for all analytes ' for the first time since installation ' The contamination plume is defined laterally to the east by MW-5 It is not defined laterally in any other direction, nor is it defined vertically 'r �I • r r