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' Geologrcaf?echnus inc Page 3 Groundwater Monitoring Report Project No 507 2 November G,2000 ' Sherwood analyzed the eight-groundwater samples 0 Benzene, Toluene, Ethyl Benzene, and Xylene (BTEX) by EPA method 602 ' • Total Petroleum Hydrocarbons as Gasoline (TPH-G) by EPA method 5030/8015(M) Additional samples were sent to Entech Analytical from Sherwood Labs for the analysis of • MTBE, DIPE, ETBE, TAME and TBA by EPA method 8260 The results and 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 analyses show the following • There continues to be no evidence of any contamination in MW-1, MW-2 and MW-3 • MW-4, MW-5 and MW-9 have significant BTEX and TPH-G contamination ' • MW-6 and MW-8 have slight BTEX and moderate TPH-G contamination • MW-6 has 10 ug/l MTBE MW-5 and MW-9 did not contain MTBE above the laboratory detection limits, however it is noted that the limits are elevated due to the high levels of TPH-G contamination Gasoline oxygenates DIPE, ETBE, TAME and TBA are not present in any of the groundwater samples o The groundwater gradient is relatively flat and the direction of groundwater has varied during the course of the investigation The site is quite close to the San Joaquin River and tidal fluctuations might be responsible for the observed changes in groundwater direction i The later _ al extent of the contamination plume is defined to the east, north-east and south-east ' by MW-3, MW-2 and MW-1 The plume has not been defined laterally to the west nor has it been defined vertically ' GTI makes the following recommendations • Continue quarterly groundwater monitoring • Further define the lateral vertical extent of the plume - T iGTI will submit a workplan to address the definition of the lateral vertical al extent of the plume in November 2000 1 i 1 1