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time, the laboratory detected benzene, toluene, and ethylbenzene in VM-3 (Table 2) Total petroleum hydrocarbons in the gasoline range were also detected in the sample from this well, but the concentration was below the reporting limt of 50 µg/l (parts per billion) and is therefore shown as ND in Table 2 and Appendix B Both the TPH-g and benzene concentrations also increased in VM-2, whereas the concentrations of these analytes decreased in VM-I Other compounds decreased or were essentially unchanged Chlorinated solvents were again detected in VM-1 and VM-2, and six compounds were detected for the first time (Table 3) These include dichlorodiflouromethane, vinyl chloride, 1,1- dichloroethene, 1,1-dichloroethane, 1,1,2-trichloroethane, and 1,4-dichlorobenzene 5.4 CONCLUSIONS Groundwater depth measurements indicate that there has been little change in depth or direction of flow since the wells were monitored in July Laboratory data, however, indicate_potentially significant changes in contaminant concentrations during the same period TPH-g and BTEX data suggest that the plume of gasoline-contaminated groundwater has migrated southeastward from its position in July, and has now reached VM-3 As a result, groundwater in the vicinity of VM-1 is slightly less contaminated with gasoline than it was in July During this same period, the variety of chlorinated compounds has increased in both VM-1 and VM-2, suggesting that the plume of solvent-contarninated groundwater has also migrated eastward and further contamined the groundwater beneath the site The chlorinated hydrocarbons provide additional evidence of a solvent leak west of the site Based on the data collected in 1996, Upgradient recommends that groundwater monitoring be / increased to quarterly in 1997 to provide more precise information on the rate of contaminant migration We also recommend that the area of investigation be extended to the east to identify the present downgradient extent of gasoline contamination We strongly recommend that the investigation be extended to the west to determine the upgradient extent of solvent contamination and to identify its source, which we believe is the responsibility of one or more businesses located west of Valley Motors We recommend that Valley Motors and its attorney request San Joaquin County PHS/E14D to identify other Responsible Parties upgradient of Valley Motors and request these parties to perform investigation of the solvent plume 4 4