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• Discussion Groundwater flow direction appears consistent with historically observed trends Neither fuel nor MTBE contaminants were observed in any well, including MW-4 Fluctuations i n contaminants are attributed to residual contaminants desorbing into the groundwater from the soil strata in the immediate vicinity of the former tank pit Aquifer discharge has probably contributed to desorbtion, and volatile components continue an overall declining trend Well MW-1 was destroyed during the soil excavation to remove residual contaminants which had historically been observed at MW-1 Once the excavation work has been completed, the monitoring well be replaced Very low concentrations of Tetrachloroethene (PCE), Trichloroethene (TCE) and c i s-1 ,2- Dichloroethene were observed in upgradient well MW-2 These compounds were observed at concentrations dust above the detection limit, and could be laboratory error, or hint at the leading edge of another contaminant plume This contaminant group is strongly suggestive of a dry cleaner source, and do not arise from M and M Conclusions and Recommendations Wright has completed the excavation of contaminated soil in the vicinity of the former • underground tank pit source and well MW-1 It is assumed that the removal of this contaminated soil will remove the low concentration contaminants observed at MW-1 Very low concentrations of V+OC were observed at MW-2 These contaminants are typical of a dry cleaner source and occur in upgradient well MW-2, showing that they did not arise from M and M An upgradient source for these contaminants is assumed Wright recommends that the quarterly monitoring for this site continue at quarterly intervals pending PHS EHD review Limitations This report has been prepared specifically for the M & M site at 60 E 10th Street, Tracy, CA, and was done according to the State and local agency suggested guidance documents for these investigations The interpretations, conclusions and recommendations made herein are based on the data and analysis for the water samples collected on-site and should be reviewed in the context of the whole report Please note that reports of contamination must be submitted to the agencies in a timely manner Wright Environmental Services, Inc is not responsible f o r errors in laboratory analysis and reporting, or for information withheld during the course of the study, and no warranty or guarantee is expressed or implied therein 0 Page 4