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IFormer Manna Pro Site Page 6 Quarterly Groundwater Monitoring Report Project No 207 2 . March 2, 2000 I 3.0 DISCUSSION 3.1 Discussion of Data Field and analytical data results are summarized in Summary Table 1 and illustrated in Figures 3 through 5 The map of groundwater gradient (Figure 3) suggests that the flow of groundwater is to the northeast The water table has risen about V2 foot since the last monitoring event in October The area of ground water depression observed in the last monitoring event has largely disappeared, although a depressed "trough" is still evident ' The analytic data suggest that contaminant levels are generally consistent with what has been observed in past monitoring events Two anomalies of note concern the analytical results of samples from MW-8 in which an anomalous "spike" results 1n a high reading of TPH-G The reported TPH-G concentration of 4480 ppm from that sample does not appear to represent actual aquifer conditions The other anomaly previously discussed is the presence of traces of xylene in blank samples It was concluded that this is due to the presence of xylene in the make-up water used to prepare the blank samples, and that the ' xylene was introduced into the water during the distilling, or packaging process at the manufacturers facility ' One sample from the previous monitoring event (MW-1) contained 670 ppb of 1,2 DCA To further explore the distribution of this chlorinated hydrocarbon, three samples were tested for the presence of 1,2 DCA in this round of sampling The three samples were from wells, MW-1, MW-2, and MW-6 None of these samples contained detectable levels of 1,2 DCA In general, the presence of gasoline in the groundwater remains at fairly high levels and is distributed over a rather large area The core of the contaminant I mass is, however, confined to a relatively small area in the vicinity of the original release site 3.2 Future Work Schedule The San Joaquin County PHS/EHD has approved a Work Plan to conduct additional site characterization of the deeper groundwater and to complete pilot level testing of several remedial technologies The California UST Fund (USTCFP) recently issued a letter of "pre-approval" for reimbursement of the 2937 Veneman Ave,#B240 Geo-Phase Environmental Inc Phone (209) 569-0293 Modesto, CA 95356 Fax (209) 569-0293