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Former Manna Pro Site Page 6 Quarterly Groundwater Monitoring Report Project No. 207.2 April 23, 2002 , 3.0 DISCUSSION I 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 direction of groundwater has returned to a normal bearing and gradient. The water table has risen about 2 feet since the last monitoring event in December. A slight local groundwater high persists in the vicinity of MW-6 as described in prior ' reports. Since February 14 between 4 and S cubic feet per minute cfm has p Y p � ) been injected into the groundwater, but this does not appear to have j L materially affected the groundwater surface and there is no unusual "mounding" of the groundwater. The analytic data suggest that contaminant levels are generally consistent with what has been observed in past monitoring events, although in one well (MW-6), the levels are higher than they have been in several years. We suspect that this may be a result of air sparging mobilizing gasoline hydrocarbons, but it is too soon to have confidence in this speculation. The more distal areas appear to display a gradual degradation of the contaminant plume, but little natural attenuation is occurring in the core area. 3.2 Future Work Schedule f The first phase vapor extraction 1 air sparge remedial system has been ' constructed and was placed in operation on February 14. A report of the construction and first 90 days of operation will be completed within the next 60 days. The results of this initial period will be used to evaluated the ' engineering characteristics of�the system prior to commencing an expansion of the vapor extraction 1 air sparge remedial system. Quarterly monitoring will u continue. l 5 _ 2937 Venexnan Ave.,#B240 Geo Phase Environmental Inc. Phone (209) 569-0293 � Modesto, CA 95356 Fax (209)569-0293 f