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' Former Manna Pro Site Page 5 Quarterly Groundwater Monitoring Report Project No 207 2 October 27, 2005 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 direction and gradient of groundwater is consistent with historical measurements The water table has fallen about three feet since the last monitoring event in ' March The mitigation measures employed at the site have substantially reduced the ' concentrations of groundwater contaminants, however the residual concentrations remain significantly above clean-up goals The TPH concentrations in MW-1 and MW-2 were at the lowest levels since monitoring ' began Samples from MW-6 have been yielding TPH concentrations of a few hundred ppb versus several thousand ppb when the remedial system was started and over 100,000 ppb when the well was new The sample from MW-5 ' did not contain detectable contamination for the first time ever Clearly the lateral extent of the contaminant mass is being substantially reduced The VE/AS remedial system had reached the point where the extracted vapor contained very low concentrations of entrained gasoline The system was ' temporarily shut-down during August and September to allow the subsurface equilibrium to restore itself The system was restarted in October and has been performing much better over the past few weeks ' 3.2 Future Work Schedule ' Quarterly groundwater monitoring will continue The vapor extraction / air sparge remedial system will continue in operation, however we anticipate experimenting with periodic system shut-downs to maximize the effectiveness ' of the system 1 • 1 2937 Veneman Ave ,#B240 Geo-Phase Environmental Inc Phone (209) 569-0293 Modesto, CA 95356 Fax (209) 569-0293 I