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• Mr Terry Tarditi <br /> July 25, 2006 <br /> Page 3 <br /> Analytical laboratory Kiff Analytical,Inc, <br /> Davis,California <br /> (California Department of <br /> Toxic Substances Control <br /> Certification No 2336) <br /> Shallow groundwater gradient Northeast <br /> Shallow groundwater flow direction 0 004 feet/foot <br /> Average depth-to-water 68 2 feet <br /> Average change in shallow groundwater <br /> elevation from 1st qtr 2006 to 2nd qtr 2006 5 99 feet <br /> DISCUSSION <br /> Based on the second quarter's data,groundwater flow direction changed from a <br /> relatively flat gradient to one flowing to the northeast under a hydraulic gradient of <br /> 0 004,as shown in Figure 2 The northeast gradient is consistent with histoncal <br /> gradients for the site as shown in Table 2,however, the recent air sparge pilot test <br /> has most likely influenced water levels in MW-1 and, therefore, doesn't represent <br /> static conditions Table 2 summarizes quarterly measurements of the hydraulic <br /> gradient <br /> The on-site supply well has been sampled on a quarterly basis since November <br /> 2002 and has never contained any detectable concentrations of any constituents of <br /> concern Therefore, sample results from this well are not included in the <br /> discussions below In addiuon,concentrations of 1,2-DCA and EDB have not <br /> been detected and are not included in the discussion below <br /> BTEX The reporting limits for all constituent concentrations in MW-1 were <br /> diluted due to known high concentrations of MtBE The dilutions were necessary <br /> because the MtBE concentrations were out of the calibration range for the target <br /> constituent The reporting limits remained the same for remaining wells at <br /> 0 5 micrograms per hter (µg/L) BTEX concentrations were below their <br /> respective reporting limas in all of the wells consistent with previous quarters Per <br /> PHS/EHD's request, Brown and Caldwell worked with the analytical laboratory to <br /> determine when it is feasible to quantify the BTEX constituents without damaging <br /> the equipment, especially in samples from MW-1 <br /> P\30000\130625 1&F 1ruckingGW Monitonng2006\Reports\2nd-06gtrdix <br />