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Mr Terry Tarditi <br /> February 3, 2005 <br /> Page 3 <br />' Analytical laboratory Kiff Analyttcal, Inc, <br /> Davis,Cahfomta <br />' (California Department of <br /> Toxic Substances Control <br /> Certification No 2336) <br />' Sample exceptions None <br /> Shallow groundwater gradient (3rd qtr) 0 002 <br /> Shallow groundwater flow direction (311d qtr/4d'qtr) Northeast <br />' Average depth-to-water (2nd qtr) 72 43 feet <br /> Average change in shallow groundwater <br /> elevation from 3�d qtr to 4d' qtr 3 27 feet <br />' DISCUSSION <br />' Based on the fourth quarter's data, the groundwater hydraulic gradient remains <br /> relatively flat,with a hydraulic gradient of 0 002 feet per foot,as shown in <br /> Figure 2 This flat hydraulic gradient is helping retard further lateral migration of <br /> constituents of concern of which has been documented by the field investigation <br /> results summarized in Brown and Caldwell's Subsurface Investigation Results and <br /> Site Conceptual Model,June 28, 2004 Also documented in the June, 2004 Report <br /> was a detection of low MtBE concentrations in a deeper zone indicating a <br /> potential vertical migration pathway <br /> Historical water level elevations are shown on Figure 5 and shows an overall <br /> decline of approximately one foot per year from when measurements were first <br /> collected in 1998 There is a seasonal trend to the water levels with seasonal lows <br /> ' during the fall and highs during the spring <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, samples from this well are not included in the discussions <br />' below <br /> BTEX The reporting limits for all constituent concentrations in MW-1 were <br />' increased to 25 micrograms per liter (µg/L) from 15 µg/L due to known high <br /> concentrations of MtBE The 15 µg/L was a decrease from the 25 µg/L reporting <br /> for the second quarter The dilutions were necessary because the MtBE <br />' concentrations were out of the calibration range for the target analyte Samples <br /> . from MW-1 are analyzed multiple tunes by the analytical laboratory to bring the <br /> correct dilution into the calibration range The reporting hmits remained the same <br /> ' Thu report=s pnpand m aavrdancr Hath the standwdf f tlx enwroxmenta!tonsxlhng tn&s1g at the lime it aws proand 11 sbomld not be <br /> rehed xpon by parties other than those for whom it nw,r pnpand,and then only to the extent of the stupe f nrork which aws axthmVd. This <br /> upon does not powke that no additional enwranmental contamination beyond that desenbed in fibs report exrsts at the site <br /> ' P\21000\21417-T&T\Rcports\4th-04gtr doc <br />