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i <br /> GEOMATRIX <br /> GROUNDWATER MONITORING RESULTS <br /> ' 540 North Aurora Street <br /> i <br /> Stockton, California <br /> ' 1.0 INTRODUCTION <br /> This report describes the results of groundwater monitoring performed by Geomatnx Consultants, Inc <br /> ' (Geomatnx) on behalf of Chevron Real Estate Management Company at 540 North Aurara Street in <br /> Stockton, California (the site) (Figure 1) <br /> 2.0 BACKGROUND <br /> ' Three underground fuel storage tanks formerly existed at this site, all three tanks have been removed <br /> (Figure 2) Two of the tanks were used to store leaded gasoline, and the third tank was'used to store <br /> ' diesel fuel Soil samples collected from beneath the tanks following their removal reportedly contained <br /> petroleum hydrocarbons at low concentrations <br /> ' Analytical results for groundwater samples collected from three groundwater monitoring wells at the site <br /> (Figure 2) are summarized in Table 1 Total petroleum hydrocarbons as gasoline(TPH-G), total petro- <br /> leum hydrocarbons as diesel (TPH-D), and benzene, toluene, ethylbenzene, and xylenes (BTEX) have <br /> been reported sporadically in groundwater samples collected from some of the wells at concentrations <br /> ' very near the detection limit during previous monitoring rounds Results of groundwater monitoring <br /> performed in August 1994 indicated that TPH-G, TPH-D, and BTEX were not detected mi groundwater <br /> samples collected from the three groundwater monitoring wells Results of groundwater monitoring <br /> ' performed in February 1995 indicated that TPH-G and BTEX were not detected in groundwater samples <br /> collected from the three wells TPH-D was reported at a concentration of 51 micrograms per liter in <br /> the February 1995 groundwater sample collected from well MW-1, however, the laboratory that per- <br /> formed <br /> erformed the analysis indicated that the material in the sample did not match the diesel standard (Canonie, <br /> ' 1995) <br /> i <br /> As requested by Jim Waldron of Chevron Production Company, a subsequent review of the chromato- <br /> ' gram for the February 1995 sample from MW-1 by Dr James E Bruya of Friedman & Bruya, Inc <br /> indicated there was no material in this sample that boiled in the diesel range Mr Waldron then asked <br /> Geomatnx to resample the wells using other sampling and analytical methods to evaluate if the concen- <br /> tration of diesel reported was an accurate representation of the amount of diesel dissolved in <br /> groundwater <br /> I <br /> 1 <br /> j i <br />