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1 <br /> TABLE 4 <br /> Groundwater Analytical Results Summary <br /> San Joaquin County Mosquito and Vector Control District Facility <br /> 7759 S. Airport Way, Stockton, California <br />' Location ID Benzene Toluene Ethylbenzene Xylene TPH-D TPH-G <br /> Mcg/L ILg/L µg/L µg/L mg/L mg/L <br />' HPl-GW ND ND ND ND 088 ND <br /> HP2-GW ND 5 0 ND 26 1 3 ND <br />' MW-1 ND ND ND ND ND = <br /> MW-2 ND ND ND ND ND <br />' MW-3 ND ND ND ND ND = <br /> MW-5 (rinse ND ND ND ND <br /> blank) <br />' ND = Not detected <br /> - — Sample not analyzed for this parameter <br />' 4.0 CONCLUSIONS AND RECOMMENDATI NS <br /> As shown in Table 3, low concentrations of TPH-D, ranging between 2 1 and 11.0 mg/Kg, were <br /> found In all soil samples taken from soil borings SB-1 and SB-2 which bracket the area of the <br /> former spray o11 tanks and the subsequent 1987 remedial excavation As noted in Section 1 1 <br /> of this report, concentrations of up to 5,500 mg/Kg were found 1n this area prior to completion <br />' of the remedial excavation No BTEX compounds were quantified in soil samples taken dunng <br /> the remedial work nor were they found by this investigation While the low TPH-D <br /> concentrations found in the soil boring samples extend to,lust above the current water table, no <br />' TPH-D concentrations (as summarized 1n Table 4) were found in groundwater samples collected <br /> from the three monitor wells located to surround this area. <br /> Due to the total lack of BTEX concentrations in soil and groundwater within this area and the <br /> demonstrated success of the 1987 remedial excavation in removing the vast majority of the <br />' extractable hydrocarbons (TPH-D) from the former tank area, WESTON recommends no further <br /> action be pursued for this area of the site. Furthermore, given the high cost that would be <br /> involved In pursuing the minimal TPH-D concentrations remaining in the soil at the fringe of <br />' the previously excavated area and the demonstrated lack of groundwater impacts, WESTON <br /> recommends that the site proceed into formal closure. <br />' For the former gasoline tank site (Tank 3) explored by soil boring HP-1, no further work is also <br /> recommended. Soil samples, collected from the boring at 8 and 12 feet below grade, did not <br /> show the presence of either TPH-D or TPH-G The groundwater sample collected from the <br /> boring via the Hydropunch tool also did not show any quantifiable concentrations of BTEX or <br /> TPH-G compounds Although TPH-D was found at a very low concentration of 0 88 mg/L in <br /> the groundwater sample, this finding does not appear to be related to the historical use of <br /> Tank 3 <br /> l SCKIRP't'SWCMVCDI STK <br /> 7 1 MAI% <br />