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BC&D Properties <br /> Report, MW Installation and Monitoring <br /> Project No. 8.1.2 <br /> December 17, 1992 <br /> Lae Page 5 <br /> Before each sample was collected the well was purged of stagnant water while <br /> `r monitoring temperature, conductivity and pH. The groundwater samples were <br /> submitted to GeoAnalytical Laboratories of Modesto (to be analyzed for benzene, <br /> toluene, total xylenes and ethylbenzene (BTEX) by EPA method 602, and total <br /> petroleum hydrocarbons (TPH-Gasoline) by 5030/LUFT and Total Lead by EPA <br /> method 7421. <br /> The detection limit for benzene, toluene and ethylbenzene is 0.3 µg/l (ppb), and <br /> 0.6 gg/l for total xylenes. The detection limit for TPH-Gasoline is 5.0 mg/l (ppm) <br /> and the detection limit for total lead analyses is 0.01 mg/l. <br /> Groundwater quality parameters including temperature, conductivity (EC), and <br /> pH were field measured and recorded while purging the wells. The information <br /> is as follows. <br /> Weil Gattorm Purged Temp. cnnauctiviry p11 <br /> C µmhoalcm <br /> MW-1 OS 213' 1691 7.20 <br /> 1D 21.2' 1566 721 <br /> 15 21.2° 1561 723 <br /> MW-2 OS 125° 1582 7.05 <br /> 1.0 20.9° 1573 6.90 <br /> 15 204, 1580 7.14 <br /> MW-3 05 21.9' 1906 6.98 <br /> 1D 21.9° 1887 7.03 <br /> 15 21.9• 1897 7,00 <br /> i" <br /> MW-4 05 15.7• 2570 7.11 <br /> 1.0 IBIS* 2240 736 <br /> 15 172• 1 2310 1 737 <br /> ie <br /> 4.0 DISCUSSION AND RECOMMENDATIONS <br /> 41 Discussion <br /> The sampling of both the soil and groundwater environments from MW-4 <br /> indicate that petroleum hydrocarbons have not impacted the soil or groundwater <br /> at this monitoring well location. Combining these data with previously <br /> generated soil and groundwater testing data, indicate that the horizontal extent <br /> of hydrocarbon contamination is confined to the immediate excavation area. <br /> The down gradient well, MW-4 shows that the hydrocarbon contamination has <br /> not migrated into the groundwater at this location at this time. <br /> The steady decrease in petroleum hydrocarbon content in the detected <br /> monitoring wells have reduced by an order of magnitude from the initial testing <br /> event (benzene from 24.6 gg/l down to 2.1 gg/l; Table 3, Appendix A). This <br /> L <br />