Laserfiche WebLink
and laboratory results of vapor samples are graphed in Figure 5 to illustrate the effect of the system on <br /> soil vapor concentrations _ <br /> ' Flow rates for the quarter ranged from a low of 28 cfm to a high of 45 cfm For most of the quarter, <br /> the unit operated efficiently only below 40 cfin The reason for poor operation at higher rates was <br /> uncertain, but the manufacturer of the extraction'unit had suggested that the CO2 concentration in the <br /> ' vapor stream may have increased due to natural biodegradation of the hydrocarbons Therefore, with <br /> the Iapproval of San.Joaquin County EHD, the December vapor sample was analyzed for inert gases to <br /> test this possibility <br /> In contrast to the first two quarters of 1995, when field monitoring indicated significant decreases in <br /> ' hydrocarbon concentrations, concentrations showed no obvious trends during the third quarter (Figure <br /> 5) During the fourth quarter, concentrations fluctuated somewhat, but Figure 5 illustrates an overall <br /> decrease in the combined stream and in the deep well Comparison of Figures 4 and 5 shows that, nn' <br /> ' contrast to previous quarters, vapor concentration was independent of air flow rate <br /> Comparison of the laboratory result (Appendix B) of the sample collected on December 14 with the <br /> PID reading on that date yields satisfactory correspondence When converted from parts per million by <br /> volume (ppmv) to parts per million by weight, the laboratory result of 555 ppm is within 12% of the <br /> value of the PID reading of 625 ppm <br /> ' 4.2 Weight of VOC's Destroyed <br /> The weight of VOC's extracted during the quarter can be computed by using the average PID <br /> concentration from Figure 5 and the cumulative volume of extracted vapors from Figure 4 <br /> ' WEIGHT OF VOU S=' <br /> CF x I VAPOR x 10-6 x 100 mol/wt <br /> 379 cf/mole <br /> ' r <br /> =4243 x 106 W 740 x 10-6x 100 moi/wt <br /> 379 cf/mole <br /> ' =3 13982 x 105 lbs <br /> 3 79x 102 <br /> ' - = 828 lbs <br /> 5.0 GROUNDWATER MONITORING <br /> t5.1 Monitoring Procedures <br /> Groundwater momtonng took place on December 14, 1995 All six monitoring wells and the deep <br /> vapor extraction well were opened and the depth'to groundwater was measured <br /> 4 <br /> 1 ' <br />