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air sparging at the SP-1 location was not resulting in an adequate decrease of <br /> petroleum impact in groundwater Therefore, new sparging well SP-A was <br /> drilled and completed on March 14, 2002 New sparging well SP-A was <br /> placed within the area of highest groundwater impact, about 10 feet southwest <br /> of well MW-1 (see Figure 2) Air sparging into SP-A is performed by <br /> supplying an approximate volume of 5 standard cubic feet per minute (scfm) <br /> PSC installed a new air sparging compressor on September 5, 2002 <br /> Venting is performed by withdrawing an approximate volume of 25 to 35 <br /> scfm of soil gas from well VW-1 Soil gas is treated initially through a <br /> primary 1,000 pound granular activated carbon (GAC) adsorber and then <br /> through a secondary 160 pound GAC adsorber <br /> Permits to operate the remediation system and emit treated air have been <br /> obtained from the San Joaquin Air Pollution Control District (SJAPCD) <br /> Emission reports are routinely submitted to the SJAPCD The system is <br /> generally monitored weekly to ensure efficient operation and permit <br /> compliance <br /> A summary of system operation, vapor concentrations and total pounds of <br /> removed contaminant is included in Table b of this report Vapor <br /> concentrations of influent and effluent streams, observed from weekly <br /> laboratory analysis of samples, are reported in Table 6 columns labeled C(int) <br /> and C(eff), respectively Vapor extraction flow rates are labeled Q(inf) and <br /> Q(eff) Total pounds of contaminant removed by the soil vapor extraction <br /> system are tabulated under the PE columns <br /> As shown to Table 6 and the associated graph of influent air sample results, <br /> recovered vapors are reaching lower asymptotic levels When first initiated, <br /> influent gas was recovered at a typical rate of 20 to 40 pounds per week <br /> Currently, influent gas is recovered at a typical rate of less than 2 pounds per <br /> week PSC considers that the remedial system's effectiveness to treat <br /> subsurface impact is nearing its end PSC's schedule for further remedial <br /> system operation is discussed in Section 4 2 of this report <br /> 7 <br /> Novembi i 2002 Ciro UndNN aI r Momtonn <br />