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22 October 1996 <br /> AGE-NC Project No. 95-0100 <br /> ' Page 5 of 9 <br /> During most of the test,vacuum readings at the extraction well (VE-1)ranged between 1.4 and 2.35 <br /> ' inches of water. At VE-2, located 15 feet southeast from VE-1, the initial vacuum was 0.07 inches <br /> of water, measured from the lower screen interval. After four hours the influence increased to 0.085 <br /> ' inches. After 5.5 hours, vacuum readings at the upper and lower intervals were 0.05 and 0.07 inches <br /> of water, respectively. At the end of the test (8.0 hours), the influence measured at the upper and <br /> lower screens were 0.065 and 0.08 inches of water. <br /> ' The vacuum measured at VE-2 waslotted t versus distance sante from the extraction pont (VE-1) on a <br /> semi-logrithmic scale. The graph represents the theoretical radius of influence of the extraction well. <br /> ' In soil at the site (sandy-gravel)it appears that a vacuum of 0.1 would be great enough to volatilize <br /> hydrocarbons. A theoretical radius of influence of approximately 15 feet could be derived from the <br /> graphed data. In practical application, an effective radius of influence of approximately 10 feet is <br /> more likely to occur. <br /> ' A relatively low flow rate was achieved during the pilot test due to the poor performance of the IC <br /> engine. The engine was limited because of low levels of free oxygen in the soil and the relatively• <br /> high concentrations of extracted carbon dioxide, therefore, a high volume of supplemental fuel <br /> (propane) was required to operate the unit at optimum rpm§. <br /> 2.7.5. ANALYTICAL RESULTS OF VAPOR SAMPLES <br /> Four soil vapor samples were submitted for laboratory analysis. TPH-g was detected at <br /> concentrations ranging from 19,000 ppb to 24,000 ppb. BTE&X were detected in the vapor samples <br /> at concentrations ranging from 220 ppb (ethylbenzene, VS-1) to 2,600 ppb (toluene, VS-3). <br /> 2.7.6. CORRECTIVE ACTION PLAN RECOMMENDATIONS <br />' The findings from the site specific investigations for soil remediation feasibility indicted that soil <br /> vapor extraction would rapidly reduce the mass of contaminates. AGE prepared a Corrective Action <br /> PIan (CAP) dated 06 December 1995 that recommended initiation of a soil vapor extraction system, <br /> utilizing the soil vapor wells installed and possibly one additional well to aid in the rapid removal <br /> and destruction of hydrocarbon vapors. <br /> - -- -The PHS=EHD'requesfed-by letter serf 25 April`1996 that the property owner's consultant perform <br /> a risk-based decision computer modeling of the site specific conditions to betterAssess the need for <br /> active remediation. The PHS-EHD also requested that a revised CAP or.a Closure Summary-Report <br /> • following the Central Valley Regional Water Quality Control Board guidelines be submitted-to the <br /> PHS-EHD incorporate the results of the risk.based computer model. This report incorporates several <br />