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CRYSTAL CREAMERY STOCKTON <br /> 'rr WKA No. 1628.10 <br /> February 5, 2000 <br /> Page 9 <br /> Therefore, the actual radii of influence for the vapor extraction wells will likely be in excess of <br /> 23 feet. <br /> Based on the observed airflow rate in the vapor extraction wells and vacuum pressure drawdown <br /> in the observation wells during the pilot tests,vapor extraction is physically feasible at the site. <br /> However,because only minor concentrations of gasoline, toluene and total xylenes were detected <br /> in VEW1, use of vapor extraction technology as a remediation option may not be economically <br /> feasible for removing adsorbed-phase petroleum hydrocarbons beneath the site. ? ' <br /> Petroleum hydrocarbons were not detected in the pre-test or post-test water samples obtained <br /> during the pilot test. However, a significant increase in dissolved oxygen was recorded in the <br /> observation wells during the pilot test. Additionally,mounding of approximately 0.05 to 0.07 <br /> feet was recorded in the observations wells. Based on the above data and the distance to each <br /> Observation well, an air sparging radius of influence of approximately 10 feet may be achieved <br /> Y'sf <br /> beneath the site. <br /> Based on the recent phase II investigation to the northeast, the new well (MWS) appears to <br /> establish a near-zero line in this direction. With this new information, we now have wells <br /> surrounding the site that either report no detectable concentrations of the target analytes or report <br /> concentrations that are extremely low. Alternatively,the recent appearance of fuel oxygenates in <br /> a number of the wells maybe cause.for concern. This appearance, may,however,be linked to <br /> the lower detection levels reported by the analytical laboratory in most samples. <br /> The next quarter of groundwater monitoring and sampling is scheduled for March 2000. Our <br /> report for next quarter will be transmitted upon completion of laboratory testing. <br /> Limitations <br /> The statements and conclusions in this report are based upon the scope of work described <br /> above and on observations made on the date of our fieldwork on presented above. Our work <br /> was performed using a degree of skill consistent with that of competent environmental <br /> consulting firms performing similar work in the area. No recommendation is made as to the <br /> INK <br /> IWALi ACE�KUHL <br />