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01/19/98 14:35 W10 842 8370 CHEVRON U.S.A. Z004/004 <br /> Hunter, Brett(blhu) <br /> From: O'Brien,Aaron[SMTP:AOBPIEN@gmgw.coml <br /> Sent: Friday, November 14, 1997 2:10 PM <br /> To: Brett Hunter <br /> Cc: O'Brien,Kent <br /> Subject: West Benjamin Holt Update <br /> Brett: <br /> Here is the summary for the recent work completed by Geraghty&Miller <br /> at Chevron Service Station#9-4275. Two site visits were completed in <br /> September relating to the startup of the SVE system and performance of <br /> an influence test as required by the San Joaquin County Public Health <br /> Services for the Addendum to the Corrective Action Plan submitted in <br /> October_ Two additional visits were completed in October as described <br /> below for operation and maintenance of the soil vapor extraction and air <br /> sparging systems. <br /> A site visit was conducted on October 14 to determine individual <br /> e)draction well flow rates following the review of SVE performance. <br /> Flow rates varied significantly between wells. Adjustments were made at <br /> the manifold to reduce e=essive flow rates and improve low flow rates. <br /> Influent concentrations improved from 115 ppmvto 300 ppmvas measured <br /> by a Gastech combustible gas detector. Measurements of the system <br /> effluent were measured with a photoionization detector as required by <br /> the San Joaquin Air Pollution Control District. Each extraction well <br /> vault was also opened and examined for leaks in the vacuum extraction <br /> and air sparging lines. <br /> During the October 14 site visit,the control panel of the SVE unit was <br /> very warm,enhancing the possibility of an electronic failure that could <br /> lead to a system shut down. The pitot tube flow measurement device on <br /> the influent was also providing inconsistent flow readings for air flow <br /> into the SVE catalytic unit. These issues were remedied during a site <br /> visit on October 24 when a fan was installed in the control panel for <br /> cooling and a venturi flow meter was installed on the system influent <br /> for more accurate flow measurement. The influent during the October 24 <br /> site visit was 180 ppmv with a system flow rate of approxdmately 67 cfrn. <br /> One site visit is planned for November to retrieve an influent sample <br /> for laboratory analysis and to verify that the system effluent is in <br /> compliance with the air district. If you have any questions regarding <br /> the ongoing operation and maintenance activities,please do not hesitate <br /> to call <br /> Thanks, <br /> Aaron O'Brien <br /> I <br /> Page 1 <br /> i <br /> I <br /> I <br />