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GEt ENyIRO SERVICES, INC. <br /> October 21, 2009 <br /> Project No. 07-132 <br /> San Joaquin County Environmental Health Division <br /> 600 East Main Street <br /> Stockton, California 95202 <br /> Attention: Mr. Harlin Knoll <br /> Senior REHS <br /> Subject: Corrective Action Pian Addendum <br /> Former EZ-Serve 100966, 2531 Waterloo Road, Stockton, California <br /> SJCEHD Site Code: 1757 <br /> GeoEnviro Services, Inc. (GESI) previously prepared an interim corrective action plan (ICAP) <br /> dated April 18, 2008 for soil and groundwater remediation at the former EZ-Serve Station No. <br /> 100966 located at 2531 Waterloo Road, Stockton, California. This interim ICAP was approved <br /> by the San Joaquin County Environmental Health Department in their letter dated May 30, 2008. <br /> Implementation of the ICAP was completed between October 2008 and January 2009. ICA <br /> activities completed included the installation of extraction and groundwater air sparge wells and <br /> the completion of high vacuum dual phase extraction (HVDPE) with groundwater air sparging <br /> (GWAS) for a period of 63-days using a mobile system. The results were documented in a <br /> report prepared by GESI dated March 31, 2009. <br /> Based upon the results of HVDPE activities completed between November 28, 2008 and <br /> January 30, 2009, GESI made the following observations and conclusions: <br /> o The 63-day HVDPE / GWAS event was successful in removing an estimated 7,616.41 <br /> pounds or 1219.11 gallons of hydrocarbons from the soil beneath the Site. The average <br /> rate of hydrocarbon extraction was approximately 5 pounds per hour. In addition, <br /> 148,250 gallons of hydrocarbon-affected groundwater were extracted, treated through <br /> granular activated carbon, and removed from the Site. <br /> o Concentrations of volatile hydrocarbons in the extracted soil vapor decreased during the <br /> 63-day extraction event from the highest combined flow concentrations of TPHg and <br /> benzene of 3,100 ppmv and 23 ppmv on December 31, 2008 while extracting from wells <br /> YEAS-3, VEAS-4, and EX-1 to final concentrations of TPHg and benzene of 1,860 ppmv <br /> and 0.77 ppmv, respectively on January 28, 2009 while extracting from wells VEAS-2 <br /> and VEAS-3 (Table 3). These results indicate a 40 percent decrease in TPHg <br /> wn0entration and a 97 percent decrease in benzene concentration in the extracted <br /> vapor. <br /> o Vammirn readings In observation wells while extracting from wells YEAS-3, YEAS-4, and <br /> VIEkS-5 indicates the radius of influence is greater than 20 feet. <br /> 5529 Kailas Street - Ventura • CA • 93003 - T 805 , 642 , 1668 - F 805. 642, 9331 <br /> PO Box 7330 + 'Ventura - CA - 93006-7330 <br />