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%/ <br /> Geologkal Tecwa la. <br /> 1107 7+St. <br /> Modesto,California 95354 <br /> (209)5224119/Fax#5224227 <br /> GTI Project No.: 750.3 <br /> GTI Project Name:City of Escalon D E C 12 2002 <br /> Mr. Doug Stidham <br /> City of Escalon ENVIRONMENT HEALTH <br /> P.O. Box 248 PERMIT/SERVICES <br /> Escalon,California 95320 <br /> RE: Vapor Extraction System Update <br /> City of Escalon(Former Arco Mini Mart), 1305 EsWon,Ave.,Escalon,CA <br /> Dear Mr. Stidham: <br /> This letter is to update you on the operation of the vapor extraction system at the Former Arco Mini <br /> Mart, 1305 Escalon Ave. in Escalon CA. The system has operated for a runtime of 226 days since its <br /> startup on February 5, 2002. In this time, it has removed and destroyed approximately 650 gallons of <br /> gasoline from the subsurface. <br /> Extracted vapor concentrations began decreasing in September and extraction rates have since decreased <br /> to approximately 9 pounds of gasoline per day. The latest groundwater monitoring event showed that <br /> only MW-1 contains any contamination and'it only has trace levels of xylenes. The data suggests that <br /> the VETS has been effective at removing the highly mobile portion of the plume. <br /> In their January 11, 2001, correspondence, SJC-PHS/EHD states that- "San Joaquin County has <br /> established that primary and secondary drinking standards, known as maximum contaminant levels, are <br /> appropriate cleanup goat's, at a minimum,for all contaminated underground storage tank sites within the <br /> county'. Data suggests that the site has reached this minimum goal. In,order to determine if significant <br /> levels of contaminates are still present in the soil of the site, GTT is going to perform a spike test. The <br /> VETS will be shut off tomorrow after the monthly air sampling is performed. The system will be down <br /> for two weeks and then restarted. Air samples will be collected an hour after restarting the VETS and 24 <br /> hours later. The spike in concentrations after the VETS has been off for two weeks and then the decrease . <br /> over a 24 hour period,will indicate how close the site is too closure. <br /> The results of the Spike Test will be reported in a VETS Summary Report that is currently being <br /> prepared. The report will contain a summary of all,of the data collected during operation of the VETS, <br /> calculations showing mass removal and estimated mass remaining and recommendations for closure or <br /> further remedial work. <br /> If you have any questions regarding this project,please call Ray Kablanow or myself at the office (209) <br /> 522-4119. <br /> Respectfixlly Submi ed, <br /> 4 <br /> i <br /> GEOLDOCAL 7ECXNICS INC <br /> Michael J.Niemi <br /> Project Geologist <br /> Cc: Lori Duncan—SJC PHS/EHD <br /> Heather Kuklo-SJVUAPCD <br /> Gordon Boggs—RWQCB-CVR <br />