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I <br /> Working to Restore Nature <br /> 1710 Main Street <br /> Escalon, CA 95320 <br /> Phone (209) 838-3507 r July 13, 1992 <br /> FAX (209)838-3509 <br /> CO � J / I <br /> L1 <br /> Mark Schonhoff <br /> San Joaquin County <br /> Air Pollution Control District <br /> P O Box 2009 " <br /> Stockton, California 95201 J U 1_ 1 3 1E02 <br /> ENVIRONIVIENIAL ;LAL.Th <br /> PERMI (/SERVICES <br /> RE: C M Weber Enterprises, Inc , Property <br /> 141 North El Dorado St , Stockton <br /> APCD Permit No AP 91-467 <br /> Dear Mr Schonhoff <br /> This report summarizes the performance of the Vapor Extraction System located at the above <br /> referenced site (Figure 1) The vapor extraction system induces a vacuum in the subsurface via <br /> extraction wells which are screened from 5 feet below grade to 1-2 feet above the water table <br /> The induced subsurface vacuum increases the rate at which gasoline will volatilize making <br /> extraction of the contaminants feasible During the week of March 16, 1992, a 250 SCFM <br /> thermal oxidizer (ORS Environmental Equipment Model ORS798001) was installed at the site <br /> The thermal oxidizer replaced an internal combustion engine which operated at the site from the <br /> end of January 1992 through mid-March 1992 Start up for the thermal oxidizer occurred on <br /> March 31, 1992 <br /> The thermal oxidizer operates at a minimum destruction efficiency of 95% for influent petroleum <br /> hydrocarbon vapors However, laboratory analyses has determined that the destruction <br /> efficiency has not dropped below 99% The thermal oxidizer has operated a total of 1343 hours <br /> since start-up on March 31, 1992 A copy of the operational log is provided in Attachment 1 <br /> The average flow rate of extraction vapors was 150 SCFM and has never exceeded 250 SCFM <br /> The start-up influent vapor concentration was 4900 ug/l total petroleum hydrocarbons as gasoline <br /> (TPHg) The June 17, 1992 influent vapor concentration data shows that the concentration has <br /> dropped to 460 ug/l TPHg A graph showing the changes in the influent concentration overtime <br /> is presented in Attachment 2 A summary of the thermal oxidizer performance from March 31, <br /> 1992 through June 17, 1992 is presented in Attachment 3 <br /> All vapor extraction system monitoring has been performed according to the guidelines specified <br /> in the Air Pollution Control Board (APCD) permit No AP 92-111 Both influent and effluent <br /> THERMOXREP MAD <br />