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0 <br /> ENVIRONMENTAL AUDIT, INC. <br /> 1000-A Ortega Way <br /> Placentia,CA 92870-7162 �!1 <br /> 714/632-8521 nn <br /> 714/632-6754 FAX E-mail:.41olj efgni lauditinc.com <br /> X1ta2: 46 <br /> MEMORANDUM <br /> DATE: July 19, 2001 EAI PROJECT NO.: 1232 <br /> TO: Marty Hartzel <br /> RWQCB —Central Valley Region <br /> 3443 Routier Road, Suite A <br /> Sacramento, CA 95827-3003 <br /> CC: See Distribution List <br /> FROM: Boris Stolin <br /> SUBJECT: STATUS REPORT—REMEDIAL SYSTEM, WARDS STOCKTON <br /> CAO NO. 5-00-707 <br /> The remediation system was restarted on June 21, 2001, after installing a separate electrical <br /> meter, and testing of rotating equipment and control system. <br /> The system was placed in operation in a vapor extraction mode only, with all vapor extraction <br /> wells connected to the system. After one hour of operation, VOC readings from individual <br /> wells were taken; however, all readings were below the atmospheric background level. The <br /> VOC reading at the inlet of the oxidizer was in the range of 30 ppmv. A soil vapor sample <br /> was obtained from the oxidizer inlet. <br /> On June 22, 2001, air sparging was initiated using all air sparging wells. No substantial <br /> increase in VOC readings was recorded. Vapor samples were obtained from the oxidizer inlet <br /> and the stack. The system was left running in the air sparging and vapor extraction mode. <br /> The three vapor samples were delivered to Air Toxic LTD for TPH and BTEX analysis by <br /> EPA Method TO-3. <br /> On June 29, 2001,preliminary (verbal) data on the TPH concentrations in the samples was <br /> provided which indicated 44 ppmv for VES mode and 87 ppmv for the air sparging mode. <br /> Attached is the written laboratory report. Based on this information, the thermal oxidizer was <br /> shut down, and the remediation system has been operating in only a"pulsed" biosparging <br /> mode, i.e.,three days on and four days off. <br /> In our opinion,the low concentration of VOCs in extracted soil vapor is a result of high <br /> ground water level and relatively low concentration of dissolved hydrocarbons based on the <br /> latest ground water monitoring event data. EAI plans to continue to operate the system in the <br />