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,M 'A <br /> �: of ingtoRestoreNature <br /> 1710 Main Street <br /> Escalon, CA 95320 <br /> Phone (209}838-3507 � -',� December 1$, 1992 <br /> FAX (209)838-3509 J'i i i ' <br /> Mark Schoenhoff <br /> San Joaquin Valley Unified Air Pollution Control District <br /> 4230 Kiernan Avenue <br /> Salida, California 95368 <br /> RE: C.M. Weber Enterprises, Inc., Property <br /> 141 North El Dorado St., Stockton <br /> UAPCD Permit Nos. AP 91-467 and AP 92-111 <br /> Dear Mr Schoenhoff: <br /> This report summanzes 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. <br /> An internal combustion engine originally operated at the site from the end of January through <br /> mid-March, 1992. It was replaced during the week of March 16, 1992, with a 250 standard <br /> cubic feet per minute (SCFM) thermal oxidizer. The thermal oxidizer operated from March 31 <br /> to July 13, 1992 <br /> A Granulated Activated Carbon (GAC) system replaced the thermal oxidizer on July 21, 1992 <br /> and became operational on July 30. Due to an electncal malfunction in the blower, the system <br /> was not operating between October 4 and October 29. Repairs were made and the system was <br /> restarted on October 30. During the November 2 sampling event, effluent monitoring with a <br /> Phototonization Detector (PID) indicated that breakthrough of contaminants may have occurred <br /> and the system was shut down pending laboratory analysis of the samples. Analytical results <br /> confirmed that breakthrough had indeed occurred. The vapor extraction system will remain <br /> nonoperational until the carbon canisters are replaced. <br /> A sample of the influent air was collected for laboratory analysis on October 1 Both influent <br /> and effluent samples were collected on November 2. The samples were sent to Sequoia <br /> Analytical for analysis of total petroleum hydrocarbons as gasoline (TPHG) and benzene, <br /> toluene, ethylbenzene, and xylenes (BTEX). Analytical results for all samples are summarized <br />. in Table 1. Laboratory data sheets and chain-of-custody documents are provided in Attachment <br /> 1 <br /> VEER-Fr MRM <br />