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r , Mr. Kyle Christie April 4, 1995 iPage 4 malfunctions in the heater and vacuum units of the system. Vapors were extracted from wells VE-3, VE-4, and VE-6. The current, historical, and total concentrations of BTEX and TPH-G in the extracted soil vapor are shown in Table 4. Table 5 summarizes the status of the vapor extraction wells and analytical results from the individual wells. Vapor samples were collected from each of the individual wells during the fourth quarter of 1994. The soil vapor laboratory reports and chain-of-custody documentation are included in Exhibit B. Influent concentrations of TPH-G are steadily declining,which indicates the hydrocarbons beneath the site are being successfully remediated. During the fourth quarter, 381 pounds (61 gallons) of TPH-G (average is 4 pounds per day) were removed. No measurable benzene was removed during the fourth quarter. The SVETS will continue to be operated in a manner designed to remediate soil and soil vapors effectively and quickly by: • Concentrating extraction from areas with highest concentrations in vapor, as monitored by field instruments and periodic laboratory analyses of air samples. • Maximizing influent concentration to the catalytic oxidizer. Influent air samples are collected monthly and used to evaluate this criteria. Recommendations Based on the operation of the SVETS during the fourth quarter of 1994, the SUETS will continue to operate. However, Brown and Caldwell has proposed that due to the decline in soil vapor influent concentrations to the catalytic oxidizer and the lack of groundwater contamination at the site, the biofilter system be permitted to remediate the remaining low soil vapor concentrations at the site. On November 7, 1994, Authority-to-Construct Permit No. N-1081-1-1 for the biofilter system was issued by SJVUAPCD. Full-time, independent operation is scheduled to begin in the first quarter of 1995. In the interim, the SVETS and the biofilter will continue to work in tandem. Brown and Caldwell will continue to optimize the operation of the current SVETS to maximize removal rates and decrease the concentration of petroleum hydrocarbons in the soil and soil vapor beneath the site. • Use or disclosure of data contained on this sheet is subject to the restriction specified at the beginning of this document. l 3l S\R&P0RTSb4TH94q MjZpT