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k� KLEINFELDER <br /> 3 BACKGROUND <br /> t <br /> The Disco Remediation Area is the site. of a former gasoline service station located on the <br /> southern portion of the Del Monte site. The Disco Remediation Area was operated as a service <br /> station until the property was purchased by Del Monte in 1976. Del Monte never operated the <br /> service station. <br /> Three 10,000 gallon underground storage tanks (USTs) were identified on the Disco site. The <br /> USTs were removed in 1985, During the removal of the USTs impacts to soil beneath the tanks <br /> was noted. The soil was excavated and aerated on the site and backfilled into the excavation. In <br /> 1991, a soil and groundwater investigation began. That investigation included a soil gas survey, <br /> seven soil borings, and installation of eight monitoring wells. The results showed concentrations <br /> of Total Petroleum Hydrocarbon as gasoline (TPH-g) in the soil at depths ranging from 55 feet <br /> below the ground surface (bgs) to 75 feet bgs, and also in'the groundwater. <br /> In February 1995, a soil vapor extraction and air sparging system (SVE/AS) was installed and <br /> operated (CH2M Hill, 1995) at the site. An estimated 8,787 pounds of TPH-g was removed <br /> while the system was in operation up to November 1995. The SVEIAS was shut down due to <br /> rising groundwater levels above the SVE systems screened level, caused primarily by the <br /> shutdown of not only three Del Monte production wells, but also reportedly due to the shut down <br /> of numerous city municipal wells in the area. <br /> The main contaminants are TPH-g, benzene, toluene, ethylbenzene, xylene, and 1,2-DCA. The <br /> site is currently being monitored on a quarterly basis. Additionally, the soil vapor extraction <br /> system was replaced in 2003 by Kleinfelder and air sparge/ozone injection systems have been <br /> installed to further remediate the plume. In general, the source area (actual Disco site) began <br /> active remediation in May 2003 using the thermal oxidizer. In June, that portion of the <br /> remediation system began operating 2417. In July, the vapor extraction unit was converted from <br /> Thermal Oxidizer to Catalytic Oxidizer, and was operating continually.' Regarding the <br /> downgradient edge of the plume, the ozone injection system began consistent and continuous <br /> operation in the beginning of September 2003. <br /> l <br /> l <br /> 12280.MON/ST04R397 Page 6 or 13 <br /> ®2004,Kleinfelder,Inc May 11,2004 <br />