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KLEIN FELDER 3 BACKGROUND 1 I The Disco Remediation Area is the site of a former gasoline service station located on the southern portion of the Del Monte site. The Disco Remediation Area was operated as a service station until the property was purchased by Del.Monte in 1976. Del Monte never operated the service station. Three 10,000 gallon underground storage tanks (USTs) were identified on the Disco site. The USTs were removed in 1985. During the removal of the USTs impacts to soil beneath the tanks was noted. The soil was excavated and aerated on the site and backfilled into the excavation. In 1991, a soil and groundwater investigation began. That investigation included a soil gas survey, seven soil borings, and installation of eight monitoring wells. The results showed concentrations of Total Petroleum Hydrocarbon as gasoline (TPH-g) in the soil at depths ranging from 55 feet below the ground surface (bgs)to 75 feet bgs, and also in the groundwater. Del Monte, under PHS/EHD direction, conducted a soil and groundwater investigation in 1991 at the site. The assessment consisted of a soil-gas survey, seven soil borings, and the installation of eight monitoring wells. The results from the assessment indicated gasoline constituents in soil and groundwater at depths of 55 to 75 feet bgs. i Dei Monte has conducted quarterly monitoring since 1991. Since 1991 to July 1994, the groundwater flow direction was reported as being to the northwest with an average gradient of 0.0006 ft/ft. From October 1995 the flow direction changed from northwest to southeast with a reported average gradient of 0.001 ft/ft. The switch in flow direction was due to the shutdown of three Del Monte production wells, and reportedly by the shutdown of numerous city municipal wells in the area. In February 1995, a soil vapor extraction and air sparging system (SVE/AS) was installed and operated (CH2M Hill, 19 95) at the site. An estimated 8,787 pounds of TPH-g was removed while the system was in operation up to November 1995. The SVE/AS was shut down due to rising groundwater levels above the SVE systems screened ,level, caused primarily by the shutdown of the Del Monte production wells, and also the numerous city municipal wells previously mentioned. The main contaminants are TPH-g, benzene, toluene, ethylbenzene, xylene, and 1,2-DCA. The site is currently being monitored on a quarterly basis. 12280.MON/ST02R519 Page 5 of 14 ©2002,KleinkIder,Inc September 19,2002