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i Quarterly Monitoring Results This report summarizes quarterly monitoring results,fourth quarter intrinsic bioremediation (ITB)demonstration results,and remediation progress based on observatiotis;measurements,and analytical results from field sampling completed in i December4996. As discussed with San Joaquin County, Public Health Services staff,Del Monte.has conducted a fourth quarter ITB sampling to complete this one year demonstration. Background The Disco property,located near the intersection of Myrtle Avenue and Filbert Street in Stockton,California,is the location of three former 10,000-gallon gasoline tanks(Disco tanks)that released gasoline constituents into the soil and groundwater (Figure 1).The Disco property and tanks are associated with a former gasoline station that was owned by Parmaceast from the mid-1960s to 1976. Del Monte Foods purchased the Disco property from Parma east on April 1, 1976;however,Del Monte never operated or utilized the Disco tanks. When Del Monte removed the Disco tanks in 1985,as directed by the San Joaquin County Public Health Services/Environmental Health Division(PHS/EHD),it was discovered that j the tanks.had released gasoline into the surrounding soils. At the time of removal,the Disco tanks contained water. Soil beneath the tanks was analyzed and found to contain gasoline constituents. Soil containing the gasoline constituents was aerated onsite to reduce levels of volatile hydrocarbons. The aerated soil was backfilled into the excavation. The results of the tank removal are presented in Del Monte's Tank Excavation Report (Exceltech, 1985). In 1991,at the direction of the PHS/EHD,Del Monte began an investigation of the soil and groundwater in the vicinity of the Disco property. Del Monte retained CH2M HILL to conduct the investigation. The investigation consisted of a soil-gas survey to assess the extent of volatile-fuel constituents in the shallow soil,seven soil borings to assess fuel J constituents in the soil,and the installation of eight monitoring wells to evaluate fuel constituents in the shallow and deep groundwater. The investigation revealed the presence y of gasoline constituents in the soil and groundwater. Most of the soil contamination was found below the former tank pit near the groundwater table,between 55 and 75 feet below ground surface (bgs). Significant concentrations of gasoline constituents,including benzene of up to 32 mg/L,were detected in the groundwater. The results of this investigation and a feasibility study are presented in Del Monte's Remedial Investigation/Feasibility Study(RI/FS) (CH2M HILL, 1992). PHS/EHD'further directed Del Monte to define the extent of contamination,install an up- gradient monitoring well and a down-gradient monitoring well pair (one shallow and one deep),conduct aquifer pump tests,and prepare a Final Remediation Plan (also known as a f Corrective Action Plan)that addresses both sail and groundwater contamination. In response to PHS/EHD's directive,Del Monte submitted a work plan (dated December 29, sFOlG:TROJECTSVELMONTEIPLANT 331QRPT2_971QTR_REP.DOC