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Quarterly Monitoring Results I This report summarizes first and second quarterly monitoring results,second quarter intrinsic bioremediation(ITB)demonstration results,and remediation progress based on observations,measurements,and analytical results from field sampling completed in February,April,and June 1996. This report is limited to a brief presentation of the data collected.At the completion of the fourth quarter of ITB data collection,a more detailed annual report will be prepared that will offer an analysis of quarterly data trends and an assessment of remediation progress. Background The Disco site,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 Parmaceast 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 PHS/EHD,it was discovered that 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 site. 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 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 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 at 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 Dei 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 Corrective Action Plan)that addresses both soil and groundwater contamination In } response to PHS/EHD's directive,Del Monte submitted a work plan(dated December 29, OIC:IpRoj ECTSIDELmoNTni age1ool-.we i