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f Prior to the switch in groundwater flow directions,the extent of the plume was defined horizontally by <br /> monitoring wells MW-DIS-3,MW-DIS-8S,MW-DIS-9,and MW-DIS-10;and vertically by monitoring well <br /> MW-DIS-713 and-8D. <br /> `I <br /> Since 1991,Dei Monte has conducted quarterly groundwater monitoring and reported results to <br /> PHS/EHD. In February 1995,Del Monte initiated remediation at the Disco site by g installin an air <br /> sparging and soil vapor extraction (AS/SVE)system. The system consisted of two sets of AS/SVE wells <br /> and two sets of nested piezometers. The system was shut down in November 1995,when rising <br /> groundwater levels submerged the SVE wells. An estimated 8,787 pounds of TPH-gasoline were removed <br /> during the period of system operation,however,as indicated by the quarterly monitoring results at the <br /> site,elevated concentrations of gasoline constituents are still present in groundwater in the former tank <br /> and pump area. <br /> An additional site investigation was conducted in 1999 to attempt to define the vertical extent of <br /> petroleum constituents in groundwater beneath the former tank and pump area and define the <br /> downgradient lateral extent of petroleum constituents in groundwater. This investigation identified the <br /> presence of 1,2-DCA approximately 400 feet downgradient of the site and approximately 100 feet below <br /> ground surface. Additional site characterization is needed to further define the extent of 1,2-DCA. Also, <br /> as a result of the 1999 additional investigation,an interim remedial measure will be initiated to attempt to <br /> hydraulically control the source area of the plume. <br /> SECTION 3 <br /> Cone Penetrometer Testing (CPT) Investigation and <br /> Well Installation <br /> This section presents the sampling methodologies and procedures to be followed for the CPT <br /> Investigation and the well installation activities which will be conducted during this focused field <br /> investigation. Discussion includes the number of samples to be taken,number of wells to be installed,and <br /> the recommended analyses for each sample. <br /> 3.1 CPT Investigation <br /> 3.1.1 Cone Penetrometer Testing (CPT) <br /> All borings installed during this field investigation will be installed using a CPT direct push rig. CPT <br /> lithologic logging will be conducted using a standard electronic piezocone (CPTU). CPTU measurements <br /> of cone bearing,sleeve friction,and dynamic pore water pressure will be recorded at 5 cm intervals for <br /> the entire length of each boring. CPTU measurements will identify the locations of sandy zones in the <br /> aquifer which will be used to identify optimal locations for the collection of groundwater samples. <br /> CPT borings will be installed at seven locations downgradient and cross-gradient of the Disco site as <br /> shown on Figure 2. Two borings will be installed on the west side of Filbert Street, one north of Highway <br /> 4, and one south of Highway 4. One boring will be installed on the east side of Filbert Street,south of <br /> Highway 4. Four borings will be installed on Lafayette Street,southeast of the Disco site.The <br /> l: downgradient borings will be installed approximately 1,000 feet downgradient from the former tank and <br /> pump area,spaced approximately 200 feet apart. CPT logs will be obtained in each of the borings to a <br /> l <br /> CATEMPMORKPuwN_DCA 1.Doc 4 <br />