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WORK PLAN FOR DESTRUCTION OF GROUNDWATER MONITOR WELLS VALLEY MOTORS 800 East Main Street Stockton, California 1.0 INTRODUCTION Nine groundwater monitoring wells, one air sparging well, and one vapor extraction well (Figure 1)were drilled under the supervision of Upgradient Environmental Consultants during a 20-year investigation and remediation of soil and groundwater contamination at 800 East Main Street in Stockton, California. The contamination was first detected when two underground gasoline storage tanks were removed from the sidewalk west of the property in 1992. Ga§oline-impacted soil was observed in the tank pit,prompting San Joaquin County Environmental Health Department to require further investigation. Mr. Michael Infurna of EHD directed the investigation until his retirement in 2012. After that time, Mr. James Barton of the Central Valley Regional Water Quality Control Board assumed responsibility for regulatory oversight. When the first monitor well was drilled in 1995,the depth to groundwater exceeded 50 feet and the well was drilled to a depth of 75 feet. The next two were drilled in 1996 to a depth of 60 feet, and the fourth well (VM-4)was drilled in 1998 to a depth of 75 feet but was backfilled with grout to a depth of 60 feet before the well was constructed. The vapor extraction and sparging wells were drilled in 2000 to a depth of 30 feet. Groundwater began rising after that and later wells were drilled to 35 or 40 feet and completed with 15 feet of screened casing to 25 feet. ' 2.0 WELL DESTRUCTION PROCEDURES Soil and water samples (Table 1 and Table 2)collected from VT-1 and VM-8 during drilling were all non-detect for petroleum hydrocarbons. Accordingly, these wells will be abandoned by pressuring grouting with neat cement from total depth to surface and the Christie boxes will be removed. Wells VM-1, VM-2 and SW-1 had soil samples that were gasoline compounds and will be over drilled with 10"diameter augurs. VM-3 through VM-8 had no soil samples that were impacted with gasoline compounds but water samples were impacted and will also be over drilled. No soil samples were obtained during the drilling of VM-9 but this well was installed in the heart of the contamination plum and it is likely this well would have had contaminated soil samples but was impacted by water contamination and it will be over drilled with 10"diameter augers: All drill cuttings will he placed in 55-gallon drums for-disposal. The wells will then be grouted to surface using tremie. The well abandonment will be done by V&W Drilling under the supervision of Upgradient Environmental. San Joaquin County EHD will be notified of the scheduled date for abandonment at least one week prior to mobilization.