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w � Well destruction permits for the groundwater monitoring wells (MW1 through MW7) and vapor extraction wells (VEW1 andVEW2) will be obtained from the SJCPHS. k" WELL DESTRUCTION PROCEDURES A licensed California driller (Woodward Drilling of Rio Vista, California, C57 #710079) will be subcontracted by ET1C to destroy the wells. One of two methods, overdrilling or pressure grouting, will be employed to destroy the wells in accordance with the San Joaquin County Well Standards. The overdrilling technique will be used if(1) analysis of historic soil samples or the most recent groundwater samples contained detectable concentrations of hydrocarbons, or(2) the well is located in the street. The pressure grouting technique will be used if analysis of historic soil samples or current groundwater samples did not contain detectable concentrations of La hydrocarbons. Based on this, wells MWl, MW2, MW4, MW5, and VEW1 will be destroyed by pressure grouting, and wells MW3, MW6, MW7, and VEW2 by overdrilling. The wells will be sounded before destruction to determine if there are obstructions that interfere with well destruction procedures in accordance with the guidelines and requirements of the SJCPHS. Well construction details are provided in Table 1. Groundwater monitoring wells MWl, MW2, MW4, and MW5 and vapor extraction well VEW1 are constructed with 4-inch-diameter polyvinyl chloride (PVC) casings and screens (Table 1). The wells will be destroyed by pressure grouting with cement tremied from the bottoms. After �. tremie grouting, a hole at least one foot larger than the original borehole diameter will be excavated to 3 feet below ground surface and the PVC cut off 6 inches above the bottom of the excavation. The resulting borehole will be filled with neat cement grout, and the surface w., repaired in accordance with the requirements of the CSPWD. The depths of the wells, the original boring diameters, and the quantities of neat cement grout needed for well destruction are provided on Table 2. La Groundwater monitoring wells MW3, MW6, and MW7 and vapor extraction well VEW2 are constructed with 4-inch-diameter PVC casings and screens. The well construction materials 60 (casing, screen, filter pack, and seal) will be removed by overdrilling to 1 foot below the original depths (Table 1). The resulting boreholes will be filled with neat cement grout, and the surface repaired in accordance with the requirements of the CSPWD. The depths of the wells, the +-• original boring diameters, and the quantities of neat cement grout needed for well destruction are provided on Table 2. +-r REPORTING AND SCHEDULE Upon completion of field activities, a letter report summarizing well destruction procedures will be submitted to the SJCPHS, and DWR well destruction reports will be prepared for submittal. Fieldwork for the well destruction is tentatively scheduled for 26 April 2001. Completion of fieldwork is contingent on obtaining well destruction permits, and upon approval of this work plan by the SJCPHS. FrlProjecu5701371Pvlaster51Vp1�YPU3011Tezc.dac 2 �I