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2 2 Groundwater Monitoring Well Installation <br /> Two (2) soil borings will be drilled to a depth of approximately 70 feet bgs for the installation of <br /> two groundwater monitoring wells The two proposed wells are to be located approximately 60 <br /> feet north and 60 feet northeast of VW-2 (Figure 2) These proposed wells are positioned to <br /> evaluate the lateral extent of impacted groundwater in a downgradient direction from the former <br /> USTs <br /> 2 2 1 Monitoring Well Installation <br /> The wells will be installed in 8-inch diameter soil borings drilled by a truck-mounted drill rig <br /> ' equipped with hollow stem augers Each well casing will consist of approximately 40 feet of two- <br /> inch diameter, Schedule 40, flush-threaded and machine-slotted (0 020-inch) polyvinyl chloride <br /> (PVC) well screen The well screen interval will extend from 30 to 70 feet bgs so that future <br /> ' fluctuations in the groundwater table elevation can be accommodated <br /> Blank PVC casing will thread into the top of the well screen and extend to the surface In each <br /> well, a filter pack of Monterey#3 graded and washed sand will be placed through the hollow <br /> stem augers as they are slowly retrieved and until the sand pack reaches approximately two (2) <br /> feet above the top of the screened interval Overlying the sand pack, two (2) feet of hydrated <br /> bentonite chips will be placed within the annular space between the borehole and the well <br /> ' casing Over the hydrated bentonite, a surface seal of 20 1 cement/bentonite grout mixture will <br /> be pumped from the surface through a tremae tube The top of the wells will be secured with <br /> water-tight locking caps and a 3-foot stovepipe well monument A well construction diagram is <br /> included as Figure 3 <br /> ' During drilling, a field geologist will log the soil cuttings for hydrogeologic and lithologic <br /> characteristics Since the soil borings are located outside of the defined plume of impacted sod, <br /> sod samples will not be collected for laboratory analysis The wells will be surged by the driller, <br /> following the placement of the sand pack and prior to the installation of the well seal <br /> All drilling equipment will be cleaned prior to arrival on site In addition, to avoid cross- <br /> contamination of borings, all appropriate downhole drilling equipment will be cleaned between <br /> borings <br /> 5 <br />