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4 GROUNDWATER INVESTIGATION WORKPLAN <br /> To collect the appropriate data needed to evaluate the groundwater quality at the Site, the <br /> following activities are proposed: <br /> • Removal of four pre-existing wells; <br /> • Install new upgradient, off-site groundwater monitoring wells; <br /> • Develop, purge, and sample the groundwater monitoring wells; and <br /> • Conduct data evaluation. <br /> Further details regarding these activities are provided in the following subsections. <br /> 4.1 PREFIELD ACTIVITIES <br /> Prior to conducting field activities, Miller Brooks will contact Underground Service Alert to locate <br /> and identify underground lines (gas, water, fiber optic, etc) on the Site. In addition, a <br /> geophysical survey will be conducted to further identify any potential subsurface interference(s) <br /> to drilling. On behalf of Cove Contractors, Miller Brooks will obtain the necessary well permits <br /> from San Joaquin County and traffic control permits form the City of Stockton prior to <br /> conducting the groundwater monitoring well destruction and installation. Copies of permits will <br /> be provided to the RWQCB after this workplan has been approved. <br /> 4.2 GROUNDWATER MONITORING WELL FIELD ACTIVITIES <br /> 4.2.1 DESTRUCTION <br /> As mentioned previously, the workplan proposes the removal of four monitoring wells. <br /> Monitoring well destruction will be in accordance with California Department of Water <br /> Resources Bulletin 74-81, Water Well Standards:State of California and its supplement Bulletin 74- <br /> 90, California Well Standards. Over-drilling will be the method used to remove each monitoring <br /> well. In over-drilling a large-diameter hollow-stem auger or direct rotary techniques are used to <br /> drill around the casing. Over-drilling, with a diameter at least two inches larger than the casing, <br /> will be conducted to the full depth of the previous boring. Upon removal of the casing, the hole <br /> will be reddled at a diameter larger than the original boring to remove annular sealant and filter <br /> pack materials. The volume of the borehole will be calculated to determine the appropriate <br /> amount of sealing material used to fill the borehole. Finally, the upper 5 feet of the boring will be <br /> filled with bentonite cement to provide a solid surface seal and cover. <br /> 5 `�AMLLEN MWOOKAF <br /> a� <br /> P:\707 Cove Contractors\WDR\Tech Report and WP 2008\Tech Report and WP_FINAL.doc <br />