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Ms. Devra Lewis <br /> February 20, 2003 <br /> Page 4 of 6 <br /> Monitoring Well Installation <br /> Groundwater monitoring wells will be installed at appropriate downgradient locations depending <br /> on the results of the direct push groundwater sampling. Well locations will be selected for areas <br /> where direct push groundwater analytical results indicate the well will be adjacent to but outside <br /> of the leading edge of the plume. It is anticipated that this will require at least one well but no <br /> more than three. RETEC will provide CVRWQCB with a summary table of the direct push <br /> analytical results and a map with the proposed well location(s) for approval prior to well <br /> installation. <br /> Monitoring well installation activities will be performed in accordance with the standards for <br /> monitoring well construction and installation described in SOP 220, Monitoring Well <br /> Construction and Installation. Material specifications and completion depths will be recorded <br /> during well construction and documented in a Well Completion Log. All wells will be <br /> constructed in accordance with CVRWQCB guidelines and San Joaquin County Public Health <br /> Services requirements. <br /> Monitoring wells will be constructed with 2-inch, Schedule 40 polyvinyl chloride (PVC) casing <br /> and screen. The screen will consist of a 10-foot section of 0.010-slot screen with a flush- <br /> threaded 6-inch long bottom cap. Blank PVC casing will extend from the top of the screen to <br /> approximately ground surface. <br /> A clean, washed silica sand pack will be selected based on the lithologies encountered during <br /> geoprobe investigations. Previous monitoring well completions at the site have utilized a No. <br /> 2/12 RMC-Pacific sand or equivalent. The sand will be placed in the annulus between the well <br /> screen and the borehole wall from the bottom of the boring, and extend a minimum of 2 feet <br /> above the top of the screen. An annular seal consisting of 2 to 3 feet of bentonite pellets will be <br /> placed above the sand pack and hydrated. The remainder of the annulus will be backfilled with <br /> bentonite-cement slurry. <br /> Wells will be completed with either a conventional stick-up monument or a flush-mount <br /> monument, depending on the specific well location or adjacent site use. The wells will be fitted <br /> with a lockable well cap. A minimum 2-foot-thick cement surface pad with a 2-foot radius will <br /> be installed around each monitoring well. <br /> The drill rig mast and all downhole drilling tools will be steam cleaned on site prior to drilling <br /> the first monitoring well, and after each monitoring well is drilled and installed. Steam cleaning <br /> will occur in a designated decontamination area and drill cuttings and fluids will be managed as <br /> described in SOP 120,Decontamination. <br /> Well Development <br /> Monitoring well development activities will be performed in accordance with SOP 221, <br /> Groundwater Well Development. Monitoring wells will be developed using a bailer and/or a <br /> submersible pump combined with surging. The well will be surged for 5 minutes after every two <br /> borehole volumes of water have been removed. The temperature, specific conductance, <br /> turbidity, and pH of the well development water will be measured after every purged borehole <br /> volume. Development will be considered to be complete when the following conditions are met: <br />