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Soil from the next higher sample insert will be extruded and <br /> tested for elevated hydrocarbon concentrations using a Gastech <br /> Model 1238 combustible gas indicator (CGI) . The CGI readings <br /> will be recorded on the boring log. The remaining soil <br /> recovered will then be extruded from the sample insert and <br /> described in accordance with the Unified Soil Classification <br /> System. For each soil type, field estimates of <br /> density/consistency, moisture, color, grading, and soil type <br /> will be recorded on the boring logs. <br /> A.2 Monitoring Well Installation <br /> Ground water monitoring wells will be constructed of <br /> 4-inch-diameter, flush-threaded, Schedule 40 PVC blank and <br /> screened (0 . 020-inch slot size) casing in accordance with the <br /> technical specifications and requirements of the SJCEHD and <br /> the RWQCB. The screened interval shall be of sufficient <br /> length to allow entry of petroleum products and address any <br /> seasonal water level changes which may occur based on the <br /> existing monitoring wells at the site. <br /> The casing will be installed in a borehole drilled with <br /> 10-inch-diameter hollow-stem augers. The annular space <br /> surrounding the screened portion of the well will be <br /> backfilled with an appropriately-sized filter pack to <br /> approximately one foot above the top of the screened interval. <br /> SA maximum of one-foot thick bentonite annular seal will be <br /> placed above the falter pack and the remaining annulus will be <br /> grouted with concrete to the surface. Utility boxes will be <br /> installed slightly above grade to minimize infiltration of <br /> surface water. Locking well caps will be installed to ensure <br /> the integrity of the well. A permanent marker indicating well <br /> number, well depth, date of installation, and well owner will <br /> be attached to each well. <br /> Ae3 monitoring Well Development, Sampling, and surveying <br /> The newly installed monitoring wells will be initially <br /> developed to remove as much sand, silt, and turbidity as <br /> possible. Monitoring wells will be developed by purging a <br /> minimum of 10 casing volumes or until stabilization of pH, <br /> temperature, and conductivity parameters to ensure that <br /> formation water has entered the well casing. <br /> All purging, development, and sampling equipment that comes in <br /> contact with ground water will be triple-rinsed prior to <br /> each sampling event in successive baths consisting of an <br /> Alcanox (laboratory grade) solution, and deionized water <br /> rinses. Prior to sampling, all ground water monitoring wells <br /> will be checked for the presence of free-product or sheen <br /> (using an electronic interface probe) and purged a minimum of <br /> 3 to 5 casing volumes or until stabilization of pH, <br />