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10 <br /> All water samples will be labeled, stored, and transported as described in the soil <br /> sampling section above. The water samples will be submitted to BCAL for analysis of BTX <br /> and TPH by EPA Method 8015, modified, Extraction Method 5030. <br /> Installation of an Off-Site Groundwater Monitoring Well <br /> This section describes the methods for monitoring well construction, development, and <br /> sampling. GLDM will be responsible for proper well abandonment when the Regional Board <br /> and/or the County determines that monitoring groundwater quality is no longer necessary. <br /> Bnrehole Drilling. BC will supervise the drilling of one off-site soil borehole zrid ac;, <br /> installation of a groundwater monitoring well in the borehole (see Figure � . The borehole <br /> will be drilled using a truck-mounted drilling rig equipped with &inch-outs;lcic-diameter, <br /> hollow-stem augers. Borehole depth is expected to be 70 feet. borehole ci.,%:jjgs will be <br /> contained in 55-gallon drums and ternporarily stored at the site. The disposal of these drill <br /> cuttings is the responsibility of GLDM. <br /> Soil Sampling. Soil sarr.gles for lidtologic cla.;sification and for laboratory analysis will <br /> be collected and handled in the same manner as that described above for the soil- <br /> characterization soil sampling. <br /> Construction of Monitoring Well. The monitoring well will be completed with 30 feet <br /> of nominal 2-inch-diameter, PVC, 0.020-inch slot'Led flush-threaded casing. The slotted casing <br /> wil: extend approximately 20 feet below the groundwater surface and 10 feet above. This <br /> design will accommodate any seasonal groundwater level fluctuations that might occur at the <br /> site. Blank casing will extend from the top of the perforated section to ground surface. <br /> PVC caps will be installed at the top and bottom of the well. Actual depth of the borehole <br /> and screened interval will depend on the conditions encountered during drilling. The well <br /> will be packed with No. 1/20 sand from the bottom of the screen to approximately 2 feet <br /> above the top of the screen. A 2-foot-thick layer of bentonite pellets will be placed on the <br /> top of the sand pack. The remaining annular space will be grouted with bentonite-cement <br /> slurry placed by tremie pipe. The well will be completed at grade using a water-ti& locking <br /> cover. Typical well construction is illustrated on Figure 4. <br /> Well Development. The well will be developed by surging, bailing, or pumping until <br /> clean, sediment-free water is produced from the well. The length of development time will <br /> vary depending upon field conditions. Water produced during development and sampling will <br /> be contained in 55-gallon barrels. GLDM will be responsible for the disposal of water and <br /> any recovered petroleum product. Prior to and following development, the depth to water will <br /> be measured with an oil/water interface probe, <br /> Groundwater Sampling. Prior to sample collection, at least three well volumes of <br /> groundwater will be removed. A well volume is defined as the amount of groundwater in the <br /> well casing and the sand pack with an assumed porosity of 35 percent. The pH and electrical <br /> conductivity of the water will be mEasured periodically prior to sample collection. <br />