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SECTIONFIVE <br />5.3.3 Hydraulic Conductivity <br />Laboratory and Field Testing <br />Back pressure permeability tests were performed in the laboratory on two intact bedrock samples <br />from TH-19 and TH-22 in accordance with ASTM D-5084. The results of the tests aze provided <br />alongside the boring profiles in Appendix A, Figures A-3 and A-4, and in Appendix C. <br />As noted, packer permeability tests were conducted during drilling in one location in each <br />borehole at a minimum depth below top of bedrock of 2.5 fl. Each test was generally conducted <br />at pressures of 50, 75, and 90 percent of the estimated effective overburden pressure in five steps <br />starting at 50 percent stepping up to 90 percent then stepping back down from 90 percent to 50 <br />percent in two intervals. Increasing and decreasing the test pressure provides information over a <br />range of pressures and on the behavior of the joints such as continuity of fractures and opening <br />and closing of fractures relative to changes in pressure. In fourteen of the twenty-nine borehole <br />locations the bedrock did not take any water during the packer permeability test, which indicates <br />a hydraulic conductivity that is less than 1.0 x 10~' cm/sec. The results of the packer <br />permeability tests are summarized in Table 5.3. <br />5.4 GROUNDWATER AND POND WATER CHEMISTRY <br />One groundwater sample from TH-4 and one pond water (surface water) sample from the active <br />gravel pit south of the proposed reservoir were tested for pH, conductivity, calcium, magnesium, <br />and hazdness at STL Laboratory in Denver, Colorado under subcontract with URS. These <br />chemical properties were analyzed because they could affect the bentonite slurry mix quality <br />and/or long term performance of the slurry wall. The results of the groundwater and pond water <br />samples aze presented in Table 5.4 and Appendix C. The test results indicate that the chemical <br />concentrations in the surface water and groundwater are within the typically acceptable range for <br />bentonite slurry mix water and soil-bentonite backfill seepage water respectively. <br />N\PROJECTS\22238240_PLATTE_SAND_GRAVEL\SUB_00\12.0_WORD_PROO\PLATTESANDSGRAVELGEOTECHNICALDESIGNREPORT6ODOCVS-NOV-0S\\ S-2 <br />