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• The DCF has been load- and shear-tested against the 100 mil and 80 mil synthetic <br />liner material and all test results meet the minimum performance requirements detailed <br />in the Technical Specifications. <br />• The potential for the Soil Liner Fill to be more susceptible to an increase in <br />permeability due to alternating freezing and thawing as a result of the 2-foot DCF <br />thickness was examined based on published experiments and in-situ measurements of the <br />Soil Liner Fill used in 1994-5 after the Fill was subjected to a winter cycle during which <br />it had no cover. The lack of excess moisture in the 1996 clays, the lack of change in <br />density of 1994-1995 Soil Liner Fill material exposed under site-specific conditions which <br />indicates no change in permeability, and the safety factor provided by the increase in <br />effective stress upon loading of ore provide sTeorrc txorcaTtorts that the 2-foot layer <br />of Drain Cover Fill will not adversely affect the permeability of the underlying Soil Liner <br />Fill. In order to further demonstrate that the permeability of the Soil Liner Fill to be <br />used in 1996 will also not change substantially with two feet of cover, CC&V will <br />perform laboratory tests of the material in accordance with the test protocol provided as <br />Attachment 1. Should the test data demonstrate that the 1996 Soil Liner Fill material <br />experiences a detrimental increase in permeability and should this increase be <br />substantially greater than demonstrated by laboratory testing of the 1994-5 Soil Liner <br />Fill, CC&V will take appropriate measures to ensure that the Soil Liner Fill permeability <br />continues to meet the design specification of < 1x10 cm/sec for those areas of the Phase <br />II Cresson Valley Leach Area that might experience cyclical and detrimental freezing and <br />thawing. <br />• The 2-foot DCF will remain more than adequate to protect the underlaying synthetic <br />liner from degradation from sunlight. The 2-foot thickness was assessed as allowing no <br />more infiltration of ultraviolet energy than 3-feet. In 1996, all liner material in the Phase <br />II area will be Linear Low Density Polyethylene. Because this "LLDPE" has resistance <br />to photodegradation equivalent to HDPE, the timely covering increases the factor of <br />safety in this regard. <br />• The 2-foot cover has been calculated to provide a static load of at least 1.3 psi on the <br />surface of the liner, adequate to hold the liner in place should there be exposed edges that <br />might be lifted by strong winds. <br />• The ability of the 2-foot cover to adequately buttress the DCF material placed <br />progressively upslope was also examined. Both the case of stability of the synthetic liner <br />on the Soil Liner Fill and that for the stability of the DCF on top of the synthetic liner <br />were examined. The Factor of Safety ("FOS") for the first case was analyzed to be <br />slightly improved over that for 3-feet and the FOS for the second case was the same <br />regardless of the thickness. <br />• The dynamic loading of the synthetic liner during placement of DCF was analyzed, <br />as was the dynamic loading that would occur when the first lift of ore was placed on onto <br />4 <br />