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Permeability and seepage rates through the tailings impoundment can now be modeled. According to Vick, the <br />seepage rate per unit area can be expressed as: <br />q= y+De+D,+D, <br />------------------------------ <br />(De/ke) + (D?k,,) + (Di/ki) <br />where, q = seepage rate per unit area = ft3/min per ft2 <br />y = ponded water depth = 4 ft. (assumed maximum) <br />D, = depth of coarse fraction = 10 ft. <br />D, = depth of slimes fraction = (varies) 4 ft. thru 78 ft. <br />D, = depth of GeoComposite liner = 0.00855 ft. <br />k, = hydraulic conductivity coarse fraction = 1.34 x 10"4 ft/min. <br />k, = hydraulic conductivity slimes fraction = 6.89 x 10-6 ft /min. <br />k, = hydraulic conductivity GeoComposite v. slimes = 4.53 x 10"6 ft /min. <br />This gives an average seepage rate ranging: 8.07 x 10-6 ft3/min per ft2 < q < 2.74 x 10-5 ft'/min per ft'` or, <br />6.04 x 10-5 gal/min per fe < q < 2.05 x 10-4 gal/min per ft2 <br />These seepage numbers have been incorporated above in Table I - Tailings Impoundment Water Balance <br />considering appropriate impoundment thickness intervals. <br />The GeoComposite was also subjected to interface friction testing. For the GeoComposite versus the textured 60 <br />mil HDPE Geomembrane, TRI reports an interface friction angle, 9 = 24. 1° which corresponds to a slope of 2.2h: Iv. <br />The sub-grade slope is less than this and provides for a factor of safety, FS = tan y/tan ig = 1.4 (USAGE Slope <br />Stability). See TRI's complete findings in the appendix of this Exhibit C. <br />Being the last liner layer, the GeoComposite was also tested for interface friction with the tailings, both coarse and <br />slimes fraction. For the coarse fraction TRI reports an interface friction angle, cpcoa,,e = 31.2° which corresponds to a <br />slope of 1.7h:1 v. The sub-grade slope is less than this and provides for a factor of safety, FSeoa,e = tan Tcoase /tan ig <br />=1.8 (USAGE Slope Stability). <br />For the slimes fraction TRI reports an interface friction angle, cp,,,me, = 23.2° which corresponds to a slope of <br />2.3h: I v. The sub-grade slope is less than this and provides for a factor of safety, FS,lime, = tan cp,t;me, /tan ig = 1.3 <br />(USAGE Slope Stability). This result will be the controlling friction angle because the slimes fraction will have the <br />most interface with the liner s sy,tem. See TRI's complete findings in the appendix of this Exhibit C. <br />The composite liner assembly was also subjected to puncture testing. A representative sub-grade soil sample was <br />prepared as specified in the Composite Liner Submittal. Loading conditions were taken assuming a depth of 88 feet <br />of deposited tailings (averaging 111 lbs/cu. ft. density) plus a 1.53 safety factor - a confining pressure approximated <br />at 105 lbs/sq. in. (15,000 lbs/sq. ft.). In sununary, under these conditions the 60 mil HDPE liner maintained its <br />integrity without puncturing. The average out of plane deformation was a span of 1.7 inches with a depth of 0.23 <br />inches. The full report can be seen in TRI/Environmental's reporting attached as an appendix to this Exhibit C. <br />Construction Scheduling: <br />Because of the incremental and phased installation of the Tailings Impoundment composite liner system, Venture <br />Resources will provide the DRMS with a minimum of 10 days notice prior to beginning installation activities. The <br />DRMS has confirmed that this will be adequate notice to arrange required construction inspections. <br />Leak Detection: <br />A monitoring well has been installed immediately down-gradient from the Tailings Impoundment Liner and <br />Leachate Collection System. This monitoring well will be sufficient to detect any breach or leaks in the composite <br />liner system. Any seepage and/or infiltration past the leachate collection system can also be detected here. A <br />monitoring well has also been installed up-gradient of the Tailings Impoundment. Testing done here provides a <br />baseline comparison with any results taken from the down-gradient monitoring well. See Exhibit E drawings for <br />monitoring well locations. A well construction detail schematic can be found above in section 6.3.3(1)(j). <br />Page 29 of 37