Laserfiche WebLink
• In summary, the HCR test results for the GeoComposite vs. coarse fraction reports a ratio of HCRe.m,, = 0.52 and a <br />hydraulic conductivity of the coarse fraction affected GeoComposite kGeo,,. coarse = 32 x 10"6 cm/sec. Similarly, the <br />HCR test results for the GeoComposite vs. slimes fraction reports a ratio of HCRslimes = 0.77 and a hydraulic <br />conductivity of the slimes fraction affected GeoComposite kGeo v. Slimes = 2.3 x 10"6 cm/sec. Even though results were <br />reported for both coarse and slimes fraction, it is almost certain that the majority of the GeoComposite will see <br />interface with the slimes fraction. See TRI's complete findings in the appendix of this Exhibit C. <br />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+DS+D, <br />(Dc/ke) + (Ds/ks) + (DINT) <br />where, q = seepage rate per unit area = W/min per ft2 <br />y = ponded water depth = 4 ft. (assumed maximum) <br />De = depth of coarse fraction = 10 ft. <br />DS = depth of slimes fraction = (varies) 4 ft. thru 78 ft. <br />Dl = depth of GeoComposite liner = 0.00855 ft. <br />ke = hydraulic conductivity coarse fraction = 1.34 x 10"4 ft/min. <br />ks = hydraulic conductivity slimes fraction = 6.89 x 10-6 ft /min. <br />lq = 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 W/min per ft2 < q <_ 2.74 x 10'5 W/min per ft or, <br />6.04 x 10"5 gal/min per ft2 < q 5 2.05 x 104 gal/min per ft2 <br />is These seepage numbers have been incorporated above in Table 1 - 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, cp = 24.1 ° which corresponds to a slope of 2.2h:1 v. <br />The sub-grade slope is less than this and provides for a factor of safety, FS = tan 9/tan ig = 1.4 (USACE 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, cp,oarse = 31.2° which corresponds to a <br />slope of 1.7h:Iv. The sub-grade slope is less than this and provides for a factor of safety, FSeOa1Se = tan yeoarse /tan is <br />= 1.8 (USACE Slope Stability). <br />For the slimes fraction TRI reports an interface friction angle, 9,limes = 23.2° which corresponds to a slope of <br />2.3h: l v. The sub-grade slope is less than this and provides for a factor of safety, FSslimes = tan (slimes /tan ig = 1.3 <br />(USACE Slope Stability). This result will be the controlling friction angle because the slimes fraction will have the <br />most interface with the linersystem. 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 summary, 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 />DBMS has confirmed that this will be adequate notice to arrange required construction inspections. <br />Page 27 of 35