2010-11-23_PERMIT FILE - M2009076

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Based on the worst case Coarse Fraction Friction Angle of <pcF,= 37°, the proposed maximum free-faced slope of the tailings impoundment of 1.5h : Iv ((psloPe 33.7°) will be satisfactory and stable over the long term. The Slimes Fraction is constrained and confined by the Coarse Fraction at the free face (see cross-section drawing Exhibit E 11). A unique geometry presents itself as the tails are impounded. As the tailings volume fills and Coarse/Slimes segregation occurs in an approximate proportion of 1.0 Coarse : 1.9 Slimes, the Impounded Slimes Fraction Angle builds at an average of 2.1 h : 1 v (cpimp( unded sliEnes- 25.4°). The worst case Slimes Fraction Friction Angle is cpsFA= 31.9°. This arrangement, too, will be satisfactory and stable over the long term. Using this CU analysis, a 1.5 factor of safety in determining the maximum confining pressure of 15,000 lb/ft', considering the relatively slow rate of tailings deposition, and assuming saturated conditions; Venture Resources is confident the analysis provides for a very conservative result. A further degree of Tailings Impoundment stability enhancement shall also be incorporated utilizing geosynthetic reinforcing fabric. Venture Resources has worked carefully with a leading geosynthetics manufacturer, Synteen Technical Fabrics, to develop a design that incorporates geogrid into the Tailings Impoundment to increase stability. Synteen's analysis considered multiple scenarios to model the Tailings Impoundment stability incorporating their SF350 Geogrid product (see Synteen SF350 specifications included within the appendix of this Exhibit C). These scenarios looked at both saturated and un-saturated states in both static and seismic conditions. Multiple levels of Tailings Impoundment buildout were also evaluated: buildout through Bench #2 and buildout through Bench #5. Below is a table summarizing the reported factors of safety at these varying conditions.- Inc r oratin S ntee» SF350 Factor of Safet Factor of Safet Reinforcing Static Analysis Seismic Analysis Un-Saturated ndtis out through Bench #2 2,10 1.47 Buildout through Bench #5 2.07 1,44 Saturated Conditions Buildout through Bench #2 1.67 1.10 Buildout through Bench #5 1.52 1.02 This clearly illustrates that the proposed design does indeed meet the un-saturated factors of safety prescribed by the DRMS on November 8, 2010, namely: Un-Saturated Tailings, Static Conditions -minimum Factor of Safety = 1.5 Un-Saturated Tailings, Seismic Conditions - minimum Factor of Safety = 1.1 Perhaps more importantly this also illustrates that considering saturated conditions the factors of safety are also largely met. The complete Synteen geogrid analysis has been included in the appendix of this Exhibit C. The Synteen SF350 geogrid is to be incorporated incrementally into the Tailings Impoundment in horizontal planes at a vertical spacing of 10' lifts, with the exception of Bench 43 which is to be spaced at 5' lifts. The geogrid shall overlap and lay over the Composite Liner System a minimum of 12 inches. Refer to the Exhibit E Drawing E11 for an illustration of this geogrid installation. Venture Resources and Synteen. Technical Fabrics have used a value of 0.12 for the peak ground acceleration of an earthquake with 2% in a 50 year return period in the seismic stability analyses. Please see the USGS Peak Ground Acceleration Map, 2% in 50year return period data attached as an appendix to this Exhibit C. ATT performed a series of Consolidation Tests to also look at tailings density characteristics during consolidation. ATT utilized ASTM D-2435 standards for this. The Coarse Fraction and Slimes Fraction were prepared to a 30% pulp density to mimic the target tailings discharge from the mill down the tailings pipeline. The results of this are as follows: Page 25 of 37