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Grand Island Resources,LLC 'a, <br /> Idaho Tunnel Portal—Slope Stability Analysis <br /> T <br /> pr�!I <br /> • <br /> 211 <br /> 000. <br /> Photograph 6—Regolith and colluvium exposed in the right(north)wing wall of the portal excavation. <br /> GIR has explored the first 200 ft of the Idaho Tunnel in order to investigate the corresponding ground <br /> conditions that can be anticipated during the rehabilitation efforts. Starting from the back of the last steel <br /> set,the existing ground support consists of timber sets with full lagging on the back and ribs for the next <br /> 41 ft,followed by rock bolts and chain link mesh. The timber sets retain loose soil and rock,obscuring the <br /> undisturbed ground. Loose blocky material has also fallen onto much of the chain link and pulled it from <br /> the roof in places. The ground mass and rubble observed consists of granular fragments of decomposed <br /> rock mixed with blocky pieces of rock,transitioning more to angular pieces of highly fractured weathered <br /> rock with increasing distance into the tunnel. Other than a change in the type ground support previously <br /> employed, there does not seem to be a well-defined point in the tunnel at which a change from <br /> "Decomposed Granite"to "Weak Hard Rock" occurs. It appears to be a gradual transition with some of <br /> each type of material found within the other. <br /> At approximately 200 ft from the new portal there is a collapse after which,the rock exposed in the sides <br /> of the tunnel (ribs)appears to be fresh and less fractured gneiss,the tunnel exhibits a more regular 6 ft x <br /> 6 ft opening,and there is no ground support visible. This is interpreted as the"Hard Rock with Fractures" <br /> indicated on Figure 1. <br />