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Grand Island Resources,LLC Via; 2 <br /> Idaho Tunnel Portal—Slope Stability Analysis <br /> .rte <br /> fp to }� <br /> Photograph 1—Idaho Tunnel Portal prior to Rehabilitation <br /> The timbered tunnel entrance and area around the opening were excavated in November 2019 in order <br /> to stabilize the tunnel portal. This effort involved excavating approximately 25 feet into the hillside, <br /> installing soil anchors, and applying a layer of shotcrete of variable thickness (Photograph 2). This work <br /> was performed by Harrison Western Construction Corporation, a licensed contractor. <br /> The tunnel portal is being enlarged to a nominal 10-ft. x 10-ft. opening in order to replace the existing <br /> ground support which is failing and remove the loosened rock surrounding the present opening. The <br /> enlarged tunnel opening is supported by steel sets installed at 4-ft center-to-center spacing with full <br /> lagging on the back and ribs. The steel sets consist of W6x20 wide-flange I-beams and support posts. The <br /> lagging consists of 3-in. x 8-in. Douglas Fir planks. Grouted threadbar spillings were installed at 12-inch <br /> spacing above the tunnel opening prior to excavation. <br /> In December 2019 a roof collapse occurred a short distance into the tunnel during initial rehabilitation <br /> efforts by Harrison Western. The roof failure occurred in an 11-12 ft section of unsupported ground as <br /> the tunnel opening was being enlarged through a section of mixed soil and decomposed gneiss. The <br /> collapse completely blocked the mine opening, crushed the pipe carrying the flow of mine water, and <br /> daylighted in the slope below County Road 128 (Caribou Road), leaving a large remnant void above the <br /> tunnel opening which estimated to be approximately 65 cubic yards. <br /> .LC: 5/7/2020 <br />