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Grand Island Resources, LLC Page 3 <br />Idaho Tunnel Portal – Slope Stability Analysis <br />Applied GeoLogic LLC 5/7/2020 <br /> <br />Photograph 2 – Current Condition of the Idaho Tunnel Portal. The three safety cones and caution tape <br />at the top of the slope mark the edge of Country Road 126 (Caribou Road). The crown hole over the <br />void is visible between the two small trees above the portal. <br /> <br />1.1.3. Collapse Repair <br />In late February 2020, two additional new steel sets were installed in the area of the tunnel portal beneath <br />the collapse and lined with lagging on the ribs and back. As with the initial two steel sets, these consisted <br />of W6 x20 wide flange steel beams and posts installed on 4-ft center-to-center spacing. Lagging consisted <br />of 3-in. x 8-in. treated Douglas Fir planks. This design and installation were inspected and approved by <br />Mr. David Hallman, a geological engineer with 37 years of experience and registered as Colorado <br />Professional Engineer No. 26076. <br />The narrow gap between the new ground supports and the existing ground was been closed using pieces <br />of lagging, plywood, polyurethane foam, and caulk to create a tight seal. The remaining void created by <br />the portal collapse will be backfilled with pervious cellular concrete to provide permanent ground support <br />that will stabilize the slope and allow drainage. <br />The completed cellular concrete backfill will be significantly stronger than the soil which originally <br />comprised the slope while imposing only a fraction of the weight. This will serve to increase stability of <br />the slope below the county road. The flowable nature of the backfill will allow it to completely <br />encapsulate the tunnel lining system in a solid mass to create robust permanent support for the mine <br />entrance. The previous nature of the backfill will allow groundwater to freely drain from the slope in <br />order to ensure long-term stability.