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Geotechnical Responses to Cazier's Comments <br />March 11, 2011 Memorandum <br />PION <br />Response #4 <br />Footings for steel sets will bear on rock. The intent is to support all mill-related structures <br />on cut. <br />Comment <br />5. On page 3 of Exhibit E, Reclamation Plan, last paragraph states, "With the exception of the bench <br />out slopes and the portal face (1.5H.-IV), slopes will be reclaimed to 2(H):I(V) or to slopes no steeper <br />than the existing topography where the natural slopes are estimated to be 1(I1): I (V). Where <br />possible, slopes will be graded to approximate original contour. "Please provide clarification of <br />where IHJV slopes are proposed. <br />Response #5 <br />Graded slopes will not be steeper than 2(H):l(V). <br />Comment <br />6 The copy of design calculations presented in Attachment 6 5.1 are difficult to make out all <br />the numbers and nomenclature due to poor quality and the interference of the grid lines on <br />the paper. However, the legible portions of the calculations appear adequate for a <br />preliminary design. The Division will require specifications for the structural steel, rebar, <br />pipe supports, concrete, shotcrete, all thread and all associated hardware. The assumed soil <br />bearing capacity (4,500 psfi appears acceptable if the soil is similar to a gravel or gravel- <br />sand mixture. The Division will require a demonstration that this is indeed the case. The <br />calculations do not appear to include a factor of safety for the footing. Due to the mill housed <br />inside the portal, the steel set footings should have a factor of safety equal to at least 3.0. <br />The potential for geologic hazards (see Item 7) may necessitate a higher factor of safety. The <br />final design shall include as a minimum, evaluation of axial, bending, shear, and buckling of <br />the supports in uniform and nonuniform loading and support conditions. The maximum steel <br />stress shall not exceed 0.6 times the steel yield strength (fy). A safety factor appropriate for <br />the level of uncertainty and the nature of the construction shall be applied. Prior to <br />construction, the Applicant will be required to submit design drawings and specifications <br />that address the following: <br />a. Shop drawings of the portals, including as a minimum the limits of proposed <br />excavations and geometries of portal excavations in both plan view and in cross-section. <br />b. Detailed description of the procedures, equipment, and methods proposed to conduct <br />the portal excavations, including as a minimum: excavation sequence for the shaft and <br />portals; schedule of operations; methods of loosening rock; spoil removal system; and <br />personnel and equipment access. <br />c. Detailed shop drawings and descriptions of the procedures and methods proposed to <br />provide Ground Support, including as a minimum: Ground Support erection scheme; <br />Ground Support element descriptions, sizes, spacings, and strengths; and design <br />calculations. Calculations shall include loads, methods, assumptions, results, and safety <br />factors. Shop drawings and calculations shall be signed and stamped by a Registered <br />Engineer in the State of Colorado. <br />5/25/2011