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May Day/Idaho Mine -Portal Repair Comments to April 18, 2011 Adequacy Responses <br />Page 3 <br />May 25, 2011 <br />Please note that the proposed design criteria (1.5H:1V) is steeper than the flatter angle of <br />repose (1.7H:1V). Also, during the June 30, 2010 inspection, tension cracks in the May <br />Day 1 bench were observed by the two DRMS inspectors present, who pointed out the <br />fracture and discussed their concern with the Wildcat representative. As such, DRMS <br />believes there to be sufficient evidence of potential instability to necessitate analyses to <br />demonstrate otherwise. Therefore, DRMS requires the operator to submit stability <br />analyses to demonstrate that the proposed benches will be stable under the proposed <br />design criteria while loaded with the expected mining/construction equipment. These <br />analyses shall have appropriate materials test data to support assumptions used for <br />analysis, including, but not limited to: unit weight, cohesion, and friction angle. <br />Additional Comments: <br />7. DRMS has not received engineering analyses, designs or specifications related to the <br />illegal mill constructed in the May Day 1 portal. The illegal mill has been identified as a <br />facility that uses designated chemicals and is therefore an Environmental Protection <br />Facility. As such, the mill is subject to regulation pursuant to Rules 3.1.5(5), 6.4.21(7), <br />6.4.21(10)a, 7.3.1, and 7.3.2. DRMS requires the applicant to submit the following: <br />a. Soil bearing capacity analysis for area under the mill, <br />b. Structural analysis for the footing or foundation itself to confirm that it is <br />sufficient to support the equipment weight without failure (usually excessive <br />cracking), <br />c. Design drawings, <br />d. Design specifications, <br />e. As-built report sealed by a professional engineer certifying construction was <br />accomplished in accordance with drawings and specifications. <br />The March 11, 2011 General Portal Repair Comments memorandum comment #6 included the <br />discussion below. DRMS has not received a response to this comment. To reiterate comment <br />#6, DRMS requires the following documentation. <br />Attachment 6.5.1 Lamb and May Day No. 1 Steel Set Geotechnical Stability Assessment: <br />8. The copy of design calculations presented in Attachment 6.5.1 are difficult to make out <br />all the numbers and nomenclature due to poor quality and the interference of the grid <br />lines on the paper. However, the legible portions of the calculations appear adequate for <br />a preliminary design. The Division requires specifications for the structural steel, rebar, <br />pipe supports, concrete, shotcrete, all thread and all associated hardware. The assumed <br />soil bearing capacity (4,500 psf) appears acceptable if the soil is similar to a gravel or <br />gravel-sand mixture. The Division requires a demonstration that this is indeed the case. <br />The calculations do not appear to include a factor of safety for the footing. Due to the <br />mill housed inside the portal, the steel set footings should have a factor of safety equal to <br />at least 3.0. The potential for geologic hazards may necessitate a higher factor of safety. <br />The final design shall include at a minimum: evaluation of axial, bending, shear, and <br />buckling of the supports in uniform and nonuniform loading and support conditions. The <br />maximum steel stress shall not exceed 0.6 times the steel yield strength (fy). A safety <br />factor appropriate for the level of uncertainty and the nature of the construction shall be <br />mAminltc1\m-1981-185 maydayidaho\portalcomments2_mem25may11.docx