2011-09-09_REVISION - M1981185 (43)

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Mr. Wallace H. Erickson Response to August 19, 2011 Cazier Memorandum September 9, 2011 Page 6 Response to Adequacy Issue No. 8. Wildcat will correct this reference to Attachment 6.5.4. Adequacy Issue No. 9. Page 6, Bench Stability. DRMS commented on this in the May 25, 2011 Memorandum from Tim Cazier to Wally Erickson. Neither the comment, nor the response from the applicant has changed: the applicant states "Existing mine benches were created in the early 1900's with no signs of failure or instability." Furthermore, it is stated that "the angle of repose of the benches range from 30 to 35 degrees ... " and that "in the future operating and reclaimed bench and waste rock slopes of 1.5 (H) to 1(V) will be used as design criteria." The stated angle of repose (30 to 35 degrees) equates to 1.4H :1V to 1.711: 1V. Please note that the proposed design criteria (1.5H: 1V) is steeper than the flatter angle of repose (1.7H:1V). Also, during the June 30, 2010 inspection, tension cracks in the May Day 1 bench were observed by the two DRMS inspectors present, who pointed out the fracture and discussed their concern with the Wildcat representative. As such, DRMS believes there to be sufficient evidence of potential instability to necessitate analyses to demonstrate otherwise. Therefore, DRMS requires the operator to submit stability analyses to demonstrate that the proposed benches will be stable under the proposed design criteria while loaded with the expected mining /construction equipment. These analyses shall have appropriate materials test data to support assumptions used for analysis, including, but not limited to: unit weight, cohesion, and friction angle. Response to Adequacy Issue No. 9. Wildcat has proposed an engineering and geotechnical analysis of the May Day No. 1 bench at Page 4 of Attachment D -2 (Portal Collapse Repair Work Plan). Wildcat will revise Exhibit 6.5 to add a third paragraph to the Bench Stability section at Page 6, as follows: In order to confirm the stability of the benches at May Day No. 2, May Day No. 3 and the Idaho Affected Area, and to assess the need for any stabilization at these benches, prior to performing any rock storage activities, Wildcat will implement a geotechnical work plan consisting of performing a review of existing data, subsurface investigation, laboratory testing, engineering analysis, conclusions regarding bench stability, rock storage area stability, and design criteria recommendations. Specifically, Wildcat will perform the following: • Drill test borings to 20 to 40 feet or refusal at locations identified by an engineer /geologist during a site visit. An engineer /geologist will log the borings and obtain relatively undisturbed, bulk samples of the materials DEN 97, 591, 785v2 9 -9 -11 GREENBERG TRAURIG, LLP • ATTORNEYS AT LAW • WWW.GTLAW.COM