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Fourth Adequacy Response 112(d)-1 Application, Amended CN-01 <br />Wildcat Mining Corporation May Day Idaho Mine Complex <br />Attachment B <br />Chief Drainage Adequacy Response <br />Fourth Review Adequacy Response <br />May 27, 2011 Cazier Memorandum <br />Permit No.1981-185/CN-O1 <br />Attachment E-6, Chief Drainage Channel Reclamation Work Plan <br />Page 3 Communication- Reporting: <br />1. The third solid bullet indicates the as-built drawings will be submitted 30 days after the <br />channel reclamation. The Division requires the as-built drawings be submitted to the <br />Division within 30 days of channel reclamation construction completion. <br />Comment: The Company will submit as-built drawings to the Division within 30 <br />days of channel reclamation construction completion. <br />Page 3 Work Plan Channel Design: <br />2. Please clarify the term "pre-channel slope". If the applicant is using Procedures for <br />Determining Peak Flows in Colorado (SCS, 1984), the slope in Figure S-IA is average <br />watershed slope, not pre-channel slope. DRMS engineering staff is reviewing <br />Attachment T-4 Table SWMP-A and the calculations presented therein. Comments on the <br />hydrologic and hydraulic analyses will be provided at a later date. <br />Comment: Term has been clarified. See Attachment K (Chief Little Deadwood <br />Gulch Channel Corrective Action Plan) to CN-01, Response to Third Adequacy. <br />3. With respect to the channel capacity discussion, it is unclear as to whether 0.4 feet of <br />freeboard applies to the 210 cfs capacity or the 87 cfs design now. However, a quick <br />check using Manning's equation and the hydraulic input parameters provided <br />demonstrates that there is less than 0.4 feet of freeboard for the 87 cfs design flow - 0.38 <br />ft. Regardless, DBMS requires a minimum of one foot of freeboard for supercritical flow <br />channels, with half the velocity head preferred if it is greater than the one foot. In this <br />case, based on the hydraulic input provided, half the velocity head is slightly less than <br />one foot. Furthermore, based on the provided hydraulic input, the channel would need to <br />be 2.4 feet deep to convey the 210 cfs with no freeboard, not the 2-foot depth stated. <br />Please correct the calculations and statements, and note Comments # 9 and #10 regarding <br />the design presented in Figure 1. <br />Comment: Free board has been increased to one foot or higher. See Attachment K <br />(Chief Little Deadwood Gulch Channel Corrective Action Plan) to CN-01, Response <br />to Third Adequacy. <br />Page 3 Site Preparation: <br />4. This bullet is unclear, please restate and clarify what is to be removed, and from where. <br />6/6/2011 <br />12