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October 17, 2013 <br />To: Marcia Talvitie <br />From: Susan Burgmaier C-0 <br />Re: Carbon Junction Mine (Permit No. C- 1992 -080) <br />Technical Revision No. 17 (TR -17) <br />Adequacy Response Review <br />Per your request, I have reviewed the packet provided by Goff Engineering and Surveying, Inc. (Goff) in <br />response to my adequacy concerns with the Technical Revision (TR -17) application for the Carbon <br />Junction Mine. I have the following comments and questions for the operator: <br />1. This item is resolved, but the recently located appendices 5 -9 and 5 -10 should be re- incorporated <br />into the permit application package. Also, the information provided by Goff conflicts with the <br />currently approved permit application pages 10c through 5 -17 of Section 2.05.3. Those pages <br />provide designs for six segments of the permanent diversion that do not coincide with the maps <br />provided by Goff, and also still include a reference to an additional 500' of rip rapped channel that <br />Goff is proposing will be vegetated instead of rip rap lined. This section of the permit should be <br />updated to make clear that pages 10c -17 are proposed design information, and reference an <br />appendix that will contain the as -built information provided by Goff. <br />2. This item is resolved. Goff did not provide information to clearly demonstrate that the existing <br />diversion ditch would safely convey the design flow with the required freeboard, but the Division <br />was able to ascertain that the water surface elevation and freeboard would be at or below the <br />elevation of the rip rap lining within all segments of the channel. <br />3. This item is resolved. Goff elected to retain the original runoff calculations in the permit application <br />package. <br />4. Goff revised the design based on a 10 yr — 24 hr event, as suggested by the Division. The runoff <br />value used (2.19 "), however, is inconsistent with the value in the currently approved permit <br />application (2.25 ") and that shown on the NOAA distribution maps located at <br />http: / /hdsc.nws.noaa.gov /hdsc /pfds /pfds map cont.html ?bkmrl< =co (also 2.25" for latitude <br />37.24722 /longitude - 107.8556). Please revise the calculations for the Upper Carbon Junction <br />discharge using a rainfall depth of 2.25 ". When the designs have been revised using the appropriate <br />rainfall amount, Goff should determine whether the predicted velocities will be erosive and provide <br />designs for channel lining if necessary. <br />5. Goff did not submit a proposed revision to the sixth page of Appendix 5 -2. It appears that this item <br />has not been addressed. <br />6. This item is resolved, the maps, cross sections, and plans have been certified. <br />