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STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1313 ShemEan St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 866-3567 <br />FAX: (303) 832-8106 <br />I nterofFice Memo <br />To: Dan Matthews <br />From: Kent Gorhar~~ ~~~~ <br />Date: 10/14/2005 <br />Re: TR-19, Munger Canyon, #C-81-020 <br />OLORADO <br />( V I S I O N O F <br />~1NERALS <br />(GEOLOGY( <br />0.ECLANATION•MINING <br />EAf ETY•SCIENCE <br />Bill Owens <br />Governor <br />Russell George <br />Executive Director <br />Ronald W. Gttatsy <br />Division Director <br />Natural Resource Tnalee <br />I have completed my review of TR-19 for the Munger Canyon Mine, #C-81-020. The <br />revision proposes modifications to the spillway system at the coal refuse pond. <br />These modifications are necessary to prevent a repeat of the situation encountered <br />during a late July 2005 rainstorm event. Consequences as a result of the storm <br />event are documented in a DMG inspection report dated August 3, 2005. <br />My review included the revised materials under TR-19 including revised permit page <br />2-13, revised page M(vii)-5, revised Figure 2.2-6, and revised Figure 2.2-7. I also <br />reviewed the currently approved version of the same and the hydrology calculations <br />in Appendix M. <br />The new design for the emergency spillway meets the requirements of Rule <br />4.05.9(2)(a). However, I did not find any information in the revised materials or in the <br />currently approved permit that demonstrate compliance with Rule 4.05.9(2)(b). This <br />Rule requires no passage of the 10-year storm through the emergency spillway. <br />Information to determine compliance with this Rule does not appear to be available. <br />Please have the applicant submit information that ident~es the peak stage of the 10- <br />yearstorm in the refuse pond. This elevation would be the minimum elevation for the <br />invert of the proposed 21-inch emergency spillway culvert. Post construction <br />cert~cation would then verify that the culvert was installed as per the approved <br />design. <br />If you have questions, please call me. <br />CC: Sandy Brown <br />• Page 1 <br />Office of t7ffice of Colorado <br />Mined Land Reclamation Active and Inactive Mines Geological Survey <br />