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\- . ti • • ll I III III III IIII Ills 999 DIVISION OF MINERALS AND GEOLOGY Department of Natural Resources 1313 Sherman St., Room 215 Denver, Colorado 80203 Phone: 13031 866-3567 FA%:13031812-8106 STATE OF COLORADO I~~ DEPARTMENT OF NATURAL RESOURCES June 14, 1995 Hoy Romer C;overnor lames 5 LochhcaA Etecwive Director Mr. Jim Stover Michael B. Lung J.E. Stover and Associates Uivi lion Director 2768 Compass Drive, Suite 101 Grand Junction, Colorado 81506 RE: Somerset Mining Company, File ~ C-81-022, Technical Revision 26 Dear Mr. Stover: The Division has completed its adequacy review of technical revision 26 (TR-26). In general the submittal addresses the problems of freeboard associated with the primary- and emergency spillways identified in the field, however, there are some associated questions raised about the hydrologic design of the pond upon implementation of these changes. These are listed below. 1. The Division was unable to verify the maximum water level for the 25-year, 24-hour precipitation event from the hydrologic designs in the permit. Please provide this information and clarify that the maximum water level on the cross-section represents the 25-year, 24-hour event. The hydrologic design beginning on page B37 in Appendix B, Volume 7 also does not clearly demonstrate what the 10- year, 24-hour event will be. Please clarify what the 10- year, 24-hour event and sediment elevation should be and show this elevation on drawing C8-1166. This design should also demonstrate that a six inch pipe for both the primary and emergency is adequate, and since the pond size is changing, the entire hydrologic design should be amended to reflect this change. 3. Upon approval of this revision and field modification to the pond, the pond will need to be recertified. Perhaps some of the requested information is in the permit application, however, we were unable to locate it. Once this information is received and accepted the revision will be approved. Page 1