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STATE OF COLORADO <br />DIVISION OF RECLAMATION, MINING AND SAFETY <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 866-3567 <br />FAX- (303) 832 -8106 <br />DATE: July 30, 2013 <br />TO: Peter Hayes, DRMS <br />FROM: TC Wait, DRMS <br />SUBJECT: Loloff Pit (M -1985 -112) <br />Review of Slope Stability Report (7/2013 by J &T Consulting) <br />COLORADO <br />D I V I S ION OF <br />RECLAMATION <br />MINING <br />SAFETY <br />John W. Hickenlooper <br />Governor <br />Mike King <br />Executive Director <br />Loretta E. Pineda <br />Director <br />Per your request, I have reviewed the slope stability report for the Loloff Pit prepared by J &T <br />Consulting, dated July 2013. This stability report was prepared as part of the Techincal Revision <br />No. 1 Request. The comments below should be considered as part of the adequacy response for <br />DRMS. <br />• The TR -1 request included changing the mining method to dewater the existing pond to <br />mine under dry conditions at a 3:1 slope. It is my understanding that the final land use <br />will remain wildlife habitat and include a pond. In general, the stability report was well - <br />written and adequately addressed the slope stability for the pit during the proposed <br />mining activity described in the TR. <br />• Basalm Avenue runs along the eastern edge of the site. There are a number of <br />underground utility lines associated with this road alignment. The analysis should be <br />sure to include effects on and from these utilities, including the possibility of water being <br />introduced from a leaking sewer or water line. <br />• The water level used in the analysis is approximately 12 ft below the ground surface on <br />the unaffected ground. This may not accurately reflect seasonally high conditions, or <br />conditions after the mine is flooded with water. <br />• The analysis sections are depicting "dry" conditions that would be found during mining <br />while the site is being de- watered. The stability should also be analyzed in "wet" <br />conditions that would represent post- mining conditions for longfterm stability. <br />• The report includes good recommendations for monitoring of slope stability. However, it <br />may be prudent to modify the inspections outlined in recommendation #1 and #4 on page <br />5 to a weekly basis for the duration of mining, then for 6 months post- mining. <br />Office of <br />Office of <br />Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines <br />