Laserfiche WebLink
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: September 11, 2013 <br />TO: Peter Hayes, DBMS <br />FROM: TC Wait, DRMS <br />SUBJECT: Loloff Pit (M- 1985 -112) <br />Response to Slope Stability Report comments, <br />Slope Stability Report Reivew (revised 8/2013 by J &T Consulting) <br />COLORADO <br />D I V IS I ON 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 responses to the adequacy review for TR -01 slope stability <br />report and revised slope stability report for the Loloff Pit prepared by J &T Consulting. The <br />responses were addressing comments in the initial adequacy review for the slope stability report <br />(memo dated 7/30/13). <br />• The revised report (8/2013) adequately addresses the majority of my initial slope stability <br />comments. Recommendations made in this report should be followed. <br />• I understand the difficulties in modeling possible effects from underground utility <br />contributions along the eastern edge of the site (Basalm Avenue). However, the proposed <br />mining activity may impact the utility lines not only from a slope failure, but from <br />differential settlement that can compromise the utility line and create a leak, which can <br />then contribute to a potential slope failure. <br />The calculated FS for this eastern alignment are 1.49 (static) and 1.1 1 (pseudo- static) <br />using a groundwater elevation of 3 feet below ground surface. <br />If utility structure agreements are not obtained, I would suggest running an additional <br />stability analysis for this eastern alignment using a groundwater elevation equal to the <br />ground surface (0 feet below ground surface) to ensure that there is a reasonable FS for a <br />saturated ground condition (extreme worst -case stability analysis). <br />Office of Office of <br />Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines <br />