Laserfiche WebLink
8/22/2014 State.co.us Executive Branch Mail - Fwd: Bowie No. 2 Mine C1996083 Technical Recision No. 89 Adequacy Response #1 <br />P 303.566.3567 x 5111 I F303.832.8106 <br />1313 Sherman Street, Doom 215, Denver, CO 50203 <br />susan.burgmaier@state.co.us I http: / /mining.state.co.us <br />Hi Tamme - <br />We are looking for a conventional slope stability analysis, showing that the resulting permanent cut slope will <br />have a static safety factor of 1.3. Our main area of concern is the portion of the ditch on the eastern end, <br />near the proposed borrow areas. The rules supporting the request are: <br />2.05.314)(a) and (d) <br />Stream channel diversions and other diversions... shall be designed to comply with requirements of 4.05.3 and <br />4.05.4 <br />4.05.3 Diversions and Conveyance of Overland Flow... <br />(3) Permanent diversions shall be constructed with gently sloping banks that are stabilized by vegetation. <br />Asphalt, concrete, or other similar linings shall be used only when approved by the Division to prevent seepage <br />or to provide stability. <br />(5) When constructed, diversions shall be designed and located in a manner that minimizes the potential for <br />landslides. <br />4.14.2 General Grading Requirements <br />(1) The final graded slopes shall approximate pre - mining slopes, or any lesser slopes approved by the <br />Division... <br />(1)(b) Backfill and grade to the most moderate slope possible, which does not exceed either the angle of <br />repose or such lesser slope as is necessary to achieve a minimum static safety factor of 1.3. <br />Given the fact that the configuration will be permanent and the ditches need to remain stable for the <br />foreseeable future, the Division believes that requiring a minimum static safety factor of 1.3 [per 4.14.2(1) <br />(b)] for all of the cut slopes above the diversion ditches is not unreasonable. <br />(Thanks, Marcia, for compiling these references.) <br />Susan L. Burgmaier <br />Environmental Protection Spotecialist III <br />Coat Regutatory Program <br />https: / /mai l.g oog le.conVmai 1 /u /0 / ?ui =2 &i Ire29129fcb5 &view= pt &search =i nbox&th= 147fa7df6e992582 &si ml= 147fa7df6e992582 2/4 <br />