Laserfiche WebLink
Mr. Ken Lambrecht <br />January 17, 2006 <br />Page 3 <br />The parameters for weathered bedrock are much more conservative than those typically <br />encountered in the area and, it is our opinion, that they are not representative of conditions at the <br />site. Additionally, the DMG dictates that the mine highwall must be modeled as vertical surface. <br />For this special case, this geometry was incorporated into our model. <br />CONCLUSIONS <br />Table 3 below summarizes the results of our analysis. Typical required factors of safety for <br />temporary mine slopes and reservoir embankments are provided for comparison. Output <br />graphics for each of the analyses aze attached. <br />Table 3: Deep Seated Failure Analysis Results <br /> Typical <br />Model Setback Factor of Required <br /> Distance (Peet) Safety Factors of <br /> Sa e <br />Temporary Mine <br />''/::1Highwall-Shallow 10 1.33 1.2 <br />Section <br />Temporary Mine %::1 <br />HighwallIntermediate 30 1.26 1.2 <br />Section <br />Temporary Mine %::1 20 1.20 1 <br />2 <br />Hi hwall Dee Section . <br />Temporary Mine '/::1 <br />Highwall Deep Section 30 1.22 1.2 <br />with weathered bedrock <br />Long Term Compacted 20 1.81 1 <br />5 <br />Cla Slo e Liner . <br />Long Term Compacted <br />Clay Slope Liner Rapid 20 1.21 1.2 <br />Drawdown <br />Long Term 3:1 Mined 16 2.21 1.5 <br />Slo e <br />DMG analysis 37 L00 1.0 I <br />Typically each of the owner's of the existing structures possibly effected (in this case the utilities <br />in the right-of--way) can be approached to see if a less conservative analysis can be used. <br />However, if a non-site specific analysis is pursued, the set back distance from the slurry wall to <br />the mine highwall will need to be 37 feet or greater, based on the DMG pazameters. If a site <br />specific analysis can be used, a highwall setback of 20 feet from the top of highwall to the slurry <br />wall should be suitable for both the temporary mine slope and the final lined reservoir slope, <br />unless weathered bedrock is encountered in the azeas of deeper bedrock. If this weathered layer <br />is encountered, the setback should be increased to 30 feet. If the highwall is mined at a 3:1 <br />(horizontal to vertical) final slope the set back only needs to 16 feet. <br />