2009-12-03_REVISION - M1977036 - Laserfiche WebLink

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Memo to Jared Ebert 2 November 6, 2009 Slope Stability Review File No. M- 1977 -036 Poudre River Trail Section and Fence The applicant's analysis was duplicated for verification; no potential failure surfaces with lower safety factors than the applicant's identified critical slip circle were located. The safety factor produced by Galena is slightly higher than that produced by Slope -W 2007; this is due to slight programming differences in the software packages and is not significant. Therefore, the accuracy of the applicant's analysis is confirmed (see attached). Gas Line Section The applicant's analysis was duplicated for verification; no potential failure surfaces with lower safety factors than the applicant's identified critical slip circle were located. The safety factor produced by Galena is higher than that produced by Slope -W 2007; this is due to slight programming differences in the software packages and is not significant. Therefore, the accuracy of the applicant's analysis is confirmed (see attached). The analyzed gas pipeline is located southwest of the proposed pit. The DRMS is concerned not only with the potential for landslide failure to damage the structure, but also with the potential for the pipeline to be damaged by flexure caused by slight earth movements caused by lateral stress relief through the excavation adjacent to the pipeline. DRMS frequently requires strain gauges be installed on pipelines adjacent to pits to monitor for flexure. However, in the case of the proposed Greeley 35 Avenue Mine, the applicant provided the DRMS with a notarized structure agreement between the applicant and the structure owner, DCP Midstream (successor in interest to Bellwether Exploration Co.); therefore strain gauges will not be necessary. Conclusion The DRMS agrees with the proposed setbacks from the mining highwall at the Greeley 35 Avenue— Brown Property Mine. enclosures