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OF ~~Cp <br />~~~~~ <br />r~~, `~3` <br />yN <br />•~ ~ <br />~a~e' <br />Richard D. Lamm <br />Governor <br />DATE: <br />T0: <br />FROM: <br />RE: <br />•- <br />DEPARTMENT OF NATURAL RESOURCES <br />Davitl M Getcnes. Eaecuhve Duector <br />MINED LAND RECLAMATION DI\ <br />DAVID C. SHELTO N, Director <br />March 26, 1984 <br />~iddle <br />P. C. Saletta ~~ <br />USS - Somerset Coal Mine <br />Stipulation No. 5 - Slope Stability <br />As per your request, I reviewed U. S. Steel's Stability Analysis of Reclaimed <br />Contours, in response to Stipulation No. 5. The report includes standard <br />laboratory analyses to determine both rock and soil strength characteristics. <br />The results from these analyses are reasonable values for soil and rock <br />materials in this particular geologic environment. <br />The method of slope stability analysis is a computer search technique of <br />circular failure surfaces using the Simplified Bishop Method. This method of <br />analysis is a standard engineering method and is similar to the OSM Slope II <br />Program for slope stability analysis. <br />The results documented by the U. S. Steel report indicate that slopes with the <br />proposed final contours will meet or exceed the required static factor of <br />safety of 1.3. <br />As verification, I calculated a safety factor for an apparent worst case slope <br />as depicted on Exhibit 6. My method utilized a stability number chart for toe <br />circles: <br />S.F. = Ns C = 11.2 (216) = 1.32 >1.3 <br />~rH lOl.S (18) <br />Where: Ns 11.2 = stability number <br />C = 216 psf = cohesion <br />H = 18 feet = height of embankment <br />~ = 101.5 pcf unit weight of soil <br />The additional analyses submitted are adequate and meet or exceed the required <br />static factor of safety of 1.3. The operator has adequately responded and is <br />in compliance with Stipulation No. 5. <br />If you have any questions or comments, please contact me. <br />/cd <br />Doc. 0348E <br />423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (30•x) 866-3567 <br />i III Iiiiillllllli III <br />