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III IIIIII III IIII III ~ STATt Of' ~.Ol.O 1t A fJU Hif lr.lnh U. LA61M f.rrv non nr <br />DEPARTMENT OF NATURAL RESOURCES <br />ggg ~ D. Monte Pasco c, E><ecut rve Director <br />1~11N Ell LA\ U N ECLAArI ~`I'lUN <br />423 Centennlai Building, 1373 Sherman Street <br />Denver, Colorado 80203 Tel. (303) 839-3567 <br />David C. Shelton <br />Director <br />June 30, 1981 <br />TO: Brian Munson <br />FROM: Jim Pendleton <br />SUBJECT: Review of t Geo hnical Aspects of the Rock Castles Company's <br />Request for c nical Revision at the Grassy Creek Coal Mine No. 1 <br />Pursuant to your request I have reviewed the Grassy Creek requested technical <br />revision. I submit the following comments for your consideration. <br />The stability analysis prepared by Hydro-Triad, Limited, appears to conform <br />with the prudent state-of-the-art. Material strength assumptions made in <br />the analysis are relatively conservative and the "SLOPE I" computer program <br />is one with which I am familiar. The stability analysis demonstrates that a <br />static slope safety factor of approximately 1.3 will be achieved in constructing <br />the road embankment, which will exceed the 1.25 requirement of the permanent <br />regulatory program. <br />Most important in assuring the construction of a stable road embankment will <br />be conformance with the engineered design. Keyed and benched construction is <br />difficult and requires careful field supervision and control. i suggest that <br />we stipulate, in accordance with Rule 4.03.1(1)(d), that the construction of <br />the haul road be"certified'bj the design engineer, Mr. Michael L. Brown, <br />Colorado Registered Professional Engineer No. 11017, of Hydro-Triad, Ltd. <br />This will require his periodic inspection and supervision during construction <br />of the ha`ul' road. Rny changes in allignment or grade necessitated by field <br />conditions should be documented in the "as-built" plans submitted as a portion <br />of his certification statement. He should certify that the road, as constructed, <br />conforms with the assumptions utilized in completing his stability analysis. <br />mab <br />cc: Fred Banta <br />