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-54- <br />Utilizing the results of Geo-F~ydro, Consultants, Inc .'s analyses, Merrick 8 <br />Company, Inc., design consultant to CWI, completed a Phase II amended design <br />for the drainage facilities at the existing surface facility area of the <br />Orchard Yalley mine. CWI has also completed a detailed stability analysis and <br />redesign of the proposed final reclaimed configuration for the surface <br />facilities at the mine. In order to ensure stability and control erosion on <br />final graded slopes, the Division proposes to approve a post-mining topography <br />of cut and fill terraces at the main mine. These terraces are compatible with <br />the post~nining land use of grazing and meet all the requirements of 4.14.2(2) <br />with the exception of 4.14.2 (2 )(a ). Terraces will all exceed twenty feet in <br />width and range in width according to the reclaimed configuration map series <br />6A-5. <br />In August, 1986, CWI submitted a permit revision application to construct a <br />west portal facility in the East Roatcap Creek valley at the Orchard Yalley <br />Mine. This application proposed the construction of a new portal facility and <br />haul road, because the existing portals at the Orchard Valley Mine had been <br />rendered unuseable by an underground coal mine fire. The applicant proposed <br />to upgrade an existing public access road to serve as a coal haul road to the <br />proposed west portal bench, which will be constructed by a balanced cut and <br />fill method. fie portal bench fill includes a 130 foot maximum height <br />terraced earthen fill constructed across East Roatcap Creek. Maximum <br />lnterterrace facial slopes shall not exceed a 2.5h:l.Ov (horizontal to <br />vertical) slope gradient. A 48 inch concrete culvert was installed beneath <br />the cross valley fill to accommodate the 100 year flow of the East Roatcap <br />Creek. <br />The permit revision application included geotechnical specifications <br />documented in the OVWM Appendix, Volume 6, prepared by Golder and Associates, <br />consultants to CWI. This appendix presents the results of geotechnical <br />investigations, stability analyses and detailed engineering designs for the <br />west portal bench cut and fill and the accompanying upgraded haul road. The <br />stability analyses are based upon projected slope configurations and material <br />mechanical properties obtained from material sampling and laboratory analyses. <br />Stability analyses were completed for both the operational <br />configurations of the west portal facility area. Analyses <br />following static slope safety factors for the west portal <br />embankment. <br />0 erational Confi uration <br />or u ope <br />Rotational Fill Slope Failure <br />Bedrock/Colluvium Rotational Failure <br />Portal Embankment Slope <br />Rotational Fill Slope Failure <br />Bedrock/Colluvium Rotational Failure <br />Fill/Colluvium Contact <br />Backfilled Confi uration <br />Ro a tona ope ailur <br />Fill/Colluvium Contact <br />and reclaimed <br />projected the <br />cut slope and fill <br />1.52 <br />1.99 <br />2.04 <br />1.55 <br />2.17 <br />1.94 <br />2.73 <br />