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4.0 RPE East Refuse Pile Permit Design <br />The RPE East refuse pile design is presented on the permit drawings provided in Appendix D. The <br />layout of the refuse pile is based on geotechnical analysis and design provided in Section 2. Key <br />components of the refuse pile design are presented below. RPE East refuse storage capacity is shown <br />in Appendix G. <br />4.1 Stripping <br />Vegetation will be removed and vegetative soil will be stripped from the refuse pile footprint prior to <br />preparing the drainage and site for placement of coal refuse materials. Vegetation that can be <br />chipped in place will be mixed with the vegetative soil to enhance the organic content.. Vegetative <br />soil will be placed in designated stockpiles until needed for contemporaneous reclamation as the face <br />of the refuse pile reaches design grade (Rule 4.13). <br />4.2 Buttress <br />A rock buttress will be constructed at the toe of the RPE East refuse pile to increase stability of the <br />refuse pile as required by Rule 4.09.1(10). Prior to buttress construction, the buttress area will be <br />stripped of soils and colluvium down to bedrock. A keyway cut will be placed at the toe of the <br />buttress to enhance stability. The buttress will consist of rock with colluvium on the upstream face <br />only, excavated from the initial refuse pile development area. The buttress will have a 1.511:1 V <br />slopes on its north face (away from the refuse pile) and a 1 H:1 V slope on the south face where refuse <br />will be placed. <br />Colluvium that is removed from the buttress foundation area that is not used in buttress construction, <br />in haul roads, or used for other construction needs may be placed in horizontal windrows orientated <br />generally perpendicular to the face of the refuse pile within the refuse material to minimize <br />interference with refuse pile drainage and to minimize potential for negative impact to geotechnical <br />stability. Where beneficial to the stability of the refuse pile, colluvium may be mixed with wet <br />refuse materials to absorb moisture. The extent of such areas will be kept to a minimum to avoid <br />developing low - permeability zones within the refuse pile. <br />Revised July 21, 2011 I" l� 5 <br />261 0 <br />P. \Mpls \06 CO \26\06261003 RPE E Permit Mod Support \WorkFiles \Permit Apphcation \Text \Exhibit 82 RPEE design 2011 -07 -21 TR 127 doc 17 <br />