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11. There will be some long-term settlement of both disposal areas. We recommend overbuild of <br />approximately 5 percent in the central portion of both fill areas in order to maintain long-term drainage. The <br />surface of the fill should be designed with a slope of 5 percent away from the head of the fill. The fills should <br />drain to ditches on both sides of the fill. <br />Given that these drainage features encompass the entire temporary clay stockpile, topsoil pile, and light -use road, <br />and that these disturbances represent only a small portion of the total excess overburden stockpile area, they should <br />provide effective drainage and sediment control for the proposed temporary activities. A temporary fueling station, <br />consisting of a fuel tank and lined secondary containment, will also be established at the stockpile location. The <br />stockpiled clay will be recovered and placed as cover material on the western slope of the Refuse Pile as soon as <br />ongoing refuse placement and grading bring this area to the final design elevation and grade. The light -use road <br />will be narrowed and ripped, stockpiled topsoil will be replaced on the associated disturbance areas, and all <br />disturbed areas will be reseeded with the permanent rangeland seed mix. <br />4) Subsurface and Surface Drainage - Small drainage ditches will be constructed downslope of the temporary <br />stockpiles to minimize water running over and down finished slopes of the CRDA. Also, it was recommended in <br />Exhibit 26A -I that temporary drainage ditches be established along the eastern edge of the benches as they are <br />constructed, to prevent excessive surface runoff fi-0111 flowing over the finished/compacted slope of the CRD.A <br />The specific recommendations for these temporary drainages are presented in Exhibit 26A-1. <br />Coal Refuse Disposal Area Expansion (MR07-226, MR15-290, TR09-67, TRIO -72, and TR13-83) <br />With the existing CRDA nearing its design capacity, TC completed an evaluation of required refuse disposal <br />requirements through the end of the Foidel Creek mine life. Included in this evaluation was an assessment of the <br />potential refuse disposal requirements for the nearby Sage Creek Project, in the event it proceeds to development <br />and full-scale production. The evaluation of potential future refuse disposal requirements indicated that a <br />maximum of approximately 20.0 MM cubic yards of additional capacity would be required to address reasonably <br />foreseeable future needs. Based on the calculated refuse disposal capacity requirement, TC contracted with <br />Northwest Colorado Consultants (NWCC) to complete site geotechnical investigations and detailed design and <br />phasing plans for phased construction of a 20.0 MM cubic yard CRDA Expansion, along with all associated <br />structures and facilities. With deferral of the Sage Creek Project, TC may utilize part of the allocated CRDA <br />capacity to support production from the Wolf Creek Reserve. If additional refuse capacity is needed in the future to <br />compensate for reallocation of this incremental capacity, TC will review options for either an additional expansion <br />of the existing CRDA or a separate CRDA location, and prepare and submit the necessary design and permitting <br />documents for CDRMS review and approval. The proposed CRDA Expansion is located immediately adjacent and <br />to the east of the existing CRDA, and the existing CRDA on the west, natural ridgelines to the east and south, and <br />the engineered, benched refuse fill toe on the north, effective bound and provide containment for refuse fills. <br />Designs for the associated facilities include required access, drainage control structures, and soil and cover material <br />handling plans and stockpiles. <br />Site geotechnical investigations are required to provide foundation and soils information for design, permitting, and <br />construction of the Coal Refuse Disposal Area Expansion. The area proposed for the Refuse Pile Expansion is an <br />area of reclaimed mine spoils immediately adjacent and to the east of the existing CRDA, as shown on Maps 24, <br />Mine Facilities and Freshwater Systems, and EX26C-MI, Surface Facilities — Refuse Pile Expansion. Site <br />geotechnical investigations for the CRDA Expansion involved completion of five, 4 -inch hollow -stem auger <br />sample holes to depths of 20-40 feet; excavation of seven shallow (ten to fifteen feet in depth) backhoe test pits. <br />and collection, examination, and testing of soil samples. There will be a total of no more than twelve auger holes <br />and test pits. <br />No new roads were built. sample locations were accessed overland using rubber -tired equipment, and access was <br />limited to periods when the ground was dry or frozen in order to minimize surface disturbance. In order to <br />minimize surface disturbance, soil removal was limited to the immediate area of each auger -hole or test pit, with <br />soil material being windrowed to the side of the disturbance area, and re -spread immediately following completion <br />of drilling/excavation/sampling and backfilling. Site runoff from the limited disturbance areas was addressed <br />through the use of alternative sediment controls consisting of straw wattles, placed and staked immediately <br />PRI 5-1 1 2.05-97.2 02/01/16 <br />