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-30- <br />The total surface area to be disturbed during the permit term will be <br />approximately 80 acres. This disturbed area includes the following surface <br />facilities, as are shown on Figure 2.05.4-2: office and shop building; wash <br />plant; conveyors; breakers and dryers; 2 substations; guard house; truck <br />tunnel; truck scales; 2 fresh water ponds; 3 sediment ponds; mine dewatering <br />system; water treatment facilities; explosives bunker; 2 coal stockpiles; an <br />access road to the waste pile; an access road to G.E.C.'s pit; storage areas; <br />topsoil stockpiles and light use roads. <br />The applicant proposes to continue the construction of a waste disposal <br />structure originally approved as a portion of the interim program permit for <br />the Dorchester No. 1 Mine. The pile, as proposed, has a capacity of <br />approximately 2.1 million cubic yards of waste material. The waste pile <br />occupies approximately 30 acres in the northwest quarter of Section 30. Waste <br />is projected to be generated by the mine at the rate of approximately 280,000 <br />cubic yards per year (30% of total excavated volume). At this rate, the pile <br />represents sufficient storage capacity for approximately 7.5 years. The <br />operator is cautioned that future permits might require additional storage <br />capacity in order to accommodate the projected waste production. <br />The applicant has provided the Division with certified reports verifying <br />construction of the approved subdrain beneath the existing portion of the <br />waste pile. The pile is proposed to reach a maximum height of 75 feet. Waste <br />material is placed in maximum 2-foot thick horizontal lifts and compacted to <br />90% of the material's maximum dry density, as required by Rule 4.10.4(3). A <br />mechanical stability analysis of the proposed configuration of the waste pile <br />has been completed by Rocky Mountain Geotechnical, Inc., consultant to the <br />applicant. This analysis, performed in accordance with the prudent <br />state-of-the-art of slope stability analysis, determined that the pile <br />achieves a static slope safety factor in excess of the 1.5 value, required by <br />Rule 4.10.4(2). This analysis is included within the permit application as <br />Attachment D. <br />The applicant has undermined portions of the waste pile area during main and <br />submain underground working development. Further, the applicant proposes to <br />retreat mine beneath this same area. A discussion and stipulation regarding <br />undermining of the coal processing waste pile area are included within the <br />"Subsidence" section of this finding document. <br />With the imposition of the stipulation within the Subsidence section of this <br />findings document, the proposed coal processing waste disposal structure is <br />found to be in compliance with the requirements of Rule 4.10. <br />XV. Roads - Rules 2.05.3(3), 4.03 <br />The applicant presents a discussion of mine roads in Section 2.05.3 of the <br />Second Adequacy Response. No haul roads have been proposed and only one <br />access road was proposed. <br />