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The pile has been designed with maximum facial outslopes of 4:1 (horizontal to <br />vertical) and a maximum height of 55'. A stability analysis, performed by - <br />CTL/Thompson, Inc., ascertained a minimum static slope safety factor of 3.6, " <br />assuming an angle of internal friction of 42° and the cohesion of 0. <br />Confirming laboratory testing, performed by the applicant, determined an angle <br />of internal friction of 42° and a cohesion of 1,500 lbs. per square foot. <br />Therefore, the safety factor determination presented within the preliminary <br />stability analysis has proven to be conservative in nature and well exceeds <br />the required 1.5 minimum acceptable static slope safety factor required by the <br />regulations. <br />The foundational area of the coal processing waste pile has been prepared by <br />removal of topsoil and unacceptable subsoils and the installation of a gravel <br />and the subdrain and peripheral toe drain. These drains will preclude the <br />invasion of ground water into the waste material. Waste material will be <br />pi aced in horizontal lifts of 24" in thickness, compacted to achieve 90'b of <br />the waste material's maximum dry density, as determined utilizing AASHTO <br />testing specification T-99. Compliance with the certified inspection <br />requirements of Rule 4.10.2 will assure compliance with the approved plans and <br />construction standards. <br />The operator has requested a variance from the 4' thick non-toxic cover <br />requirements of Rule 4.10.4(4), normally required for all coal processing <br />waste structures. The resolution of this aspect to the coal processing waste <br />pile's design is accomplished by stipulation within the vegetation portion of <br />this findings document, Section XI. <br />With the imposition of the stipulation referenced within the vegetation <br />section of these findings documents, Empire Energy Corporation's proposed coal <br />processing waste disposal plan is found to be in compliance. <br />XIX. Water Quality Standards-and Effluent Limitations - Rule 4.05.2 <br />All surface drainage from the Empire Mine Complex passes through sedimentation <br />ponds or a series of sedimentation ponds prior to leaving the permit area <br />except for those exemptions noted below. All sedimentation ponds are <br />permitted through the Water Quality Control Division of the Colorado <br />Department of Health to discharge to State waters under the NPDES Permit No. <br />CO-0034142. fie waste water treatment facility is also permitted under this <br />number. <br />Several areas at the Empire Energy Mine Complex have been granted small area <br />exemptions which excludes the need for drainage to pass through a <br />sedimentation pond. These exemptions have been granted based on`the areas <br />being small; that there is no mixture of surface drainage with discharge from <br />the underground mine workings, and that sedimentation ponds or treatment <br />facilities are not necessary for the drainage to meet the effluent limitations <br />of 4.05.2 and applicable State, and Federal water quality requirements for <br />receiving waters. The small area exemptions are .listed below. <br />Rock Dust Tanks - Tanks are fully enclosed. Tank site disturbance areas are <br />small (less than 1 acre), surface is graveled and they are located away from <br />any receiving streams. <br />-60- <br />