Laserfiche WebLink
• PROTECTION Of HYDROLOGIC BALANCE (2.05.6(3 u <br />EFCI will minimize infiltration of runoff to the coal refuse pile both <br />during construction and upon completion through use of the grading and <br />drainage control measures previously described. In addition, as <br />documented by coal refuse analysis results presented as Appendix 3, Coal <br />Refuse Chemistry, coal refuse contains no potentially acid, alkali or <br />toxic forming materials which could effect groundwater quality. <br />All surface runoff from the coal refuse pile and associated areas will be <br />captured and routed to Sedimentation Pond No. 4 by the collection ditches. <br />The water routed to Pond No. 4 will be retained to allow settlement of <br />suspended solids and will be discharged in compliance with applicable <br />effluent standards under NPDES Permit No. CO-0037109. <br />SUBSIDENCE CONTROL AND MONITORING (2.05.6(611 <br />• Rocky Mountain Geotechnical (RMG) completed a comprehensive subsidence <br />study addressing the refuse pile and other effected areas. The results <br />of this study are presented in Section 2.05.6(6), Subsidence, of the <br />permit application (Volume 6). <br />Potential subsidence effects and related mitigation measures for the <br />proposed refuse pile expansion will be essentially the same as previously <br />determined for the existing coal refuse pile. <br />The coal refuse pile, including the proposed expansion area, overlies the <br />main entries with limited overlap of immediately adjacent sub-entry areas. <br />To date, there is no evidence of any significant subsidence in either the <br />main or submain entry areas. <br />Upon completion of development and recovery of all panels served by the <br />existing main entries, EFCI will begin retreat mining, extracting pillars <br />• with the retreat. Based upon site experience, limited subsidence is <br />expected as pillar supports are removed. Maximum subsidence of up to 4.7 <br />feet would result in some settling of portions of or the entire refuse <br />12R Revised - February, 1990 <br />