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-30- <br />Stipulation No. 6 <br />IN ORDER TO SIMPLIFY THE COMPARISON OF PRE-MINING, MINING AND POST-MINING <br />TRANSECT PROFILE SURVEY DATA, THE DIVISION DEEMS IT APPROPRIATE TO <br />REQUIRE PUEBLO COAL, INC. TO PERFORM THE PROPOSED TOPOGRAPHIC PROFILE <br />SURVEYS ALONG THOSE TRANSECTS USED TO PREPARE THE CROSS-SECTIONS DEPICTED <br />WITHIN APPENDIX 4-2a WITHIN THE AMENDED PERMIT APPLICATION DOCUMENTS. <br />Comments regarding the applicant's proposed handling of acid- or toxic-forming <br />materials, both overburden and coal processing waste, may be found within the <br />statement of probable hydrologic consequences and Section XVII of this <br />findings document. <br />The reclamation plan presented within the amended permit application coincides <br />with the operations plan timetable as closely as possible, insofar as the <br />sequence of events in the normal surface mining operation allows. A specific <br />discussion of the complicated scheduling aspects of the Carbon Junction <br />surface mine is presented in detail within Section 2.05.3(2), "Operation <br />Description", of the amended permit document. An operations timetable is <br />presented briefly in tabular form on Table 5-1 of the permit application. The <br />majority of the initial 3 million cubic yards of spoil material removed to <br />establish the steady state pit at the Carbon Junction Mine will be placed in a <br />permanent excess spoil fill. Following completion of the excess spoil fill, <br />backfilling and regrading of the spoil will become contemporaneous with the <br />extraction of coal. Redistribution of subsoil and topsoil will occur in <br />logical sequence with mining and spoil regrading. Final reclamation is <br />scheduled to be completed in the fall of the fifth year following the start of <br />mining. <br />The applicant proposes to dispose of excess spoil material in a permanent <br />overburden spoil pile of 2.837 million cubic yards. The construction of this <br />fill will allow the creation of an approximately 3 million cubic yard <br />steady-state pit, necessary to accomplish the haulback mining method. This <br />projected permanent excess spoil fill will cover approximately 27 acres. The <br />design of the fill basically involves 3:1 (horizontal to vertical) side slopes <br />and a top surface grade of approximately 1% toward the south. The north end <br />of the fill ties into existing topography such that no pooling of water or <br />subsequent saturation of the fill should occur. The proposed design to the <br />excess spoil pile includes the construction of an underdrain, detailed within <br />supplemental submittals made by the applicant in response to Division adequacy <br />comments. Atypical underdrain design section is depicted on Figure A-2, <br />included within the May 4, 1983 supplemental submittal made by the applicant. <br />Spoil material will be placed in lifts not to exceed 4 feet within the excess <br />spoil pile and then compacted appropriately, in order to assure slope <br />stability. A geotechnical investigation and mathematical stability analysis <br />of the proposed excess spoil pile was performed by Kenneth C. Ko and <br />Associates, Inc., consultants to the applicant. This stability analysis, <br />performed in accordance with a prudent state-of-the-art geotechnical slope <br />stability evaluation, projects that the proposed pile configuration should <br />attain a static slope safety factor of no less than 1.8. This geotechnical <br />investigation and mathematical stability analysis can be found in Appendix 5-6 <br />of the amended permit application. <br />