Laserfiche WebLink
XVII. BackfiZling and Grading (2.05.3(6)(b), 2.05.3(9), 2.05.4(2)(a), <br />2.05.4(2)(c), 4.09, 4.13, 4.Z4) <br />The applicant proposes to backfill the site with roof fall material and material <br />that has accumulated on the bench during past operations. All coal fines and <br />remaining coal material will be backstowed in abandoned workings. A portion <br />of the access road will be left per the landowner's request. <br />The applicant proposes to backfill the disturbed portal bench areas to a config- <br />uration variant from the assumed pre-mining configuration. The proposed post- <br />mining topography includes the retention of several portions of the portal high- <br />wa11 cuts at gradients of 1.5:1 (horizontal to vertical). Pre-mining mapping <br />does not exist for the disturbed portal bench areas. However, the character <br />of adjoining undisturbed slopes suggests that the pre-mining undisturbed natural <br />slopes comprised "steep slope mining areas", with slopes exceeding 200. <br />The proposed backfill and grading configuration depicted on Map C-7 can be <br />approved. In a steep slope mining situation (200 slope or greater), however, <br />the applicant should backfill the site at a slope which will achieve the required <br />minimum 1.3 static slope safety factor. In such an instance, slope or highwall <br />areas which exceed that critical slope gradient must be shown to be erosionally <br />and structurally stable. Information supplied by the applicant is not adequate <br />to demonstrate compliance with this standard. Because the King Coal mine exists <br />in its proposed maximum degree of slope disturbance, it is deemed appropriate <br />to require compliance with the backfilling and grading requirements of the <br />permanent regulatory program through the imposition of the following permit <br />stipulation: <br />2. NATIONAL KING COAL DfUST PREPARE A MASS BALANCE DEMONSTRATION TO <br />CLARIFY THE INDICATED SOURCES OF MATERIAL TO BE USED TO BACKFILL <br />AND REGRRDE THE SURFACE FRCILI TIES AREA. SUCH DEMONSTRATION SHALL <br />INCLUDE AN AMENDED DESCRIPTION OF MATERIAL SOURCES AND TECHNIQUES <br />OF MATERIAL PLACEMENT TO BE UTILIZED. VOLUME CALCULATIONS SHALL BE <br />COMPLETED DETAILING THE VOLUME OF FILL REQUIRED AND THE VOLUME OF <br />MATERIAL TO BE OBTAINED FROM EACH SOURCE, SUCH AS SALVAGE OF EXISTING <br />BENCHES, DEPOSITION OF UNDERGROUND DEVELOPMENT WASTE AND ROOF FALL, <br />DEPOSITION OF SEDIMENT FROM SEDIMENT PONDS AND THE DISPQSAL OF DE- <br />MOLISHED SURFACE FACILITY DEBRIS. THIS MASS BALANCE EXPLANATION <br />SHALL BE SUBMITTED TO THE DIVISION WITHIN 60 DAYS FOLLOWING THE <br />ISSUANCE OF THE APPROVED PERMIT. <br />FURTHER, NATIONAL KING COAL MUST PREPARE AN APPROPRIATE GEOTECHNICRL <br />RND STABILITY ANALYSIS OF THE PROPOSED BACKFILLED CONFIGURATIONS FOR <br />THE PORTAL BENCH AREAS AT THE KING COAL MINE. THESE ANALYSES SHALL <br />UTILIZE ACCEPTED SLOPE STABILITY MATHEMATICAL ANALYSIS TECHNIQUES, <br />MATERIAL STRENGTH DETERMINATIONS RND APPROPRIATELY DETAILED GEO- <br />TECHNICAL KNOWLEDGE OF THE SITE, IN ORDER TO COMPLETE THE REQUIRED <br />STABILITY DEMONSTRATION. R REPORT OF THIS REQUIRED STABILITY ANALYSIS <br />AND THE APPROPRIATE GEOTECHNICAL INVESTIGATIONS OR OTHER INFORMATION <br />ACCEPTABLE TO THE DIVISION DEMONSTRATING STABILITY, SHALL BE SUBMITTED <br />TO THE DIVISION FOR APPROVAL WITHIN 120 DAPS FOLLOWING ISSUANCE OF THE <br />APPROVED PERMIT. <br />With the acceptance of this stipulation, the operation will be in compliance. _ <br />