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March 21, 2014 <br />Page 51 <br />Design Depth <br />Mining Height (ft) <br />of Cover (ft) <br />4 <br />4.25 <br />4.5 <br />4.75 <br />5 <br />5.25 <br />5.5 <br />5.75 <br />6 <br />6.25 <br />6.5 <br />6.75 <br />7 <br />100 <br />39 <br />41 <br />44 <br />46 <br />48 <br />51 <br />53 <br />56 <br />58 <br />60 <br />63 <br />65 <br />68 <br />120 <br />43 <br />44 <br />46 <br />47 <br />49 <br />51 <br />53 <br />56 <br />58 <br />60 <br />63 <br />65 <br />68 <br />140 <br />47 <br />48 <br />50 <br />51 <br />53 <br />55 <br />56 <br />57 <br />59 <br />60 <br />63 <br />65 <br />68 <br />160 <br />50 <br />52 <br />54 <br />56 <br />57 <br />59 <br />61 <br />62 <br />64 <br />65 <br />67 <br />68 <br />70 <br />180 <br />54 <br />56 <br />58 <br />60 <br />61 <br />63 <br />65 <br />67 <br />68 <br />70 <br />72 <br />73 <br />75 <br />200 <br />571 <br />59 <br />611 <br />63 <br />65 <br />67 <br />69 <br />71 <br />73 <br />75 <br />76 <br />78 <br />80 <br />220 <br />61 <br />63 <br />65 <br />67 <br />69 <br />71 <br />73 <br />75 <br />77 <br />79 <br />81 <br />83 <br />85 <br />240 <br />64 <br />66 <br />68 <br />71 <br />73 <br />75 <br />77 <br />79 <br />81 <br />83 <br />85 <br />87 <br />89 <br />260 <br />67 <br />69 <br />72 <br />74 <br />76 <br />79 <br />81 <br />83 <br />85 <br />87 <br />90 <br />92 <br />94 <br />280 <br />71 <br />73 <br />75 <br />77 <br />80 <br />82 <br />85 <br />87 <br />89 <br />92 <br />94 <br />96 <br />98 <br />300 <br />75 <br />77 <br />79 <br />81 <br />83 <br />86 <br />88 <br />91 <br />93 <br />96 <br />98 <br />100 <br />103 <br />320 <br />79 <br />81 <br />83 <br />861 <br />881 <br />901 <br />921 <br />941 <br />97 <br />99 <br />102 <br />104 <br />107 <br />340 <br />831 <br />85 <br />88 <br />901 <br />921 <br />941 <br />971 <br />991 <br />1011 <br />103 <br />106 <br />109 <br />111 <br />Coal Strength (psi) 871 Mining Width (ft) 11.50 <br />'Pillar widths in italics have width -to- height ratios of 0.8 <br />120 <br />t <br />U <br />C <br />x <br />o_ <br />60 <br />a <br />3 <br />8 <br />S <br />ICY <br />x <br />0 <br />50 <br />100 150 200 250 300 <br />DEPTH OF COVER (ft) <br />x <br />Q <br />J <br />J <br />5 a <br />u� <br />9 <br />0 <br />350 <br />Figure 33a. Web Pillar Design Chart —West Pit, C Seam <br />Agapito Associates, Inc. <br />No. Web Pillars 19 <br />Mining <br />Height <br />(ft) <br />4 <br />4.25 <br />4.5 <br />4.75 <br />5 <br />5.25 <br />5.5 <br />5.75 <br />6 <br />-�- <br />6.25 <br />---- 6.5 <br />6.75 <br />7 <br />i <br />100 150 200 250 300 <br />DEPTH OF COVER (ft) <br />x <br />Q <br />J <br />J <br />5 a <br />u� <br />9 <br />0 <br />350 <br />Figure 33a. Web Pillar Design Chart —West Pit, C Seam <br />Agapito Associates, Inc. <br />No. Web Pillars 19 <br />Mining <br />Height <br />(ft) <br />4 <br />4.25 <br />4.5 <br />4.75 <br />5 <br />5.25 <br />5.5 <br />5.75 <br />6 <br />-�- <br />6.25 <br />---- 6.5 <br />6.75 <br />7 <br />