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3 _3 DRILLING <br />3.3.1 Tvpes of Drilli~ <br />AG TcapQgr Mine them are three types Of drilling~ blast hole dsilli~;g, axp2ora- <br />tion gri'~ling and development dri.Lling. Blast hole ~Srillin8 oycC.FS only r,~izkia <br />the Q@rmi_t Brea aRd Ls tegVizad For the blasting operatiQn• The hele$ arE meeaed <br />fot QLacemzht of ax4losives. tp ftag~i~enC oVerburdenr ihterburdep a~ eoa2. Hoies <br />sizest depths and spacings vary eCcordigg to the thic~~ess ~.od nat~rg of the <br />material to be blasted. Because the holes are drilled just ahead D.€, ~: };ii~;in <br />an adbanring pit, they are removed by stripping or mLning within Gevora? i,unahs <br />or less. For taore_ da_tail Rn bla„cing> see Section 3.h. <br />Explora[3on drilling occur" outside tht permit hre:t and is te9uired to dezpsm.;nQ <br />the ekteht of the coal reshrvns and to provide inf7rmation On coal depth, Ybirk- <br />ness and quality. All ekploration dril.liRg Ss conducted ih ComAliance w;rb <br />applihable U.S, Bureau of Land Alanagemen[ and Stage 4f Colorado reSulaCio?vs and <br />will be handled by separatR QRrmits. <br />Develt~pment drillinP ix, required 5o proWid® d$ta for plagnigg pit ditnensioos, <br />sequehci\ig activities and equipment scheduling. Typically, development drilling <br />is conducted at Gr hear the projected coal cropline anal the ecohomic strioPioB <br />litinit ahead. o£ advahcing l,it~ ahd where new pits are planned within the ;narnii <br />area. Drilling depths needed to further define the cropline are usually oo]y so <br />the Coal in g4es[ioQ• Depend,in~ upon the informahioh obtained, drilling may be <br />conducted def%ninp Che cropline CO within 35 feet horizon[ally. The econasic <br />stripping Limit is defined in mAch the same magnet except 1t is not necessarily <br />located as accurately as the cropline• <br />Prior to stripping, chs overburiten is drilled and blasted. Overburden drilling <br />aqd blasting precedes stripping by one to five Pit wii([h5. Before the ovefburden <br />is drilled and blasted, [he topsoil is removed. Topsgil removal is conducted <br />dyrinp the fair weather months of May [h rough October. Therefore, each year's <br />M~z ~ ~a y <br />~~v~s~n ~~ 1o'~a <br />