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3.3 DRILLING 3.3.1 Types of Drilling Ac Trappuc Mine there are three types of drilling: blast hole drilli~;g, exp2oca- tion drilling and development drilling. Blast hole drilling occurs only m~ithia the p@rmLC area and is tequirad for the blasting operation. Tha holes are heeded for pLacemettt of explosives to fragment overburden, interburden and eCa1. Holes sizes, depths and spacings vary according to the thickness and nature of the material to be blasted. Because the holes are dzill@d just ahead of, o: within an advancing pit, they are removed by stripping or mining within eeveral hmnths or less. For more detail on blasting, sec Section 3.4. Exploration drilling occurs outside the permit area and is required in determine the ektent of the coal reserves and to provide information on coal depthr ibirk- ness and quality. A11 exploration drilling is conducted ih comAliance wiLb applicable U.S, Bureau of Land Management and State of Colorado regulations and will be handled by separate permits, Development drilling ir, required to provide data for ¢lanning pit dimensions, sequencing activities and equipment scheduling. Typically, development dzitling is conducted st nr neat the projected coal cropline and the economic stripping limit ahead. of advancing pits and where new pits are planned within the permit area. Drilling depths needed to further define the cropline are usually only to the coal in question- Depending upon the information obtained, drilling may be conducted defining Che cropllne.to within 25 feet horizontally. The economic stripping Limit is defined in much the same manner except it is not necessarily located as accurately as the cropline. Prior to stripping, the overburden is drilled and blasted. Overburden drilling and blasting precedes stripping by one to five pit widths. Before the overburden is drilled and blasted, the topsoil is removed. Topsoil rermoval is conducted during the fair weather months of May throughOctober. Therefore, each year's M a-zz i{~ViSf4F( APFRaV~fJ /n~z _ ~ y R~11S~D FHB 1 D'88