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3.3 DRILLING <br />3.3.1 Tvpes of Drilling <br />At Trapper Mine there are three types of drilling: blast hole drilling, explora- <br />tion drilling and development drilling. Blast hole drilling occurs only within <br />the permit area and is required for the blasCing operation. The boles are needed <br />for placement of expiosives to fragment overburden, interburden and coal. Holes <br />sizes, depths and spacings vary according to the thickness and nature of the <br />material to be blasted. Because the holes are drilled just ahead of, of within <br />an advancing pit, they are removed by stripping or mining within several months <br />or less. Fvr more detail on blasting, see Section 3.4. <br />Exploration drilling occurs outside the permit area and is required to determine <br />the extent of the coal reserves and to provide information on coal depth, thick- <br />ness and quality. A11 exploration drilling is conducted in compliance with <br />applicable U.S, Bureau of Land Management and S[aCe of Colorado regulations and <br />will be handled by separate permits, <br />Development drilling is required to provide data for planning pit dimensions, <br />s equencing activities and equipment scheduling. Typically, development drilling <br />is conducted at or near the projected coal cropline and tAe economic stripping <br />limit ahead of advancing pits and where new pits are planned within the permit <br />area. Drilling depths needed to further define the cropline are usually only to <br />the coal in question. Depending upon the information obtained, drilling may be <br />conducted defining the cropline to within 25 feet horizontally. The economic <br />stripping limit is defined in much the same manner except it is not necessarily <br />located as accurately as [he cropline. <br />Prior to stripping, the overburden is drilled and blasted, Overburden drilling <br />and blasting precedes stripping by one to five pit widths. Before the overburden <br />is drilled and blasted, the topsoil is removed. Topsoil removal is conducted <br />during the fair aeathet months of May throughOctober. Therefore, each year's <br />3-22 f{~iS~~H <br />APPROVED <br />paw 2y9-8~' <br />~llz-~`7' <br />_ RE111SED FEB 10 ~8a <br />