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In the design of the mine plan a minimum of 50 feet of interburden was used as minimum <br />• criteria for the consideration of multiple seam mining. Because of better quality and more <br />consistent seam height mining of the upper portion of the Carbonera zone is planned. This seam <br />will be mined in areas that exceed 5 feet in thickness, which is the minimum thickness considered <br />compatible with the mining machinery that will also be used to mine thicker seam areas. <br />Cameo Seam <br />The Cameo seam exists as the Upper and Lower Cameo splits, and the total Cameo seam <br />(unsplit). Height varies from 5 feet in split seam area to 26 feet in the total Cameo seam. Eleven <br />feet is considered the maximum mining height using current technology. In areas that exceed this <br />maximum (11 feet), the upper portion of the seam will be mined first. The lower portion of the <br />seam may be extracted on retreat. <br />In the area of the existing main entries the Cameo seam is split into the upper and lower seams. <br />These splits merge into a single thick seam both to the north and south. The entries, which are <br />developed in the lower split, are overlain by a small upper split area which based on the minimum <br />50 feet interburden, may be minable. To avoid creating stress concentrations, and preserve the <br />• integrity of the lower main entries, mining of this split will be delayed until the latter years of the <br />project. Mining of this area may possibly cause problems in the lower main entries the early failure <br />of which could loss of the entire coal reserve. <br />As shown in Figures 2.1-1 and 2.1-4, it is planned to develop the Cameo seam to the south <br />during this permit term (5 years}, from the point where the developed main entries change direction. <br />Later development (years 6 through S) will be north from the above noted eastern extreme of the <br />property boundary in the Cameo seam, and will coincide with the undertaking of secondary mining <br />in the southern portion of the mine plan area. <br />As described in Section 2.1.1 all development work will be done with afive-entry system. <br />Adequate bamer pillars will be left to protect the main entries and main entry barrier pillars in the <br />Carbonera will precede, by at least two years, any secondary mining in areas of the Cameo seam <br />which underlie Carbonera workings. This time should be adequate for equilibrium of stresses to be <br />achieved. <br />As noted, minable reserves are based upon seam thickness from a minimum of 5 feet to a <br />maximum of 11 feet, with a minimum 50 foot interburden in multiple seam areas. The mining plan <br />. provides for 75 percent recovery of noted seam thickness. Areas not accessible by logical mining <br />INS Page 2.1 - 6 10-12-00 <br />