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changing dip of the 1~olf Creek, it does not appear that it can be mined to a depth where • <br />interaction with the Wadge would be a concern. Therefore, the only seam interaction that <br />was analyzed was that of the Sage Creek/Wolf Creek Seams. <br />Table 1. Summary of physical characteristics of the two study areas. <br /> Parameter Minimum. ft Maximum. ft <br />Seneca IlW Wadge cover 80 380 <br /> Wadee thickness 7 ]3 <br /> ~>,tadge-Sage Creek interburden n/a n/a <br /> Sage Creek cover 0 280 <br /> Sage Creek thickness 3 6 <br /> Saee Creek-Wolf Creek interburden 0 ] 20 <br /> Wolf Creek cover 0 440 <br /> Wolf Creek thickness 12 25 <br /> <br />Yoast Wadge cover 60 460 <br /> Wadee thickness 8 ] 5 <br /> Wadee-Wolf Creek interburden 160 220 <br /> Wolf Creek cover 0 280 <br /> Wolf Creek thickness 6 19 <br />In the limited areas where the thickness of the seams is lower than the minimum • <br />mining height of the PM (50 in), highwal] mining is not planned. <br />NSA did not perform structural mapping as part of this project: however. a <br />previous study for auger mining (HMS, 7998) was reviewed for structural data. In the <br />Seneca IIW Area, two primary joint/cleat directions were identified. with trends of N47E <br />and N69E. In the Yoast area. the primary joint/cleats sets trend Nl2E and N ] 9E. Joint <br />orientations in both areas are shown on Figure 1. It was noted that in the Yoast Area. the <br />structure is more intensely developed. Joints are generally steeply dipping. within l0° to <br />] 5° of vertical. Joint spacing in the Seneca IIW Area vas noted to be on the order of 2 to <br />5 ft; a more dense joint spacing is assumed for the Yoast Area. The coal itself is strong, <br />with we]]-defined roof and floor contacts. Keeping in seam with the miner should not be <br />difficult given these contacts. Some faulting is present within both areas: however. it is <br />not considered to be significant and is not expected to cause disruptions to the mining <br />plan. <br />2.2 Core and Site Observations <br />A significant amount of core drilling and mechanical property testing has been <br />undertaken on the property over the years. This core drilling has been primarily from <br />areas to the north and west of the subject highwall mining areas. To determine the <br />applicability of these data to design, core from ttao holes in the Yoast Area (holes 3319C <br />and 3320C) were selected for mechanical testing. This core covered the Wolf Creek • <br />Seam, roof. and floor, and the floor of the Sage Creek Seam. No suitable samples for <br />Seneca Coal Company J '~5.4 Engineering, In<. <br />HighH~all t•9ine Design Repon June 2003 <br />