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Upper roof Lower roof Immediate floor 6~ 6~ E 8-16 ft above the top of the coal seam 0-8 ft above the top of the coal seam 0-]0 ft below the base of the coal seam uniaxial compressive strength indirect tensile strength Young's modulus V Slake durability (first cycle %/second cycle %o) Table 2. Summary of physical property test results for cores from the Yoast Area. Strata Location Rock T}pe 6si psi x•106 S, is Sage Creek floor/ Shale 3.595 0.64 57.6/31.1 Wolf Creek upper roof Sandstone 5.120 0.87 - Wolf Creek lower roof Shale 5.390 0.74 - Sandstone 4.170 - - Wolf Creek coal Coal 2.080 0.28 - I Wolf Creek floor Shale 4.83 0.82 9].4/79.2 I All Sandstone 4.487 0.87 - All Shale 4.822 0.75 80.2 / 63.1 The data in Table 2 show that the coal-bounding strata in the Yoast Area are moderately strong compared with strata found at other western surface mining operations. To compare the test results from this study with the extensive Peabody database. a summary of that data is given in Table 3. Table 3. Summary of physical property test results from the Peabody database. Rock T e )'P 6" si E' 6 psi x ] 0 6'` si Wadgecoal 5.037 0.5] ]~~ Sage Creek coal - - - Wolf Creek coal 5.042 O.SI 169 Shale 5.300 1.42 355 Mudstone 9.500 1.59 338 Siltstone 6.000 2.19 362 Sandstone 5.600 1.82 465 As previously noted. the core tested during this study was not fresh and had lost some of its inherent moisture. This probably explains why the coal UCS values shown in Table 2 are significantly lower than those from the Peabody database. The values from the Peabody database are the result of extensive testing (327 samples of the \\%adge Seam and ] 67 samples of the \tJolf Creek Seam), and it is NSA's opinion that the higher values from the Peabody database are likely more representative of the coal strength in the LJ • • Seneca Coal Company ~ NSA Eneineering. Inc. Hiehwall Mine De<im Repon Tune 2003