2021-05-27_PERMIT FILE - C1981019 (10)

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March 21, 2014 Page 29 At the time of the site visit, the South Taylor box cut was nearing completion, with the G78 seam being actively mined (Figures 26 and 27). Conditions in the box cut were good, with no obvious wall instabilities, and no water seeps. Colowyo personnel confirmed that as with other pits, water seeps are seasonal. Most of the current highwall in the West Pit was covered by spoils, with only the western end of the highwall visible (Figure 28). Colowyo personnel indicated that no major highwall instabilities have been experienced in recent years, and spoil stability is generally good. Previous studies have shown that joint and cleat orientations are generally consistent over a wide area and between seams with a primary orientation averaging 305 degrees ( °) (N55 °W) with near - vertical dips (NSA 2003). Secondary joints and cleats are oriented at approximately 25° (N25 °E), again with near - vertical dips. Spacing of joints is generally 0.5 ft to 4 ft. A summary of joint/cleat trends presented by Shannon and Wilson (2008) indicates that these orientations rotate somewhat to the north in the South Taylor area (with primary joint/cleat orientations of 310° to 335 °). Although it has been speculated that faulting may affect future pits, no major faults have been encountered in existing pits (CTL Thompson 2003, Shannon and Wilson 2008). Underground mining from various mines has been performed on the property in the past with limited areal extent (Anon). The Red Wing and Streeter mines operated in the FAB Seams on the eastern boundary of the reserve. The Streeter also operated in the G78 Seam. Both were room -and- pillar mines. Various coal recovery methods were practiced, but in general, 8 -ft -high entries up to 30 ft wide were developed on advance, with removal of top coal, floor coal, and pillaring on retreat. Roof conditions were reported to be very good with several pillared areas standing for long periods before caving. Other small, family- operated mines are known to have existed, but not many details of these operations are available. Spontaneous combustion has not been a problem in previous highwall mining on the property, and it is not anticipated that spontaneous combustion problems will arise in the South Taylor or West Pit study areas. No structures or infrastructure exist above the highwall mining areas of the current study, therefore special subsidence protection measures are not required. 2.2 Lithology For the purposes of the current study, lithologic logs from existing core holes were reviewed. Particular focus was placed on holes nearest to the current study areas, including HW- 03-01, -02, -03, and -04 (NSA 2003), WP -05 -07 (AAI 2005b), and ST -06 -02 and ST -08 -13 (Shannon and Wilson 2008). The locations for these holes is shown on Figure 1, and lithologic logs are presented in the Appendix. The bounding strata of the target seams, as represented in the core, can be classified into four primary rock types: sandstone, siltstone, mudstone, and carbonaceous mudstone /shale. Interbeds of sandstone, siltstone, and mudstone are common. Sandstone is the most common rock type, comprising 38% of bounding strata in the HW -03 holes, 63% in the WP -05 -07 hole, and 43% in the South Taylor (ST) holes. The sandstone is generally undisturbed, with the majority of rock quality designations (RQDs) above 80. Mudstone is the second most abundant Agapito Associates, Inc.