2023-07-14_PERMIT FILE - C1981010 (16)

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January 2, 2020 Page 3-1 Agapito Associates, Inc. 3 HWM GEOMETRY 3.1 Opening Dimensions The cutting height range of HWM systems, including the ADDCAR system, depends on the model of continuous miner used. From Table 2-3, it appears that nearly all areas could be mined using the Joy 14CM15 continuous miner with a cutting height of 3.5 to 10.5 ft and a cutting width of 11.5 ft. Other pertinent specifications for the ADDCAR system are shown in Table 3-1. Table 3-1. Typical ADDCAR System Parameters Parameter Value Leveling capacity Front (2) lift cylinder travel 5 ft Rear (2) lift cylinder travel 5 ft Distance between lift cylinders side to side 17.75 ft Distance between lift cylinders front to back 60 ft Maximum leveling capacity side to side 16° Operational leveling capacity side to side 8° Maximum leveling capacity front to back 5° Operational leveling capacity front to back 4° Maximum walking incline 8° Platform steering radius Rotates 180° within its footprint Maximum practical downdip 20° Maximum practical side dip 8° Maximum angle off-perpendicular from highwall 15° 3.2 Infrastructure Protection Should unplanned subsidence associated with HWM occur, measures may be needed to protect sensitive infrastructure. AAI is aware of a 6-inch pipeline and several power lines in the I and J Pit areas that likely will be re-routed around the proposed mining area. While AAI is not aware of specific structures that may require protection in other areas, should structures such as power lines, pipelines, or surface facilities exist, AAI recommends that a buffer (in plan view) be established between the protected structures and the closest HWM opening. As a criterion for establishing the buffer, AAI recommends a method that incorporates a fixed offset, plus an offset based on the angle of critical deformation (Peng 1992). The angle of critical deformation is defined as the angle from the excavation edge to the protected structure, measured from vertical, beyond which no subsidence damage is expected to occur. The angle of critical deformation is generally 10° less than the more commonly cited angle of draw, which defines the distance beyond which subsidence is measurable. AAI considers a 50-ft offset and an angle of critical deformation of 25° to be appropriate. 3.3 Roof Stability Assessments of roof stability and unsupported stand-time were made using a combination of the CMRR, and the Council of Scientific & Industrial Research (CSIR) Rock Mass Rating (RMR) (Bieniawski 1989).