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of draw. Slopes facing towards the mined-out area will result in larger angles of draw. At the present time, the
<br /> influence of irregular topography on the angle of draw has yet to be quantified.
<br /> It is anticipated that the irregular topography in the Permit Area will cause some variation in the angle of draw. This
<br /> is consistent with preliminary observations from the longwall subsidence monitoring area above the No. 5 Mine where
<br /> the steeper slope facing away from the gob area had a significantly reduced angle of draw. Three draw angles along
<br /> monitoring lines, as shown on the Subsidence Monitoring Map (Map 31, were measured. The results of these
<br /> measurements are shown on Table 86,Draw Angle Versus Slope and Orientation.
<br /> A careful review and evaluation of the site-specific subsidence data and the site-specific geotechnical data determined
<br /> the predicted angle of draw for the No. 5 and No. 6 Mines. This data was compared with research data from York
<br /> Canyon,New Mexico (Gentry, Stewart, and King, 1981),Kemira Colliery,Australia, (Kapp, 1974),Paonia, Colorado
<br /> (Dunrud, 1976), and Utah (Allgaier, 1982; and SUFCO, Personal Communication, 1986). The geotechnical
<br /> environment in the permit is similar to that found throughout the MCM Mine complex as well as the various coalfields
<br /> of the western United States. An angle of draw of 19 degrees is predicted as a conservative average draw angle for the
<br /> permit area.
<br /> SUBSIDENCE CONTROL PLAN
<br /> MCM has prepared this Subsidence Control Plan to outline the proposed measures that may be taken, if required, to
<br /> restore any affected structures or resource lands to their pre-subsidence condition. This section specifically addresses
<br /> the structures present in the permit area. The only renewable resource lands potentially impacted by subsidence are
<br /> the surface and subsurface water resources. The proposed mitigation measures for the surface and subsurface water
<br /> resources are discussed in Section 2.05.6,Mitigation of the Impacts of Mining Operations.
<br /> Mine Facilities (Presently Undermined) The mine facilities in the Permit Area that are presently undermined include
<br /> mine roads, powerlines, water-lines, the railroad spur, the coal storage silo, and the coal transport facilities. These
<br /> facilities are presently located over development entries (mains and sub-mains) which are designed to remain stable
<br /> for the life of the mine. These areas have been protected against subsidence damage by ensuring that sufficient coal
<br /> was left in place to prevent or minimize subsidence in the area. Given the time period that has elapsed since these
<br /> entries were developed, and that no discernible surface subsidence has been detected, the potential for any future
<br /> subsidence is negligible, however,if subsidence were to occur and the structures or facilities were to be damaged,they
<br /> will be repaired,replaced, or demolished and removed at MCM's option. In addition, areas of Trapper Mining, Inc.'s
<br /> surface mining operation which have been previously mined and reclaimed have been partially undermined. The
<br /> Trapper Mining reclaimed areas that have been undermined including reclaimed mine areas,two topsoil stockpiles, an
<br /> access road leading to the topsoil stockpiles, and several small stock ponds were undermined without any material
<br /> damage. While future subsidence is unlikely, if subsidence were to occur,MCM would assess any surface subsidence
<br /> effects relative to potential stability and drainage effects,and make any necessary repairs,as indicated.
<br /> Mine Facilities (Previously Planned To Be Undermined) The mine facilities under which proposed mining would
<br /> have taken place include limited surface facilities and portions of MCM's underground mine workings. The MCM
<br /> surface facilities that would have been undermined include Sedimentation Ponds SH-P1, SH-P2, the Old Shop and
<br /> storage area and the Storage and wood shop (both reclaimed in 2008), a rock dust tank (removed), the contractor
<br /> staging area,\and the Okie Plaza Well. Where limited mining has already occurred, it is anticipated that a general
<br /> lowering of the ground surface, localized changes in grade, and minor cracking may occur, and that any associated
<br /> subsidence effects could necessitate minor repairs to these facilities. Given that no future mining is anticipated,Ponds
<br /> SH-P1 and SH-P2 and Ditches SH-D2 and SH-D3 will not be impacted. The rock dust tank has been removed so no
<br /> effects are anticipated. No facilities except an empty water tank are located at the contractor staging area, so no
<br /> effects are anticipated. The Okie Plaza Well will not be undermined. The only underground workings that have been
<br /> undermined are limited areas of underground development entries. Portions of the No. 5 Mine mains and sub-mains
<br /> are located over development entries(mains and sub-mains)of the No. 6 Mine. The No. 6 Mine development entries
<br /> RN18-07 2.05-63 Revised 10/19/18
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