2017-01-04_PERMIT FILE - C1981044A

• Permit No: C1981044A
• IBM Index Class Name: Permit File
• Doc Date: 1/4/2017
• Section_Exhibit Name: 2.05 Operation and Reclamation Plans
• Media Type: D
• Archive: Yes

longwall panels are mined. Specific longwall layouts may vary according to mining conditions and approved MSHA
plans.
Extent of Planned Subsidence
The development and magnitudes of surface subsidence and angles of draw are controlled by geotechnical parameters
characteristic of the specific mine site and the mine plan. The critical geotechnical parameters affecting subsidence
include:
• Overburden Depth
• Surface Topography
• Overburden Geology (Stratigraphy and Structure)
Overburden Depth. Overburden thickness above the planned No. 6 Mine varies from approximately 200 feet in the
southwest corner of the longwall area to more than 1600 feet in the northeast corner. The overburden depths for areas
where detailed subsidence calculations have been developed vary from 300 feet to 1600 feet.
Surface Topo r� aphh_v. The surface topography overlying the planned No. 6 Mine is controlled by the drainages of the
Yampa and Williams Fork Rivers, the Williams Fork Mountains, as well as the geologic framework. The surface
topography overlying the five (5) year permit area is composed of two (2) principal land forms, 1) the flood plain of
the Williams Fork River and 2) a northeast dipping valley slope formed by the flank of the Williams Fork Mountains.
The floodplain of the Yampa and Williams Fork Rivers are generally flat with almost no topographic relief. No
longwall mining is planned beneath the flood plain of either the Yampa or Williams Fork Rivers.
The northeast dipping valley slope formed by the flank of the Williams Fork Mountains is a gradual rolling slope.
The general slope trend is modified by a system of northerly trending gullies. These gullies locally reach depths of up
to 100 feet. Their side slopes are generally less than 20 degrees. These slopes are generally stable.
Portions of the surface topography are reclaimed surface mining lands, which have been reclaimed to the approximate
original contour.
Overburden Geology (Stratieraphv and Structure). The geology of the permit area is discussed in detail in Section
2.04.6, Geology Description. This section presents the pertinent aspects of overburden geology as they relate to
surface and overburden subsidence effects.
The stratigraphic section above the planned mine area includes both soil and rock overburden and locally, surface
mining overburden spoil. Soil overburden is generally thin (less than 20 feet) and is restricted to the alluvial valley
floors. Overburden spoil in the planned longwall area varies in thickness from 0 feet to approximately 100 feet. EC
has drilled two (2) exploration test borings in the longwall mining area for the No. 5 Mine. The overburden spoil in
these two (2) test borings was a clayey, fine-grained material. No large blocks of rocks were encountered by the
drilling. In addition, no voids were encountered by the drilling. The boreholes tended to remain open after drilling,
allowing easy installation of casing. Also, no water was encountered during drilling.
Analysis of previous overburden test drilling in the No. 5 Mine area indicated that the overburden consisted, on the
average, of the Iithotypes indicated in Table 81, Average Percentages of Various Lithotypes in the Overburden at the
EC Mine Complex. A review of the lithotype percentages in test borings 83-04, 83-17, 83-22, and 83-25 indicated
that the overburden above the longwall mining planned for the No. 6 Mine is the same as that occurring throughout
the EC Mine complex.
The planned longwall mining area is located on the northern flank of the Williams Fork Anticline. The bedding dips
uniformly to the northeast at approximately 6.5 degrees. No faulting is known to exist within the planned mining area.
Joint patterns are not well defined. Observations of surface outcrops indicate that jointing in the massive
Permit Revision 04-34 2.05-56 Revised 7/2/04