2008-02-22_APPLICATION CORRESPONDENCE - C2008086 ‎(43)‎

• Permit No: C2008086
• IBM Index Class Name: Application Correspondence
• Doc Date: 2/22/2008
• Doc Name: PDEIS Appendix C Subsidence
• Media Type: D
• Archive: No

1.0 INTRODUCTION
Estimated subsidence magnitudes presented in this Draft Environmental Impact
Statement for the Red Cliff Mine, Project Area containing the Coal Lease Application and
the Existing Coal Lease areas are planned for principally longwall mining of coal north of
Mack and Loma Colorado and the south facing Book Cliffs and east of Colorado State
Highway 139 as indicated on the general location map titled Red Cliff Mine, Proposed
Mine Facilities and Rail Spur. The Coal Lease Application area is east of the Existing
Coal Lease that includes the active McClane Canyon Mine and the closed and reclaimed
Munger Mine.
2.0 DEFINITION OF TERMS AND SYMBOLS
Terms used to evaluate and analyze subsidence processes and amounts are described
below.
Longwall Mining: See Affected Environment/Subsidence for an overview of underground
coal mining.
Mining Panel: A rectangular mining area where mine openings are developed and coal is
extracted. In longwall mining panels, development entries, or gate roads, are driven at
either side of the panel boundaries and the intervening coal is extracted with a longwall
cutting machine.
Headgate: Entries and crosscuts driven on the side of the mining panel adjacent to
unmined coal, and on the side of the panel that is in the direction of further panel
development and used for removal by belt of coal as cut from the longwall face and
bringing ventilation to the longwall face.
Tailgate: Entries and crosscuts driven on the opposite side of the mining panel from the
head gate entries and provide a path for return ventilation air from the face.
Panel Length and Width (W, L): The length and width of the longwall panel where coal is
being extracted.
Subsidence: The vertical downward movement of the overburden and ground surface
caused by extracting the coal.
Maximum Subsidence: The maximum vertical downward movement of the overburden
and ground surface above the center of the panel caused by extracting the coal.
Tilt and Maximum Tilt (M): The inclination of the ground surface caused by mining the
coal in a longwall panel, the vertical displacement difference between two points on the
ground surface divided by the horizontal distance between these points; maximum tilt is
the maximum inclination that develops as the ground surface deflects downward towards
the center of a panel, i.e. the subsidence trough.
Maximum Strain (+E, -E): Strain is the change in length between two points of
measurement divided by the original distance between these two points (unit change in
length); tensile strain (+e) is the unit elongation between any two points on the surface
moving further apart (unit elongation) as the ground surface deflects downward towards
C-1
DBMS 293