2008-01-16_APPLICATION CORRESPONDENCE - C2008086 ‎(3)‎

• Permit No: C2008086
• IBM Index Class Name: Application Correspondence
• Doc Date: 1/16/2008
• Doc Name: Preliminary Draft Environmental Impact Statement/Subsidence
• Media Type: D
• Archive: No

DRAFT
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 Environmet/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 the center of a panel;
compressive strain (-e) is the unit shortening between any two points on the surface moving
closer together as the ground surface deflects downward towards the center of a panel. The
maximum values are for the unique conditions present at an individual panel.
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