2011-09-23_REPORT - C1980007 ‎(8)‎

• Permit No: C1980007
• IBM Index Class Name: REPORT
• Doc Date: 9/23/2011
• Doc Name: Spring 2011 Subsidence Report - Appendix A Thru C ‎(Part 2 of 3)‎
• From: Wright Water Engineers, Inc
• To: DRMS
• Permit Index Doc Type: Subsidence Report
• Email Name: TAK
• Media Type: D
• Archive: No

Monument Used
Horizontal Distance*
(feet)
Vertical Distance
(feet)
Angle of Draw
(p)
10
330
1139
16.6°
37
340
1290
14.8°
57
290
1197
13.6°
80
290
1165
14.0°
101
380
1145
18.4°
•
•
•
Memorandum to Ryan Sweetwood and Kathy Welt
August 2, 2010 (Revised February 1, 2011)
Page 2
Angle of Draw (0) = Tan -1
Vertical Distance )
where:
the horizontal distance is from the nearest point on the ground surface with no discernable
longwall subsidence perpendicular to a vertical line projected from the boundary of the
longwall panel, and
the vertical distance is from the top of the coal seam at the longwall panel boundary to the
ground elevation equal to the point of no discernable longwall subsidence.
Table 1 provides a summary of the calculated angle of draw at the various panel edges using ground
elevation data from the E -seam survey monuments and top of E -Seam elevations from Map 17 of
MCC's permit document. This information has been revised from that originally submitted (based
on interpretation of E -Seam overburden mapping) in WWE's August 2, 2010 memorandum. This
revision is in response to a question raised by Mr. Tom Kaldenbach of the Colorado Division of
Reclamation, Mining and Safety regarding the calculation of the angle of draw. He'd questioned
whether the point of no discernable longwall subsidence was located on the ground surface or on a
normalized horizontal line representing the differential vertical displacement, as is usually depicted
in reference materials, including that of the National Coal Board. After further review of the
relevant literature and WWE's previous work, we concur that the line determining the angle of draw
is the representative angle between a vertical line over the panel extraction boundary and a line
drawn from the edge of the panel to the point on the ground representing no discernable longwall
subsidence.
TABLE 1
Angle of Draw Calculations
*All horizontal distances are perpendicular to the coal extraction boundary.
(Horizontal Distance