PERMFILE44895

• Permit No: C1980007
• IBM Index Class Name: Permit File
• Doc Date: 6/2/2006
• Doc Name: for the West Flatiron Lease Area
• Section_Exhibit Name: Exhibit 60C Subsidence Eval & 2004 Geologic Hazard Field Obsersvations
• Media Type: D
• Archive: No

Exhibit sot
Subsidence Evaluation and 2004 Geologic Hazard Field Observations
• West Flatiron Lease Area
TABLE 1
Maximum Subsidence Parameters For
West Flatiron Lease Area m
•

Parameter Pane11 SA (t=12fU Panels 18-19 (1=12 ft) m Panels 20.21 (t-12ft)
W/d: Max
Min 18A 690/800 = 1.15
690/1310 = 0.53 18 9701750 = 1.29
970/1700 = 0.58 20 970 / 1030 = 0.94
970!2250 = 0.43
Max
Min 19 9701910 = 1.07
970/2250 = 0.43 21 970 / 1300 = 0.75
970 / 2175 = 0.45
S~=a~•tr°I
(a,A=S,y/tj 1.7 to3.8ft
(0.14 to 0.32) 2.2 to8,5ft
(0.18 to 0.54) 2.9 to6.5ft
(024 to 0.54)
Sm=a•tk~
(a = Sa11) 6.0 to 9,6
(0.5 to 0.8) 4.8 to9,6ft
(0.4 to 0.8) 4.8 to9.Oft
(0.4 to 0.75)
S~/d ro1 (0.005 to 0.016) (0.0021 to 0.013) (0.0021 tp 0.009)
M,° (2.2 l0 3.0 S~/d) m 0.011 to 0.048 0.005 to 0.039 0.005 to 0.027
Em (in terms of S,,,Id) m 0.006 to 0.024 0.003 t0 0.020 0.003 io 0.014
-ER, (m terms of sad> °~
(-1.310 -24 S„~d) .a.txts m -0.038 .O.pp3 to-0.031 -0.003 to -0.022
Maximkun Cradle 1 5 -15 ft 5- ZO ft 5- i5 ft
Depths 2 10-20ft 10-35R 10-20ft
Break Anglei1°r 0-5° 0-5° 0-5°
Angle of Drawr1°t 10-20° 10-20° 10-20°
t't Mardmum subsidence parameters inducts the total length of mining panels 18-21, and therefore indude the Box
Canyon mining area as well as the West Flatiron Lease area; t is the average coal extraction thickness (12 ft), which
may be more or less than this average.
m Maximum verticel displacement, fill, and horizontal strain apply to ground surfaces with sopes less that 30%;
vahres may be hgher on slopes greater that 30 percent.
mAll brxlwall panels are numbered aaordug to their planned panel idenfificetion.
<a Subsidence and subsidence factor above gate road (chain) pillars,
/~ Maximum vertical displacement (subsidence) range above the longwall panel centers, based on the average
planned coal extraction thickness of 12 feet, is obtained from Figure 4, 6dribd 60B.
m Ratio of the range of maximum verticel displacement to overburden ttepth range for the five projected lorgwall
panels. Minimum overburden depth to the B seam is lokxted in the Raven Gulch tributary in the West Flatiron lease
area above the projected cenfedures of bngrra0 panels 18 through 21. Minimum overburden depth of the projected
cen[errrm of brKfwall panel 18A (600 feet) is located 300 feet west of the east West flatiron Lease botmdary_
m Maximum range of tiR values, in terms of Smld, is obtained from Fgure 1.
m Maximum range of positive and negalrve trorizontal strain in terms of Say/d a obtained from Figure 1.
w Ma~dmum cradle depth (in feet) in bedrock that is estimated to IocaOy occur near dills, ledges, w steep slopes on
either side of West Flatiron. The first depth range (1) Ls fw bedrock sbping less than w equal ro 30 percent The
second depth range (2) Ls for steep bedrodk sloping more than 30 percent and diffs. No cracks are predrded to
coon b alluvium. No kxadks are predicted to ocwr al the surface of colluvium thidker than about 10 feet
k10r Predicted range of break angle and angle of draw, measured from a vertical reference.
831-032.650 Wright Water Engineers, Inc Page 11
November 2004