2014-06-19_PERMIT FILE - C1981019A

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 6/19/2014
• Doc Name: Geotechnical Stability Report For Highwall Mining At the Colowyo Coal Mine
• Section_Exhibit Name: Exhibit 23, Item 1
• Media Type: D
• Archive: Yes

July 23, 2013
LIST OF TABLES
Page ii
Page
Table 1.
Characteristics of the Target Seams in the South Taylor Pit ........... ..............................4
Table 2.
Characteristics of the Target Seams in the West Pit ........................ ..............................4
Table 3.
Summary of F E D2 and C Seam Physical Properties from Previous Highwall
Figure 4.
MiningStudies ................................................................................ .............................34
Table 4.
Summary of Physical Property Test Results, GT -0 1 Holes ............ .............................35
Table 5.
Summary of Physical Property Test Results, South Taylor 2006 and 2007 Holes ......
35
Table 6.
Slake Durability Classification ....................................................... .............................35
Table 7.
Normalized Coal Strengths ............................................................ .............................38
l
Table 8.
Input Parameters Used for the LAMODEL Analyses ................... .............................55
LIST OF FIGURES
Figure 1. Current South Taylor and West Pit Study Areas in Relation to Previous
Agapito Associates, Inc.
Highwall Mining Study Areas ..................................................... ..............................2
Figure 2.
South Taylor Pit, G7 Seam Floor Elevations ............................... ..............................5
Figure 3.
South Taylor Pit, G7 Seam Thickness .......................................... ..............................6
Figure 4.
South Taylor Pit, G78 Seam Thickness ........................................ ..............................7
Figure 5.
South Taylor Pit, G7 Seam Cover Depth ...................................... ..............................8
Figure 6.
South Taylor Pit, G7 to E Interburden .......................................... ..............................9
Figure 7.
South Taylor Pit, E Seam Floor Elevation ................................... .............................10
Figure 8.
South Taylor Pit, E Seam Thickness ........................................... ..............................1
l
Figure 9.
South Taylor Pit, E /D2 Seam Thickness ...................................... .............................12
Figure 10.
South Taylor Pit, E Seam Cover .................................................. .............................13
Figure 11.
West Pit, F Seam Floor Elevation ................................................ .............................14
Figure 12.
West Pit, F Seam Thickness ......................................................... .............................15
Figure 13.
West Pit, F Seam Cover Depth .................................................... .............................16
Figure 14.
West Pit, F to E Interburden ........................................................ .............................17
Figure 15.
West Pit, E Seam Floor Elevation ................................................ .............................18
Figure 16.
West Pit, E Seam Thickness ........................................................ .............................19
Figure 17.
West Pit, E Seam Cover ............................................................... .............................20
Figure 18.
West Pit, E to D2 Interburden ...................................................... .............................21
Figure 19.
West Pit, D2 Seam Floor Elevation ............................................. .............................22
Figure 20.
West Pit, D2 Seam Thickness ...................................................... .............................23
Figure 21.
West Pit, D2 Seam Cover Depth .................................................. .............................24
Figure 22.
West Pit, D2 to C Interburden ...................................................... .............................25
Figure 23.
West Pit, C Seam Floor Elevation ............................................... .............................26
Figure 24.
West Pit, C Seam Thickness ........................................................ .............................27
Figure 25.
West Pit, C Seam Cover ............................................................... .............................28
Figure 26.
View of the South Taylor Pit Box Cut, Looking Southwest ........ .............................30
Figure 27.
View of the South Taylor Pit Low Wall Looking South ............. .............................31
Figure 28.
View of the West Pit Highwall Looking West ............................ .............................32
Figure 29a.
Web Pillar Design Chart-South Taylor Pit, G7 and G 78 Seams ...........................39
Figure 29b.
Barrier Pillar Design Chart-South Taylor Pit, G7 and G 78 Seams ......................40
Figure 29c.
Raw Recovery-South Taylor Pit, G7 and G 78 Seams ............. .............................41
Figure 30a.
Web Pillar Design Chart- South Taylor Pit, E and D2 /E Seams ............................42
Agapito Associates, Inc.