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
Page i
GEOTECHNICAL DESIGN AND OPERATIONAL CONSIDERATIONS FOR
HIGHWALL MINING, SOUTH TAYLOR PIT G78 AND E/D2 SEAMS, AND
WEST PIT F, E, D2, AND C SEAMS
TABLE OF CONTENTS
Page
EXECUTIVESUMMARY ............................................................................ ............................... iv
1.0 INTRODUCTION ................................................................................. ..............................1
2.0 SITE CHARACTERIZATION ............................................................. ..............................3
2.1 Site Geology and Seam Settings ............................................... ..............................3
2.2 Lithology .................................................................................. .............................29
2.3 Physical Property Test Results ................................................. .............................33
3.0 HIGHWALL MINING CONSIDERATIONS .................................... .............................36
3.1 Seam Characteristics ................................................................ .............................36
3.2 Roof Stability ........................................................................... .............................36
4.0 SITE CHARACTERIZATION ............................................................ .............................37
4.1 Design Approach ..................................................................... .............................37
4.2 Web and Barrier Pillar Design ................................................. .............................38
5.0 NUMERICAL MODELING ANALYSIS ........................................... .............................54
6.0 OPERATIONAL CONSIDERATIONS ............................................... .............................55
7.0 REFERENCES .................................................................................... .............................60
APPENDIX— LITHOLOGY LOGS FOR SELECTED BOREHOLES .... ............................... A -1
DISCLAIMER: This report contains professional opinions based on information provided by
the Owner. AAI makes no warranties, either expressed or implied, as to the accuracy or
completeness of the information herein. Opinions are based on subjective interpretations of
geotechnical data; other equally valid interpretations may exist. Identification and control of
hazardous conditions are the responsibilities of the Owner.
Agapito Associates, Inc.