2023-07-14_PERMIT FILE - C1981010 ‎(16)‎

• Permit No: C1981010
• IBM Index Class Name: Permit File
• Doc Date: 7/14/2023
• Doc Name: Summary of Geotechnical Design andf Operational Cnsiderations for Highwall Mining-I,J,N, and L Pits
• Section_Exhibit Name: Appendix X
• Media Type: D
• Archive: No

January 2, 2020 Page i
Agapito Associates, Inc.
SUMMARY OF GEOTECHNICAL DESIGN AND OPERATIONAL
CONSIDERATIONS FOR HIGHWALL MINING—I, J, N, AND L PITS,
TRAPPER MINE

TABLE OF CONTENTS

Page
1.0 INTRODUCTION ....................................................................................................... 1-1

2.0 PHYSICAL AND GEOTECHNICAL SETTING ......................................................... 2-1

3.0 HWM GEOMETRY ................................................................................................. 3-1
3.1 Opening Dimensions ........................................................................................ 3-1
3.2 Infrastructure Protection ................................................................................... 3-1
3.3 Roof Stability ................................................................................................. 3-1

4.0 PILLAR DESIGN ....................................................................................................... 4-1
4.1 Design Approach ............................................................................................. 4-1
4.2 Pillar Design Tables and Charts ....................................................................... 4-3
4.3 Numerical Modeling of Pillar Design Cases ..................................................... 4-4

5.0 RECOVERABLE RESOURCE ESTIMATE ............................................................... 5-1

6.0 OPERATIONAL CONSIDERATIONS ....................................................................... 6-1

7.0 REFERENCES............................................................................................................ 7-1

Appendix A—I Pit Web and Barrier Pillar Design Curves....................................................... A-1
Appendix B—J Pit Web and Barrier Pillar Design Curves....................................................... B-1
Appendix C—N Pit Web and Barrier Pillar Design Curves ..................................................... C-1
Appendix D—L Pit Web and Barrier Pillar Design Curves...................................................... D-1