2009-10-30_PERMIT FILE - C1982056 ‎(6)‎

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 10/30/2009
• Doc Name: WESTERN MINING DISTRICT
• Section_Exhibit Name: Exhibit 25Z WMD Subsidence Review
• Media Type: D
• Archive: No

SubTerra, Inc. Twentymile Coal Company 04/07/09
Foidel Creek Mine
�• Permit Revision PR09 -08 Subsidence Evaluation
TABLE OF CONTENTS
Section Description Page
No. No.
1. INTRODUCTION ...................................................................................... ..............................1
2. SUBSIDENCE PREDICTION ................................................................... ..............................1
3. EVALUATION OF IMPACTS TO ROUTT COUNTY ROAD 27 .............. ............................... 2
4. EVALUATION OF IMPACTS TO FISH CREEK AND ITS (AVF) ........... ............................... 2
4.1. Scope of Work ..................................................................................... ............................... 3
4.2. Subsidence Prediction ......................................................................... ............................... 3
4.3. Predicted Impacts to the AVF., ........................................................................................... 4
4.3.1. Increase in Fish Creek's Surface Area ......................................... ............................... 4
4.3.2. Potential for Fissure Development and Water Loss (or Stream Pirating) .................... 4
5. MONITORING REQUIREMENTS ........................................................... ............................... 4
6. CONCLUSIONS AND RECOMMENDATIONS ....................................... ............................... 5
List of Figures
(� Figure Description
No.
1 Maximum Subsidence vs Width /Depth for the Foidel Creek Mine
2 Prediction for 1100 ft Deep Panels (1 and Subsequent Panels)
3 Prediction for 1400 ft Deep Panels (1 and Subsequent Panels)
Drawing Description
No.
1 Twentymile Coal, Foidel Creek Mine — Vicinity Map.
2 Twentymile Coal, Foidel Creek Mine — Western Mining District and Surface
Ownership.
3 Twentymile Coal, Foidel Creek Mine — Existing Conditions, February 2008.
4 Twentymile Coal, Foidel Creek Mine — Predicted Post Subsidence Conditions, AVF:
Normal Flow.
5 Twentymile Coal, Foidel Creek Mine — Predicted Post Subsidence Conditions, AVF:
High Flow.
i PN: 2009 -04