2010-12-17_REVISION - C1981019 ‎(153)‎

• Permit No: C1981019
• IBM Index Class Name: REVISION
• Doc Date: 12/17/2010
• Doc Name: Exhibit 7 Item 21 Collom Project Pre-Feasibility Hdyrology Report
• Type & Sequence: PR3
• Email Name: JRS
• Media Type: D
• Archive: No

Contents
6 SLOPE DEPRESSURIZATION MODEL 77
6.1 General 77
6.2 Basis for model 77
6.3 Highwall model 79
6.4 Advancing wall model 81
6.5 Sidewall model 82
6.6 Summary and conclusions 84
7
MINE WATER MANAGEMENT
85
7.1 Requirements for dewatering
85
7.2 Conceptual dewatering design for Option 1 (north to south mine plan)
86
7.3 Conceptual dewatering design for Option 2 (south to north mine plan)
93
8
CONSIDERATIONS FOR FEASIBILITY AND PERMITTING
99
8.1 Feasibility considerations
99
8.2 Permitting considerations
101
9
REFERENCES
103
TABLES
3.1
Precipitation period of record and missing data
14
3.2
Precipitation data summary
15
3.3
Storm precipitation amounts for the Collom Pit area
16
4.1
Stream inventory summary
20
4.2
Surface water quality summary
25
4.3
Spring and seep inventory
29
4.4
Spring water quality summary
34
5.1
Summary of pre- existing wells
46
5.2
Bedrock baseline monitoring well details
49
5.3
Valley fill monitoring well details
49
5.4
Bedrock standpipe piezometer details
51
5.5
Vibrating wire piezometer details
52
5.6
Hydraulic parameters
55
5.7
Summary of measured hydraulic conductivities
61
5.8
Summary of bedrock groundwater quality
65
5.9
Summary of valley fill groundwater quality
66
6.1
Model parameters
78
7.1
Schedule for Phase 1 mine
87
7.2
Schedule for Phase 2 mine
88
7.3
Dewatering well schedule for Phase 1 of Option 1 mine plan
91
7.4
Summary of estimated dewatering rate
92
7.5
Dewatering well schedule for Option 2 mine plan
95
7.6
Summary of estimated dewatering rate
97
2572 -R2
Colowyo Coal Company
Water Management Consultants