2010-12-17_REVISION - C1981019 ‎(127)‎

• Permit No: C1981019
• IBM Index Class Name: REVISION
• Doc Date: 12/17/2010
• Doc Name: Exhibit 7 Item 21 Collom Project Part 2
• Type & Sequence: PR3
• Email Name: JRS
• Media Type: D
• Archive: No

92 Mine water management
i
7.2.3 Summary of dewatering, estimates
Table 7.4 summarizes the empirically derived average dewatering rate estimates for the
proposed Collom Phase 1 box cut area. These estimates may vary depending on the
detailed mine plan and mining rate. As the mine advances up -dip to the south, it will
eventually rise above the water table and dewatering wells will not be needed. There
will likely still be seepage from perched groundwater zones into the pit walls similar to
that which occurs at the existing Colowyo Mine.
Table 7.4 Summary of estimated dewatering rate
Dewatering installation
Estimated production rate
C 7.2.4 Water balance and water management considerations
An estimate of the average water balance for the Collom Phase 1 box cut has been
prepared. This balance will change as the mining progresses up -dip to the south and
dewatering rates decrease.
Water from the dewatering system is categorized as non - contact discharge that comes
directly from the wells, and contact discharge, that comes from in -pit drains and sumps.
The contact water may have its quality affected by the mine operation. Upstream
surface water diversions are not included as a source of water in the water balance.
The components of water use include potable water and dust control. The total amount
of water available and the consumptive use will be variable depending on mining
demands and seasonal requirements.
The Collom Phase 1 box cut water balance data indicate the following:
Water available
Total non - contact water: 150 to 285 gpm
Total contact water: 90 to 380 gpm
Water used
Potable water 5 to 10 gpm
Water for dust control: 400 to 600 gpm
Maximum surplus: 275 gpm
( Maximum makeup 420 gpm
2572 -R2
Colowyo Coal Company
Water Management Consultants
(gpm)
Highwall wells (HW -1 to 5)
50 to 75
Sidewall wells (SW -1 to 6)
60 to 90
Other wells (number varies with mining)
40 to 120
Horizontal drains
20 to 80
Vertical drains
20 to 100
In -pit sumps
50 to 200
Total
240 to 665
C 7.2.4 Water balance and water management considerations
An estimate of the average water balance for the Collom Phase 1 box cut has been
prepared. This balance will change as the mining progresses up -dip to the south and
dewatering rates decrease.
Water from the dewatering system is categorized as non - contact discharge that comes
directly from the wells, and contact discharge, that comes from in -pit drains and sumps.
The contact water may have its quality affected by the mine operation. Upstream
surface water diversions are not included as a source of water in the water balance.
The components of water use include potable water and dust control. The total amount
of water available and the consumptive use will be variable depending on mining
demands and seasonal requirements.
The Collom Phase 1 box cut water balance data indicate the following:
Water available
Total non - contact water: 150 to 285 gpm
Total contact water: 90 to 380 gpm
Water used
Potable water 5 to 10 gpm
Water for dust control: 400 to 600 gpm
Maximum surplus: 275 gpm
( Maximum makeup 420 gpm
2572 -R2
Colowyo Coal Company
Water Management Consultants