2011-06-20_REVISION - C1981019 ‎(5)‎

• Permit No: C1981019
• IBM Index Class Name: Revision
• Doc Date: 6/20/2011
• Doc Name: Revised 5/23/2011 Rule 2
• Type & Sequence: PR3
• Media Type: D
• Archive: No

The temporary spoil pile will be used to fill and recontour the final pit sequence in the final two years of
mining activities (See Map 29C — Temporary Spoil Pile Design). Out of pit stored spoils will be used in
the construction of the post mine topography. Approximately 250 million cubic yards of storage capacity
for the temporary spoil stockpile will be needed.
The toe of the fill will be placed near the floor of the X4 coal seam and the stockpile will eventually
extend upward about 775 feet in thickness to an elevation of 7675. The stockpile will remain in place
until the last few years of mining and will have a life of about 15 -20 years depending on production rates.
Construction of the stockpile is expected to take about 7 to 10 years. As such, the lower portions of the
stockpile will be completed and stabilized before the top is completed. To ensure that a phreatic water
surface does not develop during the life of the stockpile, a rock drain will be installed at the base of the
fill along its entire length. The spoilpile will be confined by the valley slopes on both sides. Volume 20,
Exhibit 23, Item 1 provides the geotechnical report for the temporary spoil pile.
The temporary overburden stockpile will be constructed in 50 to 100 foot lifts by use of trucks, dozers
and loaders. Initially, each lift will be dumped at angle of repose and then subsequently dozed down to an
overall slope of less than 3H:1 V. The side slope of the active dump will not exceed a 33 percent overall
slope and will be maintained during active times of operation (See Map 29C — Temporary Spoil Pile
Design). Maintenance techniques will consist of blading of roads and ramps, along with the use of dust
control during active times of operation. During construction a dozer will be used develop and spread the
end -dumps created by the trucks, this will be the primary method used to build the temporary overburden
stockpile. Sediment control will be implemented to ensure adequate containment of potential runoff
throughout the life of the operation. Temporary seeding via the broadcast method may be employed
during inactive times of operations on the temporary stockpile to reduce the erosion potential utilizing the
following seed mix:
Western wheatgrass @ 4 lbs PLS /Acre
Mountain Brome @ 4 lbs PLS /Acre
Kentucky Bluegrass @ 2 lbs PLS /Acre
Sanfoin @ 2 lbs PLS /Acre
Total 12 lbs PLS /Acre
Following the completion of mining, this temporary overburden stockpile will be removed and placed
back into the open pit. The area that was disturbed in conjunction with this stockpile will be reclaimed in
accordance the procedures outlined in the reclamation plan.
2.05.3 (7) Coal Handling Structures
Please Refer to Volume 1, Section 2.05, Coal Handling Structures and Map 22B.
2.05.3 (8) Coal Mine Waste and Non -Coal Processing Waste
0 Not applicable. Colowyo uses dry crushing facility for coal preparation; no coal processing waste, as
defined in Rule 1.04 "Definitions ", is produced from any part of the mining operations.
Collom — Rule 2, Page 102 Revision Date: 5/20/11
Revision No.: PR -03