2009-09-14_REVISION - C1981019

• Permit No: C1981019
• IBM Index Class Name: Revision
• Doc Date: 9/14/2009
• Doc Name: Proposed Decision & Findings of Compliance
• From: DRMS
• To: Colowyo Coal Company
• Type & Sequence: RN5
• Email Name: JRS
• Media Type: D
• Archive: No

two and one-half years. In 1992, swell factor monitoring and analyses were terminated (Permit
Volume I, Section 4.14.2).
In the South Taylor Pit Colowyo will return all mined lands to approximate original contour,
with reclaimed surfaces resembling the general surface configuration of the area (though changes
will occur on a smaller scale). The Division has, however, granted a variance from AOC for the
steep slopes at the edges of the South Taylor Pit. These steep-slopes will be graded to a more
gently-sloping topography, which will enhance the post-mining land-use of rangeland. These
lands are owned by the Colowyo Land Management Company and the BLM. Both Colowyo and
the BLM have provided letters approving of the post-mining topography and the change in AOC,
located in figure 2.064-1. Maps 18A and 19B show the pre-mining topography and post-mining
topography of the South Taylor Pit, respectively.
Additionally, the removal and redistribution of overburden materials in the South Taylor Pit will
result in these materials expanding in volume approximately 20 percent. This will require
Colowyo to construct two additional valley fills. Colowyo will place the initial box-cut
overburden and interburden in the two valley fills. The valley fills are in the upper forks of
Taylor Creek and are named the West Taylor Fill and the East Taylor Fill. Approximately 60
million cubic yards of material (total) will be placed in these fills. The post-mining topography
for the West Taylor Fill and the East Taylor Fill will be higher than the pre-mining topography.
Drainages in the South Taylor Pit are constructed with gradients similar to those originally
present, and complement the drainage pattern of the surrounding terrain. Pre-mining and
post-mining drainage profiles are found on Map 33B.
Final grading plans for the South Taylor Pit provide a surface that both minimizes erosion and
slippage following the placement of topsoil. Final slopes, in general, do not exceed one vertical
to three horizontal (lv:3h).
Stock tanks of less than two acre-foot in storage capacity and embankments of less than five foot
may be built and retained (following Division approval) to provide for the approved post-mining
land use.
D. Specific Findings Required by Section 4.14
These specific findings are applicable to all areas of the Colowyo Mine including the East Pit,
West Pit, Section 16 Pit and the South Taylor Pit.
1. The Division approved the retention of box cut spoil or initial cut spoil outside the pit area
since the Applicant has demonstrated that such material is not required to achieve approximate
original contour in accordance with Rule 4.09.1 [Rule 4.14.1(2)(d)).
2. The Applicant demonstrated that fill proposed to eliminate the highwall and depressions meets
all the requirements of 4.05, 4.06, 4.09 and 4.15. Therefore, the Division proposes that excess
Proposed Decision and Findings of Compliance 14 September 2009
Permit Renewal 05 Page 56