2020-06-25_REVISION - C1981019 ‎(6)‎

• Permit No: C1981019
• IBM Index Class Name: Revision
• Doc Date: 6/25/2020
• Doc Name: Proposed Revision Materials
• From: Colowyo Coal Company, LP
• To: DRMS
• Type & Sequence: MR220
• Email Name: ZTT
• Email Name: JDM
• Media Type: D
• Archive: No

RULE 2 PERMITS
the total percentage of unsuitable material as it relates to the drill hole data shown in Volume 17, Exhibit
6 Item 9 for the sources of the majority of overburden to be generated in the area. A review of the
analysis spreadsheet for drill hole C-04-04 shows that the source of all elevated SAR levels (> 15.0)
originates from the bottom 121 feet of overburden from the bore hole. Normal overburden haulage and
sequencing will ensure this material will not contribute to elevated SAR levels on the reclaimed surface
post-mining in the Collom expansion area.
Drill Hole C-04-14
Unsuitability range in feet:
SAR> 15 =27.6 feet
Se > 0.3 = 7.3 feet
B >5.0=0 feet
Sat<25 or>80=45.35 feet
Mo> 1.0= 0feet
Total Drill Hole Depth= 354.3 feet
Total Percentage of unsuitable material:
SAR=27.6 feet/354.3 feet= 7.7900084674%
Se = 7.3 feet/354.3 feet=2.0606007903%
B =N/A
Sat=45.35 feet/354.3 feet= 12.799887101%
Mo=N/A
Drill Hole C-04-25
Unsuitability range in feet:
SAR> 15 = 69.6 feet
Se > 0.3 = 15.15 feet
B >5.0=0 feet
Sat<25 or>80= 83.8 feet
Mo> 1.0= 0feet
Total Drill Hole Depth= 639.7 feet
Total Percentage of unsuitable material:
SAR=69.6 feet/639.7 feet= 10.880100047%
Se= 15.15 feet/639.7 feet=2.3682976395%
B =N/A
Sat= 83.8 feet/639.7 feet= 13.099890574%
Mo=N/A
Drill Hole C-04-04
Unsuitability range in feet:
SAR> 15 = 111.2 feet
Se > 0.3 =0feet
B >5.0=0 feet
Sat<25 or>80=68.3 feet
Mo> 1.0= 0feet
Total Drill Hole Depth= 663.3 feet
Total Percentage of unsuitable material:
SAR= 111.2 feet/663.3 feet= 16.764661541%
Se =N/A
Collom-Rule 2,Page 78 Revision Date: 6/22/20
Revision No.: MR-220