2020-06-25_REVISION - C1981019 (6)

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RULE 2 PERMITS A dragline will be used for overburden removal over the lower coal seams and the generalized multi-seam dragline sequence at the Colowyo operation is as follows: The dragline will begin the sequence by removing the overburden over the "F6"through the "FA" seams in a single sidecast mode, spoiling the overburden into the previously mined-out pit. The "FB" through the "G8" is removed from the spoil side of the pit. The spoil from the benching operation will be placed to allow the draglines sufficient room and adequate reach to remove overburden while operating on the spoil side. The draglines construct temporary ramps in order to walk to the spoil side. The "F6" overburden is first drilled and blasted, removed by the draglines, "F6" coal is removed behind the advance of the draglines, then the drilling is initiated on the overburden of the "F7" seam. This sequence is typical through the "G8" seam. With the dragline only mining through the F6 and below spoil, it will ensure that any suspect level spoil, based upon the suitability criteria, will stay in the bottom of the pit and will buried by a minimum of 50 foot of suitable Truck Shovel material. Upon complete removal of the overburden over the "G8" seam, the draglines walk around the end of the pit to the next cut to begin removal of the overburden over"F6"coal seam. No Special Handling Procedures will be required for the overburden in the South Taylor pit. The current overburden sampling program that will be used for the East Pit, West Pit, Section 16 Pit and the South Taylor Pit is described within Volume 1, Section 2.05. It was discussed between the Division of Reclamation, Mining and Safety (DRMS) and Colowyo that suspect levels of the Sodium Adsorption Ratio (SAR), Selenium (Se), Boron (B), Saturation % (Sat), and Molybdenum (Mo) need to be addressed in more detail to determine that Special Handling Procedures, that are outside the normal pit operational procedures, will not be needed in the South Taylor pit area. For this purpose, Colowyo will only use the material that is removed and stockpiled by the Truck/Shovel operation to cap the regraded areas. It was also noted through review of Exhibit 6, Item 6, that in the region of the initial boxcut area, no unsuitable material was found in the seam sequence from the F6 coal seam to the G8 coal seam that will be removed by the Truck/Shovel operation. The entire seam sequence from the top overburden through to the bottom G8 seam,which resides in the area of the initial boxcut,will be placed in the valley fill locations;this will allow Colowyo enough spoil room to reach the desired mining depth. In the following analysis, Colowyo has demonstrated that no Truck/Shovel spoil material will exceed the suitability range for overburden criteria as described in Volume 1, section 2.05. This demonstration will be completed by showing the total percentage of unsuitable material in comparison to the total amount of suitable material in the truck/shovel sequence as it relates to the drill hole data shown in Exhibit 6, Item 6. It was discussed with DRMS, that as long as the total percentage does not exceed 15% of the total truck shovel sequence for each drill hole, spoil suitability will not be an issue based upon the overburden seams. Drill Hole 83-D3-06 Unsuitability range in feet of Truck Shovel Sequence: SAR> 15 =N/A Se > 0.3 =6.7 feet B >5.0=N/A Sat<25 or>80=28.5 feet Mo> 1.0= 7.8 feet Total Depth from surface to Bottom of Truck Shovel Sequence (176) = 184.7 feet Total Percentage of each criteria for Truck Shovel Sequence: SAR=N/A South Taylor/Lower Wilson—Rule 2,Page 67 Revision Date: 6/22/20 Revision No.: MR-220