2017-03-20_PERMIT FILE - C1981019A

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RULE 2 PERMITS The axis of the Collom syncline is approximately parallel with the Axial Basin anticline and as previously mentioned passes through the northern portion of the Collom permit expansion area. Bedding orientation, as measured on surface outcrops, has a strike of around North (N) 70° West (W). Dips on the shared limb with the Axial Basin anticline can exceed 450, but are normally between 25° and 35° and dip to the south. The south flank of the syncline has dips between 50 and 20° to the north (Map 7A). South and east of the Collom permit expansion area is the Wilson Creek Dome, part of the Danforth Hills anticline. A producing petroleum reserve, the dome is capped by the Iles Formation. This uplift has caused the Lower Wilson area to be uplifted and only the bottom 750 feet of the Williams Fork is present. The beds in this area have a strike to the northwest with dips to the northeast of approximately 7°. Two nearly vertical joint sets have been identified in the Williams fork formation in the Collom permit area. The primary joint system has a strike ranging between N55°W and N60°W. The secondary joint system has a strike of N 19°East (E). No faults have been identified in theCollom permit area. These was accomplished by examining the geologic cross setions in and around the proposed Collom pit area and looking for any potential large offsets between drill holes. In addition, any available downhole geophysical logs from the drill holes used in the cross sections, and adjacent holes to the cross sections, were examined for any repeats in the logs or missing coal sections while the Colowyo drill hole database was prepared. In addition, field work examined many of the sandstone exposures and no evidence of faulting in the proposed Collom pit area has not been found. In addition, the Collom permit area location on the southern limb of the Collom syncline is similar to the current location of the Colowyo active mining area, east of the Collom pit. During the nearly 40 years of mining in the current mining area, no faulting has been noted during the extraction of the coal. Thus, since the geologic conditions in the Collom area are similar to the current mining area, no faults should be expected to be found either. Exploration Test Borings Exploration test borings have been conducted within the Collom mining area and have been used for the following purposes: Identifying Location of Subsurface Water - Several drill holes throughout the area encountered minor amounts of groundwater; however, all of the data obtained to date by Colowyo and the United States Geological Survey (USGS) have indicated that groundwater occurrences in the Williams Fork Formation in the area are not continuous but rather are a series of perched systems of limited lateral and vertical extent. Information on groundwater occurrence is provided in section 2.04.7. Characterizing Physical Properties of the Overburden - The overburden material, which is removed as a part of the mining operation, consists mainly of mudstones, siltstones, and sandstones. Generally, the mudstones will have a relatively high erodibility and compaction factor, while sandstones and siltstones will have low erodibility factors and low to moderate compaction. Because of the variable lithology and lenticular nature of the strata in the Collom permit expansion area and the variations in the mining techniques, it is difficult to determine an actual value for the swell of the overburden; therefore, the overall swell of the overburden material was estimated to be approximately 20 percent. Evaluating Geochemical Properties of Overburden - Exploration holes were located in the proposed mining area for evaluation of the coal resources in the Collom proposed mining area during the 2004 — 2006 geologic study, The hole selection for collection of the overburden and interburden rock for physio- Collom — Rule 2, Page 15 Revision Date: 3/31/16 Revision No.: PR -04