2025-08-01_PERMIT FILE - C1981019

Home Browse Search

RULE 2 PERMITS South Taylor – Rule 2, Page 12 Revision Date: 7/21/25 Revision No.: MR-267 Near the county line of Moffat and Rio Blanco Counties (which traverses the southern portion of the permit revision area), a small anticline trending northeast is present. This unnamed anticline is an offshoot of the Danforth Hills anticline and Wilson Creek Dome to the south and west. Dips on the south flank of this small anticline are between 3° and 20° to the southeast. This anticline is associated with a small syncline located between it and the Danforth Hills anticline. The synclinal axis is located in the West Fork of the Good Springs Valley. South and west of the permit revision 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 South Taylor area to be uplifted and only the bottom 700 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°. The existing mine and permit revision area are affected on the east by an unnamed syncline that is aligned with the West Fork of Good Spring Creek. This fold has a northeast strike and the western flank of the syncline causes the beds on the east side of the South Taylor and existing mine area to dip to the southeast. These beds increase their dip as the axis of the syncline is approached in the South Taylor area. Exploration Test Borings Exploration test borings have been conducted within the South Taylor mining areas and have been used for the following purposes: Identifying Location of Subsurface Water - Since most of the exploration drill holes were dry, the circulation medium for most exploration drill holes drilled within the mine areas was compressed air with water and foam to lift the cuttings to the surface. Drilling mud was used when heavy fracturing or burn areas were encountered. Several drill holes throughout the area encountered minor amounts of groundwater; however, all of the data obtained to date by Colowyo and the 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 permit area and the variations in the mining techniques (dragline, truck/shovel), 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 twenty (20) percent. Evaluating Geochemical Properties of Overburden - Chemical analyses of overburden and interburden strata in the areas to be mined are provided in Exhibit 6, Item 6. The ongoing overburden sampling program at Colowyo described in Exhibit 6, Item 4 of the existing permit document has confirmed earlier estimates of the geochemical properties of the overburden identified by exploratory drilling. A summary of overburden geochemistry is presented in Table 2.04.6-3 and the relevant borehole locations are shown on Map 11B. This section presents the results and interpretations of geochemical tests performed on overburden material samples from the South Taylor pit area. The purpose of these tests is to determine the chemical composition and assess the acid-forming, toxic-forming, or alkalinity-producing potential of overburden material within the South Taylo pit area. This section describes the methods used in collecting