2020-03-24_PERMIT FILE - C1981019A (2)

Home Browse Search

RULE 2 PERMITS Springs that have a potential to be impacted by mining activities include 3-93-17-142, 3-93-17-432 (Taylor Creek), WFS-1 and -lA, WFS-2, WFS-4, WFS-5, and WFS-7 (West Fork Good Spring Creek), and GSCS-1 (Good Spring Creek). Springs that will be eliminated by the South Taylor pit include 3-93- 20-212 and 3-93-17-432 (Taylor Creek), 3-93-20-213, and 3-93-20-214 (West Fork Good Spring Creek). The FW source is an artesian well completed in the Trout Creek Sandstone that flows through a cracked wellhead and not a natural water discharge point. Table 2.05.6-1 lists the springs found in the vicinity of the South Taylor mining area. The locations of the investigated springs and seeps are presented on Map 10. The elevations of the springs were compared to the elevation of the confined groundwater of the Williams Fork Formation in well 84 -0 -OB. The water level in this well was 7,054 feet above mean sea level in October 1984 (CDM 1985a). Of the base flow springs, GSCS-1, WFS-2, and WFS-2A are below this elevation and may result from confined groundwater recharge from the Williams Fork Formation. Data collected for the springs contributing to the base flow of the surface water system and that have a potential to be impacted by mining are summarized in Table 2.05.6-2. During peak flow, typically April or May, seven springs contribute a combined approximately 130 gallons per minute (gpm) [equivalent to 0.3 cubic feet per second (cfs)] into the West Fork Good Spring Creek. About 20 gpm (0.04 cfs) is contributed during base flow periods. Potential Impacts to Bedrock Groundwater Quantity No impacts are anticipated to the quantity of groundwater in the Williams Fork Formation or the Trout Creek Sandstone of the Iles Formation. Drilling and mining by Colowyo in the area identified very limited perched water, and no saturated conditions, in the Williams Fork Formation. In the Williams Fork Formation, the low permeability and depositional nature of the strata restrict the ability of the bedrock to store and transmit water. There are no continuous non -coal beds in the Danforth Hills. Groundwater movement is mainly controlled by fractures of varying orientation. The Williams Fork Formation is not a significant water supply source in the Danforth Hills. It is not used as a source of water where the alluvial and surface waters are accessible. Where wells yield water, the water quality in the Williams Fork Formation is generally good. Very few registered wells for domestic, agricultural, or industrial purposes are completed in the Williams Fork Formation in the vicinity of the South Taylor pit. Drilling by Colowyo and other parties encountered no significant water in the South Taylor pit area in the litholgic sequence which is planned to mined. This is based on the drilling and geophysical logs. It should be noted that the current East and West Pits at the Colowyo Mine do not intersect any significant aquifers. Perched aquifers have been encountered which drain rapidly. Once drained, they do not produce any significant water to the current pits. Since the South Taylor pit is higher in elevation than the two current pits, and also up dip of the current pits, no significant aquifers should be encountered in this pit. The Trout Creek Sandstone aquifer is separated from the lowest coal seam (G8) to be mined by approximately 590 feet in the South Taylor pit area. Between this coal seam and the Trout Creek Sandstone is a mudstone/shale, sandstone, siltstone, and coal sequence of the Williams Fork Formation. About 165 feet above the Trout Creek Sandstone, a two -foot thick smectite clay layer (known as the Km bed) exists that is found throughout the Danforth Hills area. This layer has low permeability and therefore would be an additional impediment to downward or upward groundwater flow. South Taylor/Lower Wilson — Rule 2, Page 80 Revision Date: 4/7/17 Revision No.: RN -07