2020-03-24_PERMIT FILE - C1981019A (5)

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RULE 2 PERMITS Summary of Groundwater Conditions The coal beds of the Williams Fork Formation that are to be mined are at a high elevation and are truncated by the mining operation to the north, Goodspring Creek to the east and Taylor Creek to the west. As a result, the coals and upper sandstones are drained. Perched aquifers exist in the coals and sandstones, but exhibit little lateral or vertical continuity. Cascading waters from perched zones were encountered during drilling of exploration holes on the lease. No substantial quantities of water were encountered through the mine section or in the sandstones below the coals that are to be mined. The Trout Creek Sandstone of the Iles Formation is the first major, regional aquifer that can be recognized on the mine property. The sandstone occurs approximately 800 feet beneath the lowest coals to be surface mined. The geologic characteristics of the Williams Fork and Iles Formations appear to demonstrate natural low porosity and permeability that is enhanced locally by fracturing. Since most of the beds in the Williams Fork are not laterally extensive, and due to the relatively low yielding characteristics, the Williams Fork in this area can not be considered to be a significant aquifer. The groundwater quality has been shown to be of poor quality and is variable from site to site. A study conducted in 1974 and 1975 revealed that the specific conductance of the groundwater averaged 1390 mmhos and ranged 720 to 2700 mmhos. The results of a 1979 study conducted by Leonard Rice Consulting Water Engineers show that overall quality has not been significantly affected by mining activities. The report stated that measurements made in 1979 were within the range of variation seen in 1974 and 1975, though they were in general lower than the historical data. The most probable explanation of this apparent increase in water quality may be a dilution effect from the relatively high runoff throughout the spring and summer of 1979. The report stated that there is no evidence of contamination of the groundwater by the surface mining of Colowyo Coal Company.Additional monitoring of the Goodspring Creek alluvium/colluvium and downdip of the Gossard Loadout also indicates groundwater quality has not been significantly affected by mining activities. Surface Water Occurrence of Surface Water General Area The surface water of the general area is characteristic of a high altitude environment. The climate is semi-arid, characterized by low precipitation, large daily temperature changes, low humidity, moderate winds and abundant sunshine. Precipitation averages 21.5 inches across the drainages in the "general area"per year resulting in erratic and low flows in the major drainages near the mine area. Climatic data is discussed in detail in Section 2.04.8. Surface flows are dominated by the occurrence of runoff events resulting from either snowfall or rainfall. Snowfall derived runoff dominates the hydiulugic cycle, supplemented by periodic intense thunderstorms which result in Rule 2 Permits 2.04-20 Revision Date: 12/20/19 Revision No.: TR-135