2013-10-02_PERMIT FILE - C1981019A (3)

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RULE 2 PERMITS 2.04.7 Hydrology Description The objective of this section is to meet the requirements of Rule 2.04.7 et seq. by furnishing hydrological information for the proposed permit revision azea in sufficient detail to describe the following: • Chazacter of surface and groundwater resources; • Baseline groundwater quantity and quality; • Baseline surface water quantity and quality; • Seasonal variations in surface and groundwater quantity and quality; and • Ownership and use of surface and groundwater resources. To meet the requirements of Rule 2.04.7 et seq. both general and detailed groundwater and surface water resource information was collected, compiled, and analyzed. Groundwater resource information will be provided first followed by surface water resource information. 2.04.7 (I) Groundwater Resource Information Both general and detailed information regarding groundwater in the vicinity of the mining areas will be presented in the following subsections. General Groundwater Resource Information General Groundwater Characteristics - Colowyo Coal Company's general area of operation lies within an area known as the Danforth Hills. Regionally, the Danforth Hills are bounded on the northeast by the Axial Basin Anticline, and on the southwest by the northeastern flank of the Piceance Structural Basin. The intensely folded strata of the Mesa Verde Group characterize the Danforth Hills. The groundwater in the general area occurs principally in alluvial material associated with the major stream valleys and to a lesser extent in the permeable and semi-permeable bedrock strata (CDM, 1985a). (The term `alluvial' used in this permit application does not necessarily mean that all the materials in the valley bottom have been water deposited. In fact, the majority of these deposits are colluvial in nature). The principal geologic units in the azea are the Williams Fork Formation, the Iles Formation, and the Mancos Shale. At the top of the Iles Formation is the Trout Creek Sandstone Member The Williams Fork Formation consists of interbedded sandstone, siltstone, and shale with coal beds, and ranges up to 1,200 feet thick in the mine area. The Williams Fork Formation is not considered to be a major aquifer in the region (CDM, 1985a). The Twenty Mile Sandstone Member, which is considered an important aquifer within the. Williams Fork Formation in northern Colorado, is no[ present in the Danforth Hills area (CDM, 1985a). A detailed description of the hydrogeologic units in the area is provided in Section 2.04.6. Groundwater in the bedrock is largely controlled by the existence of fractures instead of primary permeability within the rock strata itself. The low permeability and discontinuous and lenticular nature of the strata restricts the ability of the bedrock to store and transmit water. In addition to fracturing, structural features in the area influence the limited movement and occurrence of groundwater. Groundwater tends to occur in the synclinal axis of the folds in the area as a result of the increased fracturing in these areas and the general movement of groundwater in the down-dip and down-fracture direction (CDM, 1985a). Sou[h Taylor/Lower Wilson -Rule 2, Page 37 Revision Date: 11 /30/06 Revision No.: PR-02