2010-12-17_REVISION - C1981019 (153)

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4 Introduction Groundwater recharge areas are located in the higher elevations to the south where the different geologic units outcrop. Flow proceeds down dip (northeastward) towards the axis of the syncline. Several small springs and seeps have been identified in the drainages of the property; however, none of these represents a significant groundwater discharge area. The Trout Creek Sandstone is considered the uppermost regional aquifer in the area. In the Collom study area, the Trout Creek Sandstone defines a local groundwater basin bounded by its outcrops at the edges of the syncline. In the vicinity of the Collom Mine, the Trout Creek Sandstone is located some 400 to 450 ft below the proposed bottom of the mine (the G coal seams). Preliminary estimates place the potentiometric surface of the Trout Creek Sandstone at approximately 6,800 ft amsl in the vicinity of the Collom Mine. Aquifers of regional extent do not occur within the Williams Fork Formation due to the discontinuous nature of its strata, caused by structural deformation and erosion. In the saturated portion of the section, water levels vary from unit to unit, due to limited vertical movement through the lower conductivity interbeds. Saturated valley fill material also occurs in each of the main drainages including Straight Gulch, Collom Gulch, Little Collom Gulch, and Jubb Creek. Groundwater conditions in the valley fill of each of these drainages were evaluated during the course of this project. 1.3.6 Surface water The proposed operation is located within the watershed of the Yampa River. Individual watersheds within the Collom study area include Straight Gulch, Collom Gulch, Little Collom Gulch, and Jubb Creek (Figure 1.2). Jubb Creek joins Wilson Creek, which eventually flows into the Yampa. The remaining drainages flow into Morgan Gulch before joining the Yampa. The Yampa River flows east to west through the Axial Basin and drains much of the northern plateau region of northwestern Colorado (Utah International, 1982). In general, the surface water courses are narrow channels incised into valley fill within steep -sided erosional valleys. Within the footprint of the proposed Collom Pit, the channels are typically 5 to 20 ft in width and incised about 5 to 10 ft. The stream valleys broaden considerably to the north after the streams pass through the northern limb of the Collom Syncline. 1.4 Work performed As specified in the Work Plan and SAP, WMC developed and implemented a program designed to collect baseline data and other information to support mine permitting, to define the groundwater regime, and to evaluate key hydrologic and environmental issues associated with project development at a pre - feasibility level. Data collection focused on: • Characterization of the groundwater flow regime, including: i - identification of permeable and water - bearing units, - quantification of potentiometric surfaces for each significant unit, 2572 -R2 Colowyo Coal Company Water Management Consultants