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<br />• CHARACTERIZATION OF THE ROLLINS SANDSTONE "AQUIFER' <br />ASSOCIATED WITH THE JUMBO MOUNTAIN TRACT <br />999 <br />1.0 INTRODUCTION <br />On July 5, 1994, the Colorado Division of Minerals and Geology (CDMG) provided a preliminary adequacy letter <br />to Mountain Coal Company's (MCC) responses dated May 23, 1993 regarding Permit Revision N5; West Elk Mine; <br />Permit No. C-80-007. One of the outstanding issues regarded the requirements to define the nature, extent, and <br />hydraulic characteristics of each aquifer above, within and, if potentially impacted, below the lowest coal seam <br />to be mined as stated in 2.04.7 (11, 131 and (41 Hydrology Description in the Colorado Regulations. <br />Concerns in this adequacy letter included: <br />• the indication that springs emanating through the colluvium would not be very useful for identifying <br />impact to the hydrologic regime especially the B-Seam and Rollins Sandstone Units. <br />• the need to develop piezometric surfaces for the B-seam and Rollins Sandstone which presents not only <br />the elevation of the formation water but also the direction of flow. This would assist the Division in <br />• estimating the potential for impacts to the hydrologic regime. <br />To respond to these requirements, MCC has re-evaluated these units to determine it: <br />A) based on the nature and extent of these units are these considered significant as aquifers, locally or <br />regionally; and <br />BI based on the chemistry of groundwater within these units determine if the springs are points of discharge <br />for these units. <br />The following presents the results of this evaluation. <br />2.0 NATURE AND EXTENT <br />The two hydrologic units of concern are the B-Seam and the Rollins Sandstone. The nature and extent oT these <br />hydrogeologic units are described as follows: <br />B -Seam -The stratigraphy of the B-Seam is well described in the Permit Revision as well as in the Wes[ Elk <br />Permit Application. It is the lowest minable seam on the property and typically comprised of three coal benches <br />• 1 <br />