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Under Rule 2.07.6(2)(c),the Division is required to make an assessment of the <br /> probable cumulative impacts of all anticipated coal mining in the general area on <br /> the hydrologic balance and to make a finding (as discussed in Section A of this <br /> document)that the operations proposed in the permit application have been <br /> designed to prevent material damage to the hydrologic balance outside of the <br /> proposed permit area. This section of the findings document is divided into the <br /> following subsections: Description of the Hydrologic Environment, Probable <br /> Hydrologic Consequences of the West Elk Mine, and Summary and Findings. A <br /> separate Cumulative Hydrologic Impact Assessment (CHIA) is available for <br /> review at the Division of Reclamation, Mining and Safety. The CHIA, filed at the <br /> Division office, assesses the projected cumulative hydrologic impacts of all <br /> anticipated mining operations in the general area of the West Elk Mine on the <br /> North Fork of the Gunnison River Valley. <br /> 1. Description of the Hydrologic Environment <br /> a. Regional Geology <br /> For information regarding regional geology, see Section A, Description <br /> of the Environment, Geology in this Findings Document. <br /> b. Groundwater <br /> Seven categories of potential aquifers occur in the Somerset Coal Field. <br /> These are: 1)the alluvial and terrace deposits associated with the North <br /> Fork of the Gunnison River; 2) the localized, shallow alluvium along <br /> creeks tributary to the North Fork; 3)the discontinuous, lenticular and <br /> laminar sandstones of the Mesaverde Formation; 4) the Rollins <br /> Sandstone; 5) the coal seams; 6) shallow colluvial surficial deposits; and <br /> 7) fracture zones in bedrock. <br /> The most laterally continuous sandstone units in the region are the <br /> Rollins Sandstone and the massive sandstone separating the Upper and <br /> Lower Coal Members of the Mesaverde Formation, known as the Bowie <br /> Sandstone. The Rollins crops out in the South of Divide area, <br /> approximately one mile upgradient from the West Elk Mine's <br /> underground workings. In the Jumbo Mountain area, the Rollins <br /> Sandstone appears to be hydraulically isolated. To the south and west, <br /> the Rollins Sandstone crops out in cliffs. In the Jumbo Mountain area, <br /> the average interburden thickness between the B Seam and the Rollins <br /> Sandstone is 150 feet. <br /> The Rollins Sandstone has been considered a hydrostratigraphic unit of <br /> potential regional importance, because of its wide areal extent in the <br /> southeastern Piceance Basin. The Rollins is a poor quality aquifer due to <br /> its low permeability and poor water quality. A pump test of the Rollins <br /> Sandstone near the West Elk Mine yielded 3 gallons per minute. <br /> Drillholes in the Rollins in the vicinity of the Bowie#1 Mine did not <br /> 37 <br />