2005-04-08_GENERAL DOCUMENTS - C1980007

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K. Probable Hydrologic Consequences Under Rule 2.07.6(2)(c), the Division is required to make an assessment of the probable cumulative impacts of all anticipated coal mining in the general area, on the hydrologic balance and to make a finding (as discussed in Section A of this document) that the operations proposed in the permit application have been designed to prevent material damage to the hydrologic balance outside of the proposed permit area. This section of the findings document is divided into the following subsections: Description of the Hydrologic Environment, Probable Hydrologic Consequences of the West Elk Mine, and Summary and Findings. A separate Cumulative Hydrologic Impact Study (CHIS) is available for review at the Division of Minerals and Geology. The Cumulative Hydrologic Impact Study (CHIS) filed at the DMG office assesses the projected cumulative hydrologic impacts of all anticipated mining operations in the general azea of the West Elk Mine on the North Fork of the Gunnison River Valley. I. Description of the Hydrologic Environment a. Regional Geology For information regarding regional geology, see Section A, Description of the Environment, Geology in this Findings Document. b. Groundwater Seven categories of potential aquifers occur in the Somerset Coal Field. These aze: 1) the alluvial and terrace deposits associated with the North Fork of the Gunnison River; 2) the localized, shallow alluvium along creeks tributary to the North Fork; 3}the discontinuous, lenticulaz and laminar sandstones of the Mesaverde Formation; 4) the Rollins Sandstone; 5) the coal seam; 6) shallow colluvial surficial deposits; and 7) fracture zones in bedrock. The most continuous sandstone units of any significance in the region aze the Rollins Sandstone and the massive sandstone sepazating the Upper and Lower Coal Members of the Mesaverde Formation -the Bowie sandstone. The Rollins Sandstone has been considered an aquifer of potential regional importance, because of its areal extent and potential yielding capability. However, available data indicate that the Rollins is a marginal aquifer in terms of yield and water quality. One pumping test conducted on the Rollins sandstone in the vicinity of the mine indicates that the formation was capable of producing only approximately 3 gpm. This is further documented in the vicinity of the Orchard Valley Mine where it is reported that drill holes which penetrated the Rollins Sandstone had an insufficient yield to sustain groundwater supply wells. Furthermore, the Rollins sandstone crops out a only several miles upgradient of the West Elk Mine site, so the recharge area is very limited. 45