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Ground water information can be found on pages 27 to 41 of Section 2.04 and on pages 114 to <br />138 of Section 2.05.6 of Volume 1. Water quality documentation may be found in Volume 4 and <br />is supplemented by annual hydrologic reports prepazed since 1982. For a description of the <br />ground water hydrology of the mine area and permit revision area and a discussion of the impacts <br />of mining on ground water, please refer to the Hydrologic Balance portion and the Probable <br />Hydrologic Consequences portion of Section B of this Document. <br />Three categories of potential aquifers occur in the general azea. These are alluvial and terrace <br />deposits associated with the North Fork of the Gunnison River, the localized shallow <br />alluvial/colluvial areas in the stream drainages, anti ground water in the lenticular sandstones and <br />the Rollins Sandstone of the Mesaverde Formation. <br />The most significant occurrence of ground water in the general area is associated with the <br />alluvium of the North Fork of the Gunnison River, located approximately two (2) miles southeast <br />of the mine portals and 1,500 feet lower in elevation. Significant alluvial sand and gravel <br />deposits averaging 34 feet thick exist along the North Fork from the mouth of Terror Creek to the <br />confluence of the Gunnison River. There are numerous wells in the area which draw water from <br />this alluvium; well yields range from 5 gpm to 120 gpm, with average yields of approximately 17 <br />gpm (page 31 of Section 2.04.7, Volume 1). <br />Steven's Gulch, an ephemeral stream located in the center of the permit azea, drains an area of 6.0 <br />squaze miles and contains several reaches of shallow alluvium/colluvium. Most of these reaches <br />have little ground water except during periods of stream flow. The most significant area of <br />alluvium/ colluvium occurs in the NW U4 of Section 13, Township 13 South, Range 92 West <br />(Steven's Gulch wellfield), where a 25-foot-thick sandstone outcrop has created a topographic <br />restriction such that a considerable thickness of alluvial sands and colluvial material have been <br />deposited. Test wells drilled by the applicant indicate that the alluvium in this area can support a <br />pumping rate of approximately 28 gpm (Ground Water Hydrology Appendix, Volume 4). The <br />applicant has installed a production well and currently uses this water for domestic use, dust <br />control. and fire control. <br />The rechazge to the Steven's Gulch well field azea is through flow from the adjacent colluvial <br />deposits and from a leaky pipeline aqueduct. The ground water flows through the colluvium <br />downslope to the alluvium, where it becomes trapped or temporazily stored. This situation is <br />somewhat modified by the presence of landslide complexes which occur throughout the general <br />area in the Bowie and five adjoining quadrangles (Colorado Geological Survey Information <br />Series 5, 34p.). <br />Ground water will tend to move down through the more permeable material and along lateral <br />shears of these landslide complexes. The sources of ground water discharges from the Steven's <br />Gulch alluvium at the well field are through the applicant's wells, through underflow within the <br />alluvium down the old bedrock channel of Steven's Gulch, and through discharges to the stream <br />during high water table conditions in spring and early sununer. <br />Water quality analysis for the Steven's Gulch well water indicates good quality water, with none <br />of the parameters exceeding the recommended standards of the U.S. Public Health Service. <br />14 <br />