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Water Replacement Plan <br />12/21/83 <br />•~_. Page Three <br />Streams <br />All but major streams in the area are of intermittent or ephemeral character. <br />The monitoring information is contained within the specific basin data. The <br />description of each stream is contained within that specific basin information. <br />For more information on the surface hydrology of the area, please see Section <br />2.04.7 of the Orchard Valley F1ine Underground Mining and Reclamation Permit. <br />GROUNDWATER HYDROLOGY <br />The three categories of potential aquifers within the area are: <br />1. North Fork of the Gunnison River alluvium and its associated terrace <br />deposits. <br />2. Localized shallow alluvial areas in drainage basins. <br />3. Groundwater in the Mesa Verde formation. <br />The most important alluvium in the mine operation area is that of the North fork <br />of the Gunnison River, which, at its closest point is approximately two miles <br />from the mine mouth and 1500 ft. lower in elevation. <br />Significant amounts of sand and gravel alluvium exist along the North Fork of the <br />Gunnison from the mouth of Terror Creek to the confluence of the Gunnison River, <br />Because of its location, the North Fork of the Gunnison River alluvium will be <br />not be impacted by underground mining. For more information, see Section <br />2.04.7(1)(a) Orchard Valley Mine Underground Mining and Reclamation Permit. <br />Generally, because of the geomorphology of the area, the streams within the area <br />have very shallow alluvium and little groundwater except during periods of stream <br />flow. Each stream alluvium will be described in detail within the specific <br />information. <br />The Orchard Valley Mine is located on an outcrop of the Mesaverde formation, <br />which is a thick series of interbed sandstones and shales which form the middle <br />slopes of the hillside north of the North Fork of the Gunnison River. Strati- <br />graphically, the Mesaverde formation is above the Mancos shale and below the <br />Wasatch formation. Colorado W=_stmoreland Inc. has undertaken an extensive core <br />hole drilling progrzm in the area for the purpose of developing bedrock ground- <br />water information. Because of the dip of the Mesaverde forration and the collu- <br />vial sources of the springs within the area, it has been determined that the <br />colluvial springs are not part of a deep aquifer system. N.ore information may be <br />found in Section 2.04.7(1)(a) Orchard Valley Mine Underground Mining and Reclama- <br />tion Permit and United States Geological Survey Water Resources, Investigation <br />Report B3-4069. <br />L J <br />