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The most significant occurrence of ground water in the region is <br /> associated with the alluvium of the North Fork of the Gunnison River. <br /> Significant thicknesses of alluvial sand and gravel between 30 and <br /> 80 feet exist along the North Fork. Numerous wells are developed in <br /> the alluvium with an average yield of 17.4 gpm. A pumping test <br /> conducted by Bear Coal Company on an alluvial well near the site of <br /> the Bear No. 3 Mine yielded a value of 806.5 gallons/day/foot for <br /> transmissivity. <br /> Three water quality analyses were conducted for the fear No. 3 Mine <br /> on three wells completed in the North Fork alluvium. Two wells <br /> exceeded drinking water standards for total dissolved solids, sodium <br /> and sulfate. The well located closest to the North Fork (the Bear <br /> No. 3 - office well) showed the lowest levels of these constituents. <br /> This is due to the dilution of alluvial ground water by North Fork <br /> River water at this well. <br /> Except for areas in the Minnesota Creek Drainage, the alluvium along <br /> the lower reaches of tributaries to the North Fork is predominantly <br /> thin and confined to discontinuous narrow bands along the stream <br /> courses. The deeply incised channels of these tributaries restrict the <br /> width of the alluvium, while the stream gradient and the presence of <br /> resistant sandstone in the stream channels limit the thickness and <br /> downstream extent of the alluvium. <br /> Occurrences of ground water have been noted in the Mesaverde <br /> Formation based upon information obtained from drilling, experience <br /> in the mines, and from the presence of springs and seeps in the <br /> region. This information also indicates that the only potential regional <br /> bedrock aquifer in the general area is the laterally continuous Rollins <br /> Sandstone. The laterally discontinuous lenticular sandstones within <br /> the Upper Mesaverde Formation support only localized ground water <br /> flows. <br /> Recharge to the Rollins Sandstone occurs along outcrops, along <br /> subcrops beneath stream alluvium and in the channels of the North <br /> Fork and its tributaries. However, due to the steepness of the <br /> topography in the outcrop areas (i.e., sandstones are ledge formers) <br /> and the narrowness of the stream valleys, these local aquifers receive <br /> little recharge. Some recharge to the continuous units and much of <br /> the recharge to the more discontinuous, lenticular units will come <br /> directly from the percolation of snowmelt and precipitation downward <br /> through sandstone lens and along fractures. The same is true in the <br /> Jumbo Mountain area. Of 112 exploration drill holes at the West Elk <br /> Mine that were drilled prior to the mine opening, only three of the <br /> holes produced water from the F Seam at a production rate of 3 gpm <br /> or less. Three other holes in-the Barren member had rates of about <br /> 0.75 gpm. <br /> 24 <br />