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P <br />fill. The three samples to date indicate that the water quality fluctuates <br />seasonally in response to the river. Total dissolved solids concentration <br />a increase during the snowmelt season. The well completed in the fill usually <br />has double the total dissolved solids concentrations though no down-valley <br />gradient is discernible. <br />The North Fork of the Gunnison River has downcut through the almost <br />level sedimentary strata including the entire geologic sequence from the <br />Ohio Creek Conglomerate Formation to the Mancos Shale Formation. The <br />strata crops out in elongated bands which form an eastward pointing U- <br />shaped pattern intersecting the river on the point of the V. The strata <br />subcrops into the alluvial aquifer at these points: If any of the strata <br />have primary permeability (interstitial pore space) or secondary per- <br />meabi]ity (fracture space) then water would flow from the alluvial aquifer <br />~~ into the strata: Water level would tend to be similar in elevation to the <br />river. <br />The Mancos Shale Form ation outcrops downstream of the permit are near <br />Somerset (Johnson 1948). Shale does not have primary permeability and <br />little secondary permeability. If water is present, it has high total <br />dissolved solids (U.S. Department of Interior 1978). <br />The Mesaverde Formation outcrops just upstream of the town of Somerset <br />(Johnson 1948). Sandstone is usually assumed to have primary permeability. <br />However, the sandstones of the Mesaverde Formation are very well cemented <br />and the interstitial pore space is greatly reduced due to the cement bet- <br />we~n sand grains (Bowman 1980). Therefore, most wells into the sandstones <br />yield less than 10 gpm unless a fracture zone with secondary permeability <br />2.04-22 <br />~.. <br />,. <br />_:~......,_..,_::~.::,..i,~. <br />