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<br />o <br />N <br />~ <br />o <br /> <br />Page 6 <br /> <br />4. <br /> <br />Groundwater moves down structure within the relatively highly permeable Leadville <br />Limestone. As groundwater descends, water temperature increases due to a slightly <br />enhanced geothermal gradient. <br /> <br />" <br /> <br />4a. Alternately, as groundwater moves down the complex structures, it comes in contact with <br />salt units of the Eagle Valley Evaporites. Due both to the relatively low initial TDS and <br />the elevated temperature, salt is easily dissolved, increasing the TDS significantly. <br /> <br />5. In the vicinity of Glenwood Springs, the heated saline groundwater encounters vertical <br />access to the surface. This access is probably both shallower portions of the Leadville <br />Limestone as well as near vertical faults which enhance an already high hydraulic <br />conductivity. The driving head on the groundwater is probably a combination of <br />elevation head (elevation of the recharge area) and thermal expansion due to heating. <br /> <br />6. As the groundwater nears the surface, several things occur: <br /> <br />a. Portions of the flow encounter confining layers within the Leadville and the <br />Belden Shale and can only reach the surface via wells. <br /> <br />b. Where the Leadville is more leaky (due to faulting/fracturing) or the Belden Shale <br />does not exist, thermal water escapes upward into the alluvium, as springs, seeps, <br />or diffuse flow into the river. <br /> <br />c. In still other areas, such as the Yampa Spring, the thermal groundwater simply <br />escapes from near the exposed edge of the Leadville. <br /> <br />7. The range of observed spring temperature and salinity is a function of the amount of <br />mixing between Leadville water and cold alluvial water in the near surface. <br /> <br />Michael J. Galloway <br />Consul/lng Hydrogeologlst <br /> <br />ProjecllOI6 <br />