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<br />Page 3 <br /> <br /><::> <br />N Confinement of the Leadville is imperfect, due either to faulting or variations in lithology, as <br />W <br />a,J evidenced by the numerous natural springs and seeps along the Colorado River (Figure 3). <br />Water level measurements in two wells completed within the Leadville indicate that the elevation <br />head within the Leadville is about 5740 feet above mean sea level, however, heads have been <br />observed to vary annually by as much as 3 feet (Galloway, 1985). In addition to the numerous <br />identified springs, the Bureau has speculated that as much as 50 % of the total flow from the <br />Leadville may be entering the Colorado River undetected through the alluvium, based on salinity <br />studies along this reach of the river. <br /> <br />Given the large flow to the surface at Glenwood Springs (estimated to be 9-10,000 gpm), the <br />observed elevation head of 5740 feet represents a minimum head, since the aquifer is under <br />discharge conditions and not fully confined. There is evidence in the Glenwood Springs area <br />that thermal springs have existed in this area for thousands of years with higher apparent heads. <br />Extensive travertine within the alluvial deposits along the river at an elevation of 6000 feet <br />indicate both a higher head and different chemical and temperature regimes. Travertine is not <br />being deposited by the current geothermal system. <br /> <br />The Leadville aquifer beneath Glenwood Springs is extremely "stiff" hydraulically. The term <br />"stiff" is used to describe an aquifer which has very high transmissivity but low storativity. As <br />a result of these hydrologic characteristics, almost any stress produces a hydraulic response <br />which very quickly propagates over long distances. A familiar example of a "stiff' hydraulic <br />system is when in a poorly constructed hotel, a toilet flush down the hall results in an immediate <br />pressure drop in your shower. In addition to responding to discharge from a well, as during the <br />various aquifer tests, this aquifer responds to a variety of subtle stresses, including barometric <br />pressure changes, diurnal earth tides, and heavy vehicles (such as trains) (Galloway, 1982). <br />This "stiff' response is indicative of aquifers with high transmissivity and low storativity. <br /> <br />The results of two long-term, multi-well, aquifer tests performed during 1982 and 1984 are <br /> <br />Mb:hae/ J. Ganaway <br />ConsuIJlng Hydrage%glst <br /> <br />Project 1016 <br />