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<br />Page 2 <br /> <br />2.0 SITE HYDROGEOLOGY <br /> <br />o <br />N <br />W <br />0) <br /> <br />2.1 DESCRIPTION <br /> <br />2.1.1 Geolo~y <br /> <br />Glenwood Springs, located at the confluence of the Colorado and Roaring Fork rivers, is <br />underlain by a faulted and folded sequence of Pennsylvanian, Mississippian, and Devonian rocks <br />(Figures 1 and 2). In general, the Pennsylvanian units range from sandstone to shale (Maroon <br />and Belden formations), and considerable thicknesses of evaporite sequences (Eagle Valley <br />Evaporite). The Mississippian unit is a massive limestone (Leadville Limestone), and the <br />Devonian units are dolomites and shales (Dyer and Parting formations). The bedrock units are <br />overlain by 55 to 80 feet of alluvium (URS, 1982). <br /> <br />Several faults have either been mapped at the surface, postulated, or identified in the subsurface. <br />The faulting of the rock units described above, has resulted in a keystone fault block beneath <br />Glenwood Springs (Geldon, 1985) (Figure 2). The same rock sequence occurs within and <br />adjacent to the fault block, at least within the upper few thousand feet. <br /> <br />2.1.2 Hydrology <br /> <br />The primary bedrock aquifer beneath Glenwood Springs is the Leadville Limestone. <br />Groundwater in the Leadville is confined by some combination of the Belden Shale, lower <br />permeability sequences within the Leadville, and possibly alluvium. Leadville groundwater is <br />a sodium-chloride water (20-21,000 mg/l TDS) ata maximum observed temperature of 50-51 <br />degrees C (122-124 degrees F). <br /> <br />Michael J. GaJJoway <br />Consulting Hydrogeologlsl <br /> <br />Project 1016 <br />