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<br />C\1 <br />- <br />r-- <br /> <br />'-, <br /> <br />~, <br />'-- <br /> <br />. ~ -. <br />._;~',,~,'~ <br /> <br />130,000 tons/year (TDY) of TDS to the Colorado River, with 45 percent <br />from surface springs, This figure was based upon a mean salinity <br />concentration of 9,295 mg/l. The Glenwood saline springs (mean TDS, <br />18,648 mg/l) contribute approximately 310,000 TPY to the Colorado <br />River, with 55 percent from surface springs, The saline springs at <br />South Canyon, west of Glenwood Springs, contribute only 250 TPY of <br />salinity to the Colorado River. Their mean salinity concentration is <br />776 mg/l. <br /> <br />A hypothesis was developed during the PIQ to describe the physical and <br />chemical processes at work in the Glenwood-Dotsero Springs study area. <br />The saline springs exhibit high rates of flow and issue from solution <br />widened joints, bedding planes, and fractures in the Leadville <br />Limestone. The springs occur where the Leadville Limestone outcrops at <br />river level and specific locations are probably fault and/or fracture <br />controlled. The source of the sodium and chloride ions is dissolution <br />of halite and gypsum/anhydrite beds located in the Eagle Valley <br />Evaporite by circulating meteoric water. The elevated temperatures <br />(Dotsero, 85 degrees F; Glenwood, 107 degrees F) may result from deep <br />circulation through normal geothermal gradient or from the presence of <br />an elevated geothermal gradient as evidenced by recent volcanic <br />activity and the presence of other thermal springs and wells in the <br />vicinity. The Dotsero Crater is the most recent volcanic activity in <br />Colorado (about 4150 years old). Recharge areas for the circulating <br />water are likely to be located either to the northeast or to the south <br />of the springs. This recharge water probably infiltrates downward <br />around deep faults or volcanic necks. The saline springs at South <br />Canyon have as their source the Dakota Sandstone. <br /> <br />Field verification studies were then undertaken to provide further <br />quantification of the subsurface saline spring input in the study area. <br />No new point source springs were identified but areas of subsurface <br />input were better delineated. The verification results indicated a <br />larger unmeasured input at Glenwood Springs than the PIQ (192,000 TPY <br />versus 136,000 TPY). However, the comparisons are reasonably close, <br />given the data limitations and the fact that the verification studies <br />represented loading during a small portion of one year, while the PIQ <br />used gaging station data for a number of years. These studies <br />indicated that surface collection could be accomplished by pumping the <br />areas of saturated river alluvium or by pumping in bedrock. <br /> <br />An appraisal level design, environmental assessment, and preliminary <br />determination of socioeconomic impacts were performed on each of the <br />seven viable alternatives previously identified. The appraisal level <br />design was defined as containing a degree of detail necessary to permit <br />confident assessment of the feasibility and cost of the alternative <br />plans and ultimately allow a comparative evaluation of alternatives for <br />determination of a preferred plan. The environmental and social <br />assessments were carried out to a similar level. <br /> <br />Hi <br />