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<br /> <br />small as to be unmeasurable. <br />In contrast, overburden materials in C-22676 east and <br />west tracts would be removed and replaced by a truck- <br />shovel fleet with consequent appreciable compaction. <br />Studies by Rahn (1975) show that dragline-laid spoils <br />are as much as a hundred times as permeable as truck- <br />laid spoils which yield only small quantities of <br />water to wells. Very probably, therefore, ground- <br />water recharge and discharge from the mined and <br />reclaimed portions of these two tracts would be low <br />and would not be significantly different from inferred <br />pre-mining conditions. <br />Although the increased volume of ground-water dis- <br />charged to the Yampa River system as a result of <br />mining on the proposed lease areas would be generally <br />insignificant in relation to total annual runoff from <br />the watershed, water percolating through the spoils <br />can be expected to increase in dissolved solids con- <br />centration to about 3,000 mg/1 (milligrams per liter). <br />Assuming an average pre-mining concentration of 750 <br />mg/1, the dissolved solids load contributed to the <br />Yampa River and eventually to the Colorado River as <br />a result of mining on the subject lease tracts could <br />be increased from about 30 tons/yr Mons per year) <br />before mining to as much as 550 tons/yr after <br />124 <br />