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. Geologic Structures. The Yoest Mine permit area lies on the northern end of the Fish <br /> Creek Anticline, a minor structural feature of the rag lone( Send Yesh Basin of <br /> northwestern Colorado and southcentral Wyoming (Bess et el., 1955). The Fish Creek <br /> Anticline and the Sage Creek Anticline may join to the south and form t he Yilliams Perk <br /> AntlLllne. <br />Sedimentary strata within and near the Yoast area dip at 10 to ZS° along both flanks of <br />the Fish Creek Anticline. Ground waters within the Meseverde Group (Yilliams Fork and <br />Iles Formations) are confined above end below by relatively impermeable shale units, <br />although water table conditions occur in the Meseverde Group strata near their outcrops. <br />As would be expected, ground waters within valley alluvium ere relatively uninfluenced by <br />geologic structures end occur under unconfined conditions. <br />Regional Ground Yater Recharge. Movement, and Discharge. Recharge to ground waters occurs <br />as infiltration of precipitation and snowmelt, and as seepage losses from streams. These <br />processes occur in all areas for shallow alluvial aquifers, while recharge to the deeper <br />confined aquifers occurs primarily in outcrop areas. <br />• <br />Movement of ground water in the permit area is controlled by geologic structures, <br />stratigraphy and geomorphology. Structural folding and faulting, and stratigraphy control <br />the flow of ground water in confined aquifers, while the flow of ground water in <br />unconfined alluvial aquifers is governed by the characteristics of the stream drainages. <br />These characteristics include stream gradient; width, thickness, and hydraulic <br />conductivity of the alluvial deposits; and recharge from or discharge to the underlying <br />bedrock aquifer. Ground water flow is from areas of recharge to areas of natural <br />discharge such as springs, gaining stretches of streams, and areas of phreatoph yte growth. <br />Ground water consumption by phreetophytes and hydrophytes is significant in the upper <br />Colorado River Basin (Robinson, 1958). <br />Regional Ground Yater guality. Ground water quality in the Yoast Mine area is variable <br />and partly depends on aquifer rock type. In general, near-surface ground water in younger <br />gaol ogit formations is of better quality then ground water in older, deeper formations. <br />. The relationship between aquifer lithologies end ground water chemical constituents can be <br />complex. In most lases, cation (usually calcium, magnesium, codium, end potassium) end <br />3 <br />