Laserfiche WebLink
Ceolo 9ic Structures. The Seneca II-W Mine permit area is located on the west flank of the <br /> Sage Creek Anticline, a minor structural feature of the regional Sand Wash Basin of <br />northwestern Colorado and southcen tral Wyoming (Bass et al., 1955). The Sage Creek <br />Anticline and the Fish Creek Anticline may join to the south and form [he Williams Park <br />Anticline. <br />Sedimentary strata within and near the Seneca II-W permit area dip to the west at 10-25°. <br />Cround waters within the Me sa verde Croup (Williams Fork and Iles Formations) are confined <br /> <br />above and below by relatively impermeable shale units, although water table conditions <br />occur in the Mesaverde Croup strata near their outcrops. As would be expected, ground <br />waters within valley alluvium are relatively uninfluenced by geologic structures and occur <br />under unconfined conditions. <br />Regional Ground Water Rechar qe, Movement, and Discharge. Recharge to ground waters occurs <br />as infiltration of precipitation and sno~wnelt, 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 />Movement of ground water in the permit area is controlled by geologic structures, <br />stratigraphy and geomorphology. Structural folding and faulting, and st ra tigraphy 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 mater flow is from areas of recharge to areas of natural <br />discharge such as springs, gaining stretches of streams, and areas of phreatophyte growth. <br />Cround water consumption by phrea tophytes and by dr ophytes is significant in the upper <br />Colorado River Basin (Robinson, 1958). <br />Reg Tonal Ground Water Quality. Ground water quality in the Seneca 11-W Mine area is <br />variable and partly depends on aquifer rock type. In general, near-surface ground water <br />in younger geologic formations is of better quality than ground water in older, deeper <br />formations. <br />The relationship between aquifer li Uologics and ground water chemical constituents can be <br />complex. In most cases, cation (usually calcium, magnesium, sodium, anJ potassium) and <br />