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1 <br />1 <br />' 2.04.7(1) (a) (i) (ii) <br />ARCO's investigations of the lithology, stratigraphy and <br />' structure indicates that the aquifers in the area are <br />confined to limited aquifers consisting of the sandstones <br />' and the alluvium in Sylvester Gulch. The sandstones have <br />a negligible contribution as aquifers due to the existence <br />' of many shales acting as aqufcludes. <br />' Following is an excerpt from ARCO's [•1 & R Plan of August, 197h: <br />Recharge to the springs appears to come from snow melt. The <br />' Mesaverde sandstones and the fracture system within these <br />sandstones is the apparent aquifer. The outcropping rocks <br />consist of interbedded lenticular sandstones and shales of <br />' stream channel and floodplain origin. The sandstones, which <br />have low permeability, act as the aquifers, while the shale <br />' layers act as barriers to vertical migration of waters. Thus, <br />each sandstone is a potential aquifer which may or may not <br />' be perched by the underlying shale members. Perched water <br />tables or aquifers appear to be the rule. <br />There is a rather even distribution of a number of springs <br />through the 400' interval above the F seam with a significant <br />increase in the number of springs occurring between 950'-500' <br />and S50'-600' above the F seam. This latter distribution <br />suggests a significant shale or aquiclude layer at these <br />two points. One of the above groups of springs occurs within <br />Poison Gulch, a tributary of the Dry Fork of the Minnesota <br />Creek. The valley bottom parallels tf~e dip, thus giving <br />rise to this stratigraphic zonation of springs. In addition, <br />the spring waters are dominantly low solids (500 ppm, TDS) <br />sodium bicarbonate waters. There is no marked change in water <br />quality with distance above the F seam. <br />45 <br />