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<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 aquicludes. <br />' Following is an excerpt from ARCO's [d & F. Plan of August, 1976: <br />Recharge to the springs appears to come from snow melt. 7'he <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 laa permeability, (refer to page 46a) act as the aquifers, while the shale <br />layers act as barriers to vertical migration of waters, '.Chus, <br />each sandstone is a potential aquifer which may or may no*_ <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 />' througY: the 400' interval above the F seam with a significant <br />increase in the number of springs occurring between 950'-500' <br />and 550'-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 P7innesota <br />Creek. The valley bottom parallels the 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 />' REVISPD May 15, 1931 45 <br />