Laserfiche WebLink
Big Bottom syncline, the Lewis Shale serves as a confining bed that may greatly <br />retard upward leakage of ground water from the Upper Williams Fork. The Lewis Shale <br />overlies the Second White Sandstone in the Pyeatt drainage. Shallow wells in the <br />Lewis Shale may yield 3 to 5 gallons per minute ~WOOdward-Thorfinnson, 1975). The <br />Lewis Shale at well P-3 exhibited a tranamissivity of 2400 gal/day/ft. Permeability <br />of the Lewis Shale at well P-3 was measured to be 107 ft/day. Weathered thin <br />sandstone strata can have high permeabilities, but normally the Lewis Shale should <br />contain permeabilities at least as low as the Upper Williams Fork aquifers. The <br />vertical permeability of the Lewis Shale is likely to be less than 0.001 ft/day over <br />much of this shale. <br />Alluvial Aquifer <br />A gravel pit sump test on the alluvium near the Yampa River yielded <br />tranamissivity and permeability values of 17,500 gal/day/ft and 160 ft/day, <br />respectively. These transmitting values are within the range expected for the Yampa <br />alluvial aquifer. <br />A tranamissivity of 1660 gpd/ft and permeability of 7.4 ft/day were measured <br />for the Johnson Gulch alluvium at well J-1. The Pyeatt alluvium is not as permeable <br />at well P-1, but probably contains areas of high transmitting properties. Aquifer <br />properties for the Flume alluvium were determined at the GC-3 and COY sites. <br />Transmissivities varied from 520 to 14,300 gal/day/ft, while permeabilities varied <br />from 2.4 to 39 ft/day. These values show that the alluvial aquifers are generally <br />the most permeable units at Trapper Mine. <br /> <br />2-462k <br />~y1SED FFR 1 ~ 'R7, <br />