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John Hamrick <br />January 16, 2001 <br />Page 2 <br />mudstone layer. This mudstone layer serves as a barrier to the downward migration of <br />mine water into the sandstone unit from which the Pack Rat Spring issues. The <br />mudstone layer dips toward the northwest toward the Lumsden fault. Water from the <br />mine workings, reaching the mudstone layer is directed toward the Lumsden fault <br />where it would dissipated toward the northeast. <br />A comparison of chemical-data from the Pack Rat Spring before and after mine. closure <br />with Pack Rat mine water suggests that there been no commingling of the two waters. <br />In addition, trace metals concentrations in the Pack Rat Spring do not show the <br />expected changes, with increase in spring flow rates, if the mine were supplying water <br />to the spring. <br />In that the Pack Rat Spring is separated from the Pack Rat/Hubbard mine workings by <br />an impermeable mudstone which acts as a protective barrier and directs perched <br />ground water away from the Pack Rat Spring; and that chemical data show no evidence <br />that Pack Rat Spring water has been commingled with mine water, one concludes that <br />the Pack Spring is not influenced by nor connected to the Pack Rat/Hubbard mine <br />workings. <br />Hydrogeology of Beaver Mesa <br />Beaver Mesa (Index Map, Figure 1) consists of gently-dipping sedimentary rocks <br />ranging from Permian to late Cretaceous (Figure 2) in age. The stratigraphic unit of <br />interest in this report is the Morrison Formation and in particular the Salt Wash <br />member. The Morrison Formation consists of the lower Salt Wash member and upper <br />Brushy Basin member. <br />The Summerville Formation, which conformably underlies the Morrison Formation, <br />consists of 90 feet of thin bedded, reddish-brown to greenish-gray, shales and silty <br />shales. This formation is extremely uniform in thickness and acts as an aquiclude to the <br />downward migration of ground water. <br />The Salt Wash member of the Morrison Formation consists of 230 feet of lenticular <br />sandstone beds interbedded with red mudstone and shale. The sandstone beds are <br />light gray to light brown to reddish brown and range from fine- to medium-grained. <br />The individual sandstone units are cross-bedded indicating a fluvial depositional <br />environment. Individual beds range from 2 to 10 feet in thickness. <br />The most continuous sandstone bed marks the top of the Salt Wash and is the unit in <br />which the uranium ore deposits are found. This unit is known as the "ore-bearing <br />sandstone". In the vicinity of the Pack Rat/Hubbard mine workings the ore-bearing <br />sandstone is split by a prominent gray mudstone unit.