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Whirlwind Mine Groundwater Characterization Report <br /> occurs in the various hydrostratigraphic units does not attain storage and head levels that result <br /> in visible discharge to area drainages that would result in perennial stream flow. <br /> Groundwater has been investigated and found to occur in two primary hydrostratigraphic units <br /> above the Top Rim sandstone unit of the Salt Wash Member of the Morrison Formation which is <br /> the mineralized mining zone in the study area. These aquifers include the Burro Canyon <br /> Formation and the Brushy Basin Member of the Morrison Formation. The Burro Canyon and <br /> Brushy Basin aquifers are considered aquifers because both formations readily yield <br /> groundwater to wells when pumped. No formal subsurface investigations have been conducted <br /> to investigate deeper groundwater sources underlying the Salt Wash. <br /> The shallowest aquifer exists in the Burro Canyon Formation, (which forms bedrock in the <br /> highlands west of the Whirlwind Mine area), and where present, occurs at the base of the <br /> formation and may extend into mudstones or sandstones of the underlying upper Brushy Basin. <br /> Existence of the Burro Canyon aquifer is best represented by the Dolores Point well which is <br /> located just over one mile to the west of the Whirlwind Decline portal. The aquifer is also <br /> represented by drill hole and borehole observations on Dolores Point and by DP Spring, which <br /> occurs near the aquifer's base north of the Whirlwind Decline. The Burro Canyon aquifer is <br /> unconfined and its saturated thickness is expected to spatially vary, and in some instances is <br /> not present at all. <br /> The Brushy Basin Member has shown to contain two to three subunits that bear groundwater <br /> associated with sandstone units; these units are referred to as the upper sandstone, middle <br /> sandstone, and lower sandstone. The Brushy Basin groundwater is associated with sandstone <br /> units bound above and below by mudstone and shale. These individual groundwater-bearing <br /> units are unconfined and may be perched such that interspatial zones may be devoid of <br /> groundwater. Regionally, these"channel sands" are lenticular in nature and may spatially vary <br /> in thickness or pinch out completely. This is a reflection of their alluvial depositional <br /> environment. The Brushy Basin aquifers appear somewhat consistent in the vicinity of the <br /> Whirlwind Mine, occurring in Monitoring Well W-1, the Whirlwind Decline, and on Dolores Point <br /> on Beaver Mesa, a few thousand feet to the west. <br /> Observations indicate that the Top Rim sandstone of the Salt Wash may be water-bearing in <br /> places. The occurrence of groundwater in the Top Rim sandstone is mostly indicated by the <br /> Western Water& Land, Inc. 49 <br />