Laserfiche WebLink
Whirlwind Mine Groundwater Characterization Report <br /> with an approximate thickness of 400 ft; and the Salt Wash Member of Morrison Formation, <br /> consisting largely of sandstone units with some interbeds of shale and mudstone with an <br /> approximate thickness of 300 ft. The stratigraphically highest sandstone unit in the Salt Wash <br /> hosts the uranium mineralization and is referred to as the Top Rim sandstone; the unit ranges <br /> from 30 to 105 ft thick. <br /> The Burro Canyon forms a thin (approximately 10 ft thick), discontinuous, unconfined aquifer on <br /> Beaver Mesa. The aquifer has the best water quality in the study area but due to its <br /> discontinuous and thin nature, and the lack of private lands in the area, the aquifer is not <br /> commonly used as a water source. The water chemistry from Burro Canyon sources exhibits a <br /> unique chemical signature that is of calcium-bicarbonate water type. <br /> The underlying Brushy Basin is known to contain two to three isolated aquifers associated with <br /> sandstone units: the upper, middle, and lower sandstones. However, since these sandstones <br /> are lenticular in nature, they are not continuous across the project area. The sandstones range <br /> from a few ft to approximately 40 ft thick. The interbedded mudstones have not been shown to <br /> be water-bearing and are considered confining units of low permeability. The lower sandstone <br /> zone within the Brushy Basin is the main source of groundwater seepage in the Whirlwind <br /> Decline. Water quality of the Brushy Basin is generally poor, and the unit does contain <br /> radiologically mineralized zones. Brushy Basin water sources have concentrations of some <br /> regulated constituents that exceed state regulatory groundwater standards. The water chemistry <br /> from Brushy Basin sources indicates unique chemical signature that is of sodium-bicarbonate <br /> water type. <br /> The uppermost sandstone of the Salt Wash, the Top Rim sandstone, is the mineralized ore- <br /> bearing zone that is the target for uranium mining in the area. This unit is considered an <br /> aquiclude. There is no evidence of substantial yield of groundwater from the Top Rim from <br /> historic mines, borehole testing, or exploration drilling. Most historical mining in the area <br /> accessed the Top Rim through tunnels collared at the unit's outcrop, whereas, the Whirlwind <br /> Decline was collared upslope of the Top Rim outcrop in the Brushy Basin. Observations at the <br /> Packrat Mine, which accesses the ore zone from the Top Rim outcrop, have shown that several <br /> exploration drill holes that intercept the workings and at least one vent shaft provide conduits for <br /> aquifer leakage into the underground workings of the Packrat mine from the overlying Burro <br /> Canyon and Brushy Basin hydrostratigraphic units. <br /> Western Water& Land, Inc. E-6 <br />