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C \Users\cwoodwanADesktop \Sundays \FINAL - Environmental Protection Plan Sunday Mines Revised January 2012 docx Section 8 Groundwater Quality monitoring wells located on the south side of the underground mine workings are located in the Top Rim Sandstone, which hosts the uranium- vanadium ore as well as elevated concentrations of associated natural occurring elements such as arsenic, molybdenum and selenium. Groundwater quality data shown in Table 8 -2 display a marked difference between wells screened in the Top Rim Sandstone (WS -1, WS -2 and WS -3) and the well screened in the underlying intermediate siltstones and shales (WS -4). Water quality from WS -4 is saline with TDS of 6,990 mg /L and contains high concentrations of chloride, sodium and sulfate. This water also contains relatively lower concentrations of the ore metals uranium and vanadium and associated elements such as arsenic, molybdenum and selenium. The wells screened in the Top Rim sandstone show relatively higher concentrations of the ore metals and associated elements. This water is also relatively saline with TDS ranging from 1,300 to 1,710 mg /L, but the water contains much lower concentrations of sodium, chloride and sulfate. This marked contrast in uranium and vanadium concentrations in groundwater within the underlying intermediate siltstones and shale indicates that potential anthropogenic effects to groundwater in direct proximity to the underground workings has not affected groundwater located only 63 feet from the underground workings. The groundwater data collected to date supports the hydrogeological framework for the area developed by Weir et al. (1983), which describes groundwater flow moving laterally within the sandstone unit. Vertical flow is restricted by interbedded low permeability units such as the intermediate siltstones and shales of the Salt Wash Member, which limits potential vertical migration of groundwater. The groundwater quality data described above show a marked difference in groundwater quality between the units. Groundwater quality in the Top Rim Sandstone displays a signature associated with the naturally elevated concentrations of uranium, vanadium and other elements that are present in the ore bodies. Water quality from the underlying unit displays a different chemistry with high salinity. This suggests that the intermediate siltstones and shales of the Salt Wash Member may contain natural enrichments of sodium, chloride and sulfate. The groundwater quality data collected to date shows that groundwater located within approximately 40 feet of the underground workings shows a characteristic signature associated with the naturally elevated concentrations of uranium, vanadium and other elements that comprise the ore bodies. This signature does not extend even locally into the underlying intermediate siltstones and shales of the Salt Wash member. The lateral extent of groundwater with this characteristic chemical signature in the Top Rim Sandstone unit is currently unknown. Additional monitoring wells will be installed in accordance with this EPP as discussed later in Section 11— Water Quality Monitoring Plan. 8.3 Existing and Future Uses of Groundwater Existing or potential future uses of groundwater within 2 miles of the Sunday Mines Group are limited because the land is primarily public land administered by the BLM. 8 -5