2012-09-28_REVISION - M1977307 (23)

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of the wells appear to be monitoring wells associated with remediation efforts in the area. Based on state records, these wells have been sealed and abandoned according to state regulations. There were four deep monitoring wells located within a mile of the mine that penetrated into the Wingate Formation (Table 2). The data showed that the static water level in these wells was hundreds of feet below the base of the Entrada /Carmel Formations and consistent with the depth of the Wingate Formation. These consistent water levels in these monitoring wells indicate the Entrada Formation is dry in the area and the upper- most aquifer for the region is the Wingate Formation. Observations of the Entrada outcrop in the San Miguel River valley show no indication of seeps, springs, or other indications of groundwater discharge. Table 2: Selected Wells in the Vicinity of CM -25 Well Permit # 20485 -MH (CM93 -1) 20485 -MH (CM93 -2) 20485 -MH (CM93 -3) O'Connor Design Group Inc. Top of Casing Elev. Well Depth 5606 ft 850 ft. 5703 880 ft 5458 690 ft Static Water level Elev. 4958 ft. 4942 ft 4924 ft. While the monitoring wells near CM -25 yielded low quantities of water, generally 5 gallons per minute, two wells near Uravan were drilled into the Wingate Formation for industrial and domestic purposes by the Union Carbide Corporation in 1959, and yielded substantial quantities of water - 191 and 500 gallons per minute. 8.3.2 Hydrostratigraphic Structure The geologic structure of the area is also important in predicting the direction of groundwater flow. CM -25 is located on the flank of the Paradox anticline with the geologic formations dipping to the northwest at 0.05 (ft /ft). Groundwater flow directions in the area are controlled by the dip of the rock and would flow in a similar northwest direction. There are no mapped faults within the vicinity of CM -25. There is no indication of any extensive regional fault or fracture systems that could significantly affect the area hydrology. There are no mapped faults or evidence of faulting under stockpiles, future storage areas, or mining areas. 8.3.3 Hydraulic Parameters There is only a limited amount of hydraulic data available for the geologic formations capable of transmitting water at the CM -25 mine area. Consequently, estimates of hydraulic conductivity (permeability) are based on limited site data and reported values for the type of rocks underlying the mine. Reference values for the Entrada Sandstone are from Lohman (1965), while sandstone and shale unit values are from Freeze and Cherry (1979). T -11