Laserfiche WebLink
Page 6 <br />September 2, 2008 <br />with information EFR has presented in mine permit documents. Influent groundwater was present in <br />the lower sandstone unit of the Brushy Basin Member and was apparent in the upper Salt Wash <br />Member sandstone in the drift area. Minor groundwater production was evident further up the decline <br />within 200 ft of the portal. Groundwater seepage rates from the Brushy Basin sandstone could not <br />readily be quantified due to the diffuse nature of the seepage into the reworked floor materials. Visible <br />flow on the north side of the decline floor was estimated to be between 1 and 2 gpm. <br />EFR conducted exploration drilling in the vicinity of the Whirlwind Mine that indicated that the lower <br />Brushy Basin sandstone was groundwater bearing in a number of locations. Associated data also <br />indicated that the unit was unconfined. Because the lower Brushy Basin sandstone has historically <br />produced groundwater in the decline (a period of record that spans almost 30 years), this unit is likely <br />laterally continuous and/or possibly connected to sand units higher in the geologic section. At a <br />minimum, the sandstone, or at least a facies within the sandstone, exhibits hydraulic properties that <br />facilitate sufficient storage of groundwater. In any case, seepage of water from this aquifer to the <br />Whirlwind Decline has shown a steady rate of influx since the mine was reopened, and will likely <br />continue to discharge into the mine in the future. Recharge to this sandstone unit may occur through <br />vertical and lateral influx of surrounding rock units; the origin of which is from minimal outcrop <br />exposure in areas on Beaver Mesa to the west and south of the mine. Open historic boreholes may also <br />facilitate recharge from upper aquifers. <br />The permanence of groundwater seepage from the Salt Wash Member (upper sandstone) as observed in <br />the drift area of the mine will be evaluated with time. These workings had been flooded for <br />approximately 25 years prior to reopening the decline. Permit documents (Umetco report on borehole <br />BM-001) indicate that the Salt Wash unit was of "insufficient permeability" to yield groundwater to the <br />borehole. This conclusion was made after allowing only 3 hours for the borehole to yield groundwater. <br />An exploration borehole (JB 96-2) drilled by Cotter in the same area apparently yielded groundwater <br />from the Salt Wash Member; however, this information must also be qualified as the borehole was <br />open over a large stratigraphic interval. The assessment of groundwater in the Salt Wash Member <br />within the Whirlwind Mine will be further evaluated as mining activities progress. <br />Surface reconnaissance revealed limited evidence that the Salt Wash Member (ore-bearing sandstone) <br />historically mined in the area is a major groundwater-bearing unit. With the exception of PR Spring, no <br />natural springs or seepage or discharge from mine portals was observed from the stratigraphic horizon <br />that included the ore-bearing, upper Salt Wash Member sandstone. Groundwater that does occur <br />within the Salt Wash Member is likely partially lost through evapotranspiration near outcrop exposures. <br />Flows observed in Lumsden Creek do not indicate that the unit contributes discharge to the stream. <br />Based on surface flow observations, Lumsden Creek showed a loss of flow between County Road 5/10 <br />and the sample location below the Dutchman Mine. However, these observations may be due to <br />subflow within the colluvium in the streambed. <br />Based on visual scans, no evidence of persistent seepage or springs was observed on the hillside above <br />and below the upper Salt Wash Member horizon. Seepage that was observed just inside the Dutchman <br />Mine is likely related to the mine's proximity to Lumsden Creek and/or Lumsden Fault; underground <br />exploration would be needed to further evaluate the source of this seepage. A more thorough <br />evaluation of groundwater conditions can be made once access to the Packrat Mine is possible. <br />An examination of the water quality results and comparison of these data with historic data (Table 2) <br />indicate that the June 2008 PR Spring water quality is within the concentration ranges of historical data. <br />The origin and hydraulic connection of PR Spring water will be further evaluated after reconnaissance <br />of the Packrat Mine. This will occur after EFR re-establishes ventilation in the Packrat Mine, which is <br />scheduled for 2009. <br />Weans090108.doc