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Whirlwind Mine Groundwater Characterization Report <br /> Therefore, in a post-mining scenario, groundwater that seeps into the Whirlwind Decline is <br /> expected to reach a natural static head equal to the seepage emanation point in or near the <br /> sandstone unit. Groundwater flow near the decline will return to its natural hydraulic gradient <br /> direction down geologic dip towards the northeast. This flow will preferentially occur within the <br /> sandstone unit which will have a higher overall permeability. Some minor amounts of water will <br /> infiltrate into the mudstone units locally, but this water is also expected to flow along dip to the <br /> northeast. <br /> Any groundwater that seeps around the bulkhead seal will flow into the Salt Wash workings. <br /> This water will flow along the floor of the mine and probably infiltrate. If the historic Packrat Mine <br /> becomes connected to the Whirlwind Decline workings, this seepage will have a greater area for <br /> infiltration. As approved by BLM and DRMS, EFR has a plan for a contingency bulkhead in the <br /> Packrat Mine to seal off any mine water discharge, should it be necessary. <br /> 8.4 Post-Mining Hydrology <br /> The potential for post-mining development of surface springs as a result of mine flooding and <br /> bulkhead installations is small. As described above, the flooded portion of the decline will be <br /> limited to the lower Brushy Basin and groundwater in the flooded decline above the bulkhead <br /> will eventually attain the natural static head of the seepage location at the lower Brushy Basin <br /> sandstone. This static equilibrium will allow groundwater to return to its natural hydraulic <br /> gradient down dip and to the northeast. No greater head levels should develop that would <br /> potentially lead to the development of surface springs. Any seepage that enters the Salt Wash <br /> will drain along the workings in a non-pressurized condition. <br /> Note that the Whirlwind Decline was flooded from 1981 to 2007 and again from late 2009 to the <br /> present and no new springs have been observed in the Salt Wash or lower Brushy Basin. <br /> As approved by DRMS and BLM, EFR has provided a conservative bulkhead design that is four <br /> times thicker than what is required to adequately address calculated water pressures. Low <br /> pressure grouting around the bulkhead will be used to help the rock formation. This design <br /> should substantially reduce the chance for bulkhead failure. Monitoring of water levels will be <br /> conducted to assure static water levels achieve equilibrium and that the bulkhead is performing <br /> as designed. <br /> Western Water& Land, Inc. 58 <br />