Laserfiche WebLink
The upper seal was originally proposed for safety reasons when portal closure <br />included installation of a bat gate that would have allowed access to the lower decline <br />after closure. Later information indicated that the local bat population did not use the <br />Whirlwind decline for roosting and hibernation, possibly because it was too cold. <br />Therefore, backfilling of the portal opening is now proposed and a safety seal is not <br />required. The upper seal is also not needed to protect overlying aquifers because none <br />exist in the decline. The mine portal is located topographically below the middle and <br />upper Brushy Basin aquifers that were delineated by Umetco in Boring BM-001 (see <br />Appendix C of the 112d Application). <br />b. Contingency Plan for Packrat Seal <br />Energy Fuels strongly believes that the evidence shows that there will be no water <br />discharge from the Packrat Mine. There has not been a discharge for many years from <br />the Packrat Mine and Energy Fuels will be plugging the pre-existing shaft and drill <br />holes that likely contribute most of the water currently present within the mine. As <br />previously discussed, new vent shafts and exploration holes will be sealed/plugged to <br />prevent migration of ground water from the upper water-bearing zones. <br />Energy Fuels agrees, however, to bonding for a contingency seal in the Packrat Mine <br />in the event that an area of the mine is opened where ground water inflow from above <br />cannot be controlled with packers, grouting, or other less-costly measures. This seal <br />would be placed as close as possible to the source of ground water to reduce the head <br />requirement for the seal and to minimize the volume of water sealed within the Salt <br />Wash sandstone. <br />According to the evaluation performed by the DBMS using the Einarson and Abel <br />(1990) template for bulk seal design, a concrete bulkhead seal of 1.6 feet can <br />withstand a minimum head of 147 feet. This seal would be placed using low-pressure <br />grout within the sandstone of the Salt Wash Formation. The Salt Wash sandstone is a <br />competent rock with low hydraulic conductivity and high compressive strength (see <br />Attachment B). Since the seal will be placed close to the source, Energy Fuels <br />believes that the maximum head on the seal would be no greater than 147 feet; <br />therefore, the contingency seal cost estimate has been based on a seal thickness of 1.6 <br />feet. An additional cost for a coffer dam and extra piping is included for this seal <br />since it will be assumed that water may be flowing toward the seal from the updip <br />mine workings. The estimated costs for the contingency seal in the Packrat Mine are <br />included in Attachment H of this adequacy response. <br />c Monitoring Well Down~radient of the Proposed Whirlwind Bulkhead <br />Monitoring Well W-1 described in Items 7 and 19 is located downgradient of the <br />proposed bulkhead as shown on Figure F 1 in Attachment E. <br />1::~aer~~ l~l~el5 lisc~~tra;~4 C;c~r~c~ratioi~ 44 t ~nio~a I3cn~let~~ard, 5uiie EiOt) 18 <br />L,~~keG~~c~od. £'C) ~012~ i'hcal~~: 3{}3_c~~4-2440 <br />