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Section 8 <br />Groundwater Quality <br />screened intervals of 13 to 23 ft., 18 to 28 ft., and 33 to 43 ft., respectively. Dedicated <br />tubing was installed in the wells to facilitate sampling with a peristaltic pump. <br />Minor field modifications of initial designs were necessary to facilitate well <br />installation. The primary modifications included the following: <br />Reduced Well Completion Depths: A reduction in the well completion depths <br />was necessary because of repeated borehole collapse during installation. The <br />tendency for the borehole to collapse was a result of the orientation being too <br />close to the dip of the rock units and the corresponding bedding plane <br />discontinuities. <br />Installation of Well Heads above the Water Table: Well heads were installed <br />at an elevation that is several feet above the groundwater table, because of <br />access restrictions within the underground workings. Although the well heads <br />are located in an unsaturated portion of the mine, using the -20 degree <br />installation technique, the well screens for wells WS-2, WS-3, and WS-4 were <br />completed in saturated portions of the subsurface. It appears that the screened <br />interval for well WS-1 is only partially saturated, which adversely affects <br />performance of the well. <br />¦ Installation of One Well North of Underground Workings: The hydrogeologic <br />work plan identified two wells to be installed to assess water quality <br />conditions north of the underground workings. However, during well <br />installation activities, the second well could not be installed because that <br />portion of the mine is no-longer saturated as a result of on-going mine <br />dewatering activities. <br />Groundwater samples were initially scheduled to be collected immediately following <br />purging of the newly installed wells in the underground workings (e.g., December <br />2008). However, the recharge rate of the newly installed wells was relatively low <br />which resulted in a short delay in the scheduled sampling. The low recharge rate is <br />indicative of relatively low permeability of the aquifer. During the week of December <br />22, 2008, Denison was scheduling to reenter the underground workings to purge the <br />wells and collect groundwater samples. At that time, concentrations of radon gas <br />exceeding permissible levels were again present in the underground working and <br />sampling activities could not be completed. Again, during the week of January 5, <br />2009, groundwater sampling activities were planned but were delayed due to high <br />concentrations of radon gas in the subsurface. Following modifications to the mine <br />ventilation system, Denison successfully completed well purging and sampling <br />activities during the week of February 23, 2009. A second round of samples was <br />collected during the week of March 17, 2009. <br />The groundwater quality data show that the groundwater is relatively saline with <br />TDS content ranging from 1,300 to 6,990 mg/L. The groundwater also contains <br />uranium and vanadium, which are the primary ore metals in the mine, and several <br />other elements that are naturally enriched in rocks at the Sunday Mines Group <br />8-3 <br />T:Z4986-Denison Mines\Task Order 4 - EPP Sunday Mines GroupTINAL EPP\FINAL - Environmental Protection Plan Sunday Mines.doc