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SUNDAY MINE COMPLEX-HYDROGEOLOGIC REPORT <br /> water chemistry in the saturated Top Rim unit in a location where the mine workings had <br /> flooded. Beginning in 2012, Energy Fuels Resources (USA) Inc. (EFR), who had acquired <br /> Denison, began installation of four surface groundwater monitoring wells (see Figure 3-1). The <br /> wells were installed as a result of discussions with the DRMS and the BLM concerning the need <br /> for a groundwater chemistry baseline and an associated characterization study. Three of the <br /> four wells were installed in the Top Rim Sandstone (unit) within the Salt Wash at upgradient <br /> (MW-SUN3), intermediate (MW-SUN2), and downgradient or point of compliance (MW-SUN1) <br /> locations; groundwater is present in all of these wells. The fourth well (MW-TPZ1) was installed <br /> in the shallow colluvium at the toe of the waste rock area at the Topaz Mine and has remained <br /> dry. Monitoring of the wells includes water level measurements and sampling for water <br /> chemistry. Well construction information is presented in Appendix E. <br /> Groundwater chemistry sampling was conducted at wells MW-SUN1, MW-SUN2, and MW-SUN3 a <br /> total of 7 times from September 2013 to February 2020. The first five sampling events occurred in <br /> consecutive quarters;the last two sampling events were collected in the last quarter of 2019 and the <br /> first quarter of 2020.Wells MW-SUN1 and MW-SUN2 were also sampled in December 2012 and <br /> January 2013, respectively. The analytical data for the monitoring well and previous Denison <br /> samples are summarized in Table 10-3. Table 10-4 shows summary statistics for the analytical data. <br /> Groundwater occurrence and elevation data show that the Top Rim Sandstone is saturated in all <br /> three monitoring wells installed at the upgradient(ambient), intermediate, and downgradient <br /> locations.The Top Rim unit is unconfined at well MW-SUN3 and confined at MW-SUN1 and MW- <br /> SUN2. However, monitoring well groundwater elevation data have showed divergent elevations that <br /> do not conform to a uniform hydraulic gradient. It is suspected that water levels in well MW-SUN2 <br /> reflect inflow from other water-bearing units as water levels are very high.Water levels in well MW- <br /> SUN2 <br /> WSUN2 appear relatively stable, whereas water levels in wells MW-SUN1 and MW-SUN3 have been <br /> gradually increasing with time(see Table 8-1 and Graphs 8-1 to 8-3). The groundwater elevation in <br /> well MW-SUN1 is approximately 77 feet higher than well MW-SUN3. <br /> CDM and Denison (2012) presented water level elevations measured in the spring of 2009 for the <br /> deeper portions of flooded workings in the Sunday/Carnation,West Sunday, and the Topaz Mines. <br /> Water level elevations were also measured in three vent shafts, S-4, S-8, and S-15 in 2019 and <br /> 2020.The vent shaft measurements showed that head in the flooded areas of the mine have risen <br /> approximately 85 feet to an approximate elevation of 5,490 feet above mean sea level (amsl)since <br /> Western Water& Land, Inc. x <br />