2017-05-08_REPORT - C1982056 (3)

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decline since 1996, rose somewhat in 2005, and generally exhibited a dropped again in 2011 through 2013. Levelsliappeared stable the last two years. Field measurements and watlIr quality parameters for the Ashley well are provided on Table 17. Water quality vajues were within the typical historical range of other wells in this aquifer. I II 3.2 Alluvial Groundwater Monitoring Table 18 presents a summary of alluvial well monitoring frequencies, which was last updated for Permit Revision 6 (PR 03-06) in March of 2004. Alluvial ground water in the Twentyinile Park Basin exists under unconfined conditions within the alluvial materials underlying the major surface drainages of the area and backfilled areas of adjacent surface mined areas. Stream flows are the primary source of recharge to the alluvial aquifers. Alluvial deposition is limited in areas where stream gradients are relatively steep and in areas where the stream channel has eroded to or intersects resistant bedrock. Consequently, the alluvial deposits do not tend to be continuous. Shallow wells completed in these deposits indicate that they are usually less than 20 feet thick and the depth to ground water is typically less than 10 feet. The limited extent of the Foidel Creek alluvial deposits, and the lack of base flow in the creek indicates that these deposits are relatively insignificant to the area ground water hydrologic system. Alluvial deposits containing groundwater are monitored in the Foidel Creek, Fish Creek, Trout Creek and Middle Creek drainages. In the Foidel Creek drainage, sites both upstream and downstream of the TC portals and support facilities are monitored. In the Fish Creek Drainage, sites upstream and downstream of the Mine 2 area and the Fish Creek Borehole mine dewatering facilities are monitored. Foidel Creek Alluvial Groundwater: There are four Foidel Creek alluvial wells, 009-S-10, 001-S-5, 008 -AV - 1, and 008 -AV -2. Tables 19 through 22 provide summaries of 2016 data collected at each site. Tables 19a through 22a provide historical statistical summaries of collected data at each site. Figures 29 through 33 provide graphical representations of water levels and selected water quality parameters recorded at these sites. Water levels during 2016 remained generally consistent with established ranges and patterns and showed the typical seasonal variability of elevated water levels in the sp ing. Note that the winters of 2007 and 2011 saw some record snow falls, which is exhibited in the higher water level elevations detected. 2012 was a significant drought year. 2016 was a good snow year. Well 009-S-10 provides data for the alluvial aquifer upgradient from the mine portals. Water levels in 009-S-10 for 2006 (Figure 29) are consistent with observed historical seasonal fluctuations. Conductivity values at well 009-S-10 (Figure 30) remain consistent with historical values. Well 0 1-S-5 is located just downgradient from the mine portals and su ace facilities location, and is monitored in conj nction with surface water monitoringite 8. Water levels saw a ise due to record snow melt (Figure 33). Conductivity values in 001-S-5 for 2016 (F;re 31 and 32) are consistent with observed historical season�l fluctuations.