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• appreciably after subsidence, but have continued to recover since 1998. TDS values at the Ashley well (Figure <br />28) have exhibited a general decline since 1996, but appear to have gone up slightly in 2006. Field measurements <br />and water quality parameters for the Ashley well are provided on Table 17. Water quality values were within the <br />typical historical range of other wells in this aquifer. <br />3.2 Alluvial Groundwater Monitorine <br />Table 18 presents a summary of alluvial well monitoring frequencies, which was last updated for Permit Revision <br />6 (PR 03-06) in March of 2004. <br />Alluvial ground water in the Twentymile Park Basin exists under unconfined conditions within the alluvial <br />materials underlying the major surface drainages of the area and backfilled areas of adjacent surface mined areas. <br />Stream flows are the primary source of recharge to the alluvial aquifers. Alluvial deposition is limited in areas <br />where stream gradients are relatively steep and in areas where the stream channel has eroded to or intersects <br />resistant bedrock. Consequently, the alluvial deposits do not tend to be continuous. Shallow wells completed in <br />these deposits indicate that they are usually less than 20 feet thick and the depth to ground water is typically less <br />than 10 feet. The limited extent of the Foidel Creek alluvial deposits, and the lack of base flow in the creek <br />indicates that these deposits are relatively insignificant to the area ground water hydrologic system. <br />Alluvial deposits containing groundwater are monitored in the Foidel Creek, Fish Creek, Trout Creek and Middle <br />• Creek drainages. In the Foidel Creek drainage, sites both upstream and downstream of the TCC portals and <br />support facilities are monitored. In the Fish Creek Drainage, sites upstream and downstream of the Mine 2 area <br />and the Fish Creek Borehole mine dewatering facilities are monitored. <br />Foidel Creek Alluvial Groundwater: There are four Foidel Creek alluvial wells, 009-5-10, 001-5-5, 008-AV- <br />I, and 008-AV-2. Tables 19 through 22 provide summaries of the 2004 Water Year data collected at each site. <br />Tables 19a through 22a provide historical statistical summaries of collected data at each site through 2003. <br />Figures 29 through 33 provide graphical representations of water levels and selected water quality parameters <br />recorded at these sites. <br />Water levels during 2006 remained generally consistent with established ranges and patterns and showed the <br />typical seasonal variability of elevated water levels in the spring. Well 009-5-10 provides data for the alluvial <br />aquifer upgradient from the mine portals. Water levels in 009-5-10 for 2006 (Figure 29) are consistent with <br />observed historical seasonal fluctuations. Conductivity values at well 009-S-10 (Figure 30) remain consistent <br />with historical values. <br />Well 001-S-5 is located just downgradient from the mine portals and surface facilities location, and is monitored <br />in conjunction with surface water monitoring site 8. Water levels and conductivity values in 001-S-5 for 2006 <br />(Figure 31 and 32) are consistent with observed historical seasonal fluctuations. Figure 33 is indicative of the <br />• general relationship between the alluvial groundwater elevations and surface water elevations at these two sites. <br />7 <br />