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requires semi-annual monitoring for water levels and field parameters, and annual water quality sampling. Tables <br />• 18, 19, and 20 provide summaries of the 2004 Water Year data collected at each site. Tables 18a through 20a <br />provide historical statistical summaries of collected data at each site through 2003. Tables 18b through 20b <br />provide period. of record water level summaries for each site. Figure 26 provides graphical representation of [he <br />period of record water levels measured at sites 91M001 and 91M004. Water levels at the Ashley well (Figure 27) <br />dropped appreciably after subsidence, but have continued to recover since 1998. TDS values at the Ashley well <br />(Figure 28) have continued a general decline since 1996. Field measurements and water quality parameters far <br />the Ashley well aze provided on Table 20. Water quality values were within the typical historical range of other <br />wells in this aquifer. <br />3.2 Alluvial GroundwaterMonitorinp <br />Alluvia] 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 backfi]]ed areas of adjacent surface mined areas. <br />Stream flows are the primary source of recharge to the alluvial aquifers. Alluvia] 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 ]0 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 />Alluvia] 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: During 2004, four Foidel Creek alluvial wells, 009-S-]0, 001-S-5, 008- <br />AV-1, and 008-AV-2 require monitoring on a quarterly basis, and water quality sampling (with exception of 008- <br />AV 1) on asemi-annual basis. Under TR03-42, former wells FO-1 and FO-4 were deactivated and subsequently <br />abandoned in September 2003. All monitoring requirements were met at these sites. Tables 21 through 26 <br />provide summaries of the 2004 Water Year data collected at each site. Tables 21a through 26a provide historical <br />statistical summaries of collected data at each site through 2003. Tables 21b through 26b provide period of record <br />water level summaries for each site. Figures 29 through 37 provide graphical representations of water levels and <br />selected water quality parameters recorded at these sites. <br />Water levels during 2004 remained generally consistent with established ranges and patterns and showed the <br />typical seasonal variability of elevated water levels in the spring. Well 009-S-10 provides data for the alluvial <br />aquifer upgradient from the mine portals. Water levels in 009-S-10 for 2004 (Figure 29) are consistent with <br />observed historical seasonal fluctuations. Conductivity values at well 009-5-10 (Figure 30) remain consistent <br />• with historical values. <br />7 <br />