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water levels may be the result of dewatering from historic (pre-TCC) drilling/well sites located in the northern mining district. Some undocumented sites have been identified, and more may exist. Local faulting may also have had some influence. TDS values for well 97013TC (Figure 25) in 2003 appear consistent with historical values. Field measurements are presented in Tables 12 through 17 for Trout Creek Sandstone wells. Field parameter measurements on these wells during 2003 returned values within anticipated ranges with no mine related impacts evident. Well 001-83-106 (Table 12) indicated new maximum values for lab conductivity and pH, although not significantly higher than historic values. Well 001-83-107 (Table 13) indicated a new maximum value for lab conductivity, although not significantly higher than historic values. At Well 95M001 (Table 14), conductivity values continue to be high. In 2003, 95M001 indicated a new maximum value for lab conductivity, although not significantly higher than historic values. In addition, well 95M001 indicated new maximum values for bicarbonate, carbonate, nitrite, and NO3+NO2. Well FBR-2-E (Table 15) indicated a new maximum value for bicarbonate. No new minimum or maximum values were recorded at well 97012TC (Table 16). Well 97013TC (Table 17) established a new maximum values for lab conductivity in 2003, although not significantly higher than historic values. Fish Creek Sandstone: Two Fish Creek Sandstone wells (91M001 and 91M004) had previously required monitoring for water levels on a quarterly basis, and now (per TR03-42), require monitoring on a semiannual basis for water level only. These requirements were met during 2003. An additional well (Ashley) requires semi-annual monitoring for water levels and field parameters, and annual water quality sampling. Tables 18, 19, and 20 provide summaries of the 2003 Water Year data collected at each site. Tables 18a through 20a provide POR statistical summaries of collected data at each site. Tables 18b through 20b provide period of record water level summaries for each site. Figure 26 provides graphical representation of the period of record water levels measured at sites 91M001 and 91M004. Water levels at the Ashley well (Figure 27) dropped appreciably afrer subsidence, but have continued to recover since 1998. TDS values at the Ashley well (Figure 28) have continued a general decline since 1996. Field measurements and water quality parameters for the Ashley well are provided on Table 20. This well established some new maximum and minimum values for tested parameters in 2003, however, none of these values fell outside the typical historical range of other wells in this aquifer. 3.2 Alluvial Groundwater Monitoring i• Alluvial ground water in the Twentymile 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. 7