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• Beneath the Wadge Overburden is a sequence of low permeability siltstones, shales, and coals, approximately <br />200 feet thick. This is followed by a fine-grained massive sandstone, approximately 250 feet thick, known as the <br />Trout Creek Sandstone. The Trout Creek sandstone is the second major regional aquifer, which exists in the <br />Twentymile Park Basin. There is very little hydrologic connection between the Trout Creek sandstone and the <br />overlying Wadge Overburden. <br />Wadge Overburden: During 2002, five Wadge Overburden wells (009-79-4, 006-82-74C, 91M006, 008-77-58, <br />and 93M001) required monitoring for water levels, field pazameters, and water quality parameters on a semi- <br />annual basis. All monitoring requirements were completed at these sites. Note that Wadge Overburden well <br />93M003 was abandoned in advance of mining in August 2000. Wadge Overburden well FBR-11-A was <br />abandoned in December 2001. Tables 1 through 7 provide summaries of the 2002 Water Year data. Tables la <br />through 7a provide historical period of record (POR) statistical summaries of collected data at each site. Tables <br />lb through 7b provide period of record water level summaries for each site. Figures 3 through 16 provide <br />graphical representations of water levels and selected water quality pazameters recorded at each site. <br />The potentiometric surface ht the Wadge Overburden generally slopes from south to north in monitored wells in <br />the vicinity of the TCC facilities, as shown by water levels in wells 009-79~, 006-82-74C, and 91M006. During <br />2002, the water levels in well 009-79-4 (Figure 3) continue to be comparable to previous years going back to <br />1984. Well 009-79-4 (Figure 4) also continues to exhibit a decline in total dissolved solids since 1995. Well <br />• 006-82-74C (Figure 7) has retumed levels typical of the eazly 1990s. Well 91M006 (Figure 9) continues to show <br />a steady decline in water level. The potentiometric surface reflected by wells 93M001, and FBR-11-A (before <br />being abandoned) has generally been observed to slope from southwest to northeast. Abandoned well FBR-11-A <br />(Figure 5), and well 93M001 (Figure 13) had indicated declines in water level since the 1999 water year. These <br />declines were associated with underground mining of the Eastern Mining District (EMD}. Well 008-77-58 <br />(Figure 11) has been unaffected by mining and exhibits seasonal water level fluctuations. During 1998, this well <br />experienced an unusually long seasonal decline, and subsequently an established recovering water level trend <br />resumed. 2002 also exhibited a long seasonal decline, although not as great as that of 1998. <br />No anomalous water quality impacts attributable to mining were evident in data collected from Wadge <br />Overburden wells during 2001. At well 009-79-4 (Table 1), a new minimum value was recorded for lab <br />conductivity. At we11006-82-74C (Table 3), a new minimum value was recorded for dissolved sodium. At well <br />91M006 (Table 4), new minimum values were recorded for field conductivity and dissolved sodium. Elevated <br />pH values remained evident during 2002. <br />Twentvmile Sandstone: During 2002, two wells, 006-BRDH-7 and 91M005, required monitoring for water <br />levels and field parameters on asemi-annual basis, and four wells, FBR-11-B, FBR-2, 97012TM and 97013TM, <br />required monitoring for water levels, field parameters, and water quality parameters on asemi-annual basis. All <br />monitoring requirements were completed at these sites during 2002. Tables 8 through 13 provide summaries of <br />. the 2002 Water Year data collected at each site. Figures 17 through 28 provide graphical representations of water <br />levels and selected water quality parameters recorded a[ each site. <br />4 <br />