2017-05-08_REPORT - C1982056 (3)

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Also: about 130 feet below the Wadge seam is the Wolf Creek Coal Seam. TC began rampling down from, the Wadge to the Wolf Creek seam in October 2014. Following development of the ramp and an initial gate road, mining of the Wolf Creek Coal Seam beganl'in March 2015. I' l' Wadge Overburden: Five Wadge Overburden wells (009-79-4, 006-82-74C, 91M006, 008-77-58, and 93M001) are currently monitored. Water quality sampling is required annually. All monitoring requirements were completed at these sites. Tables 2 through 6 provide summaries of the 2016 Water Year data. Tables 2a through 6a provide some historical statistical summaries of collected data at each site through 2016. Figures 3 through 11 provide graphical representations of water levels and selected water quality parameters recorded at each site. The potentiometric surface in the Wadge Overburden generally slopes from south to north in monitored wells in the vicinity of the TC facilities, as shown by water levels in wells 009-79-4, 006-82-74C, and 91 M006. During 2016, the water levels in well 009-79-4 (Figure 3) continue to be comparable to previous years going back to 1984. Well 009-79-4 (Figure 4) had exhibited a general decline in total dissolved solids since 1995, which has stabilized since about 2000. Well 006-82-74C (Figures 5 and 6) water levels have been relatively stable since 1999, although 2008 did exhibit a slight drop, and has subsequently stabilized through 2016. TDS measurement for 2005 indicated a new high and has dropped off to date, with 2016 indicating an historic low. Well 91M006 (Figure 7) has exhibited a steady decline in water level beginning in 1992, which relates to dewatering impacts from the underground mining operation. These levels have appeared relatively stable over the last five years. TC was recently informed by Miller Water Monitoring Services that they could not get a probe down this well, suggesting the well, which is a 2 -inch steel pipe may have sheared somewhere below ground surface. TC will discuss this situation with CDRMS during their next inspection. Well 008-77-58 (Figure 8) has been unaffected by mining and exhibits seasonal water level fluctuations. During 1998, this well experienced an unusually long seasonal decline, and subsequently an established recovering water level trend resumed. In 2016 TDS concentrations (Figure 9) remain at consistent levels seen since the mid 1990s. The potentiometric surface reflected by well 93M001, has generally been observed to slope froisouthwest to northeast. Well 93M001 (Figure 10) has exhibited a steep decline in water level from 1994 throw 2002. From 2002 TDS appears to be relative y stable, with a drop of 50 feet occurring in 2016. The earlier declines were associated with underground mining of the Eastern Mining District (EMD). The latest drop may be related to mining of the Wolf creek seam. TDS concentrations (Figure 11) in this well remains very stable. No anomalous water quality impacts attributable to mining were evident in data collected from Wadge Overburden wells during 2016, as compared to historical results. Twentymile Sandstone: One well, 006-BRDH-7, requires monitoring for water levels and field parameters ¢n a semi-annual basis, and two wells, FBR-2, and 97013TM, required monitoring for later levels, field parameters, on a semi-annual basis, and water quality parameters on an annual basis. Water quality frequency is annual. All monitoring requirements were completed at these sites during 2016. Tables 7 through 9 provide summaries of the 2016 Water Year data collected at each site. Tables 7a through 9a provide historical statistical summaries of