2009-07-01_REPORT - C1980007 (6)

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West Elk Mine 2008 Annual Hydrology Report 66 • maximum of 7.9 s.u.; elevated dissolved potassium of 14.94 mg/l compared to the baseline maximum of 8.5 mg/l; elevated dissolved sodium of 1,762 mg/l compared to the baseline maximum of 992 mg/l; and elevated TDS of 4,568 mg/l compared to the maximum baseline value of 2,370 mg/l. Many of these values are suspect or very close to baseline values and there is no apparent indication that these water quality changes are attributed to mining operations. Typically, underground coal mining does not impact groundwater quality but can lower groundwater level due to stratigraphic changes. No significant groundwater quality changes are expected in WY 2009. 5.4.2 Impacts to Groundwater Quantity Routine (post-baseline) monitoring of well groundwater levels is conducted three times per year, corresponding with rising limb, peak flow, and low flow periods. Groundwater level and elevation data for the monitoring wells are summarized in Appendix F. Mining operations have impacted groundwater levels in several wells. Well SOM-45-H-1 and Well SOM-45-H-2 have been affected by the underlying longwall mining in Panel 13. These wells are completed in the barren member of the Mesaverde Formation above the F Seam, respectively. The interburden between this horizon and the mined interval is about 800 feet thick. The well casing in SOM-45-H-1 collapsed between June and September 2002; therefore, the well is obstructed and is no longer functional. Therefore, • no water level data are available for this well subsequent to WY 2002. The dropping water level in SOM-45-H-2 stabilized at about 195 feet in WY 2005, recovered slightly in WY 2006 (193.6 to 192.7 feet) and in WY 2007 (191.7 feet to 190.7 feet). The water level in SOM-45-H-2 continued to rise and the depth to water was 185.0 feet in May 2008, 181.9 feet in June 2008, and 180.0 feet in August 2008. Ground water levels appear to have stabilized and are continuing to recover since mining operations ceased in this area in 2000-2001. Water levels are expected to continue to rise in WY 2009, due to natural recharge. The water level in monitoring Well SOM C-76, installed in the F-Seam, was 289.3 feet in May 2008, 289.0 feet in June 2008, and 293.1 feet in August 2008. The water levels ranged from 280.2 to 276.1 feet in WY 2007 and from 259.9 feet to 265 feet in WY 2006. The average water level dropped about 14.1 feet from WY 2005 to WY 2006; about 15.8 feet from WY 2006 to WY 2007, and about 12.7 feet from WY 2007 to WY 2008, or a total of 42.78 feet since 2005. This may be the result of mining activities in the Northeast Panel of the B-seam area. Water levels will likely rise in Well SOM C-76, as mining operations have ceased in this area. The lowering of the ground water level at Well RAV-4b through WY 2006 is likely due to mining • of the Northeast Panel area and dewatering of the B-Seam. The water level rebound at this site in 2007 and 2008 may be the result of natural recharge after mining in the area ceases. Water levels June 2009 HydroGeo, Inc.