2009-07-01_REPORT - C1980007 (6)

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West Elk Mine 2008 Annual Hydrology Report 63 • mining related water quality issues at any of these locations through WY 2008 and none are expected in the future. 5.4 Groundwater MCC maintains a network of 28 groundwater monitoring wells (including seven dysfunctional wells with collapsed casing or obstructions) throughout the permit and lease areas. A summary of the groundwater well monitoring schedule is presented in Table 6 and the well completion data is presented in Table 7. The locations of the groundwater monitoring wells are shown on Map 2. The well water elevation and depth to water data are presented in Appendix F and the groundwater quality data are presented in Appendix G. The casings in several monitoring wells have collapsed in the past several years and are likely the result of mining-induced subsidence. As a result, hydrologic data from these damaged wells are not available for the water years subsequent to the date noted in parenthesis. The damaged wells include: SOM-2-H (July 1999), SOM-16-H (September 2000), 96-27-1 (April 2002), SO.W-1 (June 2002), and SOM-45-H-1 (September 2002). Well 23-H-1 (August 2006) has obstructed and damaged casing resulting from poor installation procedures, not related to mining activities. SOM 13 (April 2007) has recently become obstructed; therefore, hydrologic data are not available for this site for WY 2007 or WY 2008. Additionally, the casing is compromised in Well SOM 23-H-2 (August 2008), so there are no water quality data for this well for WY 2008. 5.4.1 Impacts to Groundwater Quality Groundwater quality data are collected for permit specified parameters at monitoring wells throughout the permit area in order to detect potential impacts of mining activities to groundwater resources. Potential impacts to groundwater are determined by comparison to baseline values and consideration of climatic conditions. In general, there were only minor water quality changes in a few of the groundwater monitoring wells during WY 2008 (Appendix G). As noted above, no water quality or water level data are available for WY 2007 or WY 2008 for seven damaged monitoring wells. Additionally, no water quality data are available for WY 2008 for Well SOM- 23-H-2, because the casing is compromised. However, in WY 2008 there were several minor changes noted in the water quality at Upper Dry Fork Alluvial Well, Lower Dry Fork Alluvial Well, SOM 80, SOM C-76, SOM 23-H-4, SOM 23- H-3, SOM 23-H-2, 03-11-1, SOM 3E, 96-2-2, RAV 413, SOM 129- H, 01-11-1, and SOM-313. The Upper Dry Fork Alluvial well had a slightly elevated conductivity of 559.4 µmhos/cm compared to the maximum baseline value of 509 µmhos/cm; elevated dissolved arsenic 0.026 mg/I June 2009 HydroGeo, Inc.