2008-03-31_PERMIT FILE - C1980007A (34)

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West Elk Mine In summary, the West Elk Mine site can be characterized as having decreasing penneability with depth as a result of lithologic changes and smaller fracture aperture, limiting downward percolation of groundwater through the bedrock units, and resulting in localized discharge via springs generally above the F Seam. The exceptions are the damaged zones associated with fault systems encountered in the eastern portion of the mine as described above. Additional discussion of these fault-related inflows can be found in Section 2.05.6. Groundwater Quality Characteristics MCC has selected the water quality parameters listed in Table 7 for baseline laboratory analysis to characterize baseline and ongoing groundwater quality. These include iron and manganese, because the detection of these elements (or changes in their observed concentrations) may represent conditions in which metals are mobilized. Additionally, changes in conductivity and TDS can indicate changes in water quality that need to be further investigated. As a result, monitoring of these selected parameters provides a detection system for mining-induced changes in water quality. Therefore, once full-suite analyses have been collected at a site for at least five years, these indicator parameters (pH, conductivity, TDS, and iron) will be collected on an annual basis. Analyses are completed as outlined in the Guidelines for Collection of Baseline Water Quality and Overburden Geochemistry Data (CDMG, 1982). Results are reported in the Annual Hydrology Reports (AHR). If not already provided in AHR's, baseline data will be provided . to CDMG prior to longwall mining under or within the angle-of-draw of a monitored water resource. Regional Groundwater Ouality Data collected on groundwater quality from representative wells within the permit area are summarized in Table 7. As this table shows, the highest average levels of TDS are in well SOM-311 as completed in the B Seam coals. This is consistent with the elevated TDS concentrations in other B Seam wells such as SOM-129-H and JMB-12. The highest average total and dissolved iron concentrations occur in wells SOM-311 and SOM-3E. These wells also produce the highest average manganese values as well. The water chemistry results from these two wells demonstrate a striking similarity between the B and E Seams. This is consistent with the geologic (depositional and lithologic) similarities noted in Section 2.04.6 (Geology Description). The relatively high levels of iron in groundwater (Table 7) are consistent with the levels found in surface water (Table 19) and indicate some groundwater discharge to the streams and a similarity in terms of geology. The only applicable water quality standards for the parameters monitored are secondary drinking water standards. Comparison of these standards to groundwater quality data show numerous dissolved iron exceedances and routine pH levels above 8.5 in three groundwater wells (SOM-38-H-1, SOM-2, and SOM-16). However, the causes of elevated levels of these parameters are natural and not due to mining activities. 0 2.04-74 Revised June 200.1 PRIG, Mach 2006; Rev. Apri12006 PRIO, Sep. 2007PR12