2008-11-24_PERMIT FILE - C1996083 (8)

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B-Seam and Strata Above B-Seam Water Quality Analysis, Bowie Coal Mine 0 Water Quality Above B-Seam Water quality data are available from 6 wells installed in the strata above the B-Seam as listed from southwest to northeast: • TC-03-02, Terror Creek, above upper B-Seam, September 2003 to present • TC-03-03, Terror Creek, above upper B-Seam, September 2003 to present • DH-58a, Freeman Gulch, below D-Seam, July 1999 to October 2001 (abandoned) • DD-NM4x98-27, In mine N. mains, above B-Seam, June 2003 to May 2004 (abandoned) • DH-66, Hubbard Creek, below D-Seam, October 2000 to October 2003 (abandoned) • DH-67 Blw, Hubbard Creek, below D-Seam above B-Seam, October 2000 to present The water quality in the strata Above the B-Seam is highly variable with pH values (field) ranging from 7.6 standard units (s.u.) to 12.96 s.u. and pH (lab) ranging from 7.26 s.u. to 11.79 s.u. Coal seam groundwater with pH values greater than 9.5 s.u. is very unusual (Hem, 1970) and commonly indicates contamination from cement or bentonite grout that can occur during initial well installation or from well casing failure (Boulding, 1996). Concentrations of total dissolved solids (TDS) for these sites are also highly variable ranging from 65 to 4,683 mg/1. The high TDS values may also be related to grout contamination. Total iron concentrations range from 0.03 to 31.4 mg/l and total manganese concentrations range from less than minimum detection limit (<MDL) to measurable values of 0.008 mg/1 to 0.56 mg/1(Table 1). The time concentration graphs of water quality data for the only well in the strata Above the B-Seam with baseline data and operational data (DH-58a), does not show any trends or major changes in water quality from samples collected pre-mining to samples collected during mine operations (Appendix A). The time concentration graphs of water quality data for the other 5 wells in the strata Above the 13- Seam reflect only baseline data (TC-03-02, TC-03-03, DD-NM4x98-27, DH-66, and DH-67 Blw) and illustrate the highly variable nature of the water quality both within an individual well and spatially across the Permit area. The variable nature of the water quality may be due to the heterogeneous nature of the coal-bearing strata (Mesa Verde Formation). The Mesa Verde Formation was deposited by a series of transgressive\regressive marine sequences that created highly variable facies both vertically and horizontally in the rock strata. The variability in the strata could influence the ground water quality within individual water-bearing zones resulting in the highly variable water quality seen in the area monitoring wells. As mentioned previously, the extraordinarily high pH values of greater than 9.5 s.u. (Hem, 1970) and TDS concentrations of greater than 5,000 mg/1 from samples in some wells could indicate contamination from cement or bentonite grout (Boulding, 1996) from the initial well installation or from well casing failure. Spikes in the parameter values could also be the result of sampling or laboratory (Appendix A). Wells DH-58a, DH-67131w, TC-03-02 and TC-03-03 have very high pH and TDS values and are likely contaminated from cement or bentonite grout. September 2008 HydroGeo, Inc. 0