2010-03-12_REPORT - C1981019 (7)

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Colowyo Coal Company 2009 Annual Reclamation and Hydrology Report . A-7 Well: Parameter Mean Std dev Range Max. Min. Max at Min at Trend Lab pH 7.84 0.14 0.4 8 7.6 8/13/08 11/10/08 Increasing Lab Cond. 1565.71 314.64 910 2260 1350 6/18/08 8/19/09 Decreasing TDS 1227.14 391.65 1110 2100 990 6/18/08 8/19/09 Decreasing Sulfate 494.43 272.65 744 1110 366 6/18/08 11/2/09 Decreasing Calcium 129.86 24.99 70 186 116 6/18/08 8/19/09 Decreasing Iron 0.05 0.00 0.00 0.05 0.05 6/18/08 6/18/08 Level Magnesium 134.71 48.32 133 244 111 6/18/08 8/19/09 Decreasing Sodium 48.14 13.40 40 77 37 6/18/08 8/19/09 Decreasing Elevation 6890.13 3.7595 8.88 6895.87 6886.99 6/18/08 11/2/09 Decreasing A-8 Well: • Parameter Mean dSted Range Max. Min. Max at Min at Trend Lab pH 7.87 0.1799 0.5 8.1 7.6 8/19/09 11/10/08 Decreasing Lab Cond. 1128.57 197.27 540 1570 1030 11/2/09 11/10/08 Increasing TDS 818.57 200.87 560 1260 700 11/2/09 6/03/09 Increasing Sulfate 268.0 144.95 401 579 178 11/2/09 8/19/09 Increasing Calcium 110.14 25.39 75 165 90 11/2/09 6/18/08 Increasing Iron 0.09 0.12 0.31 0.36 0.05 11/10/08 11/2/09 Decreasing Magnesium 90.14 19.95 56 134 78 11/2/09 6/3/09 Increasing Sodium 15.57 4.16 10 21 11 11/2/09 11/10/08 Increasing Elevation 7107.60 6.48 16.39 7116.93 7100.54 6/18/2008 11/2/09 Decreasing NGSW: Parameter Mean Std dev Range Max. Min. Max at Min at Trend Lab pH 7.74 0.30 1.7 8.5 6.8 8/19/91 10/03/00 Increasing Lab Cond. 1976.56 282.21 1550 2700 1150 10/17/91 04/27/98 Increasing TDS 1597.00 261.59 1320 2100 780 8/13/08 04/27/98 Increasing Sulfate 768.78 168.11 1053 1340 287 3/17/09 04/27/98 Increasing Calcium 166.40 31.37 169.30 262 92.7 09/27/90 10/08/98 Increasing Iron 0.38 0.62 3.98 3.99 0.01 4/27/98 10/21/02 Decreasing Magnesium 165.70 31.85 194 270 76 09/27/90 04/27/98 Increasing Sodium 90.14 21.78 154.3 186 31.7 05/18/06 04/27/98 Increasing Elevation 6534.76 2.02 10.85 6540.65 6529.8 03/13/93 08/31/04 Decreasing Page 2-6