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Colowyo Coal Company <br />2009 Annual Reclamation and Hydrology Report <br />• Colowyo currently samples each ground water site for a variety of quality parameters. <br />Of all the parameters that are analyzed for, several key indicator parameters are <br />identified. These are lab pH, lab conductivity, TDS, sulfate, calcium, iron, magnesium, <br />sodium and elevation. Statistical analysis is completed and illustrates historical trends <br />for each parameter in Exhibit 2B. <br />Ground Water Data - The Rz value for linear regression is indicated below. <br />Site Id Lab <br />pH Lab <br />Conductivity TDS Sulfate Calcium Iron Magnesium Sodium Elevation <br />(feet) <br />A-6 0.0739 0.0047 0.0328 0.0007 0.0024 0.0101 0.0087 0.0787 0.0017 <br />A-7 0.0122 0.5593 0.5545 0.4543 0.4655 0.75 0.4306 0.4776 0.5183 <br />A-8 0.046 0.3965 0.3319 0.3159 0.5012 0.0417 0.3688 0.0882 0.4515 <br />NGSW 0.0248 0.0828 0.1226 0.0077 0.0325 0.2398 0.00005 0.2647 0.0912 <br />Gossard 0.0105 0.6266 0.7978 0.556 0.4094 0.0732 0.4354 0.0784 0.5039 <br />MT-95- <br />02 0.0122 0.0457 0.1046 0.0401 0.0004 0.0068 0.0034 0.1817 0.0034 <br />Summary of the indicator parameters for each ground water site is provided in the <br />following tables. <br />A-6 Well: <br />Parameter Mean Std dev Range Max. Min. Max at Min at Trend <br />Lab pH T61 0.34 1.9 8.6 6.7 11/30/93 11/21/02 Increasing <br />Lab Cond. 111.3.81 78.50 510 1440 930 05/01/85 04/27/98 Increasing <br />TDS 695.69 97.38 750 930 180 07/17/01 03/13/93 Increasing <br />Sulfate 1415.71 59.41 334.2 430 95.8 07/17/01 05/15/00 Increasing <br />Calcium 63.96 18.16 121.1 169 47.9 11/18/97 11/13/00 Decreasing <br />Iron 035 0.45 1.81 1.82 0.01 09/26/98 11/18/97 Decreasing <br />Magnesium 55.48 16.73 127 169 42 11/18/97 08/19/82 Decreasing <br />Sodium 121.24 18.53 124.1 142 17.9 3/11/08 04/27/98 Increasing <br />Elevation 6897.76 3.22 14.53 6902.53 6888 05/01/85 07/31/00 Increasing <br />0 <br />Page 2-5