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Colowyo Coal Company <br />2017 Annual Reclamation and Hydrology Report <br />Ground Water Data - The trend lines of the graphs in Exhibit lA were evaluated. No <br />significant trends were identified, and as such, the information is not included in <br />summary format. This analysis supports the assumed probable hydrologic consequences <br />of minimal impacts to surface water due to mining activity. <br />Summary of the indicator parameters for each ground water site is provided in the <br />following tables. <br />A-6 Well: <br />Parameter <br />Mean <br />Std dev <br />Range <br />Max. <br />Min. <br />Max at <br />Min at <br />Lab pH <br />7.75 <br />0.38 <br />1.9 <br />8.6 <br />6.7 <br />11/30/93 <br />11/21/02 <br />Lab Cond. <br />1110.04 <br />75.25 <br />512 <br />1440 <br />928 <br />05/01/85 <br />04/27/98 <br />TDS <br />695.67 <br />82.36 <br />750 <br />930 <br />180 <br />07/17/01 <br />03/13/93 <br />Sulfate <br />139.11 <br />51.00 <br />334.2 <br />430 <br />95.8 <br />07/17/01 <br />05/15/00 <br />Calcium <br />62.29 <br />16.46 <br />121.1 <br />169 <br />47.9 <br />11/18/97 <br />11/13/00 <br />Iron <br />0.25 <br />0.39 <br />1.81 <br />1.82 <br />0.01 <br />09/26/98 <br />11/18/97 <br />Magnesium <br />53.95 <br />15.49 <br />128 <br />169 <br />41 <br />11/18/97 <br />03/21/11 <br />Sodium <br />123.51 <br />18.30 <br />128.1 <br />146 <br />17.9 <br />3/11/08 <br />04/27/98 <br />Elevation <br />6897.94 <br />2.81 <br />14.53 <br />6902.53 <br />6888 <br />05/01/85 <br />07/31/00 <br />Evaluation of 2017 data for A-6 Well <br />No results from 2017 sampling were minimum or maximum values for any parameters <br />listed above during the monitoring period. Trend line analysis determined no significant <br />correlations over time. <br />A-7 Well: <br />Parameter <br />Mean <br />Std <br />dev <br />Range <br />Max. <br />Min. <br />Max at <br />Min at <br />Lab pH <br />8.02 <br />0.20 <br />0.7 <br />8.3 <br />7.6 <br />05/21/13 <br />11/10/08 <br />Lab Cond. <br />1518.72 <br />182.30 <br />1100 <br />2260 <br />1160 <br />06/18/08 <br />05/05/10 <br />TDS <br />1150.00 <br />238.76 <br />1130 <br />2100 <br />970 <br />06/18/08 <br />11/22/16 <br />Sulfate <br />431.18 <br />136.45 <br />772 <br />1110 <br />338 <br />06/18/08 <br />05/05/10 <br />Calcium <br />125.26 <br />20.15 <br />112 <br />214 <br />102 <br />05/03/11 <br />11/30/17 <br />Iron <br />0.05 <br />0.01 <br />0.05 <br />0.1 <br />0.05 <br />08/17/11 <br />06/18/08 <br />Magnesium <br />122.49 <br />27.60 <br />151 <br />244 <br />93 <br />06/18/08 <br />11/30/17 <br />Sodium <br />46.87 <br />7.06 <br />43 <br />77 <br />34 <br />06/18/08 <br />05/20/14 <br />Elevation <br />6888.67 <br />2.87 <br />14.63 <br />6899.69 <br />6885.06 <br />05/03/11 <br />10/31/12 <br />Evaluation of 2017 data for A-7 Well <br />Minimum values for Calcium, and Manesium were recorded during 2017. Trend line <br />analysis determined no significant correlations over time. <br />Page 10 <br />