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Colowyo Coal Company <br />2013 Annual Reclamation and Hydrology Report <br />GENERAL TRENDS - Surface Water <br />Colowyo currently samples each surface water site for a variety of quality parameters. Of <br />all the parameters that are analyzed for, several key indicator parameters are identified. <br />These are field pH, field conductivity, TDS, sulfate, calcium, iron, magnesium, sodium <br />and flow rate. Statistical analysis is completed and illustrates historical trends for each <br />parameter. See graphs for the trend lines in Exhibit 2A. <br />Surface Water Data - The R2 values for linear regression of the trend lines of the graphs <br />in Exhibit 2A were evaluated. No significant trends were identified, and as such, the <br />information is not included in summary format. This analysis supports the assumed <br />probably hydrologic consequences of minimal impacts to surface water due to mining <br />activity. <br />Summary of the indicator parameters for each surface water site is provided in the <br />following tables. <br />NUGSC: <br />Parameter <br />Mean <br />Std <br />dev <br />Range <br />Max. <br />Min. <br />Max at <br />Min at <br />Lab pH <br />8.14 <br />0.25 <br />1.1 <br />8.6 <br />7.5 <br />04/27/98 <br />10/24/02 <br />Lab Cond. <br />1500.90 <br />277.74 <br />2842 <br />3600 <br />758 <br />03/06/98 <br />05/27/93 <br />TDS <br />1144.99 <br />238.69 <br />1250 <br />1610 <br />360 <br />08/06/01 <br />05/08/02 <br />Sulfate <br />506.66 <br />143.33 <br />760 <br />930 <br />170 <br />07/08/02 <br />05/20/97 <br />Calcium <br />126.83 <br />19.20 <br />165.6 <br />169 <br />3.4 <br />08/02/02 <br />06/01/93 <br />Iron <br />0.77 <br />1.55 <br />8.53 <br />8.54 <br />0.01 <br />05/17/99 <br />02/11/02 <br />Magnesium <br />123.13 <br />29.46 <br />226.9 <br />228 <br />1.1 <br />08/02/02 <br />04/27/98 <br />Sodium <br />47.59 <br />15.72 <br />121.1 <br />138 <br />16.9 <br />11/10/08 <br />04/27/98 <br />Flow rate <br />2.96 <br />3.21 <br />19.94 <br />20 <br />0.06 <br />04/27/98 <br />07/30/13 <br />Evaluation of 2013 Data For NUGSC <br />Flow rate measured on 7/30/2013 was the lowest recorded value for this parameter during <br />the monitoring period. Due to the high variability of flow rate historically, and the fact <br />that the trend line analysis determined no significant correlations over time, the recorded <br />flow appears to be part of normal seasonal patterns. <br />LGSC: <br />Parameter <br />Mean <br />Std <br />dev <br />Range <br />Max. <br />Min. <br />Max at <br />Min at <br />Lab pH <br />8.05 <br />0.25 <br />2.5 <br />8.6 <br />6.1 <br />08/19/91 <br />05/14/91 <br />Lab Cond. <br />1705.04 <br />313.69 <br />2659 <br />2820 <br />161 <br />01/19/93 <br />06/23/92 <br />TDS <br />1351.87 <br />344.14 <br />3420 <br />4050 <br />630 <br />11/08/00 <br />05/23/95 <br />Sulfate <br />649.86 <br />160.18 <br />710 <br />945 <br />235 <br />12/04/89 <br />05/20/97 <br />Page 2 -3 <br />