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explaining the sampling procedure. This is followed by a plot of TDS <br />versus time for the entire period of record. The regression line on this <br />plot is generated by a method known as LOWESS (LOcally WEighted <br />Scatterplot Smoothing). Unless otherwise noted, a smoothness factor (SF) <br />of 1.0 (on a scale of 0 to 1) was used, which results in maximum <br />"smoothing". Finally, this plot is followed by a table listing historic <br />TDS values and percent milliequivalents for major ions. <br />- Alluvium. Two wells are sampled in the Grassy Creek alluvium. Well 71 <br />monitors the alluvium upstream of mining at Seneca II. It displays an <br />increasing TDS trend. Well 70 monitors the alluvium below Seneca II and <br />also downstream of the confluence with Scotchman's Gulch. It displays an <br />increasing TDS trend; however, the peak TDS value occurred in 2005. <br />In the Cow Camp Creek alluvium (below NPDES 004 Pond), water quality is <br />measured at one well. Well 69 displays a decreasing TDS trend since <br />October 2004. <br />- Wadge Overburden. Four wells are used to monitor the water quality in <br />this stratum. Well 42, located in the south central part of the permit <br />area, usually does not have enough water in its casing to sample, but <br />did have enough water the last three years. Milliequivalent data and the <br />TDS plot from previous samples have been included in Appendix C. It <br />displays a decreasing trend. Wells COV23, COV2633 and COV2702 are part <br />of the PSCM monitor plan. They were first sampled in 2008. Not enough <br />data has been collected so far to determine TDS trends. <br />- Wadge Coal. Five wells are used to monitor the water quality of this <br />seam. Well 17 is located just west of NPDES Pond 002. It displays a <br />slightly increasing TDS trend. Well 19 is located a little over a mile <br />upstream of NPDES Pond 002. It displays a decreasing TDS trend. Wells <br />CW23, CW2632 and CW2701 are part of the PSCM monitor plan. They were <br />first sampled in 2008. Not enough data has been collected so far to <br />determine TDS trends. <br />11 <br />5