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- Alluvium. Two wells are sampled in the Grassy Creek alluvium. Well 71 <br />monitors the alluvium upstream of mining at Seneca II. It recently <br />displays a stable TDS trend (SF 0.25); with the peak occurring in May <br />2010. Well 70 monitors the alluvium below Seneca II (and the PSCM) and <br />also downstream of the confluence with Scotchmans Gulch. It recently <br />displays a stable TDS trend; with 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. Five 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 (as was <br />the case this year), but did have enough water in 2008 -2011. It <br />displayed an increasing trend. Wells COV23, COV2633 and COV2702 were <br />first sampled in 2008. These three wells all indicated increasing TDS <br />trends. However, the range of all historic TDS values, 560 to 810 mg /1, <br />is relatively low when compared to what is observed in other aquifers in <br />the area. Well COV11 was first sampled in May 2011. Not enough data has <br />been collected at this well to determine a TDS trend. <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 />recent stable TDS trend (SF 0.25); with the peak value occurring in <br />2008. Well 19 is located a little over a mile upstream of NPDES Pond <br />002. It displays a stable TDS trend. Wells CW23, CW2632 and CW2701 were <br />first sampled in 2008. Well 23 and 2701 display an increasing trend. All <br />wells, except Well 17, display TDS values between 610 and 970 mg /1. <br />- Trout Creek Sandstone. Well STC5 was used as the potable water supply <br />for the PSCM. Due to a pump failure, the last sample from this well was <br />taken in June 2011. A new replacement well, CTC87, was drilled close to <br />Well STC5 in 2011. As it is the drinking water supply for the PSCM, it <br />is sampled per its CDPHE drinking water permit. <br />5 <br />