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Sage Creek basin. Due to the low aquifer transmissivities, seasonal • <br />water level fluctuations are much less pronounced than the alluvium and <br />overburden, and are often masked by water sampling effects. Well YW28 <br />(downgradient of the 1996/99 mine pit in Armand Draw) has experienced <br />decreasing water levels since October 1996, with the lowest water levels <br />on record occurring this year. The October 2003 water level, however, <br />shows an increase. In the Sage Creek basin, water levels at Wells YW29 <br />and 30 were decreasing, but have been increasing since May 2003. Water <br />levels at Well YW7 fall within its historic range. <br />- Wadge Underburden. Four wells; YWU16, 28, 29, and 30; monitor the <br />Wadge underburden. Well YWU28 exists in the Armand Draw basin, all <br />others exist in the Sage Creek basin. Most of these wells do not exhibit <br />any significant seasonal variation, although some variation from year- <br />to-year is evident. We11s YWCJ16 and 30 exhibited water levels this year <br />within their historic ranges. Well YWU28 (downgradient of the 1996/99 <br />mine pit in Armand Draw) has experienced a significant increase (68 <br />feet) in October 2002, followed by a significant drop (67 feet) in <br />October 2003. In the Sage Creek basin, Wells YWU29 and 30 have <br />experienced decreases in water levels since May 1999. YWU29 continues to <br />decline, but YWU30 has experienced an increase this year. <br />- Wolf Creek Coal and Underburden. Wells YWC32 and YWCU31 were abandoned <br />on October 26, 2001. They were about to be buried in spoils. Wells YWC33 <br />and YWCU33 were completed in August 2002 to replace those wells. More <br />data will be needed before trends can be discussed. <br /> <br />Ground Water Quality. Table 4 shows the ground water parameter list <br />used fo r all well water samples. Appendix C provides all ground water <br />quality data collected during the past two years, along with sampling <br />remarks . This is followed by a plot of TDS versus time for the entire <br />period of record. The regression line on this plot is generated by a <br />method known as LOWESS (Locally Weighted Scatter plot Smoothing). A <br />smoothness factor of 1 (on a scale of 0 to 1) was used, which gives <br />maximum smoothing. This plot is followed by a table listing historic TDS • <br />values and percent milliequivalents for major ions. Finally, a <br />4 <br />