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Wolf Creek Underburden. One well, WCU24, monitors this unit. It was drilled in August 2001. <br />Not enough data exists to evaluate a trend. In September 2001, its water level was near <br />ground level. <br />Ground Water Quality <br />Introduction. Ground water quality data may be found in Appendix 7-4. Data provided for <br />each well in this appendix begins with a total dissolved solids ITDS) vs. Time plot. The <br />regressions line on this plot is generated by a method known as LOWESS (Locally Weighted <br />Scatter Plot Smoothingl. A smoothness factor of 1 lon a scale of 0 to 11 was used, which <br />gives maximum smoothing. The TDS plot is followed by a table listing percent milliequivalents <br />of major ion and TDS values. This table is followed by a statistical summary of water quality <br />for the entire period of record. This summary is followed by the individual water quality report <br />for each sample collected and finally by a sampling remarks report. An update of data for <br />Permit Revision 3 (Sage/Wolf Creek Coal) in the II-W South area may be found at the end of <br />Appendix 7-4. <br />Alluvium. Well GW-S2W-6A2 monitors the Hubberson Gulch alluvium downgradient of the II-W <br />South area before it is influenced by discharges from central (Pond 0061 mining area. Samples <br />from this well display aCaMg-HCOa type water with an average TDS value of 675 mg/I (range <br />356 to 970) and a nearly level TDS trend since 1988. <br />Well GW-S2W-7A2 monitors the Hubberson Gulch alluvium below Well 6A2 and below the <br />discharge from the central mining area. Samples from this well display aCaMg-HCOaSOoCI <br />type water with an average TDS value of 1213 mg/I (range 760 to 1510, with one likely outlier <br />with a value of 3170 mg/11 and a slightly increasing TDS trend. <br />Wadge Overburden. Well GW-S2W-20V was a flowing monitor well that existed downgradient <br />of the II-W South area. It was sampled from 1980 to 1985 and was abandoned in 1994. <br />Monitoring was discontinued due to a failure of the annual seal of this triple completion well <br />(Wadge Overburden/Wadge Coal/Wolf Creek Coall. This failure was indicated by the <br />observation that flow from one of the wells would vary if the valves from the other two <br />flowing wells were opened or closed. Flow at the ground surface at this site would also be <br />noted when all three valves were closed. This annular seal failure appeared to affect pressure <br />measurements more than water quality, since all three wells displayed distinctly different water <br />quality. Well 20V displayed at MgCa-HCOa type water with an average TDS value of 644 mg/I <br />(range 352 to 7121 <br />Well GW-S2W-40V1 was first sampled in May 1999. Subsequent attempts to sample water <br />quality at this well were unsuccessful since the well was dry. The one sample displayed a <br />147 Revised 01/02 <br />