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Lennox-Madge [nterburden. Two wells ere used to monitor the water quality of this strata: • <br />21-LYI and 42P1-LYI. Yell 42P1-LYI did not have enough water in its casing to sample this <br />year. Yell 21-L41, situated outside of the permit boundary and downdip of prelaw mining <br />and an old fly ash pit previously operated by Colorado-Ute Electric Association, displays <br />a CaNg-SO4NC03 type water. TDS levels have actually dropped in the last six years, as <br />indicated by Table 6 (Appendix A). This decrease of TDS values may indicate that the <br />most readily soluble constituents may have been flushed from the system in prior years. <br />Madge Coal. Two wells ere used to monitor the water quality of this strata: 17-Y and <br />19-Y. Yell 17-Y, situated downdip from spoils, receives recharge from the Madge <br />Impoundment and the Little Grassy Creek alluvium. It displays a Na-S04 type eater. TDS <br />values have been increasing at this well from 1986 to 1990, but has decreased slightly in <br />the last two years. Yell 19-Y, downdip of mining, has an anomalous water quality with e <br />high percentage of sodium and bicarbonate. TDS values appear relatively stable. <br />Yolf Creek Overburden/Yadge Underburden. Three wells are used to monitor this strata: <br />7-YCO, BP1-U, and 11-U. Well 7-YCO, located downdip of the Yolf Creek pit, is a CaNg-S04 . <br />type water. The sampling procedure used since 1987 involves the removal of at least one <br />casing volume (CV) by pumping or bailing. Following the removal of one CV, only enough <br />water for one sample remains. TDS values have dropped since 1987, as stagnant, higher TDS <br />well bore water is removed from this low recovery well prior to sampling. <br />Either Yell 8-U or 8P1-U have been sampled in past years, depending on the availability of <br />sampling equipment. Both wells are completed in the same strata and are only <br />approximately 50 feet apart. Yells 8-U, 8P1-U, and 11-U have a similar water quality to <br />Madge coal Yell 19-Y. All exhibit a sodium bicarbonate type water with TDS values less <br />than 900 mg/l. Since they are all situated along the southwest boundary of the permit <br />area (see Exhibit 7-2) and ere completed in adjacent strata, it is likely that the strata <br />are hydraulically connected and that local geochemical conditions are responsible for this <br />water type. The increase in TDS noted at Wells 8-U and 8P1-U since 1987 (see Table 8, <br />Appendix A) are probably due to the subsequent adoption of sampling procedures identical <br />to those mentioned for YeIL 7-YCO. <br />C J <br />8 <br />