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Lennox-Madge Interbu rden. Two wells are used to monitor the eater quality of this strata: • <br />21-LNI and 42P1-LNI. Well 42P1-LNI did not have enough water in its casing to sample this <br />year. Nell 21-LNI, situated out of the permit boundary and doundip of prelaw mining and a <br />fly ash pit operated by Colorado-Ute Electric Association, displays a MgCa-504 type <br />eater. TDS levels have actually dropped in the last four years, as indicated by Table 6 <br />(Appendix A1. This decrease of TDS values may indicate that the most readily soluble <br />constituents may have been flushed from the system. <br />Madge Coal. Tuo wells are used to monitor the water quality of this strata: 17-N and <br />19-N. Nell 17-N, situated doundip from spoils, receives recharge from the Madge <br />Impoundment and the Little Grassy Creek alluvium. It displays a Na-504 type water. TDS <br />values have been increasing at this well since 1985, most likely a result of water from <br />the spoils (with high TDS values) discharging into the Madge Impoundment. Melt 19-4, <br />doundip of mining, has an anomalous eater quality with a high percentage of sodium and <br />bicarbonate. TDS values appear relatively stable. <br />Nolf [reek Overburden/Nadge Underburden. Three wells are used to monitor this strata: <br />7-NCO, SPt-U, and 11-U. Nell 7-NCO, located doundip of the Nolf Creek pit, is a CaMg-S04 • <br />type water. Considerable range in the data makes it difficult to define a iDS trend. <br />Annual precipitation variation and variations in sampling techniques may be the cause. <br />The sampling procedure used since 1487 involves the removal of at least one easing volume <br />(CV) by pumping or bailing. Following the removal of one CV, only enough eater remains to <br />obtain a sample from. TDS values have dropped since 1987 as stagnant well bore water is <br />removed from this low recovery well prior to sampling. <br />Either Nell 8-U or 8P7-U have been sampled in past years, depending on the availability of <br />sampling equipment. Both wells are completed in the same strata and ere only <br />approximately 50 feet apart. Nells 8-U, 8P7-U, end 1t-U have a similar water quality to <br />Nadge coal Nell 19-N. 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) end are completed in adjacent strata, it is likely that they are <br />hydraulically connected and that local geoch emicat conditions are responsible for this <br />water type. The increase in TDS noted at Nells 8-U and SP1-U since 1987 (see Table 8, <br />Appendix A) are probably due [o the subsequent adoption of sampling procedures at these <br />wells that are identical to those mentioned for Nell 7•NCO. • <br />8 <br />