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90W. Such a plume would not be expected to form until several years,possibly decades, after the pit is <br /> reclaimed. The Third White Sandstone is monitored in the area of the possible plume in well GP-9, and <br /> the alluvium is monitored with the Coy well. Monitoring data from both wells indicate that a plume has <br /> not reached these wells. Well GC-2 completed in the P White Sandstone up gradient of well GP-9 has <br /> shown evidence of the predicted plume with elevated TDS levels and sulfate levels that initially <br /> increased over time but have since stabilized and appear to be decreasing. Other wells down-gradient of <br /> spoil backfill such as well P-8 completed in the Third White Sandstone and well GD-2 completed in the <br /> R aquifer are also showing signs of elevated TDS/Sulfate likely leaching from backfilled spoils. TDS <br /> Levels in well P-8 appear to have stabilized after a large increase in 1995 but are remaining above <br /> baseline levels. TDS/Sulfate levels in the alluvial wells have fluctuated significantly over the years but <br /> appear to be within natural levels according to TMI's 2020 annual hydrology report. <br /> Surface Water Impacts <br /> Within the area of the proposed SL23 bond release,surface water flows through three different <br /> watersheds and includes discharges through three active NPDES outfalls. The three active discharge <br /> points are all covered under NPDES Permit C00032115 and located in the following gulches: Middle <br /> Pyeatt(NPDES 09),Horse (NPDES 24),and Oak(NPDES 17). All runoff is tributary to the Yampa <br /> River. <br /> Surface water consistently discharges only through Johnson,No Name, and East Pyeatt. The remaining <br /> discharge points seldom if ever record surface water runoff. Throughout the sampling history of the <br /> discharge points,no violations of C00032115 standards have occurred. Seasonal excursions of TSS and <br /> total iron occasionally occur during spring snowmelt or, as a result of an intense precipitation event. <br /> Also on occasion, seasonal excursions of pH occur. Any pH excursions are quickly mitigated by <br /> Trapper Mine with the addition of CO2. Division reviews indicate that there have been no significant <br /> water quality problems at Trapper's discharge points. <br /> No known spoil springs appear to be present on any of the reclaimed lands proposed for bond release in <br /> SL23. Spoil springs that were present at the down gradient contact of spoils and non-mined areas in East <br /> Pyeatt and Oak Gulches were previously Phase III released. <br /> Compliance with Basic Standards for Ground Water <br /> The absence of leachate plume development in the bedrock units indicates that for bedrock units in and <br /> adjacent to the bond release area,the mine operator is in compliance with the Colorado Water Quality <br /> Control Commission's Basic Standards for Ground Water(Rule 41). <br /> Any ground water in alluvial deposits in the bond release area meets the classification of Limited Use <br /> and Quality because the alluvial water is of such small volume in the thin, laterally discontinuous <br /> deposits present that it is not currently used and is unlikely to be used in the future. The Basic Standards <br /> for Ground Water have no water quality standards for the Limited Use and Quality classification. <br /> Division reviews indicate that there have been no significant ground water quality problems in the <br /> monitored formations. <br /> Protection of Ground Water Recharge Capacity <br /> On a local scale,the disturbed area does not significantly divert ground water flows to surface water <br /> Permit Number. C1981010 Page 14 of 16 <br />