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Hydrology File - Foidel Creek Mine - 5 - May 27, 1987 Alluvial Wells The Foidel Creek alluvial wells from upstream to downstream are 006-5-10, 006-S-6 and 006-5-5. Well 006-S-6 is approximately 1250 downstream of Pond D, which discharges treated mine discharge water. This site showed the highest TDS of the three sites and a 27% increase in TDS since March, 1984, when the mine initially began discharging water. The impact may not be totally attributable to the mine, as 1984 was a high water year which caused many spoils springs to first begin discharging: Sulfate concentrations have also gone up considerably: The agricultural standards for lead and boron are exceeded at this site. Alluvial well 006-5-5 is approximately one-half mile further downstream from 006-S-6. This site showed an improvement in TDS since March, 1984. In 1986, SAR levels at this site were 10% higher than the historic average, double 006-5-6, and slightly less than those found at 006-5-10, the upstream site. Iron levels increased substantially over previous years and the upstream site, and now exceed the secondary drinking water standard: The manganese situation mirrors that of iron; and it exceeds both the secondary drinking water standard of 0.05 mg/1 and the agricultural standard of 0.2 mg/1. Manganese impacts may be attributable to a spoils spring from Mine 1; which has caused an exceedance of the manganese standard monthly for the first half of 1987. In conclusion, it is difficult to isolate impacts from the undergound mine on downstream alluvial wells, given the proximity of the surface mine. The Division would do well to isolate trace element traits from mine discharge waters to alleviate downstream impacts: The alluvial wells along Fish Creek are currently not directly impacted by the Foidel Creek Mine: Chemically, they exhibit extreme hardness (460 - 1300) and high levels of iron, manganese, sulfate and total dissolved solids, which increase from the upstream site to the furthest downstream site: SAR levels decrease downstream from 5.] to 0: 9. Well 006-AU-3 is an anomaly having only iron and manganese levels which exceed standards. This well also shows historical exceedances of lead and molybdenum. Comparison of Groundwater Impacts with PHC The MLRD identified six probably impacts from the Foidel Creek Mine on the groundwater hydrologic regime: Depletion of groundwater through dewatering could cause spring and well yield depletion, and water quality could become degraded in bedrock and alluvial aquifers, as well as in surface waters receiving mine discharge waters.