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<br /> <br />concentrations of manganese also exceeded the <br />agricultural standard. The standard is o.2 mg/1, and the <br />baseline manganese concentrations in the alluvial aquifer <br />were up to 0.67 mg/1. However, the current manganese <br />concentrations in the alluvial aquifer are up to <br />Iron exceedences were observed in the alluvial aquifer <br />and the Wolf Creek Overburden. Baseline data show iron <br />concentrations at or below the standard. Predictions for <br />i~acts on manganese concentrations in these aquifers due <br />to mining should be made in the PHC during the next <br />permit renewal or midterm review. <br />4) Please indicate the rationale for using Agricultural <br />standards as a basis of comparison for groundwater <br />quality. <br />Surface Water Quality <br />5) The surface water quality data presented in Table 20 show <br />four parameters exceeding CDOH Stream Standards for the <br />Yampa River, Segment 13B. Specifically, a total of 11 <br />samples exhibited sulfate exceedences at five locations; <br />seven samples exhibited sulfide exceedences at 6 <br />locations; total recoverable iron exhibited exceedences <br />in two samples at two sites, and nitrate exceeded the <br />standard in one sample. one of the samples that exceeded <br />iron and sulfide standards was upstream of the Seneca II <br />mine. No exceedences of NPDES effluent criteria were <br />observed at the outfalls associated with the Seneca II <br />Nine during 1993. <br />Groundwater Levels <br />6) Well GW-S6-A, completed in the alluvial aquifer, appears <br />to be experiencing a slight steady decline in water <br />level. The water level declines were explained in the <br />1986 AHR as resulting from the removal of beaver dams. <br />Fluoride exceedences were observed in the Wadge coal seam <br />and Wadge underburden. Baseline data on fluoride <br />concentrations do not appear to be presented in the <br />permit application package. A discussion of trends in <br />