2010-06-04_PERMIT FILE - C1982056A (10)

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water use only) are not applicable to the mine discharge impacted reaches of Foidel, Fish, Middle and upper Trout Creeks year- round. The relevant stream segments are shown on Exhibit 50, Figure E50 -4). • In this section, comparisons of ambient water quality conditions are made with applicable standards for selected trace metals and inorganic chemical constituents. For a number of constituents, ambient concentrations were found to frequently exceed the associated stream standard (Table 14 of Exhibit 32, Quantity and Quality Modeling Analyses of Surface -Water Resources of the Trout Creek Basin). This incompatibility between standards and ambient conditions supported results of a similar baseline survey throughout the Yampa River Basin (Wentz and Steele, 1980). The purpose of this comparison is to indicate that exceedances of certain stream standards occur even before considering the impacts of additional mine flows. The several types of data available for this analysis are provided in Exhibit 32, Quantity and Quality Modeling Analyses of Surface Water Resources of the Trout Creek Basin. The average and ranges of concentrations for several trace metals of interest in this comparison of ambient conditions with State of Colorado stream standards are summarized in Table 14 of Exhibit 32, Quantity and Quality Modeling Analyses of Surface Water Resources of the Trout Creek Basin. In the cases of other trace metals, ambient levels exceeded standards for boron, cadmium, copper, lead, mercury, and zinc concentrations (Table 14 of Exhibit 32, Quantity and Quality Modeling Analyses of Surface Water Resources of the Trout Creek Basin). Past monitoring indicated that the mine discharges did not have significant amount of boron. Therefore, boron monitoring was discontinued. The mine discharges are monitored for manganese and iron. Only occasional exceedances have occurred (a total of 18 in 1997 and 1998). In addition, no exceedances of the manganese or iron in- stream standards attributable to the mining operations have been observed (Annual Hydrologic Reports). In the case of chloride, available data indicated average ambient concentrations consistently less than 20 mg /1, compared to a stream standard of 250 mg /1 (Exhibit 32, Quantity and Quality Modeling Analyses of Surface Water Resources of the Trout Creek Basin). For sulfate, ambient conditions exceeded the State of Colorado . stream standard of 250 mg /1 at the following four monitoring sites (Table 14 of Exhibit 32, Quantity and Quality Modeling Analyses of Surface Water Resources of the Trout Creek Basin) for site locations: Site 39, Foidel Creek Tributary, 295 mg /1 Site 14, Foidel Creek, 276 mg /1 Site 8/2005, Foidel Creek, 814 mg /1 Site 29, Middle Creek, 360 mg /1 In addition, sulfate exceeded stream standards from October 1980 to December 1983 21 percent of the time. This is the period of record before mining commenced in 1984 at the Foidel Creek underground mine. Moreover, reported ranges indicate standard exceedances by ambient sulfate concentrations in Fish Creek (Table 14 of Exhibit 32, Quantity and Quality Modeling Analyses of Surface Water Resources of the Trout Creek Basin). In contrast, the maximum reported sulfate concentrations at the lower Yampa River monitoring site was 180 mg /1. In cases where ambient concentrations were found to exceed applicable stream standards, mine impact analyses by the WATBALP prediction module or any other analysis would be expected to indicate such exceedances of stream standards. In summary, in an analysis separate from the modeling, ambient water - quality concentrations were assessed relative to those variables (primarily trace metals) considered in applicable stream standards promulgated by the State of Colorado. These involve Segments 13a, 13b and 13c (Trout Creek and tributaries outside of Routt National Forest) and Segment 2 (mainstream Yampa River). Primary emphasis was placed on comparing data for 15 monitoring sites in the Trout Creek Basin. Ambient conditions based upon historical data prior to the • proposed expanded mining exceeded stream standards set by the Colorado Department of Health for the following water - quality parameters: sulfate, boron, cadmium, lead, mercury, zinc, total iron, and total manganese. Several of the excessively high concentrations occurred in headwater tributary reaches upstream RN08 -05 2.05 -157 03/12/10