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Stream Standards Comparisons The State of Colorado stream standards applicable for the study area consist of: • Segment 13a: Trout Creek and tributaries excluding Segments 13b and 13c not within a National Forest • Segment 13b: Foidel Creek and all tributaries, Fish Creeks and Middle Creeks and all tributaries from County Road 27 to confluence with Trout Creek • Segment 13c: Trout Creek from headgate of Spruce Hill Ditch to confluence with Fish Creek and Tributaries to Trout Creek for County Road 27 to County Road 179 • Segment 2: Yampa River, mainstem The segments have the similar water quality standards, except that Segment 13a includes drinking water standards for active water supply uses, Segment 13b does not include drinking water standards and Segment 13c includes drinking water standards from June through February. The effect of these segment standards is that the sulfate standard is not applicable to the mine discharge impacted reaches of Foidel, Fish, Middle and 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/l, 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 /l 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 TR13 -83 2.05 -157 11/03/14