|
In this section, comparisons of ambient water quality conditions are made with applicable standards for selected
<br />trace metals and inorganic chemical constituents. For a number of constituents, ambient concentrations were
<br />found to frequently exceed the associated stream standard {Table l4 of Exhibit 32, Quantity and Quality Modeling
<br />Analyses of Surface-Water Resources of the Trout Creek Basin}, This incompatibility between standards and
<br />ambient conditions supported results of a similar baseline survey throughout the Yampa River Basin (Wentz and
<br />Steele, 1980}. The purpose of this comparison is to ittdieate that exceedances of certain stream standards occur
<br />even before considering the impacts of additional mine flows. The several types of data available for this analyses
<br />are given in Exhibit 32, Quantity and Quality Modeling Analyses of Surface Water Resources of the Trout Creek
<br />Basin.
<br />The average and ranges of concentrations far several trace metals of interest in this comparison of ambient
<br />conditions with State of Colorado stream standards are summarized in Table 14 of Exhibit 32, Quantity and
<br />Quality Modeling Analyses of Surface Water Resources of the Trout Creek Basin. In the cases of other trace
<br />metals, ambient levels exceeded standards for boron, cadmium, copper, lead, mercury, and zinc concentrations
<br />(Table 14 of Exhibit 32, Quantity and Quality Modeling Analyses of Surface Water Resources of the Trout Creek
<br />Basin). Past monitoring indicated that the mine discharges did not have significant amount of boron, Therefore,
<br />boron monitoring was discontinued. The mine discharges are monitored For manganese and iron: Only occasional
<br />exceedances have occurred (a total of 18 in 1997 and 1498). In addition, no exceedances of the manganese or iron
<br />in-stream standards attributable to the mining operations have been observed (Annual Hydrologic Reports).
<br />In the case of chloride, available data indicated average ambient concentrations consistently less than 20 mg/l,
<br />compared to a stream standard of 250 mg(l (Exhibit 32, Quantity and Quality Modeling Analyses of Surface
<br />Water Resources of the Trout Creak Basin). For sulfate, ambient conditions exceeded the Stale of Colorado
<br />stream standard of 250 mg(1 at the following four monitoring sites (Table 24 of Exhibit 32, Quantity and Quality
<br />Modeling Analyses of Surface Water Resources of the Trout Creek Hasin) for site locations:
<br />Site 39, Foidel Creek Tributary, 295 mg/l;
<br />Site l4, Foidel Creek, 276 mg/l;
<br />Site 812005, Foidel Creek, 814 mg/l ;and
<br />Site 29, Middle creek, 360 mg/l.
<br />[n addition, sulfate exceeded stream standards from Oetober 1480 to December 1983 21 % of ttte time. This is the
<br />period of record before mining commenced in 19$4 at the Foidel Creek underground mine. Moreover, reported
<br />ranges indicate standazd exceedances by ambient sulfate concentrations in Fish Creek (Table 14 of Exhibit 32,
<br />Quantity and Quality Modeling Analyses of Surface Water Resources of the Trout Creek Basin). In contrast, the
<br />maximum repoRed sulfate concentrations at the tower Yampa River monitoring site was 180 mg/1. In cases where
<br />ambient concentrations were found to exceed applicable stream standazds, mine impact analyses by the
<br />WATHALP prediction module or any other analysis would be expected to indicate such exceedances of stream
<br />standards.
<br />In summary, in an analysis separate from the modeling, ambient water-quality concentrations were assessed
<br />relative to those variables (primarily trace metals) considered in applicable stream standazds promulgated by the
<br />State of Colorado. These involve segment 13a, 136 and 13c (Trout Creek and tributaries outside of Routt
<br />National Forest) and segment 2 (mainstream Yampa River). Primary emphasis was placed on comparing data for
<br />15 monitoring sites in the Trout Creek Basin. Ambient conditions based upon historical data prior to the proposed
<br />expanded mining exceeded stream standards set by the Colorado Department of Health for the following water-
<br />quality parameters: sulfate, boron, cadmium, lead, mercury, zinc, total iron, and tots} manganese. Several of the
<br />excessively high concentrations occurred in headwater tributary reaches upstream from any current mining
<br />activity. In addition, a basinwide survey of water quality conditions for the Yampa River Basin revealed ambient
<br />conditions exceeding stream standards (Wentz and Steele, 1980).
<br />APPROVED FED 0 8 2000
<br />TR 99-32 2.05-158 I I/IS/94
<br />
|