REP28782

• Permit No: C1980001
• IBM Index Class Name: Report
• Doc Date: 12/11/2001
• Doc Name: 1994 AHR text and data
• Annual Report Year: 1994
• Permit Index Doc Type: HYDROLOGY REPORT
• Media Type: D
• Archive: No

Sulfate/Bicarbonate
As noted in previous annual hydrology reports, upstream of the mine
on Trout Creek, bicarbonate (Figure 10) is the major anion with sulfate
(Figure 11) concentrations increasing rapidly along the mine area to become
' predominating downstream (Figure 12). The sulfate levels increase is most
markedly noticed prior to the peak flow period of Trout Creek and adjacent
to mining activity, as are TDS levels in general. This increase is
probably caused by early runoff at the mine site leaching pyritic and
organic sulfur as flow passes over and through the unreclaimed spoils.
Since the flow of Trout Creek is low at that time, the amount of sulfur is
' sufficient to cause an ionic shift from a bicarbonate type water to a
sulfate type. During periods of higher flow within Trout Creek and later
in the season when runoff from the mine is small relative to Trout Creek
to
hift th
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sulfate type with concentrations of bicarbonate and sulfate being
approximately equal downstream.
As mining activities have shifted from West Ridge to Moffat, the
~~ 1992-1994 trend shows that the topological change generally still occurs at
TR-B. This is believed to be the result of the spoil spring which has
1 developed at the base of the West Ridge mining area. As further
reclamation activities continue in West Ridge, the spring exhibiting the
high levels of sulfur is anticipated to decrease in flow. Once the
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hydrologic reconstruct
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reestablished, the majority of excess runoff not used by the reestablished
vegetation will be diverted along the reconstructed surface drainage system
rather than being allowed to pass through the regraded spoils as is
currently the case. The 1992-1994 trend showing a peak sulfate levels at
TR-C and TR-D are expected to continue for the duration of mining in the
Moffat Area.
' While peak levels of individual constituents may be shifting as flow
' proceeds past the mine, they do not seem to be increasing overall and it is
lance or a
at
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ate-
believed that an equalizat
on
reversal (similar to the balance at TR-A) occurs downstream as the source
of available sulfate (active mining areas) is unavailable and dilution by
runoff from undisturbed areas is introduced.

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