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<br /> <br />Creek that were affected during the high flows of 1984 have again stabilized <br />with TSS values being consistent with values obtained during baseline <br />sampling. Samples obtained from 1985 through 1987 indicate channel <br />stabilization along the Edna Mine was taking place during this time period <br />also. This is indicated by higher TSS values occurring at TR-D than all other <br />upstream sampling stations, except during the low flow periods. Normalized <br />flow with respect to TSS is indicated throughout 1986 and 1987 with the higher <br />TSS values occurring at TR-A and TR-D. The lower values occurring at the <br />intermediate stations (TR-S and TR-C) are expected due to the diluting effect <br />on Trout Creek from the Edna Mine NPDES discharges. <br />Calcium (Figure 3) is the dominant cation in Trout Creek with magnesium <br />(Figure 3) and sodium (Figure 9) occurring in lesser concentrations. The <br />' relative proportions of these parameters change slightly between the sampling <br />points. All show a general increase in concentration with some dilution taking <br />place by the time the water passes sampling point TR-D, as expected. All <br />' three of these cations remain relatively low in terms of drinking water <br />quality. The upper limit established by EPA for theses cations in drinking <br />water is 250 mg/1, The highest concentrations of calcium, magnesium and <br />sodium observed since October 1981 are 110 mq/1, 60 mg/1 and 22 mg/1, <br />respectively. <br />As mentioned in the 1985 Annual Hydrologic Report, upstream of the mine on <br />Trout Creek, bicarbonate (Figure 5) is the major anion with sulfate (Figure 5) <br />concentrations increasing rapidly along the mine area to become predominating <br />downstream. The sulfate levels increase is most markedly noticed prior to the <br />~, peak flow period of Trout Creek as are TDS levels in general. This increase <br />is probably caused by early runoff at the mine site leaching pyritic and <br />' organic sulfur as the flow passes over and through the spoils. Since the flow <br />of Trout Creek is low at that time, the amount of sulfur is sufficient to <br />cause an ionic shift from bicarbonate to sulfate in the anions. An <br />equalization in the sulfate-bicarbonate balance occurs downstream as the <br />source of the sulfate (mined areas) is unavailable and dilution by runoff fzom <br />undisturbed areas is introduced. During periods of higher flow the input of <br />