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.., <br />Based on the worst case assumptions, the increase in salt <br />• concentration of the mine discharges to the East Fork of the Williams Fork <br />is estimated to be approximately 3.26 mg/1 or a 2.8% increase. This small <br />of an estimated increase is well below levels that might cause concern to <br />downstream water users. <br />If we were to consider the downstream dilution effects of the <br />remaining Hayden Gulch watershed, the estimated insignificant effect of the <br />mine backfill discharge would be further reduced. <br />Long Term Predictions <br />• <br />predictions for the HG Mine would not exceed the BLM predictions. <br />Predictions as to how long before all backfill areas <br />simultaneously discharge spoils water are difficult to make. The Draft <br />Environmental Impact Statement for the James Creek PRLA published by the v J~~`~l <br />BLM in November, 1985 predicts that it will take 40-400 years before that I ~. <br />entire backfill watershed is resaturated and begins to discharge. Our~^CZ~' '~~ <br />To predict how long it will take for the higher concentrations of <br />spoil salts to be flushed from the system is also very difficult to <br />predict. We believe that it will take perhaps thousands of years to flush <br />all the salts from the system and return the discharges to pre-mine <br />concentrations. However, we have shown that the predicted discharges and <br />their impacts represent the early stages .of spoil spring discharges when <br />the highest level of salts are being discharged. The predicted downstream <br />consequences during this time is considered negligible and probably <br />undetectable. Over time, as the salts are flushed from the system, the <br />dissolved solids concentration will decrease, further decreasing the <br />already negligible affects to downstream water quality. <br />Revised November, 1986 <br />~~~~ 1 <br />~7c~n~~ <br /> <br />