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Dames & Moore, 1999 - USDA Forest Service

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3, indicating buffering by iron hydroxide. The host rocks have little buffering capacity from carbonates<br />

or alumino-silicates. Seasonal variations are not apparent for pH. Copper is not abundant in the deposit;<br />

therefore, concentrations are lower than at the Holden Mine, but as pH remains low year round, the high<br />

solubility of secondary copper minerals results in relatively constant copper concentrations. Variations in<br />

copper concentrations are not readily correlated with season. In comparison, zinc concentrations are<br />

elevated throughout the year due to the abundance of zinc in the ore. Zinc concentrations also appear to<br />

peak in April during snow-melt.<br />

6.7.2.2 Waste Rock<br />

Waste rock has been disposed in two primary areas. Seepage is severely acidic and comparable to the<br />

underground drainage. Seepage fiom a second waste rock disposal area emerges at a pH between 4 and 5,<br />

contains elevated zinc concentrations, and has deposited a white precipitate in a nearby small stream. The<br />

precipitate has been found to be amorphous aluminum hydroxide.<br />

6.7.23 Tailings<br />

The tailings disposal area contains various types of ore processing residues including raw, high-sulfide<br />

tailings produced by preferential flotation of iron sulfides, and low-sulfide siliceous tailings. The tailings<br />

are classified as potentially acid generating due to the lack of acid buffering capacity. In one location<br />

downgradient of the high-sulfide tailings, acidic seepage has been noted. Seepage pH varies from 2.8 to<br />

5.5, and is accompanied by about 20 g/L sulfate, and 10 g/L iron. Zinc, lead and copper concentrations<br />

are very low (

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