Dames & Moore, 1999 - USDA Forest Service

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control and buffering by alumino-silicates. The Baker Mine is believed to have a regional stable
geochemical conditions. Likewise, the Holden Mine is also believed to be stable.
The similarities with other mines indicates that the experience gained at other sites will be applicable to
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planning remediation at the Holden Mine.
6.8 FLOCCULENT AND FERRICRETE
6.8.1 Flocculent
Iron flocculent is a colloidal material that is generated from baseflow groundwater contributed to Railroad
Creek from the tailings piles. As the pH of the groundwater increases upon contact and mixing with surface
water, iron oxyhydroxides become stable and precipitate. Some of the copper that is in solution and lesser
amounts of cadmium, zinc and other metals coprecipitate with the iron as the iron flocculent is formed.
During the fall and winter months when groundwater flow is low and the flow in Railroad Creek is low, the
majority of the flocculent that is generated settles in the base of the creek bed 'with some limited transport
downstream.
In the spring, when both groundwater and surface water flows m high, flocculent continues to be generated.
Due to the high flow, spring flocculent and flocculent that has accumulated in the Creek bed from
fallhinter are mobilized and are both transported downstream. Flocculent is transported during spring
runoff and precipitation events.
6.8.2 Ferricrete Formation
Ferricrete is typically defined as a conglomerate consisting of sand and gravel cemented into a hard mass by
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