Vancouver Island Gold Mines

Tailings Disposal

Tailings are the finely ground rock that is left over after the ore has been treated in the concentrator. The chemical and physical nature of tailings solids is very similar to commong river sand and silt. The liquor that is mixed with the tailings solids will contain any chemicals that are left over after the milling process (poisonous cyanide, if you previously chose the Cyanide Leach concentrator option). The gravity process creates no dangerous chemicals, and the flotation process chemicals are similar to the pine oils already common in local waters.

effluent treatment & land impoundment

This disposal option would create a large tailings pond (lake) with a very extensive beach (the tailings solids are the beach). Prior to exiting the concentrator the combined tailings/liquor slurry will be treated with an expensive chemical to destroy any cyanide that remains in the liquor. The resulting water (liquor) in the tailings pond will be environmentally benign. The water will released from the tailings pond into Queen Charlotte Sound when the water level gets too high

The advantage of this system over the decant treatment system (below) is that the liquor in the pond is safe for animals to drink, and in the event of a catestrophic failure of the tailings impoundment, there is no risk to the environment from the liquor (but there will be if the wall of fine mud in the beach gets loose). Small water leaks are of no concern due to the liquor being safe prior to storage.

Capital costs: high
Operating costs: high
Environmental risk: low risk of failure, but would cause large amount of damage

Tailings ponds

land impoundment & decant treatment

This option is similar to the effluent treatment and impoundment option above, except that the chemicals in the tailings liquor is not treated prior to entering the tailings pond. Instead, cyanide in the liquor will naturally degrade due to ultraviolet sunlight, neutral ambient pH, and freezing/thawing in the winter. A small polishing decant treatment system will ensure that any remaining chemicals in the decanted solution are destroyed prior to discharge into the ocean. Animals will be kept away from the poisonous water with fences, and birds will be scared away with noisemaking devices.

The advantage of this system over the effluent treatment system (above) is that chemicals in the solution are not treated until just prior to release into the environment, and the quantity of chemical required is significantly lower (roughly ten to twenty times less) than in the previous option. There is a significantly increased risk to the environment in that any leak of water from the impoundment will release toxic cyanide solution. The risk from catastrophic failure is similarly higher due to the significant danger posed by large quantities of chemical stored in the pond water.

Capital costs: low
Operating costs: moderate
Environmental risk: moderate risk of minor damage from water release; catastrophic risk potential if total impoundment fails.

Decant treatment system

Subsea tailings deposition

The previous tailings disposal systems rely upon a man made lake to hold tailings solids and liquor away from the environment. This system is exactly the opposite, it involves treating the tailings slurry to remove any poisonous chemicals, and then pumping the tailings far out into Queen Charlotte Sound and depositing them in a low spot on the sea floor. The nature of the tailings solids is similar to the silt and sand being carried down the nearby river, so the overall effect on the environment should be similar to the natural deposition of the river delta.

Note that the effect "should be" similar... in actual fact nobody really knows for sure what will happen until it is tried. Previously unknown ocean currents or potentially dangerous reactions between sea water and the otherwise safe chemicals in the tailings liquor may cause unforeseen (and potentially very risky) problems in the marine environment.

Capital costs: low
Operating costs: low
Environmental risk: unlike the land-disposal options, there is no danger of mud flows. There are, however, unknown risks of chemicals and silt upsetting the local environment.

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