The water in the bottom of the mine pit is usually a collection of storm water and ground water seepage. Augusta admits it will be need to constantly pump seepage water from the pit.
A former open pit copper mine in Butte, Mt.
The Augusta reclaim plans show there will be a large pit that will fill with water and the leftover chemical waste from the mine's operation. No fish could ever live in this toxic pond and birds will drink the water and die.
The leach pond is where the ore is sprayed with water and chemicals to release the minerals. All open mines use leach ponds.
The electro-winning system [SX-EW] is a step in the right direction as the mining industry attempts to develop methods that have less of an impact on the environment. Really, it's a huge step since it eliminates tailings impoundments, which are unsightly and can cause water pollution, and smelting, which can cause air pollution. It only works on oxide ore, whereas the majority of the ore at Rosemont is sulfide and will not dissolve into solution in a reasonable period of time. Therefore, leaching can be used on some 14% of the ore, or approximately 59 million tons.
Sulfuric acid, the leaching agent, is brought on site in large tankers. The sulfuric acid is diluted and sprayed or dripped over oxide ore, which dissolves the oxidized minerals completely in the solution. The solution, “pregnant” with the dissolved metals, is then piped to the SX-EW plant that separates out the copper into 99% pure bars. The copper is ready with no need for smelting. The waste solution is piped to on-site holding ponds, which are securely lined, awaiting the next load of oxide ore to be placed on the leach pads.
Here is a good place to learn about copper mining.
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