As you well know tailings are an integrated part of such operations. These days these things are well controlled. They are constructed in such a way that whatever overflow there is, it will flow into a controlled area where the water quality is measured and maintained to meet all regulations, before let out into a stream flowing out into the surroundings. In Canada since it rains more than what evaporates, there will always be a flow of water out of any tailings dam. That is well understood and engineered. The tailings ponds and the controll system have to be constructed to handle the worst rain fall posssible in the area not to allow uncontrolled water flow out into the environment. I suspect that the rain fall in the region is not that well measured, so that is one thing that has to be done for a couple of years just to make sure that all the designs meet worst case scenerios.

The water leaving the tailings ponds is treated(usually with lime) and measured to meet all requirements(pH, nickel content, suspended particles content, etc). They also do live insect and fish controlls. I forget the names of these specific species but basically they are placed in a bucket of actual water leaving the cleaning stage, and then they measure how many of the various insects and small fish survive for a certain number of days and then compare with acceptable standards.

In the past, tailing leaks and breakouts have happend and caused sever damage to the environment. However, today regulations and knowhow are here that manage tailing ponds very well.

Any mining of nickel in the ROF will require a mill with the production of a nickel concentrate for shippment and tailings for keeping iron sulfides controlled. Shipping of the ore directly, let us say to Sudbury, is out of question due to shipping costs and waste of fuel and energy.