And this can take decades, until swimming in the water doesn't impact health. Let alone the fact that the additional water to maintain the water level in an unnatural lake like that may be needed elsewhere. What many people forget is that during the excavation all kinds of metals and materials are uncovered leading to red water for the first couple of decades until everything is settled. I am from a german region (Lausitz) where all of that happened and believe me when I say that I'd rather have some out-of-the-job miners than big patches of land filled with lakes instead of "home towns".