A popular kind of mining these days is strip mining. When coal is to be found beneath a mountain, the easiest way to get the coal is to remove the mountain, and grab the coal. Unfortunately, this is also the worst for the environment, since both the mountain and where the rock is put generally gets completely destroyed. So federal law, and numerous state laws, require mining companies to repair and reclaim the land after the mining is done. After all, few people wish to live by a massive hole in the ground that will collapse the instant a heavy rain occurs. Mining companies have techniques to fill in the holes, plant grass, and leave the site looking similar to how it looked before, albeit now somewhat flatter.
I want to take my own stab at it. I think we need to fill the lowest level with rock, then we can have a small landfill layer (that we can fill with garbage or whatever), covered by a thick slab of cement. On the cement we have a thick layer of (finished) compost that reaches the surface. In the compost, we plant many many trees. After a few years of care, the trees grow into a mighty forest, which will stabilize the local environment. Areas in which the trees do not survive should be tested for things that may have killed them off, and to find a treatment plan. Can grass be grown instead in those areas? Or, are there chemical problems requiring treatment?
I think that geological research can establish a procedure cheap enough for the mining company, safe and stable enough for the land quality and environment, and accurate enough to be done over and over and over.