What are possible by-products of shale oil processing, and what happens to the rocks/sand to prevent pollution?

Nebraskans are concerned about the possibility of a failure of the Keystone Trans-Canada XL pipeline putting the Nebraska Sandhills aquifer at risk. But I have concerns about what happens at the processing end: what happens to the tar sand once it is processed, and what happens to the water which was used to initially used to create the slurry which transports the whole mess in the first place?