Fracking causing leaks of contaminants into groundwater is hugely dependent on the local geology. In locations with lots of natural fractures and nearby sources

Fracking causing leaks of contaminants into groundwater is hugely dependent on the local geology. In locations with lots of natural fractures and nearby sources of drinking water (e.g., Pennsylvania), there's a much higher risk of contamination than in deeper basins with more uniform geology (e.g., North Dakota). That's not to say handwaving is good, but that all geology is local and risk assessment has to be done at that scale.