Fracking Drinking Water
The best argument against fracking directly affecting drinking water supplies is that usually the geologic targets are deep, well below shallow fresh water aquifers and frequently drowning in waters full of noxious compounds. But in places that argument falls apart, and an example in Wyoming has shown that fracking fluids have entered a freshwater reservoir. While some of the blame is placed on poor cementing around wells (a problem that has been fingered elsewhere), the paper shows that hydraulic fracturing has extended up to depths overlapping with depths of wells obtaining freshwater. It would be well nigh impossible to keep fracking fluids out of an aquifer if the fracking was occurring in that aquifer.
It is hard to find any defense for this kind of activity, so not surprisingly the results of the study are being disputed. It is quite likely that issues like this have occurred in other area (like the San Juan Basin) where petroleum source rocks are very shallow.
Of course, none of the actions taken by the oil and gas operations are illegal. Fracking is exempt from the Safe Drinking Water Act.