A lot of ill informed if well meaning souls are screaming that fracking causes water pollution.
Fortunately it would seem rather easy to put that worry to rest. Tag the fracking liquid with short lived radioactive tracers, like the same kind of radioiodine used in medical procedures. Or some harmless chemical substance not found in nature. Then get samples of the water table water to check for the tracers’ presence. This doesn’t have to be done to every single well, just a randomized statistical sample of them. It ought to prove to be a definite non problem, with no water getting contaminated at all.
Short half-lives won't last long enough to trace the flow. We're talking feet per year (or maybe inches per year.
"Or some harmless chemical substance not found in nature. Then get samples of the water table water to check for the tracers’ presence."
Fluorocarbons. Soluble in the oil. Available in both liquid and gaseous types. Detectable at incredibly low concentrations with electron capture detectors. And harmless to the environment.