That is now the conclusion of the EPA.
The Wall Street Journal reports Fracking Has Had No ‘Widespread’ Impact on Drinking Water, EPA Finds. A senior official from the office of research and development said:
“Hydraulic fracturing activities in the U.S. are carried out in a way that have not led to widespread, systematic impact on drinking water resources … In fact, the number of documented impacts to drinking water is relatively low when compared to the number of fractured wells.”
The risk is in proper construction of the wellbore as it passes through the water table. I’ve previously learned there is an outer casing liner which is sealed in concrete. Then the well bore is placed inside the casing. It is sealed with another round of concrete-like material, which prevents water from moving, should it get through the other concrete and steel in the bore.