Informed look at the groundwater contamination issue:
http://blogs.scientificamerican.com/...t-the-problem/
The problems are:
1) the oil and gas business is extremely fragmented. There are literally hundreds of mom and pop drilling companies and not all of these are operated responsibly.
2) Therefore, proper installation and inspection of the the well doesn't always occur. This is where the big risk for groundwater contamination exists.
3) regulations vary a great deal from state to state. In some states the regulations are significant with good well inspection programs while in others the situation is much more lax. Resource development is profitable in both environments if the geology is favorable.
So if you are worried about groundwater contamination, better well head inspection programs is the key.