Ground water has more problems than fracking can cause.
Leaf mold and barnyard feces get into ground water. Rotting squirrels and other “natural” decay. Stormwater runoff from streets and highways, also. Lots of stuff you just don’t want to drink. That’s why cities have purification plants, especially if they draw from a river.
On the other hand, aquifers are buried under miles of limestone and usually impervious to groundwater seepage.
“On the other hand, aquifers are buried under miles of limestone and usually impervious to groundwater seepage”
You really need to do a bit of reading on “aquifers”.
These will get you started.
http://water.usgs.gov/ogw/aquiferbasics/
http://ga.water.usgs.gov/edu/earthgwaquifer.html