Some painter dumped a few cans of solvent on the ground and it seeped in, as one possibility.
I think we’d have to know more about the mix of stuff discovered in the water before we could discern between an actual frack-related problem and some EPA boys crying wolf about an unrelated matter. If it turns out that fracking related shaking allowed somebody else’s ground pollution (not fracking compound) to get into the water, who really do you blame? To take the high road, if there is any truly serious scientific question about fracking activity having had a part in it, I think the fracking company should fix or bypass the wells anyhow, without the need for a morass of lawsuits, but this is a question of policy, not of technology.