When fracking does mix with groundwater
Although claims that fracking (and we speak quite specifically of the process of creating fractures in oil- or gas-bearing strata, not the overall process of petrochemical production) polluted groundwater are legion, the reality has been clouded for quite some time. We knew that groundwater was being polluted by natural gas, and in many instances the problem was clearly an issue with the casing of the drill hole. But a rather thorough examination of one case in Pennsylvania shows that such casing failures can indeed cause fracking fluid to make it into groundwater, as is nicely described in an Ars Technica posting.
Now this still doesn’t mean that fracking fluids are migrating up from the depth range where fracking is being conducted (and such a migration is and will remain unlikely: once the well is fracked, the pressure gradients act to pull material down towards the well bore, not outwards from it). What it does mean is that bad casing jobs can lead to even worse pollution than just that produced by migration of natural gas along the drill hole. And, again, once you pollute these aquifers, cleanup is nearly impossible (in the Pennsylvania case, homeowners were actually bought out). This suggests that drilling companies have to be liable for such groundwater pollution in the same way that a company dumping toxic materials into a river should be (maybe more–the river will clean itself over time; aquifers are not so easy). It further argues for tighter regulation and testing of casing jobs so that such episodes can be avoided.