...you’re saying that the company was responsible, co-operated with the authorities, supplied the water needs of the residents and complied with the law…if all that’s true, then what’s the problem?

A rather charitable view on your part.  My view is that even if a gas company is a model citizen as it cleans up a mess it has made, that does not change the fact that the mess itself and anything that the company did or did not do to contribute to the mess is still a problem. 

Applying this principle to other situations, even if BP had behaved in an exemplary fashion at every step after the Gulf spill, the spill would still have been a problem.  Or, to use a title business example, if a title agent has misappropriated money from their escrow accounts, if they cooperate with authorities, try and clean up the mess they have left behind and attempt to pay restitution, they've still created a problem.

This would relate in a way to your observation that gas companies are no longer permitted to treat waste water in the possibly hazardous way that was commonplace until earlier this year.  If the water supply was degraded by the old wastewater treatement methods and people's health was negatively affected, there still could be a problem.  Asbestos handling practices were reformed many years ago, but health effects from the old unsafe practices are still a problem.  Lead paint was regulated years ago, but it is still a problem.  Problems caused by a hazardous business practice don't necessarily just go away because the practice is discontinued.