"Why don't we impose an environmental tax (which I believe already exists but have to verify) on the companies?"

The reason we do not is because of lobbyists. The people paying for the elected officials campaigns. Any current environmental taxes are nonsense. The externalities associated with these huge corporations are beyond the scope of most peoples understanding. Gas SHOULD cost well over 5$ a gallon. A t-shirt should cost a Hundred... This applies to everything at the cherished walmarts. The cost should be increased and companies should be responsible for cleaning up the mess being made of the environment. If they don't want to do it, which they have shown they do not, then they need HUGE taxes imposed so the government can do it for them. All this freedom, and american dream nonsense...if the government would let them, these companies would be pouring their toxic wastes in a hole underneath your homes.