Earlier quoted context omitted.
It's pretty much what environmentalists have done with dams, right? They buy them and then dismantle them to restore the natural flow of rivers. It's more effective than lobbying the government to pass legislation forcing the removal of the dam.
Has this happened frequently?
Google no longer works for me to find things again that I vaguely remember. What I do remember was that they had taken out multiple smaller dams on a river, and if memory serves me right, a group had bought them for a reasonably low amount as the previous owners had no more use for them.
Most of what I found with a quick search from what I remembered were public/private partnerships to remove obsolete dams (Riverkeeper seems to be a larger player).