Undoing dams that have outlived their usefulness--or whose social and economic utility is overshadowed by the environmental harm they do--is an idea that is catching on.
It looks like some people consider environmental harm to be a cost that can be compared to 'social and economic utility' (read benefits).
This week the California Resources Agency is host to a daylong workshop on the Hetch Hetchy [local river] question that promises to look broadly at what is known about the costs--and the benefits--of pulling the dam down.
There are benefits and costs to leaving a dam in place, and there are benefits and costs to removing a dam. Can cost/benefit analysis help us weigh the relative advantages and disadvantages of the alternatives? I think so (as do many others).