Dams need to be re licensed every 40-50 years by FERC. Small and medium hydro dams are increasingly expensive to re-license mostly due to the cost to install upstream and downstream fish passage.  With wholesale power costs so low (due to oversupply of energy from cracking and other causes) small/medium dams like Carmen-smith might not pencil out.  The re licensing costs can't be recovered by power sales over the 40-50 year license period.  But you can't just mothball or abandon your dam either.  FERC doesn't allow that.  
So we are working to bring Carmen re-licensing costs down.  (Note: It is configured to produce power at times of day when it is most valuable to us. Don't be so quick to kiss it off.)

Leaburg and Walterville are much smaller and were relicensed 15 years ago.  IMHO  we ought to explore removing them when their licenses expire.  There are pros and cons. A robust community debate is needed. If we decide to decommission, we need to start saving money now to pay for it.