I wrote here about the Park Canal and why it should not be restored. I did not include, because I had not then seen it, a link to this report in the Limerick Post. It shows why the gates on the second lock were not replaced. The core problem is that the banks in the upper section of the canal slope too steeply to be stable.
The slope of the banks above the railway bridge (from a boat)
Happily, this deficiency in the original construction has saved us from another foolish restoration.
Irish waterways history 