Dan: you have several separate strands there.
First, I'm not sure what the canal towing-path's "fullest potential" is or why it should have to reach that potential. It is already, as you know, much used; it seems to me that there are simple, cheap ways of increasing the level of use, and especially of using it as a tourist attraction. But the canal itself doesn't need anything done about it: it just sits there, with nature and anglers and stuff. Most Irish canals are little used by boats. How many pass through Dublin, between the twelfth lock on the Royal and the twelfth on the Grand, each year? Very few. But that doesn't stop people walking by them.
I don't know what it would cost to make the thing navigable. About ten years ago I was told that the cost of a lock was about one million euro, but much depends on the condition of the lock. Like those on the Shannon--Erne Waterway http://irishwaterwayshistory.com/abandoned-or-little-used-irish-waterways/waterways-of-ulster-and-thereabouts/lock-gear-on-the-junction-navigation-sew/
, it might have to be dismantled piece by piece and rebuilt with a concrete lining and the old stonework on top. The bridge itself might need attention too. Then there's dredging: it might be tricky on the canal, but it might be equally so on the river. I don't know what condition the boatstream (the portion of the river close to the towing-path that would have been kept clear for boats) is in after eighty years. Dredging in an environmentally friendly way, without being attacked by anglers, and with no road access, might be difficult. But these are engineering matters, and I'm afraid I just don't know the answers. I suspect that the total cost would be in the millions, and I do know that Waterways Ireland's capital budget for all waterways is €4.5 million http://irishwaterwayshistory.com/2011/12/19/the-dahg-view-of-waterways/
. My main point is that there is no conceivable return on money spent restoring the Park Canal; yours, I think, is that the canal would look nicer with boats on it and thus attract more people to visit it. Perhaps this solution http://www.thisisstaffordshire.co.uk/3D-artwork-makes-splash-village/story-12499357-detail/story.html
would be cheaper.
On the derelict sites, the abandoned buildings were being used until the powers-that-be put steel sheets over the doors and windows. And the buildings also look attractive with interesting painting on them. I'd like TPTB to add some information about the history of the harbour, but in the meantime it is nice to see that active citizens have been doing their bit with their spray cans. I agree that it would have been nice to have caffs and so on, but the site owners don't seem to be interested in such developments and I doubt if there will be money for them for many years to come. And, of course, the harbour would be enhanced by having boats in it, and could have been a better destination than the Custom House, but (a) it would still be very hard to get in there from the Abbey River and (b) that too is not going to happen.
You don't have to go to Wales to find people living on boats. There are significant colonies at Lowtown, Sallins, Hazelhatch and (now to a much lesser extent) Shannon Harbour on the Grand, with a few on the Royal at Blanchardstown and some others scattered hither and yon around the waterways; I wrote about some of the issues here http://irishwaterwayshistory.com/rants/living-on-the-canals/
. I don't myself think that Grove Island would be a suitable location: while Goytre Wharf is on a canal, Grove Island is on a river with a large tidal range and very strong currents. I don't think it's a safe place for residential moorings — and I would be surprised if Waterways Ireland would permit any (further) narrowing of their navigation. The best place in Limerick for such moorings is in the dock: a large body of still water, little used. But whereas previous recessions saw increases in demand for cheap narrowboats to live on (some, perhaps, about to fail their BSS checks in the UK), the current surplus of housing may mean that living in a small steel box becomes less attractive.
Cheap and cheerful improvements, not expensive engineering, are what we need. bjg