alternative:
use freight containers.
hack the tops off, tar the door-ends, load them with some ballast, air-drop 'em into position using tractors or baots with guy-lines to keep 'em stable, then air-drop more ballast in them and sink them in place.
there are hundreds of freight containers available for use over on the Jackson Avenue docks - the HQ yard of Coastal Cargo Inc has more than enough all on its own to do the job.
The heavy airlift needed to do that just arrived this morning. One airport just opened, but the surface vehicles needed to deal with that must just now be rolling off the transport craft.
Some McGuyver-type improvisation (such as you describe) may have helped stem some of the destruction in NO. I'm afraid, however, that our best and brightest minds are currently tied up in the WOT. Shame they can't be in two places at once...