well Warragamba took 1800 people to build and I would hazard that the process is a lot more automated these days. so don't think that will use up all the underutilised. I wont comment on your assumptions about their physical ability to do such work, and the problems of overcoming their lack of skills in the construction of dams. personally wouldn't want to be living downstream from a dam built by an army of the unemployed.
I am surprised that the right would be bringing up an obvious reference to the Hoover dam considering its political context. F D was a Democrat, part of the First New Deal. the same man who first introduced welfare legislation in the US.
