There might be no money to do it, but there is another reason for the phased work. Lets say you get a small portion of money and the project runs smoothly with no headaches, well then you are highly likely to get more money. But if there is problems with the initial allocation of money - things like, if you go over budget, or it takes forever to get through the planning process or the construction period is dragged out. Then getting another round of money is less likely. It has to be run well, on-time and in budget.