The project might not be a good allocation of resources. Under a sound money standard, that becomes obvious quickly. If it can't produce enough profit from tolls to repay the loan, it's a poor use of resources. The market is telling you that people value something else more than they value the bridge. Maybe adding a second ferry to reduce the wait time is a better allocation of resources? 

We've been brainwashed by fiat economics to see any infrastructure or any business that "makes money" as productive. Without the ability to finance those things through inflation by issuing debt, only projects that provide a lot of real value will be able to get financing. 

Anything else will have to be paid up front, by someone who values the project for other than purely economic reasons.