Is there a word for "to be built"?
Planned fits.
Plan (verb) - to intend or expect to do.
The planned bridge will have four lanes.
Consider slated.
The bridge is slated for construction starting February 1.
slate: to plan or designate (something) for a particular place and time; schedule.
I would say scheduled. It gets rid of some of the ambiguity of when.
The projected bridge will be one-way, but no one knows why.