This happens in alot of jobs btw. Not uncommon to pull in additional crews, pull OT, or even run 24 hr crews in order to meet hard deadlines.
A lot of factors contribute in a jobs schedule.
I don’t understand being “half way through” with a PO.
Why wouldn’t your vendor just send a quote to the University, the University writes the PO (minus tax of course), then the vendor just invoices as materials arrive on site?
Maybe I misunderstood