There indeed was/is a two-phase power. It dates back to the very first AC systems set up by Tesla at Niagra Falls.

The phases are offset by 90 degrees. There's four wires just as you say. This allows for self-starting AC induction motors. Again, Tesla was the guy to identify that you need more than one phase to self-start an induction motor. Today, we use a cap to shift a single phase to start a single-phase induction motor. 

I'm hoping you're not constrained to 25Hz power at Ft. Peck. That would be carrying the homage to Tesla just a wee bit too far. ;-)