The truss bridge was built in 1931 and rehabilitated in 1973. The replacement one-mile-long, bluff-to-bluff bridge started in 2013 was scheduled to be done in Fall 2016, but it was almost a year late (Aug 2, 2017). The new bridge does uses post-tensioning with almost 2,000 miles of strands segment strands. [video] (All of the videos are below in the order that they should be watched.)
The new Saint Croix Crossing bridge. A cell phone photo doesn't do it justice. This is the first and only bridge of its type in North America, an extradosed structure. It uses 5 sets of short towers to avoid spoiling the view from the river, whereas a more conventional cable stayed bridge would have had a pair of 500 foot towers that would have been totally out of character along a National Wild and Scenic River. — at The New Saint Croix River Crossing.
Approaching the new Saint Croix Crossing bridge on the ramp leading up to the pedestrian / bicycle deck.
[I include this photo as a bonus.]
|MNDOT from stcroixcrossing/gallery|
(source of videos: bottom of stcroixcrossing)
If this part of the river had a rapids, then multiple, short towers would be relatively cheap because the bedrock would be close to the surface. But this video indicates the towers are rather expensive because the pier caissons go down as far as 140 feet.