Tim,
      One of the photos in the collection provides your answer. It shows a crane lifting a girder into position, with a second girder spanning two flatcars seen on the tracks below. No barges in sight. Thanks for sharing the link, there are some great photos there.

Regards,
Bob Heninger
Minot, ND

UP box cars
https://www.facebook.com/130170407077838/photos/a.562900027138205.1073741854.130170407077838/562994253795449/?type=3&theater

flat cars with girder
https://www.facebook.com/130170407077838/photos/a.562900027138205.1073741854.130170407077838/562994383795436/?type=3&theater

PFE reefers and flat cars with girder
https://www.facebook.com/130170407077838/photos/a.562900027138205.1073741854.130170407077838/562994487128759/?type=3&theater

rail to dinkey transfer
https://www.facebook.com/130170407077838/photos/a.562900027138205.1073741854.130170407077838/563000277128180/?type=3&theater

why rail is a better alternative at times
https://www.facebook.com/130170407077838/photos/a.562900027138205.1073741854.130170407077838/562994580462083/?type=3&theater

GN and CB&Q box cars
https://www.facebook.com/130170407077838/photos/a.562900027138205.1073741854.130170407077838/562899987138209/?type=3&theater

before the bridge was built almost on top of this roundhouse
https://www.facebook.com/130170407077838/photos/a.562900027138205.1073741854.130170407077838/562900127138195/?type=3&theater

blast plates??? to prevent damage from steam locos???
https://www.facebook.com/130170407077838/photos/a.562900027138205.1073741854.130170407077838/562906873804187/?type=3&theater

Tim O'Connor