I was still in Norfolk, Va when they replaced the Coleman Bridge, that connects Yorktown with Gloucester Point. The old span was a 2 lane swing bridge and was to be replaced with a 4 lane. The folks that lived in Gloucester and worked in places south of the river were to have 60 miles extra to drive during the replacement process.
The bridge was constructed on top of pilings just south of the Naval Base. It was built in 6 sections, with each one already paved, wired and plumbed. When it was complete, the sections were floated off the pilings and onto barges and moved up to the site by tugs. The old bridge was lifted in a similar manner and moved out of the way.
Once the new bridge was in position, the wires and pipes were connected so that the pre-fabbed unit was ready for service. Due to the inconvenience of the process, the State had allowed the construction company 30 days for the procedure. They completed the bridge swap in 8.
The old bridge was taken back down to the construction site and placed onto the pilings. Charges were placed and they dropped the old one into the water. It's much easier salvaging that way.
I was still running a tug at the Naval Base and got to see a lot of this up close. It was amazing to me that they would even think of this, let alone swapping out those bridges in just 8 days. VDOT made a video of the whole thing and I used to have a copy. I looked for it and don't know what I did with it.