They're replacing the old two-track girder bridge with one that's wider, giving CSX trains more clearance between Tracks 2 and 3. They're also going to make it and the single-track bridge on the opposite side, which carries Track 1, a little higher to give NS more clearance. (One wonders for what: Stack trains?) Finally, they're shoring up each end of the CSX railroad's high earthen fill with steel piles because the new bridge will be longer and heavier.
The shoring-up has begun. You can see it in one or more of the pictures below. To replace the bridge, they're going to erect a kind of heavy-duty "scaffold" framework parallel to the old two-track bridge, the one next to the crane. Once the scaffold is completed, they will begin assembling the new bridge on top of that scaffold. To move the finished bridge, bogeys will be slipped under it so it can be rolled sideways along the steel framework, which will be grooved to provide a guideway. Portable, gas-powered (I think) hydraulic machines rigged with cables will be used to tow the new bridge over.
On D-Day ("T-Day"?), scheduled to take place next April, both CSX and NS will shut down their affected tracks above and below for four days, leaving one track per railroad in service. The monster red crane will lift the old two-track bridge out of its supports and place it aside. Then the new bridge will be rolled into its new spot. Once there it can be jacked up, bogeys removed, and jacks eased off so the bridge can settle into place.
Finally, the old single-track bridge will be jacked up to a new altitude, but I don't recall what will be done next. Something will have to be inserted under it to keep it in its higher location.
After work site clean-up, Pete said, "We can all go home."
After my meeting with Pete in the construction office, I came outside to discover a couple of CSX "suits" (black suits, to be exact--probably accounting types) had shown up for a tour: