The derailment took seven tanker cars off the rails and sent four into the creek. One of the cars that fell into the water ruptured, spewing its cargo of toxic vinyl chloride into the air and forcing the evacuation of nearly 700 people for several days.
Repair efforts were under way even as cleanup crews worked to remove the derailed cars, Coast Guard spokeswoman Cindy Oldham said, offering an explanation for the bridge's apparently rapid return to service.
The train derailed Nov. 30 after it was permitted to go through a red signal that indicated a possible problem with the mechanism that locks the rails in place on the swing bridge.
The locking mechanism aligns the bridge tracks with those on shore and secures the bridge to its abutment. All four locks have to be in place for electronic sensors to trigger a green signal.
The engineer of the Conrail train that derailed used an electronic keypad to try to get the green signal, but could not. Then the conductor walked the bridge and reported that it looked secure, and the engineer asked for and received permission from a dispatcher in Mount Laurel to proceed.
Workers laid "new solid rail to lock the bridge in place," Coast Guard spokesman Drew Madjeska said Monday.
Once FRA officials determined that the locking mechanism and the rails were secure, they cleared the bridge for operation, he said.
An FRA spokesman said "the timing of this inspection was typical for bridge inspections."
The resumption of rail activity came after about 30 businesses pressed officials on Friday to explain how they would determine which would receive priority shipments.
"At this point, I think we can heave a little bit of a sigh of relief, because we do have product moving along the rail," said Heather Simmons, a member of the Gloucester County Board of Freeholders, which organized the meeting between businesses and the unified command leading the cleanup effort. "But there's still a backlog."
According to a trade group, two Salem County plants, OxyVinyls and PolyOne Corp., which use vinyl chloride in their manufactures, suspended operations after the derailment because they ran out of the chemical.
It was not immediately clear Monday whether the plants had reopened; neither the trade group, the Chemistry Council of New Jersey, nor the companies responded to requests for an update.
Paulsboro residents had lambasted officials leading the cleanup efforts for everything from a lack of communication to arbitrary decisions for where to draw evacuation boundaries.
At least one remained skeptical Monday that the bridge was safe to operate.
"My question with this: How could they get the last tanker out of the water . . . and then have the rail repaired and adequately inspected by Sunday afternoon?" asked James McGovern, a 64-year-old registered nurse from Paulsboro.
Contact Andrew Seidman at 856-779-3846, firstname.lastname@example.org or @AndrewSeidman on Twitter.