Comments about technological history, system fractures, and human resilience from James R. Chiles, the author of Inviting Disaster: Lessons from the Edge of Technology (HarperBusiness 2001; paperback 2002) and The God Machine: From Boomerangs to Black Hawks, the Story of the Helicopter (Random House, 2007, paperback 2008)

Saturday, February 4, 2012

Delta Mariner, Abridged: Structure's navigational lights under scrutiny

Here's an update on the Delta Mariner allision, in Q & A format.

          Is the ship still anchored at the site?
Yes, but not for long. From the Paducah Sun, here's a shot taken pointing southeast, taken earlier this week:
The salvage barge in the photo is ready to start removal of the bridge wreckage today, now that the USCG has approved the salvage plan.

          Where did it happen?
Delta Mariner hit a two-lane highway bridge crossing the Kentucky Lake Reservoir, a dammed portion of the Tennessee River. The old name of the bridge is Eggner's Ferry; on maps, it's the US 68/KY 80 bridge. The location of the mishap is the second span from the east, called Span E, three spans east from the main navigation channel, which from the images I am guessing is called "Span B." A slide show of images is here, at the West Kentucky Star. The main channel is the one that Delta Mariner should have used since it offers the highest clearance. As is painfully obvious now, Span E over the recreational channel was a Siren's call. My notes on this AP Photo for which span is which:
          The area has been mostly closed to the public. Can I get a look at it?
For a few hours today (Saturday), there will be a one-time opportunity, for people to hop in their cars and go to the Fenton camping area and see the damage at a distance. The entire area will be cordoned off again after that. Check your local news or this Land Between the Lakes website before setting out, in case salvage work has changed the schedule.

          What was Delta Mariner carrying?
  • Atlas first stage for the second geosynchronous satellite in the Advanced Extremely High Frequency (AEHF) military-communications system for USAF's Space Command
  • Centaur second stage, also for AEHF-2
  • Interstage adapter, for the Radiation Belt Storm Probes (RBSP) mission for NASA
We are told none of the cargo sustained damage.

          Is Delta Mariner a ship, or a barge, or what?
It's an ocean-going, self-propelled Roll-on, Roll-off ship, abbreviated RORO. The biggest stages are carried in a hangar-like structure in the center of the ship. After leaving the river network it takes rockets east to Cape Canaveral, Florida; or else south to transit the Panama Canal, then back north to Vandenberg AFB near Lompoc, CA.

          Has anything like this happened before?
WSMV referenced a November 2011 mishap in which a much smaller vessel hit a bridge support after taking the wrong channel. No significant damage resulted.

          Did Delta Mariner have a Voyage Data Recorder?
I speculated in the previous post that it probably did, given the vessel's work for NASA and the high-value cargo. The NTSB has sent data-recovery specialist Michael Bauer to the ship so Delta Mariner must have some kind of forensic logger on board, maybe a simplified voyage data recorder, or S-VDR. If so, it should have saved a recording of the bridge audio.

          Why did Delta Mariner hit the bridge?
No information from the USCG investigation is yet public. Even though the ship had one and perhaps two river pilots on board at the time, it was almost a thousand feet from the main channel -- which seems like a lot. In the direction that Delta Mariner was going (north), the correct channel to take is the one under the second span from the left side; instead it took the channel under the second span from the right side. It almost suggests uncertainty on the bridge about whether the ship was bearing north or south.

That's hard to believe, though, and more plausible reasons include impaired visibility, since it was dark and raining, and perhaps foggy. Problems with navigational aids might have contributed: Some of the bridge navigation lights were reported to be out of commission beforehand. Lighting repair work on the bridge was scheduled for the next day.

          What are bridge navigation lights?
The Coast Guard specifies a lighting plan for bridges on navigable waterways, marking the channels to use. Here's the generic upstream lighting plan for fixed-span bridges with main and alternate channels; Eggner's Ferry Bridge is in that class.
I haven't seen lighting details for this particular bridge, but if the diagram reflects the requirements, the center of the main channel is supposed to be marked with three vertical lights on the bridge, typically white. If the bridge lights on the side visible to Delta Mariner were burned out, that could have been a contributing cause.

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