Finding out what caused last month's train derailment and fire in the CSX tunnel beneath the heart of Baltimore may turn out to be one of the most difficult challenges ever faced by the National Transportation Safety Board, experts say.
The five-day fire and the process of fighting it destroyed or altered evidence investigators typically rely on to determine the causes and consequences of rail accidents.
One investigator characterized the wreck July 18 of the 60-car, chemical-bearing CSX train in the Howard Street tunnel as a "Murphy's Law" sort of accident and aftermath, where anything that could go wrong did. Rail cars were moved from their crash positions, new debris was carried onto the site, and the fire consumed cargo and affected the track and tunnel in ways that tainted the scene for investigators.
"It's something we can't help, unfortunately, but that can destroy clues that may have been important to us," said NTSB spokesman Keith Holloway. "And that can lengthen the investigation and put more roadblocks in front of us."
With no one injured in the Baltimore wreck and CSX traffic through the tunnel returning to normal, the challenge of finding out just what happened might seem less urgent than an investigation of a plane wreck that took hundreds of lives.
But investigators and safety experts say finding out what happened beneath Howard Street last month is imperative if they are to avoid more serious consequences in future mishaps. Indeed, rail accidents have been rising steadily since 1997.
"If there is something that can be learned from this, you'd like to know about it as quickly as possible," said Wyman Jones, an engineer who teaches accident investigation for the Transportation Safety Institute. "Could this happen elsewhere on the system? I'd want to know what caused it in case it is endemic to the whole rail system."
Ordinarily, the positions of cars and wheels in derailments yield valuable evidence of how such accidents occurred. In addition, scrapes and bends in the rails can reveal defects. Wood ties are studied for signs of weakness in the track. When tunnels are involved, the structures are inspected for deterioration that might have contributed to an accident.
In this case, many of those clues went up in smoke or were at least cast into doubt.
Entirely concealed from view by the tunnel, the train wreckage was inaccessible for days because of a double whammy -- a chemical spill complicated by fire.
Examining the position of the wreckage was never an option because the cars were removed in small groups so firefighters could close in on the blaze.
"Normally you go up to a site and the equipment is laying there and you can generally tell where the exact point of derailment is," said George Gavalla, head of safety for the Federal Railroad Administration. "We don't have that luxury here because the cars were pulled out of the tunnel before we had a chance to look at them."
"It will affect our ability to re-create and see all the evidence as it happened," said Gavalla.
By comparison, consider the collision Aug. 3 between two transit trains that injured more than 200 people in Chicago. Exposed on an elevated track that made it easy for investigators to inspect from any angle, the train cars were still in place 10 days later as the NTSB team methodically measured, photographed and calculated.
In Baltimore, removing the cars from the tunnel did more than just eliminate the chance for investigators to see how the train came to rest. It unavoidably created more marks on the rails, rail bed and cars, and introduced fresh debris at the accident site.
With lives potentially at stake, there was no choice, all agree.
"But when you do all that, you contaminate the scene," said Jones, of the Transportation Safety Institute. "Now it becomes twice as hard for an investigator to re-create what happened."
Creosote-soaked rail ties were incinerated by the blaze too, posing other difficulties. "If there were problems with the ties, the fire is going to impede our ability to identify that as a contributing factor," said one investigator, who spoke on condition that he not be named.
In addition, the blaze consumed the contents of some cars, inhibiting efforts to check the weight of loads at the time of the accident.
Affected too will be the assessment of tunnel conditions. The investigator described fractures and fist-sized holes in the walls of the tunnel. The NTSB has publicly acknowledged finding "earthy" rock-like debris on the tops of some train cars that were located well in front of the derailment point, suggesting that a portion of the tunnel might have fallen onto the train or tracks and contributed to the accident.
But the length and intensity of the blaze inside the tunnel is likely to complicate reaching such a conclusion, according to the investigator. The extreme temperatures produced by the fire could have caused mortar to expand and contract, he said.
That's what happened in 1996 after an explosion on a train carrying flammable cargo through the Channel Tunnel between England and France. The fire burned so hot that it caused concrete inside the tunnel to explode.
"If not for the fire, you could say, 'Yes, some material might have fallen from the ceiling onto the track in Baltimore,'" the investigator said. "But because of the high temperatures generated by the fire, I don't know if the problems we saw in the tunnel were due to the intense heat or existed prior to the event."
The accounts of the crew will be particularly important in the absence of other evidence, said Jim Tucci, an independent investigator hired by the state. "Maybe the engineer felt the train drag or the wheels lock up, and that's when he stopped his train," he said.
And Tucci said track-related documents and tunnel inspection reports could be key.
The five-day fire and the process of fighting it destroyed or altered evidence investigators typically rely on to determine the causes and consequences of rail accidents.
"It's something we can't help, unfortunately, but that can destroy clues that may have been important to us," said NTSB spokesman Keith Holloway. "And that can lengthen the investigation and put more roadblocks in front of us."
With no one injured in the Baltimore wreck and CSX traffic through the tunnel returning to normal, the challenge of finding out just what happened might seem less urgent than an investigation of a plane wreck that took hundreds of lives.
But investigators and safety experts say finding out what happened beneath Howard Street last month is imperative if they are to avoid more serious consequences in future mishaps. Indeed, rail accidents have been rising steadily since 1997.
"If there is something that can be learned from this, you'd like to know about it as quickly as possible," said Wyman Jones, an engineer who teaches accident investigation for the Transportation Safety Institute. "Could this happen elsewhere on the system? I'd want to know what caused it in case it is endemic to the whole rail system."
Ordinarily, the positions of cars and wheels in derailments yield valuable evidence of how such accidents occurred. In addition, scrapes and bends in the rails can reveal defects. Wood ties are studied for signs of weakness in the track. When tunnels are involved, the structures are inspected for deterioration that might have contributed to an accident.
In this case, many of those clues went up in smoke or were at least cast into doubt.
Entirely concealed from view by the tunnel, the train wreckage was inaccessible for days because of a double whammy -- a chemical spill complicated by fire.
Examining the position of the wreckage was never an option because the cars were removed in small groups so firefighters could close in on the blaze.
"Normally you go up to a site and the equipment is laying there and you can generally tell where the exact point of derailment is," said George Gavalla, head of safety for the Federal Railroad Administration. "We don't have that luxury here because the cars were pulled out of the tunnel before we had a chance to look at them."
"It will affect our ability to re-create and see all the evidence as it happened," said Gavalla.
By comparison, consider the collision Aug. 3 between two transit trains that injured more than 200 people in Chicago. Exposed on an elevated track that made it easy for investigators to inspect from any angle, the train cars were still in place 10 days later as the NTSB team methodically measured, photographed and calculated.
In Baltimore, removing the cars from the tunnel did more than just eliminate the chance for investigators to see how the train came to rest. It unavoidably created more marks on the rails, rail bed and cars, and introduced fresh debris at the accident site.
With lives potentially at stake, there was no choice, all agree.
"But when you do all that, you contaminate the scene," said Jones, of the Transportation Safety Institute. "Now it becomes twice as hard for an investigator to re-create what happened."
Creosote-soaked rail ties were incinerated by the blaze too, posing other difficulties. "If there were problems with the ties, the fire is going to impede our ability to identify that as a contributing factor," said one investigator, who spoke on condition that he not be named.
In addition, the blaze consumed the contents of some cars, inhibiting efforts to check the weight of loads at the time of the accident.
Affected too will be the assessment of tunnel conditions. The investigator described fractures and fist-sized holes in the walls of the tunnel. The NTSB has publicly acknowledged finding "earthy" rock-like debris on the tops of some train cars that were located well in front of the derailment point, suggesting that a portion of the tunnel might have fallen onto the train or tracks and contributed to the accident.
But the length and intensity of the blaze inside the tunnel is likely to complicate reaching such a conclusion, according to the investigator. The extreme temperatures produced by the fire could have caused mortar to expand and contract, he said.
That's what happened in 1996 after an explosion on a train carrying flammable cargo through the Channel Tunnel between England and France. The fire burned so hot that it caused concrete inside the tunnel to explode.
"If not for the fire, you could say, 'Yes, some material might have fallen from the ceiling onto the track in Baltimore,'" the investigator said. "But because of the high temperatures generated by the fire, I don't know if the problems we saw in the tunnel were due to the intense heat or existed prior to the event."
The accounts of the crew will be particularly important in the absence of other evidence, said Jim Tucci, an independent investigator hired by the state. "Maybe the engineer felt the train drag or the wheels lock up, and that's when he stopped his train," he said.
And Tucci said track-related documents and tunnel inspection reports could be key.
