The bridge study came in response to two recent accidents. Left, in May 2002, an interstate bridge in Webbers Falls, Okla., collapsed after being struck by two barges pushed by a towboat; 14 people were killed. In September 2001, eight people died when a towboat pushing four barges hit the Queen Isabella Causeway Bridge in Texas.
The report, prepared by the Bridge Allision Work Group, made up of representatives from the U.S. Coast Guard and the American Waterways Operators, examined 2,692 barge-bridge allisions from 1992 to 2001 that occurred at 559 bridges nationwide.
“This is by far the most detailed analysis that’s ever been done” of bridge allisions by the Coast Guard, said Capt. Michael B. Karr, chief of the Coast Guard’s Office of Investigation and Analysis, who was part of the work group.
Of five major recommendations made by the Bridge Allision Work Group, three addressed problems with the location or safety of bridges. The group recommended that vulnerable bridges be identified, that the cost and benefits of adding protection to bridge piers be studied, and that the process for removing or altering “unreasonably obstructive bridges” already targeted by the Coast Guard be sped up.
Industry and government action can cut the occurrence of bridge allisions, but the risk cannot be reduced to zero. “Thus, additional actions by transportation authorities are needed to remove hazardous bridges and improve protection standards for bridges so that consequences from a bridge allision are minimized,” the report’s authors stated.
The study was triggered by two major barge-bridge collisions. On May 26, 2002, the towboat Robert Y. Love struck the Interstate 40 bridge in Webbers Falls, Okla., causing the span to collapse; 14 people died as a result. On Sept. 15, 2001, eight people were killed when a towboat pushing four barges struck the Queen Isabella Causeway Bridge in Texas.
“This industry had not had a fatal barge allision in nearly 10 years; then in a span of nine months, we had two,” said Jennifer Carpenter, senior vice president of government affairs for the AWO. “We said, â€˜Wait a minute; we’ve got to take a look at this; something is not right.'”
Carpenter was part of the AWO staff that worked with the group. The study did not address the I-40 and Texas incidents because both are still being investigated by the National Transportation Safety Board.
A Coast Guard-AWO Safety Partnership committee has been in place since 1995, working on industry issues, such as crew alertness, deck hands falling overboard and barge transfer spills. In June 2002, an ad hoc group, under the auspices of the safety partnership, began examining all bridge allisions involving towing vessels and barges for the past decade. The Bridge Allision Work Group consisted of 19 people: nine from the Coast Guard and 10 from the towboat industry, with staff support from both the AWO and the Coast Guard. This group will meet again on Aug. 6, to decide which recommendations will be addressed first, according to Karr.
Of the 2,692 bridge allisions studied, 52 percent involved highway bridges, and 48 percent involved railroad bridges. But when it came to the more serious collisions, incidents that involved damage over $500,000, injuries, pollution or a fatality, 63 percent of the allisions involved highway bridges, compared with 37 percent involving railroad bridges.
The report found that the bridges hit the most were not the ones with the highest vessel traffic. The areas of the country that had the most frequent allisions, based on Coast Guard Marine Safety Office locations were: Davenport, Iowa; Chicago; Morgan City, La.; and Mobile, Ala. Each reported at least 320 incidents. There was no correlation between the time of day and allisions, according to the report.
The work group did not have enough resources to analyze specific causes behind all 2,692 incidents, so it focused on 459 allisions. In this set, 78 percent were caused by pilot error, and 12 percent were caused by other operational errors, such as miscommunication by a deck hand at the head of the tow. Only 5 percent were caused by mechanical problems.
“I was surprised at how few of the allisions were attributable to loss of propulsion or loss of steering,” Karr said.
In order to compare the number of allisions with the total number of towboat and tugboat trips, the group looked at data for the Mississippi River in 2000. In this period, there were about six allisions for every 10,000 vessel towing trips. The 70 deaths caused by barge-bridge allisions since 1992 were the result of just four incidents.
The report made several recommendations for pilot training, such as developing practices for transiting bridges that are vulnerable to allisions and requiring route familiarization, posting and having new captains ride with senior captains before being allowed to navigate alone under a vulnerable bridge.
The Coast Guard plans to work with the AWO and use this data to identify hazardous bridges that would become part of a national database available for towboat and tugboat operators, Karr said. The group recommended that the Coast Guard, over the next three to five years, perform more in-depth investigations to gather as much data as possible for selected allisions involving human error.
The recommendation to identify bridges that are particularly vulnerable does not just apply to bridges that have been hit, Carpenter said. “To the extent we can, we can try to identify bridges that would be vulnerable to catastrophic results when hit,” Carpenter said. For example, the I-40 bridge in Webbers Falls had not been hit before, so it would not have been on a list of vulnerable bridges, she said.
The report recommended that the costs and benefits of providing additional protection for vulnerable bridges also be studied.
Identifying bridges that are susceptible to collapse when struck remains key to this problem, according to bridge experts. “It comes back to assessing which the most vulnerable ones are, and dealing with them in some sort of priority,” said Michael A. Knott, a vice president at Moffatt & Nichol Engineers, in Norfolk, Va., and an internationally known authority on the science of risk analysis for bridge collapse. “We have the methods and the tools to identify the ones that are the most vulnerable.”
One federal program does exist to fix bridges that are deemed an obstruction to navigation, but it is underfunded. The Truman-Hobbs Act is designed to identify bridges that obstruct navigation and to provide funds to fix them. A bridge would be a candidate for repair or removal under the act because of “insufficient height or width of the navigation span” or because of “difficulty in passing through the draw opening.” There is dedicated federal funding for this program, which is used for both highway and railroad bridges.
However, 918 allisions in this study occurred at bridges that were already scheduled for alteration or removal under the Truman-Hobbs Act. Of that group, 256 allisions took place at bridges that were on the backlog priority list. Between 1992 and 2001, the average amount the Coast Guard received from this program was $11.6 million, according to the report. The amount of money needed for bridges already on the list is $284 million, and funding has not been provided for these projects.
Accelerating the removal or alteration of Truman-Hobbs bridges is another recommendation of the bridge group. “There has not been sufficient attention paid to bridges that we know have problems,” Carpenter said.