(The following story by William Petroski appeared on the Des Moines Register website on September 19.)
DES MOINES, Iowa — Burlington’s Great River Bridge, which carries 10,000 vehicles daily over the Mississippi River between Iowa and Illinois, is among 44 cable-stayed bridges nationally that have created worries for the U.S. Department of Homeland Security.
Federal officials said they are concerned the large bridges could be inviting targets for terrorists, according to a report in USA Today. Homeland Security workers have been working with the U.S. Army Corps of Engineers to find ways to shield the cables and connections from explosives, officials told the newspaper.
“These are attractive structures,” said Mary Ellen Hynes, a research chief in the department’s Science and Technology Division. “Terrorists are out there, they’re blowing up bridges in Iraq, and we need to be preparing ourselves to make sure we protect our bridges and our people.”
The concerns about terrorism apparently haven’t been passed on to the Burlington Police Department. The law enforcement agency isn’t taking any special steps to protect the Great River Bridge, said Lt. Steve Bell, a police department spokesman.
“No, nothing out of the routine or the normal,” Bell said. “You can see the bridge from the police department. It’s, like, three blocks away from us. You can look out the back window of the building and see the bridge over the river.”
The Great River Bridge, which opened in 1993 – replacing the old MacArthur toll bridge – is Iowa’s only cable-stayed bridge, said Dena Gray-Fisher, spokeswoman for the Iowa Department of Transportation. The structure was built at a cost of $48.9 million. The bridge is 2,800 feet long, including approach spans, and its single cable tower is 374 feet tall. The main span is 660 feet long.
“We are looking at some surveillance, and I am not going to get into specifics, because we don’t want to talk about security risk assessment issues,” Gray-Fisher said.
The 44 cable-stayed bridges are in 24 states and Puerto Rico. Such bridges are known for their sail-like design and long spans that can handle lots of traffic. They cross the Charles River in Boston, Tampa Bay in St. Petersburg, Fla., the Ohio River in Rockport, Ind., and many other bodies of water.
One of the concerns is that, unlike suspension bridges, cable-stayed spans have only one set of cables that connect directly to a highway. That gives anyone aiming to weaken or take down a bridge with explosives ready access to key parts of the structure holding it up, USA Today reported.
Iowa DOT officials have been looking at ways to fortify the Great River Bridge, particularly the cables, as well as at alternatives to repair damage and to restore service in event of a terror attack, Gray-Fisher said. It’s part of a process that began after the Sept. 11, 2001, terrorist attacks, and it has involved bridges across the state, she said.
“We are very aware. We are very persistent,” Gray-Fisher said. “We have looked at (that) when we are building new, and we have looked at the existing structures that we have, and what type of security risk assessments are necessary.”
In 2003, railroad bridges at Clinton and Fort Madison were placed under around-the-clock guard against terrorism as part of Operation Liberty Shield. The two railroad bridges, used daily by dozens of freight trains crossing the Mississippi River, were watched on the Iowa side for about one month by a force of National Guard troops and state and local law enforcement officers. The bridges were among 250 national critical assets that federal officials said needed additional protection.
The Iowa Division of Homeland Security and Emergency Management has developed a list of about 1,100 “critical assets” statewide, said David Miller, the division’s administrator.
The list includes assets in 17 sectors, covering areas such as transportation, communications, energy, emergency services, agriculture and banking.
“The bulk by far are privately owned,” Miller said.
Iowa was ahead of other states in identifying potential terror targets after former Gov. Tom Vilsack asked state officials to address the issue in the wake of the Sept. 11 terror attacks, Miller said.
During the past couple of years, state and federal officials have worked to refine Iowa’s list, he said.