Since the cargo ship Dali collided with the Francis Scott Key Bridge in Baltimore, engineers have differed on whether anything could have been done to protect it, but they are clear that design standards have changed to protect bridges from ship collisions since the Key Bridge was built nearly 50 years ago. Its replacement will likely have more protection.
As many looked at the crumpled wreckage of the Key Bridge in awe, engineers the News4 I-Team talked to were looking at what was in place before the accident to protect the bridge from just that type of collision. In pictures and video of the bridge, large concrete circles in the water – called dolphins – are visible. Those columns extend to the bottom of the Patapsco River. They're designed to absorb the impact of an errant ship and hopefully slow it down enough to keep the support from taking a direct hit.
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The Key Bridge has two dolphins on either side but at some distance from the bridge supports. National Transportation Safety Board drone video shows when the Dali lost control, the nearly 1,000-foot-long ship didn’t even come in contact with those protective features before it collided with the bridge.
Bridge engineers tell the I-Team many protective features came about after the collapse of Tampa’s Sunshine Skyway Bridge on May 9, 1980. In that accident, a cargo ship blew off course in a storm and hit a bridge support, collapsing the bridge. Thirty-five people died.
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When that bridge was rebuilt seven years later, the new Skyway Bridge had dozens of protective dolphins. Additionally, the bridge supports are surrounded by islands, which extend underwater, designed to force a ship aground before a collision.
The safety of the bridge is now part of the NTSB investigation.
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“We look at changes over time, whether we look at bigger container ships or traffic on a bridge or whether a structure that may be decades old is safe,” NTSB Chair Jennifer Homendy told News4.
One hundred miles up the coast from Baltimore, the Delaware Memorial Bridge along Interstate 95 near Wilmington is in the middle of a three-year, $95 million safety upgrade.
“The structures themselves that are in the water to act as that bumper would absorb the impacts of the ship and keep it away from our tower,” Jim Salmon, a spokesperson for the Delaware River and Bay Authority told the I-Team.
In renderings of the new project, the protective features are placed closer to the Memorial Bridge than those at the Key Bridge and surround the piers from approaching ship traffic. The Delaware River and Bay Authority predicts if the same accident happened under their bridge once the system is complete, it would still be standing.
“We'd have significant damage to the fendering system, the new cylinders,” Salmon said, “but people will be still using the bridge.”
Engineers reminded cost is a key consideration in bridge planning. Collisions are rare, improvements are expensive, but every day the port is closed has a $10 million economic impact, said Daraius Irani, Ph.D., a Towson University expert.
The I-Team asked the Maryland Transportation Authority when the Key Bridge dolphins were installed but hasn't heard back.
