At around 1:27 in the morning of March 26, 2024, the Singaporean-flagged container vessel Darley collided with the Baltimore Bridge, which carries Route 695 across the 2 and 1/2 km span of the Patapsco River in Baltimore, Maryland.
Key Bridge Collapse: Causes of Darley Vessel Collision in Baltimore Bridge
The impact caused a chain reaction, leading to the bridge’s complete collapse within seconds. So what happened? How could a ship so easily collapse a bridge that stood in place for almost 50 years?
Throughout the evening of March 25, 2024, the container vessel Darly was alongside her berth at the southern end of the Sea-girt Marine Terminal, which is a massive facility in Baltimore capable of accommodating some of the world’s biggest ships. The Daily, for example, is around 300 meters long with a gross tonnage of just under 100,000 tons. Late in the evening, she completed the final checks for departure and was ready to get underway for her next passage towards Colombo, Sri Lanka.
It was a lovely evening with light winds from an east-to-north direction and minimal tide or flow as it was approaching low tide shortly after midnight. Now, on the 26th of March, she made fast two tugs, one forward and one aft, and with their assistance, came bodily to port off the berth. Once she had opened to a ship’s width or so from the key, she came ahead on her engines to get some water flowing over the rudder and prepare for the turn to port towards the main channel.
As the speed picked up to three or four knots or so, the two tugs lay alongside her on the port side and just ran with her as she completed her turn. By 1:10, the turn was complete, and Darly entered the main channel, at which point the tugs were standing down so that she could continue to pick up speed. When you’re working with tugs, you need to ensure you keep your speed down low because tugs are at massive risk of capsizing if you go too fast.
Anyway, with the tug standing down, Darly continued following the channel outbound, lining up for the main span under the Key Bridge, which is the only place large enough for these sorts of massive vessels to fit under. She continued to increase speed, reaching around 8.7 knots at 1:26 just before the bridge, but then something went wrong.
She started turning to starboard just around the same point where the Curtis Bay Channel joined the main channel. But why? Were there some interactive effects? Maybe, for example, if your starboard bow is no longer subject to pressure from a bank, it could cause a turn to starboard. If that did happen, though, the ship’s bridge is full of professionals who are more than capable of correcting it with some engine and rudder movements. So was there something else stopping them?
If, for example, the ship suffered some sort of power failure at that point, you would expect it to veer off under the effects of interaction at exactly the position where the underwater profile of the channel changes, like where another channel joins from the side. Either way, regardless of the reason for leaving the channel at that point, the crew knew there was a serious problem.
The tugs that had been standing down from the earlier maneuver sprang back to life and started heading back towards the Darly at full speed, but unfortunately, it was just too late. She was now so close to the bridge and carrying so much momentum that there was nothing anyone could do. At 1:29 local time on the 26th of March, she struck the southern tower, which just didn’t stand a chance against more than 100,000 tons of vessel and cargo traveling at 7 and 1/2 knots.
The collapse of the southern tower led to the collapse of spans on both sides of the river, which in turn led to the collapse of further spans as the chain reaction travelled along the bridge. Fifteen minutes later, at 1:43, the first tug arrived on the scene, but by then, the damage was already done. From that point on, the priority was search and recovery.