The NTSB said Tuesday that a loose wire caused a power failure on the 984-foot freighter Dali, leading to its March 2024 collision with Baltimore’s Francis Scott Key Bridge, killing six construction workers and destroying the span.
The investigation found that a single loose wire in the electrical system caused a circuit breaker to open unexpectedly, triggering a sequence of events that led to two vessels losing power and losing propulsion and steering.
The National Transportation Safety Board, in its final conclusions on the cause of the accident, found wire-label strips prevented the wire from being fully inserted, causing an inadequate connection.
NTSB Chair Jennifer Homendy compared the painstaking search for the wire to finding a single loose rivet on the Eiffel Tower. The NTSB and the ship’s manufacturer HD Hyundai Heavy 329180.KS had to test thousands of wires to find the problem, she added. “It’s like finding a needle in a haystack.”
The board also said that contributing to the collapse was the lack of countermeasures to reduce the bridge’s vulnerability from impacts from ocean-going ships, which could have been implemented if a vulnerability assessment had been conducted by the Maryland Transportation Authority.
A replacement bridge was originally estimated to cost $1.7 billion to $1.9 billion and be completed by the end of 2028. On Monday, state officials said they now expect the bridge to cost $4.3 billion to $5.2 billion and not open to traffic until late 2030. They cited a new pier protection system and a new longer, taller design as reasons for the increased cost.
Board staff said they recommended operators conduct periodic inspections of high-voltage switchboards and suggested changes that would allow ships to recover more quickly from a power loss.
The NTSB previously said the Dali lost electrical power several times before crashing into the Key Bridge, including experiencing a blackout during port maintenance and shortly before the crash.
Power outages can happen on the water, and the NTSB made several new recommendations to prevent catastrophic collisions, including to the U.S. Coast Guard. It also urged Hyundai Heavy to incorporate “proper wire-label banding installation methods.”
In response to questions about the NTSB findings, HD Hyundai said in a statement that it delivered a safe, seaworthy vessel in 2015 with automated systems and critical redundancies to quickly respond to power outages, but “unfortunately, the owner and operator bypassed these safety measures.”
The company added that when it delivered the vessel, “there was no indication that any wire was loose” and said that if a wire were to come loose “over the course of a decade, through vibration or otherwise, the owner and operator should have discovered it during a routine inspection and through normal maintenance.”
The key bridge, like many other bridges, was not equipped with a warning system to prevent motorists from driving onto the bridge in case of danger.
Assessment of bridge safety
In March, the board called for rapid safety assessments of 68 bridges in 19 states, including crossings such as the Golden Gate Bridge, Chesapeake Bay Bridge, Brooklyn Bridge and George Washington Bridge. The NTSB recommended Tuesday that major bridge owners consider adopting driver warning systems capable of activating when a threat is identified to immediately stop drivers from entering the bridge in an emergency.
The review focused on bridges built before 1991 and frequented by ocean-going vessels that have not undergone vulnerability assessments.
The NTSB said last year that the Dali lost power about four minutes before the crash when electrical breakers unexpectedly tripped, causing a loss of power to all onboard lighting and most equipment when it was 0.6 miles (1 km) from the bridge.
The FBI is conducting a criminal investigation into the collapse.
Homendy said some of the ship’s crew are still in the United States.
