The NTSB said Tuesday that a loose cable caused a power outage on the 984-foot Dali freighter, leading to its March 2024 collision with Baltimore’s Francis Scott Key Bridge, which killed six construction workers and destroyed 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 blackouts on two vessels and a loss of propulsion and steering.
The National Transportation Safety Board, in its final findings on the cause of the accident, found that the cable tag bands prevented the cable from being fully inserted, causing an improper connection.
NTSB Chairwoman Jennifer Homendy compared the painstaking search for the cable 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 cables to find the problem, he added. “It’s like finding a needle in a haystack.”
The board also said contributing to the collapse was a lack of countermeasures to reduce the bridge’s vulnerability to ocean vessel impacts, which could have been implemented if the Maryland Transportation Authority had conducted a vulnerability assessment.
A replacement bridge was initially estimated to cost between $1.7 billion and $1.9 billion and be completed by the end of 2028. On Monday, state officials said they now expect the bridge to cost between $4.3 billion and $5.2 billion and open to traffic only in late 2030. They cited a new pier protection system and a new longer, taller design as reasons for the increased costs.
Board staff said they recommended operators complete periodic inspections of high-voltage switchboards and proposed changes that would allow ships to recover more quickly from a loss of power.
The NTSB has previously said that the Dali lost power several times before crashing into the Key Bridge, including a blackout during maintenance at the port and shortly before the accident.
Power outages can occur on the water, and the NTSB made numerous new recommendations to prevent catastrophic collisions, including to the U.S. Coast Guard. It also called on Hyundai Heavy to incorporate “proper wire tag band installation methods.”
In response to questions about the NTSB’s 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 outages, but “unfortunately, the owner and operator circumvented these safeguards.”
The company added that when it delivered the ship there was “no indication that any cables were loose” and said that if any cables became loose “over the course of a decade, due to vibration or otherwise, the owner and operator should have detected them in 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 entering the bridge in the event of a hazard.
Bridge Safety Assessment
In March, the board called for urgent 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 owners of major bridges consider adopting driver warning systems capable of activating when a threat is identified to immediately prevent drivers from entering the bridge in the event of 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 circuit breakers unexpectedly tripped, causing a loss of power to all onboard lights and most equipment when it was 1 kilometer from the bridge.
The FBI is conducting a criminal investigation into the collapse.
Homendy said some of the ship’s personnel are still in the United States.
