Investigators are looking into a pair of “mechanically distinct” outages aboard the Dali while it was in port at Seagirt Marine Terminal, and whether they were coincidental or connected to the later outages before the ship struck and collapsed the Francis Scott Key Bridge, National Transportation Safety Board Chair Jennifer Homendy told Congress on Wednesday.

Investigators are still unsure of the exact cause of the two outages after the ship left port that caused the fatal collision, Homendy said.

In particular, Homendy said, investigators are scrutinizing the crew’s decision to reconfigure the electrical breakers that regulates the power systems on the ship 10 hours before it departed. After the outages at port, the crew activated two different breakers that had not been in use for months and a new transformer. When the Dali left port, those newly engaged breakers were still in use, according to the preliminary report.

The switching of equipment “may have affected operations the very next day on the accident voyage,” Homendy said. “The configuration of the breakers remains under investigation.”

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Homendy’s testimony came one day after the National Transportation Safety Board released a preliminary report on the cause of the catastrophe that claimed six lives and closed the Port of Baltimore to vessel traffic.

In the early morning hours of March 26, the 984-foot freighter Dali lost power twice and went adrift as it approached the Key Bridge, striking one of the piers supporting the span, and toppling it in seconds. Six workers on the bridge were killed. The disaster essentially cut off the port from the rest of the world, putting on hold the economic activity and jobs generated by the port, and severed a major Baltimore artery used by trucks and commuters.

Homendy was joined by representatives from the U.S. Coast Guard, the U.S. Army Corps of Engineers and the Federal Highway Administration. The group appeared before the U.S. House Committee on Transportation and Infrastructure and answered questions, providing the second update to Congress on the ongoing investigation. Administrator Shailen Bhatt represented the FHA; Vice Adm. Peter Gautier represented the Coast Guard; and Maj. Gen. William “Butch” Graham represented the USACE.

Bhatt primarily answered questions about funding for the federal response and the planned reconstruction of a replacement bridge, in particular about money that might come from insurers. Bhatt indicated replacement cost of the bridge to be at least $1.7 billion and gave 2028 as an estimated time of completion. Gautier emphasized a need to examine bridge protection around the country and gave examples of some measures that could be taken.

Homendy provided the bulk of pertinent information related to the probe. She urged authorities to conduct “risk assessments” on all the bridges in the U.S. to be examined for potential vulnerabilities to strikes by ships.

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“They don’t need to wait for the conclusion of our report,” she said.

Homendy estimated a final report will take 18 months to complete, but added the NTSB could provide updates before then as well as issue urgent safety recommendations.

The design of the nearly 50-year-old bridge made it especially susceptible to collapse, Homendy has previously stated.

The NTSB and Coast Guard both have active safety investigations into the bridge collapse. On Tuesday, the NTSB released its preliminary report into the catastrophe, which verified the Dali suffered two power outages in the hours before it set sail.

Wreckage from the collapsed Francis Scott Key Bridge is seen on top of the cargo ship Dali from a boat in the Patapsco River on April 25, 2024. (Ulysses Muñoz/The Baltimore Banner)

One outage was the result of human error: A crew member wrongly closed an exhaust damper, which caused the ship’s engine to stall, according to the NTSB report. That, in turn, caused a generator to go offline and the ship’s breakers to trip. A second outage followed when a backup generator experienced low fuel pressure.

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However, the report did not identify why the ship lost power on its approach to the Key Bridge. The report appeared to rule out contaminated or “dirty” fuel as a possible cause for the blackout just before the bridge strike.

Homendy told the committee all the fuel on the ship was tested by an independent lab, and the results “did not identify any concerns regarding the quality of the fuel.”

Absent from Wednesday’s hearing was the FBI, which last month launched its own criminal probe into the collapse and raided the Dali. The status of that investigation is unclear.

A construction crew of immigrants was repairing potholes on the bridge at the time of the collapse, and six of them died. A seventh was rescued from the water.

When asked about emergency protocols in place for the Key Bridge, Homendy expressed confidence in the response time, emphasizing that only 52 seconds elapsed between the time the pilot’s dispatcher notified the Maryland Transportation Authority Police and when the bridge was closed. She also noted how little warning the ship’s crew had, pointing out the time between the ship’s final blackout and the collision was only four minutes.

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An April 10 Senate hearing made clear that transportation officials were focused on the Dali’s electrical systems. The NTSB flew representatives from Hyundai — the company that built the ship — to Baltimore to help in the retrieval of data from its engine room.

A Baltimore Banner review of Coast Guard data found that more than 100 cargo ships have experienced engine trouble in and around the Port of Baltimore and Chesapeake Bay, including some that came perilously close to the Key Bridge and Chesapeake Bay Bridge.

Maritime experts have said that a total loss of power like the Dali experienced before hitting the Key Bridge is relatively rare when compared to the number of ships that transit ports on a daily basis.

Correction: This story has been updated to correct the spelling of the Francis Scott Key Bridge.

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