EXPLAINER-Why did the Baltimore bridge collapse and what is the death toll?

The Francis Scott Key Bridge was one of three ways to cross the Baltimore Harbor and handled 31,000 cars per day or 11.3 million vehicles a year. The steel structure was four lanes wide and rose 185 feet (56 m) above the river.

Work is underway to begin clearing the wreckage of Baltimore's Francis Scott Key Bridge a week after a cargo ship crashed into it, sending the span crashing into the harbor and killing six construction workers. Replacing the bridge will likely take years, but authorities are working on opening a temporary alternate channel that will be 11 feet (3.4 meters) deep to allow some vessels through. President Joe Biden will visit Baltimore on Friday.

WHAT IS THE DEATH TOLL? The six victims of the bridge collapse were all immigrants from Mexico and Central America who were fixing potholes on the bridge on March 26. Divers recovered the bodies of two men the following day. They were identified as Alejandro Hernandez Fuentes, 35, of Baltimore, originally from Mexico, and Dorlian Castillo, 26, of nearby Dundalk, originally from Guatemala.

Authorities have not yet recovered the bodies of the other four men in the 50-foot-deep (15 m) waters surrounding the twisted ruins due to treacherous conditions. They are Maynor Suazo from Honduras; Jose Lopez from Guatemala; Miguel Luna from El Salvador; and another whose name has not been released. Two other workers were rescued. Authorities saved lives by stopping vehicles from using the bridge after the ship sent out a mayday call.

The ship also dropped its anchors to slow down, buying time to clear the bridge. WHEN DID THE BALTIMORE BRIDGE COLLAPSE?

Shortly after 1 a.m. EDT (0500 GMT) on March 26, a container ship named the Dali was traveling down the Patapsco River on its way to Sri Lanka. At 1:24 a.m., it suffered a total power failure and all its lights went out. Three minutes later, at 1:27 a.m., the container ship struck a pylon of the bridge, crumpling almost the entire structure into the water.

Less than a minute before impact, a first responder on emergency radio responded to the crew's mayday call by sending officers to halt traffic onto the bridge. Without their fast work, the scale of the disaster may have been far greater, even during the early morning hours when vehicular traffic is relatively light.

The disaster may be the worst U.S. bridge collapse since 2007, when a design error caused the I-35W bridge in Minneapolis to plunge into the Mississippi River, killing 13 people. WHY DID THE BRIDGE COLLAPSE? Bridges such as the one in Baltimore are classified as "fracture critical" by the federal government - meaning that if one portion of the bridge collapses, the rest of the structure falls. There are more than 16,800 such spans in the U.S., according to the Federal Highway Administration.

The head of the National Transportation Safety Board said the bridge lacked structural engineering redundancies common to newer spans, making it more vulnerable to catastrophic collapse. The Key Bridge opened in 1977 - three years before a similar vessel collision of the Sunshine Skyway Bridge in Tampa Bay, Florida, killed 35 people, and prompted bridge designers to implement better protections for foundation piers.

WHO WILL PAY FOR THE DAMAGE AND HOW MUCH WILL THE BRIDGE COST? President Joe Biden will visit Baltimore on Friday and has said he wanted the federal government to pay to rebuild the bridge. The Transportation Department on March 28 awarded $60 million in "quick release" emergency relief funds to aid in clearing debris and begin the process of rebuilding. To replace the bridge, Congress would need to approve funding. After the bridge collapse in 2007 in Minnesota, Congress allocated $250 million. Initial estimates put the cost of rebuilding the bridge at $600 million, according to economic analysis company IMPLAN.

Federal officials have told Maryland lawmakers the final cost of rebuilding the bridge could soar to at least $2 billion, Roll Call reported, citing a source familiar with the discussions. Insurers could face billions of dollars in claims, analysts said, with one putting the cost at as much as $4 billion, which would make the tragedy a record shipping insurance loss. HOW LONG WILL IT TAKE TO REBUILD THE BRIDGE? Rebuilding could be a lengthy process and will depend on whether any of the remaining structure can be salvaged. It took five years to construct the original bridge from 1972-1977.

The closure of the port for just one month would cost Maryland $28 million in lost business, according to IMPLAN. Authorities are preparing to establish a temporary channel on the northeast side of the main shipping lane to allow essential vessels through.

WHAT SHIP HIT THE BALTIMORE BRIDGE? The Dali was leaving Baltimore en route to Colombo, Sri Lanka, with 21 crew and two pilots on board.

The ship measures 948 feet (289 m) - as long as three football fields. It was stacked high with containers but capable of carrying twice as much cargo. Safety investigators recovered the ship's black box, which can give them the vessel's position, speed, heading, radar, bridge audio, and radio communications as well as alarms. The same ship was involved in an incident in the port of Antwerp, Belgium, in 2016, when it hit a quay as it tried to exit the North Sea container terminal.

A later inspection in June 2023 carried out in San Antonio, Chile, found the vessel had "propulsion and auxiliary machinery" deficiencies, according to data on the public Equasis website, which provides information on ships. The registered owner of the Singapore-flagged ship is Grace Ocean Pte Ltd, LSEG data show. Synergy Marine Group managed the ship, and Maersk chartered the vessel.

WHAT DO WE KNOW ABOUT THE BRIDGE THAT COLLAPSED? The Francis Scott Key Bridge was one of three ways to cross the Baltimore Harbor and handled 31,000 cars per day or 11.3 million vehicles a year.

The steel structure was four lanes wide and rose 185 feet (56 m) above the river. It opened in 1977 and crosses the Patapsco River, where U.S. national anthem author Francis Scott Key wrote the "Star Spangled Banner" in 1814 after witnessing the British defeat at the Battle of Baltimore and the British bombing of Fort McHenry.

HOW WILL THE BRIDGE COLLAPSE IMPACT THE BALTIMORE PORT? Traffic was suspended at the port, the 17th largest in the country, and the jobs of 15,000 people are on hold. The flow of containers to Baltimore can likely be redistributed to bigger ports. However, there could be major disruptions in shipping cars, coal and sugar. It is the busiest U.S. port for car shipments, handling at least 750,000 vehicles in 2023, according to data from the Maryland Port Administration.

In 2023, the port was the second busiest for coal exports. It is also the largest U.S. port by volume for handling farm and construction machinery, as well as agricultural products such as sugar and salt.

(Writing by Lisa Shumaker; Editing by Daniel Wallis and Bill Berkrot)

(This story has not been edited by Devdiscourse staff and is auto-generated from a syndicated feed.)