Since 2017, train cars from as far away as Alberta, Canada, have carried propane and butane to Underwood Energy’s rail yard in Sparrows Point. There, the company transfers the gas onto tractor trailers bound for customers throughout the region, who use it to cook, heat or resell.

Owner Sean Underwood told The Baltimore Sun that more than 70% of the trucks used to head south from his facility, a route that took them over the Francis Scott Key Bridge, until March 26, when the massive cargo ship Dali toppled the span.

“People just think, ‘Oh, you can take the tunnel.’ Well, we aren’t allowed to run our traffic through the tunnel,” Underwood said of restrictions on hazardous materials in the harbor tunnels. “So what are we supposed to do? Just be put out of business? It might take them five years to fix that bridge.”

On Tuesday, Underwood Energy sued the Singaporean companies that own and operate the Dali, arguing they should be held responsible for damages related to the collapse that also killed six construction workers.

Grace Ocean Private Ltd. and Synergy Marine Group have sought to limit their liability in the disaster, but the propane distributor contended in a legal filing that not only should their liability not be limited, but that “an example should be made” of the ship’s owner and operator.

“We’ve lost sizable clients because of the bridge collapse,” Underwood said in an interview, noting that tractor trailers now must make a 30-mile detour around Interstate 695. “It’s been beyond detrimental to the success of that facility. In our world, you’re successful based on margins of pennies. To essentially double your freight because the bridge is gone, it makes you non competitive.”

His company’s legal filing described the Dali as “unseaworthy” and its owners and operators as “negligent.”

The “allision with the Key Bridge,” Underwood’s lawyers wrote, “was foreseeable, avoidable, and a direct and proximate result of Petitioners’ carelessness, negligence, gross negligence, and recklessness, coupled with the unseaworthiness of the Dali.”

Darrell Wilson, a spokesperson for Grace Ocean and Synergy, declined to comment on Underwood’s legal filing.

“Unfortunately due to the ongoing investigations, in which we are fully participating and the legal proceedings, it would be inappropriate for us to comment at this time,” he said in a statement.

Bryan Short, an attorney for Underwood, called the gas industry a “cutthroat business” and said that his client is now at a marked disadvantage with competitors.

“My client believes that there’s been a great harm to the area surrounding Baltimore that needs to be addressed by the authorities and the parties responsible,” Short said.

Much of maritime law is rooted in decades- and centuries-old precedent. In this case, a 1927 U.S. Supreme Court decision, Robins Dry Dock v. Flint, could make it difficult for Underwood’s filing to succeed, Baltimore attorney Charles Simmons said Tuesday. Without direct, physical damage to a claimant’s property (such as the bridge itself or the people and vehicles on it), it is challenging to recover lost business.

“Under the current state of maritime law, it is hard to imagine that these types of claims — without a physical loss or personal injury — are going to result in recoveries involving economic losses,” said Simmons, who teaches maritime law at the University of Baltimore and University of Maryland law schools and practices at Whiteford, Taylor & Preston.

The Dali lost power twice in the shadow of the Key Bridge on March 26, rendering it mostly adrift as it smashed into one of the span’s critical support columns, but the legal claims filed to date against Synergy and Grace Ocean, including Underwood’s, focus on what happened before the massive cargo ship left the Port of Baltimore’s Seagirt Marine Terminal.

Federal investigators with the National Transportation Safety Board determined that the Dali lost power twice about 10 hours before it departed on a voyage for Sri Lanka.

The in-port blackouts, or total power losses, led crew members to switch breakers for the ship’s electrical power system, according to the NTSB’s preliminary investigative report. The replacement breakers tripped after the 984-foot Dali departed early the morning of March 26, causing the first of two complete power losses aboard within about half a mile of the bridge.

More recently, investigators have narrowed their probe on an electrical component about the diameter of a soda can. The NTSB brought in representatives from the ship’s Korean manufacturer, Hyundai, to analyze the device.

Less than a week after the bridge fell, the companies that own and manage the Dali filed under a 19th-century federal statute to clear themselves of liability and limit potential damages related to the collapse to the salvage value of the ship and the revenue it stood to make from its cargo, which they estimated at $43.7 million.

In the weeks and months after the collapse, crews searched for the bodies of six construction workers who plunged to their deaths in the Patapsco River and then removed the crumpled span and tons of highway debris from its murky waters. Those salvage efforts cost hundreds of millions of dollars, and authorities estimate it will take at least $1.7 billion to rebuild the bridge, which officials expect to be completed by fall of 2028..

While responding to the disaster, Maryland and federal officials pledged to hold the Dali’s owner and manager accountable.

Baltimore’s mayor and city council were quick to allege negligence on the parts of the companies behind the Dali, arguing in a court filing that they allowed a ship unfit to sail to leave the Port of Baltimore. Others, including a Baltimore publishing company, followed suit with similar legal arguments.

The law that Synergy and Grace Ocean filed under to protect their companies — the Limitation of Liability Act of 1851 — came under scrutiny in the aftermath of the Key Bridge collapse. Arguing the statute, designed to protect the maritime industry, was outdated, some federal lawmakers pledged an overhaul.

Democratic U.S. Reps. John Garamendi and Hank Johnson, of California and Georgia, introduced a bill in August that would retroactively increase the liability rate of foreign vessels beginning the day before the bridge collapse. Under their legislation, the companies behind the Dali could be on the hook for as much as $854 million.

Baltimore Sun reporter Madeleine O’Neill contributed to this article.