Sometime in August, dump trucks delivered the final load of Patapsco River mud, dredged from the sea bed during the cleanup of the Key Bridge collapse, to the Kinsley landfill in Deptford Township, New Jersey, about 15 miles outside Philadelphia.

The mud, which contained random debris that came up with it and had to be picked clean, was the last of the materials contractors disposed of after the remnants of the bridge were dismantled and removed. Four months after the steel truss bridge collapsed, portions of its footings remain, as do the stubs of roadway to the southwest and northeast.

But all that fell is gone, as is the freighter Dali that struck the bridge and took it down.

By the rough estimate of Paul Hankins, the director of salvage operations for the U.S. Navy’s SupSalv, which coordinated the cleanup, about 50,000 tons of material was removed. Of that material, 16,000 tons was steel, a slightly larger amount was road material, and the remainder was the mud, which is officially referred to as “displaced materials.”

All of it was repurposed and put to good use. The steel was recycled, as was the concrete once the rebar was separated from it.

“We could be shaving with the Key Bridge remnants,” Hankins said. “No telling.”

The dredged-up mud was used to regrade and sculpt the decommissioned landfill, which hasn’t received any municipal waste since 1987. It was long ago capped and closed, but landfills settle over time and new material needs to be added to the top to encourage runoff of rainwater.

The grading material needs to be stable and consistent and relatively easy to work with. To be put in a New Jersey landfill, it also has to meet requirements for fill material set by the state’s Department of Environmental Protection. The Key Bridge dredge met all those standards.

After the main channel into Baltimore Harbor was cleared and opened in early June, the work of disposing the debris left by the collapse of the bridge continued at Sparrows Point and beyond.

One of the salvage contractors, Skanska, cut large pieces of the steel truss into fragments small enough to send to a recycler, roughly a cubic yard, with no piece having a dimension larger than four feet. Workers used hydraulic shears and torches to cut the steel, the same tools used to cut bridge sections on the Patapsco.

More than 100 workers cut down the steel, seven days a week, and 12 to 14 hours per day, said Stephen Skippen, a project manager for Skanska.

The small chunks of steel were then taken by truck to recyclers in the Baltimore area, chiefly Smith Industries, a large scrap processor with facilities in several Mid-Atlantic states. The fragments were weighed and sold to the highest bidder, some of them domestic, and some foreign. The global appetite for steel is ravenous, and it was consumed quickly. By June 17, Skanska had cleared Sparrows Point of steel scrap. And by July 10, the last piece of equipment left Sparrows Point.

“You wouldn’t know anyone had been there,” Hankins said.

The fate of the mud was more complicated and protracted. It could not be simply dredged and dumped elsewhere in the bay because it was contaminated with unknown amounts of bridge debris. For the same reason, pumping the mud was not an option – the usual method of removing mud from the bottom. Debris could cause pumps to clog or break.

Another contractor, Donjon Marine, carefully loaded the mud onto barges, preferably large ocean-going barges if they were available. If not, the mud was temporarily loaded onto smaller inland barges and transferred later. Large pieces of steel and concrete were immediately removed and taken to Sparrows Point.

Once ready for transport, the tainted cargo was taken up the Chesapeake Bay, through the Chesapeake and Delaware Canal, and into Delaware Bay. From there, the barges left the bay and entered the Atlantic Ocean for the offshore journey to Newark, New Jersey.

By then, the mud had stiffened as its water content evaporated. An excavator pulled any previously unnoticed pieces of debris out of the mud; a hardener, Portland cement, was added to transform the mud into something resembling clay before it was loaded onto trucks for the final leg to the landfill.

The journey was circuitous and long, but depositing the debris in New Jersey cost the state of Maryland considerably less than disposing of the material at an appropriate site in Maryland, Hankins said.

All told, Donjon transported more than 55,000 cubic yards of mud by barge, representing “many, many round trips,” said Tim Williamson, vice president of salvage operations for Donjon, who also oversaw the dredge operation for the Ever Forward, a container ship that ran aground near the Chesapeake Bay Bridge in March 2022.

(Dredging was the key to freeing the Ever Forward, but in that incident, the pristine mud was pumped and dumped on nearby Poplar Island, Williamson said.)

The vast majority of the Key Bridge mud was removed toward the end of the operation, because that work required the bridge remnants and the freighter Dali to be removed first. The Kurt Schulte was one of the barges used to transport the mud. The 10-year-old vessel is 256 feet long, 54 wide and draws only two feet when empty, and 23 feet when fully loaded. It could carry up to 5,000 tons of cargo at a time.

“The storage of the material was the choke point for how fast we could work,” Williamson said. The mud couldn’t be stored on land for regulatory reasons.

“We would pass the steel to Skanska,” Williamson said, “but the mud never went ashore.”

By the time the dredge material arrived at the landfill, it mostly resembled soil, said Daniel Edwards, the CEO and president of Transtech Industries, the parent company of the landfill. The process of adding more material and re-sculpting the hill will likely go on indefinitely as it settles, and dips and ponds form.

“Our employees, they’re like artists the way they do it,” Edwards said.

The Kinsley landfill has gone a step forward and become a solar farm, producing enough electricity to power 16,000 homes in New Jersey, Edwards said.

“We’re very proud of the fact, that we’ve taken a closed landfill and turned it into a renewable energy center,” he said. “The residents who live nearby don’t like living next to a landfill, but they don’t seem to mind living next to a renewable energy center.”