By all accounts, the destruction of Baltimore’s Francis Scott Key Bridge was first and foremost a human tragedy. Six men – all of them workers performing routine road maintenance – lost their lives in the early morning hours of March 26 after a cargo ship slammed into the span.

But was it an environmental tragedy as well? It doesn’t appear to have been, authorities tell the Bay Journal.

That’s not to say the environment is out of the woods. As the long, slow work of retrieving the fallen portion of the bridge from the mouth of the Patapsco River continues, environmental experts say, there are potential threats to water quality and aquatic life.

And in the years ahead, those experts point out, the situation will bear close monitoring as attention turns toward the planning and reconstruction of the lost Interstate 695 segment.

An Oily Sheen

The 1.6-mile Key Bridge had stood at the entrance to Baltimore Harbor since 1977. Its demise came suddenly when the container ship Dali apparently experienced power problems and rammed into one of the bridge supports.

In the weeks afterward, a picture of the bridge collapse’s environmental impacts was only beginning to come into focus.

Here is what is known so far:

An oily sheen appeared on the surface of nearby waters in the hours after the collapse, prompting worries that the stricken ship was leaking hazardous fluid. Authorities deployed thousands of feet of booms to contain any spills. The sheen has since dissipated.

The massive vessel was carrying more than 4,000 containers at the time of the incident, according to the salvage operation’s public affairs office.

Of those, 56 contained hazardous materials, including corrosive and flammable substances, lithium metal batteries and other chemicals. The hazardous chemicals onboard that spilled from 14 damaged or destroyed containers consisted of soap products, perfume products, or not otherwise specified resin.

Three rounds of water sampling conducted upriver and downstream of the site, however, showed no evidence of fuel spillage or release of lithium or sulfur, according to the Maryland Department of the Environment. Fish consumption advisories weren’t altered in the region.

“At this time, there is no immediate concern of risks to the environment or public health,” said Lt. Cmdr. Amanda Faulkner of the U.S. Army Corps of Engineers, the agency coordinating the recovery effort.

Crews have also worked to minimize the potential threat posed by a BGE natural gas pipeline that runs beneath the shipping channel in the vicinity of the crash site. The line has subsequently been shut off and the gas inside of it rendered inert to prevent any fire or explosions, authorities say.

Contaminated Sediments

“Our biggest concerns moving forward are really related to the impacts of disturbing the legacy sediments we know are present in the harbor,” said Allison Colden, the Maryland executive director for the Chesapeake Bay Foundation.

Much of Baltimore Harbor’s sediments contain a toxic cocktail of lead, copper, zinc and mercury as well as organic chemicals such as PAHs (polycyclic aromatic hydrocarbons) and PCBs (polychlorinated biphenyls). While contamination levels can be dangerously high, they vary from place to place, researchers say.

A toxic cocktail of lead, copper, zinc, mercury, PAHs (polycyclic aromatic hydrocarbons) and PCBs (polychlorinated biphenyls) are in the harbor’s sediments.

The material inside the regularly dredged shipping channel tends to consist of fresher deposits and is, therefore, relatively clean.

But the sediment in some locations outside those channels – especially to the southeast at the site of the former Sparrows Point steel mill – is so polluted that scientists have long admonished against disturbing it.

• Sparrows Point admits that toxic chemicals have been leaking into Baltimore Harbor for years (11/23/2009)

Under normal circumstances, that’s acceptable because the water on top of the contamination acts like a cap, keeping the pollution in a state of chemical equilibrium, experts say.

Efforts to unstick the ship from the mud and reopen the channel, though, could upend that balance, they worry.

“With the crashing down of the bridge and pulling the bridge out of the mud, those activities of recovery and rebuilding are going to cause a lot more disturbance than the natural processes that occur there,” said Larry Sanford, a University of Maryland Center for Environmental Science sediment expert who has studied the harbor for decades.

The good news, said Jeff Cornwell, another UMCES sediment expert, is that the sediment in the part of the river where the bridge collapsed is generally cleaner than it is farther upstream.

The MDE has been testing water for metals to assess whether any of the response activities might be causing contaminants in the riverbed to be resuspended. So far, no elevated levels have been detected, Faulkner said.

Risks to Aquatic Life

Fish, crabs and other living creatures – including a large oyster bed planted by the Chesapeake Bay Foundation near the collapsed bridge at Fort Carroll – will probably emerge from the ordeal relatively unscathed, said Bill Dennison, UMCES’ president.

The biggest concern is the timing of the emergency dredging, he added. The Port of Baltimore typically winds up its routine harbor dredging program by the start of April each year to prevent impacts to growing underwater plants and heightened fish activity in the warmer months.

Dennison said he is confident the port will accomplish the work “in the most environmentally sensitive way possible with the technology at hand.”

Another timing-related concern is the pressure officials are under to rebuild the bridge.

It will likely take several years and hundreds of millions of dollars to reconstruct the vital transportation link. Members of Congress from Maryland have unveiled a bill to have the federal government assume 100% of the cost of the building the replacement.

Environmentalists say they fully expect the environmental permitting for the project to be expedited to get the bridge reopened as quickly as possible.

If that’s the case, Colden said, “we don’t want that to result in skipping any of the steps that would happen under a traditional review process.”

• A version of this story was first published in the Bay Journal.