UMCES scientists on the ecological impact of the Key Bridge collapse and recovery

April 2, 2024

On March 27, the Francis Scott Key Bridge collapsed after being struck by a tanker. The 1.6-mile structure lies in the Patapsco River, closing the Port of Baltimore, one of the nation’s largest ports. What is the environmental impact of this disaster? How will cleanup and rebuilding impact the Patapsco River and Chesapeake Bay? Faculty at the University of Maryland Center for Environmental Science (UMCES) work every day to help state and federal lawmakers and agencies understand questions like these.

“Our scientists are united in our desire to aid the massive effort underway to restore the Port of Baltimore,” said UMCES Interim President Bill Dennison. “We have reached out to our various partners to offer our assistance and advice and we are poised to offer our expertise to support efforts throughout the entire process of reconstruction.” 

UMCES scientists are experts on what happens to heavy metals when polluted mud is disturbed, how water quality is impacted by dredging the channel to deepen it for large ships, how that material can be used to rebuild marsh and habitat, and how fish and crab breeding grounds may be impacted. An initial assessment of the ecological impact of the bridge collapse on the Patapsco River is below.

Francis Scott Key Bridge in 2005 (Courtesy Michael Fincham/Maryland Sea Grant)

OVERVIEW: The immediate ecological impacts of the collapse of the Francis Scott Key bridge will likely be minimal. The ecological effects of the salvage operation and subsequent reconstruction may be more substantial and will require the same environmental safeguards that currently guide harbor activities.

Impacts of the collapse of the bridge itself can be separated into two areas: direct impacts on Bay life, and disturbance of sediment-bound chemicals. The bridge’s steel structure and road bed do not represent an immediate ecological threat beyond the damage to the habitat they have caused. The timing with seasonal cool water temperatures means that there is little migratory fish activity, fish and shellfish spawning is low and aquatic vegetation (marshes and submerged grasses) are not growing quickly. Moreover, the limited extent of the area impacted compared to the entire harbor complex and the upper Bay suggest that localized impacts will not affect the health of their populations.

CONTAMINANTS: The Bay’s sediment exists in a state of chemical balance with the overlying water. Since Baltimore is a port with a long industrial and commercial history, potentially toxic chemicals that are a legacy of that history occur in the sediments. These chemicals include metals (such lead, copper, zinc and mercury) and organic chemicals such as PAHs (polycyclic aromatic hydrocarbons) and PCBs (polychlorinated biphenyls). The impact of the bridge collapse will have affected that chemical balance, and some legacy contaminants bound to particles disturbed by the collapse are likely more exposed and available to interact chemically than they were before.  

FISHERIES: As the salvage operation continues into the spring/summer, more migratory fishes, such as shads and river herrings, will be moving through the area. White perch and striped bass are beginning to prepare for spawning. These and other species use the shallow waters that border the shipping channel extensively. Crabs are emerging from the winter dormancy and will be active in the vicinity of the collapse. Although not a prominent oyster ground currently, other shellfish, such as clams and mussels, will be more active and potentially filtering contaminated particles from the water.  The presence of dolphins in Baltimore Harbor in recent years. Dolphins may be affected by the restoration. These animals are very sensitive to sound, and if pile driving occurs, we can expect these animals to avoid this area as a result.

AIR QUALITY: There are interim impacts of the closure of the port related to increased emissions of carbon dioxide related to unexpected and additional shipping and movement of goods. Ships that would have come to Baltimore will now be diverted to different ports. Their longer journeys will result in greater emissions of carbon dioxide and other greenhouse gasses. Similarly, the additional distance transported goods will have to move on the nation’s road and rail network will also lead to increased emissions.

DREDGING: Navigational dredging will likely be required to maintain the shipping channel essential to port operations. The approach channel and the harbor are already dredged routinely to maintain required depths. There are well established protocols for monitoring and placement of dredged material in the containment facilities within the harbor. However, the salvage and reconstruction may involve dredging of shallow areas not routinely dredged to support port activities. Impacts in these shallow areas may be greater, and careful monitoring of the composition of the dredged material is warranted. Note, there are beneficial uses of dredged materials which represent opportunities for restoration and habitat improvement.

UMCES has been working directly to provide the Maryland Port Administration (MPA) with advice on environmental and economic issues for almost 40 years and has an important role in the Dredged Material Management Program.

The University of Maryland Center for Environmental Science (UMCES) has long-standing working relationships with state and federal agencies who are involved in Baltimore Harbor and will continue to provide scientific expertise on topics including water quality, water circulation, ecosystem dynamics, dredging, invasive species, sediments, contaminants, fisheries, wetlands, climate adaptation and mitigation, green shipping and economic analyses of revitalization of properties in the vicinity of the Port of Baltimore.

Prepared by Drs. William Dennison (Interim President), Jeff Cornwell, Lora Harris, Andrew Heyes, Russell Hill, Thomas Miller, Cindy Palinkas, Larry Sanford, Eric Schott, David Secor, Lorie Staver, Mario Tamburri, Lisa Wainger, and Ryan Woodland.

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