An “unforeseen event” or an accident waiting to happen?
The recent collapse of Baltimore’s Francis Scott Key Bridge (Maryland State, USA) following the strike by the container ship Dali brings home the value of risk identification and mitigation, as well as the tragic consequences (six lives lost) and cost (est. up to US$3bn (Baltimore bridge collapse: Insurance loss could hit $3bn (bbc.com)) of not adequately addressing such.
As a Process Engineer, I have no technical knowledge of bridge design and/or construction; and up until the news of the Dali container ship striking the bridge, and it’s subsequent collapse made the news on the 26th March, I was unaware of its existence.
Reading subsequent reports of this event (Where Baltimore bridge investigation goes now (bbc.com)) raises some significant points:
- The 1970s constructed Francis Scott Key Bridge was designed at a time much smaller shipping was in use, and much less shipping trafficking the Port of Maryland. Since then, container ships have become ever more massive (the Dali being reported as being in excess of 85,000 gross-tonnes) and many more of these behemoths traverse the world’s shipping lanes and ports. Was the safety case updated adequately?
- The Continuous Through Truss design employed on this 1970s design does not have the redundant support structures employed within more modern designs. Partial failure often cascades to total failure. As such, the Francis Scott Key Bridge has/had known design vulnerabilities when compared to more modern designs.
- It is reported that almost minutes elapsed between the Dail container ship losing power (and it is believed, steering) and striking the bridge. Was the port traffic management appropriate given container ships losing steering isn’t unforeseen, and does happen – as per the recent (March 2021) Ever Given Container ship running aground in the Suez Canal (How One of the World’s Biggest Ships Jammed the Suez Canal – The New York Times (nytimes.com)).
Was this bridge strike an “unforeseen event” or an accident waiting to happen? In my career, I have never seen an “accident waiting to happen”; rather an opportunity missed to prevent one happening.
The paragraph that stands out for me in this BBC article is the quote from Ms Mattei:
Experts told The Conversation that it appears “dolphins” – protective barriers – were installed near the Francis Scott Key Bridge but did not prevent the vessel taking down the bridge.
Ms Mattei said that mitigating risk is about analysing probabilities in choosing where to spend money.
Ultimately, authorities may have judged that the likelihood of a massive ship hitting one of the bridge's supporting columns was too low to justify reinforcing them. “We have limited dollars to invest,” she said.
As with most engineering projects I have been involved with, I would expect that this bridge was engineered to a budget, and within a schedule. Quality may well have been a distant third concern when the project was awarded. Often such projects can and are awarded to the lowest bidder. I could not say if this was the case here. I am not, and do not suggest that safety was neglected on any of these projects.
Whether or not is was as comprehensive and robust as it needs or needed to be is the US$3 billion question (What is the economic cost of Baltimore’s bridge collapse? | Shipping News | Al Jazeera) for the insurers associated with the Francis Scott Key Bridge. And let us not forget that six people lost their lives. There is no price for the families of the bridge workers tragically killed. As Engineers, our first concern should be that the consumers of our engineering get to go home after such use.
It is a note to all of us that time changes many things; the design basis and safety case for this particular bridge from the 1970s seemingly being one such change. To reinforce that point is the chilling article from the Wall Street Journal that details eight (8) additional bridges in the USA that are vulnerable to a repeat of the Francis Scott Key Bridge collapse (These Eight U.S. Bridges Are Vulnerable to a Repeat of the Baltimore Crash – WSJ).
CNN goes further in claiming that one (1) in every thirteen (13) bridges in the USA are in “poor” (CNN’s words) condition (1 in every 13 bridges in America is in ‘poor’ condition. Thousands could collapse from a collision | CNN Business) and that “thousands” (CNN’s words) could collapse from a collision!
It is much easier to say with hindsight what could have been done; should have been done. Sadly, bridge collapses from shipping strikes in the USA are not a new thing and are not as uncommon as they should be.
The Washington Post (A list of major bridge collapses, ship crashes in U.S. history – The Washington Post ) makes reference to seven (7) other incidents over the last 52 years. As above, this is all the more sobering given container ships have greatly increased in tonnage and there is significantly more shipping than in past times.
The Maryland Port adjacent to the Francis Scott Key Bridge is reported to be the 9th busiest in the USA for international cargo and also ships transporting liquified natural gas. (Baltimore bridge collapse: Ships carrying cars and heavy equipment need to find a new harbor | AP News)
One would hate to think of the potential consequences had an LNG bulk carrier struck the Francis Scott Key Bridge in similar circumstances to the Dali.
