The National Transportation Safety Board issued an urgent recommendation to the U.S. Army Corps of Engineers last month, calling on them to evaluate the Bourne and Sagamore Bridges for risk of collapse in the event of a vessel collision.

This recommendation came out of an investigation into last year’s collapse of the Francis Scott Key Bridge in Baltimore by the National Transportation Safety Board, which killed six people. The investigation yielded a report that included a list of 68 bridges that are overdue for risk assessments, including the Bourne and Sagamore Bridges.

CAI’s Gilda Geist spoke with John MacPherson, canal operations manager for the U.S. Army Corps of Engineers New England District to learn more about the status and safety of Cape Cod’s current and future bridges. What follows is a lightly edited transcript.

Gilda Geist: What is your current understanding of the risk of collapse due to vessel collision for the Cape Cod bridges?

John MacPherson: We’re fortunate at the Cape Cod Canal in that we limit vessels in the Cape Cod Canal that fit within the channel depth, the width, and underneath the air draft of the bridges. The size of ship that hit the bridge in Baltimore Harbor was much larger than we would permit to ever transit the Cape Cod Canal. The maximum length vessel that is permitted to transit our canal is 820 feet. The motor vessel Dali that brought the bridge down in Baltimore was 980 feet long, so it was a much longer, heavier vessel. We’re protected and safe in that that size ship wouldn’t be allowed to transit our canal. The other important point here with our channel is that we have marine traffic controllers that monitor and manage all large vessels transiting our canal. So our controllers confirm everything is working on a vessel prior to entering our project, and they ensure that vessel is aware of any other special circumstances that could impair safe navigation.

Geist: I was looking at the report that the National Transportation Safety Board put out, and there was that urgent recommendation that the owners of various bridges, including the Cape Cod bridges, use the American Association of State Highway and Transportation Officials’ method to assess the risk of collapse due to vessel strike. So I’m wondering, when is the last time the Army Corps of Engineers has used that method to assess that risk? And is there a plan to use that method to assess those bridges again soon?

MacPherson: The last time we had an evaluation was in 2006. We completed a vessel allision [nautical term for when a ship strikes a stationary object] analysis. That analysis showed the risk of allision is extremely low, and nothing’s changed in the channel configuration or the bridges since 2006. However, we are planning on performing another analysis to provide a more current assessment of the situation for our current bridges. We are partnering with the state and federal entities to have both highway bridges replaced. When they do get replaced, we’re changing the configuration quite a bit. That will help bridge and navigation safety. The new piers for the bridge will be out of the water completely. That’s a huge change that’ll help with safety of the bridges and navigation in general.

Geist: Is there a plan for how often the Army Corps of Engineers will be doing this type of risk assessment going forward with the new bridges?

MacPherson: It won’t be a reoccurring thing, unless something changes in the channel or the bridges. The additional assessment that’ll be done on the new bridges—that assessment will be performed and we believe those piers will be protected.

Geist: I was watching the press briefing for this report when it came out, and the chair of the National Transportation Safety Board was talking about how ships have changed. She talked about the difference in how big and how heavy ships were in the 1950s versus now. Would there be periodic assessments to keep up with any changes in the shipping industry as well?

MacPherson: I don’t know if we’ll need periodic. We would certainly perform updated analyses if anything changed—if the ships became larger that were transiting our canal here. In general, the size of the vessels stays pretty uniform year to year. We have some reoccurring, known vessels that deliver automobiles through the canal, and almost two billion gallons of petroleum flows on barges through the canal. The size of those generally stays the same for our canal. They are getting larger in some of the other harbors that are dredged deeper, but the Cape Cod Canal, at this time we have no plans to expand its depth or width. And because of that, I think the vessel size will stay pretty uniform.