How a Delaware Memorial Bridge construction project will fortify against ship collision
What do you get when you combine 4,320 tons of steel, 15,000 cubic yards of sand, 4,320 cubic yards of large rocks and boulders, and over $92 million?
A protection system that could keep the Delaware Memorial Bridge from collapsing when hit by a ship — even one as large as the freighter that brought down Baltimore's Francis Scott Key bridge on March 26.
Construction of the new Ship Collision Protection System, part of the Capital Improvement Program, began last summer after nearly a decade of planning, DRBA Chief Operations Officer Vincent Meconi said. If construction stays on schedule, the system should be completely installed by September 2025.
Because construction of the Delaware Memorial Bridge dates back to 1945, it is not required to meet current safety standards—only those that were in place when it was first built.
Now, "it's past time to get it upgraded," Meconi said.
The work will cost nearly $93 million, according to DRBA. A $22.25 million grant from the U.S. Department of Transportation and bond issuances will fund most of the project. And although it may seem costly upfront, Meconi said it will allow the Delaware Memorial Bridge to remain safe and operational for many years to come.
"You have to think long term, especially when you've got an asset like ours," Meconi said.
Construction in progress
Over 100,000 vehicles cross the two spans of the Delaware Memorial Bridge each day, according to DRBA, with 2023 recording a near record-breaking 18.1 million vehicles crossing in one direction in the span of a year.
To protect those travelers from both accidental and intentional ship collisions, engineers have designed stone-filled cylinders called "dolphins" to reinforce the piers supporting the bridge. DRBA plans to build eight of these dolphins, each of which measure 80 feet in diameter and takes about three months to build.
The frames of the dolphins are made of steel piles driven into the riverbed. Then, in order to fill the cylinders, construction workers have installed long wick drains into the river bottom. As they pack in the sand and, later, stones, the drains act like straws and draw out the water to the surface. It's a laborious process, Meconi said, but an effective one.
Once the dolphins are completely filled, a cap will be placed over the top. The dolphin will then be ready to serve as a sort of airbag, Meconi said; it won't survive if it's hit by a ship, but it "would have done its job" to protect the bridge.
Other bridge safety investments
The installation of dolphins to prevent collapse in the case of a collision is not the only investment DRBA is making towards the safety of the Delaware Memorial Bridge.
The bridge is regularly inspected by engineers, according to DRBA, and millions are invested every year to maintain the bridge. This includes everything from painting the steel to protect it from corrosion to dehumidifying the bridge's main cables.
Meconi said that although it may seem scary in the wake of the collapse in Baltimore, it is safe to continue driving across the Delaware Memorial Bridge while the Ship Collision Protection System is installed.
"Obviously nothing in life is risk free," Meconi said "But we are trying to protect against something that is not going to be a common occurrence."
MORE: Port of Wilmington ship traffic 'close to double' after Baltimore bridge collapse
Send story tips or ideas to Hannah Edelman at hedelman@delawareonline.com. For more reporting, follow them on X at @h_edelman.
This article originally appeared on Delaware News Journal: Delaware Memorial Bridge adding ship collision protection system
