Infrastructure
How a $93M Project Will Protect the Delaware Memorial Bridge From Big Vessel Collisions
Delaware Memorial Bridge project will protect against potential ship collisions.
Photo courtesy DRBA
The twin spans of the Delaware Memorial Bridge will soon have an extra layer of protection from vessel collisions, such as the one that caused last year’s collapse of the Francis Scott Key Bridge in Baltimore.
Scheduled for completion in September, the two-year, $93-million project is adding a total of eight 80-ft-diameter stone-filled “dolphin” cylinders adjacent to the piers supporting the nearly 10,800-ft-long suspension bridge’s 440-ft-tall eastern and western towers. Constructed by R.E. Pierson Construction Co. of Pilesgrove Township, N.J., the cells are located a minimum of 443 ft from the edge of the 800-ft-wide, 50-ft-deep Delaware River navigation channel between Delaware and New Jersey.
For more than 50 years, the Delaware Memorial Bridge towers’ only protection from vessel strikes has been a channel-side fender system that successfully absorbed the impact of an oil tanker within a year after the second span to carry I-295 between the two states was added in 1968. Jim Salmon, a spokesperson for the Delaware River and Bay Authority says the agency has long recognized the need for a more robust collision protective system, particularly since more than 100,000 vehicles now cross the twin spans daily.
“Today’s cargo ships are bigger, faster, and carry more product than those plying the river in the 1960s,” Salmon says. “The old fendering system was antiquated and needed to be enhanced.”
Partially funded by a $22.25-million federal grant, construction of the dolphins began in July 2023. Each structure is formed by 150 interlocked 115-ft-long sheet piles driven 45 ft into the riverbed, extending through silty clay to an underlying layer of dense sand. The cells are filled with sand, stone and riprap. A ring of concrete is constructed around each cell’s outside face. An upgraded fender system is also part of the project, which has been closely coordinated with the U.S. Coast Guard, allowing the project to progress with minimal impact on shipping traffic
Salmon says the new system is designed to withstand the impact of a 120,000-deadweight-ton Neopanamax vessel traveling at approximately 7 knots.
By comparison, the Key Bridge was struck by the M/V Dali, also a Neopanamax container ship with an estimated deadweight tonnage of 116,000 at the time of the collision. In a March 18, 2025 report providing vulnerability assessment guidance for bridge owners, the National Transportation Safety Board (NTSB) noted that that the four 28-ft-diameter, rubber-fendered dolphins constructed along the Key Bridge’s navigation channel were insufficient in both size and location to protect the structure’s piers from a collision from an off-course vessel. The agency’s investigation into the incident is ongoing.
Although construction of the Delaware Memorial Bridge collision system was well underway when the Key Bridge was struck, Salmon says the incident has heightened attention in the project.
“A number of fellow bridge owners have requested information or plans, and visited the construction site to gain further insight into what we’ve done,” he says.
