The Delaware Memorial Bridge, a crucial transportation artery, is being protected from potential accidents by constructing dolphins filled with sand and concrete. This $100 million project is crucial in safeguarding the 2,000-ft span from potential collisions, ensuring safety for the Northeast corridor.
Photo courtesy of R.E. Pierson
The project will cost approximately $100 million and is two-thirds complete.
Some people might find insurance boring. Others would find the lack of insurance protection negligent, especially when it comes to protecting an important transportation resource like the Delaware Memorial Bridge. The insurance for this transportation artery is not only in a written policy but also in concrete, steel and sand.
The Delaware Memorial Bridge soars 188 ft. above the Delaware River and carries I-295 and Route 40 traffic from Delaware to New Jersey. The two suspension bridges are four lanes each and on a busy day transport 80,000 vehicles in each direction along the Northeast corridor. The Delaware River Bridge Authority (DRBA) collects tolls and manages the bridge.
Photo courtesy of R.E. Pierson
The DRBA is currently working to protect this valuable resource. The destruction of Baltimore's Key Bridge in March by a runaway container ship weighing approximately 100,000 tons is fresh in the minds of many.
Gregory Pawlowski, senior engineer of the DRBA, is working with R.E. Pierson Construction and Hudson Engineers to create eight cells or "dolphins" filled with sand, stone and concrete to protect the bridge towers that support the 2,000-ft. span across the water.
The timeliness of the effort is more circumstantial than good planning.
"The discussions about enhanced bridge protection go back to at least 1999," said Pawlowski. "At that time, there was not a desire to invest the dollars needed to protect the bridge. Planners felt it would detract from other infrastructure needs like caring for the bridge deck, upgrading overpasses and taking care of our ferries."
As the DRBA assembled the funds for adequate protection of the bridge, it also put together a team to work together on the project. The team included Ralph Farabaugh, construction supervisor, R.E. Pierson of Pilesboro, N.J.; and Tony DePasquale, director of marine engineering of S.T. Hudson Engineers of Cherry Hill, N.J.
"When we did our research, we discovered that we first applied for a grant for bridge protection back in 2002," said Pawlowski. "So the money took a while to arrive, but we are glad it is here now."
History of Serving Travelers
The second suspension bridge was completed in 1968 for $77 million. The first major bridge strike was just a year later when it was hit by a tanker that plowed through the "fender," the original protection system.
Today's protections are more robust than the earlier efforts. But today's ships are much more massive than the vessels of 50 years ago. The concept is surprisingly simple, although the execution is not.
"When a truck loses its brakes, the driver can plow into drums filled with sand on the side of the road," said Pawlowski. "These structures can save lives."
Photo courtesy of R.E. Pierson
The bridge protection follows a similar pattern. Workers have been building immense "dolphins," 80 ft. in diameter filled with sand and rock that can take the hit from runaway ships. The dolphins would be destroyed but would absorb the impact from the hit and leave the bridge towers unscathed.
The project will cost approximately $100 million and is two-thirds complete.
Of course, building protective structures in water is more complex than building them on land. The construction team began by sinking test piles to see the depth required. The piles were constructed in 40 ft. of water with the piles on the west side at 110 ft. and the east side piles at 135 ft.
The plan requires the workers to use a temporary platform to steady the straight wall sheet piling as it is lowered into the water. Pawlowski described the process as working off the temporary platform to lower the sheet piles slowly in the water, 5 ft. at a time, making sure the river mud did not cause the piles to toe in or toe out and overstress the piling interlocks. The eight dolphins required 150 sheet piles with each about 16 in. wide.
Precast concrete panels were attached to the inside and outside of the piles causing them to stiffen and be able to withstand the water pressure from the outside. The panels also should keep the steel from corroding in the water. Workers also installed a walkway and railing on the top of each dolphin.
The temporary platforms used 653 tons of steel. Once the construction is complete the platforms will be dismantled. The dolphins required a total of 3,700 tons of steel.
Construction Teamwork
Tony DePasquale brought some ideas for the dolphins over from his time with the Army Corps of Engineers. His team at Hudson put together the plan for the current construction in 2010. The team then put the plan forward for permitting and reviews by regulators.
When the plan for the protection system was approximately 30 percent complete, both R.E. Pierson and the DRBA began serious collaboration on how to best build the system. The working entity is called a Construction Manager General Contractor (CMGC).
Still, the team did not get adequate funding to begin the protections. Finally, the funding package arrived around 2018 and, after more reviews, work on the project began.
Photo courtesy of R.E. Pierson
"One of the key elements on this design is the inclusion of wick drains in the dolphins," said DePasquale. "This system allowed us to consolidate the soil without having to dredge the river. I believe this approach will work and save the cost of dredging."
Equipment for the project has included four 300-ton capacity cranes, several barges and an excavator for work in a marine environment.
Consultants with specialized water skills also have contributed to the work. One consultant monitored the vibration caused by driving the sheet piles. Another consultant did inspection dives while the cells were being filled. Their job was to ensure the integrity of the sheet piling interlocks during the filling.
As workers push toward the finish line for the project, S.T. Hudson, R.E. Pierson and the DRBA feel they have a solution that will be beneficial to entities in other states as they seek to protect their bridges.
"We don't want it to happen to our bridge what happened to the Key Bridge," said Pawlowski. "Our team has designed and built the protection to work against the biggest vessels that come through the Panama Canal. Our vision is to protect this bridge for future generations." CEG
Chuck MacDonald
Chuck MacDonald is an editor, blogger and freelance feature writer whose writing adventures have taken him to 48 states and 10 countries. He has been the editor for magazines on pavement construction, chemicals, insurance and missions. Chuck enjoys bicycling, kayaking and reading. He graduated from the University of Missouri with a degree in journalism. Chuck lives in Annapolis, Md. with his wife Kristen. They have seven grandchildren.
Read more from Chuck MacDonald here.
Today's top stories
