After 20 months of planning and construction, the McNally Construction Inc. semisubmersible caisson barge JG Burke got underway this week for its first job, building an $80 million wharf for the Canadian military at Halifax, Nova Scotia.
Originally built as an ABS oceangoing deck barge, the former Weeks 246 is now a 250’ x 75’ x 16’ work platform that can double as a transport and heavy lift ro/ro barge, with capacity up to 5,000 tons.
At the Weeks Marine Inc. Greenville yard at Jersey City, N.J., workers installed 1,600’ of internal piping running from each compartment to a 16” sea chest header pipe. Two 16” gate valves on the port and starboard sea chests supply water through the pipeline, varying from 6” to 12” in diameter.
The system, controlled from an operator’s station and valve manifold 20’ above deck, floods and de-ballasts compartments at the same rate, keeping the barge level all through roughly 90-minute cycles of submergence and surfacing. The barge can submerge to a depth of 18' over deck so the newly built caissons can be installed.
The JG Burke in a submersion test. Weeks Marine photo.
“There are a number of submersible barges in service but this barge is particularly unique,” said David Forrest, naval architect with JMS Naval Architects, Mystic, Conn., who developed the design. “I’m not aware of any that have removable wing walls like this barge. It provides increased lift capacity similar to a dry dock but also maintains the barge’s mobility for transporting it between job sites.
“Overall, it’s an extremely flexible design and perfect for marine construction or even salvage operations. It fits into a niche where a self-propelled, heavy lift ship would be overkill, and a floating dry dock too restrictive.”
The project started in July 2015 when McNally, a Weeks subsidiary based in Hamilton, Ontario, got together with Weeks, based in Cranford, N.J., and JMS. Construction started that fall, with a McNally team headed by Greg Burke, the company’s vice president of construction, working alongside Weeks personnel.
McNally “had a small barge they used to build caissons” and had been considering building a large barge, said Week’s John Devlin Sr., who headed up the project at Greenville. The idea was for a larger barge to fabricate caissons — bathtub shaped concrete structures used to build bulkheads — that could partially submerge and float off the caisson to be moved into position and set.
Considering factors of time and cost, McNally saw the opportunity to use Weeks’ resources and JMS to come up with a design using existing equipment. When Forrest proposed the concept of removable wing walls, Weeks president Richard Weeks had an idea: pontoons.
“Rich said, ‘We have those in our inventory.’ They were built for the FDR Drive,” a New York City highway project in the early 2000s, Devlin said.
Removable pontoons on the JG Burke. Kirk Moore photo.
Weighing 75 tons each, the steel tanks now rest in hinged mounts at each corner of the barge. That met “the principal challenge with this vessel…so that you have the ability to remove the wing walls [the pontoons, in this case] and place them onto the 75’ wide deck for transiting to a work site via the 78’ wide locks of the St. Lawrence Seaway,” Forrest said.
The work deck on the JG Burke. Kirk Moore photo.
At the work site, the buoyancy tanks are reattached, and the barge has a clear working deck of 150’x65’ with access from three sides.
Originally built in the late 1980s for Brown & Root as an oil platform launch barge, the Weeks 246 had a ballast system just to adjust draft and trim, with pumps below decks and valves accessible from the main deck only.
All had to be upgraded to handle increased flow rates, and new manifold and valve controls installed so tanks can be flooded and dewatered separately from a central control station. So the decision was made to replace all piping.
Up on the new control station, an array of valves on the operating manifold overlooks the work deck. Flooding to all 15 compartments is managed with remote controlled butterfly valves and dewatering driven by onboard compressors. In the control station house, a monitoring system designed and installed by Electronic Marine Systems Inc. (EMS Marcon) Rahway, N.J., monitors water depth in each compartment, overall internal compartment pressure, and differential pressure between compartments.
Harsh Shah of Weeks worked closely with EMS, and came up with innovative changes that allow the system to be remotely monitored from anywhere in the world to assist the crew with troubleshooting problems. A screen shows operators the water depth in every compartment at a glance. If there is a valve malfunction, a trunk from the control station down into the barge’s double hull allows access, even in the submerged mode.
Two self-elevating 36”x80’ spuds help keep the JG Burke in position while on site. The spuds are raised and lowered using air operated winches located on two of the forward pontoon. Air for these winches is provided by the same two 750 cfm compressors on the operations platform that supply air pressure for pumping out when de-ballasting the barge.
The finished barge is named for Greg Burke, the McNally vice president.
“The technical hurdles are often the easy part,” said architect Forrest. “It’s the creativity and experience that make projects like this a success. It’s rewarding at the end to see something completed that seemed almost unachievable in the beginning — at least from a cost-effective perspective.
“I’ll add too, that, the completed vessel obviously can’t convey the number of different design approaches and concept designs we explored to make a heavy-lift barge that can expand and retract its overall width at the job site,” he said.
Devlin obviously enjoyed the experience, capping his 32-year career with Weeks.
“I was supposed to retire in May of ’15,” Devlin said, looking over the JG Burke a few days before its departure. “But I took this on as one last project.”
