Early in the concept phase, engineers scrapped their preconceived notions of marine terminal design and dove deeper into the wind industry's needs.

When the New Bedford Marine Commerce Terminal, aka South Terminal, opens for business in 2015, the site will represent a lot of firsts.

It will be the first heavy load marine terminal in the U.S. capable of handling both uniform loads of up to 4,100 pounds per square foot and concentrated loads of about 20,000 pounds per square foot.

It will be the first offshore wind staging facility in the U.S. And it will be a first sign of a healthy offshore wind industry developing in the region.

But for builders and engineers working there now, equally exciting firsts are already happening at the site both through the design of the facility's structure and the integrated way it is being constructed.

Once complete, they say, that unique design is what will allow the terminal to function with more flexibility than even some European wind staging facilities do.

But by the time the first shipment of turbine components is offloaded, those features will be largely invisible.

"The bones are out there now, (but) it's going to get covered with skin," said Jay Borkman, principal designer, of Apex Engineering. "Right now you can see the steel cells poking out of the soil and it's those steels cells that give the front end of the facility, the bulkhead, its strength."

Stretching 1,000 feet along the front of the terminal, the bulkhead is made up of an interlocking series of 25 circular steel cells called coffer dams. In total, there will be 13 larger cells, 60-foot in diameter each, interspersed with 12 smaller ones.

Each cell is comprised of flat steel sheets, a little more than 1.5 feet wide, that are driven into rock in overlapping sequence to create the circular structure. The larger cells are made up of 116 sheets each and connect with the smaller cells to form a long chain along what will be the water's edge.

Piles placed inside the cells and around their exterior create additional support. The cells are then filled with earthen material taken from the harbor floor during harbor dredging.

The entire chain will eventually be covered with concrete to form the base of the platform, but as of mid-May, with construction a little more than halfway done, concrete had not yet been poured.

The design is a hybrid of styles that together give the terminal the strength to support the massive weights required and the flexibility to move them efficiently.

"There have been many other sites I think that have used the cellular coffer dams (design) and other sites that have used concrete relieving platforms pile support," said Susan Nilson, of CLE Engineering in Marion. "But to combine them and to be able to achieve the lift capacity that we have here — this is the first purpose built terminal to support offshore wind industry that achieves those loading requirements."

Early on in the concept phase, engineers scrapped their preconceived notions of terminal design and dove deeper into the wind industry's needs, taking into consideration lessons learned by European wind staging facilities.

"We originally expected to simply apply American marine design to this specific site and we kind of attacked it like, OK, we understand they want a big area to work, they need a bulkhead, they need some dredging," said Borkland. "Then we started to get input from Siemens, Cape Wind...all of these European offshore wind developers and they said to be efficient we need to have cranes, we need to have bigger ships...All of that information started to get put into our concepts and it caused us to modify the way we were doing some of the design process."

"We started to realize that even though Europe is 15 years ahead, that in some cases they didn't do things exactly the way they should have been done," he continued. "So we were able to learn from some of the mistakes that they made and they were more than happy to tell us (about those mistakes)."

For example, the team began with the idea that they needed an average load capacity of 4,000 pounds per square foot, but discovered that working from an average wasn't effective, because at specific times and locations, the required load capacity was much higher.

The European staging sites had stressed the need to achieve the right capacity, but the 4,000 pound average they offered up, didn't look right to the New Bedford team.

Concerned, engineers, including Nilson, traveled to U.S. crane manufacturers and investigated.

"We looked at specific cranes, the largest that are used, and designed (the terminal) for those cranes to be able to make the heavy picks right at the quayside," Nilson said.

Sensors placed under treads recorded loads of around 12,000 pounds. But that requirement rose even higher when the team looked at the trucks used to transport equipment. There they found loads that were closer to 20,000 pounds.

It was game-changing information.

"Everybody looks at what the average of the site is," said Borkland. "It turns out the numbers you have to build to are actually higher than the sort of average that the wind industry was telling us."

"We had to make sure we took that into consideration when we designed the (terminal) subsurface. So what we did was, rather than try to design this like they do in Europe to an average, we actually designed it for a specific crane, picking up a specific piece of equipment, at a specific distance," he said.

The result is a terminal that can handle concentrated loads of up to 20,000 pounds per square foot and that allows cranes to move freely, capturing whatever angle and position lets them better and more quickly offload heavy cargo.

"In a normal terminal, you cannot get a heavy duty crane right up to the quayside, here you will be able to," said Bill White, of the Massachusetts Clean Energy Center, which owns the facility. "And they'll be able to be mobile on the entire site right up to the quayside."

That mobility is crucial because industry cranes are huge, easily dwarfing the construction cranes there now. The cranes have six-feet-high and 20-feet-wide treads with counterweights that are almost as large as the cranes on site now.

"They are going to make these ones look like toys," Borkland said.