The Panama Canal's massive expansion project—started in 2007 to let bigger ships go through the Central American waterway—is scheduled to be completed sometime in 2015.
That has spurred cities along the U.S. East Coast, like Baltimore, Miami, Jacksonville, Fla., and Charleston, S.C., to undertake multimillion-dollar efforts to increase their harbor capacity and local infrastructure.
They want to be able to handle the larger ships and their cargo in order to gain from an anticipated economic boost, to everything from manufacturing to rail lines to real estate.
But some analysts warn the expectations of a boom surrounding the port projects may not happen.
"It's not going to be there from the canal," said Ed Sands, global practice leader at the transportation procurement firm Procurian.
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"Places like Florida don't have the distribution activity that the big cargo ships need so I don't really see them going there even if the harbors are deeper," he said.
"And when global trade went negative during the Great Recession, shipbuilders re-examined their capacity and made ships 25 percent bigger than even the new Panama Canal expansion will handle," he said.
"The cities have unrealistic expectations when it comes to the canal expansion," said Jean-Paul Rodrigue, professor of global studies and geography at Hofstra University.
"They believe their own expansion will bring in business and new trade," he said. "But It won't create trade and if you look at U.S. port traffic over the last few years, it's been leveling off."
"There may be some shift in cargo going to the eastern U.S. ports because of the canal expansion and their improvements but It's just not guaranteed," Rodrigue added.
The canal's expansion will cost at least an estimated $5.25 billion. Funding comes from canal traffic taxes and tolls (the current average toll cost per ship is $32,000 but is expected to rise after the expansion) and from international loans to the Panama Canal Authority, or ACP, which runs the canal.
The expansion was supposed to be completed in 2014—the 100th anniversary of the canal. But a reported problem with concrete for the new locks pushed it back to 2015.
When done, the canal will be able to handle ships with a capacity of 12,000 to 13,000 twenty-foot equivalent units, or TEUs, as used in shipbuilding measurement terms. That's up from the current 4,800 to 5,000 TEUs for ships. A TEU is essentially the volume of one intermodal container or those big metal boxes used to transport goods.
The ACP predicts that cargo volume transiting the canal will grow an average of 3 percent per year, doubling the 2005 tonnage by 2025.
Nearly 14,000 vessels of all kinds use the canal each year and some 70 percent of all shipping cargo going through the canal comes to the U.S. coasts.
But China's imports to the U.S. East Coast go mainly to the West Coast—only 20 percent go through the Panama Canal—as it's still cheaper to unload at Los Angeles and then transport goods by train and truck to cities like New York.
Canal expansion could take some 35 percent of current West Coast freight, according to one estimate, because the bigger ships, called Post-Panamax, will have more cargo, making it, theoretically, more cost effective.
"It can cost a lot to unload in Los Angeles and put goods on a truck and ship East," said Bob McMillian, chairman of the Panama Canal Commission in 1993.
(The commission functioned as an independent agency maintaining the Panama Canal until 1999, when the ACP took over.)
"There's no doubt in my mind that it will be cheaper to transport goods through the canal to the East Coast," he said.
The only port on the East Coast able to handle the Post-Panamax ships is The Port of Virginia at Norfolk. West Coast ports are naturally deeper and can handle the bigger ships.
So, East Coast cities, along with the budget-conscious federal government, are prying open the checkbook to attract the Post-Panamax ships. (U.S. ports are under federal control, including providing funding for maintenance and improvements).
South Carolina is currently investing some $700 million in port-related infrastructure projects in Charleston, said Jim Newsome, CEO of the South Carolina Ports Authority, and an expected $1.3 billion—mostly federal aid—over the next 10 years.
"American exports are growing again and while it may not be a boom, more ships from Asia will come through the canal and to East Coast cities," said Newsome.
"We'll have more jobs and more opportunity for manufacturing as a result of the capacity to handle the bigger ships," he said.
"The Port of Miami paid $43 million for four super-sized cranes that can handle cargo from the larger ships," said Edward Easton, chair of industrial development firm The Easton Group, based in Miami.
"Local government is spending $550 million on a tunnel that will enable tractor-trailers to go from the port directly to I-95," he said. "We should see at least a 3 percent improvement in the local industrial economy from the expansion and what the city is doing."
As much as the money has been flowing, it's been difficult to come by. States and cities are having to put their own funds in, as the money from Washington for port improvement is dependent on reviews and approvals that take time.
New York and New Jersey officials announced a plan in 2010 to raise the Bayonne Bridge from 151 feet above the water to 215 above the water to allow the bigger ships to pass through to New Jersey's Port Newark and other local ports. The review process is still in effect.
And Congress has to agree on a renewal (currently done every two years) of the Water Resources Development Act, which collects fees for harbor improvements and dredging, which reportedly has some $8.1 billion on hand.
"We need the support of federal dollars to keep this process going," said former U.S. Sen. George Lemieux, R-Fla., who served on the Senate Commerce, Science and Transportation Committee.
"Florida is a donor state, meaning we send more money to Washington than we get back, so getting the funds to help the port projects will be consistent to help create jobs," he said. "People in Miami and Florida are optimistic about the canal expansion and the benefits to us."
What lies head for the U.S. ports is a guessing game, analysts say.
"There's no question it's a gamble to do all these port improvements," said Chris Davis, a maritime lawyer who has lived in Panama and whose first job was to work on the Panama Canal, measuring water levels.
"But the bottom line is there is a need to expand the canal to handle the bigger ships," he said.
"My advice is don't expect a miracle from the expansion," said Hofstra's Rodrigue. "The health of the economy is more important than the size of the ports when it comes to benefits from shipping trade."
One analyst said it's the long-term picture that's important.
"This is not a five-year strategy for the ports we're talking about," said Lemieux. "It's a 50-year strategy to see the overall results."
—By CNBC's Mark Koba. Follow him on Twitter@MarkKobaCNBC