The port already gets long trains, of 110 cars or longer, project manager Kim Shaffer said. But it can't fit the entire train at once.
"They can come in, but they have to be broken in half and loaded on the existing internal storage tracks," Shaffer said.
Vancouver sits at an important rail junction. Small barges and oceangoing ships alike use the rails to move their cargo across the continent.
The port takes 45 minutes to an hour to break apart a train and bring it to port, and the same amount of time to reassemble the long trains, called unit trains, port spokeswoman Katie Odem said.
Both actions can cause delays in the entire system, BNSF spokesman Gus Melonas said. When the trains are split, half of the train goes to the BNSF yard, blocking the main line between Portland and Seattle.
"It can tie up, in some cases, for hours," Melonas said. The 10 Amtrak trains using BNSF track each day also can be delayed, he said.
When the port stops using that section of track, Amtrak can reconfigure it to provide more reliable service, said Larry Paulson, the port's executive director.
The Terminal 5 project is one piece of a $135-million project that will eventually create a rail loop through the port. Paulson said this first piece could cost up to $18 million, although he's hoping the bids, which are due Oct. 15, come in lower.
Intense coordination is required to load, unload and assemble trains, Paulson said. Adding track gives the port more flexibility.
"There's loading and unloading throughout the port," Paulson said. "We have a grain facility that will make use of the unit trains.
"But they might need to pull all the way back to the west end (and) then pull back," he said. "Mineral boats use it. And Subaru autos use unit trains right next to Terminal 5."
The rail loop will be built on the former Alcoa and Evergreen aluminum manufacturing sites the port bought earlier this year. Port officials needed to wait until those polluted sites were cleaned up, and the buildings were demolished, before it could close on the sale. The whole process took between 15 and 20 years, Paulson said.
When the entire project is finished, sometime around 2017, the port will be able to handle 160,000 to 180,000 railcars per year, Paulson said. It currently handles 45,000 to 55,000.
The first piece, expected to be completed next spring, will boost that number significantly, Odem said. "We'll add 25 percent more capacity than we have right now for railcars at the port," she said.