A barge carrying 700 tons of steel parts for the new Niantic River Bridge is expected to arrive at the project site this weekend.

The barge is delivering the major steel components for the structure that opens the bridge, known as the lift span. Amtrak is building a two-track, electrified, railroad bascule bridge across the Niantic River between East Lyme and Waterford, 58 feet south of its current location.

The barge left the steel fabricator, G&G Steel Inc. in Alabama, in mid-January - a tricky time for shipping since a nor'easter or any other severe weather could cause delays.

Its arrival has to be timed with high tide since it's easier to maneuver and tie up the barge when the water is at its highest.

"Any time you're moving a barge and steel, it all has to be carefully planned," said Peter Finch, the project manager for Amtrak.

The barge is traveling south of Long Island, through The Race and past New London. Local residents will be able to see it only from afar since the project site is fenced off and the nearby beach is closed while it is being filled with sand as part of the project.

The crews have three days to unload the steel parts using large cranes. Many of the parts will be transferred to another barge in the water where they will be bolted together over the next two months.

The lift span and its towers will weigh 1.6 million pounds even before the lead balance blocks and plates are added to act as a counterweight when the bridge opens.

Some of the parts were so large that they were laid on their sides for the trip to Niantic.

The $125 million bridge, funded with federal stimulus money from the American Recovery and Reinvestment Act and Amtrak's capital budget, is expected to be complete in May 2013. This month, the Amtrak crews also will weld 80-foot sections of rail into quarter-mile sections of track.

j.mcdermott@theday.com