Construction crews are beginning to drive massive cylindrical piles into the Patapsco riverbed, part of the next stage of the expedited rebuilding of Baltimore’s fallen Francis Scott Key Bridge.

If everything goes right, some of these steel piles could later form part of the new Key Bridge, engineers said. But mainly, they are test subjects.

Once the piles are positioned deep within the river bottom, crews will top them with a large yellow cap that functions as a hammer, striking the pile repeatedly to test its strength. Eventually, the blows will reach a maximum force of about 10 million pounds, said Brian Wolfe, the director of project development at the Maryland Transportation Authority. ..

Each pile is more than 200 feet long and 8 feet in diameter, and weighs around 340,000 pounds, Wolfe said. So, maneuvering them requires some of the East Coast’s largest cranes, as have several other parts of the complex effort to demolish the old bridge and bring in the new.

Initial projections placed the cost for the bridge replacement around $1.8 billion, with a 2028 reopening date.