The Long Island Rail Road now has an unobstructed path from Queens to Grand Central Terminal in Manhattan.

Crews working on the Metropolitan Transportation Authority's $8.24-billion East Side Access project Thursday broke through the final piece of concrete in Long Island City to connect newly bored tunnels in Manhattan to newly bored tunnels in Queens.

The result is a 3 1/2-mile-long subterranean passageway that will eventually bring 160,000 daily LIRR riders to Manhattan's East Side when the project is completed, scheduled for 2019.

"For the first time since the East Side Access project began, there is now a continuous path" through a newly built tunnel "from Queens to the East Side of Manhattan," MTA chairman Joseph Lhota said. "This is the path Long Island Rail Road trains will follow when this project is completed."

The MTA began digging new tunnels for East Side Access in September 2007.

In July, the MTA finished its major tunnel-excavating work, which required the use of 200-ton boring machines. But workers still had to punch through 120 feet of earth underneath Northern Boulevard. That meant propping up a busy six-lane road, a subway tunnel, and an elevated subway line -- and digging underneath.

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Workers Thursday punched through, creating a 5-foot square hole. It will eventually become a 60-foot-wide, 40-foot-high tunnel.

Michael Horodniceanu, president of MTA Capital Construction, called it "the most complicated and challenging 120 feet of tunnel" of any MTA project.

"That it is being completed as intended is a testament to human ingenuity and perseverance."