Using a 642-ton tunnel-boring machine, contractor Granite Traylor Frontier Joint Venture, of Long Island City, finished mining the third of four new tunnels underneath the busy Sunnyside Yard in Queens on Tuesday night.
On the western end, the tunnel connects to a separate tunnel that goes under the East River and into Grand Central Terminal. On its eastern end, the new tunnel connects to the LIRR's Main Line tracks that lead to Jamaica and Port Washington.
Metropolitan Transportation Authority officials said the new tunnel, which began being bored on March 26, was finished seven weeks ahead of schedule.
The fourth and final tunnel being built in Queens is expected to be finished by August. Workers also still have to excavate a 100-foot section of ground underneath Northern Boulevard.
"We are delighted to complete this important milestone," MTA Chairman Joseph Lhota said in a statement. "Each piece of the project that we bring in ahead of schedule means we can dedicate resources to those parts of the project that most need attention."
Lhota revealed earlier this month that, as a whole, East Side Access is running about a year behind and $1 billion more than the agency's 2009 projections. The MTA now says East Side Access -- the largest public works project going on in the United States -- will be completed by 2019 and cost as much as $8.24 billion.