“Hole-through” milestone on NYC’s Second Avenue Subway project

“Hole through” at USA Civil’s 86th Street Station project, part of New York City’s Second Avenue Subway project.

With a loud boom, followed by cheering and clapping, the subterranean wall of rock separating the northern and southern halves of Skanska’s 86th Street Station project was breached earlier this year in what is called a “hole through.” This is part of USA Civil’s work in constructing its portion of New York City’s long-awaited Second Avenue Subway.

“Thanks to the skills and hard work performed by our dedicated craft workers, engineers and supervisors, we have safely holed through the first drift of this future rock cavern subway station,” said Gary Almeraris, USA Civil project executive. “This is just the beginning of a series of major work milestones necessary in completing this subway, which will change the landscape of the Upper East Side community for generations.”

The Skanska joint venture’s work at this station – which will be about 1,000 feet long, 70 feet wide and 50 feet high – began last year and will be completed in 2014. The subway is expected to open to the public in 2016.

The hole through involved drilling 125 holes in the rock wall; those holes were then loaded with explosives that were wired together and timed sequentially. As the blast was about to commence, our team stopped cars and pedestrians on the busy street above to ensure the public’s safety. They also carefully monitored the impacts of the blast using seismographs and building instrumentation.

Following the hole-through, crews have been excavating rock from this cavern and its multiple entrances. Then concreting operations will commence, with concrete being poured in two shifts daily well into 2014.

This hole through follows earlier work we did on a separate Skanska-led joint venture that bored 14,000 linear feet of 22-foot-diamater tunnels through the Manhattan schist. We used massive tunnel-boring machines to carve that network 80 feet below ground level.

Click here to view some great photos of the 86th Street Station excavation.

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