Construction began this spring on a platform that will provide the foundation for the eastern half of Hudson Yards, a new, 28-acre neighborhood in midtown Manhattan that will be the largest private development in U.S. history, as well as the largest development in New York City since Rockefeller Center. The $20 billion project’s developers, Related Cos. and Oxford Property Group, faced a unique development challenge: how to construct almost 6 million square feet of new buildings above a working rail yard, where 30 railroad tracks converge into four near Penn Station, the nation’s busiest commuter rail hub?
The solution: a 37,000-ton, $700 million platform, a massive artificial foundation that will “float” above West Side Yard and be strong enough to hold up four skyscrapers (two office towers and two residential ones), as well as 1 million square feet of retail space and about five acres of public open space while also leaving room for trains to continue to operate beneath. The development team began drilling more than 250 caissons (each of which will be installed with 90-ton cores encased in concrete) deep into the bedrock below the tracks in March. Because of the location of the tracks, underground utilities and tunnels, only 38 percent of the site can be used to support the platform.
The 2.6 million-square-foot, 80-story 30 Hudson Yards, designed by Kohn Pederson Fox Associates, will be the fourth-tallest building in New York and home to the city’s highest outdoor observation deck. Set atop a platform being constructed over an operating rail yard, it will be the new home of Time Warner Inc. when it is completed in 2018.
Once the caissons are in place, work will begin on the platform itself, a foundation perched on those columns. But because there is no room for caissons at the narrow neck of the rail yard — and because the tallest of the site’s buildings, the 1,227-foot-high 30 Hudson Yards, is to be constructed directly over that neck — a system of 15 large-span trusses (reinforced horizontal beams) has been designed to transfer that structure’s weight to caissons on either side of the 150-foot-wide neck.
Throughout the platform’s two-year construction process, the rail yard will remain operational. Limited track outages will be permitted; the decking over the neck area will be put in place during 37 52-hour-long weekends, during which two of the four connecting tracks will be taken out of service at a time.
By the time the platform is finished in 2016, workers will have installed 25,000 tons of steel and 14,000 cubic yards of concrete. The completed platform will weigh more than 35,000 tons, more than twice as much as the Brooklyn Bridge. It is being financed with equity from Related, Oxford and Time Warner Inc. (lead tenant at 30 Hudson Yards) as well as a $250 million loan from Deutsche Bank AG, according to a March 19 Bloomberg News article.
While it is a challenging engineering project, this platform isn’t a first for New York City. In the early 20th century, the New York Central Railroad built a similar type of deck over tracks north of Grand Central Terminal, upon which much of the nearby Park Avenue neighborhood was built.