NEW YORK (CNNMoney) -- New York City is building a new subway line, one of the largest public works projects in American history.
The Second Avenue Subway -- a project more than 40 years in the making -- has a budget of $4.5 billion for the first mile-and-a-half segment. With three stops and a new entrance to an existing station, the cost of construction is more than a billion dollars a stop.
What contributes to the mammoth tab?
Big machinery, for starters. At $800,000 a piece, equipment such as hydraulic drill jumbos and load-haul-dump loaders can rack up a bill for the Metropolitan Transit Authority.
The single biggest piece of equipment -- the two-story, 22-foot in diameter tunnel boring machine -- takes 20 people to operate and costs approximately $12 million.
The tunnel boring machine makes the process much less disruptive to life above ground than the old-fashioned cut-and-cover method of building subways, digging underground from street level.
Now, highly specialized laborers do the work underground. Sandhogs, or urban miners, work alongside operating engineers who drive and maintain machinery. Between salary, benefits, FICA and other expenses, each worker costs about $1,000 per day, according to Tom Peyton, who's with construction manager Parsons Brinckerhoff.
Completing the entire proposed line -- running nearly the length of Manhattan Island -- would cost even more, between $22 billion to 24 billion, according to estimates from Dr. Michael Horodniceanu, president of MTA Capital Construction.
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