8. The Second Avenue Subway Renovation (New York City)
Estimated Cost: $6 billion
The long overdue repair and renovation of the Second Avenue Subway has finally been planned. It took a total of 50 long years before it happened as digging new Subway tunnels is no easy task in a populated mega city like NYC. The second phase is still said to be started by 2019. It might have taken a lot of time and money before construction began, but the end result is should be one for the books.
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