Even though the economy is sputtering, some big transit projects in the city are moving forward, including the extension of the Number 7 line to Manhattan's far west side. NY1's Bobby Cuza filed the following report.

It's called a cutter head -- 22 feet wide, weighing 100 tons, with 44 rotating steel discs that will slice through Manhattan bedrock, creating a new tunnel beneath 11th Avenue for the extension of the Number 7 subway line.

"Some may question, with our economy stalling, the wisdom of proceeding with such an ambitious project now. My answer is, it's precisely now when we should be building this project and other projects like it," said Mayor Michael Bloomberg.

Thursday, at the mayor's signal, workers began the process of moving the enormous cutting head into place. Crews maneuvered it off the ground, then lowered it into a giant shaft at the corner of 25th Street and 11th Avenue. There, 125 feet below ground it will be assembled with other components into what's known as a tunnel boring machine, one of two that will begin drilling in the spring.

Once they begin drilling, the two tunnel boring machines will head north from here beneath 11th Avenue until they hit 41st Street, when they'll make a right turn before eventually connecting with the existing 7 line tunnel at Times Square.

The 7 extension will have just one new station at 34th Street and 11th Avenue, in a cavern that's already been excavated. There was not enough funding for a second station at 10th Avenue and 41st Street, and federal stimulus money will be used elsewhere.

Unlike other MTA projects, the entire cost of the 7 extension, at $2.1 billion, is being financed by the city. The mayor is betting on the 7 line to spur new development in the area.

"If you take a look at a map, the far west side of Manhattan is the gold coast for the future of this city, and this is going to allow people to build here, to live here, to shop here, to work here," said Bloomberg.

So far, officials say the project is on schedule, with the 7 extension set to open in December 2013.