Firsthand look at MTA mega-digs

MTA staff photographer Patrick Cashin has been photographing the agency's Second Avenue Subway project on Manhattan's East Side since 2009.

This image of the tunnel construction was taken in December 2009.

Read on to see Cashin's spectacular photographs of the Second Avenue project as well as the East Side Access mega project, which will connect the Long Island Rail Road to a new passenger concourse underneath Grand Central Terminal.

Watch more: NYC's subway, still under construction
See more photos: Building NYC's Second Ave. Subway

A recently-released photo shows an update on the East Side Access mega project which will connect the Long Island Rail Road to a new passenger concourse underneath Grand Central Terminal, June 2013.

William Ury, East Side Access' Senior Quality Engineer, stands at the board where "sandhogs" and other workers sign in and out of the work site using brass plates, June 2013.

This recent photo shows an update on the status of construction on the Manhattan side of the project, June 2013.

A photo from September 2009 shows the Second Avenue Subway project in progress.

This recent photo shows an update on the status of construction on the Manhattan side of the project, June 2013.

Workers' boots are seen during the construction of the the Second Avenue Subway project, June 2013.

An October 2009 photo shows construction progressing in the Second Avenue Subway project.

This recent photo shows an update on the status of construction on the Manhattan side of the project, June 2013.

CBS News 24/7