The Second Avenue subway is on track as it reached a new construction milestone Thursday.
The 485-ton tunnel boring machine completed its second pass from 92nd Street and Second Avenue, breaking through into an existing tunnel at the Lexington Avenue/63rd Street station.
It completes more than two miles of tunnels that will provide Q train service from 96th to 63rd Streets.
The long delayed project will alleviate overcrowding and delays on the 4, 5 and 6 lines, and eventually go from 125th Street down to Hanover Square, just south of Wall Street.
Some East Side residents and business owners are worried about the effects the construction could have on air quality in the area.
Area entrepreneurs also say construction has forced more than than 30 businesses to close, and the ones that remain battle disruption and debris.
"We are hurting, apartments are not renting like they used to, business is down," said a local business owner.
"I can feel it. It's difficult to breath and I see the dust and the dirt," said a local resident.
The Metropolitan Transportation Authority says it is doing what it can to curb those concerns and will shortly announce details on an air quality monitoring program.
"We've taken great steps in terms of building enclosures to try to be able to deal with noise and air quality, we'll continue to work with residents in any way we can," said MTA Chairman & CEO Jay Walder.
The next step in the $4.5 billion project will include installing the tracks, signals and communication systems.
MTA officials say the first phase of the subway line is scheduled to begin service in December 2016.
"I believe we'll deliver that. We're right now totally on schedule," said MTA Capital Construction President Michael Horodniceanu.
However, a federal study says the project will cost nearly $400 million more and take an extra two years.