KITTERY — Workers at the Portsmouth Naval Shipyard have witnessed a milestone with the arrival of the USS Virginia.

The Virginia represents the first in its class of submarines to undergo a major overhaul.

The shipyard in Kittery has been preparing to work on the new submarines since it was removed from the base closing list in 2005. By next year, one-third of the shipyard’s 4,400 workers will be assigned to Virginia-class submarines.

The nuclear-powered submarines are more technologically advanced than the Los Angeles class, which has been the yard’s bread and butter.

The Virginia arrived this afternoon.