On 27 May 2004 Montpelier went through an 18-month Depot Modernization Period (DMP) at Portsmouth Naval Shipyard in Kittery, Maine. The ship and crew completed this period three months ahead of schedule and, after successfully completing sea trials returned to their home port in Virginia.[3] The boat entered Norfolk Naval Shipyard on 5 February 2010 for modernization, maintenance, and upgrades, expected to cost around $35 million for 640,000-man hours, and included changing the submarine's buoyancy characteristics and upgrading its sonar capabilities. The work was completed and the sub returned to the fleet on 26 July 2010, eight days earlier than scheduled.[4]
Accident
On 13 October 2012, USS Montpelier collided with the cruiser USS San Jacinto off the east coast of the United States near Florida. Both ships were conducting a training exercise at the time of the incident. No one on board either ship was injured.[5] The sub's captain, Commander Thomas Winter, was relieved and the sub has since undergone $70 million in repairs.[6]