Groton — Dozens of line handlers used to stand on top of the walls of the drydock at the Naval Submarine Base, shouting as they maneuvered the lines to keep a submarine centered in the basin.

Only a few voices could be heard over handheld radios on Tuesday as the USS Pittsburgh glided out of the dock and into the Thames River — even during the critical part of the maneuver when the stern cleared the back of the drydock and the submarine was subject to the winds and currents.

Instead of 75 people working on the dock, there were about 40.

The drydock, or Shippingport (ARDM 4), was upgraded with automated systems to flood the dock when a sub is entering or leaving and to keep the submarine centered so it doesn’t hit the walls. The Pittsburgh (SSN 720) was the first submarine to use the improved dock.

Kevin Crisman, the assistant regional maintenance officer, said the old way was “very, very manpower intensive,” but now a system of pulleys and capstans and the computers controlling the pumps do a large share of the work. It also costs far less to put a submarine in the dock instead of sending it to a shipyard, he added.

After the drydock was upgraded and returned to the base, it still had to be certified. The Groton waterfront did not have an operational dock for nearly four years.

The maintenance and system upgrades on the Pittsburgh began in September. Two tugs pulled the submarine to a pier on Tuesday, where the last of the maintenance and testing will be performed so it can rejoin the fleet in July. The Los Angeles-class submarine is scheduled to be inactivated in 2017.

While workers from Portsmouth Naval Shipyard were in charge of the maintenance, Electric Boat employees worked on the drydock.

“Having the Shippingport back is very important to us,” said EB spokesman Robert Hamilton. “That kind of work has been critical to maintaining the skilled work force that builds new construction submarines.”

Another submarine is not scheduled to go into the drydock, Crisman said. Crisman served in the Navy for 30 years and participated in more than 12 submarine maintenance availabilities in drydocks. The new technology, he said, is “just awesome.”