Groton - The four submarines that were in port at the Naval Submarine Base left Friday to get out to sea ahead of Hurricane Irene.

The USS Pittsburgh was the first out at 10 a.m., followed two hours later by the USS Providence, then the USS Hartford and USS Toledo. The USS Missouri, which is at the Electric Boat shipyard, will be sheltered in a dry dock, said Capt. Marc W. Denno, commanding officer of the base.

It marked the first time since the hurricanes in the 1980s that the Navy has ordered a sortie of its in-port submarines from Groton.

Denno said he wasn't necessarily worried about the subs hitting the pier during the storm but feared that anything that broke free on the lower base could hit the subs and damage the hulls. Sending the submarines to sea, he said, "significantly changes the risk equation."

"The number of unknowns goes down to zero," he said while watching the Providence (SSN 719) leave shortly before noon.

The submarines, which left with full crews of about 130 submariners on each, had to travel 10 hours from Groton and submerge to about 400 feet, he said. Denno could not say when the submarines would return to port.

Some would return after the hurricane, he said, while others were scheduled to leave for training soon anyway and will possibly start those exercises after the hurricane rather than return immediately.

The Coast Guard Barque Eagle and Cutter Morro Bay, as well as the Plum Island ferries, are planning to dock at the base during the storm.

The base and the commander of Submarine Group Two began planning the sortie Monday and some of the maintenance work on the submarines had to be finished quickly.

Friday, Rear Adm. Richard P. Breckenridge assumed command of the group from Rear Adm. Michael E. McLaughlin. Shortly after the ceremony, Breckenridge said that getting the subs ready quickly is "second nature."

"We have to surge and respond quickly and with agility, whether it's to get our submarines to safe waters or to hostile waters," he said in an interview. "That's what the Submarine Force is known for."

Over the next few days, Breckenridge said he would also focus on making sure the families of the sailors who left are taken care of.

Denno also expressed concern for the families, saying that there would be sailors at the base over the weekend who could go out into the communities if the families needed help.

The sailors will be safely submerged during the hurricane, Denno said, but "the toughest part is leaving your family behind. That's where my job comes in."

Meanwhile, on the lower base, sailors piled about 22,000 white, beige and green sandbags- 27 flatbeds full- in front of doors to the buildings, the most labor-intensive part of the preparations. Anything that wasn't bolted down also had to be brought inside the buildings to prevent damage from flying debris.

They were preparing for a worse-case scenario of 1 to 2 feet of water above some of the piers due to the storm surge. Denno said all of the preparations would be finished today. Only essential personnel will report to the base starting tonight.

j.mcdermott@theday.com