Groton — For the first time in a decade, Electric Boat is simultaneously working on two submarines in its main building shed.

The first module for the future USS Illinois, the 13th member of the Virginia class, arrived by barge from EB's Quonset Point facility Tuesday. It was placed next to the North Dakota, the 11th of the class.

Two submarines have not been side by side in Building 260 since 2003, when EB was building the USS Jimmy Carter and the USS Virginia, the first of the class.

"This is our first step to ramping up in Groton to two boats a year," said Todd Beardsley, the ship's manager at EB for the Illinois (SSN 786).

The first module for the follow-on submarine at EB normally arrives after its predecessor is put into the water for the first time. The "float off" for the North Dakota (SSN 784) will not happen until September or October. That submarine is on track for the fastest delivery of the class yet.

"Everything keeps getting earlier and earlier, so we're ready to go to two boats a year," Beardsley added.

The Navy began buying two submarines per year in 2011 but the Groton waterfront is where the final assembly and testing of submarines is done, so it is not projected to have a steady workload until 2015. EB is under contract to build the 11th through the 18th ships of the class, with Newport News Shipbuilding in Virginia.

About 600 people in Groton and Quonset Point are working on the Illinois. Next year, once all four modules are in Groton, nearly 1,000 people will be working in the yard on the submarine.

The arrival of the first module, in this case, the forward half of the engine room, is a milestone, Beardsley said, because major work on the submarine can now begin in Groton. The next task is to attach the reactor compartment to the 50-foot-long cylindrical module, he said.

Cmdr. Jess Porter, the submarine's commanding officer, arrived in Groton on Monday to begin assembling the crew. The first group, about 35 people, will spend the next few weeks in school in Schenectady, N.Y., learning how to operate the propulsion plant, Porter said.

Porter said being in command of a new Virginia-class submarine is "a phenomenal opportunity" because the culture for the ship is set in the early stages of construction.

"That culture, in large measure, goes a long way toward building that ship to a viable and powerful platform," he said.

First Lady Michelle Obama was named sponsor for the submarine last year.

Construction on the Illinois began in March 2011. The submarine is contracted to be delivered to the Navy in 66 months, on Aug. 31, 2016. Beardsley said his goal is to finish earlier in 2016 and to beat whatever record the North Dakota sets when it is delivered in early 2014.

Female officers will begin reporting aboard Virginia-class submarines in January 2015. Porter said that if women are assigned to the Illinois, "my ship will be ready to support that."

Porter, 46, who is from Pocatello, Idaho, took the USS Missouri through the delivery and commissioning process as that submarine's executive officer. He spent 12 years as an enlisted nuclear electrician's mate in the surface fleet before being commissioned as an officer and joining the submarine force. He served on the USS Michigan and the USS Connecticut.

The shipyard is a challenging environment, Porter said, but the crew will come away from it knowing "that ship inside and out." Porter and Beardsley met for the first time on Wednesday so Porter could see the hull section.

Outside of the bustling building shed, EB's three graving docks are currently filled with three submarines undergoing repairs. Beardsley, who has worked at EB for 14 years, remembers when the Jimmy Carter and the Virginia were there.

"This is by far the busiest we've been since then," he said.