Navy Secretary Carlos Del Toro launched one of the largest shipyard projects ever — a $1.7 billion dry dock expansion — at a ceremony Wednesday at the Portsmouth Naval Shipyard.

“Thank you for making Portsmouth a priority,” said Sen. Jeanne Shaheen, D-N.H., turning to Del Toro. “We hope you will come back often to see the progress.”

A makeshift dirt pile and a dozen shovels were lined up on the ground signifying the groundbreaking of the first of three “multi-mission dry docks” designed to allow for the simultaneous refurbishment of three next-generation nuclear-powered attack subs.

Officials said the dry docks are an effort to improve the timely return of ships and submarines back to the fleet following maintenance and modernization.

“Supporting our shipyards like Portsmouth strengthens the readiness of the Navy fleet and our national security,’’ said Shaheen, a senior member of the Senate Armed Services Committee.

The Navy will invest some $21 billion over 20 years to modernize infrastructure at its four shipyards — Portsmouth, Norfolk, Va., Puget Sound, Wash., and Pearl Harbor, Hawaii.

Shipyard commander Capt. Daniel Ettlich called the modernization program “a marathon, not a sprint” and used the occasion to deliver a “Meritorious Civilian Service Award” to shipyard employees Linn Lebel and Nathan Maher.

“Their dedication and perseverance despite numerous challenges and trials have delivered results,” Ettlich said.

Shaheen said the program will position Portsmouth to meet the Navy’s requirements for the next generation of submarines.

The Congressional Research Service briefed Congress last month on the Navy’s desire to procure a new class of nuclear-powered attack subs called the “Next-Generation Attack Submarine” or “SSN(X)” for short. It would replace the Virginia-class submarines in service in recent years.

Nick Pansic, vice president of Stantec, the firm that designed the Portsmouth dry dock, said the project is expected to provide 100 years of service.

When asked about the future impact of sea level rise, Pansic said, “The bigger impact is extreme weather.”

Dry docks allow ships’ entire hulls to be exposed for work. The vessel is floated into the dock, the gates are closed and the water is pumped out, leaving the ship resting on keel blocks high and dry.

This was Del Toro’s first visit to the shipyard after being sworn in a month ago as the 78th secretary of the Navy. He oversees an annual budget that exceeds $200 billion and is responsible for 900,000 sailors, Marines and civilian personnel.

Del Toro’s family emigrated from Cuba in 1962 when he was a year old. He grew up in New York City’s “Hell’s Kitchen” neighborhood near the Hudson River, where he said the ships inspired him to join the Navy. A graduate of the U.S. Naval Academy, he served 22 years in the Navy, retiring as a commander. He was the first commanding officer of the guided missile destroyer USS Bulkeley.

“I was very, very thankful to our country from a very early age,” he said. “I felt the need to serve.”

Del Toro, Ettlich and Greg Hill, an executive with 381 Constructors, the prime construction contractor, were called up one by one to a platform decorated with red, white and blue bunting while a Navy color guard stood at attention on the ground level. They were joined by Shaheen and Maine Sen. Susan Collins for the groundbreaking.

Sen. Maggie Hassan, D-N.H., Rep. Chris Pappas, D-N.H., and Maine Sen. Angus King looked on from front-row seats

A few hundred others, including shipyard personnel, officials from Portsmouth and Kittery, Maine, officers in dress whites and contractor representatives, looked on under clear blue skies.