The Navy said Tuesday it awarded a $9 million contract to AECOM Technical Services Inc. of Los Angeles for further studies directed at major renovation of Pearl Harbor Naval Shipyard to meet 21st-century threats.

The Shipyard Infrastructure Optimization Program is a 20-year, $21 billion effort to modernize infrastructure at the nation’s four naval shipyards through dry-dock repairs, restoring and optimally placing shipyard facilities and replacing aging and deteriorating equipment, Naval Facilities Engineering Command Pacific said.

“Award of this task order is the next major step toward executing a strategic infrastructure plan to create the shipyard of the future,” Joanna Victorino, deputy program management officer for the Navy’s improvement effort at Pearl Harbor, said in a release.

The Navy in February said it was “investigating” building a new dry dock at Pearl Harbor — its first since World War II — and using the excavated material to fill in Dry Dock 3, where a first-of-its-kind “dry dock production facility” would be built to improve waterfront efficiency.

The Hawaii plan is expected to involve billions in construction that will benefit local workers.

A surge in demand for attack submarines due to competition with China and the lengthening of Virginia- class subs to carry more missiles has the Navy looking at building its first new dry dock at Pearl Harbor since 1943.

Four dry docks are in use. The oldest of them, Dry Dock 1, at 1,002 feet, was completed in 1919. Dry Dock 2, at 1,000 feet, was finished in 1941, according to the Defense Department.

Dry Dock 3, which is only 497 feet long, was complet­ed in 1942, while Dry Dock 4, at 1,088 feet, was finished in 1943.

Three of the dry docks are used for submarine work, while No. 4 is for surface ship repair.

Newer Virginia-class subs, at 377 feet, are longer than the older Los Angeles-class they are replacing, and those built with what’s known as a Virginia Payload Module will have an additional 84-foot midbody section with four vertical launch tubes capable of firing 28 additional Tomahawk missiles.

The improvement ups the $3.2 billion sub’s torpedo- size weapons to 65 from about 37, a congressional report said.

According to the U.S. Government Accountability Office, all but Dry Dock 3 at Pearl Harbor can accommodate the new 460-foot lengthened Virginia subs.

The last major shipyard work on Los Angeles-class submarines is expected in 2022. “After that, the shipyard will focus on the Virginia class,” the Navy said.