YOKOSUKA, JAPAN — Human error was behind a small oil spill in Yokosuka Harbor last week, U.S. Navy officials said.

About 20 gallons of oil leaked from the USS Fitzgerald during a refueling operation while the Aegis destroyer was in dry dock at Yokosuka Naval Base on Feb. 28.

An oil skimmer and oil-containment boom were deployed but oil escaped into Yokosuka Harbor, officials said. The Japanese Coast Guard discovered the sheen and helped disperse it with assistance from the Japan Maritime Self-Defense Force and Japanese Coast Guard, said Capt. Greg Cornish, Yokosuka Naval Base commanding officer.

“The cause appears to be an isolated case of human error so we are taking steps to prevent a similar incident from occurring,” Cornish said. “There was no damage to the environment, no injuries and only a slight disruption of work. We appreciate the cooperation and assistance of the JMSDF and Japanese Coast Guard.”

The spill was the third recorded this year. The first was Jan. 17 off the USS Kitty Hawk at Yokosuka; the second Feb. 27 off the USS John McCain in Kagoshima, Japan.

“It was extremely disappointing that it had happened again,” said Nagatoshi Esashi, Yokosuka City’s Military Affairs Office chief.

He visited Cornish on Friday, expressing the city’s concern and asking that preventive measures be taken.

“We know that the Navy is making an effort to prevent it, but the issue is if the policy reaches to the rank and file,” Esashi said. “We ask the Navy to give thorough education to all the personnel who actually work at the site.”

The city takes every oil leak seriously, he added.

Esashi said Cornish offered apologies and assurances that the base would work to prevent a recurrence.

The incident is under investigation, a base spokesman said Monday.

Sign Up for Daily Headlines

Sign up to receive a daily email of today's top military news stories from Stars and Stripes and top news outlets from around the world.

Sign Up Now