The Navy has confirmed that an approximately 1,000-gallon fuel leak was detected Thursday at the troubled Red Hill fuel farm, a World War II-era facility that came under criticism following a 27,000-gallon fuel release in 2014.

Navy Region Hawaii said in an email Friday that “personnel responded to and contained a reported fuel release, initially assessed at approximately 1,000 gallons, from a pipeline at the Red Hill Bulk Fuel Storage Facility Thursday night. As designed, the fuel release went into a containment system in the tunnel where the pipeline is located, and the fuel was recovered. There appears to be no release into the environment.”

The Navy said it is investigating the cause of the release and “is fully committed to environmental stewardship and continues to work closely with federal and state agencies,” including the state Department of Health and U.S. Environmental Protection Agency, “to protect the environment as we operate the Red Hill facility.”

But David Kimo Frankel, an attorney for the Sierra Club of Hawaii, said in a news release, “It’s not surprising that the Red Hill tanks leaked. They have a long history of leaking. And the Navy itself said there was a 27.6% chance of the tanks leaking up to 30,000 gallons of fuel every single year.

“It’s only going to get worse from here. The tanks need to be drained,” Frankel said.

Studies have detected petroleum contamination in the groundwater beneath the tanks, according to the Sierra Club. Since its construction in the 1940s, it is believed the tanks have leaked more than 178,434 gallons of fuel, the organization said.

“This latest leak proves, once again, that the 78-year-old Red Hill fuel tanks are deteriorating and pose a serious threat to drinking water for hundreds of thousands of Oahu residents. It’s time to retire the tanks,” Hawaii Peace and Justice’s Kyle Kajihiro said in a Sierra Club statement.

The Department of Health is conducting a contested case hearing to determine what terms the Navy needs to follow to continue to operate the tanks.

Opening arguments were made Feb. 1 debating the merits of awarding a five-year state operating permit for the Navy to continue storing up to 187 million gallons of fuel at Red Hill.

While the Sierra Club believes the 20 tanks should be relocated and the Honolulu Board of Water Supply maintains they should be moved or rebuilt with secondary containment, the Navy said the tanks and monitoring have improved greatly.

“Since 2014 the Navy has a different facility, both in its physical construct and how it’s operated and monitored each and every day,” Navy lawyer Karrin Minnot said during the hearing.

Twice a year the tanks are tested for leaks using a method certified by third-party verifiers, Minnot said.

“The Navy’s procedures for inspections and repairs at Red Hill go above and beyond the industry standards,” she said.

But Frankel previously said that from the beginning the underground fuel tanks leaked. Tank 16 was leaking 546 gallons a day in 1949, he said.

“The Red Hill tanks cannot be, and are not operated, in a manner that is protective of our (groundwater),” Frankel said. “There is a practical alternative: build new tanks above ground in a safe location (and) relocate the fuel — just as the Navy did on the mainland.”

Military officials say the fuel supply is a crucial — and massive — war reserve for the Pacific that would be hard to replicate with above-ground tanks. The cost would be in the billions of dollars.

The Defense Department has invested over $200 million and plans to spend over $400 million more “to ensure the facilities remain safe,” Minnot said.

Located 2.5 miles from Pearl Harbor, Red Hill has 20 vertically arrayed 250-foot-tall underground storage tanks that were constructed between 1940 and 1943, with each tank capable of holding 12.5 million gallons.

In response to a 27,000- gallon fuel spill in 2014 from Tank 5, the EPA and state Health Department negotiated an ongoing administrative order of consent requiring the Navy to make fuel safety improvements.

Much of the concern centers on the tanks’ location 100 feet above the water supply aquifer, which lies in saturated volcanic rock.

In 2018 the Health Department amended its underground storage tank rules to, among other things, require previously exempt field-constructed tanks such as Red Hill to follow state requirements.

The Navy applied for a five-year permit, and the Sierra Club and Board of Water Supply requested a contested case hearing. The permit and consent order are separate procedurally.

Both actions have focused on the age and construction of Red Hill, a single-wall tank system of quarter-inch-thick welded steel plates backed by 2 to 4 feet of concrete.

Minnot, the Navy lawyer, said evidence shows “the continuing operation of Red Hill is protective of human health and the environment.”

The 2014 fuel release “was certainly unfortunate, but it was not from corrosion, or deterioration of the Red Hill tanks,” she said.

The contractor error that led to the release “would not be possible under the new and improved tank inspection, repair and maintenance protocol” that was approved by the state Health Department and EPA in 2017, Minnot said. Officials also faulted “ineffective response and oversight.”

The Navy has long maintained that the water from the Red Hill shaft down-­gradient from the fuel farm, and which supplies Joint Base Pearl Harbor-Hickam, is completely safe to drink.

The Navy “is fully compliant with every one of Hawaii’s underground storage tank regulations,” Minnot said.

U.S. Sen. Mazie K. Hirono, D-Hawaii, said in a statement that she was updated on the situation by Adm. John C. Aquilino, who heads the U.S. Indo-Pacific Command, and was assured “the detection and response system worked and the fuel release is contained.”

Hirono, who chairs the Senate Armed Services Subcommittee on Seapower, said Aquilino vowed to keep her office informed as the Navy completes its investigation and cleanup. She said the admiral also will review the notification process “to ensure all appropriate parties are promptly informed. This incident reaffirms the need for clear and transparent information to be communicated in a timely manner.”