Secretary of Defense Lloyd Austin, in his announcement Monday that the Navy would empty and permanently shut down its underground Red Hill fuel farm, cited both health risks and a need to build a more “resilient” military fuel infrastructure in the region.

The facility’s 20 massive underground tanks, which hold up to 250 million gallons of fuel, sit above a critical aquifer that provides most of Honolulu’s drinking water.

In November, fuel that leaked from the aging World War II-era facility contaminated the Navy’s water system, which serves 93,000 Oahu residents, including military housing, schools and local businesses.

Austin seemingly backed long- argued contentions by critics that the facility — which holds reserves for what the Pentagon considers its priority theater of operations — is outdated and obsolete.

The U.S. military conducts nearly constant operations across the Pacific region as tensions simmer with China. The Chinese military has stationed troops and weapons on disputed land formations in the South China Sea to assert its claims against the objections of neighboring countries.

In recent years the U.S. Pacific Fleet has stepped up “freedom of navigation operations” in the region. Meanwhile, U.S. Pacific Air Forces adopted what it calls Agile Combat Employment, frequently moving aircraft to airstrips scattered across the Pacific to make them harder to hit in the event of a missile strike during a conflict.

“To a large degree, we already avail ourselves of dispersed fueling at sea and ashore, permanent and rotational,” said Austin. “We will now expand and accelerate that strategic distribution.”

But after years of relying on Red Hill, truly transitioning will be a massive endeavor for the Department of Defense.

“Closing Red Hill is straightforward, but shifting to a resilient fuel architecture will be difficult,” said Timothy Walton, a fellow at the Hudson Institute’s Center for Defense Concepts and Technology in Washington, D.C.

“We will defuel Red Hill and reposition the fuel to land and afloat locations,” Pentagon spokesman John Kirby said Monday during a media briefing. “This will meet our national security objectives by better positioning the United States to meet future challenges in the Pacific region while ensuring environmental stewardship and protecting the population.”

“Afloat locations” refers to using tanker ships to store fuel from the Red Hill reserves, something U.S. Rep. Kai Kahele, D-Hawaii, cited as a potential partial solution to the crisis in February during a mews conference at the state Capitol. However, it’s not clear how many tankers the military might need.

“We think we’ve got enough to be able to get us in the right direction,” said a senior Pentagon official who agreed to speak on background. “It’s not going to be enough long term. I mean, obviously, we’re gonna have to offset the loss of Red Hill, and we think that one way to offset that is additional hulls in the water.”

The Pentagon official added, “We’re still just now at the beginning of working through the process of determining exactly how many hulls and how fast can you get them. And if you can’t get them fast enough, would you need to pull some from elsewhere?”

The military currently has access to about 10 tankers in the Pacific. The Tanker Security Fleet program, created by Congress in 2020, could provide a stipend to make 10 more commercial tankers available in times of conflict or emergency and could generate a small net increase of five or so tankers in the U.S.-flagged fleet. But the program remains unfunded.

Walton also points out that in a 2016 study, U.S. Transportation Command identified wartime requirement for 86 tankers — currently, only about 10 U.S.- flagged tankers are available to the Defense Department. The U.S. military has at times turned to foreign- flagged tankers.

“DOD needs to gain assured access to more maritime tankers,” said Walton. “Hoping requisite numbers of foreign tankers will be available in a conflict is imprudent. Global spare tanker capacity significantly fluctuates, and a large and growing portion of tanker fleets are PRC (China) controlled or subject to PRC coercion.”

However, it’s unclear how quickly more ships can be built or acquired.

On land, officials advised Austin to look at existing fuel facilities in places like Guam, Japan and South Korea — many of which are much closer to potential flashpoints. Hawaii is a critical mid-Pacific fueling and maintenance point for ships and aircraft but is relatively far from what commanders consider their main areas of focus.

“That resonated very much with Secretary Austin, given that he has made it clear that China is the pacing challenge for this department,” said the senior defense official. “So having the fuel closer to where the forces are on any given day made a lot of sense for him.”

However, that in many ways flies in the face of efforts of military planners who worried that keeping fuel in the Western Pacific would make it vulnerable to enemy attacks and blockades by enemy forces cutting off supply lines, putting the fuel in a “contested” environment during a conflict.

The underground Red Hill facility is considered a “hardened” fuel store, one that is much harder to attack for enemy forces during a conflict.

Military planners already made some efforts to spread fuel around the Pacific. While fuel moved from Asia has made its way to Red Hill, this year construction began for a new facility near the Australian city of Darwin, which would be above ground, where U.S. Marines are set to have a larger presence. But analysts argue having some underground facilities remains critical.

“Hardened underground fuel stores were necessary in 1943, and given potent (Chinese) People’s Liberation Army strike capabilities, they are still necessary today,” said Waldon. “This will require DOD to build new hardened underground fuel stores in other locations such as Alaska, the Marianas, Compact States, and Australia. These should complement or replace planned DOD projects that are building vulnerable, above ground stores in places like Darwin and Tinian (in the Marianas).”

Underground fuel facilities are more expensive and harder to maintain than above-ground tanks. The U.S. military has closed other underground facilities in California, Washington state and the Marshall Islands and transitioned to above-ground tanks to cut costs.

But that led to the military consolidating more of its underground fuel reserves in the Red Hill tanks above Oahu’s aquifer.

Walton acknowledges that underground tanks pose more environmental risks than above-ground ones, but stressed that not all of them sit above aquifers and that new technology and engineering techniques, as well as more deliberate placement, can mitigate those risks.

“New double-hulled hardened underground storage tanks can be built in an environmentally conscious manner” that allows for very detailed monitoring and maintenance, said Walton.

Pentagon officials say Red Hill’s role as a fuel storage facility is over — but they haven’t ruled out the possibility that it could continue to serve military functions.

“As Red Hill is closed as a bulk fuel storage facility, it could be repurposed into a hardened underground command and control bunker,” said Walton. “Many important command and control facilities on Oahu are in unhardened, above-ground buildings that can be easily targeted. Placing some of those facilities within Red Hill’s caverns could enhance their survivability.”