Briskly constructed during the World War II era, the Navy’s underground fuel storage facility in the hills above Pearl Harbor — the largest such tank farm in the Northern Hemisphere — was a state secret until the early 1990s, when it was declassified.

A few years later, the American Society of Civil Engineers placed the facility alongside Hoover Dam, the Eiffel Tower, Panama Canal and Statue of Liberty as an engineering marvel, a buried historic landmark.

But along with accolades, the disclosure has rightly prompted leak-related worries in municipal and environmental circles because Red Hill’s set of 20 aging cylindrical tanks — each massive enough to swallow a 20-story building — are perched just 100 feet above Oahu’s primary aquifer, which supplies a quarter of the water consumed in urban Honolulu.

The Navy and regulatory agencies are now working on a proposal for a 20-year-plan to reduce any risk of leaks and fuel contamination. After nearly four long years of vetting possible tank upgrades, it appears likely that next month the Navy will seek Pentagon support for the cheapest and least-protective option under consideration.

Regulators — the U.S. Environmental Protection Agency and the state Health Department — should reject this proposal as insufficient. And Hawaii’s congressional delegation, which will eventually weigh in on funding, should heed red flags raised by Honolulu Board of Water Supply (BWS) officials and others.

During a public meeting at the state Capitol last week, Navy officials said the only leak at Red Hill since 1988, when underground fuel storage tank regulations were implemented, was in 2014, when 27,000 gallons of fuel were released from one tank. And that leak, they asserted, was caused by contractor error and poor Navy oversight — not crumbling structure.

Even so, Navy reports indicate that there were likely dozens of historical leaks at the facility.

In attendance at the meeting was BWS Manager and Chief Engineer Ernie Lau, who challenged stated assurances by passing out copies of documents signed by the Navy in 2002 that reported leaks to the Department of Health (DOH). In response, Navy officials said at least one report had turned out to be a false alarm, and that all tanks currently in service had passed leak detection tests.

The DOH further muddied the matter. Keith Kawaoka, state deputy director for environmental health, said: “We’ve had reports, anecdotally, a lot of them, of (Red Hill) tanks leaking in the past and hundreds of thousands of gallons leaking, but nothing verifiable.” Hardly reassuring. If the state can further explain its verification efforts, that might silence skeptics. But that has not happened.

While the Navy appears to be dragging its feet in selection of an upgrade — required by an Administrative Order of Consent with regulators in the aftermath of the 2014 leak — it hasn’t been idle. Officials point out that since then more than $45 million has been spent to improve the facility, such as via a high-tech leak-detection system, and protect the environment.

Further, the Navy contends that in this case, in the interest of fiscal responsibility, the most expensive option is not the best solution. It maintains that although the tanks are nearly 80 years old, they were built to last and need only what a Navy report has described as “minimal changes to the status quo.”

Such confidence seems misguided. Regardless of the Red Hill’s structural integrity, its tanks are buried above groundwater that the BWS taps for drinking water, flowing to faucets from Moanalua to Hawaii Kai. A large-scale leak of any sort could be ruinous. Cleanup could take decades or be deemed cost-prohibitive. Then what?

In the interest of public health and safety as well as environmental responsibility, regulators and our elected leaders should insist that the Navy install a more expensive — and clearly more effective — option of modern double-wall protection, which the BWS recommends.