Honolulu Board of Water Supply officials and environmentalists are rightly raising more red flags at Red Hill, the Navy’s underground fuel storage facility. This time, they’re pointing to Navy testing on one of its massive underground tanks pertaining to corrosion.

In response to concern about the potential for leaks, the Navy has cautioned that its study is still in the works and conclusions based on preliminary information and targeted samples should be suspect. That’s a reasonable point. Any sort of public safety verdict must wait until final results are in, of course.

What’s wholly unreasonable, however, is the Navy’s foot-dragging to put in place much-needed fixes to substantially improve public safety in the aftermath of a 27,000-gallon fuel leak in January 2014.

The Red Hill Bulk Fuel Facility, near Pearl Harbor, continuously stores 187 million gallons of fuel for ships and jets in tanks that are about 75 years old — hurriedly constructed during the World War II era. They’re buried just 100 feet above a state-designated drinking water aquifer, which supplies flows to faucets from Moanalua to Hawaii Kai. A large-scale leak could be ruinous, with cleanup taking decades or deemed cost prohibitive.

After nearly four long years of vetting upgrades as part of an agreement with regulators — the U.S. Environmental Protection Agency and the state Health Department — the Navy earlier this month signaled a preference to patch the threat it created with the cheapest and least-protective option. Regulators should reject this proposal, which a Navy’s own report has described as “minimal changes to the status quo.” It’s simply unacceptable.

To responsibly protect Oahu’s groundwater quality and quantity, it appears that regulators need to make some noise. They should insist that the Navy install a more expensive — and clearly more effective — option of modern double-wall protection, which the BWS recommends.

Citing inherent environmental risks tied to underground storage, Naval Base Kitsap’s Manchester Fuel Depot in Washington State is now in the process of replacing its underground fuel storage tanks — also WWII vintage — with state-of-the-art, above-ground steel tanks. Hawaii would be wise to quickly follow suit.

While the Manchester facility ranks as the Department of Defense’s largest single-site fuel terminal on the mainland, storing 75 million gallons of military-grade fuel, Red Hill stores more than twice as much — in tanks each large enough to contain Aloha Tower — and is the largest site in the Northern Hemisphere. It follows that we need to safeguard against potentially bigger environmental risks.

According to the BWS, which was briefed by the Navy on preliminary data in the ongoing Red Hill testing, a sampling of steel plates from a tank showed advancing corrosion. Also worrisome to the BWS and the Sierra Club, which has been monitoring the facility issue for years, was early data indicating a thinning of parts of the tank’s original, quarter-inch-thick steel liner.

Regarding the data, Rear Adm. Brian Fort, commander of Navy Region Hawaii and Naval Surface Group Middle Pacific, has said: “We have not and will not rush to judgment or conclusions, and we will continue to keep the drinking water safe, no matter what.” He added, “There is much more work to do in studying, analyzing and then implementing all the right initiatives at Red Hill.”

Regulators must carefully weigh the final results of corrosion testing, which are due in late October.

But with each tank’s aging steel and surrounding concrete apparatus standing between the fuel and any leakage into the environment, the red-flag response to even early data is justified. And the Navy’s “right initiatives” should entail a robust secondary containment — or facility replacement, through which Red Hill’s 20 tanks are retired and the fuel is relocated away from potable ground water supplies.