HONOLULU — The U.S. Navy is pushing for the least expensive option in upgrading 20 massive underground fuel tanks that pose risks to a major source of drinking water on Oahu.

The Navy has assessed six options to improve the aging tanks at the Red Hill Underground Fuel Storage Facility, telling regulators last month that it would recommend the option with “minimal changes to the status quo,” the Honolulu Star-Advertiser reported Monday.

In a deal with the Environmental Protection Agency and the state Department of Health, the Navy agreed to examine options to improve tank safety after 27,000 gallons of fuel leaked at the facility in 2014. The EPA and the state Health Department must sign off on the Navy’s selection to improve the tanks built in the 1940s.

"As stewards of your tax dollars, the Navy will continue to pursue the most affordable option that achieves the safety and protection of our drinking water," said Mark Manfredi, the Navy's regional program director of Red Hill.

The affordable option would include coating the tanks and nozzles to prevent corrosion and upgrading the leak detection system. That could cost up to $25 million per tank.

This option has concerned environmental advocates and officials with the Honolulu Board of Water Supply. Choosing a tank within a tank option would better protect the island’s water, said Ernie Lau, manager and chief engineer of the water board. The affordable option maintains the existing steel exterior.

"This is basically the status quo with a little more of a coating on the bottom of the tank," Lau said.

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The Navy is reviewing its fuel requirements in the Indo-Pacific region, which casts uncertainty on the tanks' future, said Bruce Anderson, director of the state Health Department. That review could take another year to complete.

"My thinking is, given the uncertainty of the future of those tanks, it is not unreasonable that they would want to maintain them as they are with these upgrades and then come back to us with a final recommendation on what they propose over the next five years," Anderson said.

The state Health Department is planning to hold public meetings on the Navy’s choice in the coming months.