The Navy opposes proposed state legislation that would require the military’s Red Hill fuel tanks to have secondary, or double-­walled, containment by 2027 — and so does the state Department of Health.

The Health Department said in written testimony on Senate Bill 1259 that its “top priority is the protection of public health and the environment,” but “due to the unprecedented and massive scale of this project, rushing to implement secondary containment may actually not result in the best practicable solution.”

The Navy, Health Department, U.S. Environmental Protection Agency and Defense Logistics Agency are parties to an “Administrative Order on Consent” established after a 27,000-­gallon fuel leak in 2014 at Red Hill to minimize the threat of future releases.

That agreement “remains the best and most comprehensive path forward” to protect drinking water while requiring the Navy and Defense Logistics Agency to improve the facility, the Health Department said.

The Navy said the World War II-era steel-lined and concrete-encased tanks at Red Hill are not leaking, and that the fuel farm “is of vital strategic importance to our nation and U.S. Pacific Command.”

Tank upgrades have to be evaluated, and “secondary containment is currently being considered and may be the best tank upgrade option,” the Health Department wrote, placing emphasis on the word “may.”

Senate Bill 1259 passed out of the Committee on Agriculture and Environment and the Committee on Public Safety, Intergovernmental and Military Affairs last week.

The Red Hill Bulk Fuel Storage Facility, the state’s largest field-constructed underground tank system, stores more fuel in a single location — up to 187 million gallons per day — than any other underground tank system in Hawaii, according to the bill.

Hawaii administrative rules exempt field-­constructed underground storage tanks, including Red Hill, from the requirements that must be met by owners and operators of other underground tanks.

Red Hill has 20 underground tanks, each able to contain up to 12.5 million gallons of fuel. The Honolulu Board of Water Supply said the tanks are 100 feet above a drinking water aquifer that supports the Halawa Shaft and Moanalua wells, which supply 25 percent of the drinking water to residents from Moanalua to Hawaii Kai.

The Navy’s well 2254-01 is 3,000 feet west and downhill from the underground storage tanks, drawing 4.4 million gallons per day and supplying 24 percent of the Pearl Harbor Water System, according to a 2008 report.

The Sierra Club of Hawaii, which “strongly supports” Senate Bill 1259, noted that the facility has historically experienced fuel leaks, and said in written testimony that in the three years since the January 2014 spill, “the Navy can demonstrate little progress towards cleaning up existing contamination or guaranteeing against future leaks.”

It said that secondary containment for fuel storage tanks is a minimum requirement that all modern gas stations follow. The Senate bill would require field-­constructed underground storage tanks with capacities greater than 50,000 gallons to upgrade with secondary containment by July 1, 2027, or be taken out of service and permanently closed by July 1, 2030.

The Health Department said the administrative order parties selected six Red Hill tank alternatives to be evaluated. The final version of the “Tank Upgrade Alternative” study — to include the possibility of double-­walling the tanks — is due out late this year, officials said.

“Subsequently, the department and EPA will select the best available practicable technology as the first required upgrade that the Navy must implement in order to continue to operate their tanks,” the Health Department said.

Capt. Richard Hayes, commander of Naval Facilities Engineering Command Hawaii, asked in testimony that the proposed bill be deferred to allow the Health Department “to continue its work with the EPA and the Navy.”

“We respectfully remind all stakeholders that there are no ‘off the shelf’ solutions to many of these requirements,” Hayes said. “Assessing the best available practicable technology requires consideration of alternatives, including some untested alternatives, as well as considering public input.”

Double-walled tank modifications have not been tested or proved on the scale of Red Hill, particularly within the timeline set by the bill, he said.

“We remain committed to protecting drinking water in Hawaii as an unquestioned, non-negotiable requirement,” Hayes said. He said testing confirms drinking water from the Red Hill shaft is safe.

Over $200 million has been spent on improvements at Red Hill since 2006, and 12 groundwater monitoring sites are arrayed around the facility to detect any fuel migration toward the drinking water source, Hayes said.

Prior to the 2014 leak in Tank 5, contractors performed maintenance on the empty tank. Hayes said poor workmanship, poor oversight by the Navy and a lack of operator “procedural compliance” led to the leak — issues that have been addressed and corrected.

Testing of the Red Hill fuel tanks between November and early February found no leaks, the same as results from 2015, the Navy said.