The U.S. Navy has concluded that a May 6 spill at its Red Hill underground fuel farm was due to a control room operator’s failure to follow correct procedures.

Navy officials said today, after releasing the results of its investigation, that additional safeguards have been implemented at the facility and that “appropriate action” has been taken against the civilian employee who made the error.

“This release was not due to age of infrastructure, corrosion or the equipment condition,” said Capt. James Meyer, commanding officer of Naval Facilities Hawaii.

The release, of what the Navy now estimates was 1,618 gallons of jet fuel, became a flash point in an increasingly contentious battle over the future of the World War II-era facility, with the Hawaii Sierra Club saying at the time that it was further evidence that the aging facility poses a grave threat to Oahu’s drinking water supply.

Wayne Tanaka, executive director of the Hawaii Sierra Club, said the Navy’s report did little to assuage his concerns about the facility that contains 20 massive underground fuel tanks and sits 100 feet above an aquifer that serves as a major source of drinking water for Oahu.

“They really just reinforce what we already know, which is there is no way to eliminate human error,” said Tanaka.

The Hawaii Department of Health, which regulates the facility, said it needed more time to comment on the report, which it received Monday.

The Navy said that the May 6 fuel release was not from any of the underground tanks, but rather a connecting pipeline. The Navy was transferring fuel from one tank to another, when a control room operator failed to follow valve procedures, the Navy said.

The operations order “lays out in excruciating detail what valves are supposed to be open and when,” said Capt. Albert Hornyak, commanding officer at the Naval Supply Systems Command’s Fleet Logistics Center Pearl Harbor.

He said failure to follow that protocol resulted in a rapid surge of pressure in the pipeline, causing the spill.

“It’s almost like building a Lego,” said Hornyak. “You go through and you have your steps and you follow those steps, and if you don’t follow those steps exactly, the picture on the box that you are trying to build toward is not going to look the same.”

Hornyak would not specify what action’s were taken against the control room operator.

He said operators undergo extensive training, but as an added safeguard the Navy has added an additional operator during fuel transfers to provide a “second set of eyes.”

The Navy has also increased the sensitivity of its alarm systems to detect pressure and fuel level irregularities.

The Navy’s investigation concluded that all but 38 gallons of the spilled fuel was recovered and there was no indication that the fuel had been detected in groundwater monitoring wells.