HONOLULU (AP) — The Honolulu Board of Water Supply said Thursday it has detected a small amount of a chemical naturally occurring in coal, crude oil and gasoline in a monitoring well near a Navy fuel storage facility that spilled jet fuel last year.

The utility said in a news release it found “very low levels” of the chemical, polycyclic aromatic hydrocarbons. It said it shared its data with the state Department of Health and the U.S. Environmental Protection Agency and both agencies agree these low levels are not expected to cause any health effects. Still, they agreed the situation needs attention and continued monitoring, the utility said.

The Board of Water Supply said the discovery heightens its concern that fuel spilled from the Red Hill Bulk Fuel Storage Facility is migrating through the aquifer located under the tank farm.

The utility has three wells that tap the aquifer to supply drinking water to more than 400,000 Oahu residents.

It shut down those wells in December when it learned fuel had flowed from the tank farm into a Navy drinking water well supplying water to 93,000 people on and near Joint Base Pearl Harbor-Hickam. That leak sickened some 6,000 of the Navy’s water users with nausea, headaches and other symptoms.

The utility worries fuel may travel through the aquifer’s porous volcanic rock from the area around the Navy’s well to its own wells, which could poison Honolulu’s own water supply. It has been calling on the Navy to swiftly remove fuel from the tanks to reduce the threat of further leaks.

The Board of Water Supply said it found the chemical in water samples taken from a well about 1,500 feet (457 meters) southeast of the Red Hill facility. It also found total petroleum hydrocarbons in the same samples.

Lydia Robertson, a spokesperson for Navy Region Hawaii, said the Navy hasn’t seen the utility’s data but would welcome the opportunity to review it.

Ernie Lau, the Board of Water Supply’s chief engineer, called the detections “warnings that we cannot ignore.”

“Our precious and irreplaceable water resources are at risk of further contamination every day the fuel remains in the Red Hill tanks,” he said in a statement. “We urge the Navy to expeditiously defuel and permanently close the Red Hill facility – Ola I Ka Wai,” he said, using the Hawaiian language phrase meaning “water is life.”

The military in April agreed to an order from the state of Hawaii to drain the tanks and close the World War II-era tank farm. But it says December 2024 is the earliest it can accomplish this.

A Navy investigation released last month said a cascading series of mistakes from May through November of last year caused 20,000 gallons (75,700 liters) of fuel to spill into its drinking water well. It blamed mismanagement and human error for the episode.

The leak was the most recent of a series of fuel spills from Red Hill dating to 2014.

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