The US Navy has maintained fuel tanks at Pu‘u Kapu (Red Hill) since World War Two. There might be a leak:

The Navy, in coordination with the state Department of Health and other agencies, is investigating a possible leak of aviation fuel—primarily consisting of kerosene—from a tank at the Red Hill Underground Fuel Storage Facility.

Samples of ground water and drinking water in the vicinity have been collected and are being tested, the Navy said this evening in a news release.

Navy officials said fuel operators on Monday detected a fuel-level discrepancy in the tank, which holds JP-8 aviation fuel. 

The possible loss of fuel from the tank prompted the Navy to immediately begin transferring fuel to another tank at the facility, according to the release. The transfer process may take up to five days to complete, officials said.

There’s interesting background about the fuel tanks here. Among other trivia, there are 20 fuel tanks, each 20-stories tall.

UPDATE 1/21/14: The Navy issued a statement saying that less than 20,000 gallons of JP-8 jet fuel leaked from Tank 5. Water is safe to drink, according to federal standards, but local agencies are continuing to monitor the situation. From the Star-Advertiser:

Test results from five drinking water wells in the vicinity taken by the Honolulu Board of Water Supply have shown no fuel contamination. The board is moving forward with its own monitoring plan of the drinking water that has been approved by the state Department of Health. HBWS drinking water wells that were shut down as a precaution are being brought back into service as of today, according to the release.