In January 2014 the U.S. Navy reported to the Hawaii Department of Health that approximately 27,000 gallons (102,000 liters) of jet fuel had leaked from an underground tank at the Red Hill Bulk Fuel Storage Facility, which supplies fuel to Pearl Harbor naval base. The leak raised serious concerns over the risk of contamination spreading to important water supplies. The fuel facility consists of 20 tanks and is located just 100 feet (30 meters) above an aquifer that hundreds of thousands of residents living in and around Honolulu depend upon for their fresh drinking water. Officials from the Hawaii Department of Health and Honolulu Board of Water Supply inspected the fuel facility and were able to see the leaking tank, tank 5, first-hand. Documents filed with the health department showed that there had been a previous leak at the Red Hill facility in 2001-2002 with efforts to undertake follow-up monitoring. Reports indicated that even at that time the state had doubts over the adequacy of the monitoring system for preventing fuel from getting into drinking water. Detecting and repairing a leak from underground tanks is far more difficult than with above-ground facilities. In April 2014, as contractors began to inspect the tank and the Navy sought a contractor to ‘define the nature, extent and magnitude of soil and groundwater contamination beneath Tank 5’, Honolulu City Council members joined a chorus of officials urging the Navy to make improvements to prevent what the Honolulu Board of Water Supply warned could be a serious hazard to the water supply if a powerful earthquake in the area were to disturb the ground. The Board of Water Supply and Hawaii Department of Health said that, to date, there were no indications that fuel had contaminated the groundwater aquifer, but elevated levels of hydrocarbons had been detected in soil vapor samples at nearby monitoring points. There were particular concerns over the possible threat to two wells, Halawa Shaft and and Moanalua Shaft, accounting for 25 per cent of the water supply to the area between the residential neighbourhoods of Moana-lua and Hawaii Kai. And a long history of fuel leaks from the Red Hill facility came to light. Water officials said the Navy had reported dozens of fuel releases, adding up to a volume of about 1.2 million gallons (4.45 million liters), but the Health Department had not informed Board of Water Supply officials until the most recent leak was being discussed. A Navy report from 2010 had suggested that fuel contamination might be moving in the direction of country drinking water supplies.