HONOLULU (KHON2) — The Hawaii Department of Health is near completing a five-day contested case hearing that challenges the Navy’s permit application to operate its Red Hill fuel storage facility.

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The hearing was brought forward by representatives of the Sierra Club of Hawaii and Board of Water Supply who argue that Red Hill tanks pose a risk to Hawaii’s drinking water supply.

“The risk these tanks pose to the groundwater is huge,” Marti Townsend, Director of Sierra Club of Hawaii, said in an email Thursday. “Mathematicians have calculated that there is a 96% chance that a leak of 30,000 gallons will occur sometime over the next 10 years.”

On Monday, the Sierra Club and Board of Water Supply detailed the history of the Navy’s Red Hill fuel tanks leaking, dating back to 1949 when one of the tanks leaked 546 gallons per day. The latest incident was in 2014 when a tank leaked 27,000 gallons of fuel.

On Tuesday, it was revealed that only one tank in the Red Hill facility was inspected in compliance with the Navy’s inspection schedule, while 14 of the fuel tanks above the water supply did not undergo safety inspection. Tanks that are currently being inspected and repaired have been found to have defects, according to the Sierra Club.

On Wednesday, the hearing focused on assessing and managing all of the risks that come with storing millions of gallons of fuel 100 feet above Oahu’s aquifer.

The Navy’s position is that the tanks are in line with state law and regulations, and will not impact Oahu’s drinking water. However, the Sierra Club argues that the Navy continues to fail in demonstrating that the tanks are not a threat.

Friday is the last day of the hearing (watch here) from 8 a.m. to 4 p.m. and will feature witnesses from the Board of Water Supply. Closing arguments will likely be held on Monday.