The tanks at the Red Hill Bulk Fuel Storage Facility will be drained after fuel leaked into the drinking water. Nearly 6,000 people became sick, and 4,000 military families were displaced from their homes, the Associated Press reported.

In late November last year, jet fuel leaked from the storage facility and contaminated the drinking water in over 90,000 people’s homes, businesses, offices and schools within and surrounding Pearl Harbor, which is on the island of Oahu, about 10 miles west of Honolulu.

Several days later, people began complaining their tap water smelled like fuel and had an oily sheen. People reported physical ailments such as nausea, rashes, stomach cramps, headaches and vomiting after drinking the water. After testing, traces of petroleum were found in the water, which prompted thousands of Navy family members to be moved from the base.

After months of debate, the fuel tanks will be drained. Before the drainage can occur, officials must first determine the safest way to proceed. The process is expected to take about a year, according to the AP.

The decision to drain the tanks was based on the Pentagon’s assessment but is in line with the state Department of Health’s previous ruling in favor of draining fuel from the tanks, the AP said.

The department upheld the governor’s order to drain the tanks after officials became concerned the fuel could contaminate Oahu’s drinking water. The tanks sit just 100 feet above an aquifer that is shared by the Honolulu Board of Water Supply and the Navy.

“Defueling safely will require a coordinated effort, and the delegation will do everything possible to support this effort,” Hawaii’s congressional delegation previously said in a statement. “Clean drinking water is essential to our health and safety, and our future—we all agree this cannot be compromised for anything.”

The fuel storage facility consists of 20 tanks that were built into a mountain ridge to shield them from a potential aerial attack, the AP said. Each tank holds about 12.5 million gallons and is approximately 25 stories high. Collectively, they can hold up to 250 million gallons of fuel. The tanks are at less than half capacity right now, and two of the tanks are empty.

It’s unclear exactly how the petroleum leaked into the water, but officials are investigating a theory that the jet fuel spilled from a ruptured pipe last May. An estimated 14,000 gallons of jet fuel ultimately spilled, and some fuel made its way into the water distribution system for the Navy’s Red Hill Bulk Fuel Storage Facility.

Update 03/07/22, 4:50 p.m. ET: This story has been updated with more background and information.