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Bilge Water Leaks Forced Two Carriers to Return to Port Last Year

USS Nimitz under way with a full air wing on deck
USS Nimitz under way (USN)

Published May 16, 2023 9:57 PM by The Maritime Executive

The U.S. Navy has concluded its inquiry into drinking water-contamination incidents aboard two aircraft carriers last year and found that both were caused by bilge water leaking into the potable water tanks.  

On Sept. 16, while the USS Nimitz was operating off the coast of Southern California, crewmembers reported a fuel-like smell and taste in the ship’s drinking water. The engineering department shut down access to the ship's potable water and began testing the tank, and the ship headed back into San Diego. Once alongside the pier, the ship was connected up to the city water main so that the crew would have access to clean fresh water. 

Eleven crewmembers developed symptoms that could have resulted from drinking JP-5 in water, including headaches, rashes and diarrhea. All were treated and were cleared to return to duty by October 5. 

On inspection at Air Station North Island, four of the ship's 26 tanks were found to have levels of JP-5 above the Navy's health action level, and these tanks were isolated until they could be cleaned. 

After two weeks of flushing her potable water system, Nimitz put back out to sea. After exercises, she sailed to Bremerton, Washington, arriving on October 28. On arrival the four isolated tanks were cleaned, repaired and returned to service. 

The investigation determined that the contamination had occurred years earlier, during Nimitz's last deployment, and the fuel had been sitting in the water tanks ever since. Bilge water containing JP-5 leaked into an unused water tank through a deteriorated gasket on the tank top at some point in 2020-2021, while Nimitz was operating in the Pacific and the Mideast, according to the Navy. 

The carrier USS Abraham Lincoln had a related problem at about the same time and place. On September 21, 2022, just after getting under way from San Diego, Lincoln's engineering team found that the water from one tank tasted abnormal. They took the tank offline and tested it for chlorine levels; finding that chlorination levels were normal, they put it back in service. 

Six hours later, engineering crewmembers reported an off taste and color in the ship's drinking water. The engineering officer of the watch ordered all tanks in use to be valved off and tested. 

The next day, after more testing, the crew found that three tanks were contaminated with E. Coli and coliform bacteria. The tanks were isolated from the rest of the drinking water system, and the crew was provided with bottled water. 

After the incident, investigators determined that bacteria-laden bilge water got into a potable water tank through a hole in a corroded vent pipe. The pipe was repaired and all of the affected tanks were cleaned and inspected after Lincoln returned to port. No crewmember illnesses were reported in connection with the contamination.