Excessive air crept inside the “two-day tank” on board, which feeds into the ferry’s fuel manifold. When combined with moisture inside the tank, a black sludge formed at the bottom. That sludge broke free, overwhelming the ship’s fuel filters, killing power to the generators and disabling the Walla Walla’s steering.
Ferry officials announced last spring that the boat’s malfunctioning was due to fuel contamination but didn’t specify the source of that contamination
Read more: https://www.seattletimes.com/seattle-news/transportation/bacteria-and-fungus-in-fuel-caused-ferry-walla-walla-to-run-aground/