When tanks have been washed with crude oil, and ballasted without being water rinsed, the ballast is referred to as _________.

Correct Answer: Option D — dirty ballast

Dirty ballast is defined as ballast water that has been introduced into a cargo tank previously containing oil and has not been subjected to a final water rinse. Because it contains significant oil residue from the tank walls, it must be handled according to strict MARPOL discharge regulations.