(a) All owners or managing operators of more than one existing towing vessel required to have a COI by this subchapter must ensure that each existing towing vessel under their ownership or control is issued a valid COI according to the following schedule:

1. (1) By July 22, 2019, at least 25 percent of the towing vessels must have valid COIs on board;
2. (2) By July 20, 2020, at least 50 percent of the towing vessels must have valid COIs on board;
3. (3) By July 19, 2021, at least 75 percent of the towing vessels must have valid COIs on board; and
4. (4) By July 19, 2022, 100 percent of the towing vessels must have valid COIs on board.