I’m not sure but, I believe that the Load Line does not even come into play until they hit either Sea or the Sound. When I was up there it was common to see barges loaded decks to leaving ship side and heading to a dock to discharge.
Those Sewage Tankers no longer go to sea and I believe they just move it from one dock to another. Years ago, I worked on a Disposal Tanker and that company (the Dragon Lady) was known to “Push” the limits on what we carried but we went to sea to dump.