One of the first paragraphs of the article: at the time it was considered dumping the barrels in the deep ocean was sufficient because the vast amount of water would dilute the chemical. The shortcut they took was that they did not go that far into the ocean but instead kept much closer to shore and dumped the barrels there, as well as punctured them when they floated. The discovery that's lamented is the "shortcut dumping ground". This does not fit with your jumped-to conclusions.