Section 153.256 - Trunks, domes, and openings of cargo tanks(a) The hatch of a cargo tank must:(1) Be at the highest point of the tank; and(2) Open on or above the weatherdeck.(b) To be endorsed to carry a cargo requiring an independent cargo tank, a tank must have: (1) A trunk or dome at the uppermost part of the tank, extending above the weatherdeck;(2) Its hatch at the top of the trunk or dome; and(3) No openings below the weatherdeck.