{"data":{"id":"us/46-cfr-178.450","jurisdiction":"us","citation":"46 CFR 178.450","heading":"Calculation of drainage area for cockpit and well deck vessels.","body":"(a) The drainage area required on a vessel must be computed using the following formula:\nFor protected waters required drainage = .1 × Basic Drainage\nFor partially protected waters required drainage = .5 × Basic Drainage\nFor exposed waters required drainage = Basic Drainage\nwhere:\nBasic Drainage area in centimeters 2 = 4389.12 × [(Recess Volume × Recess Ratio) + (Weather Deck Volume × Weather Deck Ratio)]; or\nBasic Drainage area in inch 2 = (Recess Volume × Recess Ratio) + (Weather Deck Volume × Weather Deck Ratio)\nRecess Volume = (BR × DR) − VR\nBR = average height in centimeters (feet) of the bulwark above the well deck or cockpit deck;\nDR = total deck area of the cockpit or well deck in the after 2/3 of the vessel length (LOD) measured in centimeters 2 (feet 2).\nVR = volume of any weather tight structure below the bulwark of the well deck or cockpit deck.\nRecess Ratio = LR / LC\nLR = the length of the recess in the after 2/3 vessel length (LOD).\nLC= 2/3 vessel length (LOD).\nWeather Deck Volume = (BD × DD) − VS\nBD = average height in centimeters (feet) of the bulwark above the weather deck;\nDD = total deck area of the weather deck adjacent to bulwarks but not in way of the cockpit or well deck in the after 2/3 of the vessel length (LOD) measured in centimenters 2 (feet 2).\nVS = volume of any weather tight superstructure below the bulwark on the weather deck located within DD.\nWeather Deck Ratio = LD / LC\nLD = the length of the weather deck bulwark in the after 2/3 of the vessel length (LOD).\nLC= 2/3 vessel length (LOD).\n(b) Vessels with bulwarks in the forward part of the vessel shall not form a well with the deckhouse which retains water.","path":["Title 46—Shipping","CHAPTER I—COAST GUARD, DEPARTMENT OF HOMELAND SECURITY","SUBCHAPTER T—SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS)","PART 178—INTACT STABILITY AND SEAWORTHINESS","Subpart D—Drainage of Weather Decks"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-46.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:22Z","sha256":"dee57ec456c51a0e828099aa7d0beb3f03023049da377f350b90feea1397f463","source_id":"us-cfr","stale":true,"prev":"us/46-cfr-178.440","next":"us/46-cfr-178.510"},"notice":"GroundRules: Original legal text. Not legal advice."}