Section 157.10a - Segregated ballast tanks, crude oil washing systems, and dedicated clean ballast tanks for certain new and existing vessels of 40,000 DWT or more(a) An existing vessel of 40,000 DWT or more that carries crude oil and a new vessel of 40,000 DWT or more but less than 70,000 DWT that carries crude oil must have: (1) Segregated ballast tanks with a total capacity to meet the draft and trim requirements in paragraph (d) of this section; or(2) A crude oil washing system that meets the design, equipment, and installation requirements of subpart D of this part.(c) An existing vessel of 40,000 DWT or more that carries products and a new vessel of 40,000 DWT or more but less than 70,000 DWT that carries products must have: (1) Segregated ballast tanks with a total capacity to meet the draft and trim requirements in paragraph (d) of this section; or(2) Dedicated clean ballast tanks that have a total capacity to meet the draft and trim requirements in paragraph (d) of this section and that meet the design and equipment requirements under subpart E of this part.(d) In any ballast condition during any part of a voyage, including that of lightweight with either segregated ballast in segregated ballast tanks or clean ballast in dedicated clean ballast tanks, each tank vessel under paragraph (a)(1), or (c) of this section must have the capability of meeting each of the following without recourse to the use of cargo tanks for water ballast:(1) The molded draft amidship (dm) in meters, without taking into account vessel deformation, must not be less than dm in the following mathematical relationship: dm = 2.0 + 0.02L
(2) The drafts at the forward and after perpendiculars must correspond to those determined by the draft amidship under paragraph (d)(1) of this section, in association with a trim by the stern of no more than 0.015L.(3) The minimum draft at the after perpendicular is that which is necessary to obtain full immersion of the propeller.(e) Each tank vessel that meets paragraph (a)(1), or (c) of this section may be designed to carry ballast water in cargo tanks as allowed under § 157.35 .CGD 77-058b, 45 FR 43707, June 30, 1980, as amended by CGD 82-28, 50 FR 11626, Mar. 22, 1985; USCG-1998-3799, 63 FR 35531, June 30, 1998 Segregated ballast tanks located in wing tanks provide protection against oil outflow in the event of a collision, ramming, or grounding.