Section 157.09 - Segregated ballast(a) A new vessel of 70,000 tons DWT or more must have segregated ballast tanks that have a total capacity to allow the vessel to meet the draft and trim requirements in paragraph (b) of this section without recourse to the use of oil tanks for water ballast.(b) In any ballast condition during any part of a voyage, including that of lightweight with only segregated ballast, the vessel's drafts and trim must have the capability of meeting each of the following requirements: (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 as specified in paragraph (b)(1) of this section, in association with the trim by the stern of no more than 0.015L.(3) The minimum allowable draft at the after perpendicular is that which is necessary to obtain full immersion of the propeller.(c) The vessel may be designed to carry ballast water in cargo tanks during the condition described in § 157.35 .(d) Segregated ballast spaces, voids, and other noncargo-carrying spaces for a vessel of conventional form must be distributed: (1) So that the mathematical average of the hypothetical collision (Oc) and the hypothetical stranding (Os) outflows as determined by the application of the procedures in § 157.19 and appendix B is 80 percent or less of the maximum allowable outflow (OA) as determined by § 157.19(b)(1) ; and(2) To protect at least 45 percent of the sum of the side and bottom shell areas, based upon projected molded dimensions, within the cargo tank length. When the vessel design configuration does not provide for the spaces to be distributed to protect at least 45 percent of the side and bottom shell areas, the spaces must be distributed so that the mathematical average of the hypothetical collision (Oc) and the hypothetical stranding (Os) outflows, determined by application of the procedures in § 157.19 and appendix B, is a further 2 percent less than the maximum allowable outflow (Oa) for each 1 percent by which the shell area protection coverage required is not achieved.(e) A ballast space, void or other non-cargo-carrying space used to meet requirements in paragraph (d) of this section must separate the cargo tank boundaries from the shell plating of the vessel by at least 2 meters.(f) A vessel of conventional form for application of this section has: (1) A block coefficient of .80 or greater,(2) A length to depth ratio between 12 and 16, and(3) A breadth to depth ratio between 1.5 and 3.5.(g) Segregated ballast spaces, voids, and other noncargo-carrying spaces for a vessel not of conventional form must be distributed in a configuration acceptable to the Coast Guard.CGD 74-32, 40 FR 48283, Oct. 14, 1975, as amended by CGD 74-32, 40 FR 49328, Oct. 22, 1975; CGD 75-201, 41 FR 1482, Jan. 8, 1976