46 CFR §45.123

1. (a)For the purposes of freeing port area only, bulwark height is considered standard at 24 in for ships 240 ft in length and less; and 48 in for ships 480 ft in length or greater. The standard bulwark height for ships of intermediate length is obtained by direct interpolation.
2. (b)If the bulwark is more than standard height, the area required by § 45.117 must be increased by 0.04 square feet per foot (ft 2/ft) of length of well for each foot difference in height.
3. (c)For ships greater than 480 ft in length that have an average bulwark height less than 3 ft, the area required by § 45.117 may be decreased by 0.04 ft 2/ft of length for each foot difference in height.