46 C.F.R. § 171.150
(b) Except as provided in paragraphs (c) and (d) of this section, the area required for freeing ports in the bulwarks that form a well must be determined as follows:
(2) If a vessel operates only on protected or partially protected waters and complies with the requirements in the following sections for a vessel that operates on exposed waters, it must have at least 50 percent of the freeing port area derived from table 171.150:
(d) If a vessel that operates on exposed or partially protected waters does not have free drainage from the foredeck aft, then the freeing port area must be derived from table 171.150 using the entire bulwark length rather than the bulwark length in the after two-thirds of the vessel as stated in the table.
| Height of solid bulwark in inches (centimeters) | Freeing port area 1 2 |
|---|---|
| 6(15) | 2(42.3) |
| 12(30) | 4(84.7) |
| 18(46) | 8(169.3) |
| 24(61) | 12(253.9) |
| 30(76) | 16(338.6) |
| 36(91) | 20(423.2) |
| 1 Intermediate values of freeing port area can be obtained by interpolation. | |
| 2 In square inches per foot (square centimeters per meter) of bulwark length in the after 2⁄3 of the vessel. |
[CGD 85-080, 62 FR 51354, Sept. 30, 1997]