4.1 Regulations Review and Case Studies
The intent of the Coast Guard’s watertight integrity regulations is to protect against water ingress into passenger accommodation spaces and downflooding into spaces below. The ultimate hazard that the regulations aim to prevent is capsizing, an event whose potential, and unacceptable, consequence is the deaths of many people. The regulations therefore aim to minimize the probability of capsize to the greatest extent possible.

The regulations with regard to watertight integrity for Subchapter K and T passenger vessels include provisions for coamings at weathertight doors and are an important element of the vessel stability regulations found in Subchapters K and T and in Subchapter S “Stability”. The two specified coaming heights of 6” and 3” correspond to exposed or partially protected waters and protected waters, respectively, as specified in each boat’s Coast Guard Stability Letter.

The new Subchapters K and T post-date Subchapter S, which regulates all vessels under 100 gross tons, and do not specifically supersede Subchapter S’s weathertight door coaming regulation. The K and T coaming regulation is prescriptive where S allows for interpretations based upon onboard door location and the associated downflooding potential. The terms of reference in these three subchapters differ and can be confusing. The interpretation of Subchapter S can in some cases result more stringent requirements for passenger boats operating on protected waters, while T and K prescription may in some cases be more stringent for boats on exposed and partially protected routes.

It is evident that different designers make different choices in the application of these coaming regulations. It is the author’s opinion, however, that Subchapter T and K regulations are most commonly applied in the current fleet. For the “flush deck” vessels with doors on the “main deck” which make up most of the affected passenger fleet, those regulations allow for coaming-less weathertight doors in protected waters and require coamings in “partially protected” or “exposed” waters.

That state of affairs required re-examination of the premise of the scope of work, that Volpe Center conduct case studies of “exemptions” from the coaming regulation, in light of the intent and application of Coast Guard regulations and procedures. The Coast Guard does not exempt vessels from safety regulations, but will consider and may approve alternate designs or arrangements as providing equivalent safety to the regulation in question, under the “equivalents” or “special considerations” provisions found in both Subchapters K and T.

The correspondence with the Coast Guard by the Access Board and the Volpe Center id not reveal cases of specifically approved “equivalent” designs or “special considerations” in the matter of the coaming regulations for K and T boats. The results of the cases examined are nonetheless instructive, and are summarized below:

The bow doors used for embarkation and disembarkation meet ADAAG specifications for width and threshold, but not for door hardware or level floor surface. They were, however, observed to be very effective for passengers in wheelchairs. The aft port and starboard sliding doors comply with the width and hardware specifications, but not the threshold and maneuvering space requirements.

4.2 Recommendations for Phase 2
The apparent dearth of currently approved alternate designs for coamings does not imply that Phase 2 of this project should not go forward and indeed suggests that the need to develop such designs is more urgent. The task will, however, be more difficult without the guidance of successful examples. The following elements for execution of Phase 2 are suggested:

Reconfiguration may entail more than the simple rearrangement of weathertight doors. Other considerations may include provision of alternate doorways and other modifications addressing downflooding potential.

The Board should also consider an initial investigation of the need for water flow and control modeling, comparing the performance of compliant doors with coamings to alternate door designs. Doors without coamings or ramps could be acceptable if shown to provide equal protection by use of computer or scale modeling simulations. The consideration of such simulation work is beyond the scope of this project, but development of its technical framework could be undertaken in cooperation with Coast Guard safety experts.