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 Coast Guard approved doors without coamings on the Flying Cloud and Lightning, catamarans operated by the Harbor Express in Boston on “partially protected” waters, without any special approval. The most important reason is the separate construction of the passenger cabin deck and of the watertight decks forming the upper bounds of the catamaran hulls, which allow no opportunity for downflooding, even if water does enter the passenger cabin. In addition, the doors are always closed during operations, and there is a specially designed drainage system both forward and aft of the doors.
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.
- Fairweather and Chenega, catamaran car and passenger ferries under construction for the Alaska Marine Highway, have weathertight doors without coamings which did not require Coast Guard approval of equivalency or special consideration. The main deck for Fairweather and Chenega is the vehicle deck, and the passenger accommodation decks are considerably higher, with negligible risk of ingress through the weather doors in question. The ingress hazard is therefore abated due to the doors’ locations.
- Many K and T boats are approved for operation with coaming-less doors located on the main deck. The cases examined include several bow-loading ferries with doors in the forward end of the deckhouse, designed to move large numbers of passengers on and off quickly. These boats were found to operate in protected waters, where coamings are not required due to the low likelihood of boarding waves and the near proximity of safe harbors or anchorages.
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:
- Coast Guard participation – The cooperation and formal participation of the Coast Guard is crucial and may require a formal request from either the Board or the Office of the Secretary of Transportation. The Coast Guard should review the philosophical approach to the work in general and the technical approach to specific design solutions. The ultimate result would be their imprimatur on the technical guidance published by the Board, without which the acceptance and success of the document would be doubtful.
- Reconfiguration solution – The work will include an outline of guidance as to where and under what operational conditions doors without coamings are acceptable without special approval, as in the cases described in Chapter 3. The project team will investigate modified arrangements of two passenger vessel types (to be approved by the Access Board), showing an adjusted layout which eliminates the coaming requirement for at least one door and provides the desired access to passenger accommodation areas.
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.
- Doorway design – Candidate alternate design work should include:
- Further development of the concepts proposed by the PVA Advisory Committee in their 2000 report.
- Investigation of removable or hinged coamings and protocols for their use.
- Investigation of doors without coamings requiring special approval and the development of associated water control and drainage arrangements suitable for common vessel types.
- Identification of operational practices required for implementation in concert with the alternate designs, for example, the requirement that the door only be operated at certain times.
- Other arrangements, such as double deck construction, that address the hazards and risks in different ways and allow for redesign for accessible doors.
- Assistance from the Coast Guard as may be necessary to identify candidate passenger vessels for the doorway design and analysis. Most observed during the Phase 1 work do not have the weather deck doorway coamings for a variety of reasons, some alluded to above. Volpe Center will work with local Marine Safety Offices (e.g., Boston and Providence) to find such vessels nearby, in order to minimize travel costs. We suggest that monohull K boat and a catamaran (either T or K boat) should be the two types examined for Phase 2.
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.