Review and Update of U.S. Coast Guard Vessel Stability Regulations and Guidance (2019)

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The report from the first phase of the study provided a preliminary assess- ment of each part and subpart of Subchapter S to identify candidate up- dates or changes for the U.S. Coast Guard (USCG) to consider. In this second phase of the study, the USCG asked the study committee to suggest a method for the USCG to use in prioritizing these updates and changes, which were presented in Table 3 of the first phase of the study. The method suggested in this chapter focuses on the risk reduction impact of the change; that is, it provides a means of ranking changes according to which ones promise the greatest potential to improve safety through stability assurance improvements. This chapter proposes a numerical ranking process and then applies this process for illustrative purposes to the Subchapter S updates and changes suggested in the Phase 1 report. This exercise is followed by a more thorough review of those updates and changes that the proposed methodol- ogy indicates are strong candidates for early action. RISK-INFORMED RANKING METHODOLOGY The committee believes that any effort to prioritize the suggested updates and changes in Subchapter S be informed by an understanding of the potential to reduce risk, taking into account the potential for the update and change to be implemented in a timely manner. Although there is no single way to construct such a prioritization methodology, a straight- forward approach would consist of the following basic steps: 7 Methodology for Prioritizing Subchapter S Updates and Changes 87

88 USCG VESSEL STABILITY REGULATIONS AND GUIDANCE 1. Identify significant stability-related hazards and rank them by like- lihood and severity (risk). 2. Take into account the number of vessels exposed to the risk. 3. Consider the ease of change or implementation of a regulatory update or change intended to reduce an identified hazard risk. 4. Consider changes in regulations that would improve their usability, but that do not necessarily have a clear benefit in terms of hazard risk reduction. Hazard Identification and Risk Ranking Examples of stability-related hazards are damage to the hull, improper load- ing, flooding caused by loss of watertight or weathertight integrity, severe seas and storms, and unaccounted lightship weight or cargo weight changes. An assessment of the risk of the hazard requires that consideration be given to both its likelihood and severity. Some hazards occur more frequently than others for a variety of reasons such as human error, weather, and operating conditions. When they do occur, their severity, or adverse consequences, can vary to include injuries and fatalities to crew members and passengers, envi- ronmental harm, damage to the ship and port facilities, and commercial losses. Casualty statistics can be a guide to ranking hazards according to their risk. Table 7-1 provides a common matrix that can be used to rate hazards according to risk. The likelihood of the hazard is characterized as low, medium, and high. “Low” likelihood hazards could be those that have rarely, if ever, occurred in the casualty data, while “high” likelihood hazards are those that are experienced on a regular basis. A “medium” likelihood hazard would consist of those that occur periodically. Likewise, the severity, or consequence, of the hazard can be characterized as low, medium, and high. “Low” consequence hazards would include those incidents that are not reportable to the USCG because they do not involve injury requiring first aid or they incur damage of less than $10,000. “Medium” consequence hazards would include those that require reporting to the USCG because they involve a minor injury that nevertheless requires professional treat- ment beyond first aid, damage greater than $10,000 but less than $200,000, and notification to the National Response Center. “High” consequence hazards would include those that involve a death or a major injury, large- scale property damage greater than $200,000, or other special outcomes such as an oil spill requiring third-party clean up. Hazardous events that fall into the high-risk, high-likelihood cell (upper left hand) of the matrix in Table 7-1 are obviously those that would give the USCG the greatest concern. Conversely, hazards that fall into the lowest cell in the right-hand column would be of least concern. For the purpose of ranking hazards by risk, the USCG might therefore assign risk-based scores

PRIORITIZING SUBCHAPTER S UPDATES AND CHANGES 89 to individual hazards. For illustration purposes, Table 7-1 assigns numeri- cal scores of 3, 2, and 1 for high, medium, and low ratings, respectively. To arrive at an overall risk rating—that is, one that accounts for both the hazard’s likelihood and its severity—these scores could be multiplied, such that a high-likelihood, high-consequence hazard would have the highest rating of 9, while a low-likelihood, low-consequence event would have the lowest rating of 1. Exposed Vessel Population Because these hazards may be more applicable to some vessels than others, it would be important for the USCG to consider the population of exposed vessels (or number of vessels). Here too, the USCG could assign numerical scores to hazards depending on the overall population of applicable ves- sels. Again, for illustrative purposes, one might assign a score of “2” for hazards that apply to less than 10% of the fleet, a score of “4” for hazards that apply to 10% to 60% of the fleet, and a score of “7” for hazards that apply to more than 60% of the fleet. Ease of Implementing a Regulatory Change to Address a Hazard While a method for prioritizing changes to Subchapter S could take into account the previously described risk and exposure considerations that are related to the hazard that the potential regulatory or policy document change is intended to address, the process could also account for the ease of making the change. Changes that are easy to implement might deserve early attention because they can be made relatively easily and quickly. Examples TABLE 7-1 Hazard Risk Ranking Matrix LIKELIHOOD High (3) Medium (2) Low (1) C O N SE Q U E N C E S High (3) High (9) High (6) Medium (3) Medium (2) High (6) Medium (4) Low (2) Low (1) Medium (3) Low (2) Low (1) NOTES: The matrix shows the risk numerical scoring system for the three classes of risk as High (6 ≤ score ≤ 9), Medium (3 ≤ score ≤ 5), and Low (1 ≤ score ≤ 2). Using the rounded mean values of these risk scores as the basis for assigning scores to the three “non-risk” rank- ing factors, we have Low = 2, Medium = 4, High = 7, which can be considered equivalent to the risk scoring system.

90 USCG VESSEL STABILITY REGULATIONS AND GUIDANCE are changes that can be implemented by policy document or letter, as op- posed to changes to federal regulations that require public notice and com- ment as part of the rulemaking process. Ease of change or implementation could likewise be ranked on a numerical scale—for instance, a “2” might be assigned to a change that requires a complex rulemaking project, a “4” might be assigned to a change that would require a headquarters policy document (e.g., a Navigation and Vessel Inspection Circular), and a “7” might be assigned to a change that could be implemented relatively easily by issuing a Marine Safety Center Technical Note or Plan Review Guidelines. Change for the Purpose of Increasing Usability Although risk reduction is a primary impetus for making changes to Sub- chapter S, the USCG may also want to prioritize changes that can serve other purposes, such as to increase the usability of the regulations. Improve- ments in the clarity and consistency of regulations (e.g., harmony with other parts of the Code of Federal Regulations [CFR] and with international regu- lations) are examples of changes that can increase usability. Accordingly, one could assign a value of “2” for a change that would fix minor errors, such as typos, missing links, or editorial issues; a “4” could be assigned to changes that would bring the USCG regulation into conformity with mildly conflicting international standards; and a “7” could be assigned to a change that would correct a major conflict with an international requirement. APPLICATION OF THE PRIORITIZATION METHODOLOGY By applying the proposed (and illustrative) prioritization methodology, one can compute numerical “scores” as the basis for prioritizing the Sub- chapter S changes identified in the first phase of study. The scores may be weighted differentially depending on interest—for instance, to ensure that risk reduction is given sufficient attention and more weight than usability- related changes. The end score for each change may be used as the basis for establishing priorities. To illustrate, the committee selected the following weighting factors (see Table 7-2) to be applied. TABLE 7-2 Risk Weighting Factor Element Percentage of Weighting Risk (likelihood × consequence) 60% Number of vessels 20% Ease of change or implementation 10% Clarity and harmony or usability 10%

PRIORITIZING SUBCHAPTER S UPDATES AND CHANGES 91 Table 7-3 applies these weights to regulatory changes that affect risk and usability and that consider ease of implementation. The total score of each candidate change is obtained by adding the numerical score for each element with the weighting factor applied. The total score provides the ranking for each candidate change. Review of Top Ranked Change Options While it is presented as illustrative and not definitive, the prioritization methodology identifies some potential “higher priority” changes (marked in yellow in Table 7-3). The following assessment articulates the basis for the change (e.g., documented casualty or near miss shortcoming, hazard not being controlled) and why the change ranked so highly. Part 173, Subpart E–Towing Capsizing of tugboats and towboats (including escort tugboats) is a signifi- cant stability risk and can occur when the towline reaches a large angle rela- tive to the centerline of the towboat. If the boat is unable to maneuver out of this position and the quick release cannot be activated in time, tripping (also girding, girthing, or girting) can occur due to the athwartship force of the towing line creating a heeling moment that causes the boat to lean over at a large angle, causing flooding in openings and ultimately capsizing. The risk of tripping also increases when the towing point on the towboat is near amidships. Contributing causes of a towboat capsizing in a tripping situa- tion can include small freeboard, poor stability curve of righting arms, and weathertight and watertight openings not secured correctly. When tripping accidents occur, the towboat can capsize so rapidly that crew members are not able to escape or make use of life-saving equipment. It is considered one of the most hazardous situations a tug may encounter, and the risk of tripping is often present during towing operations.1 According to April 2019 Marine Information for Safety and Law Enforce ment data, 493 inspected towboats are currently in the U.S. flag fleet, of which 97 were built between 2000–2009, and 168 between 2010–2019 (see Appendix B, Table B-10). Safety statistics for towing ves- sels report 3,244 medium and high severity incidents by the initial event for the period 2001–2017.2 The incidents include events due to loss of 1 The Shipowners’ Club. Loss Prevention: Tugs and Tows—A Practical Safety and Opera tional Guide. August 2015. See https://www.shipownersclub.com/lossprevention/ tug-and-tow-safety-and-operational-guide. 2 U.S. Coast Guard. U.S. Coast Guard–American Waterways Operators, Annual Safety Report. July 31, 2018. See https://safety4sea.com/uscg-towing-vessel-safety-statistics-for-2017.

92 USCG VESSEL STABILITY REGULATIONS AND GUIDANCE TABLE 7-3 Risk Ranking Prioritization Matrix for Subchapter S Candidate Changes Cite Topic Comment Candidate Change C on se qu en ce s (C ) L ik el ih oo d (L ) R is k (R ) N um be r of V es se ls (N um be r) E as e of C ha ng e (E ) C la ri ty a nd H ar m on y (C & H ) T ot al P ri or it y R an ki ng (R an ki ng ) 60% Risk Weighting of Each Factor 20% 10% 10% 100% Part 173, Subpart E Towing The requirements in this Subpart have been superseded by new requirements in the IS Code, Part B, Section 2.8, the update of which the USCG was actively involved. For tugs in rigorous service, such as escort tugs and ones with Voith Schneider propulsors, the existing CFR could be inadequate. However, for the large domestic towing industry with conventional tugs, the existing requirements seem adequate. For new tugs in rigorous towing service, such as escort tugs, the requirements of the new IS Code, Part B, Section 2.8, could be more appropriate. For conventional tugboats and towboats, review of the existing CFR requirements is suggested to see if the IS Code could supplement. 3 2 6 4 2 7 5.30 Part 170, Subpart F– Determination of Lightship Displacement and Centers of Gravity Lightship Weight of Passenger Vessels Passenger ship lightship weight periodic verification. Add to this Part that non- SOLAS passenger ships and boats be subject to periodic lightship weight verification process at regular intervals, which is an existing requirement for passenger ships with SOLAS Certificates. 3 2 6 4 2 7 5.30 Part 170, Subpart H Watertight Bulkhead Doors Contains some archaic requirements, such as for coal bunker doors, and refers only to an ASTM International standard for watertight doors. Watertight doors are available on a worldwide basis built to international and Class standards. There is also no requirement to keep watertight doors closed (USCG has advised on this issue). Align this section better with SOLAS requirements for better harmonization. Add requirement for keeping watertight doors closed. SOLAS provides good guidance on this. 2 2 4 7 4 4 4.60

PRIORITIZING SUBCHAPTER S UPDATES AND CHANGES 93 TABLE 7-3 Risk Ranking Prioritization Matrix for Subchapter S Candidate Changes Cite Topic Comment Candidate Change C on se qu en ce s (C ) L ik el ih oo d (L ) R is k (R ) N um be r of V es se ls (N um be r) E as e of C ha ng e (E ) C la ri ty a nd H ar m on y (C & H ) T ot al P ri or it y R an ki ng (R an ki ng ) 60% Risk Weighting of Each Factor 20% 10% 10% 100% Part 173, Subpart E Towing The requirements in this Subpart have been superseded by new requirements in the IS Code, Part B, Section 2.8, the update of which the USCG was actively involved. For tugs in rigorous service, such as escort tugs and ones with Voith Schneider propulsors, the existing CFR could be inadequate. However, for the large domestic towing industry with conventional tugs, the existing requirements seem adequate. For new tugs in rigorous towing service, such as escort tugs, the requirements of the new IS Code, Part B, Section 2.8, could be more appropriate. For conventional tugboats and towboats, review of the existing CFR requirements is suggested to see if the IS Code could supplement. 3 2 6 4 2 7 5.30 Part 170, Subpart F– Determination of Lightship Displacement and Centers of Gravity Lightship Weight of Passenger Vessels Passenger ship lightship weight periodic verification. Add to this Part that non- SOLAS passenger ships and boats be subject to periodic lightship weight verification process at regular intervals, which is an existing requirement for passenger ships with SOLAS Certificates. 3 2 6 4 2 7 5.30 Part 170, Subpart H Watertight Bulkhead Doors Contains some archaic requirements, such as for coal bunker doors, and refers only to an ASTM International standard for watertight doors. Watertight doors are available on a worldwide basis built to international and Class standards. There is also no requirement to keep watertight doors closed (USCG has advised on this issue). Align this section better with SOLAS requirements for better harmonization. Add requirement for keeping watertight doors closed. SOLAS provides good guidance on this. 2 2 4 7 4 4 4.60 continued

94 USCG VESSEL STABILITY REGULATIONS AND GUIDANCE Cite Topic Comment Candidate Change C L R Number E C&H Ranking Part 174, Subpart E– Special Rules Pertaining to Specific Vessel Types Tugboats and Towboats Although this Subpart E appears to overlap with Part 173, Subpart E–Towing (see previous information in table), it is necessarily separate because it applies to boats built as tugboats and towboats, and not just vessels that may carry out towing. Tugboats and towboats have distinct shapes and low freeboard, so these stability regulations may seem appropriate. Update these requirements based on IS Code, Part A, where appropriate, to improve harmonization with latest standards. 2 2 4 4 4 4 4.00 Part 170, Subpart E–Intact Stability Criteria, Section 170.170 Weather Criteria Requirement for each vessel to have initial GM based on a wind heel moment. Very traditional method of stability assessment that does not work with vessels with nontraditional shape and freeboard and does not consider positive stability range of the vessel as it heels. For existing vessels where this is the sole criteria, consider requiring them to update stability documentation to include other criteria that would be applied to that vessel type. 3 1 3 2 4 7 3.30 Part 170, Subpart E–Intact Stability Criteria, Section 170.173 Vessels with Unusual Proportion and Form Range of stability righting lever arm requirement that is very similar to IS Code Section 2.2 Criteria Regarding Righting Lever Curve Properties. Also contains reduced requirements in Part (e) for vessels in partially and protected routes. Limitations included on which ships it applies to, such as less than 100 m. Remove the restriction on length less than 100 m, as this restriction is not applied in the IS Code and there is no technical basis for it. Expand application to all self-propelled vessels, except for special types and small boats to which IS Code would not apply. 2 1 2 4 2 7 2.90 Part 170, Subpart F– Determination of Lightship Displacement Determination of Lightship Weight and Centers of Gravity Lists requirements for methods of determination of lightship weight and centers. Duplicates much of what is in the IS Code, Part B, Annex 1: “Detailed Guidance for the Conduct of an Inclining Test.” Replace much of Subpart F, where appropriate, with IS Code, Part B, Annex 1, to harmonize U.S. regulations with those of other nations and incorporate latest standards. 1 1 1 7 4 4 2.80 Part 174, Subpart B– Special Rules Pertaining to Specific Vessel Types Deck Cargo Barges Deck cargo barges are a traditional form of waterborne transport in the U.S. Depending on the service (inland, Great Lakes, oceans, bays, and sounds) there are different requirements for this Subpart. The IS Code for barges (defined as pontoons by the IMO) applies to ocean-going barges and was recently updated with USCG and industry input. Review and update Subpart B for consistency of terminology and consider the latest requirements contained in the IS Code, Part B, Section 2.2. 1 1 1 7 4 4 2.80 TABLE 7-3 Continued

PRIORITIZING SUBCHAPTER S UPDATES AND CHANGES 95 Cite Topic Comment Candidate Change C L R Number E C&H Ranking Part 174, Subpart E– Special Rules Pertaining to Specific Vessel Types Tugboats and Towboats Although this Subpart E appears to overlap with Part 173, Subpart E–Towing (see previous information in table), it is necessarily separate because it applies to boats built as tugboats and towboats, and not just vessels that may carry out towing. Tugboats and towboats have distinct shapes and low freeboard, so these stability regulations may seem appropriate. Update these requirements based on IS Code, Part A, where appropriate, to improve harmonization with latest standards. 2 2 4 4 4 4 4.00 Part 170, Subpart E–Intact Stability Criteria, Section 170.170 Weather Criteria Requirement for each vessel to have initial GM based on a wind heel moment. Very traditional method of stability assessment that does not work with vessels with nontraditional shape and freeboard and does not consider positive stability range of the vessel as it heels. For existing vessels where this is the sole criteria, consider requiring them to update stability documentation to include other criteria that would be applied to that vessel type. 3 1 3 2 4 7 3.30 Part 170, Subpart E–Intact Stability Criteria, Section 170.173 Vessels with Unusual Proportion and Form Range of stability righting lever arm requirement that is very similar to IS Code Section 2.2 Criteria Regarding Righting Lever Curve Properties. Also contains reduced requirements in Part (e) for vessels in partially and protected routes. Limitations included on which ships it applies to, such as less than 100 m. Remove the restriction on length less than 100 m, as this restriction is not applied in the IS Code and there is no technical basis for it. Expand application to all self-propelled vessels, except for special types and small boats to which IS Code would not apply. 2 1 2 4 2 7 2.90 Part 170, Subpart F– Determination of Lightship Displacement Determination of Lightship Weight and Centers of Gravity Lists requirements for methods of determination of lightship weight and centers. Duplicates much of what is in the IS Code, Part B, Annex 1: “Detailed Guidance for the Conduct of an Inclining Test.” Replace much of Subpart F, where appropriate, with IS Code, Part B, Annex 1, to harmonize U.S. regulations with those of other nations and incorporate latest standards. 1 1 1 7 4 4 2.80 Part 174, Subpart B– Special Rules Pertaining to Specific Vessel Types Deck Cargo Barges Deck cargo barges are a traditional form of waterborne transport in the U.S. Depending on the service (inland, Great Lakes, oceans, bays, and sounds) there are different requirements for this Subpart. The IS Code for barges (defined as pontoons by the IMO) applies to ocean-going barges and was recently updated with USCG and industry input. Review and update Subpart B for consistency of terminology and consider the latest requirements contained in the IS Code, Part B, Section 2.2. 1 1 1 7 4 4 2.80 continued

96 USCG VESSEL STABILITY REGULATIONS AND GUIDANCE Cite Topic Comment Candidate Change C L R Number E C&H Ranking Part 172, Subpart B– Special Rules Pertaining to Bulk Cargoes Grain In 170.030(b)(5), the definitions of GMR and GMI are difficult to understand and what the required values are is not clear. In addition, the formulas in (i) and (ii) are missing the division sign “/”. Clarify the definitions and “required values” of GMR and GMI and correct the formulas by adding the missing “/”. 2 1 2 2 7 4 2.70 Part 170, Subpart H Watertight Bulkhead Doors Contains some archaic requirements, such as for coal bunker doors, and refers only to an ASTM standard for watertight doors. Watertight doors are available on a worldwide basis built to international and Class standards. There is also no requirement to keep watertight doors closed (USCG has advised on this issue). Expand list of permitted watertight doors to include those constructed to recognized international and Class standards. 1 1 1 4 7 4 2.50 Part 170, Subpart F– Determination of Lightship Displacement and Centers of Gravity, Section, 170.200 Estimated Lightship Weight, Vertical Center of Gravity For some types of vessels, such as barges, placing a pendulum during the incline test is difficult to do in a manner that is not subject to interference from wind. Current USCG and IMO guidance is to use at least one pendulum. As electronic inclinometers have become more reliable and accurate, it may be acceptable to eliminate the need for one pendulum and to use only inclinometers where vessel arrangement makes pendulum use difficult. Consider allowing use of only inclinometers where installation of a pendulum out of the weather is not practical considering the vessel’s arrangement. This could be limited to vessels that are not generally stability limited and could be issued as a policy letter. 1 1 1 4 7 2 2.30 Part 170, Subpart F– Determination of Lightship Displacement and Centers of Gravity, Section, 170.200 Estimated Lightship Weight, Center of Gravity For tank vessels that use estimated VCG, when changes to outfitting are made that exceed 2% of lightship weight, stability documentation has to be updated. However, because basic dimensions of the vessel are not changed, VCG remains the same, and if max displacement is not changed, stability at max draft remains the same, so it appears the results of the stability calculation remain the same. For tank vessels with estimated VCG and no change in max displacement, allow a higher threshold for changes in lightship weight that trigger need for updated stability documentation. A joint industry committee could study this issue to develop a recommendation, which could be issued as a policy letter. 1 1 1 4 4 4 2.20 NOTES: “Higher priority” changes highlighted in yellow. ASTM = American Society for Testing and Materials, now ASTM International; CFR = Code of Federal Regulations; GM = metacentric height; GMI = metacentric height, increment; GMR = metacentric height, re- quired; IMO = International Maritime Organization; IS Code = Intact Stability Code, IMO; SOLAS = International Convention for the Safety of Life at Sea; USCG = U.S. Coast Guard; VGC = vertical center of gravity. TABLE 7-3 Continued

PRIORITIZING SUBCHAPTER S UPDATES AND CHANGES 97 Cite Topic Comment Candidate Change C L R Number E C&H Ranking Part 172, Subpart B– Special Rules Pertaining to Bulk Cargoes Grain In 170.030(b)(5), the definitions of GMR and GMI are difficult to understand and what the required values are is not clear. In addition, the formulas in (i) and (ii) are missing the division sign “/”. Clarify the definitions and “required values” of GMR and GMI and correct the formulas by adding the missing “/”. 2 1 2 2 7 4 2.70 Part 170, Subpart H Watertight Bulkhead Doors Contains some archaic requirements, such as for coal bunker doors, and refers only to an ASTM standard for watertight doors. Watertight doors are available on a worldwide basis built to international and Class standards. There is also no requirement to keep watertight doors closed (USCG has advised on this issue). Expand list of permitted watertight doors to include those constructed to recognized international and Class standards. 1 1 1 4 7 4 2.50 Part 170, Subpart F– Determination of Lightship Displacement and Centers of Gravity, Section, 170.200 Estimated Lightship Weight, Vertical Center of Gravity For some types of vessels, such as barges, placing a pendulum during the incline test is difficult to do in a manner that is not subject to interference from wind. Current USCG and IMO guidance is to use at least one pendulum. As electronic inclinometers have become more reliable and accurate, it may be acceptable to eliminate the need for one pendulum and to use only inclinometers where vessel arrangement makes pendulum use difficult. Consider allowing use of only inclinometers where installation of a pendulum out of the weather is not practical considering the vessel’s arrangement. This could be limited to vessels that are not generally stability limited and could be issued as a policy letter. 1 1 1 4 7 2 2.30 Part 170, Subpart F– Determination of Lightship Displacement and Centers of Gravity, Section, 170.200 Estimated Lightship Weight, Center of Gravity For tank vessels that use estimated VCG, when changes to outfitting are made that exceed 2% of lightship weight, stability documentation has to be updated. However, because basic dimensions of the vessel are not changed, VCG remains the same, and if max displacement is not changed, stability at max draft remains the same, so it appears the results of the stability calculation remain the same. For tank vessels with estimated VCG and no change in max displacement, allow a higher threshold for changes in lightship weight that trigger need for updated stability documentation. A joint industry committee could study this issue to develop a recommendation, which could be issued as a policy letter. 1 1 1 4 4 4 2.20 NOTES: “Higher priority” changes highlighted in yellow. ASTM = American Society for Testing and Materials, now ASTM International; CFR = Code of Federal Regulations; GM = metacentric height; GMI = metacentric height, increment; GMR = metacentric height, re- quired; IMO = International Maritime Organization; IS Code = Intact Stability Code, IMO; SOLAS = International Convention for the Safety of Life at Sea; USCG = U.S. Coast Guard; VGC = vertical center of gravity.

98 USCG VESSEL STABILITY REGULATIONS AND GUIDANCE stability, capsizing, and flooding, but do not provide sufficient information to determine if any of these incidents were due to tripping. Internationally, Canadian statistics indicated four fatalities from three near-capsizing and eight capsizing because of tripping incidents over a 10-year period (1999– 2009).3 Likewise, the UK Marine Accident Investigation Branch accident reports have confirmed incidents where towline-tripping heeling has caused towboats to flood and capsize.4 This regulatory change ranks highest by the suggested risk ranking methodology. The stability risks of towing vessels, especially the potential to capsize due to tripping, was rated as a high risk due to medium likeli- hood and high potential consequence. As the regulation change would be applied to new tugboats and towboats, the number of potential new vessels to be built in the future was rated medium level, considering the current trend of new builds over the past 19 years. The ease of implementation of the change was rated low because it would require going through the difficult and lengthy rulemaking process. For new tugs in rigorous towing service, such as escort tugs, the requirements of the newer Amendments to the 2008 Intact Stability Code, IMO (IS Code), Part B,5 appear to provide more appropriate guidance. Part 170, Subpart F–Determination of Lightship Displacement and Centers of Gravity Under Part 170, Subpart F, each vessel is required to calculate the lightship weight and centers of gravity; however, there is no requirement for peri- odic verification of lightship weight afterward. International Convention for the Safety of Life at Sea (SOLAS) passenger ships are required to have such periodic verification, while non-SOLAS passenger vessels are not. If a periodic verification of lightship weight requirement were added for non- SOLAS passenger vessels, it could be modeled after the guidance provided in Subchapter S, Part 170, Subpart F. Incremental growth of lightship weight can occur over many years and can produce a stability risk to a passenger vessel. The USCG requires 3 See footnote 22, Canada Transportation Safety Board Marine Investigation Report, M09W0141, Tug Girding and Capsizing–Tug North Arm Venture While Towing the Barge North Arm Express Entrance to Sechelt Rapids, British Columbia, 19 July 2009. August 2010. http://www.bst-tsb.gc.ca/eng/rapports-reports/marine/2009/m09w0141/m09w0141.html. 4 UK MAIB. On the Investigation into the Loss of the Tug Ijsselstroom in the Port of Peterhead, 14 June 2009. Report No 4/2010. April 2010. https://www.gov.uk/maib-reports/ girting-and-capsize-of-tug-ijsselstroom-in-peterhead-bay-scotland. 5 See Section 2.8, Ships Engaged in Towing and Escort Operations at http://www.imo.org/en/ KnowledgeCentre/IndexofIMOResolutions/Maritime-Safety-Committee-%28MSC%29/ Documents/ MSC.415%2897%29.pdf.

PRIORITIZING SUBCHAPTER S UPDATES AND CHANGES 99 a vessel to undergo a stability review if its lightship weight changes more than 2% or the longitudinal center of gravity shifts more than 1% of the length between perpendiculars. Although potential weight creep may not exceed these values from the result of any one change, accumulated weight creep over time could be an issue, although detecting any of these small changes can be difficult. The small incremental changes in the vessel’s draft or trim could go unnoticed by the master or crew, potentially creating un- noticed reductions in a vessel’s stability. Accordingly, periodic reviews of a passenger vessel’s lightship weight can monitor whether a potential stability risk exists. While the committee is unaware of any reported stability casualties due to lightship weight growth, the U.S. passenger vessel fleet has evolved greatly in design, configuration, and markets served to create potential new risks from complacency. What has worked safely for past designs may not work for new vessel designs. Although it is unaware of any formal studies on weight creep and its potential impact on the U.S. domestic passenger vessel fleet’s stability, the committee did perform its own sensitivity analyses as described in Chapter 3 of this report. The results indicated that, for non- SOLAS passenger vessels, small changes in lightship weight could critically affect their stability. The committee rated the unmonitored growth of lightship weight as a high-risk concern because of the possibility of major damage to the vessel and possible injury to the crew or passengers. Periodic verifications of lightship weight could be made for many inspected passenger vessels. The ease of implementation is rated low, as a regulatory change would require formal rulemaking under the Administrative Procedure Act (APA) process. Clarity and harmony would be greatly enhanced by bringing the regulation into agreement with SOLAS Chapter II-1, Regulation 5.5, which mandates periodic lightship weight surveys for all passenger ships. Part 170, Subpart H, Watertight Bulkhead Doors Part 170, Subpart H, contains some outdated requirements, such as for coal bunker doors, and refers only to an ASTM International (formerly American Society for Testing and Materials) standard for watertight doors, although watertight doors built to international and class standards are available worldwide. In addition, there is no requirement to keep watertight doors closed. A requirement could be added for keeping watertight doors closed during navigation, using the good guidance on this topic provided in SOLAS.6 6 See MSC.1/Circ.1564, July 16, 2017, IMO Revised Guidance for Watertight Doors on Passenger Ships at https://www.mardep.gov.hk/en/msnote/pdf/msin1811anx2.pdf.

100 USCG VESSEL STABILITY REGULATIONS AND GUIDANCE Watertight doors prevent the ingress of water from one compartment to another during flooding or accidents. Watertight doors may be inad- vertently left open during navigation, which creates a risk to the required damage stability survivability of a ship. Structural damage can occur to a ship during a collision or grounding, which introduces a potential risk for deformed bulkheads and decks, so that watertight doors cannot close. The risk of progressive flooding following such deformation of the ship’s struc- ture may increase if watertight doors are left open or cannot be closed. With extensive structural damage creating a large opening, the water ingress rate can be high such that a ship’s compartment floods quickly. If watertight doors are open in adjacent compartments, several compartments may be- come flooded before the doors are closed, greatly increasing the risk to the damage stability survivability of a ship. In applying the risk-ranking methodology, the committee rated the open watertight door as a medium risk level scenario that might occur with minor to medium damages to the vessel and possible injury to the crew or passengers. The regulation change would be applied to most inspected vessels. The ease of implementation of the change was considered medium as the change could be affected by a USCG headquarters policy document. Implementation of the change would clarify that watertight doors closed during navigation could decrease risk and would be in harmony with inter- national regulations. Based on the foregoing assessment, this candidate change was ranked as a high priority by the methodology. Part 174, Subpart E–Special Rules Pertaining to Tugboats and Towboats Although this Subpart seems to overlap with Part 173, Subpart E– Towing, this Subpart is necessarily separate because it applies to boats built as tugboats and towboats and not just vessels that are equipped for towing. Consider updating the Subpart E stability requirements based on the 2008 IS Code, Part A, where appropriate, to improve harmonization with the latest standards. The significant stability hazards previously described for vessels while towing apply to tugboats and towboats that are equipped for towing. Tug- boats and towboats have distinctive shapes with low freeboard and poor righting arm characteristics. With low freeboard, downflooding and deck edge immersion occur at low heel angles, with a quick loss of righting arm at small angles of heel. The committee rated the stability risks of tugboats and towing vessels as medium, with the potential loss of stability to be of medium risk with medium likelihood with high consequences. The number of vessels affected by any change was considered medium level. The ease of implementation of the change was considered medium as it is undetermined what changes,

PRIORITIZING SUBCHAPTER S UPDATES AND CHANGES 101 if any, would involve the APA rulemaking process. Implementation of any change would better harmonize Part 174, Subpart E, with the 2008 IS Code, Part A. Part 170, Subpart E–Intact Stability Criteria, 170.170 Weather Criteria In its Phase 1 report, the committee suggested that Part 170.170 Weather Criteria could be retained as an available standard, as long as it is not the sole criterion, except in special cases. It could be applied to vessels in domestic service that are non-ocean-going or that do not operate in Great Lakes service away from land. Because of the shortcomings of the 170.170 weather criteria for overall stability assessment, existing vessels, for which it is the sole criteria, would not be automatically “grandfathered” during subsequent regulatory updates. Existing vessel stability documents could be updated to include the additional criteria that may apply to them to ensure that an adequate level of stability safety is achieved. As discussed in Appendix G of the Phase 1 Report,7 Part 170.170 is the traditional USCG intact stability criteria developed originally from data for traditionally shaped ocean-going ships.8 These criteria are initial metacentric height (GM) criteria that determine the GM for small angles of heel of the upright vessel and are “a poor indicator of overall stability, especially in response to large heeling forces and moments as might be experienced by a vessel in heavy weather where high winds and seas can be expected.”9 The criteria are also poor indicators of overall stability for ships with low free- board that quickly lose righting arm at small angles of heel. The weather criteria’s applicability to “each vessel” can be as viewed as being too broad. As a general standard for most domestic vessels, it can continue to be useful, particularly for vessels with large wind areas such as some small passenger vessels with large canopies. The weather criteria could be retained as an available standard, as they are currently referenced in numerous other subchapters (such as M, T, and K), as long as they are not the sole standard, except in special cases. Vessels for which they are the sole criteria could be reevaluated as to whether these would be the governing criteria if they were reevaluated for stability under the CFR with changes 7 See the Phase 1 letter report at http://www.trb.org/Main/Blurbs/178088.aspx. 8 Marine Safety Manual, Vol. 4, Chap. 6, 6.E.20.a: “In the early 1940’s the Coast Guard developed an intact GM criterion using Liberty Ship and T-2 tanker type vessels as the data base. This criterion has remained in effect and is referred to as the weather criterion (now in 46 CFR 170.170). Also, the vessels in the data base were much larger than T-boats and much smaller than car carriers.” See https://media.defense.gov/2017/Mar/29/2001723819/-1/-1/0/ CIM_16000_9.PDF. 9 Marine Safety Center. Technical Report, SS El Faro, Stability and Structures. March 22, 2017, p. 45.

102 USCG VESSEL STABILITY REGULATIONS AND GUIDANCE suggested by the committee. If not, vessels could update their stability docu- mentation to include the additional criteria that will be applied to similar vessels under the updated CFR. A comparable international regulation is the 2008 IS Code, Part A, Chap- ter 2, Section 2.3, Severe wind and rolling criterion (weather criterion).10 Some confusion with 170.170 Weather Criteria will be inevitable as these two criteria have similar names. The 2008 IS Code criterion is intended to check vessel stability against capsizing in wind and waves in the case of loss of propulsion power and the vessel drifting abeam to the seas, one of the extreme stability hazards a vessel could face. Whether the required stability from 170.170 or Section 2.3 will require a higher level of safety depends on the vessel shape (vessels with high wind profile will generally require a higher initial GM under 170.170). However, the 2008 IS Code Section 2.3 is inappropriate for most domestic vessels, which would neces- sitate retaining the 170.170 Weather Criteria for most domestic service, non-ocean-going vessels (vessels operating less than 20 nautical miles from the coast). However, an exception could be made for vessels operating on the Great Lakes, where they can be far from land and face conditions simi- lar to ocean service. A new regulation that references this paragraph in the 2008 IS Code could be added for domestic vessels that are ocean-going or in equivalent Great Lakes service away from land. The stability risk associated with this candidate change was charac- terized as low to medium, as it is expected that not many existing vessels would be affected by this change. The ease of implementation of the change was considered medium, as it is uncertain whether such a change would involve the federal APA rulemaking process. Implementation of the change would significantly harmonize the regulations with latest standards. Part 170, Subpart E–Intact Stability Criteria, 170.173—Criterion for Vessels of Unusual Proportion and Form Section 170.173 contains intact stability requirements for certain vessels under 328 ft (100 m). This restriction could be removed, as there is no reason for this restriction at this time, and it does not apply in the 2008 IS Code, Part A, Section 2.2. One possibility is to apply this requirement to all self-propelled vessels, except for special types and small boats to which the 2008 IS Code, Part A, Section 2.2 also does not generally apply. Vessels with low freeboard and larger vessels for which 170.170 weather criteria are the sole criteria are at risk of not having adequate stability over a range of heels that may occur due to wind, weather, damage, 10 See http://www.imo.org/en/KnowledgeCentre/IndexofIMOResolutions/Maritime-Safety- Committee-(MSC)/Documents/MSC.267(85).pdf.

PRIORITIZING SUBCHAPTER S UPDATES AND CHANGES 103 or operation. There does not appear to be a reason to exempt vessels larger than 100 m from this requirement because a similar requirement applies to these vessels in the 2008 IS Code. Section 170.170(d), which appears to apply Section 170.173 only to vessels that do not meet the standard ship proportions, places these vessels at greater risk by not applying currently accepted stability criteria to vessels of standard proportions. Section 170.173 is similar to the 2008 IS Code Part A, Section 2.2, criteria with regard to righting lever curve properties. The 2008 IS Code is applicable to vessels in ocean service, and so a similar requirement is applied to all U.S. vessels to which this Part applies and that also operate in exposed or ocean waters and have international certificates (see Section 170.165). Section 170.173 does contain reduced requirements in paragraph (e) for vessels in partially protected and protected routes, which appear appropriate for the broad range of vessel types and services covered by this regulation. The basis for this is discussed in more detail in the Marine Safety Manual.11 This section could also apply to all self-propelled vessels and not just to vessels of unusual proportion and form. When appropriate, the USCG does develop exceptions for special vessel types, such as tugboats, towboats, catamarans, high-speed craft, and boats under 24 m, etc. This would also require deleting Section 170.170(d), which appears to apply Sec- tion 170.173 only to vessels that do not meet the standard ship proportions. The priority ranking of this candidate change is largely driven by the improvement in clarity and harmony from the change. SUMMARY To aid the USCG’s decision making about the review and updating of can- didate regulation changes, the committee developed an illustrative meth- odology to prioritize changes based on risk impact, ease of change or implementation, and clarity and harmony. To demonstrate the application of the risk ranking methodology, the committee applied it to the candidate changes identified in the Phase 1 report. For the top six highest priority reg- ulation changes identified by the methodology, the rationale for their high ranking is explained. As previously noted, many of the suggested updates to Subchapter S would require new regulations and engaging with applicable industry advisory groups prior to initiating an APA rulemaking process. 11 Energy for Less Than Ocean Service. Marine Safety Manual. Vol. 4, Chapter 6, 6.E.20.k, p. 6-81.