Sub-Committee on Ship Design and Construction (SDC 9), 23-27 January 2023

Addressing underwater noise from ships - draft revised guidelines and work plan agreed   

Draft revised Guidelines for the reduction of underwater noise from commercial shipping to address adverse impacts on marine life have been agreed by the IMO Sub-Committee on Ship Design and Construction (SDC 9), which met 23-27 January.

The draft guidelines recognize that commercial shipping is one of the main contributors to underwater radiated noise (URN) which has adverse effects on critical life functions for a wide range of marine life, including marine mammals, fish and invertebrate species, upon which many coastal Indigenous communities depend for their food, livelihoods and cultures. 

The draft revised guidelines provide an overview of approaches applicable to designers, shipbuilders and ship operators to reduce the underwater radiated noise of any given ship. They are intended to assist relevant stakeholders in establishing mechanisms and programmes through which noise reduction efforts can be realized.

The draft guidelines revise the previous guidelines (issued in 2014). They include updated technical knowledge, including reference to international measurement standards, recommendations and classification society rules. They also provide sample templates to assist shipowners with the development of an underwater radiated noise management plan.

The draft guidelines will now be submitted to the Marine Environment Protection Committee (MEPC 80), which meets from 3-7 July 2023, for approval.

The draft guidelines were developed by a correspondence group with further work completed by a working group which met during the Sub-Committee session.

The correspondence group was re-established, to report back to SDC 10 in January 2024, to address the remaining work under the agenda item. It was, in particular, tasked with revising a flowchart on the URN Noise Management Planning process to reflect the Revised Guidelines, and the underwater noise management plan included in appendix 3, to be used as a tool for raising awareness. The group will also finalize and prioritize the provisional list of suggested next steps to further prevent and reduce underwater radiated noise from ships.

The Sub-Committee agreed a work plan which envisages, among other things, identifying ways to implement the Revised Guidelines and increase awareness and uptake; organizing an expert workshop on potential co-benefits and trade-offs that may exist between the reduction of underwater radiated noise from ships and energy efficiency; and developing a plan of action for further work.

Underwater noise in Inuit Nunaat and the Arctic

The revised draft guidelines include reference to Inuit Nunaat, saying that, in Inuit Nunaat, a number of characteristics of the region and the activities within could increase the impacts from underwater radiated noise. This includes potential for icebreaking activities, presence of noise-sensitive species, and potential interference with indigenous hunting rights. Additional efforts to decrease impacts on marine wildlife are advisable for ships that operate in these areas, including particular attention to reducing the noise impact from icebreaking and implementation of operational approaches and monitoring.  

In addition, the working group developed separate draft guidelines for underwater radiated noise reduction in Inuit Nunaat and the Arctic, with a view to being utilized in the future by interested parties.

These draft guidelines recognize that Inuit Nunaat is a unique environment and adverse impacts to marine wildlife in this area from shipping noise may be significantly increased as a result. Sound levels throughout Inuit Nunaat are lower than elsewhere, making it more vulnerable to increases from industrial activity.

The draft text was noted by the Sub-Committee

Emergency towing arrangements - extension to ships other than tankers   

Draft SOLAS amendments to apply requirements for emergency towing equipment for tankers to other types of ships were agreed, for submission to the next session of the Maritime Safety Committee (MSC) for approval with a view to subsequent adoption.   

 The draft amendments to SOLAS Regulation II-1/3-4 – Emergency towing arrangements and procedures - would require emergency towing arrangements to be fitted on ships other than tankers of 20,000 gross tonnage and above, constructed on or after the entry into force date of the amendments. Such arrangements shall, at all times, be capable of rapid deployment in the absence of main power on the ship to be towed and easy connection to the towing ship. 

 The Sub-Committee also agreed on the need to amend the Guidelines on emergency towing arrangements for tankers (resolution MSC.35(63), as amended) to address all types of ships covered by the draft new regulation.  

Prohibiting asbestos on MODUs 

The Sub-Committee agreed draft amendments to the 1979, 1989 and 2009 Codes for the Construction and Equipment of Mobile Offshore Drilling Units (MODU Codes) to prohibit materials which contain asbestos. The draft amendments will be submitted to the MSC for adoption, with a view to entry into effect on 1 January 2024.  

 The Sub-Committee also agreed to a draft unified interpretation, to clarify that existing materials stowed on board before 1 January 2024 are not prohibited from being retained on board but should not be installed unless they can be documented to be asbestos-free before use/installation. 

 Draft new guidelines for maintenance and monitoring of materials containing asbestos on board MODUs were also agreed, for approval by the MSC.   

Safe return to port – revision of the explanatory notes 

The Sub-Committee began its work to revise the Interim explanatory notes for the assessment of passenger ship capabilities after a fire or flooding casualty (MSC.1/Circ.1369).  

 The interim guidelines were issued in 2010 to provide additional guidance for the implementation of a package of SOLAS amendments adopted in 2006 , affecting passenger ships built after 1 July 2010.  The amendments were the result of a comprehensive review of passenger ship safety initiated in 2000 with the aim of assessing whether the SOLAS regulations in force at the time were adequate, in particular for the large passenger ships being built. Increased emphasis is placed on reducing the chances of accidents occurring and on improved survivability, embracing the concept of the ship "as its own best lifeboat" and a philosophy of "safe return to port". 

 The review of the interim guidelines will take into account more than a decade of advancement in technology and design. A correspondence group was established to progress the work intersessionally.  

Safe novel and innovative designs for ships – development of guidelines 

The Sub-Committee continued its work on developing safety objectives and functional requirements of the Guidelines on alternative design and arrangements for SOLAS chapter II-1 - Construction - Subdivision and stability, machinery and electrical installations - as an important step to ensure safe novel and innovative designs for ships. 

 SOLAS requirements already allow the approval of alternative designs and arrangements, provided that they meet the intent of the requirements concerned and provide an equivalent level of safety. To support the development of new designs and alternative technology, the MSC has been developing goals and functional requirements. 

The Sub-Committee agreed, in principle, to the goals for SOLAS chapter II-1, parts C (Machinery installations) and E (Additional requirements for periodically unattended machinery spaces). Also agreed, in principle, were the outcome of failure modes/hazards identification for SOLAS chapter II-1, parts C and E. 

ESP Code – amendments agreed    

The Sub-Committee agreed to draft amendments to the International Code on the Enhanced Programme of Inspections during Surveys of Bulk Carriers and Oil Tankers, 2011 (ESP Code), for submission to MSC 107 for approval, with a view to subsequent adoption. They relate to the procedures for approval and certification of a firm engaged in thickness measurement of hull structures contained in the Code, so as to permit Administrations to exercise the right of auditing a company conducting thickness measurement of hull structures.  

Revised performance standards for water level detectors - amendment agreed  

The Sub-Committee agreed to draft amendments to the Revised performance standards for water level detectors on ships subject to SOLAS regulations II-1/25, II-1/25-1 and XII/12 (resolution MSC.188(79)/Rev.1), for submission to MSC 107 for adoption and dissemination as MSC.188(79)/Rev.2. The draft amendments aim to accurately define the measurement of the installation height of sensors.  

Unified interpretations agreed  

The Sub-Committee agreed to draft unified interpretations, for submission to the MSC, concerning: 

  • mooring arrangements and equipment;  

  • pressure testing after a fire test for penetrations in watertight divisions; 

  • the SOLAS chapter II-1 amendments adopted at MSC 102 and MSC 103; and 

  • the 2008 Intact Stability Code.