Most people are familiar with risk assessments used for onshore LNG developments, however, people are less familiar with marine risks and it is useful to review some aspects related to these. Generally, marine LNG transportation has been conducted safely for over 50 years, so the driver has been prudent management of a risk, rather than a response to accidents.
Both the USA and Canada address marine risks from LNG cargo and fuel but in different ways. In the USA the approach is governed by Waterway Suitability Assessments (WSA) approved by the USCG (the Coast Guard), whereas in Canada the approach is governed by TERMPOL studies (Technical Review Process of Marine Terminal Systems and Transshipment Sites) reviewed by Transport Canada.
WSA historically was driven by the events of Sept 11 to assure that accidental and intentional events would be properly addressed and that any consequential impacts would be of a manageable scale. To this end, Sandia National Laboratory carried out a series of numerical assessments and large-scale experiments to establish fire and dispersion consequence zones. These topics are of significant technical complexity, so the USCG has established a Liquefied Gas Carrier National Center of Excellence in Port Arthur Texas to provide advice and training for regional USCG offices. FERC also has an important role in assessing WSA submissions.
TERMPOL assessments are quite different. Historically TERMPOL was developed to address accidental risks from oil carriers with environmental impacts, but it was extended to address chemicals and liquefied gas carriers as well. It focuses on the marine transportation components of a project and examines the safety of tankers entering Canadian waters, navigating through channels, approaching berthing at a marine terminal, loading or unloading activities, and the marine terminal itself. TERMPOL assessments are voluntary, extensive and cover the entire transportation and berthing system. TERMPOL studies are also public documents, and thus greater explanations are provided. DNV GL normally uses a detailed marine transportation risk model (MARCS) that considers more than 50 aspects relating to navigational aids, tugs, pilots, competence, regulatory controls, etc. The use of MARCS for LNG transportation has been less common in the USA, although it has been used for sensitive navigation risk studies (Prince William Sound, and the Aleutian Islands). There is a current navigation study for the Columbia River covering all accidental events leading to spills and this covers LNG. This is a public study and demonstrates the use of quantitative risk models for LNG transportation safety.
Marine risks from LNG do not only arise from large vessels. LNG bunkering is in use or under discussion in many locations globally. This introduces smaller quantities but more frequent movements of LNG cargoes in ports, but without the full range of safeguards afforded to large carriers (pilots, tugs, escorts, etc.). DNV GL in a study for the US Maritime Administration (MARAD) reviewed the many possible bunkering configurations and what needs to be done to assure safety. This is all feasible and LNG bunkering can be achieved both safely and economically.
Overall, the use of risk management approaches addressing both design features and operational controls to achieve high levels of transportation safety is an integral part of the approval process and provides an equivalent approach to shore-based facilities. The US uses less quantified risk approaches than some other jurisdictions, but this may be changing. The use of detailed, validated risk models provides a traceable logic pathway that can provide confidence to the public and justification for any needed enhancements to safeguards.
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Image courtesy of DNV GL
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