BfR-Wissenschaft 
53 
9 Decision making process 
Ivan Calvez 
Centre of Documentation, Research and Experimentation on Accidental Water Pollution 
(Cedre), Brest, France 
Introduction 
Aiming at providing the general public and oil spill responders with pertinent information doc 
uments and practical guidelines under the framework of the International Convention on Oil 
Pollution Preparedness, Response and Co-operation (OPRC), the 61 st session of the Marine 
Environmental Committee (MEPC) of the International Maritime Organization (IMO) decided 
to review the existing IMO guideline (dating from 1995) on the use of oil spill dispersants at 
sea. 
To this end, a Pollution Prevention and Response (PPR) inter-sessional correspondence 
group, including representatives from various countries and from both public/private sector, 
coordinated by CEntre de Documentation Recherche et Expérimentations sur les pollutions 
accidentelles des eaux (Cedre) (France) and Department Fisheries and Oceans (DFO) 
(Canada), has been tasked to draft parts l-lll of an upcoming revised “Guideline for the use 
of dispersants for combating oil pollution at sea”. Those parts, approved by MEPC, address 
specific issues as follows 1 : 
• Part I (Basic Information on Dispersants and Their Application) 
• Part II (Outline for a National Policy) 
• Part III (Operational and Technical Sheets) 
In particular, Part II aims at assisting competent authorities in defining/reviewing their policy 
regarding chemical dispersants use at sea. In a nutshell, it sums up tasks to be completed 
when establishing a national oil spill contingency plan (NOSCP), integrating scientific issues 
(oil dispersibility studies, principles for NEBA 2 , geographical boundaries...), technical issues 
(selection processes for dispersants, spraying equipment...), as well as operational/logistical 
related issues (e.g. authorities in charge, flight pre-authorizations, efficiency assess 
ment/monitoring ops, ancillary resources...). 
Amongst various topics, it provides a rationale for facilitating the decision-making process 
when considering dispersant application at the time of the incident. This process may be rep 
resented under the form of a decision-tree, laid out through 3 successive steps addressing 3 
essential concerns: oil dispersibility, potential impacts, and logistical capability. 
Chemical dispersion is one of the available response strategies to combat oil spills at sea, 
amongst which containment and mechanical recovery is one of the most typical. As for any 
technique and despite having operational advantages, its applicability may be impeded by 
different factors (oil properties, metoceanic features, etc.). Thus, the selection of the most 
appropriate strategy(ies) should rely upon a comparative examination of the options own 
merits, i.e. their expected feasibility, efficiency, as well as overall benefit (i.e. mitigation of 
environmental/economic impacts). 
Applied onto oil slicks, chemical dispersants tend: 
(i) to reduce interfacial tension between water and oil and, as a result, allow for a 
natural (wave-induced) mixing of the oil into tiny droplets, as well as 
(ii) to prevent their coalescence (reverting, eventually, into an water-in-oil emulsion 
slick). 
1 Part IV (Sub-sea Dispersant Application) is in progress, under the coordination of the United States Cost Guard 
(USCG). 
2 Net Environmental Benefit Analysis