70 
Hunt - Operational experience worldwide 
Operational Experience of dispersant use 
When used judiciously in appropriate conditions, dispersants can be an effective oil spill re 
sponse strategy. In open water dispersants are capable of rapidly transferring large quanti 
ties of floating oil from the sea surface into the top few metres of the water column where it is 
diluted through the action of sub-surface currents and subsequently degraded by naturally 
occurring micro-organisms. In many cases significant environmental and economic benefits 
can be achieved through the use of dispersants, particularly when other at-sea response 
techniques are limited by weather conditions or availability of resources. 
However, as with all spill response techniques, when formulating a strategy the application of 
dispersants must be carefully considered to take into account the characteristics of the oil, 
the sea state, weather conditions and environmental or socio-economic sensitivities. When 
making the decision to use dispersants in a given scenario a key consideration ought to be 
the potential effect of dispersed oil on nearby sensitive sub-surface resources, such as fish 
spawning grounds or aquaculture installations. Ideally the risk and consequences of such 
impacts would be compared and contrasted with the implications of following alternative 
strategies. For instance, the implications of dispersing oil offshore might be contrasted with 
the potential impacts of floating oil on seabird populations, or the effect of stranded oil on 
sensitive coastal habitats, such as saltmarshes or mudflats. This balanced approach to the 
formulation of a spill response strategy is often referred to as Net Environmental Benefit 
Analysis (NEBA), and when working through this process it can be particularly helpful to con 
sider the lessons learned from responses to past spills. Taking account of the particular cir 
cumstances of case studies can help to inform the decision-making process during the re 
sponse to a spill, and also during the contingency planning process. 
In this section of our report, we provide a summary of the main messages delivered during 
the ITOPF presentation given at the workshop in Berlin on the subject of ‘International Expe 
rience of Dispersant Use at Ship-Sourced Spills’. The talk focussed on the experience gained 
and lessons learned during the responses to four international oil spill incidents that involved 
the application of dispersant. 
Experience of Large-Scale Application 
Dispersant application at sea is frequently observed by ITOPF when attending small and 
medium-scale oil spills in countries where this is a favoured method of response. However, 
detailed information on the effectiveness of operations is rarely documented or available for 
subsequent review by the international spill response community. For instance, the specific 
rationale and decision-making process behind their use is often unclear; and technical details 
such as the methods of application, application rates, type of dispersant, testing protocols, 
monitoring of effectiveness or potential impacts are often uncertain, particularly if a variety of 
different private contractors are involved and they are not directly controlled by the relevant 
authorities. 
The relative paucity of detailed information on dispersant application at smaller scale inci 
dents makes it very difficult to take account of such cases when considering the relative mer 
its and potential risks associated with this key response strategy. However, information is 
often more readily available in relation to major spills. For these larger cases it is frequently 
possible to benefit from different perspectives from the organisations and individuals directly 
involved in operations, such as oil spill response organisations (OSROs), scientific institutes 
and international technical advisers, in addition to the government authorities taking the lead 
on the spill response. Having access to a variety of viewpoints in this way can help to build a 
more complete picture of the actions taken and the lessons learned. In addition, after dealing 
with major incidents, national governments often carry out a thorough review of the response 
activities carried out and their relative merits in order to assess their own spill response ca