BfR-Wissenschaft 
57 
The definition of areas where chemical dispersion can be reasonably undertaken is a rela 
tively long and complex process, since it should account for many local environmental pa 
rameters and data (currents, ecological resources and related sensitivities, etc.). Such a task 
-that is having defined geographical boundaries for the use of dispersants- can hardly be 
carried out during an incident. More realistically, it should be included in contingency plan 
ning activities: 
• through scenarios-based studies, allowing for a comparison of expected environmen 
tal and socio-economic impacts under “dispersed oil scenario” vs. “undispersed oil 
scenario” (mechanical recovery at-sea, shoreline cleanup); 
• according to a NEBA approach, taking into account local characteristics: sensitive 
ecological and socio-economic resources (e.g. species of environmental value, ma 
rine protected areas, fisheries resources, life cycles and seasonal variations, and mi 
gration of the marine species of interest, currents). 
These areas may also be predefined within boundaries (i.e. distance from the shore and wa 
ter depth allowing for sufficient dilution) corresponding to chemical dispersion of spills of in 
creasing magnitude, from small [e.g. up to 200 t. spills] to large [e.g. larger than 200 t.] 
events. 
At the time of a spill, the first step for decision is to assess if the oil is sufficiently far from the 
shoreline or from other sensitive items, so as not to cause damage. If geographical bounda 
ries for dispersant use (see above) have been pre-established, decision may be made ac 
cording to the location of the slicks: if those are outside (offshore) the boundaries, chemical 
dispersion may be implemented. Otherwise, or in case no boundaries have been pre- 
established, decision may rely upon a NEBA approach carried out using drift models and 
available data about ecological resources at risk (maps, distribution, sensitivities, etc.). 
Pre defined geographical boundaries 
allowing dispersant use along coasts 
(Based on spill scenario for Tier 1,2 and 3) 
Figure 9.3: Detailed flowchart for Q2 “Is dispersion beneficial from an environmental viewpoint?” (Note: 
Yellow boxes indicate information which should be, as possible, made available in NOSCP) (adapt, from 
Merlin, 2015).