IPIECA report series: choosing spill response options to minimise damage Net Environmental Benefit Analysis
After an oil spill, urgent decisions need to be made about how to minimise environmental and socio-economic impacts. The advantages and disadvantages of different responses need to be compared with each other and with natural clean-up. This process is called Net Environmental Benefit Analysis.
The process must take into account the circumstances of the spill, the practicalities of clean-up response, the relative impacts of oil and clean-up options, and some kind of judgement on the relative importance of social, economic and environmental factors.
Decisions are best and most rapidly made if contingency planning has included reviews of environmental and socioeconomic information, and consultations and agreements by appropriate organisations.
Aims of spill response
The aims are to minimise damage to environmental and socioeconomic resources, and to reduce the time for recovery. This can involve:
• Guiding or re-distr ibuting the oil into less sensitive environmental components;
• Removing oil from the area of concern and disposing of it responsibly.
Initiation of a response, or a decision to stop cleaning and leave an area for natural clean-up, should be based on an evaluation made both before the spill (as part of the contingency planning process) and after it.
The evaluation process
Evaluation typically involves the following steps:
• Collect information on physical characteristics, ecology and human use of environmental and other resources of the area of interest.
• Review previous spill case histories and experimental results which are relevant to the area and to response methods which could be used.
• On the basis of previous exper ience, predict the likely environmental outcomes if the proposed response is used, and if the area is left for natural clean-up.
• Compare and weigh the advantages and disadvantages of possible responses with those of natural clean-up.
Each of these steps is considered in detail in the text.
Considerations and examples
Oil on the water
When a large spill occurs many miles offshore and it is not clear where the oil will move, a wide-ranging preliminary evaluation is an appropriate precaution, Rapid decision making is particularly important for nearshore situations, where there may be only a few hours available before the oil reaches the shore.
If sea conditions preclude containment and recovery, dispersant spraying may be the only possible option if there is to be any atsea response.
Oil on the shore
If large volumes of mobile oil are present on the shore surface, a rapid response is necessary before the oil spreads. For some shores, ecological recovery times may be reduced by rapid action to remove smothering or particularly toxic oil. In contrast, more time can be given to decisions involving small amounts of weathered
oil firmly stuck to the shore or retained beneath the surface.