RIASSUNTO
Abstract
This paper describes how simulations with a recently developed model systemhave been used as input to a Net Environmental Benefit Analysis, to evaluate astrategy for use of chemical dispersants as an integrated part of the initialresponse at two Norwegian oil fields. A scenario with release of 100 m3 crudeoil has been used as an example.
The results indicate that the use of chemical dispersants generally gives afaster removal of oil from the sea surface, as compared to mechanical recovery.On the other hand, dispersant application increases somewhat the concentrationsof dispersed oil and dissolved oil components in the water column. Thedispersed and dissolved oil dilutes to low levels within a few hours in deepwater. Based on a NEBA evaluation it is suggested that mechanical recovery begiven priority during the fish spawning season, while dispersant applicationshould be prioritised during periods with high sea bird activity in thearea.
Introduction
In Norway, mechanical recovery has traditionally been the preferred responsetechnique for the past two decades, with removal of oil from the environment asthe key goal. More recently, the Norwegian Pollution Control Authority (SFT)has opened the door to the consideration of dispersant use in certainsituations. The responsibility for defining which situation may be appropriatefor dispersant application lies with the operating oil companies. Theirdecisions are subject to review and approval by SFT.
The decision of whether to use dispersants in a given situation must be madeextremely rapidly. The documentation basis for the decision must take intoaccount the potential environmental consequences of alternative responsestrategies, and the chosen response must be practical to use. Detaileddocumentation for when, where and how to use dispersants effectively in a spillsituation must be integrated into the contingency plan.
Net Environmental Benefit Analysis (NEBA). The principle of NEBA is animportant aspect in oil spill response analysis. From an ecological point ofview, NEBA consists of the weighing of advantages and disadvantages ofalternative oil spill responses for all aspects of environmental damage,compared with no response.
NEBA is used for:
* oil spill response planning (pre-spill analysis of spill scenarios),
* addressing potential conflict of interest during the contingency planningprocess,
* weighing the advantages and disadvantages of alternative response methodsversus no response
NEBA requires the development of quantitative weighing methods, so thatcomparison of impacts on different resources can be carried out objectively.For example, the choice of a dispersant application rather than (or incombination with) mechanical cleanup may lead to reduced potential exposure forbirds and beaches, but may at the same time increase the exposure for organismsin the water column. The objective is to choose a response strategy thatminimizes the net environmental injury.