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Detailed development plan for sea areas in Vats- and Yrkefjorden. Environmental impact assessment. Subtopic: the marine environment

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Torgeir Heggelund Bakke, Trine Dale, Lars Gunder Golmen, Astri J.S. Kvassnes, Torbjørn Martin Johnsen, Åse Åtland


The environmental impact assessment (EIA) covers accidental discharges that according to AF Decom Offshore AS (AFDO) may potentially occur in connection to the planned industrial activities in the sea outside AF Miljøbase Vats at Raunes. Accidents may cause input to the sea of heavy metals, ethylene glycol, oil (hydraulic and transmission oil, diesel oil, crude oil), polychlorinated biphenyls (PCBs), naturally occurring radioactive material (NORM), biocides, and corrosion inhibitors. For each of these AFDO has provided a conservative estimate of magnitude and duration of individual incidents. Potential no-effects concentrations (PNEC) at chronic exposure to these compounds are proposed on basis of literature, except for marine growth and NORM. The impact assessment estimates the extent of the sea area or volume within which concentrations of the potential input compounds will be high enough to represent a risk of toxic effects to marine organisms. Outside this impact zone effects are not likely. The assessment also takes into account the time it takes to reach non-toxic concentrations through natural dilution with recipient water. Extent and duration is then assessed against the distribution and value of the natural resources in the fjord areas. If discharges of undesirable substances to the sea from the planned activities in the fjord are anticipated, a permit covering such activities pursuant to the pollution control act will be required in each case. On basis of expected current patterns and hydrographical conditions numerical modelling predicts that a discharge plume will be diluted 400-700 times at 100 m distance, 850-1300 times at 200 m distance, and 2500->3000 times at 500 m distance from the two most likely positions for the industrial activities. The time it takes to reach these dilutions ranges from a few minutes to one hour.