Sammendrag
This report is an update to NIVA report 7276-2018 " Tiltaksplan for forurenset sjøbunn utenfor Elkem
Carbon, Kristiansand " (Olsen and medarb. 2018). Based on new analyses and modelling, the design
of erosion protection has been presented as part of capping layers of the contaminated sediments in
Elkembukta. The erosion protection will prevent resuspension from ship maneuvering. The capping
layer and the erosion protection layer must be designed in accordance with applicable regulations
and standards. In this context, geotechnical calculations should also be carried out to control stability
and carrying capacity in the area. In Fiskåbukta, where the risk from PAH is relatively small and the
condition of sediment-living animals is good, it is in the remediation action plan recommended
monitored natural recovery to monitor the effect of emission reductions on sediment concentrations
and ecological risk associated with PAH. The recommendation does not change as a result of this
update. In recent years, Elkem Carbon has focused on source control to reduce emissions. This has
meant that inflows to sea of PAH with process water today are in the range of 5-10 PAH16 per year.
Elkem Carbon is in the process of reducing PAH with surface water. As of today, estimated discharges
of surface water are in the range of 25 kg of PAH16 per year. Further measures are being taken to
reduce this. This work is important for minimizing the recontamination of the capping layers and it is
recommended that this work be given priority.
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