Investigation of chemical release and biota on seabed test fields in Grenlandsfjordene 2018-2019

Summary

Six test fields for thin layer capping were established in the Grenland fjords in 2009. The purpose was to test the suitability of this method to reduce the spread and bioavailability of dioxins from historically contaminated sediments. Classified according to Norwegian guidelines, the sediments in Ormerfjorden were "heavily polluted" (class IV) with dioxins, while the sediments in Eidangerfjorden were "very heavily polluted" (class V). The fields were established in the Ormerfjord (about 30 m deep) and the Eidangerfjord (about 100 m deep). Two fields were treated with suction dredged marine clay with activated carbon (AC), one field was treated with the same clay without AC and one field was treated with crushed rock (<2mm) from a limestone quarry on Langøya in the Oslofjord. In each of the fjords, a nearby, untreated reference field was established.