. 2002. Environmental and socio-economic impact assessment of Ekoreef, a multiple platform rigs-to-reefs development. -ICES Journal of Marine Science, 59: S300-S308.The North Sea Ekofisk oil field is approaching the end of its production, and various options are being considered regarding future use or demolition of the platforms. One option is the rigs-to-reefs initiative. OSPAR and Norwegian national legislation contain provisions that allow for the creation of artificial reefs providing they do not hinder other users and do not cause significant pollution. More generally, the creation of sizeable artificial reefs using redundant offshore steel structures is only sensible if positive impacts outweigh negative impacts. At an early stage in the cessation process, we carried out an impact assessment to identify factors that would present special environmental or socio-economic risks or benefits. Thirty-nine impacts, positive and negative, were identified and grouped under the following headings: exploitable fish stocks (8); local biota (7); sediments (4); water column (2); energy and emissions (2); socio-economics (10); other (6). Techniques by which to estimate their likely severity in general and the potential for their reduction (negative impacts) or maximization (positive impacts) are summarized. Semi-quantitative severity scores for all impacts identified were assigned to each of 11 reef-creation options. These were totalled and the options were then ranked accordingly. From an environmental and ecological (including commercial fish stocks) perspective, the results indicate that reef use for protection would be a better option than use for commercial fishing, although differences between the two were not large. The rank order did not discriminate among four of the suggested reef locations. However, toppling in situ was clearly identified as the worst scenario, whereas reef creation at a relatively clean site offered the most promising perspective.

No abstract

There are approximately 70 working and planned structures in the Norwegian sector of the North Sea. The majority are steel-legged installations (oil and gas jackets) placed in depths ranging from 70 to 200 m. Several oil fields and structures are soon to be abandoned. Production from the North-east Frigg and Odin fields, was stopped in 1993 and 1994 respectively.

There is a growing concern regarding the fate of oil and gas facilities for which abandonment is programmed as a result of declining production. Different abandonment options have been proposed for consideration in recent years, varying from total removal of all elements of the installations to toppling in place or abandonment in-situ of temporary or permanent placement of one or several elements of an installation on the seabed could be seen as a potential source of pollution. The probability of pollution depends on the type of installation, procedures for cleaning the platform and the nature and sensitivity of the receiving environment. This paper presents the objectives and recommended practice for the preparatory works required to rnder a cold state multifunction steel jacket installation clean. The basis for this framework procedure was an assessment of the technical limitations and relevant legislative requirements and constraints and the findings of a preliminary qualitative risk assessment of the potential environmental implications of the entry into the North Sea offshore marine environment of the residual materials inventory. An Appendix summarizes the recommended framework procedure developed that was based in part of the following recommendations proposed from the findings of the preliminary risk assessment:–all components containing PCBs should be removed;–all components containing halons/freons should be removed;–persistent synthetic substances should be removed where practical;–production chemicals should be taken onshore for disposal;–topside tanks and pipework should be cleaned as far as practical to removed residual sediments containing heavy metals and hydrocarbons; and–components/equipment containing radionuclides should be removed.

Samples of different fish species were obtained at different sites in the North Sea, Bank of Halten and NW of the Faroe Islands and analysed by GC/MS for selected hydrocarbons. Petrogenic contamination of different origin was observed in almost all samples. Tainting, by organoleptic analyses of cod, was not traced.