Offshore renewable energy: decommissioning guidance for Scottish waters

7. Environmental and safety considerations

Overall approach

7.1 This chapter covers: the default requirement for full removal of installations, statutory notifications, environmental information and role of the landlord with regard to residual liabilities. It does not contain a prescriptive set of technical requirements for decommissioning, as these will vary according to the installation and location, with best practice in methods expected to develop over time.

7.2 Decommissioning programmes must set out the extent of infrastructure to be removed, methods and processes (based on current methods). Decommissioning programmes must include a base case of all infrastructure being removed, alongside any alternatives that the operator proposes, backed up by evidence and reasoning for selection of the preferred option.

7.3 Section 105(8) of the Energy Act sets out that a decommissioning programme must:

a) set out measures to be taken for decommissioning the relevant object;

b) contain an estimate of the expenditure likely to be incurred in carrying out those measures;

c) make provision for the determination of the times at which, or the periods within which, those measures will have to be taken;

d) if it proposes that the relevant object will be wholly or partly removed from a place in waters regulated under this chapter, include provision about restoring that place to the condition that it was in prior to the construction of the object; and

e) if it proposes that the relevant object will be left in position at a place in waters regulated under this chapter or will not be wholly removed from a place in such waters, include provision about whatever continuing monitoring and maintenance of the object will be necessary.

7.4 Decommissioning programmes will be subject to review during the operational period and this will provide an opportunity to incorporate new information and challenge previous assumptions.

Presumption for full removal

7.5 To minimise residual liabilities, retain value in Crown Estate Scotland assets, maximise seabed re-use and for the safety of other marine users, it is expected that all relevant objects will be fully removed at the end of their operational life. The approval of decommissioning programmes will be based on this assumption.

7.6 The standards for the removal of offshore installations should not fall below those set by the IMO in 1989^[9] (or successor standards). the Scottish Ministers will consider exceptions from full removal in line with those standards, only on presentation of compelling evidence that removal would create unacceptable risks to personnel or to the marine environment, be technically unfeasible or involve extreme costs. Operators should note that in certain circumstances, such as in proximity to navigational routes, the IMO does not grant exceptions. IMO guideline 3.13 states that no installation or structure should go on the continental shelf or any exclusive economic zone unless it has been designed for full removal. The Scottish Ministers endorse the principle that relevant objects should be designed and constructed to facilitate full removal.

7.7 In all cases, evidence must be presented in decommissioning programmes to allow a costed evaluation of decommissioning options, including full removal, and advice sought from the relevant statutory bodies.

7.8 If making arguments for exceptions to full decommissioning, the responsible person should take the following points into account:

• arguments should be tailored to the individual site and should set out whether the risks are equal across all parts of the site (for buried cables for example, are some areas of the site more prone to sediment shift?)
• arguments should be relative to the effect of conducting the activity during construction
• the IMO exception for 'extreme cost' is not normally expected to be accepted where it is the sole reason being cited for not fully removing a relevant object
• the responsible person is encouraged to consider using the 'Comparative Assessment Framework' set out in the UK Government's decommissioning guidance for the Oil and Gas sector when determining and setting out their position^[10]

Method of removal

7.9 Removal techniques are likely to evolve as experience (including experience of removing oil and gas installations) is gained and technology advances. The following aspects should be factored into your methods of removal:

• other uses of the sea
• safety of surface and subsurface navigation
• health and safety considerations
• environmental impacts

Risks to mariners and notifications

7.10 Requirements in relation to notification and marking of any remains will be contained within project specific marine licenses, as will requirements for navigational aids and marking during the removal process.

7.11 It will be important to ensure that where any deferral of the approved decommissioning programme for a scheme has been agreed by the Scottish Ministers, that the need to maintain any ongoing mitigation measures, such as the provision of navigational warning lighting or aviation radar mitigation schemes associated with that scheme, is taken into account to coordinate the continuation of these measures until decommissioning does occur or a new deployment commences using that infrastructure.

7.12 It is the responsibility of the responsible person to ensure that all health and safety requirements are met.

Sea-bed clearance

7.13 Following decommissioning, it will be important for the responsible person to confirm that, where full removal of installed infrastructure has been stipulated, the site has been cleared, in accordance with the approved decommissioning programme, and to provide evidence that this has been achieved (see paragraphs 7.20 to 7.22).

7.14 The area covered for debris clearance will be decided on a case-by-case basis, taking account of the guidance for oil and gas installations which specifies a 500 metre radius around any installation as the minimum area to be covered for debris clearance. (It is recognised, though, that the nature and size of OREIs differs from that of oil and gas installations).

7.15 The Scottish Ministers would expect to see independent, third party involvement in providing evidence that the site has been cleared. Decommissioning programmes should set out the responsible person's proposals for achieving this. There are various forms of evidence which may be presented, examples might include over-trawling of the site or the presence of an independent observer during site clearance operations.

On-land management of waste

7.16 Waste from decommissioning should be managed in line with the waste hierarchy. This gives preference to reuse, then recycling and then recovery (e.g. incineration with energy recovery) with disposal (e.g. landfill) the least preferable waste management option. The Scottish Ministers do not consider disposal of waste at sea to be acceptable. Waste management must be carried out in accordance with all relevant legislation at the time, including control of any hazardous wastes.

Post-decommissioning survey / report

7.17 Typically responsible persons will be required to undertake a survey following decommissioning to enable identification and subsequent recovery of any debris located on the sea-bed which may have arisen from the responsible person's activities and which may pose a risk to navigation, other users of the sea or the marine environment.

7.18 A post decommissioning report is required in the decommissioning programme and must be submitted within the agreed timescale, following completion of decommissioning works. This must be in the format proposed in the approved decommissioning programme. The report must include:

• evidence (e.g. photographic evidence of infrastructure out of the water, or survey footage of the seabed) that all infrastructure that was due to be removed, according to the decommissioning programme, has been removed
• if infrastructure is left in situ, evidence that it has been cut off / buried / otherwise treated in accordance with the decommissioning programme and references to any future monitoring, maintenance and mitigation set out in the decommissioning programme
• references to compliance with permitting (such as marine licence) obligations
• a comparative analysis of predicted and actual costs.

7.19 The Scottish Ministers will review the post-decommissioning report and decide whether to accept it as evidence that the decommissioning has been carried out in accordance with the decommissioning programme.

Post-decommissioning, monitoring, maintenance and management of site

7.20 In situations where any part of an installation is not removed entirely, long term monitoring will be required. The objective of the monitoring is to identify any new or increased risks to navigation or other users of the sea which may be posed by remaining materials (for example, where cables or foundations may have become exposed due to natural sediment dynamics). Appropriate action should be taken to mitigate the risks.

7.21 If necessary, the monitoring regime may be adapted over time where agreed to by the Scottish Ministers.

7.22 The Scottish Ministers will agree with the responsible person when the monitoring programme may cease, taking account of any risks to navigation or other users of the sea which may be posed by remaining materials. Requirements would always be considered on a case-by-case basis, taking account of the specific risks posed in each case. Whether there was a need for further monitoring would be considered in the light of the results of these surveys. Monitoring arrangements for wave and tidal demonstrator projects are normally expected to be limited, or not required at all if full removal is involved and any post-decommissioning survey shows this has been achieved. Monitoring reports should be submitted to the Scottish Ministers, together with proposals for any maintenance or remedial work that may be required. The reports should also be published by appropriate means.