GUINEVERE INSTALLATION DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT
2018
Guinevere Installation Decommissioning Project Environmental Impact Assessment
PERENCO 3 Central Avenue | St Andrews Business Park Norwich | Norfolk | NR7 0HR
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GUINEVERE INSTALLATION DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT
Document Control Page Document Reference SN-PG-BX-AT-FD-000002 Number:
Revision Record DATE REV NO. DESCRIPTION PREPARED CHECKED APPROVED 08/05/18 01 Draft for PUK review D Morgan G Jones (BMT G Nxumalo (BMT Cordah) Cordah) (Perenco) 04/06/18 02 Installation only D Morgan G Jones (BMT G Nxumalo (BMT Cordah) Cordah) (Perenco) 09/07/2018 03 BEIS comments G MacGlennon G Nxumalo G Nxumalo addressed (Perenco) (Perenco) (Perenco)
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Standard Information Sheet Information Project Name Guinevere Installation Decommissioning Project Environmental Impact Assessment BEIS Reference No. n/a Type of Project Decommissioning Undertaker Name Perenco UK Limited Undertaker Address St Andrews Business Park, 3 Central Ave, Norwich, Norfolk, NR7 0HR Licensees/Owners Perenco Gas (UK) Limited (75%) Hansa Hydrocarbons (LAPS) Limited (25%) Short Description Perenco UK Limited propose to decommission the Guinevere Installation which is located within the UKCS Block 48/17b in the southern North Sea. Cessation of Production was approved by the Oil and Gas Authority in December 2016. This Environmental Impact Assessment has been prepared to support the Guinevere Installation Decommissioning Programme.
The infrastructure which is included within the scope of the Guinevere Decommissioning Programme is summarised below: One (1) platform topside; One (1) four-legged jacket and four (4) piles; and Two (2) platform wells (48/17b-G1, 44/17b-G2).
Anticipated It is currently envisioned that decommissioning activities will commence during Commencement of late Q3 2018 and last for up to four years (although activities will not take Works concurrently during this period). Previously Submitted None Environmental Documents Significant Following the identification of the interactions between the proposed Environmental Guinevere decommissioning activities and the local environment, the Impacts Identified assessment of all potentially significant environmental impacts, and key environmental concerns identified as requiring consideration for impact assessment were investigated under the scope of the following:
Energy use and atmospheric emissions; Underwater noise; Seabed impacts; Societal impacts; and Accidental events.
PUK have, or intend to put in place sufficient safeguards to mitigate the potential environmental and societal risk and to monitor the implementation of these measures, a programme of which will be agreed with the Regulator. Document Prepared Perenco UK Limited in conjunction with BMT Cordah Limited By
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ABBREVIATIONS, ACRONYMS AND UNITS % Percentage °C Degrees Celsius µg Micrograms ACOPS Advisory Committee on Protection of the Sea AIS Automated Identification System Al Aluminium ALARP As Low As Reasonably Practicable API American Petroleum Institute As Arsenic Ba Barium bbls barrels BEIS Department for Business, Energy & Industrial Strategy (formerly DECC) BHA Bottom Hole Assembly BMAPA British Marine Aggregate Producers Association BOD Biological Oxygen Demand boepd Barrels of oil equivalent per day BSI British Standards Institute C Carbon Category I Fish with no swim bladder or other gas volume (particle motion detectors) Category II Fish with a swim bladder or other gas volume, and therefore susceptible to barotrauma, but where the organ is not involved in hearing (particle motion detectors) Category III Fish with a swim bladder or other gas volume, and therefore susceptible to barotrauma, where the organ is also involved in hearing (sound pressure and particle motion detectors) CCS Carbon Capture and Storage Cd Cadmium Cefas Centre for Environmental, Fisheries and Aquaculture Science CH4 Methane Cm centimetres CO2 Carbon dioxide COP Cessation of Production Cr Chromium cSAC Candidate Special Areas of Conservation CSV Construction Support Vessel Cu Copper dB Decibel dB re 1 µPa m Units of the zero-to-peak decibel ratio of sound pressure to a reference pressure of 1 (peak) micropascal at 1 metre (re 1 μPa m) in underwater acoustics dBht (species) Sound level in decibels above the hearing threshold of a species DECC Department of Energy & Climate Change (currently called BEIS) DEFRA Department for Environment, Food & Rural Affairs DP Decommissioning Programme DTI Department of Trade and Industry (currently BEIS) EA Environment Agency EBS Environmental Baseline Survey EC European Commission ED50 European Datum 1950 EDC Engineering Down and Cleaning
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ABBREVIATIONS, ACRONYMS AND UNITS EEC European Economic Community EIA Environmental Impact Assessment EPS European Protected Species ERL Effects Range Low ES Environmental Statement Espoo The Convention on Environmental Impact Assessment in a Transboundary Context EU European Union EUNIS European Nature Information System FAC First Aid Case FC&D Final Cleaning and Disconnect Fe Iron g grams GJ Gigajoules Hg Mercury HLV Heavy Lift Vessel HMX Explosive also known as Octogen HSE Health and Safety Executive HSSE Health, Safety, Security and Environment Hz Hertz ICES International Council for the Exploration of the Sea IoP Institute of Petroleum IPCC Intergovernmental Panel on Climate Change ISO International Organisation for Standardisation ITOPF The International Tanker Owners Pollution Federation Limited JNCC Joint Nature Conservation Committee JNCC Joint Nature Conservation Committee kg Kilogram(s) kHz kilohertz km Kilometre(s) km2 squared kilometre LAPS Lancelot Areas Pipeline System LAT Lowest Astronomical Tide m Metre(s) m/ s Metres per second m2 Squared metre(s) m3 Cubic metre(s) MARPOL International Convention for the Prevention of Pollution from Ships MAT Master Application Template MBES Multi-beam echo sounder MCA Marine and Coastguard Agency MCAA Marine and Coastal Access Act MCZ Marine Conservation Zone; rMCZ – recommended MCZ MEG Mono Ethylene Glycol Mg/ l Milligrams per litre mm Millimetre(s) MMO Marine Management Organisation MMObs Marine Mammal Observers Mn Manganese
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ABBREVIATIONS, ACRONYMS AND UNITS MoD Ministry of Defence MPA Marine Protected Area ms-1 Metres per second MSFD Marine Strategy Framework Directive MTC Medical Treatment Case NA Not Applicable Nb Niobium NFFO National Federation of Fishermen’s Organisation Ni Nickel nm Nautical Mile NMPI National Marine Plan International NOAA National Oceanic and Atmospheric Administration NORM Naturally Occurring Radioactive Materials NOx Nitrogen Oxide compound NRA Navigational Risk Assessment NUI Normally Unattended Installation OGA Oil and Gas Authority OGUK Oil and Gas UK OPEP Oil Pollution Emergency Plan OPOL Oil Pollution Operator’s Liability Fund OSPAR The Convention for the Protection of the Marine Environment of the North-East Atlantic OSPAR Oslo Paris Convention OSPAR Oslo and Paris Convention OSPAR Oslo Paris OSPAR Convention for the Protection of the Marine Environment of the North-East Atlantic OSRL Oil Spill Response Limited OWF Offshore Windfarm P Phosphorous P&A Plug and Abandon/ Abandonment PAH Polyaromatic hydrocarbon PAM Passive Acoustic Monitoring Pb Lead PETS Portal Environmental Tracking System Phi The Krumbein Phi logarithmic Scale for sediment sorting PL Pipeline POMS Perenco Operating Management System ppt Parts per Thousand PTS Permanent Threshold Shift – A permanent elevation of the hearing threshold resulting from physical damage to the sensory hair cells of the ear PUK Perenco UK Limited RIH Run In Hole RWC Real World Case s second S Sulphur SAC Special Area of Conservation; cSAC – candidate SAC SAT Subsidiary Application Template SCANS Small Cetaceans in the European Atlantic and North Sea SCI Site of Community Importance
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ABBREVIATIONS, ACRONYMS AND UNITS SD Standard Deviation SEA Strategic Environmental Assessment SEL Sound Exposure Level in dB re 1 µPa2 s SEMS Safety and Environmental Management System Si Silicon SLzp Zero to Peak Source Level - the decibel ratio of sound pressure to some reference pressure in dB at 1 m (re 1 μPa m) in underwater acoustics (zero-to-peak) SMRU Sea Mammal Research Unit Sn Tin SNS Southern North Sea SO2 Sulphur dioxide SOPEP Shipboard Oil Pollution Emergency Plan SOSI Seabirds Oil Sensitivity Index SOx Sulphur oxide compound SPA Special Protected Area; pSPA – possible SPA SPL Sound Pressure Level – the decibel ratio of sound pressure to some reference pressure in dB re 1 μPa in underwater acoustics (zero-to-peak or peak) SSB Spawning Stock Biomass SSS Side Scan Sonar t tonnes THC Total Hydrocarbons Ti Titanium TOC Total Organic Carbon TOM Total Organic Matter TTS Temporary Threshold Shift – Temporal and reversible elevation of the auditory threshold which is the minimum sound level that can be perceived by an animal in the absence of background noise UK United Kingdom UKCS United Kingdom Continental Shelf UKDMAP United Kingdom Digital Marine Atlas UKHO United Kingdom Hydrographical Office UTM Universal Transverse Mercator V Vanadium VMS Vessel Monitoring System VOC Volatile Organic Compounds w/w Wet weight WFD Water Framework Directive WIA Well Intervention Operations Application WMP Waste Management Plan WOW Wait on Weather Zn Zinc
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1 Non-Technical Summary Perenco UK Limited (PUK) ceased production from the Guinevere Field (situated in United Kingdom continental shelf Block 48/17b of the southern North Sea (Figure i) during Q2 2017 and is therefore preparing two decommissioning programmes to support the decommissioning of the installation and pipelines (and associated materials), respectively. This document presents the findings of the environmental impact assessment undertaken in support of the Guinevere Installation Decommissioning Programme. The purpose of the environmental impact assessment is to understand and communicate the potential significant environmental impacts associated with the project and to inform the decision-making process. This section of the document provides an overview of the environmental impact assessment associated with the decommissioning of the Guinevere installation.
Project Overview The Guinevere normally unmanned installation produced gas from two platform wells. A three-inch Mono Ethylene Glycol line piggybacked on an 8-inch export pipeline (both 6.92 kilometres) connect the Guinevere installation to the PUK operated Lancelot platform in Block 48/17a. The Guinevere installation is controlled remotely, via satellite and on-board diesel driven generator sets provide electrical power. During production, all produced fluids were passed through a production separator and gas and condensate were recombined in the export pipeline while produced water was discharged to sea. Over the past few years, PUK has explored all avenues for continuing production from the field, but in 2016 reached the conclusion that it is now uneconomical. Approval to cease production from the field was therefore granted by the Oil and Gas Authority in December 2016. Cessation of Production took place in the second quarter of 2017 and subject to approval. Decommissioning activities will commence offshore during the third quarter of 2018. It is currently envisaged that decommissioning activities will last for a maximum of four years (although activities will not be undertaken concurrently during this period). This Environmental Impact Assessment is in support of the Installation Decommissioning Programme only. Pipeline infrastructure and supporting materials will be covered by an updated version of the Environmental Impact Assessment and a Pipeline Decommissioning Programme.
Regulatory Context The decommissioning of offshore oil and gas infrastructure on the United Kingdom continental shelf is principally governed by the Petroleum Act 1998, as amended by the Energy Act 2008. The Petroleum Act sets out the requirements for a formal Decommissioning Programme which must be approved by the Department for Business, Energy and Industrial Strategy, formerly the Department for Energy and Climate Change, before the owners of an offshore installation or pipeline may proceed with decommissioning. Under the Guidance Notes: Decommissioning of Offshore Oil and Gas Installations and Pipelines (May 2018) the decommissioning programme must be supported by an environmental appraisal. This Guidance Notes state that an environmental appraisal should include an assessment of the following: All potential impacts on the marine environment including exposure of biota to contaminants associated with the installation; other biological impacts arising from physical effects; conflicts with the conservation of species, with the protection of their habitats, or with mariculture; and, interference with other legitimate uses of the sea. All potential impacts on other environmental resources; including emissions to the atmosphere, leaching to groundwater, discharges to surface fresh water and effects on the soil. Consumption of natural resources and energy associated with reuse and recycling.
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Other consequential effects on the physical environment which may be expected to result from the option. Potential impacts on amenities, the activities of communities and on future uses of the environment.
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Figure i: Guinevere Field infrastructure location map
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In addition, under the Marine and Coastal Access Act 2009 and the Marine (Scotland) Act 2010 a licence application will be required at the time of decommissioning and the supporting environmental impact assessment updated to reflect detailed engineering design and specific mitigation measures. The OSPAR Decision 98/3 on the Disposal of Disused Offshore Installations sets out the United Kingdom’s international obligations on the decommissioning of offshore installations. The OSPAR Decision prohibits the dumping and leaving wholly or partly in place of offshore installations. The topsides of all installations must be returned to shore, and all installations with a jacket weight of less than 10,000 tonnes must be completely removed for re-use, recycling or disposal on land. Any piles securing the jacket to the seabed should be cut below the natural seabed level at a depth that will ensure they remain buried. The depth of cutting is dependent upon the prevailing seabed conditions and currents.
Scope of the Guinevere Installation Decommissioning Programme The Guinevere infrastructure to be decommissioned comprises: One (1) platform topsides; One (1) four-legged jacket and associated four (4) piles; and Two (2) platform wells.
Decommissioning Studies PUK commissioned a number of studies to support the Guinevere decommissioning planning process and option evaluation, in order to determine the recommended decommissioning option and optimal engineering solution. The main findings and conclusions from these studies have been considered within this environmental impact assessment and the EIA process. Some of these studies include: Scoping brief for stakeholder engagement Pre-decommissioning environmental baseline survey Energy and emissions assessment to support the Guinevere Decommissioning Programme Guinevere wells plug and abandonment Decommissioning Environmental Impact Assessment Justification Navigational risk assessment around the Guinevere installation Underwater noise assessment Inventories of the assets, materials and hazardous materials on the Guinevere installation Quantitative risk assessment and high level hazard identification study of decommissioning and removal options A series of engineering studies and reports on the options for decommissioning the topside and jacket.
Recommended Decommissioning Options In addition to the plugging and abandonment of the two platform wells (in accordance with Oil and Gas United Kingdom Guidelines and Health and Safety Executive “Offshore Installations and Wells (Design and Construction etc.) Regulations 1996,” decommissioning activities will include the removal of the Guinevere normally unmanned installation from the seabed (as required under OSPAR Decision 98/3). Table i provides an overview of the recommended decommissioning options for each of the Guinevere infrastructure aspects. Table i: Summary of the recommended options for the Guinevere decommissioning programme
Infrastructure Selected option Topside Complete removal by single lift for reuse, recycling or final disposal onshore Jacket Complete removal by single lift for reuse, recycling or final disposal onshore
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Infrastructure Selected option Wells Plug and abandon
Environmental Settings and Sensitivities A key consideration when planning and finalising the Guinevere decommissioning programmes is to give a clear understanding of the surrounding environment. This section provides an overview of the physical, biological (Tables ii and iii) and socioeconomic environment (Table iv) both within the United Kingdom continental shelf Blocks 48/17a and 48/17b (the blocks of interest), as well as in the wider southern North Sea area. It should be noted that this includes the location of the Guinevere pipelines (as well as the Guinevere installation) and therefore provides the setting for a worst-case scenario for any associated environmental impact. Table ii: Key environmental characteristics and sensitivities within the vicinity of the Guinevere installation
Aspect Characteristics
The Guinevere installation is located in Block 48/17b, approximately 53 kilometres north of the nearest United Kingdom landfall, in North Site overview Norfolk, and approximately 116 kilometres to the west of the United Kingdom/ Netherlands transboundary line. The water depth at the Guinevere installation is, approximately, 18.4 metres. Conservation interests Annex I habitats No Annex I habitats are known to occur in the immediate vicinity of the Guinevere facilities. However, two of the three Annex I habitats can be found nearby in Special Areas of Conservation including those designated for “ sandbanks slightly covered by seawater all the time” and “Reefs” in the nearby North Norfolk Sandbanks and Saturn Reef SAC (12 kilometres to the east) and Inner Dowsing, Race Bank and North Ridge SAC (20 kilometres to the southwest). Annex II species All four Annex II species (harbour porpoise, bottlenose dolphin, grey seals and harbour seals) listed in Annex II species known to occur in United Kingdom offshore waters have been sighted within Quadrant 48 and surrounding quadrants. Marine protected areas Southern North Sea Special Area of 4 kilometres northeast of Guinevere Conservation North Norfolk Sandbanks and Saturn 12 kilometres east of Guinevere Reef Special Area of Conservation Inner Dowsing, Race Bank and North 20 kilometres southwest of Guinevere Ridge Special Area of Conservation Haisborough, Hammond and Winterton 43 kilometres southeast of Guinevere Special Area of Conservation The Wash and North Norfolk Coast 43 kilometres southwest of Guinevere Special Area of Conservation Wash Approach recommended Marine 8 kilometres southwest of Guinevere Conservation Zone Silver Pit recommended Marine 30 kilometres west of Guinevere Conservation Zone Holderness Offshore recommended 31 kilometres northwest of Guinevere Marine Conservation Zone Cromer Shoal Chalk Beds Marine 43 kilometres south of Guinevere Conservation Zone
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Aspect Characteristics
Greater Wash Special Protection Area 33 kilometres southwest of Guinevere North Norfolk Coast Special Protection 50 kilometres southwest of Guinevere Area Plankton In this area of the North Sea, the phytoplankton community is dominated by the dinoflagellate genus Ceratium and the zooplankton community by copepods (in terms of biomass and productivity), particularly Calanus species, which constitute a major food resource for many commercial fish species. Benthic environment Seabed sediments Particle size distribution analysis revealed the majority of samples to be dominated by sand-sized particles, with two stations containing over 98 percent sand. Benthic fauna The macrofauna throughout the Guinevere survey area showed some small-scale variability in terms of abundance, richness and species composition associated with the sediment composition across the survey area. The infaunal community was dominated by annelids, followed by crustaceans and molluscs in terms of species richness, however crustaceans were the dominant group with regard to individual abundance. Colonial epifauna were less dominant in terms of species richness and abundance. Aspect Months of the Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Fish spawning and nursery grounds in International Council for the Exploration of the Sea Rectangle 35F1 Mackerel N N N N NS* NS* NS* NS N N N N Herring N N N N N N N NS NS NS N N Cod N N N N N N N N N N N N Hake N N N N N N N N N N N N Haddock N N N N N N N N N N N N Whiting N NS NS NS NS NS N N N N N N Plaice N N N N N N N N N N N N Lemon sole N N N NS NS NS NS NS NS N N N Sole N N NS NS* NS N N N N N N N Sandeels NS NS N N N N N N N N NS NS Sprat N N N N N N N N N N N N Horse mackerel N N N N N N N N N N N N Key: Fish spawning/ nursery S spawning S* peak spawning N nursery Seabirds in Block 48/17 Seabirds sensitivity 3 3 3 3 5 5 5 3 4 2 1 3 Marine mammals Quadrant 48 and surrounding quadrants Harbour porpoise M H L H H L VH H L M L White-beaked dolphin L L M L M L L L M H L Minke whale L L L L L Long-finned pilot whale L Bottlenose dolphin L
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Aspect Characteristics
Common dolphin M White-sided dolphin L L Grey seals Grey seal density in the block 48/17 ranges from 0 to 1 seals per 5 km2. Harbour seals Harbour seal density in block 48/17 ranges from 1 to 10 seals per 5 km2. Seabird sensitivity key: Sensitivity Extremely 1 High 3 Low 5 high Very high 2 Medium 4 Cetacean abundance key: Cetacean abundance Very high VH Moderate M No data High H Low L
Table iii: Summary of socioeconomic characteristics and sensitivities
Aspect Characteristics Other users Commercial fisheries landings and value range from low to moderate within International Council for the Exploration of the Sea rectangles 35F1. Catch composition by weight of landings from United Kingdom and foreign vessels in ICES rectangle 35F1 for 2016 was dominated by crabs, lobsters and whelks. Between 2013 and 2016, the annual total live weight of fish landed from ICES rectangle 35F1 ranged from 928 tonnes in 2015 to 1,411 tonnes in 2013 and total annual value from £1,157,009 in Fishing 2015 to £1,286,988 in 2014. Fishing gear types include harvesting machines, traps and trawls. Vessel Monitoring Systems (data for all UK vessels greater than 15 metres in length landing into UK ports (2009 to 2013), shows that mobile demersal fishing activity was low within the blocks of interest and an area of high activity for lobster fishing lies in the northwest of International Council for the Exploration of the Sea Rectangle 35F1. Shipping activity Shipping density within the block of interest is regarded as moderate. Structures in the vicinity of the pipelines include the Guinevere and Lancelot Platforms Oil and Gas (both adjacent to the pipelines), the Excalibur platform (7 kilometres to the northeast) and the Waveney platform (7.3 kilometres to the south). Telecommunications No cables are laid within Block 48/17 No military activities occur in Block 48/17. There is a license condition obliging the license Military activities holder to notify the Ministry of Defence prior to any activities in this block. The closest wind farm (Dudgeon) to the pipelines is under construction located approximately 12.7 kilometres to the southeast of the nearest pipeline point. Windfarms Sheringham Shoal wind farm is located 31 kilometres to the south of the pipelines and a further consented wind farm will be located at Triton Knoll, 17 kilometres to the west of the pipelines. No designated historical wrecks have been recorded in Block 48/17. There are 70 wrecks Wrecks classed as dangerous by the United Kingdom Hydrographic Office in the vicinity of the Guinevere Decommissioning area, the closest one is located 3.9 kilometres to the west. The Hornsea project wind export cable is located 28 kilometres to the north of the Telecommunications pipelines. No telecommunication cables are present in Block 48/17.
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Two active dredging aggregate extraction sites are located in the vicinity of the Guinevere Aggregate extraction Decommissioning area, Outer Dowsing (515/2) and Outer Dowsing (515/1), 3.5 and 17.2 kilometres to the west, respectively. The Deborah gas storage area is located 47 kilometres to the southeast of the Guinevere Gas Storage facilities and is currently under agreement for lease.
Assessment of Environmental Effects and their Significance The potential environmental issues (or aspects) associated with the proposed Guinevere Installation Decommissioning Programme were identified through discussions with the PUK project team, an informal scoping exercise with key stakeholders and from the environmental team’s previous oil and gas project experience. At the time of writing the environmental impact assessment, some aspects of the proposed Guinevere decommissioning programme have yet to be finalised. Therefore, where project decisions are still to be made, a worst‐case scenario from an environmental perspective has been considered. Each of the potential environmental issues identified during the initial stage of the environmental impact assessment process was then assessed and their significance determined by combining the likelihood of occurrence (frequency/ probability) with the magnitude of impact (consequence). Cumulative and transboundary impacts have also been considered. The majority of issues were found to be of low or negligible risk to the environment (i.e. not significant) and were scoped out from detailed assessment in the environmental impact assessment. Some issues, however, were considered to be of medium risk to the environment (i.e. potentially significant). For these issues, mitigation measures were identified to either remove the potential impacts by design or minimise or manage the potential impacts through operational measures. Once mitigation measures were determined, the potential impacts were re‐assessed to determine whether the overall impact significance had been reduced. These remaining impacts are referred to as the residual impacts. A summary of the main findings of the environmental impact assessment process is provided below. Energy and Emissions Energy use and associated emissions resulting from the proposed Guinevere installation decommissioning activities are mainly attributed to the vessel and helicopter use. Standard mitigation measures have been identified to minimise energy usage by project vessels. The atmospheric emissions from the Guinevere installation’s decommissioning activities are unlikely to have any effect on sensitive receptors. Emissions from the Guinevere installation decommissioning activities will contribute to greenhouse gas emissions and have an insignificant cumulative and transboundary impact. Emissions will be kept to a practicable minimum. Total carbon dioxide emissions generated from the proposed Guinevere decommissioning operations represent a very small proportion (less than 0.2%) of the of the total annual carbon dioxide emissions from the United Kingdom continental shelf in 2016. Underwater Noise The subsea noise levels generated by surface vessels used during the decommissioning operations of the Guinevere installation are very unlikely to result in physiological damage to marine mammals. Depending on ambient noise levels, sensitive marine mammals may be locally displaced by noise from a vessel in its immediate vicinity, or by any other continuous noise source during the decommissioning activities at the Guinevere Field, however, the impact from vessels is not expected to be significant. The predicted cumulative source sound levels during the decommissioning operations involving explosive cutting indicate that fish (within 10.9 kilometres) and cetaceans (within 17.8 kilometres) may be injured or display significant behavioural displacement. However, it should be noted that the modelling is based on a highly conservative worst-case scenario of an unconfined blast at the seabed. In reality, the explosive
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Societal Impacts Potential damage or loss of demersal fishing gear, as a result of the rock-placement, will be minimised by notifying the appropriate organisations of any subsea structures left in place after decommissioning. In addition, overtrawlability trials will be undertaken during decommissioning and periodically thereafter. If the overtrawlability trial fails, additional rock-placement will be conducted as soon as practicable. There is no evidence of a drill cutting piles and any cuttings debris is considered to have been widely dispersed. As such, no societal impacts are anticipated as a result of this. The effect on local ships transiting the site is expected to be minimal since the mandatory 500 metre safety zone will remain around the Guinevere installation during the decommissioning activities, within which the majority of the decommissioning vessels will be located. Conversely, as the decommissioning activities proceed there will be a positive impact. New areas of sea(bed) will ultimately become available to fishers through the removal of the 500 metre safety exclusion zone. Discharges to Sea During the decommissioning of the Guinevere installation and the associated vessel operations, no long- term release of residual contaminants in the sediment into the water column (long-term) is anticipated. The total hydrocarbon content for all sampled locations from the Environmental Baseline Survey were below the OSPAR (2006) 95th percentile background level of THC for the southern North Sea (11.4 μgg-1). Any short-term (temporary) impacts during decommissioning or trawling operations will be due to the potential release of chemical contaminants; however, this will result in localised effects which are not
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GUINEVERE INSTALLATION DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT anticipated to have any discernible impact on the wider marine environment cumulatively or in combination with other activities. Accidental Events Hydrocarbon releases and chemical spills are the two types of accidental events that could occur during the Guinevere decommissioning activities. Although the likelihood of such a spill is remote, there is a potential risk to organisms in the immediate marine and coastal environment, and a socioeconomic impact if a spill were to occur. A worst-case scenario at the Guinevere installation location would result from a loss of diesel from vessel lift or collision. Diesel spills will disperse and dilute quickly, with a very low probability of hydrocarbons reaching the coastline. The likelihood of a hydrocarbon spill occurring is low and will not contribute to the overall spill risk in the area. The current Oil Pollution Emergency Plan for the Guinevere Field will provide effective spill management in the case of an accidental event. The potential sources of chemical spillages during the decommissioning of the Guinevere installation have been identified through a risk assessment workshop and identified as an accidental loss of fluids from subsea or topsides removal. The impacts of all the chemicals that may be used or discharged offshore during decommissioning will be assessed and reported to the Department for Business, Energy and Industrial Strategy in a relevant portal environmental tracking system application. Chemicals in pipelines will be flushed and returned to the platform for disposal under appropriate permits. Waste As the Guinevere installation is obsolete and/or in a degraded condition, it is not considered suitable for safe re-use. The majority of jacket and topside material will be recycled. Where necessary, hazardous waste resulting from the dismantling of the Guinevere installation will be pre-treated to reduce hazardous properties or, in some cases, render it non-hazardous prior to recycling or landfilling. Disposal of waste transported onshore for disposal will be provided by an approved waste management contractor, in compliance with PUK existing standards, policies and procedures. Environmental Management The Guinevere Installation’s decommissioning will be undertaken in accordance with the PUK safety and environmental management system which forms part of the PUK operating management system. The PUK SNS SEMS provides a uniform approach to every element of operations across SNS assets. With regards to health, safety, security and environmental management the purpose of the SEMS is to ensure that, as far as reasonably practicable, all of the installation’s activities are undertaken in accordance with PUK commitment to its QSSHE Policies and compliance with all relevant statutory provisions applicable to offshore operations within SNS. SEMS includes PUK, SNS and site specific processes and procedures through which the local business is delivered. The SEMS framework comprises 15 key components which together provide a roadmap to safe, environmentally conscious and reliable operations. The framework for the PUK SEMS is built around the 15 Perenco Standards which sets out high level targets which shall be complied with, a set of actions to be implemented, along with supporting information to provide guidance on implementation. It is these business processes, procedures and information that describes in more details how PUK achieves conformance with the Perenco Standards.
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PUK also hold International Organization for Standardisation 14001 standard certification and therefore have relevant documentation to support the decommissioning process from the perspective of environmental standards PUK intend to resource such projects through the utilisation of contractors, should these not be available within the business itself. PUK expects its main contractors to operate a management system that is compatible with the principles of the PUK Safety and Environmental Management System. PUK will develop a Safety and Environmental Management Plan for the Guinevere Installation Decommissioning Programme to ensure compliance with the PUK Safety, Health and Environment Policy and Safety and Environmental Management Systems, as well as with statutory requirements. The Safety and Environmental Management Plan will also incorporate all the mitigation measures which PUK has committed to implement, as identified during the Environmental Impact Assessment process and documented within this Environmental Impact Assessment, and will outline the processes PUK will follow in order to monitor compliance. PUK will audit its activities on a periodic basis to verify full implementation of its Safety and Environmental Management Systems and the Guinevere-specific Safety and Environmental Management Plan. Summary In summary, it is concluded that the proposed Guinevere Installation Decommissioning Programme will not result in any significant environmental impacts (including transboundary and cumulative impacts) provided that all identified mitigation measures are implemented.
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1 INTRODUCTION This section introduces Perenco UK Limited (PUK), explains the background to the proposed Guinevere Installation Decommissioning Project (DP), outlines the Environmental Impact Assessment (EIA) process that has been followed for the project and defines the structure of the Environmental Impact Assessment document. It also summaries the key issues raised during the stakeholder engagement process and, where applicable, indicates where these have been addressed within the EIA.
1.1 Project Background and Purpose
PUK is currently the operator of the Lancelot Area Pipeline System (LAPS) Gas Field in the southern North Sea (SNS). The Guinevere Field is part of this system and is operated by PUK (75%) on behalf of its partner Hansa Hydrocarbons Ltd (25%). The field is produced by two platform production wells, via a normally unattended installation (NUI), located within United Kingdom Continental Shelf (UKCS) Block 48/17b. The installation is located, approximately, 53 km from the nearest UK coastline and 116 km from the UK/ Netherlands median line. Processed and water-separated gas is exported through an 8” line (PL0874) to the Lancelot platform, 7 km away in UKCS Block 48/17a. The exported gas is comingled with gas produced on Lancelot and is then exported to the Bacton Terminal on the Norfolk coast via the PL0876 pipeline system. Mono Ethylene Glycol (MEG) is required to be injected into the Guinevere export pipeline for hydrate control and is supplied from the Lancelot platform via a 3.5” pipeline (PL0875) (Figure 1-1). PUK has explored all avenues for continuing production from the Guinevere Field, but concluded that it was no longer commercially viable. Production from the Guinevere Field commenced in 1988, however, since 2012 the field has been marginal, production rates have significantly declined and predicted recoverable volumes for 2017 have been deemed uncommercial. The Guinevere platform was installed in 1993 and some parts of the installation are still in good working order. For this reason, the reuse potential of some of the topsides components will be considered as a possible alternative to recycling and/ or disposal. PUK submitted an application to cease production from the Guinevere Installation to the Oil and Gas Authority (OGA), which was approved in December 2016. Cessation of Production (COP) took place in the second quarter of 2017 and PUK is now preparing a Decommissioning Programme (DP) to be submitted to the Department for Business, Energy & Industrial Strategy (BEIS) (formerly the Department of Energy and Climate Control [DECC]) for approval under the Petroleum Act 1998, as amended by the Energy Act 2008. In support of the Guinevere Installation DP, this document presents the findings of an EIA, as outlined in the BEIS Guidance Notes on Decommissioning of Offshore Oil and Gas Installations and Pipelines under the Petroleum Act 1998 (DECC, 2011a).
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Figure 1-1: Schematic showing the LAPS infrastructure adjacent to the Guinevere installation
1.2 Overview of the Guinevere Infrastructure to be Decommissioned
The infrastructure which is included within the scope of the Guinevere Installation DP and Decommissioning EIA is summarised below: One platform topsides; One four-legged jacket and four (4) piles; and Two platform wells (48/17b-G1, 44/17b-G2).
Figure 1-2 illustrates the location of this infrastructure within UKCS Block 48/17b. Further details are provided in Table 1-1.
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Figure 1-2: Location of Guinevere infrastructure (Source: UKOilandGasData 2017)
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Table 1-1: Location of Guinevere installation
Aspect Guinevere installation Location (latitude/longitude) 53° 24' 53” N (ED50, UTM Zone 31 N) 01° 16' 25” E UKCS block number 48/17b ICES rectangle 35F1 Distance to UK coast 53 km Distance to UK/Netherlands median line 116 km Key: International Council for the Exploration of the Sea (ICES); Universal Transverse Mercator (UTM).
PUK proposes to remove the Guinevere Installation from the seabed, as required under the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR) Decision 98/3 in line with regulatory requirements and industry best practice. Limited preparation activities started at the Guinevere Installation during the third quarter of 2017 in the form of a well abandonment campaign. The wells have now all been abandoned and the conductors have been cut and removed. The Guinevere Installation decommissioning activities will commence offshore in Q4 of 2018 and, subject to regulatory approval, work is expected to take place intermittently over the course of the following four years. 1.3 Purpose of the Environmental Impact Assessment An EIA is a systematic process that considers how a project will change existing environmental and societal conditions, and assesses the consequence and significance of such changes (Table 1-2). It is an iterative process that is generally initiated at a project’s inception and provides an aid to project decision-making throughout the planning and design phases so that, where practical, potentially significant environmental effects can be mitigated at the source. The purpose of the EIA process is to understand and communicate the significant environmental impacts associated with the project options to inform the decision making process (Section 2). To support the Guinevere Installation DP, the EIA process was conducted in accordance with the Offshore Petroleum Production and Pipelines (Assessment of Environmental Effects) Regulations 1999 (as amended). This document presents the findings of the EIA and has been prepared as part of the planning and consents process for the decommissioning Guinevere installation.
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Table 1-2: Key stages of the EIA process for decommissioning
EIA Stage Description Scoping Allows the study to establish the key issues, data requirements, and impacts to be addressed in the EIA and the framework or boundary of the study. Consideration of Demonstrates that other feasible approaches, including alternative project alternatives options, scales, processes, layouts, and operating conditions have been fully considered. Description of Provides clarification of the purpose of the project and an understanding of its project actions various characteristics, including stages of development, location and processes. Description of Establishes the current state of the environment on the basis of data from environmental literature and field surveys, and may involve discussions with the authorities and baseline other stakeholders. Identification of key Seeks to identify the nature and magnitude of identified change in the impacts and environment as a result of project activities and assesses the relative significance prediction of of the predicted impacts. significance Impact mitigation Outlines the measures that will be employed to avoid, reduce, remedy or and monitoring compensate for any significant impacts. Mitigation measures will be developed into a project environmental management plan. Aspects of the project which may give rise to significant impact which cannot be mitigated to an acceptable or tolerable level of impact may need to be redesigned. This stage will feed back into project development activities. Presentation of the Reporting of the EIA process through production of an EIA that clearly outlines Environmental the above processes. The EIA provides a means to communicate the Impact Assessment environmental considerations and environmental management plans associated with the project to the public and stakeholders. Monitoring Project impacts will be monitored during the projects activities and following cessation of any operations to verify that impact predictions are consistent with the subsequent outcomes.
1.4 Regulatory Context The decommissioning of offshore oil and gas infrastructure in the UKCS is principally governed by the Petroleum Act 1998, as amended by the Energy Act 2008. The Petroleum Act sets out the requirements for a formal DP which must be approved by BEIS before the owners of an offshore installation or pipeline may proceed. The Guidance Notes: Decommissioning of Offshore Oil and Gas Installations and Pipelines under the Petroleum Act 1998 (DECC, 2011), state the DP must be supported by an EIA. The Guidance Notes state that an EIA should include an assessment of the following: All potential impacts on the marine environment including: exposure of biota to contaminants associated with the decommissioning of the installation; other biological impacts arising from physical effects; conflicts with the conservation of species with the protection of their habitats, or with mariculture; and interference with other legitimate uses of the sea. All potential impacts on other environmental compartments, including emissions to the atmosphere. Consumption of natural resources and energy associated with reuse and recycling. Potential impacts on amenities, the activities of communities and on future users of the environment.
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In addition, BEIS have advised the Oil and Gas Industry that under the Marine and Coastal Access Act 2009 (MCAA), an EIA will be required for all licence applications relating to decommissioning operations. OSPAR Decision 98/3 (the Decision) sets out the United Kingdom’s (UK’s) international obligations on the decommissioning of offshore installations. The Decision prohibits the dumping and leaving wholly or partly in place of offshore installations. The topsides of all installations must be returned to shore, and all installations with a jacket weight of less than 10,000 tonnes must be completely removed for re-use, recycling or disposal on land. Any piles securing the jacket to the seabed should be cut below the natural seabed level at a depth that will ensure they remain covered. The depth of cutting is dependent upon the prevailing seabed conditions and currents (DECC, 2011). Further regulatory drivers relevant to the Guinevere decommissioning project are provided in Appendix A.
1.5 Consultations During preparation of this EIA, the views of the following organisations were solicited by an informal scoping letter and report on the 5th October 2017: BEIS; Centre for Environment, Fisheries and Aquaculture Science (CEFAS); Joint Nature Conservation Committee (JNCC); Ministry of Defence (MoD); National Federation of Fishermen's Organisation (NFFO).
The main issues raised during the informal consultation exercise, and how PUK has, or is proposing to address these are summarised in Table 1-3. A reference to the relevant section has been provided where the issues are discussed further within this EIA. Of note is that consultations and liaison with interested parties is a continuous part of PUK’s Safety and Environmental Management Systems (SEMS) and will continue throughout the Guinevere decommissioning project.
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Table 1-3: Summary of the consultation responses for the Guinevere decommissioning project
Consultee Summary of issues raised PUK’s response EIA section BEIS Mention should be made of PUK have assessed the impacts associated with the impact of jacket cutting these activities in this EIA. 7 and excavation of seabed sediment. The potential noise impact The impacts associated with vessel noise have from vessels should also be been assessed as part of a supporting technical 6 considered in the EIA. report and are also investigated in this EIA. The intent regarding the use PUK can clarify that explosives are to be used for of explosives should be the cutting of the tubing only. A description of clarified. PUK should use this method is included in this EIA. 3 and 6 alternative methods for the removal of the conductor and the casing PUK should be working to PUK are working to minimise the amount of rock minimise the amount of hard material to be introduced to the area. Rock will substrate material on soft only be used as stabilisation material where sediments. absolutely necessary. In the unlikely event that 7 rock is required for the stabilisation of vessels during decommissioning activities, this will be assessed in this EIA. Cefas No response. - - JNCC Full environmental survey Full survey results were received following the results should be included. distribution of the scoping report and are now Any Annex I habitats should included in this EIA. 3 be avoided as much as possible and BEIS/ JNCC should be notified. PUK should be working to PUK are working to minimise the amount of rock minimise the amount of hard material to be introduced to the area. Rock will substrate material as the only be used as stabilisation material where impact on sandy or muddy absolutely necessary. In the unlikely event that 7 seabeds is currently not fully rock is required for the stabilisation of vessels, understood. during decommissioning activities, this will be assessed in this EIA. PUK should be closely PUK have undertaken a noise analysis desk study following JNCC guidelines and are also undertaking surveys at the where explosives are to be Guinevere location (following JNCC guidelines) to 6 used during mitigate any impacts during detonation. The decommissioning results of this will be included within this EIA operations. MoD No comments. - - NFFO No response. - -
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1.6 Report Structure The structure for this Guinevere Installation EIA is detailed in Table 1-4. Table 1-4: Guinevere Installation EIA structure
Section Description Non-Technical A non-technical summary. Summary 1. Introduction An introduction to the project and the EIA scope. 2. Project Description A description of the decommissioning options and the recommended decommissioning option, as determined through a formal CA process. 3. Environmental A description of the environmentally sensitive receptors in the vicinity of the Description project area. Socio-economic? 4. Risk Assessment A detailed description of the risk assessment approach and findings. 5. Energy and Identification of potential sources of impact to environmental and societal Emissions receptors, cumulative and transboundary impacts, and details of practicable 6. Underwater Noise mitigation strategies. 7. Seabed Impact 8. Societal Impact 9. Accidental Events 10. Waste 11. Environmental A description of PUK’s environmental management procedures and how these Management will apply to the decommissioning of the Guinevere installation. This section also includes a register of commitments made within the EIA. 12. Conclusions Key findings and conclusions. References Sources of information used to inform the assessment. Appendix A: A summary of relevant environmental legislation. Legislation Appendix B: Non- A summary of the non-significant impacts. Significant Impacts Appendix C: Energy An outline of the conversion factors used to estimate energy use and gaseous Use and Atmospheric emissions. Emissions Supporting Information
1.6.1 Transboundary and Cumulative Impacts The EIA process also includes the identification of any potential cumulative and transboundary impacts that could be caused by the proposed DP. Cumulative impacts may occur as a result of a number of activities (e.g. discharges or emissions) combining or overlapping and potentially creating a new or larger impact. Even where impacts do not overlap, it is important to consider the incremental effect of many small areas of impact on a particular environment or its use. Transboundary impacts are those that could have an impact on the environment and resources beyond the boundary of UK waters. The Convention on Environmental Impact Assessment in a Transboundary Context (Espoo, 1991) addresses the need to enhance international co-operation in assessing transboundary environmental impacts. The Espoo Convention was a key step in bringing together all stakeholders to prevent environmental damage before it occurs.
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The EIA process assessed the transboundary and cumulative impacts of all installation-related decommissioning activities within assessment Sections 5 to 10 of this EIA document.
1.7 Contact Address Any questions, comments or requests for additional information regarding this EIA should be addressed to: Gail Nxumalo Environmental Lead Perenco UK Limited 3 Central Avenue St Andrews Business Park Norwich Norfolk NR7 0HR E-mail: [email protected] Telephone (Direct): +44 (0) 1603 771208 Switchboard: +44 (0) 1603 771000
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2 Project Description This section presents a description of the Guinevere installation, the scope of the decommissioning operations, components to be decommissioned and alternatives considered for decommissioning of this infrastructure, including the selected options and associated activities. At present, PUK has not finalised the contracts to carry out the offshore decommissioning activity, therefore some details of the exact methodology to be employed may be subject to future modification. Where this is a possibility, the impact assessment, as presented in this EIA, has been based on a worst-case assumption. Any changes to the decommissioning methodology should therefore only lead to a reduction in the likelihood or severity of any proposed environmental impact. 2.1 Overview of installation and materials to be decommissioned The infrastructure included within the scope of the Guinevere Installation DP and EIA and the location, status and relevant EIA section that details each component of this infrastructure, is summarised in Table 2- 1. Table 2-1: Infrastructure associated with the Guinevere Installation DP.
Latitude/ Longitude UKCS Current EIA Section Facility type Component (ED50) Block status Reference 53° 24' 53.4" N Topsides 48/17b Operational 01° 16' 25.3" E 2.1.1 Guinevere NUI Four legged Jacket 53° 24' 53.4" N 48/17b Operational 2.1.1 with four piles 01° 16' 25.3" E Wells 48/17b-G1 53° 24' 53.3" N 48/17b Plug and 01° 16' 25.1" E Abandon (P&A) 2.1.4 44/17b-G2 53° 24' 53.50" N 48/17b P&A 01° 16' 25.2" E
The Guinevere installation (Figure 2-1) is located in a water depth of 18.4 m (Lowest Astronomical Tide (LAT)) in UKCS Block 48/17b. An overview of the installation components to be decommissioned is provided in Table 2-2. Table 2-2: Guinevere platform information (PUK, 2015a)
Topsides / facilities Jacket and Jacket piles Facility type Total Number of Total lift Number of legs Number of piles weight (t) modules weight (t) Fixed platform (NUI) 818 1 806** 4 4 ** Jacket weight 509 Te plus estimated Marine Growth of 107 Te. Piles are 495 Te in total; however, 305 Te from 3.0m below mudline will be left in situ and 190 Te will be decommissioned, incl. 5 Te of concrete grout.
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Figure 2-1: Guinevere Installation (PUK, 2017a)
2.1.1 Topsides The Guinevere topside (Figure 2-2) is a conventional carbon steel structure with a cellar deck, mezzanine deck and weather deck. A helideck is situated at the same level as the weather deck. There are nine well slots on the drill floor of which two have been drilled. The size of the topsides is 31.6 m x 21m x 8 m high (including helideck).The total topsides weight is 818 tonnes (t). A breakdown of this weight by material is provided in Table 2-3.
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Figure 2-2. The Guinevere topsides and jacket layout (PUK, 2017a)
Table 2-3: Guinevere topsides materials inventory
Material Weight (t) Steel 803 Lead 4 Plastic 8 NORM/ Hazardous 3 Total weight (t) 818
2.1.2 Jacket The Guinevere jacket (Figure 2.1) is a conventional four-legged carbon steel structure, each with a single 48" tubular pile through the pile sleeve attached to each leg. The jacket has a single vertical face to facilitate approach of a jack-up rig and the three other faces have a batter. The total jacket height is 29 m and it is sitting in a water depth of 18.4 m LAT. The total jacket steel weight (including piles) is 999 t, comprising 509 t of steel in the jacket and 490 t of steel in the piles. During decommissioning activities, the piles will be cut at, approximately, 3 m below the seabed. As a result, 185 t of the pile steel will be removed
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GUINEVERE INSTALLATION DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT and 305 t will remain in the seabed. A total of 694 t of combined jacket and pile steel will therefore be removed during the decommissioning process. No significant scour was observed at the seabed around the jacket during the most recent site surveys (Bibby Hydromap, 2017a and 2017b). 2.1.2.1 Marine Growth The fully submerged and intermittently immersed parts of offshore man-made structures are frequently colonised by opportunistic marine organisms. These colonies are referred to as marine growth or fouling (Comber et al., 2002). Marine growth is considered a waste by-product from decommissioning offshore infrastructure. PUK estimate that approximately 107 t (wet weight) of marine growth may be attached to the Guinevere installation jacket (Table 2-3). During the decommissioning of the Guinevere installation, it is expected that while some limited quantities of marine growth will be removed offshore to facilitate access to key parts of the structure, the majority of the material will be removed at the onshore disposal yard. Data from previous decommissioning projects shows that the actual weight of marine growth received at the disposal yard is often much lower than the estimated wet weight (BMT Cordah, 2011). For example, during the decommissioning of seven individual gas platform jackets in the southern North Sea, 40 to 50 t of marine growth was expected per platform. However only around 7 t of material per platform were actually received, approximately 80 to 85% less than expected (BMT Cordah, 2011). This difference is primarily the result of the natural dehydration process that begins once marine growth is removed from the sea. The water content of marine growth is typically between 70 to 90% of its total weight (Tvedten, 2001) and depending on local weather conditions, the natural drying process can proceed quickly. Other losses of marine growth can occur as a result of removal and dislodgement during the cutting, lifting and transportation of infrastructure (BMT Cordah, 2011). Given the above, it is unlikely that the estimated 107 t (wet weight) of marine growth will be received by the disposal yard. For the purposes of this assessment, a conservative loss of 70% of the estimated wet weight will be assumed. Therefore, it is estimated that approximately, 32 t of marine growth will be landed with the Guinevere installation jacket. 2.1.3 Wells Guinevere has two platform wells, as listed in Table 2-4. Table 2-4: Guinevere platform wells (PUK, 2017a) Well identification number Well type Status 48/17b-G1 Gas Production P&A 48/17b-G2 Gas Production P&A
2.1.4 Drill Cuttings Pile Survey work carried out by Bibby HydroMap (2017a) found no evidence of cuttings piles on the seabed in the vicinity of the surveyed Guinevere wellheads. The dynamic marine environment present at the surveyed wellheads has led to the redistribution of drill cuttings from around the wellheads. Drill cuttings are therefore not required to be scrutinised under the OSPAR Recommendation 2006/5 Management Regime for Offshore Cuttings Piles. However, Total Hydrocarbon (THC) quantities are presented in Section 3.3.7.2. 2.1.5 Assessment of Alternative Use of the Guinevere Installation Regulations on the decommissioning of offshore structures were consolidated and strengthened in 1998 when the OSPAR (Oslo – Paris Convention) Contracting Parties agreed the OSPAR Decision 98/3 on the Disposal of Disused Offshore Installations. Under the terms of OSPAR Decision 98/3, which is implemented in the UK through the Petroleum Act 1998 and Energy Act 2008, there is a prohibition on the dumping and leaving, wholly or partly in place, of offshore installations.
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PUK has considered the feasible removal and disposal methods for the Guinevere installation in line with the Waste Hierarchy (Section 10.2), which gives priority to preparing waste for re-use, then recycling, then other forms of recovery (including for energy production) and last of all disposal (e.g. landfill) (DECC, 2011; Environment Agency (EA) 2017)). The re-use of an installation (or parts thereof) is first in the order of preferred decommissioning options. PUK therefore considered extending the producing life of the Guinevere installation, by utilising it as an infrastructure hub for third party tie backs and enhanced recovery programmes. An assessment of feasible options, however, found that neither was commercially viable. Following this, the option of relocating the Guinevere installation as a producing asset was considered, but it was concluded that due to Guinevere’s ageing process technology and the high cost of maintaining the fabric and structural integrity of the installation, no technically viable re-use option was available. With the option to re-use the Guinevere installation as a whole considered impractical, the installation must therefore be completely removed to shore for re-use, recycling or final disposal, taking into account all relevant regulatory requirements and PUK’s company policy. As the DP progresses, PUK is committed to continue to review the Guinevere installation’s equipment inventories to assess the potential for adding to their existing asset portfolio spares or for re-sale to the open market. In addition, PUK will continue to track market trends in order to seize re-use opportunities at the appropriate time. 2.2 Decommissioning Options This section outlines the available and chosen options for the decommissioning of the Guinevere installation. 2.2.1 Topsides PUK previously considered three options; (1) reverse installation multi-lifts; (2) piece small offshore deconstruction; and (3) single lift. It is proposed to scope out the piece small removal and the reverse installation options, these options are considerably costly and require more time at sea in comparison to the single lift option. Therefore, the preferred option for the removal of the platform topsides would be the single lift method. In the single lift option, a lift vessel capable of lifting the entire topsides in one lift will be utilised. The topsides would be prepared for this by a combination of engineering down and cleaning (EDC), module sea-fastening and structural strengthening. The topsides will then be transported to the designated disposal yard by lift vessel or cargo barge where they will be transferred to the quayside for dismantling. 2.2.2 Jacket As the weights (in air) of the jacket (Table 2-2) is <10,000 t, it falls within the OSPAR 98/3 category of steel structures for which derogation cannot be sought. Therefore, the only option available is complete removal of the installation. Complete removal will involve severing the risers, cutting the jacket piles to a 3 m below the natural seabed to ensure any remains are unlikely to become exposed and removal of the jacket and risers. The preferred method of cutting the piles is to use internal cuts, which will not require external dredging of the jacket legs. External cutting will only be undertaken in the event debris prohibits access within the jacket legs. However, the methodology is subject to contractor selection and thus yet to be confirmed. 2.2.3 Wells The wells have been P&A’d in accordance with HSE “Offshore Installations and Wells DCR 1996” and in accordance with OGUK Guidelines for the Suspension and Abandonment of Wells" (Issue 5, July 2015). 2.2.4 Drill Cuttings Drill cutting debris is widely dispersed, with no obvious drill cuttings piles around the installation. Drill cuttings are therefore not required to be scrutinised under the OSPAR Recommendation 2006/5 Management Regime for Offshore Cuttings Piles and will be left in situ to degrade naturally. 2.2.5 Summary of Preferred Decommissioning Options The preferred options for the Guinevere Installation DP are summarised in Table 2-5.
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Table 2-5: Summary of preferred options for the Guinevere Installation DP
Selected Infrastructure Justification for selection Key decommissioning activities option Complete removal by Decontaminate the topsides and single lift for To comply with OSPAR remove the topsides by single lift. reuse, Topside Decision 98/3 and maximise Re-use followed by recycle and then recycling or the recycling of materials. landfill will be the prioritised options final for the topsides. disposal onshore Complete To comply with OSPAR Piles will be severed at least three removal by Decision 98/3. metres below the seabed. single lift for Leaves clean seabed, removes Jacket legs will be removed and reuse, Jacket a potential obstruction to dismantled at an onshore location. recycling or fishing operations and final Re-use followed by recycle and then maximises the recycling of disposal landfill will be the prioritised options materials. onshore for the jacket. Wells have been Plugged and abandoned in compliance with HSE Meets Health, Safety and “Offshore Installations and Wells DCR Wells P&A Executive (HSE) and BEIS 1996” and in accordance with OGUK regulatory requirements. Guidelines for the Suspension and Abandonment of Wells" (Issue 5, July 2015).
2.3 Decommissioning Activities The main elements of the Guinevere installation’s decommissioning activities include the following: Arrival of the Seafox 1 jack-up unit for accommodation, construction, maintenance, and well services and positioning alongside the Guinevere NUI. P&A of wells from the Seafox 1 in accordance with a well abandonment programme (This is covered by a separate environmental assessment conducted for the Well P&A works). Final cleaning and preparation for removal of mobile hydrocarbons and chemicals from topsides (gas, methanol and corrosion inhibitor). Leaving Guinevere NUI in cold suspension with appropriate navigational aids until topside and jacket removal. Preparation of infrastructure for removal by specialist contractors to an approved onshore disposal facility. Removal of topsides infrastructure by Heavy Lift Vessel (HLV). Excavation and cutting of the jacket piles, 3 m below the seabed. Removal of jacket infrastructure by HLV. Removed infrastructure will be dismantled and recycled/ disposed of at a suitable onshore reception facility. Disposal yard selection remains to be made.
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Surveys to monitor the state of the seabed post-decommissioning. 2.3.1 Preparatory activities The initial decommissioning operations will be undertaken with the Seafox 1 jack-up accommodation drilling rig stationed alongside the unmanned Guinevere installation and bridge-linked during the P&A of the two wells and engineering down and cleaning (EDC) activities. As part of the EDC activities, a navigational aid will be placed on the topside decks of the installation. This will both enable clear sight and aid navigation. The Seafox 1 was deployed at this location previously and was positioned adjacent to the Guinevere installation with no requirement for rock stabilisation on the seabed. However, when the lift vessel is on location, PUK will assess the current seabed state by undertaking a debris survey to determine the requirement for rock-placement. If rock is required this will be to protect against: Punch-through, whereby the spud-cans suddenly penetrate through the seabed resulting in the uneven distribution of the vessels weight and ultimate destabilisation and/ or listing of the vessel. Hang-up, whereby the vessels spud-cans penetrate through the seabed to a depth which prevents the uniform removal of the four legs, resulting in the potential for the destabilisation of the vessel or the lowering of the vessel within the water below safe depths and possible capsize. The use of rock-placement is not currently considered as a likely requirement. However, should it be required a variation to the marine licence will be submitted to BEIS to seek approval to commence the rock-placement operations at the installation. 2.3.2 Vessels Details pertaining to those vessels expected to be used during the process of decommissioning the Guinevere installation is provided in Table 2-6. A small quantity of atmospheric emissions will result from combustion of fuel for power generation on the decommissioning vessels. The impacts of energy use and atmospheric emissions on the environment are addressed in Section 5. Table 2-6: Summary of vessels expected to be used during Guinevere decommissioning activities.
Approximate duration (working days) Vessel Type Jacket and Topsides Accommodation barge (Seafox 1) 70 Supply vessel for barge 70 Stand-by vessel for barge 70 HLV 24 Supply vessel for HLV 24 Cargo barge 24 Tugs x3 42 Stand-by vessel for HLV 24 Survey vessel 2 Helicopter 94 2.3.3 Topsides PUK will purge the topside systems to ensure that minimal hydrocarbons remain in the system prior to the final cleaning and disconnect (FC&D). During the FC&D works, all the systems will be progressively depressurised, purged and rendered safe for removal operations. Pipework and tanks may then be cleaned to remove sources of potential spills of oils and other fluids. Table 2-7 outlines how this will be done.
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Table 2-7: Cleaning of topsides prior to removal (PUK, 2017a)
Material type Detail Preparatory activity On-board Flushed and drained to container on Process fluids, fuels and lubricants hydrocarbons Guinevere NUI Other hazardous NORM, instruments containing Transported ashore for re-use/disposal by materials heavy metals, batteries appropriate methods May give off toxic fumes/dust if flame- Original paint Lead-based paints cutting or grinding/blasting is used so coating appropriate safety measures will be taken Asbestos and Appropriate control and management will - ceramic fibre be enforced Note: Naturally Occurring Radioactive Materials (NORM)
PUK proposes that the topsides will be removed as a complete unit by HLV or a combination of crane vessel and piece small dismantling and transported to shore for appropriate re-use of selected equipment, recycling, break up and/or disposal. The installation’s equipment inventory will be assessed for use as spares for PUK’s asset portfolio. Please note that the Guinevere diesel generators will not be used during the DP operations. Power will be sourced from the Seafox 1 while on location. NORM is present within the Earth’s crust and can be concentrated and enhanced by oil and gas recovery as it may be present in drilling sludges, muds and pipe scale and accumulate in dead spaces in equipment over time (OGP, 2008). During decommissioning, PUK will ensure that this material is disposed of separately. Any NORM-contaminated (or other hazardous material) material returned to shore will be treated, recycled or disposed of as appropriate in line with the permit requirements for Guinevere. 2.3.4 Jacket The planned, high-level process for the jacket removal is: Completion of the installation removal preparations; Cutting of the risers; Remove soil plug from leg piles; Cutting of the jacket piles to a suitable depth below the natural seabed level using abrasives (depth to be determined based on prevailing hydrodynamic conditions, currently estimated at 3 m); Structural strengthening of the jacket if required; Lift vessel (single lift) removal of the jacket (including risers); and Transportation by the lift vessel or cargo barge to the quayside for cleaning and disposal. Marine growth will be fully dried at a disposal yard in the Netherlands, following which it will be sent to a recycling facility.
2.3.5 Wells Drilling and completion fluids produced recovered from the wells as a result of the decommissioning activities were dealt with in accordance with The Offshore Chemicals Regulations 2002, as were other chemicals used in the abandonment procedure. Chemicals recovered from the well annuli included calcium chloride completion brine and oil based mud. All recovered well fluids and chemicals were transported to shore by vessel for subsequent treatment and disposal. There was zero discharge of these annular fluids to the marine environment.
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The abandonment of the wells was conducted in accordance with the UK legislation and industry guidelines listed below: Offshore Installations and Wells (Design and Construction) Regulations 1996. Offshore Installations (Safety Case) Regulations 2005 (SI 2005/ 3117). Oil and Gas UK Guidelines for Suspension and Abandonment of Wells, Issue 4, July 2012.
A well abandonment application (known as a PON5)1 and a Chemical Permit Subsidiary Application Template 2(SAT) under a Well Intervention Operations Application (WIA) Master Application Template (MAT), was submitted via the UK Oil Portal and approved in advance of the well abandonment operations. Well decommissioning involved flushing and cleaning the wells and placing mechanical plugs and cement barriers in the well bore and cutting the wells at the appropriate depths using explosives, according to the specific features of each well / reservoir. The production tubing was recovered from each well and required to be cut using an explosive charge, the depth of the cuts were 2,396m in G1 and 2,725m in G2. One explosive charge per well was used for cutting the tubing. Explosives were also required to perforate the production casing to create a circulation path required for the placement of the cement plugs. Perforations were made at 244m in G1 and 305m in G2. Each explosive charge used in the wells was detonated one at a time. The charge sat inside the tubing and/or casing, which was encased by the outer production casings, which ran from the depth of the explosion to the platform deck. The tubing and inner casing strings were fully contained within the outer casing. At no time before or after the cut were the charges open to the sea. The quantity and the fate of the fluids associated with the P&A of the two Guinevere wells is provided in Table 2-11. The wellheads were removed following the well P&A. 2.3.6 Summary of the Expected Wastes The wastes that are expected to be generated by the proposed decommissioning methods discussed above for the Guinevere installation are summarised in Table 2-8. The significant environmental impacts associated with the removal of this material and leaving the remainder in situ are addressed in Sections 5 to 10 of this EIA. PUK’s approach to dealing with the proportion of the waste that is to be shipped to shore is outlined in Section 10.
Table 2-8: Summary of the expected wastes that will be generated by the Guinevere decommissioning
Estimated solid waste quantity Leave / in situ (t) Ship to shore (t) Solid waste (t) Topside Jacket Steel 803 998 305 1,496 Plastic 8 0 0 8 Concrete 0 5 0 5 Lead 4 0 0 4 Marine growth 0 32 0 32 NORM / hazardous 3 1 0 4 Solid waste total (t) 818 1,036 305 1,549
1 WONS applications - 48/17b-5 (G1): WONS/10236/0/AB3/1 Version 1; 48/17b-G2: WONS/10237/0/AB3/1 Version 2 Chemical Permit - CP/1262/1
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Reinject Ship to Liquid waste Estimated liquid waste quantity in barrels (bbl) into Well shore G2 (bbl) (bbl) Sodium Chloride (NaCl) Brine 988 (505 (G1 well); 483 (G2 well)) 505 483 Water-based mud (WBM) 80 (G2 well) - 80 Oil-based Mud (OBM) 204 (G1 well) - 204 Liquid waste total (bbl) 1,272 505 767
Materials will be segregated for ease of handling and to reduce the energy used when transporting different materials to their respective recycling, reuse or disposal facilities. PUK will ensure that all waste is handled in a manner that will minimise the threat to personnel and the environment (see Section 10 for further information).
2.3.7 Post-decommissioning surveys Several surveys will be carried out following decommissioning activities to make sure the seabed is clear of debris, to ensure overtrawlability and to assess the environmental impacts of decommissioning (if any). 2.3.7.1 Debris Clearance and Overtrawlability Survey A post-decommissioning site survey will be carried out within a 500 m radius area around the Guinevere NUI site. Significant seabed debris will be recovered and transported to shore for disposal or recycling in line with existing disposal methods. To ensure safety for fishing activity in the area, independent verification of the seabed state will be obtained by over-trawling the platform area. This will be followed by a statement of clearance to all relevant governmental departments and non-governmental organisations (NGO). 2.3.7.2 Environmental Seabed Survey A post-decommissioning environmental seabed survey, centred on the installation, will also be carried out. The survey will focus on the assessment of the physical and chemical impacts of decommissioning and will be compared to the findings of the pre-decommissioning environmental baseline survey. 2.3.7.3 Ongoing Monitoring and Evaluation With any materials left in situ following decommissioning, the Operator has a liability to monitor and mitigate any impacts from these materials. After the initial post-decommissioning site survey reports have been sent to BEIS and reviewed, a post-monitoring survey regime will be agreed by both parties if this is deemed necessary.
2.4 Decommissioning Programme Schedule It is currently envisaged that the decommissioning activities at Guinevere will last for a period of up to four years. The proposed project schedule for the Guinevere DP is provided in Table 2-9.
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Table 2-9: Outline of the proposed schedule for the Guinevere DP
Year 2017 2018 2019 2020 2021 2022 Quarter 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 HC Free Pre-engineering / Planning Develop Decom Programme & EIA Decom Programme Preperation & Consultation Approval of instalation DP Drifting tubing, setting bridge plugs in wells Pipeline pigging Jack-up barge arrival Well rig-less P&A Purge topeside and leave installation black Verify hydrocarbon free Dismantling Pre-engineering / Planning HLV arrival Topesides and jacket removed Site clearance Approval of completion Contingency
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3 ENVIRONMENTAL BASELINE This section describes the baseline environmental setting of the proposed area to be decommissioned and identifies those components of the physical, chemical and biological environments that might be sensitive to the potential impacts arising as a result of the proposed activities. An understanding of the environmental sensitivities at the local and regional level informs this assessment of the environmental and societal impacts and risks associated with decommissioning activities. Although this EIA is focussed on the impact assessment of the decommissioning of the Guinevere installation, this section covers all of the Guinevere infrastructure and therefore represents a worst-case scenario. 3.1 Overview The Guinevere infrastructure to be decommissioned is located in UKCS Blocks 48/17a (export pipeline from Guinevere Field to Lancelot Field) and Block 48/17b (platform and associated infrastructure), in the southern North Sea. The Guinevere NUI is located in the Guinevere Field in Block 48/17b, approximately 53 km north from the Norfolk coast and 116 km from UK/ Netherlands median line (Figure 1.2). The water depth at the installation is 18.4 m (Lowest Astronomical Tide (LAT)). 3.2 Environmental Surveys The environmental baseline information contained within this EIA has been informed in-part using an Environmental Baseline Survey report (EBS; Section 3.2.1) and bathymetry survey report (Section 3.2.2) specific to the Guinevere facilities area (Bibby HydroMap, 2017a and 2017b, respectively).
3.2.1 Bibby HydroMap (2017a) Environmental Baseline Survey The objective of this work was to establish the environmental baseline conditions of the seabed to support decommissioning operations at the Guinevere installation’s location. Environmental survey equipment was used to ground-truth seabed conditions at 13 stations across the survey area. A cruciform sampling strategy (ten stations) was used to acquire samples around the Guinevere installation. Three further stations were sampled along the pipeline route to cover any areas of interest (exposures, bathymetric depressions, etc.), areas of changing reflectivity (seabed bedforms, patches of cobbles and boulders) or spacing along the routes. Sampling was based on the acquisition of four replicate samples using a 0.1m2 Day Grab designed for use in sandy sediments and a 0.1m2 Hamon Grab for coarser sediments (Bibby HydroMap, 2017a). The locations of the sampling stations are provided in Table 3-1 and Figure 3-1.
The survey’s scope of work was to:
Assess the status/ diversity of benthic habitats in the vicinity of the Guinevere installation and along the pipeline corridor;
Provide data on the chemical and physical properties of the sediments in this area;
Provide high resolution still images and corresponding video footage at specific points in a cruciform pattern around the installation and at nominal 3 km intervals along the pipeline corridor; and
Provide sufficient benthic data to establish a baseline against which the environmental impact of the future decommissioning operations can be assessed.
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Table 3-1 Summary of the environmental sampling positions and samples acquired during the EBS
Station Distance (m) and direction from Guinevere NUI Easting Northing
1 100 SE 385323.7 5919860 2 600 SE 385649.1 5919481 3 1600 SE 386299.9 5918722 4 30 SW 385222.6 5919918 5 250 SW 385072.8 5919769 6 100 NW 385191.7 5930010 7 500 NW 384924 5920308 8 1000 NW 384589.5 5920679 9 100 NE 385332.9 5920003 10 250 NE 385444.4 5920103 11 PL0874_01* 387001 5919693 12 PL0874_02* 389756.6 5919409 13 PL0874_03* 390952.4 5919287 *Sampled at locations of interest identified from SSS along pipeline route (Figure 3-1). Source: Bibby Hydromap (2017a)
3.2.2 Bibby HydroMap (2017b) Bathymetric and Debris Survey The objective of the geophysical survey was to acquire information on surficial and sub-seabed conditions at the proposed well location to ensure the safe, secure and efficient installation and operation of a jack-up rig. Bibby HydroMap surveyed the well location using multi-beam echo sounders (MBES), sub-bottom profiling (pinger and sparker) and side scan sonar (SSS). The acoustic data was used as a basis for the identification of the 13 sampling stations analysed as part of the EBS (Table 3-1; Section 3.2.1). Camera transects were also collected during the SSS survey. The extent of the survey area is illustrated in Figure 3-1.
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Figure 3-1: Location of the Bibby HydroMap bathymetric survey and EBS sampling stations (Bibby HydroMap, 2017a)
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3.3 Physical and Chemical Environment Characteristics of the bathymetry, currents, meteorology, sea temperature, salinity and seabed sediments in the area around the Guinevere NUI are described in the following subsections. 3.3.1 Bathymetry A review of the available acoustic data revealed a generally uniform seabed at a depth of 16.8 m to 18.3 m below LAT with rippled sand occurring across the entire survey area (Figure 3-1). This was supported by the debris survey which reported mostly featureless sands with sporadic boulders and areas of megaripples with wavelength between 4 m and 11 m and heights less than 0.5 m (Bibby HydroMap, 2017a). 3.3.2 Currents, waves and tides The Guinevere infrastructure is located in an area influenced by the southern North Sea current and the English Channel current. The cyclonic, counter current created from the ingress of water through the channel drives the near surface current towards a more easterly direction. The shallower waters of the southern North Sea remain permanently mixed throughout the year due to the influence of tidal currents (OSPAR, 2000). Tidal current velocities over the Guinevere area are between 0.25 to 0.50 m/s (neap tides) and 0.50 to 0.75 m/s (spring tides) (ABPmer, 2016). Annual wave height recorded for the Guinevere location is in the range of 1.26 to 1.50 m, however, there is considerable seasonal variation with summer wave height at 0.76 to 1.25 m and winter wave height is higher at 1.51 to 2.00 m (ABPmer, 2016). 3.3.3 Meteorology Regional assessments indicate that the annual wind speeds in the vicinity of the Guinevere facilities are 9.0 to 9.5 m/s, with seasonal variability ranging such that winter wind speeds are as much as 12.0 m/s (ABPmer, 2016). Along the coast, offshore winds prevail from the southwest/ west and are typically less than 7.5 m/s. Onshore winds originating from the northeast are stronger (often greater than 13.9 m/s), however, they are less frequent than those from the offshore area (Montreuil and Bullard, 2011). The wind regime has the potential to greatly influence the tidal regime through the generation of storm surges. These may be generated through either changes in atmospheric pressure and/ or increased wind stress upon the sea surface. During storm surge events in the SNS, current speeds will increase with subsequent increases in sediment transport (Heaps, 1983). During a typical 1 m surge, there can be a doubling of normal current speeds accompanied with a 10-fold increase in suspended sediment transport rates (HR Wallingford, 2002). 3.3.4 Sea temperature and salinity Sea temperature and salinity affects both the seawater properties and the fate of spills or discharges into the marine environment. Generally, areas south of 54º N remain vertically mixed all year round with little evidence of thermal stratification often observed in the deeper water to the north. This is a result of the shallower water in the southern North Sea being susceptible to tidal stirring which is sufficient to overcome the inputs of thermal energy. Due to the mixing at these shallow depths there is little variation in salinity with depth (Lee and Ramster, 1981). Mean sea surface temperature across the Guinevere area is around 14.5 to 15°C in summer and 5.0 to 5.5°C in winter. Mean bottom sea temperature is, approximately, 14 to 15°C in summer and 5 to 6°C in winter. (UKDMAP, 1998). The mean sea surface salinity across the Guinevere area during summer and winter is around 34.50 ppt. In summer, the mean seabed salinity is around 34.40 ppt, increasing in winter to between 34.40 and 34.60 ppt (UKDMAP, 1998). 3.3.5 Suspended sediments Suspended sediment concentrations within the water column are directly related to the volume of material available for suspension, and the strength of the metocean (wave and tide) regime for the mobilisation and
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The dominant sediment type throughout the Guinevere pre-decommissioning environmental survey area was interpreted to be Sand (S), with some stations falling into the gravelly Sand (g(S)) and sandy Gravel ((s)G) categories, according to the Folk classification (Folk, 1954; Table 3-2). Fine (muddy) sediments were very scarce in the area (mean 0.38% ± 0.82SD), being virtually absent in all the grab locations with the exception of the four stations (i) 600m SE, (ii) 250m NE, (iii) PL874/02 and (iv) PL874/03. The high percentage of stations with an absence of fine material (Table 3-2) suggests a high energy environment within the survey area (Bibby HydroMap, 2017a).
According to the Wentworth classification (Table 3-2) most samples peaked around the sand (Փ -1.0 to 4.0) fractions with seven stations also exhibiting peaks for the coarsest fractions (Փ <-1.0). The mean particle sizes for sampling stations (Table 3-2), show some major variations in the sediment composition throughout the Guinevere survey area. There appeared to be a geographical pattern of distribution of sands and gravels throughout the PL874 pipeline survey area, with increasing proportions of gravel and decreasing proportions of sand further away from the installation (Bibby HydroMap, 2017a).
A review of the sediment types from seabed photography and video has further confirmed sand dominance around the installation, with current-related bedforms, such as sand ripples and megaripples, evident across much of the survey area (Bibby HydroMap, 2017b).
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Table 3-2 Summary of surface particle size distribution
Wentworth Folk Phi Station Mean sediment size (mm) classification Sorting Fines (%) Sands (%) Gravel (%) classification (Փ) category category 100 SE 0.29 1.79 Medium sand Moderately well sorted 0.00 98.28 1.72 Sand 600 SE 4.75 -2.25 Pebble Very poorly sorted 1.57 39.01 59.42 sandy Gravel 1600 SE 0.27 1.89 Medium sand Moderately well sorted 0.00 99.26 0.74 Sand 30 SW 1.22 -0.29 Very coarse sand Very poorly sorted 0.00 61.28 38.72 sandy Gravel 250 SW 0.28 1.82 Medium sand Moderately well sorted 0.00 96.84 3.16 Sand 100 NW 0.28 1.86 Medium sand Moderately well sorted 0.00 98.42 1.58 Sand 500 NW 0.41 1.29 Medium sand Very poorly sorted 0.00 86.69 13.31 gravelly Sand 1000 NW 0.53 0.92 Coarse sand Very poorly sorted 0.00 83.53 16.47 gravelly Sand 100 NE 1.32 -0.40 Very coarse sand Very poorly sorted 0.00 58.48 41.52 sandy Gravel 250 NE 7.17 -2.84 Pebble Extremely poorly sorted 0.50 47.79 51.71 sandy Gravel PL0874/01* 0.39 1.37 Medium sand Moderately well sorted 0.00 100.00 0.00 Sand PL0874/02* 0.75 0.42 Coarse sand Very poorly sorted 0.17 80.06 19.77 gravelly Sand PL0874/03* 1.41 -0.50 Very coarse sand Very poorly sorted 2.70 49.88 47.43 sandy Gravel Mean 1.47 0.39 - - 1.88 0.38 76.89 - StDev 2.1 1.58 - - 1.15 0.82 22.54 - Variance (%) 402.3 - - 142.91 - 61.05 216.96 29.32 3 Source: Bibby HydroMap, (2017a)
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3.3.7 Sediment chemistry A summary of the organic carbon and hydrocarbon concentrations in the sediment around the Guinevere installation is provided in Table 3-3. Table 3-3 Summary of organic and inorganic chemical analyses
Station Total Organic Carbon THC Total n- alkanes Total PAHs (% w/w) (µg.kg-1) (µg.g-1) (µg.g-1)
100 SE <0.1 2.19 132.00 47.00 600 SE <0.1 2.65 149.00 48.00 1600 SE <0.1 3.19 167.00 42.00 30 SW 0.29 3.75 215.00 45.00 250 SW <0.1 3.51 244.00 62.00 100 NW <0.1 2.34 132.00 55.00 500 NW <0.1 3.63 253.00 76.00 1000 NW <0.1 3.76 263.00 58.00 100 NE <0.1 4.54 265.00 93.00 250 NE <0.1 3.67 203.00 57.00 PL0874/01* <0.1 2.49 188.00 62.00 PL0874/02* <0.1 9.75 761.00 205.00 PL0874/03* <0.1 6.42 278.00 108.00 Mean 0.07 3.99 250.14 73.59 StDev 0.07 2.05 161.96 43.88 Variance (%) 97.23 51.45 64.75 59.63 Source: Bibby HydroMap, (2017a)
3.3.7.1 Organic Chemistry Organic matter in marine sediments is primarily made up of detrital matter and naphthenic materials (carboxylic acids and humic substances and a small proportion of biological biomass). The results of the total organic carbon (TOC) analysis undertaken during the EBS are presented in Table 3-3 (Bibby HydroMap, 2017a). TOC represents the proportion of biological material and organic detritus within the substrate. The TOC results were below the detection limit throughout the Guinevere environmental survey area (less than 0.10%), with the exception of Station 30 SW, where the TOC was 0.29%. This reflects an organically- deprived environment and a possible influence of the installation on the immediate surrounding sediment. The low TOC level could also be the result of the dynamic nature of the seabed. TOC in surface sediments is an important source of food for benthic fauna (Snelgrove and Butman, 1994), although an overabundance may lead to reductions in species richness and number of individuals due to oxygen depletion. Increases in TOC may also reflect increases in both, physical factors (i.e. fines) and common co-varying environmental factors through elevated adsorption on increased sediment surface areas (Thompson and Lowe, 2004). A general lack of fine material and therefore reduced surface area for adsorption means that overall, TOC levels within the sediment are low. This may in turn affect the richness and abundance of deposit-feeding organisms within the sediment (Bibby HydroMap, 2017b).
3.3.7.2 Hydrocarbons The total hydrocarbon (THC) results showed generally low levels ranging from 2.19 µg.g-1 to 4.54 µg.g-1, near the Guinevere installation and higher concentrations of 9.75 µg.g-1 and 6.42 µg.g-1 recorded along the pipeline at stations PL874_02 and PL874_03 respectively (Table 3-3). The mean THC for the Guinevere survey (including the pipeline) was 3.99 µg.g-1 (±2.05SD; Bibby HydroMap, 2017a). The mean background THC levels for surface sediments recorded for stations located over 5 km from oil and gas platforms from the southern North Sea were estimated by UKOOA (2001) to be 4.34 µg.g-1, with an upper 95th percentile concentration of 11.39 µg.g-1 f. Whilst the THC concentrations at stations PL874/02 and PL874/03 were slightly elevated above typical background levels for the southern North Sea (UKOOA, 2001), higher
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Total polycyclic aromatic hydrocarbon (PAH) concentrations were variable but low, ranging from unrecorded to 205 µg.g-1 (mean 73.59 µg.g-1±43.88 SD; Table 3-3). The highest levels again recorded along the PL874 pipeline, with slightly elevated concentrations at stations PL874/02 (205 µg.g-1) and PL874/03 (108 µg.g-1). The highest concentration recorded close to the Guinevere NUI was found at station 100 m NE (93 µg.g-1). All PAH concentrations, except for station PL874/02, recorded during the survey fell within typically expected mean concentrations (111 µg.g-1) for sediments at background stations in the southern sector of the North Sea as reported in UKOOA (2001). However, the elevated level found at PL874/02 was still well below the 95th percentile concentration (366 µg.g-1) for stations located over 5 km from oil and gas platforms (UKOOA, 2001). The overall low PAH levels indicate that these are representative of low background concentrations, likely relating to shipping activity and the high density of oil and gas installations within the area (Bibby HydroMap, 2017a).
3.3.7.3 Heavy metals The analysis of heavy metals amongst the priority stations (Table 3-4) showed fairly consistent results between stations in the vicinity (less than 100 m) of the wellhead. With the exception of arsenic, all metal concentrations were well below the ‘effects range-low’ threshold (ERL - lowest concentration of a metal that can produce a harmful effect in 10% of reviewed data). However, arsenic levels were significantly lower than the ‘effects range-median’ (ERM - level at which half of the studies reported harmful effects) of 70 mg/kg (Long et al., 1995). Barium is of particular relevance to the offshore oil and gas industry as this metal is often associated with drilling mud discharges around offshore installations. Close to the Guinevere installation, bioavailable barium was highest (54 mg/kg) at the station 100 m NE of the Guinevere installation, along with elevated levels of most other metals at this location (Bibby HydroMap, 2017a). However, the levels recorded were not sufficiently high as to indicate contamination from drill cuttings. A fusion technique was further applied to measure total barium concentrations, but all concentrations within the priority samples were below the mean background concentration of 218.4 mg/kg reported for the southern North Sea (UKOOA, 2001).
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Table 3-4 Summary of organic and inorganic chemical analyses
Station
Arsenic (AS) Cadmium (Cd) Chromium (Cr) Copper (Cu) Lead (Pb) Mercury (Hg) Nickel (Ni) Vanadium (V) Zinc (Zn) Aluminium (Al Iron (Fe) Barium (Ba) (Sn)Tin 100 SE 9.00 <0.1 6.30 7.00 6.40 0.02 4.40 14.60 17.40 2,510.00 8,170.00 23.00 <0.5 600 SE 10.50 <0.1 5.80 6.30 6.70 0.01 3.40 14.50 13.90 1,830.00 7,410.00 25.00 <0.5 1600 SE 9.50 <0.1 5.30 5.50 6.70 0.01 3.10 13.50 14.00 1,360.00 6,810.00 17.00 <0.5 30 SW 10.00 <0.1 5.50 6.10 6.70 0.02 3.20 14.40 14.80 1,400.00 7,280.00 21.00 <0.5 250 SW 8.60 <0.1 4.80 5.60 5.80 0.01 2.90 12.90 12.10 1,120.00 6,640.00 15.00 <0.5 100 NW 9.10 <0.1 5.10 6.00 6.20 0.01 3.10 13.40 14.30 1,220.00 6,930.00 17.00 <0.5 500 NW 9.20 <0.1 5.30 5.40 6.50 <0.01 3.20 13.70 13.80 1,370.00 7,030.00 21.00 <0.5 1000 NW 6.40 <0.1 5.00 6.00 5.40 0.01 2.60 10.80 12.70 1,340.00 6,100.00 27.00 <0.5 100 NE 11.90 <0.1 10.00 7.40 6.50 0.01 10.60 23.00 23.20 3,450.00 25,600.00 54.00 <0.5 250 NE 8.60 <0.1 5.50 6.60 6.00 <0.01 3.20 12.00 12.50 1,220.00 7,220.00 18.00 <0.5 PL0874/01* 16.70 <0.1 5.60 5.50 7.10 <0.01 3.80 16.70 16.20 1,490.00 9,160.00 13.00 <0.5 PL0874/02* 13.20 <0.1 10.40 8.90 8.20 0.01 10.10 25.50 29.20 3,870.00 16,000.00 54.00 <0.5 PL0874/03* 10.60 0.10 23.20 12.30 6.60 <0.01 28.40 35.40 28.70 10,700.00 19,900.00 78.00 0.50 Mean 10.25 0.05 7.52 6.82 6.52 0.01 6.31 16.95 17.14 2,529.23 10,326.90 29.33 0.27 StDev 2.55 0.01 5.05 1.91 0.67 0.01 7.15 6.96 5.98 2,610.73 6,169.76 19.81 0.07 Variance (%) 24.88 25.75 67.13 28.06 10.31 50.00 113.42 41.08 34.86 103.22 59.74 67.53 25.75 ERL * 8.20 1.20 81.00 34.00 47.00 0.10 21.00 n/a 150.00 n/a n/a n/a n/a Source: Bibby HydroMap, (2017a). n/a: not available. Note: where levels were below the detection limit, a value of half the detection limit was applied in the calculations. *Effects Range Low (ERL) Lowest concentration of metal that can produce a harmful affect (Long et al., 1995).
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3.4 Biological Environment This section summarises the characteristics of plankton, benthos, finfish and shellfish spawning and nursery grounds, marine mammals, seabirds and offshore conservation areas relevant to the Guinevere area. 3.4.1 Plankton Plankton are defined as small plants (phytoplankton) and animals (zooplankton), which live freely in the water column and move passively with the water currents (Lawrence, 2000). Plankton forms a fundamental link in the food chain and vary seasonally in community structure according to temperature, water column mixing and nutrient availability. The southern North Sea is characterised by shallow, well-mixed waters, which undergo large seasonal temperature variations (JNCC, 2004). The region is dynamic with considerable tidal mixing and nutrient-rich run-off from the land (eutrophication). Under these conditions, there is consistent nutrient availability throughout the year and organisms, such as diatoms, are particularly successful (Margalef 1973, after Leterme et al. 2006). However, the phytoplankton community in the Regional Sea 2 area is dominated by the dinoflagellate genus Ceratium (C. fusus, C. furca, C. lineatum), along with higher numbers of the diatom, Chaetoceros (subgenera Hyalochaete and Phaeoceros) than are typically found in the northern North Sea (DECC, 2001). The zooplankton community is dominated by copepods including Calanus helgolandicus, C. finmarchicus, Paracalanus and Pseudocalanus spp., Acartia spp., Temora spp. and cladocerans such as Evadne spp. (BEIS, 2016a). However, there has been a marked decrease in copepod abundance in the southern North Sea, which has been linked to changes in global weather phenomena (BEIS, 2016a). The planktonic assemblage in the vicinity of the Guinevere facilities is not considered unusual. 3.4.2 Benthic fauna An understanding of the composition of the seabed (benthic) faunal communities can facilitate in the assessment of the impacts of a proposed oil and gas activity, such as the decommissioning of the Guinevere infrastructure. Benthic fauna comprises species that live either within the seabed sediment (infauna) or on its surface (epifauna). Infaunal and epifaunal species are particularly vulnerable to external influences which alter the physical, chemical or biological characteristics of the sediment. These organisms are largely sedentary and thus unable to avoid unfavourable conditions. Colonisation of sediments by different species is largely dependent on the type of sediment present and its characteristics. Physical and biological factors including seabed depth, water movements, salinity, temperature and available oxygen are important in determining species abundance and distribution. The species composition and relative abundance in a particular location provides a reflection of the immediate environment, both current and historical (Clark et al., 1997), as every benthic species has its own response and degree of adaptability to changes in the physical and chemical environment. Therefore, determination of sediment characteristics is of particular importance in the interpretation of benthic environmental survey data. The European Nature Information System (EUNIS) indicates the Guinevere area habitat type as A5.25 or A5.26 deep circalittoral sand. These habitat types are typically made up of clean fine sands or non-cohesive circalittoral muddy sands with silt content, respectively. The habitats may also extend offshore and are generally found in water depths of over 15 to 20 m. These habitats are characterised by a wide range of echinoderms (in some areas including the pea urchin (Echinocyamus pusillus)), polychaetes and bivalves. These circalittoral habitats tend to be more stable than their infralittoral counterparts and as such support a richer infaunal community (EUNIS, 2017). Following the EBS for the Guinevere area, a total of 451 individuals were recorded from 26 samples, representing 89 taxa (Bibby HydroMap, 2017a). Sixty of the 89 taxa were infaunal and the remaining 29 were epifaunal. Annelida, predominantly polychaetes, were the most diverse with 21 taxa accounting for 24.9% of the total individuals. The crustaceans were represented by 16 species (51.8%), the molluscs by 14 species (18.2% of total individuals) and the echinoderms by three species (1.6% of total individuals), whilst all other
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Figure 3-2: Proportion of individual abundance by main taxonomic group for each station (Bibby HydroMap, 2017a)
Figure 3-3: Proportion of individual richness by main taxonomic group for each station (Bibby HydroMap, 2017a)
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The macrofauna throughout the Guinevere survey area showed some small-scale variability in terms of abundance, richness and species composition associated with the sediment composition across the survey area. The infaunal community was dominated by annelids followed by crustaceans and molluscs in terms of species richness, however crustaceans were the dominant group with regard to individual abundance as shown in Figure 3-2 and Figure 3-3. The macrofauna abundance was dominated by crustaceans followed by annelids and molluscs (Bibby HydroMap, 2017a).
A measure of the overall dominance pattern in the sampling area was achieved by ranking the top 10 species per sample replicate according to abundance, giving a rank score of 10 to the most abundant species, decreasing to one for the tenth most abundant species, and summing these scores for all 26 samples to provide an overall dominance score (Eleftheriou and Basford, 1989) for each species. The rank dominance calculation revealed some homogeneity within the Guinevere survey area, resulting in eight of the highest numerically ranked species also to be found in the top 10 overall rank. This dominance was shown in both abundance and richness, with five crustaceans recorded in the top 10 ranked species followed by three annelids and two molluscs. The most abundant 15 species are given in Table 3-5. In overall rank order, the top 10 dominant species throughout the Guinevere survey area were the amphipod Urothoe elegans followed by the bivalve Abra alba, the polychaete Nephtys cirrosa and a further two crustaceans, Bathyporeia guilliamsoniana and Abludomelita obtusata. The polychaete Sabellaria alveolata was ranked sixth while Bathyporeia tenuipes and Nebalia bipes were ranked eighth and ninth, only separated by the slipper limpet Crepidula fornicata on rank seven. The 10th overall ranked species was the polychaete worm, Ophelia limacine (Bibby HydroMap, 2017a).
Of these species, the honeycomb worm, Sabillaria alveolata is protected under the Habitats Directive (Annex I) where it forms reef structures. However, no reef-like structures were noted during this survey (Bibby HydroMap, 2017a).
Table 3-5 Overall species ranking (Top 15 species)
Overall Species/ Taxon Total rank score Phylum Numerical Numerical top 15 (out of 260) abundance top 15 rank rank (26 replicates) 1 Urothoe elegans 139 Crustacea 113 1 2 Abra alba 122 Mollusca 42 3 3 Nephtys cirrosa 107 Annelida 23 4 4 Bathyporeia 88 Crustacea 50 2 guilliamsoniana 5 Abludomelita 68 Crustacea 18 5 obtusata 6 Sabellaria alveolata 65 Annelida 15 7 7 Crepidula fornicata 57 Mollusca 11 8 8 Bathyporeia tenuipes 54 Crustacea 18 5 9 Nebalia bipes 44 Crustacea 7 13 10 Ophelia limacina 39 Annelida 6 16 11 Lepidonotus 35 Annelida 7 13 squamatus 12 Ammothella longipes 35 Crustacea 5 18 13 Scoloplos (Scoloplos) 33 Annelida 11 8 armiger 14 Syllis cornuta 33 Annelida 5 18 15 Abra prismatica 33 Mollusca 6 16 Source: Bibby HydroMap, (2017a)
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A total of 29 taxa considered to be epifaunal were recorded during this survey, most of which belonged to the phyla Bryozoa and Cnidaria. Stations 30 m SW, 10 0m NW and PL847_03 showed the highest richness of epifaunal species with 11, 10 and 11 species, respectively. Sponges (Porifera) were only recovered to the southwest of the Guinevere installation at Stations 30 m SW and 250 m SW (Bibby HydroMap, 2017a).
Grab sampling often fails to recover coarse material, especially the larger pebbles and cobbles colonised by epilithic fauna, therefore, it is important to not only assess epifauna through physical samples, but also through analysis of video and still photographs.
Echinoderms were the most conspicuous macrofauna throughout the survey area, most notably the asteroids Asterias rubens (common starfish) and Crossaster papposus (common sun star). Various polychaete tube worms (Lanice conchilega) and Crustacea were seen sporadically during the inspection of areas of sandy seabed as well as some chordate species such as the teleost fish Agonus cataphractus and Gobiidae sp. Amongst the crustaceans, the decapods Liocarcinus depurator, the hermit crab Pagurus bernhardus and the edible crab Cancer pagurus were sporadically identified within the survey area. Some unidentified sponges were noted on the underwater still as well as the occurrence of the Dahlia anemone Urticina felina, both in retracted and exposed forms (Bibby HydroMap, 2017a).
Some examples photographs of species encountered during the Guinevere survey are shown in Figure 3-4.
Figure 3-4: Examples of epifaunal and megafauna species recorded (Bibby HydroMap, 2017a)
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Figure 3-4 (continued): Examples of epifaunal and megafauna species recorded (Bibby HydroMap, 2017a)
No EC Habitats Directive Annex I habitats or other protected habitats/species were encountered during the Guinevere pre-decommissioning environmental survey. Although Sabellaria specimens were identified at a total of five stations, only 15 individuals were recovered throughout the entire survey. The worm tubes were not conspicuous in the video/ photo data acquired and therefore the presence of Sabellaria was only limited to rare occurrences. These occurrences do not require further consideration under the protected ‘reef’ status as outlined in Gubbay (2007). 3.4.3 Fish and shellfish Adult and juvenile stocks of finfish and shellfish are an important food source for seabirds, marine mammals and other fish species. Species can be categorised into pelagic and demersal finfish and shellfish: Pelagic species occur in shoals swimming in mid-water, typically making extensive seasonal movements or migrations between sea areas. Examples include herring, mackerel, blue whiting and sprat;
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Demersal species live on or near the seabed and include cod, haddock, plaice, sandeel, sole, and whiting; Shellfish species are demersal (bottom-dwelling) molluscs, such as mussels and scallops, and crustaceans, such as shrimps, crabs and Nephrops (Nephrops norvegicus).
Generally, there is little interaction between fish species and offshore oil and gas developments. Some fish and shellfish species are, however, vulnerable to some offshore oil and gas activities, such as discharges to sea (Cefas, 2001). The most vulnerable period for fish species is during the egg and juvenile stages of their life cycles. Fish that lay their eggs on the sediment (e.g. herring and sandeel) or which live in intimate contact with sediments (e.g. sandeel and most shellfish) are susceptible to smothering by discharged solids (Coull et al., 1998). Other ecologically sensitive fish species include cod, most flatfish (including plaice and sole) and whiting because in the North Sea these stocks are considered to be outside ‘safe biological limits’ (EEA, 2015). 'Safe biological limits' are defined by a minimum safe stock size and a maximum exploitation rate. The stock size is measured in terms of 'spawning stock biomass (SSB)', which represents the total weight of spawning fish each year. The exploitation rate is measured by 'fishing mortality', which represents the rate at which fish are removed from the stock by fishing. If the stock is either below the minimum safe SSB or above the maximum ‘safe exploitation rate’, the stock is said to be outside safe biological limits (EEA, 2015). A number of factors have contributed to some fish stocks being outside ‘safe biological limits’ and these include a combination of overfishing, poor recruitment and poor fisheries management, with respect to under estimation of fish stocks and related issues (WWF, 2001). The industry-commissioned Fisheries Sensitivity Maps in British Waters and Strategic Environmental Assessment (SEA) 2 Technical Report on North Sea Fish and Fisheries (Coull et al., 1998, Cefas, 2001), as well as the Cefas-led spawning and nursery areas of fish of commercial and conservation importance (Ellis et al., 2010), provide data illustrating fish spawning and nursery locations within International Council for the Exploration of the Seas (ICES) rectangle 35F1, where the Guinevere infrastructure lies (Figure 3-5 and Figure 3-6).
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Figure 3-5: Key fish spawning areas around the Guinevere area
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Figure 3-6: Key fish nursery areas around the Guinevere area
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Spawning and nursery grounds are dynamic features of fish life history and are rarely fixed in one location from year to year. The information provided in Figures 3-5 and Figure 3-6 represents the widest known distribution given current knowledge and should not be seen as rigid, unchanging descriptions of presence or absence (Coull et al., 1998; Ellis et al., 2010). Spawning times represent the generally accepted maximum duration of spawning (Coull et al., 1998). After spawning, fish hatch quickly from their eggs and many species remain in discrete areas (nursery grounds) in the water column or settle on the seabed as larvae, consuming microscopic organisms and gradually developing the body shape and behaviour patterns of adults. The prevailing water temperature and availability of food can alter the position of these nursery grounds from year to year and they can drift far from initial spawning location. As a result of these factors it is difficult to define precisely the limits of nursery areas. The spawning maps in Figure 3-5, along with the nursery maps in Figure 3-6, provide an indication of the likely positions of juvenile concentrations around the UK, rather than a definitive description of the limits of all nursery grounds (Coull et al., 1998). The Guinevere facilities lie within spawning grounds for herring (Clupea harengus; November to January), lemon sole (Microstomus kitt; April to September), mackerel (Scomber scombrus; May to August), sandeels (Ammodytidae spp.; November to January), sole (Solea; March to May) and whiting (Merlangius merlangus; February to June) (Coull et al., 1998; Ellis et al., 2010; Figure 3-5); and within nursery grounds for cod, haddock (Melanogrammus aeglefinus), herring, horse mackerel (Trachurus trachurus), lemon sole, mackerel, plaice (Pleuronectes platessa), sprat (Sprattus sprattus), sole, sandeels and whiting (Aires et al., 2014; Coull et al., 1998; Ellis et al., 2010; Figure 3-6). Data from Aires et al. (2014) indicates the probable presence of Age 0 group fish using previously identified nursery grounds by Coull et al., (1998) and environmental habitat variables (Figure 3-6). Age 0 group fish are defined as fish in the first year of their lives and can also be classified as juvenile. Aires et al. (2014) data indicates a high probability for sole and sprat within Block 48/17b and high probability of sprat in the ICES rectangle, moderate probability for cod and herring within Block 48/17b and herring, horse mackerel and mackerel within ICES rectangle 35F1. 3.4.4 Seabirds Seabirds found in offshore North Sea waters include fulmars (Fulmarus glacialis), gannets (Morus bassanus), auks, gulls, and terns (DTI, 2001), while coastal regions accommodate their breeding colonies (DTI, 2002). The Norfolk coast accommodates one of the most important breeding areas for waders, featuring estuarine shingle structures and beaches, sand dunes and salt marshes (DTI, 2002). In general, offshore areas of the North Sea contain peak numbers of seabirds following the breeding season and through winter, with birds tending to forage closer to coastal breeding colonies in spring and early summer (DTI, 2001). The East Offshore Marine Plan (MMO, 2017) indicates a clear seasonality in seabird density within the vicinity of the Guinevere facilities. The density through the year is typically less than five seabirds per km2 offshore, increasing to between five and ten seabirds per km2 in summer and to ten to 20 seabirds per km2 in winter towards the coast. This estimate is based on information from the combined work of the Marine Management Organisation (MMO) and Joint Nature Conservation Committee (JNCC) looking at the Special Protected Areas (SPAs) in UK waters and the 25 species that breed regularly in UK waters (MMO, 2017). Birds are vulnerable to oiling from surface oil pollution, which can cause direct toxicity through ingestion, and hypothermia as a result of the birds’ inability to waterproof their feathers. During the moulting season, certain species (e.g. guillemot, razorbill and puffin) become flightless and spend a large amount of time on the water surface, making them particularly vulnerable to surface oil pollution (DTI, 2001). However, seabirds are not normally affected by planned offshore oil and gas operations (DTI, 2001). Although locally important numbers of birds have been killed directly by oil spills, such spills have primarily been associated with the transportation of oil, and little or no direct mortality of seabirds has been attributed to exploration, production or decommissioning activities in the North Sea (DTI, 2004).
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Seabird sensitivity to surface pollution varies throughout the year, with peaks in late summer after breeding when the birds disperse into the North Sea, and during the winter months with the arrival of over- wintering birds. Oil and Gas UK commissioned HiDef, a consultancy specialising in a digital aerial video and image analysis, to produce the Seabirds Oil Sensitivity Index (SOSI), a tool designed to aid planning and emergency decision making with regards to oil pollution (Oil & Gas UK, 2016). SOSI identifies sea areas with highest likelihood of seabirds becoming sensitive to oil pollution. It is derived from 1995 to 2015 seabird survey data, extending beyond UKCS and is based upon following factors (Certain et al., 2015): habitat flexibility (an ability of species to relocate to alternative feeding ground); adult survival rate; potential annual productivity; proportion of the biogeographical population in the UK.
The seabird sensitivity to oil pollution in Block 48/17, where the Guinevere infrastructure is located, and in surrounding blocks varies from low to extremely high throughout the year (Oil & Gas UK, 2016). The most sensitive times of year for birds in the Guinevere area are January to March and October to December, with extremely high vulnerability within Block 48/17 in November (Table 3-6). Table 3-6: Seabirds sensitivity to oiling in and around UKCS Block 48/17.
Block Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 48/11 3 3 2 2 5 5 5 3 5 4 2 2 48/12 2 2 2 2 5 5 5 3 3 2 1 2 48/13 1 2 3 3 3 5 5 3 3 1 1 2 48/16 3 4 3 3 5 5 5 4 5 4 2 3 48/17 3 3 3 3 5 5 5 3 4 2 1 3 48/18 5 2 3 3 5 5 5 3 3 1 1 1 48/21 4 4 3 3 5 5 5 4 4 4 2 3 48/22 4 3 3 3 5 5 5 3 3 2 2 2 48/23 2 2 3 3 5 5 5 3 4 2 2 2
KEY 1 Extremely High Seabirds Sensitivity 2 Very High Seabirds Sensitivity 3 High Seabirds Sensitivity 4 Medium Seabirds Sensitivity 5 Low Seabirds Sensitivity ND No Data Block of interest Source: Oil & Gas UK (2016)
3.4.5 Marine mammals Marine mammals include whales, dolphins and porpoises (cetaceans) and seals (pinnipeds). Marine mammals may be vulnerable to the effects of oil and gas activities and can be impacted by noise, contaminants, oil spills and any effects on prey availability (SMRU, 2001). The abundance and availability of prey, including plankton and fish, can be of prime importance in determining the numbers and distribution of marine mammals and can also influence their reproductive success or failure. Changes in the availability of principal prey species may result in population level changes of marine mammals but it is currently not possible to predict the extent of any such changes (SMRU, 2001).
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3.4.5.1 Cetaceans Cetaceans can be divided into two main categories: baleen whales (Mysticeti) which feed by sieving water through a series of baleen plates; and toothed whales (Odontoceti) which have teeth for prey capture. These cetaceans are widely distributed in UK waters and are recorded throughout the year (Reid et al., 2003). Cetacean distribution may be influenced by variable natural factors such as water masses, fronts, eddies, upwellings, currents, water temperature, salinity and length of day. A major factor likely to influence cetacean distribution is the availability of prey, mainly fish, plankton and cephalopods (Stone, 1997). The main cetacean species occurring in UKCS Quadrant 48 and surrounding quadrants are minke whale (Balaenoptera acutorostrata), long-finned pilot whale (Globicephala melas), bottlenose dolphin (Tursiops truncates), common dolphin (Delphinus delphis), white-beaked dolphin (Lagenorhynchus albirostris), white- sided dolphin (Lagenorhynuchus acutus) and harbour porpoise (Phocoena phocoena), with the most sightings occurring in the summer months (Reid et al., 2003; UKDMAP, 1998). The three species recorded throughout the year within Quadrant 48 where the majority of the decommissioning activities will take place are white-beaked dolphin, white-sided dolphin and harbour porpoise (Table 3-7). Table 3-7: Cetacean densities within and around UKCS Quadrant 48.
Species Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Minke whale L L L L L Long-finned pilot whale L Bottlenose dolphin L Common dolphin L M White-beaked dolphin L L M L M L L L M H L White-sided dolphin L L Harbour porpoise M H L H H L VH H L M L
KEY L Low densities Sightings within Quadrant 48 M Moderate densities Sightings in surrounding quadrants H High densities VH Very high densities Source: Reid et al. (2003); UKDMAP (1998) 3.4.5.2 Pinnipeds The grey seal (Halichoerus grypus) and the harbour seal (Phoca vitulina) are both resident in UK waters and occur regularly over large parts of the North Sea (SCOS, 2016). Density mapping by Jones et al., (2015) indicates a high grey seal concentration around the mouth of the Humber River, Humber Estuary Special Areas of Conservation (SAC) and close to the Donna Nook National Nature Reserve (Natural England, 2017a). Figure 3-7 illustrates that seals may travel past the Guinevere facilities to the north and on into their offshore foraging grounds. In the offshore regions of Block 48/17, between zero and one grey seals per 5 km2 could be present at any one point in time (NMPI, 2018; Figure 3-7). Harbour seals have been observed in high concentrations in The Wash National Nature Reserve, which supports one of the largest harbour seal population in England (Natural England, 2017b), and are also more likely to be found further offshore in the area to be decommissioned. It is likely that they are travelling to this area from haul-out sites in The Wash to forage for food. In Block 48/17, between one and ten harbour seals per 5 km2 could be present at any one point in time (NMPI, 2018) (Figure 3.3).
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Figure 3-7: Pinniped density around the Guinevere facilities (NMPI, 2018)
3.4.6 Conservation areas The European Community (EC) Directive 92/43/EEC on the Conservation of Natural Habitats and of Wild Flora and Fauna (the Habitats Directive), and the EC Directive 79/409/EEC on the Conservation of Wild Birds (the Birds Directive), are the main instruments of the European Union (EU) for safeguarding biodiversity. The Habitats Directive includes a requirement to establish a European network of important high quality conservation sites that will make a significant contribution to conserving the habitat and species identified in Annexes I and II of the Directive. Habitat types and species listed in Annexes I and II are those considered to be in most need of conservation at a European level (JNCC, 2002). The Offshore Petroleum Activities (Conservation of Habitats) Regulations 2001 (as amended) implement the EC Habitats Directive (92/43/EEC) in UK Law. These regulations apply to UK waters and to the UK offshore waters. The UK government, with guidance from the JNCC and the Department of Environment, Food and Rural Affairs (Defra), has statutory jurisdiction under the EC Habitats Directive to propose offshore areas or species (based on the habitat types and species identified in Annexes I and II) to be designated as SAC. In relation to UK offshore waters, three habitats from Annex I and four species from Annex II of the Habitats Directive are currently under consideration for the identification of Special Areas of Conservation (SACs) in UK offshore waters (JNCC, 2017a; Table 3-8).
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Table 3-8: Annex I habitats and Annex II species occurring in UK offshore waters
Annex I habitats considered for SAC selection in Species listed in Annex II known to occur in UK UK offshore waters offshore waters Sandbanks which are slightly covered by Grey seal seawater all the time; Harbour (common) seal Reefs (bedrock, biogenic and stony) Bottlenose dolphin o Bedrock reefs – made from Harbour porpoise continuous outcroppings of bedrock which may be of various topographical shape; o Stony reefs – these consist of aggregations of boulders and cobbles which may have some finer sediments in interstitial spaces; and o Biogenic reefs – formed by cold water corals (e.g. Lophelia pertusa and Sabellaria spinulosa). Submarine structures made by leaking gases Source: JNCC (2017a)
3.4.6.1 Annex I habitats Within UK offshore waters there are currently 18 designated SACs, six candidate SACs (cSACs) and one cSAC/ Sites of community Importance (SCIs). cSACs are sites that have been submitted to the EC, but not yet formally adopted and SCIs are sites that have been adopted by the EC but not yet formally designated by the government of each country (JNCC, 2017b). The North Norfolk Sandbanks and Saturn Reef SAC, located 12 km east, is the nearest SAC to the Guinevere NUI (Table 3-9; Figure 3-8). The North Norfolk Sandbanks and Saturn Reef SAC is designated for ‘sandbanks slightly covered by seawater at all times’ and ‘biogenic reefs formed by polychaete worm S. spinulosa’. Both SACs are Annex I habitats (JNCC, 2017c; Table 3-8 and Table 3-9). Table 3-9: Conservation sites within 50 km of the Guinevere installation
Name and Distance & Area Qualifying features designation direction (km2) from Guinevere Southern North 4 km NE 36,951 Primary Annex II species: Sea cSAC Harbour porpoise North Norfolk 12 km E 3,603 Primary Annex I features: Sandbanks and Sandbanks which are slightly covered by sea water Saturn Reef SAC all of the time; Reefs 20 km SW 854 Primary Annex I features: Inner Dowsing, Sandbanks which are slightly covered by sea water Race Bank and all of the time; North Ridge SAC Reefs Haisborough, 43 km SE 1,468 Primary Annex I features: Hammond and Sandbanks which are slightly covered by sea water Winterton SAC all of the time; Reefs
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Name and Distance & Area Qualifying features designation direction (km2) from Guinevere The Wash and 43 km SW 1,077 Primary Annex I features: North Norfolk Sandbanks which are slightly covered by sea water Coast SAC at all times; Mudflats and sandflats not covered by water at low tides; Large shallow inlets and bays; Reefs; Salicornia and other annuals colonising mud and sand; Atlantic salt meadows (Glauco-Puccionellietalia maritimae); Medditerranean and thermo-Atlantic halophilus scrubs (Sarcocornetea fruticosi) Primary Annex II species: Harbour seal Wash Approach 8 km SW 724 Carpets of bryozoans, sea squirts, hydroids, sponges and rMCZ anemones, squat lobsters and crabs. Feeding grounds for harbour porpoises, grey and harbour seals, as well as seabirds. Silver Pit rMCZ 30 km W 168 Crustaceans including edible crabs and common lobsters. Geological feature – the Inner Pit glacial tunnel. Spawning grounds for lemon and Dover sole, sprat, whiting, cod, plaice and herring. Feeding ground for harbour porpoise and minke whale. Holderness 31 km NW 1,176 A mosaic of habitats for attaching and burrowing creatures. Offshore rMCZ Crustaceans including edible crabs and common lobsters. Geological feature – the Inner Silver Pit. Feeding ground for harbour porpoise, grey and harbour seals. Cromer Shoal 43 km S 321 Protected features: Chalk Beds MCZ Moderate energy infralittoral rock, high energy infralittoral rock., moderate energy circalittoral rock, high energy circalittoral rock, subtidal chalk, subtidal coarse sediment, subtidal mixed sediment, subtidal sand, peat and clay exposures, North Norfolk Coast (subtidal; geological feature) Greater Wash 33 km SW 3,606 SPA protected features: SPA Over winter - Red-throated Diver, Common Scoter, Little Gull. Breading season - Common Tern, Sandwich Tern, Little Tern North Norfolk 50 km SW 79 SPA protected features: Coast SPA During breading season - Common Tern, Avocet, Bittern, Little Tern, Marsh Harrier, Mediterranean Gull, Roseate Tern, Sandwich Tern, Redshank Ringed Plover. Over winter - Bar-tailed Godwit; Avocet, Bittern, Golden Plover; Hen Harrier, Ruff; Dark-billed Brent Goose, Knot, Pink-footed Goose, Pintail, Redshank, Wigeon. On passage: Ringed Plover. Source: JNCC (2017b,d), JNCC (2016), Wildlife Trust (2012a,b,c & d), Natural England (2017c)
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3.4.6.2 Annex II species All four Annex II species listed in Table 3-8 are recorded in the vicinity of the Guinevere facilities (UKDMAP, 1998; Reid et al., 2003; Jones et al., 2015). Predicted densities of harbour and grey seals were between one and ten seals per 5 km2 for the area surrounding the Guinevere facilities (NMPI, 2018; Section 3.4.5.2). The Wash and North Norfolk Coast SAC with marine features, designated for protection of harbour seal and a range of Annex I habitats, is located 43 km southwest from the Guinevere installation (Figure 3.5). The Offshore Marine Conservation (Natural Habitats, & c.) (as amended) Regulations 2009 transpose the Habitats Directive and Birds Directive in the marine offshore area, from 12 to 200 nm from the UK coast. Under these regulations it is an offence to: Deliberately disturb any species, that has a designated SAC or SCI while it is within its SAC/ SCI; Capture, injure or kill any wild bird or any wild animal of a European Protected Species (EPS); and/or Significantly disturb any EPS, whether it is within a protected site or not, in such a way as to significantly affect (i) the ability of any significant group of animals to survive, breed, rear or nurture their young; or (ii) the local distribution or abundance of that species.
EPS include all species of cetaceans (whales, dolphins and porpoises), all species of marine turtles, the sturgeon (Acipenser sturio) and the otter (Lutra lutra) (JNCC, 2011). Harbour porpoise Harbour porpoises are highly mobile and well distributed around the UK, with the exception of the English Channel and south-east of England (Reid et al., 2003). Numbers of harbour porpoise in the southern North Sea declined during the twentieth century, but there is evidence of recent return to the area, for example Camphuysen (2004) and Thomsen et al., (2006). Sightings from shipboard and aerial surveys in the North Sea indicate that harbour porpoises are widely and almost continuously distributed, with important concentrations in the central North Sea, along the Danish and northern German coasts (Donovan and Bjørge, 1995; Hammond et al., 2002; IWC, 1996). The seasonal movements and migratory patterns of harbour porpoises in the North East Atlantic and North Sea are not well understood. Porpoises may reside within an area for an extended period of time. However, onshore/ offshore migrations and movements parallel to the shore are thought to occur (Bjørge and Tolley, 2002). In the North Sea, there may be a general westward movement from the eastern North Sea and possibly from the very northern areas of the North Sea into the western edge of the northern North Sea (along the east coast of Scotland) during April to June and a further influx to the northern North Sea during July to September (Northridge et al., 1995). These seasonal movements are thought to coincide with the calving and mating seasons, respectively. There is limited information available on the overall distribution and abundance of this species in UK waters. However, during the 2016 SCANS III surveys, sightings of harbour porpoises were widely distributed throughout the North Sea and adjacent waters, Irish Sea and around the Scottish coast (Hammond et al., 2017). The harbour porpoise abundance estimate in the entire North Sea from the SCANS III surveys conducted in July 2016 is 345,000. During the SCANS III surveys, harbour porpoise density was highest in the south central North Sea and coastal waters of northeast Denmark (~1.1 animals/ km2), elsewhere there was variation in porpoise density from 0.2 to 0.9 animals/ km2 (Hammond et al., 2017). Numbers of porpoise present in UK waters vary seasonally and more animals are likely to pass through UK waters than are present at any one time (JNCC, 2017d). Five cSACs (Bristol Channel Approaches, North Anglesey Marine, North Channel, Southern North Sea and West Wales Marine) have been submitted for the management of harbour porpoise populations in UK Waters (JNCC, 2017e). These cSAC sites have been identified within the North, Irish and Celtic Seas, encompassing areas that represent the physical and biological factors essential to harbour porpoise. The
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3.4.6.4 Special Protection Areas SPAs are protected sites, which have been classified in accordance with Article 4 of the EC Birds Directive. They are designated based on the location of rare and vulnerable birds and also for frequently occurring migratory species, which are listed on Annex I of the Directive. The UK currently has 102 SPAs with marine components, with only four entirely marine. The Guinevere infrastructure does not transect any SPAs with marine components; however, there two are located within 50 km of the Guinevere NUI; the Greater Wash and the North Norfolk Coast SPAs (Table 3-9).
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Figure 3-9: Conservation areas in the vicinity of Guinevere facilities
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3.5 Summary of Environmental Characteristics and Sensitivities Table 3-10 summarises the environmental sensitivities in the area surrounding the Guinevere infrastructure. Table 3-10: Summary of environmental characteristics and sensitivities
Aspect Months of the Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Site overview The Guinevere infrastructure is located in the southern North Sea Quadrant 48, within Blocks 48/17a and 48/17b. Conservation interests Offshore and Coastal Marine Protected Areas and Annex I habitats North Norfolk Designated for: Sandbanks and Sandbanks which are slightly covered by seawater all the time. Saturn Reef SAC Annex I biogenic reef habitats formed by the polychaete worm (S. spinulosa) Located 12 km east of the Guinevere NUI. Inner Dowsing, Designated for: Race Bank and Sandbanks, which are slightly covered by seawater all the time; North Ridge SAC S. spinulosa reef habitats. Located 20 km southwest of the Guinevere NUI. Haisborough, Designated for: Hammond and Sandbanks, which are slightly covered by seawater all the time; Winterton SAC S. spinulosa reef habitats. Located 43 km southeast of the Guinevere NUI. The Wash and Designated for: North Norfolk Sandbanks, which are slightly covered by seawater all the time; Coast SAC Mudflats and sandflats not covered by water at low tide; Large shallow inlets and bays; Salicornia and other annuals colonising mud and sand; Atlantic salt meadows (Glauco-Puccionellietalia maritimae); Mediterranean and thermo-Atlantic halophilus scrubs (Sarcocornetea fruticosi). Located 43 km southwest of the Guinevere NUI. Wash Approach Designated for: rMCZ Carpets of bryozoans, sea squirts, hydroids, sponges and anemones, squat lobsters and crabs. Located 8 km southwest of the Guinevere NUI. Silver Pit rMCZ Designated for: Crustaceans including edible crabs and common lobsters; Geological feature – (the Inner Pit glacial tunnel); Spawning grounds for lemon and Dover sole, sprat, whiting, cod, plaice and herring. Located 30 km west of the Guinevere NUI.
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Holderness Designated for: Offshore rMCZ Mosaic of habitats for attaching and burrowing creatures; crustaceans including edible crabs and common lobsters; Geological feature – (the Inner Silver Pit). Located 31 km northwest of the Guinevere NUI. Cromer Shoal Protected features: Chalk Beds MCZ Moderate energy infralittoral rock, high energy infralittoral rock, moderate energy circalittoral rock, high energy circalittoral rock, subtidal chalk, subtidal coarse sediment, subtidal mixed sediment, subtidal sand, peat and clay exposures. Located 43 km south of the Guinevere NUI. Greater Wash SPA protected features: SPA Over wintering: Red-throated Diver, Common Scoter, Little Gull. During breading season: Common Tern, Sandwich Tern, Little Tern Located 33 km southwest of the Guinevere NUI. North Norfolk SPA protected features: Coast SPA Over winter: Bar-tailed Godwit; Avocet, Bittern, Golden Plover; Hen Harrier, Ruff; Dark-billed Brent Goose, Knot, Pink-footed Goose, Pintail, Redshank, Wigeon. During breading season: Common Tern, Avocet, Bittern, Little Tern, Marsh Harrier, Mediterranean Gull, Roseate Tern, Sandwich Tern, Redshank Ringed Plover. On passage: Ringed Plover. A wetland of international importance. Located 50 km southwest of the Guinevere NUI. Annex II species Month Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Harbour M H L H H L VH H L M L porpoise Bottlenose L dolphins Grey seals Grey seal density in the vicinity of the Guinevere facilities ranges from 0 to 1 seals per 5 km2 (NMPI, 2018). Haul-out and breeding sites are located within the Humber Estuary SAC the Donna Nook National Nature Reserve (Natural England, 2017a). Harbour seals Harbour seal density in the vicinity of the Guinevere facilities ranges from 1 to 10 seals per 5 km2 (NMPI, 2018). Haul-out and breeding sites are located within The Wash and North Norfolk Coast SAC. This site represents the largest colony of harbour seals in the UK, with approximately 7% of the total UK population (Natural England, 2017b). Southern North Chosen to protect Annex II species, harbour porpoise. Located 4 km northeast of the Sea SAC Guinevere platform (JNCC, 2017e). Plankton
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Plankton in the area surrounding the Guinevere facilities is typical for the southern North Sea. Dominant phytoplankton species are dinoflagellates of the genus Ceratium, including C. fusus, C. furca and C. tripos. High numbers of the genus Cheaetoceros are also present. Dominant species of zooplankton present include small copepods including Para-Pseudoclanus spp., and echinoderm larvae. The larger species of copepods, Calanus helgolandicus and Metridia lucens are also present.
Benthic environment Particle size distribution analysis revealed the majority of samples to be dominated by the sand fraction (>63µm and <2000µm) with two stations containing over 98% sand. The EUNIS classification system identifies two Level 4 seabed habitats within the blocks as: A5.25 - Circalittoral fine sand A5.26 - Circalittoral muddy sand Benthic fauna The macrofauna throughout the Guinevere survey area showed some small-scale variability in terms of abundance, richness and species composition associated with the sediment composition across the survey area. The infaunal community was dominated by annelids, followed by crustaceans and molluscs in terms of species richness, however crustaceans were the dominant group with regard to individual abundance. Colonial epifauna were less dominant in terms of species richness and abundance (Bibby HydroMap, 2017a). Fish – spawning and nursery for the ICES Rectangle 35F1 (coull et al., 1998; Ellis et al., 2010 and Aires et al., 2014) Mackerel N N N N NS* NS* NS* NS N N N N Herring N N N N N N N NS NS NS N N Cod N N N N N N N N N N N N Hake N N N N N N N N N N N N Haddock N N N N N N N N N N N N Whiting N NS NS NS NS NS N N N N N N Plaice N N N N N N N N N N N N Lemon sole N N N NS NS NS NS NS NS N N N Sole N N NS NS* NS N N N N N N N Sandeels NS NS N N N N N N N N NS NS Sprat N N N N N N N N N N N N Horse N N N N N N N N N N N N mackerel Key: Fish S spawning S* peak spawning N nursery spawning/ nursery Seabirds Block 48/17 The most common species of seabird found in these areas of the SNS include: Fulmar, Gannet, Guillemot, Kittiwake, Razorbill, Puffin, Little Auk; as well as numerous species of gull, tern and skua. Seabirds 3 3 3 3 5 5 5 3 4 2 1 3 sensitivity
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2 Very high sensitivity 4 Medium sensitivity
Marine mammals Quadrant 48 and surrounding quadrants Harbour M H L H H L VH H L M L porpoise White-beaked L L M L M L L L M H L dolphin Minke whale L L L L L Long-finned L pilot whale Bottlenose L dolphin Common M dolphin White-sided L L dolphin
KEY Cetaceans abundance
VH Very high cetaceans abundance H High cetaceans abundance M Moderate cetaceans abundance L Low cetaceans abundance No data
3.6 Socioeconomic Environment This section focuses on the broader socioeconomic considerations of the existing baseline in relation to the Guinevere decommissioning activities. Attention is given to the potential impact on the fishing (UK and non-UK fishing in the area) and shipping industries as well as any potential impact on other users of the sea, such as military activity and activity within the renewable energy sector. The existence of submarine cables, historic wrecks as well as other oil and gas installations are also considered. 3.6.1 Commercial fisheries An assessment of the fishing industry in the vicinity of the Guinevere facilities has been derived from ICES fisheries statistics, provided by MMO and Marine Scotland Science Division. Offshore oil and gas operations, including decommissioning activities, have the potential to interfere with fishing activities, for example as a result of the exclusion of fishing vessels from around an area of operation (Cefas, 2001). It is therefore important to have an understanding of the fishing activities and intensity in the area around the Guinevere facilities in order to evaluate the potential impacts associated with the proposed decommissioning on the fishing industry. For management purposes, ICES collates fisheries information for individual rectangles measuring 30 by 30 nm. Data was obtained for ICES rectangle 35F1, which contains the Guinevere facilities. Statistical data
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GUINEVERE INSTALLATION DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT from the ICES rectangles provide information on the UK fishing live weight of demersal, pelagic and shellfish species caught by all UK vessels between 2013 and 2015 and by foreign fishing vessels landed in UK (MMO, 2017). Data on the economic value of the fishing industry in this area has been produced based on UK catches and landings (MMO, 2017). The overall value of different fisheries by area (financial yield per ICES rectangle) is an indication of the differential worth of areas and is used as a method of expressing commercial sensitivity (Coull et al., 1998). The type of fishing gear and techniques employed by fishermen depends on a variety of factors, such as: Species fished, e.g. demersal, pelagic or shellfish. Depth of water and seabed topography. Seabed characteristics. Species found in the water column (pelagic species) are fished using techniques that do not interact with the seabed, whereas demersal and shellfish species are generally fished on or near the seabed. Finfish, such as cod, whiting, haddock and flatfish, and shellfish species, such as Nephrops, which are found on or near the seabed, are caught by demersal gear. Demersal trawling methods interact with the seabed, and may interact with the existing infrastructure on the seabed and historical seabed anomalies created by oil and gas activities, including disturbance from subsea structures left in situ such as footings, pipelines, rock- placement or concrete mattresses left or buried in the sediment. 3.6.1.1 Fishing effort The total number of days’ effort in ICES rectangle 35F1 was 767 days in 2013 and 572 days in 2014, with no data available for 2015 or 2016 (MMO, 2017). The fishing effort was dominated by pots and traps (MMO, 2017). 3.6.1.2 Fishing quantity and value Relative quantity and value of fish landed from ICES rectangle 35F1 in 2015 was low for pelagic and demersal species and moderate for shellfish species (Table 3-11). Between 2013 and 2016, the annual total live weight of fish landed from ICES rectangle 35F1 ranged from a low of 936 tonnes in 2015 to a high of 1,417 tonnes in 2013 and total annual value from a low of £1,157,009 in 2015 to a high of £1,286,988 in 2014 (MMO, 2017; Tables 3-12 & 3-13). 3.6.1.3 Catch composition Shellfish species dominated the catch (98 to 100%) in 2014 to 2016, with demersal species accounting for 1 to 2% of the catch (MMO, 2017). Catch composition by weight of UK landings from UK and foreign vessels in ICES rectangle 35F1 for 2016 was dominated by crabs, lobsters and whelks. Crabs and lobsters made up 15% and 35% respectively, and whelks 60% of the catch in 35F1 during this period (MMO, 2017; Figure 3- 12). Table 3-11: Relative quantity and value of fisheries in ICES rectangle 35F1 in 2016
Species type Fisheries relative value (£) Relative quantity landed (tonnes) Demersal Low (≤500,000) Low (<300) Pelagic ND ND Shellfish Moderate (500,000 to <2,000,000) Moderate (500 to <2,000) Source: MMO (2017). ND: No Data Table 3-12: Total landings (tonnes) of demersal, pelagic and shellfish species caught in ICES rectangle 35F1 by UK and foreign vessels between 2013 and 2016
Species type Live weight (tonnes) 2013 2014 2015 2016 Demersal 25 22 8 2 Pelagic 0 0 0 0
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Shellfish 1,392 1,100 928 1,117 Total 1,417 1,122 936 1,118 Source: MMO (2017) Table 3-13: Total annual value (£) of demersal, pelagic and shellfish species caught in ICES rectangle 35F1 by UK and foreign vessels between 2013 and 2016
Species type Annual Value (£) 2013 2014 2015 2016 Demersal 115,120.2 76,721.05 27,013.57 8,065.73 Pelagic 400 0 20 0.00 Shellfish 1,344,793 1,210,267 1,129,975 1,454,308.00 Total 1,460,313 1,286,988 1,157,009 1,462,374 Source: MMO (2017)
3.6.2 Vessel Monitoring System (VMS) data VMS (satellite tracking) data complement ICES fisheries statistics data presented above and shows satellite tracking data for the years 2009 to 2013 for all UK registered commercial fishing vessels over 15 m in length (Kafas et al., 2013). To differentiate between vessels steaming and fishing, only vessels with speeds between 0 and 6 knots were assumed to be fishing. The available data is limited to Nephrops, demersal species, pelagic (mackerel and herring), crab, lobster, scallop and squid fisheries (Kafas et al., 2013)). Data shows high activity of vessels fishing for lobster in the ICES rectangle 35F1 between 2009 and 2013 (Figure 3.10).
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Source: Kafas et al. (2013)
Figure 3-10: Satellite (VMS) fishing intensity of UK vessels over 15 m near the Guinevere facilities
3.6.3 Nearby oil and gas infrastructure The Guinevere facilities are located in the southern North Sea gas basin, which is densely populated by various installations (Figure 1-2).The closest platforms and pipelines, located within approximately 15 km from the Guinevere infrastructure, are listed in Table 3-14.
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Table 3-14: Oil and gas developments located within15 km from the Guinevere infrastructure
Infrastructure Distance and direction from the Operator Guinevere infrastructure Platforms Lancelot A Platform 6.9 km E Perenco UK Ltd Excalibur EA Platform 7.3 km NE Perenco UK Ltd Waveney Production Platform 7.3 km S Perenco UK Ltd Pickerill B Platform 14.4 km NW Perenco UK Ltd Malory Platform 14.5 km N Perenco UK Ltd Galahad Platform 15.6 km NE Perenco UK Ltd Pipelines PL979 Lancelot to Excalibur 6.9 km E Perenco UK Ltd PL1167 Lancelot to Galahad 6.9 km E Perenco UK Ltd PL1639/ PL1640 Waveney to Lancelot 6.9 km SE Perenco UK Ltd PL454 LOGGS PP to Theddlethorpe 3.6 km S Conoco Phillips Durango to Waveney 7.3 km S Perenco UK Ltd PL1627 Malory to Galahad Tee 13.4 km N Perenco UK Ltd PL818/ PL819 Pickerill A to Pickerill B 14.5 km NW Perenco UK Ltd PL877 Bacton to Lancelot 6.9 km E Perenco UK Ltd Source: UK Oil and Gas Data (2017)
3.6.4 Commercial shipping Overall shipping density in the vicinity of the Guinevere facilities is considered moderate (BEIS, 2016b). The MMO has made vessel Automated Identification System (AIS) data available for 2012, which present average weekly shipping densities (Figure 3-11). The Anatec vessel traffic survey considered shipping routes in the vicinity of the Guinevere infrastructure from July to December 2016 (Anatec, 2017). Results revealed 63 shipping routes used by an estimated 12,771 vessels per year passed within 10 nm of the Guinevere installation, corresponding to an average of 35 vessels per day (Anatec, 2017). The majority of vessels recorded in the vicinity of the Guinevere installation were cargo tanks (55%), including freight ferries, container ships and general cargo vessels, and tankers (31%). The remaining vessels included platform supply vessels (PSV), passenger, tug, windfarm, military, dredgers, HSC vessels, as well as lifeboats, fishery research vessels and bout tender vessels (Anatec, 2017). 3.6.5 Military activities There are no recorded military training or disposal sites located within Block 48/17. However, there is a licence condition applied by Department for Business, Energy and Industrial Strategy (BEIS) on behalf of the Ministry of Defence (MoD) obliging the licence holder to notify the MoD prior to any activities in the block of interest (BEIS, 2016b). 3.6.6 Submarine cables Currently there are no subsea cables laid within Block 48/17 (NMPI, 2018). The nearest are the Hornsea project wind export cable located 28 km north and the Norsea Com 1 telecommunication cable located 63 km east from the Guinevere installation (NMPI, 2018).
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Figure 3-11: Average weekly shipping density near the Guinevere facilities in 2012
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3.6.7 Marine archaeology and wrecks In the UK, submerged prehistoric sites and shipwrecks are not protected unless specific action has been taken to protect them. There are, however, two different acts under which wrecks that may be of archaeological interest may be designated, namely the Protection of Wrecks Act 1973 and the Protection of Military remains Act 1986. Designation of wrecks and submerged prehistoric sites is also possible under a third act, the Ancient Monuments and Archaeological Areas Act 1979, which applies to Scotland, England and Wales (DECC, 2009). There are no recorded wrecks in Block 48/17, (NMPI, 2018) however, there are 72 wrecks located in surrounding blocks (Table 3-15). Table 3-15: Summary of wrecks located in blocks surrounding the Guinevere facilities
Block Number of wrecks Category Location of the nearest wreck in relation to Guinevere infrastructure 48/11 11 dangerous 24.6 km NW 48/12 3 dangerous 11.7 km NE 48/13 2 dangerous 24.7 km NE 48/16 13 11 dangerous 3.9 km W 2 non-dangerous 48/17 0 - - 48/18 0 - - 48/21 27 dangerous 14.2 km SW 48/22 11 dangerous 10.5 km S 48/23 5 dangerous 15.6 km SE Source: NMPI (2018)
3.6.8 Renewable energy activity There are many marine and coastal areas around the UK being investigated and/ or developed as renewable energy resources. Wave, tidal and wind renewable energy studies and projects are underway in several areas. 3.6.8.1 Wave and tidal The UK has a particularly good marine current resource with at least 40 possible locations having currents of a suitable speed for energy generation. Many of these are within the waters off Shetland and Orkney. No tidal and energy zones are located in the vicinity of the Guinevere facilities. 3.6.8.2 Wind There are four known windfarms located in the vicinity of the Guinevere facilities (Table 3-10; Crown Estate, 2016). 3.6.8.3 Gas and carbon capture and storage activities As a result of declining natural gas resources in the North Sea, pressure is mounting for more investment in UK gas storage facilities to ensure integrity of supply. There are currently no offshore gas storage facilities in operation in the UK, although licences have been granted such as ENI’s Deborah field located in Block 48/29 in the southern North Sea, 47 km southeast of the Guinevere installation (Table 3-16). The use of existing storage facilities and associated infrastructure is unlikely to have a significant environmental impact, although the release of hypersaline water in the production of salt caverns may have some localised effects (Scottish Government, 2017).
Carbon capture and storage (CCS) is a new technology being developed to manage the emissions of CO2 and reduce the contribution of fossil fuel emissions to global warming. The closest to the Guinevere facilities is the Endurance project located over 70 km north (Table 3.16). There are no known CCS plans in the vicinity of the Guinevere facilities (Crown Estate, 2016).
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Table 3-16: Crown Estate activities located in the vicinity of the Guinevere facilities
Type of activity Area name Status Distance and direction from Block 48/17 Windfarm Dugeon Under construction 12.7 km SE Windfarm Sheringham Shoal Active 31 km S Windfarm Triton Knoll Consented 17 km W Windfarm Race Bank Under construction 30 km SW Minerals aggregations Outer Dowsing Active dredging 3.5 km W (515/2) Minerals aggregations Outer Dowsing Active dredging 17.2 km W (515/1) Minerals aggregations Humber 3 (484) No active dredging 40 km E Gas storage Deborah Agreement to lease 47 km SE Carbon capture storage Endurance Agreement to lease 71 km N (CCS) Source: Crown Estate (2016); BMAPA (2015)
3.6.8.4 Dredging and aggregate extractions Aggregates are mixtures of sand, gravel, crushed rock or other bulk minerals used in construction, principally as a component of concrete. Most UK dredging sites are located in the southern North Sea with the main region of aggregate extraction in the North Sea being the Humber Region (DTI, 2001). The closest one, the Outer Dowsing, with active dredging, is located 3.5 km west from the Guinevere installation (Table 3.16; Crown Estate 2016). 3.7 Summary of Socioeconomic Characteristics and Sensitivities Table 3-17 summarises the socioeconomic sensitivities in the area surrounding the Guinevere facilities. Table 3-17: Summary of socioeconomic characteristics and sensitivities
Aspect Characteristics Commercial fisheries landings and value range from low to moderate within International Council for the Exploration of the Sea rectangles 35F1. Fishing gear types include harvesting machines, traps and trawls. The annual value of catches in 2015, ranged from £3,393 to £236,747, where the majority of fish were landed between April and July. Fishing Vessel Monitoring Systems (data for all UK vessels greater than 15 metres in length landing into UK ports (2009 to 2013), shows that mobile demersal fishing activity was low within the blocks of interest and an area of high activity for Lobster fishing lies in the northwest of International Council for the Exploration of the Sea Rectangle 35F1. Shipping activity Shipping density within the block of interest is regarded as moderate. Structures in the vicinity of the pipelines include the Guinevere and Lancelot Oil and Gas Platforms (both adjacent to the pipelines), the Excalibur platform (7 km to the northeast) and the Waveney platform (7.3 km to the south). Telecommunications No cables are laid within Block 48/17 No military activities occur in Block 48/17. There is a license condition obliging Military activities the license holder to notify the MoD prior to any activities in this block. The closest wind farm (Dugeon) to the pipelines is under construction located Windfarms 12.7 km to the southeast of the nearest pipeline point.
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Aspect Characteristics Sheringham Shoal wind farm is located 31 km to the south of the pipelines and a further consented wind farm will be located at Triton Knoll, 17 km to the west of the pipelines. No designated historical wrecks have been recorded in Block 48/17. There are 70 wrecks classed as dangerous by the United Kingdom Hydrographic Office in the Wrecks vicinity of the Guinevere Decommissioning area, the closest one is located 3.9 kilometres to the west. The Hornsea project wind export cable is located 28 km to the north of the Telecommunications pipelines. No telecommunication cables are present in block 48/17. Two active dredging aggregate extraction sites are located in the vicinity of the Aggregate extraction Guinevere Decommissioning area, Outer Dowsing (515/2) and Outer Dowsing (515/1), 3.5 and 17.2 km to the west, respectively. The Deborah gas storage area is located 47 km to the southeast of the Guinevere Gas Storage facilities and is currently under agreement for lease (Crown Estate, 2016).
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4 EVALUATION OF POTENTIAL ENVIRONMENTAL IMPACTS As required by the Petroleum Act, 1998 and OSPAR Decision 98/3, this section identifies and ranks the environmental and societal impacts and risks that could arise from planned and unplanned activities associated with the proposed decommissioning activities. The activities associated with the decommissioning of the Guinevere installation have the potential to result in an environmental impact in several different ways, including the physical disturbance of the seabed, gaseous emissions to the atmosphere and waste generation for disposal onshore. These effects could arise as consequences of the following aspects of the decommissioning programme, which have also been outlined in Section 2: General decommissioning activities; Full removal of the topsides and jacket; Leaving the dispersed drill cuttings in situ.
An assessment of the significance of the risks to any environmental and societal receptor as a result of the operations was undertaken. The assessment looked at both planned operations and unplanned, accidental events. Where appropriate, site specific, transboundary and cumulative impacts were also included in discussions during the risk assessment process.
4.1 Risk Assessment Methodology The purpose of the risk assessment is to: Identify potential environmental impacts that may arise from the proposed decommissioning activity; Evaluate the potential significance of those potential impacts in terms of the threat that they pose to specific environmental receptors; Assign measures to manage the risks in line with industry best practice; and Address concerns or issues raised by stakeholders during the consultation for this EIA.
The risk assessments were undertaken using the following method: 1. Each decommissioning option was broken into its component activities, operations and end-points. 2. Receptors at risk (societal or environmental elements) were identified from the potential operational impacts and end-point impacts (Table 4-1). 3. The significance of the potential environmental impacts and risks was assessed according to pre- defined criteria. These criteria recognise the likely effectiveness of planned mitigation measures to minimise or eliminate potential impacts/ risks. 4. Assessments were undertaken to determine what level of impacts/ risks the component activity/ operation could pose to the different groups of environmental or societal receptors. The following Scoring Criteria and Risk Matrix were applied to complete the associated worksheets: PUK's Consequence Matrix (Table 4-2). PUK's Likelihood Matrix (Table 4-3). 5. The overall significance of risk for a particular activity was determined by the PUK’s Risk Matrix (Table 4-4).
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Table 4-1 Listing of environmental and societal receptors
Physical and chemical Biological Societal
Sediment disturbance Sediment biology (benthos) Commercial fishing Water quality Water column (plankton) Shipping Air quality Finfish and shellfish Government or institutional users Land Marine mammals (e.g. Ministry of Defence [MoD]) Freshwater Seabirds Other commercial users Ecosystem integrity Recreational users Conservation sites Onshore communities (resources) Terrestrial flora and fauna
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Table 4-2 PUK’s consequence matrix
Impact Level Consequence criteria 1 (Very low) 2 (Low) 3 (Medium) 4 (High) 5 (Very high) 1. Safety Potential snagging Loss of fishing gear/ 1.1 Risk to other users of hazard if protection Vessel collision/ No risk. vessel infringes tow Loss of vessel. the sea (post operations) deteriorates or is damage to vessel. exclusion zone. moved. 1.2 Risk to those on land FAC or no specific RWC/ Day away from Fatality or long-term Multiple fatalities or MTC/ RWC (during operations) treatment. work case. injury. long-term injury. 1.3 Risk to 3rd party Standard operations Impact with 3rd party Impact with 3rd party Crossing 3rd party assets/ vessels (during No risk. required in 500 m asset – no loss of asset – loss of assets. operations) zones. containment. containment. 2. Environmental Discharge causes Discharge causes Discharge causes Discharge causes changes, which are change in ecosystem change in ecosystem change in ecosystem No or negligible 2.1 Chemical discharge unlikely to be leading to medium term leading to long term leading to medium term discharge. measureable against damage but with good damage but with good damage but with poor background activities. recovery potential. recovery potential. recovery potential. 2.2 Hydrocarbon No or negligible 1 – 100 litres oil. 100 – 1,000 litres oil. 1 – 10 m3 oil. >10 m3 oil. discharge discharge Medium hydrocarbon Very high hydrocarbon Low hydrocarbon High hydrocarbon concentration and/ or concentration and/ or 2.3 Seabed disturbance None. concentrations and/ or concentration and/ or moderate rate of very rapid rate of very gradual release. rapid rate of release. release. release. Wider area of Localised disturbance (0 Localised disturbance Wide area of disturbance (100 – 2.4 Energy use 0 – 10 GJ - 100% of equipment (100% of equipment disturbance (>200% of 200% of equipment footprint). footprint). equipment footprint). footprint). 2.5 Estimated discard to 0% 10 – 100 GJ 100 – 200 GJ 200 – 400 GJ >400 GJ sea (% of total material)
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Impact Level Consequence criteria 1 (Very low) 2 (Low) 3 (Medium) 4 (High) 5 (Very high) 2.6 Estimated discard to landfill (% of total 0% 0 – 20% 20 – 50% 50 – 80% >80% material) 3. Technical Regular construction Regular construction Non-routine task. High Non-routine task. Low Novel technique or 3.1 Technical challenge task using generic task using detailed level of historical level of historical equipment. No industry procedures. procedures. experience. experience. experience. 3.2 Level of diving <10 days 10 - 20 days 20 - 30 days 30 – 40 days >40 days intervention Requires specific Requires specific Standard operations Required specific General operations weather window for weather window for experiencing expected weather window for 3.3 Weather sensitivity relying only on ability to certain tasks. Schedule prolonged period. operational downtime small number of tasks. launch ROV. can be optimised to Operation on critical for time of year. Non schedule critical. accommodate. path. Existing, proven Existing, proven Unable to complete Technology research Potential catastrophic 3.4 Risk of major project equipment used for equipment used for operation in scheduled and development failure of major failure specific task for which it specific task for new timeframe. Re-work required. component. was designed. application. required prior to revisit. 4. Societal 4.1 Fisheries access (post Free, unrestricted Unrestricted access to Access to site with Access to site with Site remains restricted. operations) access to site. site – noted seabed overtrawlable charted charted obstructions. disturbance. obstructions. 4.2 Communities No impact. Low impact (dust, noise Short term impact to Long term impact to High impact to onshore etc.) onshore communities onshore communities communities (pollution, (waste handling traffic (landfill, infrastructure, loss of amenity, etc.). etc.). etc.). 5. Legal compliance Compliant with 5.1 OSPAR 98/3 Fully compliant. Not applicable. Not applicable. Non-compliant. derogation. Total removal of Burial 0.6 m below Buried but not to depth Exposed at some 5.2 NFFO Guidance Totally exposed. structure. natural seabed level. required. locations.
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Impact Level Consequence criteria 1 (Very low) 2 (Low) 3 (Medium) 4 (High) 5 (Very high) 6. Commercial £5,000,000 - £10,000,000 - 6.1 Economic <£1,000,000 £1,000,000 - £5,000,000 >£15,000,000 £10,000,000 £15,000,000 Bi-annual survey Survey inspection at Annual surveys and 6.2. Ongoing liability No ongoing liability. Reactive survey regime. inspection and ongoing increasing intervals. ongoing remedial work. remedial work. Note: First Aid Case (FAC); Medical Treatment Case (MTC); Real World Case (RWC); Gigajoules (GJ)
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Table 4-3 PUK’s likelihood matrix
Likelihood rating Very low likelihood. 1 Very low Very low level of uncertainty. Detailed definition and understanding of methodology, hazards and equipment. Low likelihood. 2 Low Low level of uncertainty. High level definition and understanding of methodology, hazards and equipment. Moderate likelihood. 3 Medium Moderate level of uncertainty. General definition and understanding of methodology, hazards and equipment. High likelihood. 4 High High level of uncertainty. Basic definition and understanding of methodology, hazards and equipment. Very high likelihood. 5 Very high Very high level of uncertainty. Limited definition and understanding of methodology, hazards and equipment.
Table 4-4 PUK’s risk matrix
Consequences 1 (Very low) 2 (Low) 3 (Medium) 4 (High) 5 (Very high) Very Low Low Low Low Medium 1 low 1 2 3 4 5
Low Low Medium Medium Medium 2 Low 2 4 6 8 10 Low Medium Medium Medium High 3 Medium 3 6 9 12 15 Likelihood Low Medium Medium High High 4 High 4 8 12 16 20 Very Medium Medium High High High 5 high 5 10 15 20 25
4.2 Risk Assessment Findings A detailed outcome of the risk assessment is presented in Table 4-5. The left-hand column of the detailed tables identifies those activities associated with the Guinevere Installation DP that may cause, or have the potential to cause, impacts to sensitive receptors. These environmental aspects (BSI, 2015) include planned and unplanned events during the lifetime of the decommissioning project. The remaining columns of the tables identify the potential environmental (physical, chemical, biological) and societal receptors. The final two right-hand columns of the table presents the overall assessed risk category and the sections of the report that give a detailed justification of the assessment made. Taking the effects of planned mitigation into account, the risk assessment indicates that the general decommissioning activities carry one activity identified as high risk and the other decommissioning activities relating to the jacket and topside decommissioning have several medium risks associated with them. These risks are assessed further in Sections 5 to 10: Energy use and atmospheric emissions (Section 5); Underwater noise (Section 6);
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Seabed impact (Section 7); Societal impact (Section 8); Accidental events (Section 9); and Waste (Section 10) Table 4-6 provides a summary of the risk assessment and the significance assigned to the decommissioning activities assessed in Table 4-5. Where stakeholder concerns have been raised (Table 1-3) these have also been considered within Sections 5 through to 10. For the impacts or risks that were considered to be low, Appendix B provides the justification for excluding these potential impacts and risks from further investigation in the EIA.
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Table 4.5: Assessment of significance of environmental impacts
Physical and Chemical Biological Societal
Seabed disturbance quality Water quality Air Land Freshwater Sediment biology (benthos) column Water (plankton) and Finfish shellfish Marine mammals Seabirds Ecosystem integrity Conservation sites Terrestrial flora and fauna Commercial fishing Shipping Government, institution (e.g. users Other MOD) commercial users Recreation amenity and users Onshore Communities (Resources) Likelihood Consequence Overall significance Justification section(s) reference General decommissioning activities - Planned operations
Physical presence of vessels 3 1 3 Appendix B Well P&A using explosives 5 4 20 6 Removal of the wellheads 3 1 3 Appendix B Anchoring of the accommodation barge (Seafox 1) for P&A, 7 preparation and cleaning 3 2 6 Use of rock stabilisation on the seabed for support of the 7, 8 accommodation barge (Seafox 1) 2 3 6 Underwater noise from dynamic positioning of vessels, 6 engines and on-board equipment 5 2 10 Noise generated from helicopter transport 2 1 2 Appendix B Operational discharges of treated oily bilge from vessels 2 1 2 Appendix B Waste produced from onsite vessels 2 1 2 Appendix B Sewage and grey water discharges from vessels 2 1 2 Appendix B Macerated food waste discharge from vessels 2 1 2 Appendix B Ballast water uptake and discharge from the vessels 3 1 3 Appendix B Atmospheric emissions from vessels 5 1 5 5 Atmospheric emissions from helicopters 5 1 5 5 General decommissioning activities - Unplanned operations Dropped objects 1 2 2 Appendix B Well blow-out 1 5 5 9 Diesel spill/ tank loss 1 5 5 9 Chemical spill 1 5 5 9 Bunkering spill 1 5 5 9 Vessel to vessel collision 1 5 5 9 Full removal of topsides and jacket (single or multiple lifts) - Planned operations Atmospheric emissions associated with power generation for Appendix B topside separation and cutting (plasma, flame or cold 2 1 2 cutting), underwater cutting of jacket and lifting activities Topside preparation, separation and cutting (plasma, flame Appendix B or cold cutting) 4 1 4 Excavation of piles using jetting and dredging techniques 4 1 4 Appendix B Underwater cutting (diamond wire, oxyacetylene, high Appendix B pressure water abrasive) of jacket piles 3 m below seabed 4 1 4 Anchoring of the lift vessel 3 2 6 7 Use of rock placement on the seabed for support of the lift 7, 8 vessel 2 3 6 Dismantling structures/ recovery/ transport and recycling of 5, 8, 10 materials onshore 2 3 6 Disposal and treatment of solid and potentially hazardous 10 waste 2 3 6 Presence of scour around the legs of the Guinevere jacket 2 1 2 Appendix B Full removal of topsides and jacket (single or multiple lifts) - Unplanned operations Vessel to vessel collision 1 5 5 9
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Physical and Chemical Biological Societal
Seabed disturbance quality Water quality Air Land Freshwater Sediment biology (benthos) column Water (plankton) and Finfish shellfish Marine mammals Seabirds Ecosystem integrity Conservation sites Terrestrial flora and fauna Commercial fishing Shipping Government, institution (e.g. users Other MOD) commercial users Recreation amenity and users Onshore Communities (Resources) Likelihood Consequence Overall significance Justification section(s) reference Dropped object (Topside and/ or jacket loss during lifting and 1 3 3 Appendix B transportation) Leave dispersed drill cuttings in situ - Planned operations Disturbance of any areas of contaminated sediment during Appendix B excavation and removal of jacket 4 1 4 Leave dispersed drill cuttings in situ - Unplanned operations Post – decommissioning disturbance of any areas of Appendix B contaminated sediment during trawling activities 4 1 4
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Table 4-6 Summary of risk categories associated with decommissioning activities during the environmental and societal risk assessment.
Risk categories Low Medium High
Decommissioning activities
operations
Planned operations Planned operations Unplanned operations Planned operations Unplanned Planned operations Unplanned General decommissioning activities Full removal of topsides and jacket (single or multiple lifts) Leave dispersed drill cuttings in situ Note: Risk category is based on the highest scoring activity for each option (Table 4-5).
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GUINEVERE DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT DECOMMISSIONING PROJECT 5 ENERGY AND EMISSIONS This section provides quantitative estimates of the energy use and atmospheric emissions from the proposed Guinevere installation decommissioning activities. The potential for environmental impact and mitigation measures to minimise emissions and optimise energy use are also assessed. 5.1 Regulatory Context Atmospheric emissions generated from the decommissioning of the Guinevere installation will be managed in accordance with current legislation and standards as detailed within Appendix A1. 5.2 Approach This energy and emissions assessment is based on the Institute of Petroleum (IoP) “Guidelines for the Calculation of Estimates of Energy Use and Gaseous Emissions in the Decommissioning of Offshore Structures” (IoP, 2000). The assessment includes: Identification of all structures to be decommissioned; Establishment of a materials inventory for each structure to be decommissioned; Identification of all operations associated with the decommissioning options (where operations are defined as all of the offshore and onshore activities associated with dismantling and transporting the components and recycling or treating any recovered materials); Identification of all end points associated with decommissioning each structure (end points are defined as the final states of the decommissioned materials); Identification of the associated activities that will be a source of energy expenditure and gaseous emissions for each operation and end point; and Selection of conversion factors and subsequent calculation of energy use and atmospheric emissions. The calculations predominantly use the energy use and atmospheric emission factors provided within IoP (2000) guidelines. In accordance with these guidelines, alternative factors may be used where specific equipment is considered to have a significantly different fuel use from that presented in the IoP database. The factors used for the energy and emissions calculations associated with the manufacture of new materials, recycling of materials, general fuel consumption and vessel fuel use are detailed in Appendix C. This section details the following sources, which were considered to have an associated impact on the energy and emissions at each stage of the Guinevere installation decommissioning. Helicopters for transportation of personnel; Vessels for transportation and offshore operations; Onshore dismantling and/ or processing materials; Onshore transportation to processing, recycling and landfill sites; Recycling; and New manufacture to replace recyclable materials decommissioned in situ or disposed of in landfill.
5.3 Assumptions and Calculation Factors The following sub-sections outline the assumptions relevant to the Guinevere installation decommissioning activities as a whole, and those assumptions specific to particular components of the installation. 5.3.1 General Assumptions For the calculation of the energy use and atmospheric emissions, the following assumptions were made. These are applicable to all the components of the Guinevere installation decommissioning operations. The estimates of energy use and gaseous emissions will contain an inherent uncertainty; IoP (2000) reports a typical inherent uncertainty of approximately 30 to 40%. However, the primary function of the IoP approach is to compare decommissioning options rather than to obtain absolute estimates of energy use and gaseous emissions. Care has been taken throughout this assessment to
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document the assumptions and ensure consistency of assumptions between and within components of the Guinevere installation decommissioning activities. As dismantling operations will be running concurrently, the Guinevere topsides and jacket estimates of energy and emissions have been assessed as one entity. A round trip by helicopter to the centre of the Guinevere area takes, approximately, half an hour from Norwich. A Sikorsky s-92 helicopter has been assumed for this assessment as it is one of the most commonly- used models in the North Sea (Bristow, 2017). This model is one of the largest (Bristow, 2017) and a single helicopter uses on average, 640 litres (1,412 pounds) of aviation fuel per hour (Senzig and Cumper, 2013). Energy use and gaseous emissions for helicopter use may therefore be an overestimate and represent a worst-case scenario. Energy use and emissions calculations for vessel use are based on a worst-case scenario of type of vessel used for the operations (i.e., where a number of vessels are being considered, the vessel with the highest fuel consumption has been assessed). Therefore, energy use and gaseous emissions for vessel use may be an overestimate and represent a worst-case scenario. Recovered material is assumed to be landed ashore in the Netherlands and subsequently taken to recycling and/or landfill sites at the dock location. The processing site is adjacent to the dock, so a an assumption has been made that the disposal, recycling and treatment site will be a maximum of 2 km return journey from the shipping yard. It is assumed that material is transported by lorry with a capacity of, approximately, 33 tonnes. Lorries are assumed to use, approximately, 0.46 litres of fuel per km (Defra & DECC, 2011) and are assumed to make a return trip from the landing site to the location of the disposal/ decontamination/ recycling facility. The energy use associated with the offshore and onshore deconstruction of materials is calculated according to the IoP factor for “overall dismantling” (IoP, 2000). This assumption has been made for two reasons. Firstly, there is inconsistency in the level of information provided by contractors on the fuel use of their deconstruction equipment. Secondly, there is an absence of published data on the deconstruction of different types of materials and components. Therefore an overall value is used to allow a comparison between this and other studies. A theoretical replacement value is calculated for recyclable material decommissioned in situ or disposed of in a landfill site. It should however be noted that the replacement of otherwise recyclable material is a theoretical activity designed to account for materials left in situ and is mainly used to achieve a balanced assessment when comparing decommissioning options. In reality it is unlikely that this activity will take place. This will therefore represent an overestimate of energy use and CO2 emissions. The energy use and atmospheric emissions associated with recycling and the manufacture of new materials are calculated for all materials for which standard factors are available.
5.3.2 Topsides Assumptions The following assumptions apply specifically to the decommissioning of the topsides: No material is decommissioned in situ. It has been assumed here, as a worst-case, that topsides and jackets will be decommissioned separately (i.e. two return trips to shore). All recovered material that can be re-used or recycled will be, where practical, and any remaining material will be sent to landfill. Recyclable material sent to landfill has been accounted for under “New manufacture to replace recyclable materials decommissioned in situ or taken to landfill”.
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There will be three helicopter flights per week during the vessel scope (this is a worst-case scenario and may lead to an over-estimate of the energy use and emissions associated with helicopter transport). Wait on Weather (WOW) contingency is applied to all vessels involved with the topsides removal.
5.3.3 Jacket Assumptions The following assumptions apply specifically to the decommissioning of the jackets: No material is decommissioned in situ above the seabed. All recovered steel, conductor and anode material from the jacket is recycled. Some steel will remain in situ below the seabed. This has been accounted for in the calculations for replacement of steel. There will be three helicopter flights per week during the vessel scope (this is a worst-case scenario and may lead to an over-estimate of the energy use and emissions associated with helicopter transport). Wait on Weather (WOW) contingency is applied to all vessels involved with jacket removal.
5.4 Materials and Operations Inventories The following section describes the materials inventory and vessel requirements for the decommissioning of the Guinevere installation. 5.4.1 Materials Inventory Inventories of materials are based on the summary of waste estimates (Table 2-3). 5.4.2 Vessel Use The vessel requirements expected for the decommissioning of the Guinevere infrastructure are summarised in Table 5-1. Table 5-1: Summary of vessel use during the decommissioning of the Guinevere installation Facility Recommended Decommissioning Vessel Use Relevant Decommissioning Method Section Option Topsides Complete removal Full removal via Jack Up for reuse, recycling single lift accommodation or final disposal barge (Seafox 1) onshore Cargo Barge Jacket Complete removal Full removal and HLV for reuse, recycling dismantled on Tugs (3), 5.5.1 or final disposal shore Stand-by vessel(s) onshore Supply vessel(s) Subsea Template Removal Removal and Survey vessel dismantling on shore
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GUINEVERE DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT DECOMMISSIONING PROJECT 5.5 Energy Use and Atmospheric Emissions Results Estimated energy use and atmospheric emissions during operations decommissioning the Guinevere installation are detailed within Tables 5-2 and 5-3, respectively. The greatest energy use can be attributed to vessel use and power generation, amounting to approximately 91% of the total energy use (Table 5-2). As a result, vessel and helicopter use is the significant contributor to CO2 emissions, contributing approximately 90% of the total CO2 value (Table 5-3). Table 5-2: Total energy use for the decommissioning of the Guinevere topsides and jacket
Decommissioning element Energy use (GJ) Approximate project percentage (%) contribution Vessel and helicopter use 251,397 91 Onshore transportation 1 0 Onshore deconstruction 1 1 Recycling 13,605 5 New manufacture to replace recyclable materials left in situ 7,709 3 or landfilled Total 274,845 100
Table 5-3: Total atmospheric emissions for the decommissioning of the Guinevere topsides and jacket
Decommissioning element Emissions (tonnes) Approximate project percentage (%) CO2 CO2 NOx SO2 CH4 contribution Vessel and helicopter use 18,644 342 23 1 90 Onshore transportation 0.1 0.001 0 ND 0 Onshore deconstruction ND ND ND ND 0 Recycling 1,445* 2* 6** ND 7 New manufacture to replace recyclable 579 1 2 0 3 materials left in situ or landfilled Total 20,668 345 31 1 100 Note: “ND” indicates that no data is available to enable a conversion to be made between a particular operation and the resulting gaseous emissions. Values have been rounded to the nearest whole number. *Includes emissions values for recycling steel and concrete (plastic and lead values not available). **Includes energy values for steel, concrete and plastic (lead values not available).
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5.6 Impacts on Sensitive Receptors Gaseous emissions from the proposed decommissioning activities include CO2, CH4, NOx, SOx and Volatile Organic Compounds (VOCs). These have the potential to impact sensitive receptors in the area as well as contribute to issues on a wider scale. The direct effects of the emission of CO2, CH4 and VOCs are the contribution to global climate change and regional air quality deterioration through low-level ozone production (CH4 has 21 times the global climate change potential of the main greenhouse gas CO2 (IPCC, 2007)). The indirect effects of low level ozone include deleterious health effects, as well as damage to vegetation, crops and ecosystems. The direct effect of NOx, SOx and VOC emissions is the formation of photochemical pollution in the presence of sunlight. Low level ozone is the main chemical pollutant formed, with by-products that include nitric and sulphuric acid and nitrate particulates. The effects of acid formation include contribution to acid rain and dry deposition of particulates. The main environmental effect resulting from the emission of SO2 is also the potential to contribute to the occurrence of acid rain; however, the fate of SO2 is difficult to predict due to its dependence on weather. The Guinevere installation is located approximately 116 km west of the UK/ Norwegian median line. Gases released from the offshore decommissioning activities is unlikely to be present in any measurable concentrations across the UK/ Norwegian median line. As the Guinevere installation is approximately 53 km north of the nearest UK coastline, it is very unlikely that any impact will be felt by any designated coastal or onshore conservation sites from offshore emissions. All four Annex II marine mammal species (bottlenose dolphin, harbour porpoise, grey seal and harbour seal) have been recorded in the vicinity of the Guinevere installation (see Section 3.4.6.2). In the open conditions that prevail offshore, the atmospheric emissions generated during the decommissioning activities would be quickly dispersed, and outside the immediate vicinity of decommissioning activities, all released gases would only be present in low concentrations. The atmospheric emissions from the proposed activities are therefore considered unlikely to have any effect on marine mammals. Potential impacts from onshore emissions are likely to be minor and within local and regional air quality criteria. The potential cumulative effects associated with atmospheric emissions produced by the decommissioning activities includes contribution to global climate change, regional acidification (acid rain) and local air pollution. The total annual CO2 emissions from offshore oil and gas UKCS operations during 2016 was 13.1 million tonnes. The estimated CO2 emissions released during the decommissioning of the Guinevere installation (20,668 tonnes) represent less than 0.2% of this total (Oil and Gas UK, 2017). Therefore, the atmospheric emissions from the Guinevere installation’s decommissioning activities are unlikely to have any effect on sensitive receptors
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GUINEVERE DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT DECOMMISSIONING PROJECT 5.7 Proposed Mitigation Measures Mitigation measures to minimise atmospheric emissions and energy consumption are detailed within Table 5-6. Table 5-6: Proposed mitigation measures
Energy and Emissions sources Proposed mitigation measure Vessels will be audited as part of selection and pre- mobilisation. All generators and engines will be maintained and operated to the manufacturers’ standards to ensure maximum efficiency. Vessels will use ultra-low sulphur fuel in line with MARPOL requirements. Vessel and helicopter use and onshore transportation Work programmes will be planned to optimise vessel time in the field Fuel consumption will be minimised by operational practices and power management systems for engines, generators and other combustion plant and maintenance systems. All mitigation measures will be incorporated into contractual documents of subcontractors.
5.8 Conclusions The operations for decommissioning the Guinevere installation (topsides and jacket) are predicted to use a total of 274,845 GJ of energy. Approximately 91% of this total can be attributed to vessel and helicopter use offshore.
A total of 20,668 tonnes of CO2 is expected to arise from the decommissioning of the Guinevere installation. The highest contributor to CO2 emissions is also represented by vessel and helicopter use offshore, which represents approximately 90% of total emissions. Emissions from the Guinevere installation decommissioning activities will contribute to global greenhouse gas emissions and have a non-significant cumulative and a negligible transboundary impact. Emissions will be minimised as far as is practicable. Total CO2 emissions generated by the proposed Guinevere installation decommissioning operations will represent a very small proportion (less than 0.2%) of the of the total annual CO2 offshore emissions from the UKCS in 2016 (Oil and Gas UK, 2017). Emissions from the Guinevere installation decommissioning activities will contribute to greenhouse gas emissions but will have a non- significant cumulative and transboundary impact.
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6 UNDERWATER NOISE Sound is important for many marine organisms with marine mammals, fish and certain species of invertebrates having developed a range of complex mechanisms for both the emission and detection of sound (Richardson et al., 1995). For example, cetaceans (whales, dolphins and porpoises) use sound for navigation, communication and prey detection. The introduction of anthropogenic underwater noise has the potential to affect the behaviour of, and in some cases injure, marine organisms. Underwater noise may cause animals to deviate from normal activities, potentially interrupting feeding, mating, socialising, resting or migration. This may impact body condition and reproductive success of individuals or populations (Southall et al. (2007); Richardson et al. (1995)). Feeding may also be affected indirectly if noise disturbs prey species (Southall et al. (2007); Richardson et al. (1995)). The proximity to the source of underwater noise is critical when evaluating the impact to marine species. Noise levels in the marine environment decline with increased distance from the source (dispersion in three dimensions) and through absorption by the water (Richardson et al., 1995). This section will consider the noise generated during the Guinevere installation decommissioning activities, and the potential impact on marine organisms. 6.1 Regulatory Context Under Regulations 41(1)(a) and (b) of the Conservation (Natural Habitats and c.) Regulations 1994 (as amended) and 39(1) (a) and (b) in the Offshore Marine Conservation (Natural Habitats, and c.) Regulations 2007 (amended 2009 and 2010), it is an offence to deliberately: capture, injure or kill any wild animal of a European Protected Species (EPS). disturb wild animals of any such species.
Disturbance of animals is defined under the Regulations and includes in particular, any disturbance which is likely to impair their ability to: Survive, breed, rear or nurture their young; or Hibernate or migrate (where applicable); or Significantly affect the local distribution or abundance of the species to which they belong.
In a marine setting, EPS include all the species of cetaceans (whales, dolphins and porpoises) (JNCC, 2010). As underwater noise has potential to cause injury and disturbance to cetaceans, an assessment of underwater noise generated by the decommissioning operations is required in line with guidance provided by the JNCC (JNCC, 2010). 6.2 Approach The impact of underwater noise on any sensitive receptors is assessed here using a modelling approach. There is a potential for certain decommissioning activities of the Guinevere installation to produce underwater noise resulting in environmental impacts. The primary noise sources associated with the proposed decommissioning operations, along with expected noise levels have been identified (Section 6.3). A review of sensitive receptors has been undertaken, and potentially significant impacts are identified based upon accepted thresholds (Section 6.4). Potential issues related to transboundary and cumulative impacts were also identified (Section 6.5). 6.3 Sources of Potential Impacts The sources of sound associated with the proposed decommissioning of the Guinevere installation will vary depending upon which options are selected to undertake the works. Following risk assessment (Section 4), the main potential sources can be identified as:
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Vessels, with inherent use of dynamic positioning, for transportation and to carry out decommissioning operations, and; The use of explosives for the cutting of well tubing during P&A operations; and Jacket cutting.
The typical level and frequency of sound generated by each source was obtained from published studies (reviewed by Genesis (2011)) and summed accordingly to generate a cumulative sound level. Using the modelling approach, sound propagation from the source was determined using the Marsh- Schulkin model (Schulkin and Mercer, 1985) and the worst-case scenario as detailed above, was used throughout. This model applies to acoustic transmission in shallow water (up to, approximately, 185 m) and represents sound propagation loss in terms of sea state, substrate type, water depth, frequency and the depth of the mixed layer. In order to model the worst-case scenario, it was assumed that all sources will operate at all times during each activity. In reality, this is unlikely, and the source level is likely to be lower than predicted within this assessment. 6.3.1 Vessels Most oil and gas decommissioning activities are typically dominated by vessel noise which is continuous and not captured within the Marine Safety Framework Directive (MSFD) descriptor for loud, low and mid- frequency impulsive sounds. Broadband source levels for these activities rarely exceed about 190 dB re 1 μPa m and are typically much lower (Hannay & MacGillivray (2005); Genesis (2011)). Whilst continuous noise can mask biologically relevant signals such as echolocation clicks, the sound levels are below the threshold levels for Temporary Threshold Shift (TTS) (a temporary hearing loss) in cetaceans, according to the Southall et al. (2007) criteria (Genesis, 2011). The level and frequency of sound produced by vessels is related to vessel size and speed, with larger vessels typically producing lower frequency sounds (Richardson et al., 1995). Noise levels depend on the operating status of the vessel and can therefore vary considerably over time. In general, vessels produce noise within the range 100 Hz to 10 kHz, with the strongest energy over the range 200 Hz to 2 kHz. Based upon previous studies, it is anticipated that the subsea noise levels generated by surface vessels used during the decommissioning phase are unlikely to result in physiological damage to marine mammals. Depending on the ambient noise levels, sensitive marine mammals may be locally disturbed by noise from a vessel in its immediate vicinity, however, the impact is not expected to be significant. Various combinations of vessels will be on site during the decommissioning operations and for the purposes of modelling it has been assumed that a maximum of eight will be operating in the area at any one time. Source levels resulting from a previous study (Hallett (2004)) giving the average of ten merchant ships (lengths 89 to 320 m, average 194 m) during entry or exit to port were used as a basis for this assessment; note that the standard deviation around the mean source level was given as 5 to 10 dB. This data is more conservative than many of the published examples for specific construction and support vessels. For continuous sound such as shipping noise, it is usual to use a measure of the total sound intensity of a signal (rms). However, the larger zero-to-peak values have been used in the modelling to illustrate the worst-case scenario.
6.3.2 Use of Explosives during Well P&A The production tubing was recovered from each well and required to be cut using an explosive charge, the depth of the cuts were 2,396m in G1 and 2,725m in G2. One explosive charge per well was used to cut the tubing. The explosive charge used for each tubing cut contained 0.052kg of HMX. Explosives were also required to perforate the production casing to create a circulation path required for the placement of the
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GUINEVERE DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT cement plugs. Perforations were made at 244m in G1 and 305m in G2. The explosive charges used for each perforation contained 0.56kg of HMX Each explosive assembly was deployed using slickline. The charge was run in hole (RIH) to the required depth inside the production tubing/casing and after detonating, the downhole assembly was recovered from the well using the slickline winch. A new explosive bottom hole assembly (BHA) was prepared before deploying for the next explosive operation. Each explosive charge used in the wells was detonated one at a time. The charge was positioned inside the tubing and/or casing, which was encased by the outer production casings, which ran from the depth of the explosion to the platform deck. The tubing and inner casing strings were fully contained within the outer casing. At no time before or after the cut were the charges open to the sea. All explosives operations were carried out from the Guinevere NUI and was supported by the Seafox 1 jack- up barge and a support vessel. A chemical explosion starts with an extremely rapid reaction that generates a large volume of high pressure, superheated gas. The pressure difference across the gas-water interface causes a shock wave, which moves outward at speeds greater than the speed of sound in seawater (~1,500 ms-1). The shock wave consists of a nearly instantaneous increase in pressure, which then rapidly decays. As peak pressures increase, so does the speed of the shock wave. The peak pressure in the shock wave increases as the weight of the explosive increases and will decrease as the shock wave moves away from the source (BMT Cordah, 2017a). The hot gases from the chemical explosion also create a large, oscillating gas bubble in the water. The shock wave and the gas bubble each contain, approximately, half of the energy produced by the explosion. After the gas bubble is formed, it expands until the pressure inside the bubble is lower than the surrounding pressure. At that point the bubble begins to collapse, causing the pressure inside to increase. This increase in pressure eventually causes the bubble to stop collapsing and to expand again. Pressure pulses are generated when the bubble begins to expand from its minimum volume. This bubble oscillation continues and creates a series of pressure pulses called bubble pulses. Each successive pulse is weaker than the preceding one. The peak pressure of the second bubble pulse is only about of fifth of that of the first bubble pulse (BMT Cordah, 2017a). Explosions create a pressure impulse with a sharp rise time that is relatively broadband in frequency, including low-frequency energy. They generally have high source levels. The spectral and amplitude characteristics of explosions vary with the charge weight and the detonation depth. Parvin et al (2007), summarises a series of source peak pressure values derived from detonations of explosive charges freely suspended in the water column. Three of these examples are as follows: For a charge of mass 4,540 kg this gives a source peak pressure of, approximately, 300 dB re 1 µPa m; For a typical charge used for well head separation (circa 40 kg), source peak pressure values of around 285 dB re 1 µPa m are typically seen; and For smaller charge weights typical of those used during human and animal exposure experiments, the source peak pressure value for a 2.27 kg charge is in the region of 276 dB re 1 µPa m.
Nedwell and Edwards (2004) found that peak pressure levels recorded during wellhead decommissioning were similar to those for similar explosive charges fired unconfined in the water. The charge was inserted into a casing and was lowered to between two and three metres below the mud line (seabed). Nedwell and Edwards (2004) suggested that the pipework surrounding the charge and the sediment below which the charge detonated did not act as an effective confinement for the blast because of the following behaviours:
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Firstly, the pipework surrounding the charge is in close proximity to the explosives and hence the forces acting on it are extremely high when compared with the pipe burst pressure; and Secondly, the sediment adjacent to the pipe may be expected to be of comparable density to the adjacent water. Hence the explosive energy will couple into the water in a similar way as it would when fired unconfined.
Nedwell and Thandavamoorthy (1989) observed that during borehole blasting in rock, the peak pressure levels are typically 10% or less than those for unconfined charges. However, better confinement of the explosive energy and losses caused by explosive products venting through fragmented rock account for the lower levels, thus providing an additional efficient loss mechanism. The acoustic impact of the buried charge explosion can vary significantly depending on the sediment composition and could range from an essentially waterborne detonation to a completely confined shot with no venting of explosion gases into the water column (Continental Shelf Associates, 2004). The presence of the metal casing surrounding the tubing may act as containment and may absorb a portion of the explosive energy. However, there is some evidence that the extremely high detonation forces in close proximity to the charge far exceed the strength of metal structures in these cases, resulting in negligible influence (Continental Shelf Associates, 2004). Generally, it is safe to assume that ignoring the effects of the structure will yield a conservative “worst-case” assessment of the impact from the detonation. The explosive cutting generates impulsive noise and the impact from this will likely dominate any continuous noise sources, such as from vessels. 6.3.3 Jacket Cutting The jacket members and associated caissons, conductors and risers will be severed internally at the seabed using either diamond-wire cutting or abrasive water jetting tools. If this is not possible, the jacket members will be severed externally using the same methods and an ROV. Underwater noise from jacket cutting is expected to be temporary and short-term. No studies are currently available in the literature referring to noise assessments from jacket cutting. However, it may be possible that any target species in the immediate vicinity at the time of cutting activities could be temporarily disturbed. 6.3.4 Ambient Noise Ambient or background noise in the ocean results from sounds generated by physical factors such as wind and waves; by marine mammal vocalisations; and by other shipping. DEWI (2004) reported on ambient noise measurements from five different locations in the North Sea and this data has been used as a basis for comparison in the current study. 6.4 Potential Impact on Sensitive Receptors Underwater noise can affect the behaviour of, or may cause injury to, several different marine taxa, in particular marine invertebrates, fish and marine mammals such as pinnipeds and cetaceans. Behavioural changes will vary from a minor change in direction to confusion and altered diving behaviours, which may have varied medium and long-term effects on the individual. One of the most critical issues in relation to behavioural effects of sound on marine mammals and fish is whether anthropogenic sound interferes with, or masks, the ability of the animal to detect and respond to biologically relevant sounds (Popper et al., 2014). In effect, masking raises the threshold for detection by an animal and the degree of masking is related both to the level of the masking noise and the frequencies that it contains. 6.4.1 Marine Invertebrates There have been few studies of the effects of underwater noise on marine invertebrates (Hawkins et al, 2014; Morley et al., 2013; Cheesman et al., 2012). Roberts et al. (2016) found that anthropogenic substrate- borne vibrations resulting from noise pollution have a clear effect on the behaviour of a common marine crustacean, Pagurus bernhardus. They suggested that further research is required to understand the long
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GUINEVERE DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT term effects of underwater noise on marine crustaceans. Hence, although marine invertebrates may be affected by the decommissioning activities, there is insufficient knowledge currently available to be able to make an assessment. 6.4.2 Fish Many species of fish use sound for location of prey, avoidance of predators and for social interactions. The inner ear of fish including elasmobranchs (sharks, skates and rays) is very similar to that of terrestrial vertebrates, and hearing is understood to be present among virtually all fish (NRC, 2003). The sensory systems used by fish to detect sounds are very similar to those of marine (and terrestrial) mammals and hence sounds that damage or in other ways affect marine mammals could have similar consequences for fish. In considering the impact of anthropogenic sounds upon fish, it is useful to place fish into different functional categories, depending on their structure and degree of hearing specialisation (Popper et al., 2014; Cheesman et al., 2012). Fish may tentatively be separated into: Category I - Fish with no swim bladder or other gas volume (particle motion detectors); Category II - Fish with a swim bladder or other gas volume, and therefore susceptible to barotrauma, but where the organ is not involved in hearing (particle motion detectors); and, Category III - Fish with a swim bladder or other gas volume, and therefore susceptible to barotrauma, where the organ is also involved in hearing (sound pressure and particle motion detectors).
Fish species vary in many ways, anatomically, physiologically, ecologically and behaviourally in their response to sound, such that a guideline for a behavioural response can never fit all fish (Popper et al., 2014). Many finfish species in response to anthropogenic noise display an alarm of tightening schools, increased speed and moving towards the seabed (Fewtrell and McCauley, 2012; McCauley et al., 2003). Most fish respond to the particle motion component of sound waves whereas marine mammals do not. Animals near the seabed may not only detect water-borne sounds, but also sound that propagates through the substrate and re-enters the water column (Popper et al., 2014). Reviews on the effects of anthropogenic sound on fishes concluded that there are substantial gaps in the knowledge that need to be filled before meaningful noise exposure criteria can be developed (Popper et al., 2014; Popper and Hastings, 2009). However, injury thresholds have been proposed for Category II and III fish (> 207 dB re 1 µPa m) and Category I fish (> 213 dB re 1 µPa m) (Popper et al., 2014). 6.4.3 Pinnipeds Pinnipeds (seals, sea lions and walruses) also produce a diversity of sounds, although generally over a low, restricted bandwidth (generally from 100 Hz to several tens of kHz). Their sounds are used primarily in critical social and reproductive interactions (Southall et al., 2007). Available data suggest that most pinniped species have peak sensitivities between 1 and 20 kHz (NRC, 2003). However, the data available on the effects of anthropogenic noise on pinniped behaviour are limited. Grey seals and harbour or common seals are resident in UK waters and occur regularly over large parts of the North Sea (SMRU, 2001). Both species are found predominantly along the UK coastline but there are few data available on the distribution and abundance of seals when offshore. Tracking of seals suggests they make feeding trips lasting two to three days, with the animal ultimately returning to the same haul- out site from which it departed (SMRU, 2001). The Guinevere installation is within, approximately, 75 km of several high density and haul-out sites including the Humber Estuary, Donna Nook and The Wash (Section 3.4.5.2; Figure 3-7) hence they may be travelling to feed in the vicinity of the proposed decommissioning activities (NMPI, 2018). 6.4.4 Cetaceans Cetaceans use sound for navigation, communication and prey detection. Anthropogenic underwater noise has the potential to impact on marine mammals (JNCC (2010); Southall et al. (2007); Richardson et al. (1995)). Several species of cetacean have been recorded in the Guinevere Field area, namely minke whale,
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GUINEVERE DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT long-finned pilot whale, bottlenose dolphin, common dolphin, white-beaked dolphin, white-sided dolphin and harbour porpoise with the most sightings occurring in the summer months (Reid et al., 2003; UKDMAP, 1998; Table 3-2). The Guinevere installation is also located 4 km from the boundary of the Southern North Sea cSAC (Figure 3-9), which is designated as an area of importance for harbour porpoise. Harbour porpoise are listed under Annex II of the EC Habitats and Species Directive as species whose conservation requires the designation of SACs (JNCC, 2017h). During operations, harbour porpoise are expected to be present in low to very high numbers in the immediate vicinity of the Guinevere installation (Table 3-7). 6.4.4.1 Characterisation of hearing sensitivities Currently available data (via direct behavioural and electrophysiological measurements) and predictions (based on inner ear morphology, modelling, behaviour, vocalisations, or taxonomy) indicate that not all marine mammal species have equal hearing capabilities in terms of absolute hearing sensitivity and the frequency band of hearing (NOAA, 2015). Consequently, vulnerability to impact from underwater noise differs between species. Southall et al. (2007) classified the “hearing types” of different marine mammal species (Table 6-1).
Table 6-1: Functional cetacean hearing groups
Species sighted in the Guinevere Cetacean functional hearing Estimated auditory Field area (Quadrant 48 and group Bandwidth surrounding quadrants) Minke whale Low-frequency 7 Hz – 25 kHz Long-finned pilot whale White-beaked dolphin Atlantic white-sided dolphin Mid-frequency 150 Hz – 160 kHz Bottlenose dolphin Common dolphin High-frequency 200 Hz – 180 kHz Harbour porpoise Grey seal Pinnipeds in water 75 Hz – 100 kHz Common seal Grey seal Pinnipeds in air 75 Hz – 30 kHz Common seal Source: Southall et al. (2007); UKDMAP (1998); NOAA (2015)
In addition, audiograms were obtained for harbour porpoise, bottlenose dolphin, grey and common seals (Nedwell et al., 2004) and for white-beaked dolphin (Nachtigall et al., 2008). A generalised mysticetes (baleen whale) audiogram was obtained and assumed to represent the hearing ability of long-finned pilot whales and minke whales (Tech Environmental, 2006). No audiograms are available for Atlantic white-sided dolphins. However, an audiogram is available for another member of the same genus as the Atlantic white- sided dolphin, the Pacific white-sided dolphin (Lagenorhynchus obliqidens) (Tremel et al., 1998); and it has been assumed that members of this genus may have similar hearing characteristics. Note that no audiograms are available for common dolphin. 6.4.4.2 Thresholds for injury and disturbance to marine mammals The noise level perceived by an animal (the “received noise level”) depends on the level and frequency of the sound when it reaches the animal and the hearing sensitivity of the animal. In the immediate vicinity of a high sound level source, noise can have a severe effect causing a permanent threshold shift (PTS) in hearing, However, at greater distance from a source the noise decreases and the potential effects are diminished (Nedwell et al., 2005; Nedwell and Edwards, 2004a), possibly causing the onset of a temporary shift in hearing thresholds (TTS-onset). As noted above, hearing sensitivity, in terms of the range of
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GUINEVERE DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT frequencies and sound levels that can be perceived, varies with species. The minimum level of sound that a species is able to detect (the hearing threshold) varies with frequency. Southall et al. (2007) undertook a review of the impacts of underwater noise on marine mammals and used this to define criteria for predicting the onset of injury and behavioural response in marine mammals with different hearing characteristics (Table 6-3) when subjected to different types of noise (Table 6-2). The estimated bandwidths have been revised recently by NOAA (NOAA, 2015). This distinction between noise types is required as single and multiple noise exposures at different levels and durations differ in their potential to cause injury to marine mammals. This led Southall et al. (2007) to propose a set of precautionary thresholds for peak sound pressure levels (SPL) and sound exposure levels (SEL) that are likely to lead to injury (PTS) and disturbance to marine mammals for different noise types (Table 6-3). Southall et al. (2007) recommend assessing whether a noise from a specific source could cause disturbance to a particular species by comparing the circumstances of the situation with empirical studies reporting similar circumstances. JNCC (2010), in their guidance on how to assess and manage the risk of causing “disturbance” to a marine EPS as a result of activities at sea, suggest that marine mammal disturbance is likely to occur from sustained or chronic behavioural response with a severity scoring of five or above according to the scale of Southall et al. (2007). The severity scaling system which ranks the behavioural response from a zero for ‘no response’ to a nine for ‘outright panic, flight, stampede, attack of conspecifics or stranding events’. A behavioural response with a severity scale of five/ six is considered to represent a disturbance, with animals showing noticeable changes in swimming pattern to minor avoidance reactions. These sound thresholds are compared with the predicted sound levels generated by the decommissioning operations to estimate a distance from the activities within which disturbance may occur. Table 6-2: Functional cetacean hearing groups
Noise type Definition* Decommissioning activities Single-pulse Brief, broadband, atonal, transient, single discrete noise NA events; characterised by rapid rise to peak pressure Multiple-pulse Multiple pulse events within 24 hours NA Non-pulse Intermittent or continuous, single or multiple discrete Vessel activity, rock- acoustic events within 24 hours; tonal or atonal and placement, well P&A, without rapid rise to peak pressure underwater cutting *Source: Southall et al. (2007)
Table 6-3: Precautionary thresholds for injury or disturbance to cetaceans
Functional Sound Injury threshold for different sound Disturbance threshold for single hearing measure1 types pulse sounds2 group Single- Multiple Non-pulse Single- Multiple- Non-pulse pulse pulse pulse pulse Low- SPL 230 230 230 224 - - frequency cetaceans SEL 198 198 215 183 - - Mid- SPL 230 230 230 224 - - frequency cetaceans SEL 198 198 215 183 - - High SPL 230 230 230 224 - - frequency SEL 198 198 215 183 - - cetaceans Pinnipeds SPL 218 218 218 212 - - (in water) SEL 198 198 215 171 - -
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Functional Sound Injury threshold for different sound Disturbance threshold for single hearing measure1 types pulse sounds2 group Single- Multiple Non-pulse Single- Multiple- Non-pulse pulse pulse pulse pulse Pinnipeds SPL 149 149 149 109 - - (in air) SEL 144 144 144.5 100 - - Notes: 1In water: SPL – zero-to-peak Sound Pressure Level in dB re 1 µPa; SEL – Sound Exposure Level in dB re 1 µPa2s. In air: SPL – zero-to-peak Sound Pressure Level in dB re 20 µPa; SEL – Sound Exposure Level in dB re 20 µPa2s. Applies to Pinnipeds (in air) only. 2Southall et al., 2007 did not define thresholds for disturbance from multiple pulse and non-pulse sounds. (See text for details)
6.4.4.3 The dBht(species) alternative approach The work of Southall et al. (2007) gives a broad indication of suitable sound thresholds for behavioural responses and injury, these can be further clarified by consideration of the alternative approach of Nedwell et al. (2007). Nedwell et al. (2007) suggest that all species with well-developed hearing are likely to avoid sound when the level exceeds 50 to 90 dB above their hearing threshold and receive damage to hearing organs at 130 dB above their hearing threshold. Species-specific audiograms are used to filter received noise levels according to the hearing ability of a species, giving sound levels in dBht(species) (loudness of the sound perceived by that species). The distance from the centre of operations to the points at which 130 dBht(species) and 90 dBht(species) are exceeded represents an estimate of the limits within which injury (PTS) and likely avoidance might be expected, respectively.
6.5 Noise Impact Assessment
Underwater sound is characterised with reference to two metrics; its frequency measured in Hertz (Hz) and the sound or intensity of the sound measured in decibels (dB). Sound manifests itself as pressure (i.e. a force acting over a given area). It is expressed in terms of SPL, which use a logarithmic scale of the ratio of the measured pressure to a reference pressure (expressed as decibels relative to one micro‐Pascal (dB re 1 μPa)). SPLs are quoted at a standard range from the source, usually one metre (dB re 1μPa at 1 metre). Sound frequency is an important characteristic of the source noise. High frequency sounds are attenuated in seawater more quickly than low frequency sounds: for example, a 100 Hz sound may be detectable after travelling hundreds or even thousands of kilometres, whereas a 100 kilohertz (kHz) sound may travel for only a few kilometres (Swan et al., 1994; MMC, 2007). Underwater sounds spread spherically from the noise source to a range approximately equal to water depth. This is followed by the cylindrical spreading of sound waves (FAS, 2010). As sound spreads underwater, it decreases in intensity (attenuates) with distance from the source. The rate of attenuation is affected by a number of factors including sound absorption or scattering by organisms in the water column, reflection or scattering of the sound wave at the seabed (which varies depending on sediment type), water temperature, stratification, salinity and weather (Munk and Zachariasen, 1991; Richardson et al., 1995). Various models for calculating the propagation of underwater sound have been proposed. The model proposed by Richardson et al. (1995), which assumes spherical spreading, is the most widely used, and is shown below: Transmission Loss = 20Log(R/R0) dB Spherical spreading is assumed. R0 = the reference range, usually 1 metre. R = the distance from the reference range.
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This provides a measure of sound given to a 1‐metre reference distance but is based on a number of assumptions; sound transfer is through a homogenous medium (i.e. no attenuation due to variations in temperature, salinity, bathymetry etc.) and infinite space for the sound wave to spread. This method provides a conservative estimate of sound propagation with distance as it struggles to extrapolate sound attenuation in the near field (within tens of metres of the noise source), due to interference between sound waves and reverberation and therefore generally overestimates transmission of sound from the source. As such, it is considered sufficient to examine a ‘worst‐case’ scenario for noise impacts on marine fauna and has been used to assess the potential effects of underwater noise from the proposed operations.
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6.5.1 Potential Impact on Fish Figure C.1. Sound Propagation in Water from the Use of Explosives (assuming spherical spreading) Against Fish Injury Criteria in relation to Single‐Pulse Noise (after Popper et al., 2014)
6.5.2 Potential Impact on Marine Mammals Figure C.2. Sound Propagation in Water from the Use of Explosives (assuming spherical spreading) Against Marine Mammal Injury and Significant Behavioural Disturbance Criteria in relation to Single‐ Pulse Noise (after Southall et.al. 2007)
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6.6 Cumulative and Transboundary Impacts The Guinevere installation is located, approximately, 116 km from the UK/ Netherlands median line. At this distance, noise levels from explosive cuttings, the greatest source of sound associated with the Guinevere installation decommissioning activities would attenuate to a level lower than that likely to cause temporary displacement to any cetacean species. Therefore, there is unlikely to be a transboundary impact from the noise generated by the decommissioning activities. The Guinevere installation is located in the SNS gas basin which is currently home to over 150 installations (Section 3; Oil and Gas data, 2017). The closest installations are the Excalibur platform (7.3 km to the northeast) and the Waveney platform (7.3 km to the south) with three other platforms and two wind farm locations within 20 km (Table 3-14). Despite the proximity of the proposed work to other installations, the noise decommissioning activities will be restricted temporally (work will be undertaken in short bursts) and spatially (within a maximum radius of 1 km), no cumulative impacts (resulting from cumulative sound sources) are anticipated with other oil and gas or renewables activities. There is a possibility for future aggregate extraction close to the Guinevere installation location (Outer Dowsing dredging area (515/2) is located 3.5 km to the west); however the associated cumulative impact would be limited. Source levels at frequencies below 500 Hz from dredger vessels are generally in line with those expected for a cargo ship travelling at modest speed (MALSF, 2011). Of note is that the elevated broadband noise is dependent on the aggregate type being extracted (gravel generating higher noise levels than sand) (MALSF, 2011). 6.7 Proposed Mitigation Measures PUK operates within a Safety and Environmental Management System (Section 11) that applies to all oil and gas activities. The proposed activities described in this submission will be carried out in accordance with this management system and with PUK’s policy and procedures. Mitigation measures, in accordance with JNCC guidelines (JNCC, 2010) where available, will be implemented during the proposed decommissioning operations as appropriate (Table 6-7). The JNCC (2010b) guidelines for minimising the risk of injury and disturbance to marine mammals from the use of explosives will be implemented throughout any relevant noise generating operations. Two Marine Mammal Observers (MMObs) will be on the vessel. A minimum monitoring zone of 1 km around the explosive source will be established (Table 6-8), although the final radius of the mitigation zone will be decided following consultation with JNCC. Vessel activity is in general not considered by JNCC (2010) to pose a high risk of injury or non-trivial disturbance. The noise impact assessment undertaken supports this view, showing that there is unlikely to be any significant impact on any marine species. It is therefore considered unlikely that further mitigation measures, beyond those naturally adopted from PUK’s Safety and Environmental Management System, policy and procedures, will be required. Mitigation measures, in accordance with JNCC guidelines (JNCC, 2010) where available, will be implemented during the proposed decommissioning operations as appropriate (Table 6-4). Table 6-4: Proposed mitigation measures
Potential source of Proposed mitigation measures impact Underwater noise from Machinery and equipment will be in good working order and well-maintained. construction The number of vessels utilising dynamic positioning will be minimised. activities
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Potential source of Proposed mitigation measures impact Accurately determine the amount of explosive required so that the amount is proportionate to the activity and not excessive. Plan the sequence of multiple explosive charges so that, wherever possible, the smaller charges are detonated first to maximise the ‘soft-start’ or ‘ramp up’ effect. Only commence explosive detonations during the daylight hours and good visibility (observers should be able to monitor the full extent of the mitigation zone). Plan explosive detonations so that the scheduling will reduce the likelihood of encounters with marine mammals. For example, this might be an important consideration in certain areas/ times, e.g. during seal pupping periods near SACs for common seals or grey seals Using trained MMO personnel, commence pre-shooting searches for marine mammals at least one hour prior to detonation. This search will be undertaken within a mitigation zone of at least 1,000 m radius around the operations, leading to a delay in detonation if marine mammals are detected. Use trained Passive Acoustic Monitoring (PAM) operatives to deploy and monitor Underwater hydrophones1 in the water column to detect vocalising marine mammals, also noise from leading to a delay in detonation if marine mammals are detected within the explosive mitigation zone. sources Explosive detonations should not be undertaken within 20 minutes of a marine mammal being detected within the mitigation zone. If a marine mammal is observed, or acoustically detected, within the mitigation zone, it should be monitored and tracked until it moves out of range. If the marine mammal is not detected again within 20 minutes, it can be assumed that it has left the area and the detonation may commence. If an animal has been detected acoustically, the PAM operative should use a range indication and their judgement to determine whether the marine mammal is within the mitigation zone. Use Acoustic Deterrent Devices which have the potential to exclude animals from the shooting area. Continue pre-detonation search and soft-start to cover any breaks in shooting. Report shooting activity and any marine mammal detections via the MMO report submitted upon completion to JNCC. Machinery and equipment will be in good working order and well-maintained. The number of vessels utilising dynamic positioning will be minimised.
Notes: 1. PAM equipment can be used with reasonable effectiveness during mitigation for some cetacean species. The harbour porpoise and other small odontocetes (e.g. porpoise species and Cephalorhynchus dolphins) are known to emit regular high-frequency echolocation clicks. If these clicks are detected, then animals are generally within a few hundred metres of the PAM system. However, research has shown that aside from these species, the use of PAM equipment for mitigation purposes for other cetaceans should not be considered to represent a reliable sole method but rather supplementary to the use of MMOs (MMOA, 2012). 6.8 Conclusions Perenco is planning to undertake decommissioning activities at the Guinevere installation. Records indicate previous sightings of up to seven cetacean and two pinniped species within the study area during the year. These species are all subject to regulatory protection from injury and disturbance.
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The predicted cumulative source sound levels during the decommissioning operations involving explosive cutting is 276 dB re 1 µPa m; and is 198 dB re 1 µPa m with vessels only. The source sound level for explosive cutting exceeds the threshold for injury to cetaceans as detailed in Southall et al. (2007). Fish may be injured up to 6.7 km away from the explosive source. Mid frequency cetaceans should not be injured or display significant behavioural displacement within a default 1 km explosives mitigation monitoring zone. The modelling suggests that it is possible that high frequency cetaceans such as harbour porpoises may be injured or display significant behavioural displacement, within about 10.9 km or 17.8 km of the explosive source, respectively. However, it should be noted that the modelling is based on a highly conservative worst-case scenario of an unconfined blast at the seabed. In reality, the explosive source will be confined within the tubing, approximately 244 m below the mudline. It is anticipated that the energy and impacts associated with the explosives downhole at the Guinevere wells will be significantly less than those indicated by the worst-case scenario modelled within the water column. The subsea noise levels generated by surface vessels used during the decommissioning operations are very unlikely to result in physiological damage to marine mammals. Depending on ambient noise levels, sensitive marine mammals may be locally displaced by noise from a vessel in its immediate vicinity, or by any other continuous noise source during the decommissioning activities at the Guinevere Field. However, the predicted impact is not expected to be significant. There has been a high (September and November) to very high (August) level of marine mammal sightings in blocks adjacent to the Guinevere field during the proposed period of explosive decommissioning operations, with harbour porpoise sightings recorded as very high in August and high in September. As the Guinevere Installation is located around 53 km north of the nearest UK coastline, it is likely that grey and common seals would be regularly found in the vicinity of the proposed development.
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7 SEABED IMPACTS The following section discusses the potential short- and long-term environmental impacts associated with seabed disturbance resulting from the proposed Guinevere installation decommissioning activities. The measures planned by PUK to minimise these impacts are detailed in Section 7.8. 7.1 Regulatory Context Seabed disturbance resulting from the proposed decommissioning activities will be managed in accordance with current legislation and standards, as detailed within Appendix A. 7.2 Approach The Guinevere installation decommissioning activities will require work below, at or near the seabed, which may result in either short- or long-term disturbance to the seabed sediments and marine organisms. The extent of any disturbance, combined with the seabed type and hydrodynamic conditions during the activities, will determine the burial and smothering from suspended sediments and any direct impact to species or habitats, as described in Table 7-1. Table 7-1: Summary of potential sources of seabed disturbance and resultant environmental impacts
Environmental impact Decommissioning activity Suspended Release of Burial and Change in sediments contaminants smothering habitat Full removal of topsides Short-term - Long-term* Long-term* Full removal of jacket Short-term - Long-term* Long-term* *Only deemed a long-term impact if rock-protection is used for stabilisation of accommodation and lift vessels. This is not anticipated but is considered here as a worst-case scenario. 7.3 Sources of Potential Impacts The following activities represent worst-case scenarios that will potentially impact the seabed at the Guinevere installation: Anchoring and positioning of a jack-up accommodation unit (Seafox 1) adjacent to the Guinevere installation during well plugging and abandonment (P&A) and preparatory activities (short and potential long-term impacts); and Positioning of lift vessel on the seabed and the removal of the topsides and jacket (short and potential long-term impacts).
7.3.1 Anchoring and Positioning of Jack-Up Accommodation Unit Both the seabed sediments and benthos will be impacted by the placement of the Seafox 1 Jack-up accommodation and multi support unit. Upon commencement of preparatory and P&A operations, the Seafox 1 will be located to its working position adjacent to the Guinevere installation. There will be a seabed impact from the Seafox 1 spudcans, anchors and anchor chains. No rock stabilisation was required during previous deployment of the Seafox I in the area adjacent to the Guinevere installation. It is therefore not considered to be a potential contributor to the overall seabed impact associated with the Seafox I. Rock placement for stabilisation will only be required if seafloor instability is encountered during a debris survey and is discussed here on a worse-case assessment basis. Anchors and anchor chains will be used to relocate the Seafox 1 from its stand-off position (out-with the Guinevere installation’s 500 m safety zone) to its operational position. The maximum deployment time of the anchors (weather permitting) will be, approximately, 24 to 36 hours, after which they will be fully recovered and stowed. No additional seabed impacts are associated with the deployment and recovery of either the anchors or anchor chains.
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The worst-case seabed disturbance associated with the Seafox 1 positioning is presented in Table 7-2. As a worst case scenario, the length of each chain was assumed at 441 m, but in reality, the chains will be between 395 and 441 m long, and only part of the length of these chains will be in contact with the seabed (Perenco, 2017a; Figure 7-1). Table 7-2: Seafox 1 working position and potential seabed disturbance Position Total seabed impact Location Description of Disturbance Name (km2) Anchors – (2.586 m x 2.345 m) x 4 anchors 0.00002
Latitude: Anchor chains – ((0.076 m chain diameter 0.007 + 4 m to allow for scour corridor) x 441 m Working 53˚ 24’ 53.279” N length) x 4 chains position Longitude: Spud cans – 4 x 22 m2 0.00009 01˚ 16’ 24.375” E
Total 0.007
7.3.2 Jacket Removal The weight (in air) of the Guinevere jacket is less than 10,000 t and therefore it falls within the OSPAR 98/3 category of steel structures for which derogation cannot be sought. Therefore, the only decommissioning option available for the installation is full removal, as presented in Section 2. The four piles on the jacket will be cut internally using high pressure water abrasion and removed to, approximately, 3 m below the seabed. If the internal cutting operations encounter problems, excavation of an area around each jacket pile may be required. During excavation, sediment would be excavated by a work class ROV and would be deposited down-current of the jacket piles to undergo natural dispersal with minimal/ short-term impact on the surrounding seabed area. Excavation of the footings has therefore been considered as a worst-case scenario. Excavation of the footings would impact a maximum seabed area of approximately 0.0006 km2 (Table 7-3). Due to the relatively coarse sediment characteristic of the seabed in this area (Section 3) dispersion of the sediment and any remaining drill cuttings is expected to be rapid. The cut jacket will be removed from the seabed in a single lift and transported to shore by lift vessel for dismantlement, disposal and recycling. Table 7-3: Structures and materials with potential to impact on the seabed – jacket removal pile excavation
Structure Dimensions Total seabed impact (km2) Guinevere jacket 154 m2 x 4 piles 0.0006 Jacket removal total 0.0006 Note: Jacket removal assumptions based on a worst-case scenario excavation of a 14 m diameter pit (1.54 x 10-4 km2) around each platform pile
7.3.3 Jack-Up Lift Vessel The vessel contract for the removal of the topsides and jacket has yet to be awarded; it is possible that a jack-up lift vessel will be contracted. To represent a worst-case scenario, calculations have been based on: A large lift vessel supported on seabed by six spud cans.
As with the Seafox – 1 above, stabilisation material (rock-placement) will only be required if seafloor instability is encountered during a debris survey. In accordance with HSE guidelines for jack-up rigs (with particular reference to foundation integrity (HSE, 2004)) placing gravel, rock or geotextiles onto the site to prevent scour damage is recommended. PUK will not know if rock-placement is required in order to
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GUINEVERE DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT prevent scour damage until the lift vessel has arrived on location. Whilst it is not anticipated that stabilisation material will be required and it will be avoided where possible, it cannot be ruled out. If required, the rock would be placed at six locations on the seabed as rock berms to support the six jack-up legs. The amount of rock required (and therefore footprint) is dependent on local bathymetry and sediment structure at the installation. The seabed at the Guinevere installation is characterised by a mobile sand streaks, which are actively transported across the seabed, with mobile sand waves (Bibby HydroMap, 2017b). As such it is difficult to predict whether rock-placement will be required during operations. Should rock placement be required, updates to marine licence will be submitted to BEIS to seek approval for the operation. This update will specify the proposed volume of rock and site-specific berm design. PUK estimate the worst-case mass of rock required for the jack-up would be 6,000 t (1,000 t per leg). PUK estimate that 0.009 km2 of the seabed would be impacted from the installation of the rock berms at the installation (Table 7-4). It is also anticipated that the stabilising rock berms will be used for lifts of both the jacket and the topsides via lift vessel, therefore limiting the impact on the seabed. Table 7-4: Structures and materials with potential to impact on the seabed – lift vessel installation
Structure Dimensions Total seabed impact (km2) Lift vessel spud cans 6 x 22 m2 0.0001 Stabilisation material (rock 1.5 m x 6,000 t 0.009 berms) Lift vessel installation total 0.009
7.3.4 Anchored Lift Vessel An alternative lift vessel requiring anchoring to the seabed may also be selected for the removal of the topsides and/or jacket. As the vessel contract has yet to be awarded, calculations have been based on a worst case scenario: Lift vessel operation with a maximum eight-point mooring system; Two vessel operations at the installation (jacket and topside lifts); Anchor dimensions of 4.1 x 4.8 m, (based on a 10-tonne (10,000 kg) ‘flipper delta’ anchor); A chain length of 1,250 m, a maximum seabed contact length of 975 m and an average chain width of 0.076 m; and The vessel will be moored twice, once for the jacket and once for the topsides.
Table 7-5: Structures and materials with potential to impact on the seabed – anchoring activities
Structure Dimensions Total seabed impact (km2) Anchor (4.1 m x 4.8 m) x 8 anchors x 2 0.0003 Chain (975 m x 0.076 m) x 8 x 2 0.001 Anchoring total 0.0013
7.4 Short- and Long-Term Impacts The seabed impacts resulting from the decommissioning activities associated with the Guinevere installation can be classified as short- or long-term. Short-term impacts are defined here as those which have transient impacts lasting a few days to a few years. Long-term impacts are those which will continue to have an impact for decades to centuries following decommissioning.
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7.4.1 Short-Term Impacts Excavation and anchoring activities will be transient and will have a short-term impact on the local benthic environment in the Guinevere decommissioning area. The likely short-term (temporary) impacts arising from these activities can be summarised as: Sediment disturbance within the water column; and Fauna disturbance. 7.4.2 Long-Term Impacts The likely long-term impacts arising from these activities can be summarised as: Habitat change; and Seabed morphological change
7.5 Short-Term Impacts on Sensitive Receptors The following sections provide an overview of the current understanding of the seabed environment at the Guinevere location, enabling an assessment to be made of the spatial and temporal extent of the short- term impacts. 7.5.1 Sediment Disturbance Sediments in the vicinity of the Guinevere installation are relatively uniform, predominantly comprising sand with varying levels of gravel at some stations. The high percentage of stations not showing any fine (mud) material (Table 3-2) suggests a high energy environment within the survey area (Section 3; Bibby HydroMap, 2017a and 2017b). The proposed excavation, cutting and anchoring operations will physically disturb the sediment in the local area. The seabed sediment disturbance will be short-term, localised and confined to an estimated area of impact of, approximately, 0.017 km2 (Table 7-6). Table 7-6: Decommissioning activities with short-term potential to impact on the seabed and benthic fauna Activity Total seabed impact (km2) Table reference Jack-up (Seafox 1) placement* 0.007 7-2 Jacket removal 0.0009 7-3 Lift vessel installation** 0.009 7-4 Total short-term impact 0.017 *Includes anchoring and spud can placement. **Only includes spud can rock support as this has a greater impact than anchoring when considering a worst-case scenario.
Sediments that are redistributed and mobilised as a result of the proposed decommissioning activities will be transported by the nearbed currents before settling out over adjacent seabed areas. The hydrodynamic conditions (Section 3.3.2) will result in suspended sediment, in particular any finer particles (fines), being transported away from the source of the disturbance. The natural settling of the suspended sediments is such that the coarser fraction (sands and gravels), which comprises up the majority of the sediment sampled (Section 3.3.6), will quickly fall out of suspension with the less dense material being the last to settle. This natural process will ensure that all the suspended sediment is not deposited in one location. In such a mobile area, the expected sediment recovery time from removal and/ or excavation activities is approximately eight months, as demonstrated by Hill et al., (2011) who observed that areas of dredging on sandbanks which are subject to naturally high sediment mobility may disappear within a few tidal cycles where adequate sediment is available to supplement this. Infrequent, high-energy (storm) conditions will also result in sediment suspension and redistribution. Published calculations of wave and tidal current- induced bed shear stress clearly show that large waves have the capability to mobilise seabed sediments (ABPmer, 2012).
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7.5.2 Fauna Disturbance The proposed operations will physically disturb the benthic fauna living on or in the sediment in the local area. The disturbance to benthic fauna will be short-term, localised and confined to an estimated area of impact of, approximately, 0.017 km2 (Table 7-6). The proposed activities will cause some direct impact to fauna living on and in the sediments. Mortality is more likely in the non-mobile benthic organisms, whereas mobile benthic organisms may be able to move away from the area of disturbance and return once operations have ceased. Upon completion of the subsea decommissioning activities, it is expected that the re-deposited sediment will be quickly recolonised by benthic fauna typical of the area. This will occur as a result of natural settlement by larvae and plankton and through the migration of animals from adjacent undisturbed benthic communities (Dernie et al., 2003). In a series of large scale field experiments, Dernie et al., (2003) investigated the response to physical disturbance (sediment removal down to 10 cm) of marine benthic communities within a variety of sediment types (clean sand, silty sand, muddy sand and mud). Of the four sediment types investigated, the communities from clean sands (such as those prevalent in the Guinevere Field area) had the most rapid recovery rate following disturbance. Studies of seabed dredging sites indicate that faunal recovery times are generally proportional to the spatial scale of the impact (where the impact is between 0.1 m2 and 0.1 km2 (Foden et al., 2009)). Biological recovery is therefore expected to be even quicker in less extensive, dynamic sandy habitats (Hill et al., 2011) such as those observed at the Guinevere location. In low-energy areas of the North Sea subject to extensive dredging, local fauna took approximately three years to recover to the original level of species abundance and diversity. Studies of the impacts from anchoring indicate that the faunal recovery from the processes of anchor scarring, anchor mounds and cable scrape is likely to be relatively rapid (1 to 5 years) (DECC, 2011). Based on the dynamic seabed characteristics in the Guinevere area, recovery would be expected to be at the shorter end of this scale. A small number of demersal and pelagic fish and their spawning grounds might also be temporarily disturbed by the decommissioning activities. There are potential fish spawning areas in ICES rectangle 35F1 for herring, lemon sole, mackerel, sandeels, sole and whiting (Section 3.4.3) (Coull et al., 1998; Ellis et al., 2012). 7.6 Long-Term Impacts on Sensitive Receptors The following sections describe the footprint of the additional footprint that could be created due to the placement of rock for stabilisation on the seabed for the lift vessel. 7.6.1 Habitat Change Habitat change will result from the introduction of hard substrate (rock-placement) into a predominantly soft substrate environment. The rock would be placed in an area of the southern North Sea where the sediment comprises sands and gravelly sands (Section 3). As organisms associated with hard substrates will be naturally present in the area, the stabilisation material provide a relatively small additional rocky habitat for epibenthic organisms. The seabed features that will result from rock-placement may also provide habitats for crevice-dwelling fish (e.g., ling, conger eel and wolf fish) and crustaceans (e.g., squat lobsters and crabs) in addition to attracting fish species to the site (Lissner et al., 1991). 7.6.2 Seabed Morphological Change The footprint resulting from leaving the rock support material in situ is estimated to be 0.009 km2 (Table 7- 5). Morphological change in the seabed in the Guinevere installation area (further to the natural seabed dynamics evident in these areas) may result from the presence of rock placed on the seabed and the removal of the Guinevere jacket from the seabed. 7.7 Cumulative and Transboundary Impacts Following completion of the proposed installation decommissioning activities, the total maximum seabed footprint is expected to be 0.017 km2 (Table 7-7). A second DP is also expected to be submitted in the near- future for the pipelines and stabilisation materials associated with the Guinevere installation. As the final
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GUINEVERE DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT decommissioning option and activities associated with this are undecided, PUK cannot provide an estimate of the seabed impact at this stage, but will consider the cumulative impact of both installation and pipelines/stabilisation materials in this second DP. Within 20 km of the Guinevere installation there are six oil and gas installations, eight oil and gas pipelines, numerous subsea oil and gas structures, one offshore wind farm (OWF) under construction (Dudgeon), one consented OWF (Triton Knoll) and an active minerals aggregation dredging area (Outer Dowsing 515/2), all with varying dimensions and footprints. Based on the lack of information available regarding the physical extent of the footprint, the estimated lifespan and the planned method of decommissioning of these installations, it is difficult to quantify the level of potential cumulative impact from the existing infrastructure within the vicinity of the Guinevere installation. The proposed decommissioning activities are located, approximately, 116 km west of the UK/ Netherlands median line. Decommissioning activities are not anticipated to create any transboundary impacts. 7.8 Proposed Mitigation Measures PUK operates within a SEMS (Section 11.0) that applies to all oil and gas activities. The proposed activities described in this submission will be carried out in accordance with this management system and with PUK’s policy and procedures. Mitigation measures, in accordance with JNCC guidelines (JNCC, 2010) where available, will be implemented during the proposed decommissioning operations as appropriate (Table 7-7). The JNCC (2010) guidelines for minimising the risk of injury and disturbance to marine mammals from the use of explosives will be implemented throughout any relevant noise generating operations. Two Marine Mammal Observers (MMObs) will be on the vessel. A minimum monitoring zone of 1 km around the explosive source will be established (Table 7-9), although the final radius of the mitigation zone will be decided following consultation with JNCC. Drilling, cutting, rock-placement and vessel activity are in general not considered by JNCC (2010) to pose a high risk of injury or non-trivial disturbance. The noise impact assessment undertaken supports this view, showing that there is unlikely to be any significant impact on any marine species. It is therefore considered unlikely that further mitigation measures, beyond those naturally adopted from PUK’s SEMS, policy and procedures, will be required. Mitigation measures, in accordance with JNCC guidelines (JNCC, 2010) where available, will be implemented during the proposed decommissioning operations as appropriate (Table 7-9). Table 7-7: Proposed mitigation measures
Potential sources of impact Proposed mitigation measures Cutting and lifting operations will be controlled by ROV to ensure Subsea equipment: accurate placement of cutting and lifting equipment and minimise any cutting, excavation and lifting impact on seabed sediment. Internal cutting techniques will be used. All anchors will be completely removed from the seabed at the end of the decommissioning operations. Anchoring activities An overtrawl survey will be undertaken following decommissioning activities and establish whether any additional mitigation is needed. ROV support will be used for any rock placement. The rock mass will be carefully placed over the designated areas of seabed by ROV and/or controlled fall pipe equipped with cameras, profilers, pipe tracker and Protection material: other sensors as required. This will control the profile of the rock Rock covering and accurate placement of rock on the seabed to ensure rock is only placed within the planned footprint with minimal spread over adjacent sediment, minimising seabed disturbance.
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Potential sources of impact Proposed mitigation measures
Vessel orientation will be reviewed and selected to minimise the requirements for rock whilst allowing for the safe locating of the accommodation work vessel and access, i.e. crane reach to undertake Protection material: essential scopes of work. Rock (continued) The profile of the protective and stabilisation material on the seabed will allow fishing nets to trawl unobstructed. Suitably graded rock will be used to minimise the risk of snagging fishing gear.
7.9 Conclusions The Seafox 1 jack-up accommodation unit will be in placed adjacent to the Guinevere installation during topside preparatory operations. The positioning of the Seafox 1 jack-up legs on the seabed will create some temporary, short-term disturbance of the seabed sediments, over an estimated area of 0.007 km2. Given the dynamic seabed conditions, recovery of the seabed and associated fauna is expected to be rapid (approximately a year). The cutting and lifting of the Guinevere jacket will create a temporary, short-term disturbance of the seabed sediments, over an estimated area of 0.0006 km2. This disturbance will be relatively small and occur due to the seabed excavation (where required), the ROV manoeuvring, and the use of cutting equipment. These activities will be controlled to minimise excavation activity and to ensure the accurate placement of cutting and lifting, thereby minimising the risk of sediment disturbance. The contract for the topsides removal is yet to be awarded and it is possible that a jack-up lift vessel could be utilised. The placement of such a vessel would impact a seabed area of 0.0001 km2. Recovery of the seabed and associated fauna following the removal of a jack-up lift vessel is expected to be rapid (less than a year). If stabilising rock is required for the support of the jack-up legs, the seabed impact would be approximately 0.009 km2. This would impact the sediment through long-term, localised modification of the seabed over an estimated area of 0.009 km2 and short-term physical disturbance caused by suspension of material into the water column. This impact will be mitigated by controlled placement of the rock material to minimise seabed footprint. The rate of colonisation of new material such as rock is difficult to predict, but as organisms associated with hard substrates will be naturally present in the area, the rock-placement may provide a relatively small additional habitat for epibenthic rock-dwelling organisms. Alternatively, anchoring a lift vessel would result in an anchor footprint of 0.0013 km2. All anchors would be removed from the seabed following decommissioning operations and recovery of the seabed and associated fauna is expected to be rapid (approximately a year). Overall, the decommissioning of the Guinevere installation is expected to impact a maximum area of seabed area of 0.017 km2.
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8 SOCIETAL IMPACTS This section describes the societal impacts associated with the proposed decommissioning activities of the Guinevere installation. The assessment of societal impacts is concerned with the human components of the environment and seeks to identify the social and economic impacts on people and their activities (Morris and Therivel, 2009). 8.1 Regulatory Context Societal impacts resulting from the proposed activities associated with the decommissioning of the Guinevere installation will be managed in accordance with current legislation, guidelines and standards, as detailed in Appendix A. 8.2 Approach During the Guinevere Installation DP stakeholder engagement activities (Table 1-3) and the risk assessment of this EIA (Section 4), the activities identified as having a potential societal impact were: Post-decommissioning damage to or loss of fishing gear as a result of supporting material (rock) left in situ, posing potential snagging risks; and Onshore impacts associated with the deconstruction, reuse, recycling, treatment and disposal of materials on or near-shore.
The onshore decommissioning yard has not yet been identified and will be finalised during the contracting process. Therefore, the onshore impacts associated with decommissioning are covered at a high level in this assessment and will be subject to further assessment once a decommissioning yard has been selected. 8.3 Sources of Potential Impact The following provides a description of those societal impacts that have the potential to result from the proposed decommissioning activities stated above. 8.3.1 Interference with Fishing Activities During the decommissioning operations, navigational conflicts might occur between fishing and decommissioning vessels transiting to and from the site. This could include towed gear vessels being required to alter towing direction, or the fouling of fixed gear markers. Any interference has the potential to extend beyond the immediate vicinity of the Guinevere installation, being ultimately dependent upon the location of the decommissioning port(s) and associated transiting routes. A Navigational Risk Assessment (NRA) survey was undertaken for all vessels (including fishing vessels) travelling past the Guinevere installation (Anatec, 2017). Of the fishing vessels, the main gear types recorded during the survey period were bottom otter trawler (58%), otter twin trawler (14%) and pots/ traps (9%). The majority of fishing vessels are steaming on passage (greater than 6 knots) rather than engaged in fishing operations. The majority of the steaming vessels were travelling to the west of Guinevere and some vessels travelling at less than 3 knots appeared to be working at the Dudgeon Wind Farm and were likely being used as guard vessels. As identified in the NRA survey (Anatec, 2017), the majority of fishing activity in the vicinity of the Guinevere Field is by vessels towing mobile gear. Any interaction with vessels is expected to result in changes to fishing patterns, rather than damage to fishing gear. As such it is considered that any loss of income would be minimal. The magnitude of effect is dependent upon the location of the decommissioning port(s); the precautionary approach adopted within this EIA has assumed that transit routes will be in the vicinity of both fixed and towed gear. The mandatory 500 m safety zone will remain around the Guinevere installation throughout the period of decommissioning operations. As such, it is expected that the majority of decommissioning vessels will be located within this zone and thus any potential interference to fishing vessels is likely to be small.
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8.3.2 Damage To or Loss of Gear Once decommissioning has been completed, and only if rock-placement was utilised, there is the potential for fishing gear to snag on any rock-placement used to stabilise accommodation jack up legs / heavy lift vessel. The relative fisheries value and landings for demersal gear in 2016 was low (Table 3-11). The majority of fishing vessels identified in the NRA (Anatec, 2017) in the vicinity of the Guinevere infrastructure were vessels operating demersal gear (otter trawls). In the period, 2013 and 2014 (the most recent available data), fishing effort was dominated by pots and traps (Section 3.6.1; MMO, 2017). Vessels operating demersal gear have the highest risk associated with fastening gear on obstructions due to the nature of their activity. Whilst there is also potential for pelagic and fixed gear to snag on subsea obstructions, the associated risks are considered to be slightly lower than demersal gear due to the nature of the activities. Conversely, as the decommissioning activities proceed there will be a positive impact as new areas of the sea will ultimately become available to fisheries through the removal of the 500 m safety exclusion zone, amounting to a seabed area of 0.79 km2. 8.3.3 Onshore Impacts All structural material recovered from the Guinevere Field will be transported to shore for dismantling, and recycling or disposal as appropriate. Licensed contractors at licensed sites would undertake processing and as such minimal impacts will arise from the controlled operations. PUK’s Duty of Care extends beyond the quayside to ensure that onshore licensed disposal sites undertake all dismantling activities in a responsible manner. Any potential environmental impacts that may occur at any onshore site selected for receiving and dealing with material from the decommissioning of the Guinevere installation are anticipated to be short- lived, localised and managed according to relevant legislation and regulations. The environmental impacts are expected to be to the same as those that have previously arisen during past commercial activities at the site. PUK’s approach to hazardous and non-hazardous waste management is outlined in Section 10. 8.4 Impacts on Sensitive Receptors As stated within Section 8.3, the long-term physical presence of rock stabilisation has the potential to interfere with fishing gear, leading potentially to a loss of catch/revenue for fishermen. There may also be the potential to disrupt previously established shipping operations in the area, whilst vessels carry out removal and rock-placement/ stabilisation operations. 8.4.1 Impacts on Fishing Activities With respect to fishing activities, further potential impacts include the limited loss of access to fishing grounds during decommissioning activities. Additionally, the impedance to fishing gears by subsea rock structures decommissioned in situ only if the use of rock placement was required. Otter trawls and seabed focussed otter trawls (where large rectangular otter boards keep the mouth of the trawl net open) are the main methods of fishing in ICES rectangle 35F1 in the period 2011 to 2016 (Section 3). Both methods have the potential to interact with rock-placement. The weight and width of fishing gear and the nature of the benthic substrate will ultimately determine the level of impact. Figure 8-1 shows a typical otter trawl gear used on fishing vessels in North Sea crossing a pipeline. Rock stabilisation will only be required should seabed instability be encountered. In this instance, it has been estimated that 1,000 t of material per leg (four legs) for the accommodation vessel). For the lift vessel (six legs) this volume has been estimated at 1,000 t per leg. Overtrawlability trials will be undertaken during decommissioning and periodically thereafter. If the overtrawl trial fails, the existing rock placement design will be altered or additional rock-placement will be installed as soon as practicable. 8.4.2 Impacts on Commercial Shipping The shipping density within the interest block is stated to be moderate (BEIS, 2016b; Section 3). As the main structures to be decommissioned are contained within the 500 m exclusion zone, the impact on shipping transit and thus commercial shipping is considered to be low (Section 4). Following industry
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GUINEVERE INSTALLATION DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT standards and notifications to mariners of planned transit routes, movement of decommissioned infrastructure to the decommissioning port(s) will not pose a significant risk to commercial shipping. 8.4.3 Impacts on Onshore Communities Onshore activities include dismantling, recovery, transport and recycling of materials onshore. These activities form an integral part of the anticipated Guinevere decommissioning activities. These occurrences are anticipated to be temporary, localised to the receiving port, transport route and onshore disposal site and managed under approved licenses. As such, it is considered that these planned activities are unlikely to pose a significant risk to onshore communities. 8.5 Cumulative and Transboundary Impacts Given the location of the Guinevere installation, approximately, 116 km to the west of the UK/ Netherlands median line, there are no transboundary impacts anticipated. There are a number of oil and gas infrastructures in the North Sea which could potentially undergo decommissioning at the same time as the Guinevere decommissioning activities. In addition, there is also potential for construction activities to occur in the area as a result of wind farm development. Several Notices to Mariners have been issued for ongoing activities at the Dudgeon windfarm site and for transit to and from the site (Statoil, 2017). PUK will pay attention to these notices and will issue their own Notices when required. Given the predominately localised and limited nature of the activities associated with the Guinevere installation DP, it is unlikely that there will be any cumulative societal impacts. Whilst a cumulative impact associated with the rock-placement (Section 7) may occur, the area (approximately 0.014 km2) covered by the additional rock will be significantly less than the seabed area (0.79 km2) released for use by fisheries through the removal of the 500 m safety exclusion zone. As the decommissioning activities proceed, new areas will become available to fisheries, reducing the overall cumulative impact to fisheries and resulting in a positive impact. The fishing methods are also unlikely to change, as species associated with hard substrate material (i.e. the protective rock berm) will already be present in the area. 8.6 Proposed Mitigation Measures Proposed mitigation measures to minimise societal impacts are detailed in Table 8-1. Table 8-1: Proposed mitigation measures
Potential source of impact Proposed mitigation measures Prior to commencement of operations, the appropriate notifications will be made and maritime notices posted. Notice will be taken to other Notices to Mariners relevant to the area in the vicinity of the Guinevere installation. Physical presence of All vessel activities will be in accordance with national and decommissioning vessels international regulations. causing potential interference Appropriate navigation aids will be used in accordance with with other users of the sea the consent to locate conditions to ensure other users of the sea are made aware of the presence of vessels. The number of vessels travelling to, or standing by, at Guinevere will be kept to a minimum On-going consultation with fisheries representatives. Damage to or loss of gear as a Post-decommissioning seabed clearance. result of subsea obstructions, Overtrawlability trials during decommissioning and decommissioned in situ, posing periodically thereafter. potential snagging risks Materials left in situ will be mapped and the UK Hydrographical Office (UKHO) and Kingfisher informed. Onshore Licensed contractors at sites holding required permits
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8.7 Conclusions There will be a minor impact to any fishing activities during the decommissioning operations at the Guinevere installation. This impact will be reduced by minimising the number of vessels travelling to, or standing by, Guinevere once it has been decommissioned and taking notice of any relevant Notices to Mariners. Potential damage or loss of demersal fishing gear may occur as a result of the rock-placement to stabilise vessel legs (should the seabed prove unstable). All structural material recovered during installation decommissioning activities will be transported to shore for dismantling, and recycling or disposal as appropriate. Licensed contractors at licensed sites would undertake processing and as such minimal impacts will arise from the controlled operations As the decommissioning activities proceed there will be a net positive impact. A total of 0.009 km2 of seabed will be covered by rock placement (if required) and 0.79 km2 of seabed will ultimately become available to fisheries through the removal of the 500 m safety exclusion zone.
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9 ACCIDENTAL EVENTS This section evaluates the potential impacts of accidental events and the proposed mitigation measures which PUK will implement to reduce an event’s probability of occurrence and ensure that the environmental impact is reduced as far as is reasonably practicable. There are two types of accidental event which present the most likely worst-case environmental impacts: Hydrocarbon release or spill; and Chemical spill.
The potential risk from each of these events is examined in the following sections. Dropped objects have not been considered in this section as all dropped objects (should any occur) will be recovered. 9.1 Regulatory Context The consequences of potential oil or chemical releases from the activities associated with the proposed Guinevere decommissioning activities will be managed in accordance with current legislation and standards. These are detailed within Appendix A. 9.2 Hydrocarbon Releases This sub-section examines the potential impacts of an accidental hydrocarbon release during the decommissioning of the Guinevere installation. 9.2.1 Sources of Potential Impacts All offshore activities carry the potential risk of a hydrocarbon loss to the marine environment. During the period from 1975 to 2005, a total of 16,930 tonnes of oil was discharged from 5,225 individual spill events in the UKCS (UKOOA, 2006). Analysis of spill data for this period shows that 46% of spill records related to crude oil, 18% to diesel and the remaining 36% to condensates, hydraulic oils, oily waters and other materials (UKOOA, 2006). During 2012 on the UKCS, a total of 248 oil spills were reported to BEIS, of which 8% were greater than 455 litres (ACOPS, 2013). The potential sources of hydrocarbon spillages from the Guinevere installation have been identified through the risk assessment process and the knowledge and experience developed from PUK oil and gas operations in the North Sea. Based on this knowledge, the following scenarios have been identified for the proposed activities: Vessel sinking due to collision, releasing diesel to the sea; Diesel spill or diesel tank loss from a vessel lift; and Accidental bunkering fuel (diesel or aviation) spillage during refuelling.
There is only a small probability of a vessel collision occurring. Further, the subsea infrastructure and topsides are not expected to contain hydrocarbon fluids and as such an accidental release of condensate is not considered here. The possibility of marine diesel spillages and the associated impacts on sensitive receptors have been investigated below. 9.2.1.1 Oil behaviour at sea When oil is released to the marine environment, it is subjected to a number of processes including: spreading, evaporation, dissolution, emulsification, natural dispersion, photo-oxidation, sedimentation and biodegradation (Table 9-1). The processes of spreading, evaporation, dispersion, emulsification and dissolution are most important early on in a spill whilst oxidation, sedimentation and biodegradation become more important in later stages. The behaviour of hydrocarbons released at depth will depend on the immediate physical
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GUINEVERE INSTALLATION DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT characteristics of the release, subsequent plume dispersion processes and metocean conditions (DTI, 2001; ITOPF, 2012). Table 9-1: Overview of the main weathering fates of oil at sea Weathering Process Description Lighter components of oil evaporate to the atmosphere. An oil with a high Evaporation percentage of light and volatile compounds will evaporate more than one with a larger amount of heavier compounds. Waves and turbulence at the sea surface can cause the slick to break up into Dispersion droplets of varying sizes, which will start dispersing through the water column. Emulsification occurs as a result of physical mixing promoted by wave action. The emulsion formed is usually very viscous and more persistent than the original oil Emulsification and formation of emulsions causes the slick volume to increase between three and four times. This will slow and delay the other processes which cause the oil to dissipate. Dissolution Water soluble compounds in an oil may dissolve into the surrounding water. Oils react chemically with oxygen either breaking down into soluble products or Oxidation forming persistent tars. This process is promoted by sunlight. Sinking is usually caused by the adhesion of sediment particles or organic matter Sedimentation to the oil. In contrast to offshore, shallow waters are often laden with suspended solids providing favourable conditions for sedimentation. Sea water contains a range of micro-organisms that can partially or completely Biodegradation breakdown the oil to water soluble compounds (and eventually to carbon dioxide and water). Source: DTI, 2001; ITOPF, 2012 9.2.1.2 Hydrocarbon properties The fate and effect of a spill is dependent on the chemical and physical properties of the hydrocarbons. Hydrocarbons used in, or produced by, the Guinevere facilities include diesel, aviation fuel and condensate. The Guinevere condensate specific gravity is 0.75 with an API of 57.5°. Consequently, this condensate is classified as an ITOPF Group I oil. Group I oils (non-persistent) tend to dissipate completely through evaporation within a few hours and do not normally form an emulsion (ITOPF, 2012). Diesel and aviation fuel have very high levels of volatile components, evaporating quickly upon release. The low asphaltene content in these fuels prevents emulsification, reducing persistence of them in the marine environment. Whilst diesel oil is a more persistent hydrocarbon than the condensate, its characteristics and subsequent behaviour when released means that it is unlikely to represent a significant threat to the environment when compared to a crude oil spill. 9.2.2 Impact Assessment and Oil Spill Modelling An accidental hydrocarbon release can result in a complex and dynamic pattern of pollution distribution and impact in the marine environment. As there are a variety of natural and anthropogenic factors that could influence an accidental spill, each spill is unique. Long-term effects reported range from nothing detected (e.g., after the Ekofisk blow-out in 1977) to chemical contamination but no acute biological effects detectable (e.g., after the wreck of the Braer in 1993) (DTI, 2001). The extent of an environmental impact of a spill depends on several factors including: Location and time of the spill; Spill volume; Hydrocarbon properties; Prevailing weather/ metocean conditions;
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Environmental sensitivities; and Efficacy of the contingency plans.
Oil spill modelling for the Guinevere facilities is included within the Oil Pollution Emergency Plan (OPEP) (PUK, 2017b). Given that there will no production at the Guinevere facilities at the time of decommissioning, it is the simulation of a marine diesel oil spill that is relevant to this EIA. The pertinent results are presented in the following section. 9.2.2.1 Overview of the oil spill modelling undertaken An instantaneous loss of 87.5 m3 of marine diesel was modelled, using Oilmap Version 7.0.0.12, as the worst case release from the Seafox1 at the Guinevere installation. Although marine diesel undergoes rapid evaporation, the release location in relation to designated habitats (Section 3) is such that there exists a potential for environmental impacts. The modelling results indicate the following: Beaching has a limited likelihood (less than 6%) and is more likely to occur following an accidental release in Spring than in other seasons. The shortest arrival time is no less than 64.5 hours (2.7 days); The greatest volume beached is between 0.5 m3 (Summer) and 6.8 m3 (Spring); Only limited transboundary effects are indicated, with an associated maximum probability of 4% and minimum arrival time of 46.5 hours (1.9 days); and Sea surface contamination remains localised to the spill location, such that a maximum probability of 25% is only experienced within of 30 km of the release. A less than 10% probability of surface oiling occurs no further than 80 km from the release point. 9.2.3 Impacts on Sensitive Receptors The potential for both short-term (temporary) and long term impacts are assessed for the major taxonomic groups relevant to the southern North Sea marine environment in order to determine the potential scale of interaction within the vicinity of an accidental oil spill. The location of those designated sites which are contaminated to a minimum threshold of 0.3 µm are illustrated in Figure 9-1. Socioeconomic and shoreline impacts are also described below.
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Figure 9-1: Location of designated sites with the potential to be contaminated by > 0.3µm of marine diesel from the Seafox 1 at the Guinevere installation (PUK, 2017b).
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9.2.3.1 Biological receptors Although there is only a small likelihood (offshore typically 10% probability; shoreline less than 6%) of a hydrocarbon spill from the Guinevere facilities, there is a potential risk to organisms in the immediate marine environment if a spill were to occur. The following section highlights the biological receptors that may be impacted from a potential oil spill incident. The potential effects of oil spills to marine life during the Guinevere installation’s decommissioning activities are summarised in Table 9-2. As the majority of potential spills are likely to be on the surface, both planktonic and benthic communities are less likely to be influenced by an accidental spill. Other communities including fish, birds and marine mammals may incur greater impacts. For a description of the environmental sensitivities in Guinevere facilities areas, please refer to Section 3 (Baseline Section). Table 9-2: Summary of potential impacts to main biological receptors from a generic hydrocarbon release at the Guinevere installation location. Biological Effects and communities at risk receptor Localised effects due to toxicity. Impacts on communities are unlikely due to natural variability, high turnover and seasonal fluctuation. ITOPF (2012) reported that plankton is Plankton abundant and replenished by the constant movement of water body. There is little evidence that oil spills have caused a significant population decline in the open sea. The surface releases of diesel and condensate will likely not impact benthic communities Benthos and therefore the risk is considered minimal. The Guinevere infrastructure is located within ICES rectangle 48/17, which is spawning grounds for six species. Those species which have benthic eggs have a dependency on specific substrata for spawning. For example, sandeels lay their eggs on clean sandy sediments and therefore may spawn on discreet sandy sediments within the interest blocks. Such sediments would be considered important for this species (Section 3). Fish, The Guinevere infrastructure also lies within the nursery grounds throughout the year for spawning 11 species (Section 3). As most adult free swimming fish will move away from oil and contaminated water, fish kills in open water following an oil spill are rare (ITOPF, 2012). nursery However, if fish may be affected by oil spills, hydrocarbons may result in tainting of the grounds fish, and hence in a reduction of commercial value. Eggs and larvae may be affected, but such effects are generally not considered to be ecologically important because eggs and larvae are distributed over large sea areas. In addition, laboratory tests have not shown evidence that oil induced mortalities of fish and shellfish eggs and larvae in the open sea would result in significant effects on future adult populations (ITOPF, 1998). Whilst data shows that shellfish species are present in the vicinity of the Guinevere Shellfish infrastructure (Section 3), the surface releases of diesel and condensate will likely not impact seabed communities and therefore the risk is considered minimal. Seabird vulnerability to surface pollution varies throughout the year with peaks in late summer after breeding when the birds disperse into the North Sea, and during the winter months with the arrival of over-wintering birds. The seabird sensitivity to oil pollution in Block 48/17, where the Guinevere infrastructure is located, and in surrounding blocks Seabirds varies from low to extremely high throughout the year (Oil & Gas UK, 2016). The most sensitive times of year for birds in the Guinevere area are January to March and October to December, with extremely high vulnerability within Block 48/17 in October (Table 3.6). The periods of very high to extremely high sensitivity can be attributed to moulting of some of the species and foraging or feeding behaviour (JNCC, 1993; Section 3). Physical fouling of feathers, damage to eyes and toxic effects of ingesting hydrocarbons can result in direct and indirect fatalities. Effects would depend on species present, their abundance,
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Biological Effects and communities at risk receptor reliance on particular prey species and the time of year. Diving birds such as auks and Seabirds gannets are particularly susceptible. Species most affected may be guillemots, razorbills (continued) and puffins that spend large periods of time on the water, particularly during the moulting season when they become flightless (DTI, 2001). The main cetacean (whale and dolphin) species occurring in the Guinevere Field and surrounding quadrants are minke whale, long-finned pilot whale, bottlenose dolphin, common dolphin, white-beaked dolphin, white-sided dolphin and harbour porpoise with sightings occurring throughout the year (Section 3). Grey seals and harbour seals are considered as frequent visitors to the Guinevere NUI area Marine (Section 3). mammals Potential effects may include inhalation of toxic vapours, eye/ skin irritation and bioaccumulation. Ingestion of oil can damage the digestive system or affect liver and kidney function. Loss of insulation through fouling of the fur of young seals and otters increases the risk of hypothermia. Oil contamination can impact food resources directly through prey loss or indirectly through bioaccumulation. However it is expected that marine mammals would avoid the area if a spill were to occur. The North Norfolk Sandbanks and Saturn Reef SAC, located 12 km east, is the nearest SAC from the Guinevere NUI (Table 3.4; Figure 3.5). The North Norfolk Sandbanks and Saturn Reef SAC, designated for sandbanks slightly covered by seawater at all times and biogenic Protected reefs formed by the polychaete worm S. spinulosa, are both Annex I habitats (JNCC, 2017c; habitats Section 3). and species The Guinevere installation lies 4 km from the southern North Sea cSAC. This site is a candidate for designation for the Annex II species harbour porpoise (Section 3).
9.2.3.2 Shoreline impact Oil spill modelling for a marine diesel release from the Seafox-1 at the Guinevere installation has predicted a low probability (less than 6%) of shoreline contamination along the UK coast only. There is no beaching predicted for the Netherlands, Denmark, Belgium or French coastlines. Of note is that the modelling predicts low beaching volumes of less than 6.8 m3. 9.2.3.3 Socioeconomic receptors A number of sectors may be influenced by a potential accidental release during the Guinevere infrastructure decommissioning activities and are described in Table 9-3.
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Table 9-3: Summary of main socioeconomic receptors Socioeconomic Risks and status at Guinevere installation receptor One of the primary economic activities in the EU, fishing supports other shore- based activities including fish processing and boat construction. Impacts to offshore fishing can be either restricted to the period that oil remains on the surface or could be closed for a specified period of time following an oil spill, as access to fishing grounds would be limited. There is the potential for fish that come into contact with oil to become tainted precluding commercial sale. There is no UKCS evidence of any long-term effects of oil spills on offshore fisheries. Fisheries The total number of days’ effort in ICES rectangle 35F1 was 767 days in 2013 with and 572 days in 2014, with no data available for 2015 or 2016 (MMO, 2016). The fishing effort was dominated by pots and traps (MMO, 2016). Between 2013 and 2016 the annual total live weight of fish landed from ICES rectangle 35F1 ranged from 1,118 tonnes in 2016 to 1,411 tonnes in 2013 with the total annual value from £1,462,374 in 2016 to £1,460,313 in 2013 (MMO, 2016; Table 3.12). Coastal tourism can be adversely affected by oil pollution events owing to reduced amenity value. Impact can be further influenced by public perception and media Tourism coverage. The offshore location of the Guinevere installation (greater than 53 km from the nearest coast), combined with the limited beaching (probability and volume) suggests that there is unlikely to be any impact on tourism. The Anatec vessel traffic survey considered shipping routes in the vicinity of the Guinevere infrastructure from July to December 2016 (Anatec, 2017). Results revealed 63 shipping routes used by an estimated 12,771 vessels per year passed within 10 nm of the Guinevere installation, corresponding to an average of 35 vessels per day (Anatec, 2017). Shipping activity in the area of the Guinevere Shipping installation is regarded as moderate (Section 3). Shipping lanes are used by shuttle tankers, supply and standby vessels serving the offshore oil installations in the area. Although all may potentially be impacted by an oil spill, the impacts likely last only while oil is on the sea surface, as this may restrict access. Therefore, it is considered unlikely that there will be any long-term impacts on this industry. The Guinevere installation is located in the southern North Sea gas basin, which is densely populated by various installations (Figure 1-2). The closest platforms, to Guinevere infrastructure, include the Lancelot platform (6.9 km to the east, the Excalibur platform (7.3 km to the northeast) and the Waveney platform (7.3 km to the south). There are four known windfarms located in the vicinity of the Guinevere Oil and gas/ wind installation, the closest being Dudgeon, which is under construction, 12.7 km to the farms southeast. The Outer Dowsing aggregate dredging area is also located 3.5 km to the west of the Guinevere installation (Section 3; Crown Estate, 2016). Although these receptors may potentially be impacted by an oil spill, the impacts would likely last only whilst there is oil on the sea surface as this may, for example, restrict access to installations/ on boarding of the aggregate material. As such, it is considered unlikely that there will be any long-term impacts on this industry.
9.2.4 Cumulative and Transboundary Impacts The sub-sections below summarised the residual, cumulative and transboundary impacted expected in case of accidental oil spill event.
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9.2.4.1 Residual impacts During removal operations, the loss of hydrocarbons contained within pipework, tanks and storage sumps may result in a small release, which would cause a localised and temporary deterioration in water quality. PUK will ensure that pipework, sumps and tanks in the topsides are emptied and cleaned prior to removal. Any vessel receiving or handling the topsides will be equipped with its own Shipboard Oil Pollution Emergency Plan (SOPEP) to deal with minor releases and will have access to the PUK OPEP (PUK, 2017b) and equipment. The residual risk of an environmental impact from accidental spills during the decommissioning of the Guinevere installation will be reduced to levels that are as low as reasonably practicable (ALARP). This will be achieved by the preventive measures incorporated during design, operational control procedures and training. Even with these in place, there will still be a residual, albeit very low, risk of marine environmental and/ or socioeconomic impact. 9.2.4.2 Cumulative impacts Cumulative effects arising from the decommissioning activities at the Guinevere installation have the potential to act additively with those from other oil and gas activities, including both existing activities and new activities, or to act additively with those of other human activities (e.g., fishing and marine transport of crude oil and refined products) (DTI, 2004). Any hydrocarbon discharge as a result of the decommissioning activity would be expected to evaporate rapidly in the immediate environment without the potential to combine with other discharges from concurrent incidents. It is difficult to precisely predict whether the impacts from an oil spill to the marine ecology of the affected area would be cumulative. This would depend on previous disturbances or releases at specific locations. Cumulative effects of overlapping "footprints" for detectable contamination or biological effects are considered to be unlikely. No significant synergistic effects are anticipated (DTI, 2004). 9.2.4.3 Transboundary impacts There is a low probability that a hydrocarbon spill would cross into international sectors including the Netherlands, Belgium and French sectors. Modelling predicts that marine diesel will cross the UK/ Netherlands median line with a probability less than 4%. The probability of crossing into both the Belgium and French sectors is less than 1%. The Marine and Coastguard Agency (MCA), Counter Pollution and Response Branch also have agreements with equivalent organisations in other North Sea coastal states (Belgium, France, Germany, Ireland, the Netherlands, Norway, Sweden and Denmark), under the Bonn Agreement 1983. In the case of a spill reaching the English Channel, the Anglo-French Joint Maritime Contingency Plan (Mancheplan) covering counter pollution and rescue operations, will be activated. 9.2.5 Mitigation Measures Mitigation and management primarily focus on preventing or minimising the probability of an accidental spill and secondly, reducing the consequences of the event through optimum and efficient containment and release response. During decommissioning, minor non-routine and emergency events such as minor leaks, drips and spills from machinery and hoses on the installation, from vessels or at onshore sites, could cause a localised and temporary impact. The accidental release of small quantities of oil would be minimised as far as possible through appropriate management procedures and mitigation measures. The effects of such releases will be immediately rectified on site and managed through vigilance, operational, inspection and emergency procedures, and specific safeguards such as on-site clean-up equipment and containment measures. For these reasons, such minor events have been excluded from this assessment as they will be managed under normal operational procedures and controls. PUK’s planned response to all spills is detailed in the relevant OPEP (PUK, 2017b). Table 9-4 lists the planned measures to prevent or reduce the likelihood of a spill occurring during decommissioning of the Guinevere installation. Based on the estimated volumes of diesel and condensate, the PUK response capability for both counter pollution and containment is capable of providing an appropriate level of spill
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GUINEVERE INSTALLATION DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT response. The mitigation measures and contingency plans in place would consider all foreseeable spill risks and would ensure that the spill risk is reduced to ALARP. 9.2.6 Conclusions The conclusions from the impact assessment for an accidental hydrocarbon release are that: The worst-case scenario at the Guinevere installation would result from a loss of diesel from vessel lift or collision; Any spilt diesel, or condensate, will disperse and dilute quickly, with none or negligible impact to coastlines; Whilst the spilt contaminants may reach/ travel through designated sites, the probability of such an occurrence remains low and the duration of the hydrocarbon within the marine environment is short; The probability of a hydrocarbon spill occurring is low and will not contribute to the overall spill risk in the area; and The approved SOPEP/ OPEP response will provide the direction and strategies required to effectively manage the spill in the case of an accidental event.
Table 9-4: Oil spill preventive measures for likely scenarios during decommissioning
Potential source of Planned mitigation measures impact The inventories will be minimised prior to removal and transport to disposal yard. The OPEPs have been produced in accordance with the Merchant Shipping (Oil Pollution Preparedness, Response & Co-operation Convention) Regulations 1998 and the Offshore Installations (Emergency Pollution Control) Regulations 2002. The OPEPs detail responsibilities for initial response and longer term management, and will be updated as needed to reflect any change in operations and activities associated with decommissioning. All oil spills There are three planned levels of response, depending on the spill size: Tier 1 - standby vessel equipped with dispersants and spraying equipment; Tier 2 - air surveillance and dispersant spraying through Oil Spill Response Ltd. (OSRL); and Tier 3 - clean-up equipment and specialist staff available through OSRL. In addition, PUK have specialist oil spill response services provided by OSRL and are members of the Oil Pollution Operator’s Liability Fund (OPOL). Local shipping traffic would be informed of proposed decommissioning activities Vessel collision and a standby/ support vessel would monitor shipping traffic at all times. Spill from a vessel beyond the 500 m In the event of an accidental spill to sea, vessels will implement their SOPEP. exclusion zone
9.3 Chemical Releases An accidental chemical release can result in a complex and dynamic pattern of pollution distribution and impact to the marine environment. The number of factors that could influence an accidental spill, both natural and anthropogenic, renders each spill unique. Potential sources of impact are presented in the following sections, and include a review of the sensitive receptors that may be influenced. In many cases, both impacts and receptors have been detailed in the hydrocarbon release section (Section 9.2). Where the chemical release impacts differ from those described in the hydrocarbon release section, they are discussed in further detail.
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9.3.1 Methodology As part of the decommissioning process, it is important to consider the magnitude of a potential chemical spill and assess the effects of such an unplanned event on key sensitive receptors. 9.3.2 Sources of Potential Impact Technical failure remains the leading cause of chemical spills in the North Sea. The primary sources of loss to the environment are from spills of hydraulic fluids or chemicals. The potential sources of chemical spillages from the decommissioning of the Guinevere installation have been identified through a CA workshop and the knowledge and experience developed from PUK and oil and gas industry operations in the North Sea. Based on this knowledge, the following scenario has been identified: Accidental loss of fluids from subsea or topsides removal.
9.3.3 Impacts on Sensitive Receptors Chemical release into the marine environment may impact sensitive receptors in different ways, depending on the following factors: Spill volume; Depth of release; Chemical toxicity; Chemical solubility; Persistence in the environment; Biodegradability of the compound; Potential for bioaccumulation in the food chain; and Partitioning of individual components.
9.3.3.1 Biological receptors A comprehensive description of the biological receptors at the Guinevere installation, sensitive to potential chemical spills, is provided in Table 9-3 and Section 3. Due to the rapid dispersion and dilution of chemicals upon discharge or release, few biological receptors will be noticeably impacted. The most sensitive receptors are the planktonic communities. Plankton (phytoplankton, zooplankton and fish larvae) are likely to come into direct contact with discharged chemicals, with zooplankton appearing to be the most vulnerable particularly at the early stages of development. However, the impact of a chemical spill is not likely to impact beyond the immediate vicinity of the discharge point because: the likely credible maximum volume of chemicals that may be spilt would be very low; discharge is likely to be dispersed and diluted rapidly by the receiving environment; many of the compounds are volatile or soluble and are removed from the water by evaporation and dilution; and, Biological Oxygen Demand (BOD) is likely to be within the capacity of ambient oxygen levels.
9.3.3.2 Socioeconomic receptors The main socioeconomic receptors relevant to a hydrocarbon spill are presented in Table 9-4 and in most cases, this information is also pertinent to chemical spills. Dispersion, dilution and potentially very small volumes spilt will result in localised impact areas. No significant socioeconomic impacts are considered likely for fisheries, tourism, oil and gas, or shipping.
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9.3.4 Cumulative and Transboundary Impacts The majority of chemical spills are unlikely to result in an environmental impact due to a combination of rapid dispersion and dilution of the chemicals and the depth and distance from shore (greater than 53 km) of the Guinevere installation. The potentially spilt volumes are unlikely to pose any noticeable risk to residual, cumulative or transboundary impacts. 9.3.5 Mitigation Measures The impacts of all the chemicals that may be used or discharged offshore during decommissioning will be assessed and reported to BEIS in a relevant Portal Environmental Tracking System (PETS) application. The proposed mitigation measures to reduce the likelihood of chemical spills to the environment are presented in Table 9-5. Table 9-5: Planned mitigation measures
Potential source of Planned mitigation measures impact PUK will conduct all operations in a controlled manner with trained personnel using suitable equipment. All vessels will have suitable skill kits and an efficient spill response process is in place. Chemical spills from PUK routinely swap out perishable equipment such as hoses, and a Guinevere installation management programme is implemented in order to ensure their integrity. decommissioning Prior to transfer, visual checks are undertaken by trained personnel in activities communication with the standby vessel. Observed leaks are reported and dealt with immediately by competent personnel and reported to the appropriate authorities.
9.3.6 Conclusions The conclusions from the impact assessment for an accidental chemical release are that: Any chemical spills will disperse and dilute quickly, with only localised effects to planktonic communities. The probability of a chemical spill occurring is low and will not significantly add to the overall spill risk in the area.
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10 WASTE MANAGEMENT Decommissioning activities will generate quantities of controlled waste, defined in Section 75(4) of the Environmental Protection Act 1990 as household, industrial and commercial waste or any such waste. The sequence and quantities of controlled waste generated at any one time will depend on the processes used for dismantling and the subsequent treatment and disposal methods. Three key challenges are associated with waste management for the Guinevere installation. Generation of large quantities of controlled waste within short timeframes. This will require detailed planning to manage the logistics associated with the transport to shore, temporary storage and onward treatment/ disposal of materials. Potential for “problematic” materials, generated due to cross-contamination of non-hazardous waste with substances that have hazardous properties, which result in the material being classified as hazardous waste. Hazardous waste is defined as material that has one, or more, properties that are described in the Hazardous Waste Directive (91/689/EEC) as amended by Council Directive 94/31/EC. Problems associated with materials with unknown properties at the point of generation. These quantities of ‘unidentified waste’ require careful storage and laboratory analysis to determine whether they are hazardous or non-hazardous waste.
In accordance with the regulatory Guidance Notes under the Petroleum Act 1998 (DECC, 2011), the disposal of such installations should be governed by the precautionary principle. PUK will assume the worst-case, especially when dealing with hazardous and unidentified wastes, and choose waste treatment options which would result in the lowest environmental impact. 10.1 Waste Generation PUK will follow the principles of the Waste Hierarchy as described in Section 10.3. Typical non-hazardous waste will include scrap metals, and plastics that are not cross-contaminated with hazardous waste and can therefore be removed and recovered for reuse, recycling or landfill. Hazardous waste will include oil contaminated materials and chemicals. Many types of hazardous waste generated during decommissioning are routinely generated during production and maintenance of offshore installations. However, the decommissioning process may generate significantly greater quantities of both non-hazardous and hazardous waste when compared to routine operations and as such requires appropriate management. An estimate of the different types of materials and quantities in the Guinevere infrastructure to be decommissioned is detailed in Section 2.4.7. 10.1.1 Radioactive Waste Radioactive wastes including sources (e.g. smoke detectors) and Naturally Occurring Radioactive Material (NORM) that can accumulate within pipework and receptacles will be managed in line with current legislative requirements (Appendix A). PUK has existing procedures in place for managing radioactive waste and for working with radioactive materials (PUK, 2016a, 2016b, 2016c), which will be revised to include the removal and transportation of radioactive materials during decommissioning in consultation with the relevant authority depending on the location of disposal/ treatment site. 10.1.2 Wastes Generated During Engineering Down and Cleaning During engineering-down and cleaning, all topside systems will be depressurised, purged, flushed and rendered safe for removal operations. Pipework and tanks will be drained to remove sources of potential spills of oils and other fluids. Diesel and lubricating oils will be drained and returned to shore for disposal. Mobilised solids filtered from the pipeline flushing will be removed and sent to a fully permitted onshore treatment facility. All waste generated during engineering down and cleaning will be transported to shore.
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10.2 Regulatory Context There is no waste related legislation that specifically covers decommissioning activities, however some aspects of existing waste legislation are relevant and described in Appendix A. Whether a material or substance is ‘waste’ is determined by EU law. The EU Waste Framework Directive (WFD) (2006/12/EC) defines ‘directive waste’ as “any substance or object in the categories set out in Annex I of the Directive which the holder discards or intends or is required to discard”. Annex I provides a list of definitions and includes a general category – “Any materials, substances or products which are not contained in the above categories”. The responsibility for waste management lies with the producer or duty holder to decide whether a substance or object is waste. The action of removal and transfer of redundant installations and infrastructures to shore falls within the legal definition of waste. The responsibility for determining whether a substance or object is waste lies with the operator. Having determined the substance or object is waste, subsequent storage, handling, transfer and treatment of the waste generated is then governed by the relevant waste regulations (Appendix A). The selection of a disposal yard contractor has not been finalised by PUK. However, if the selected disposal yard is in a country outside of the UK, the waste will be dealt with in line with the receiving country’s waste legislation. The ‘Waste Hierarchy’ (Figure 10-1) is a key element in OSPAR Decision 98/3 and has been transposed into UK law through the Waste (England and Wales) Regulations 2011. The waste hierarchy is a framework which prioritises options for dealing with waste based upon their sustainability. Regulatory guidance notes on decommissioning (DECC, 2011) require that the utilisation of the waste hierarchy is incorporated into the decommissioning decision making process.
Stages Includes Most preferred Prevention Using less material in design and manufacture, keeping option products for longer, re-use, using less hazardous materials
Preparing for re-use Checking, cleaning, repairing, refurbishing, whole items or spare parts
Recycling Turning waste into a new substance or product, includes composting if it meets quality protocols
Other recovery Anaerobic digestion, incineration with energy recovery, gasification and pyrolysis which produce energy (fuels, heat and power) and materials from waste, some backfilling Least preferred Disposal Landfill and incineration without energy recovery option
Figure 10-1: The Waste Hierarchy (from EA, 2017)
10.3 Waste Management PUK recognises that, in line with the waste hierarchy, the reuse of an installation or its components is first in the order of preferred decommissioning options. However, as the Guinevere installation is obsolete
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GUINEVERE INSTALLATION DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT and/or in a degraded condition, it is not considered suitable for safe re-use. The majority of jacket and topside material will therefore be recycled. Non-hazardous materials, such as scrap metal and plastics not contaminated with hazardous waste, will be removed and, where possible, reused or recycled. Other non-hazardous waste which cannot be reused or recycled will be disposed of to a landfill site. Steel represents the largest weight from the Guinevere installation. Where necessary, hazardous waste resulting from the dismantling of the Guinevere installation will be pre- treated to reduce hazardous properties or, in some cases, render it non-hazardous prior to recycling or landfilling. Under the Landfill Directive, pre-treatment will be necessary for any hazardous wastes which are destined to be disposed of to landfill site. Tables 10-1 and Figure 10-2 outline the fate of all decommissioned material from the Guinevere installation. Only a small amount of material (approximately 0.8 tonnes), is expected to be sent to landfill. Opportunities where recover materials destined for landfill can be reduced, or otherwise recycled or reused, will be actively sought out. Table 10-1: Proposed fate of Guinevere installation materials
Infrastructure Recommended decommissioning option Destination Decommission in situ* Jacket Full removal (single lift) Recycling Landfill Reuse Recycling (or landfill where Topside Full removal (single lift) not feasible) Treatment *Steel associated with piles left in situ >3m below the seabed. Note: In reality some of the material sent to landfill or recycling may be suitable for reuse.
The management of waste generated from offshore activities is governed by PUKs ISO 14001-certified SEMS (Section 12). The SEMS includes a documented procedure for waste management (PUK, 2016d) , which is designed to ensure that all waste generated during the PUK offshore activities are managed according to the Company’s Health, Safety, Security and Environment (HSSE) policy and relevant legislation. A specific Waste Management Plan (WMP) will be developed for the Guinevere decommissioning project in order to address project specific waste management issues.
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1400
1200
Steel
1000 Concrete
800
Lead Weight (t) Weight 600 Plastics
400 NORM/ Hazardous Chemicals and materials
Marine Growth 200
0
Figure 20-2: Estimated tonnage and predicted disposal routes of decommissioned material.
Note: material to be decommissioned in situ consists of the remaining pile steel (305 t) which will be cut at ≥3 m below seabed level. A small amount of plastic has been assigned for landfill (0.8 t) and reuse (0.4 t) but these quantites are too small to be viewed here.
10.3.1 Contractor Management Waste management activities include the handling, storage and treatment of waste offshore, the transfer of waste to a waste treatment or dismantling yard for further storage, handling and treatment as appropriate, and then further transfer to the final disposal or treatment point. These activities will be conducted by contractors and sub-contractors on behalf of PUK using their own waste management systems. These contractors and sub-contractors will also prepare all necessary documentation required for the identification, quantification and tracking of wastes generated per asset in order to provide a transparent audit trail from the offshore location through to the final disposal point. Although PUK will not be undertaking the actual physical work, the legal liability i.e. Duty of Care, for all waste generated from decommissioning remains with PUK for the duration of the programme.
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The selection and management of contractors by PUK is managed through existing contractor control processes and procedures. Specific targets to maximise re-use and recycling, and minimise waste to landfill, will be agreed during the contractor selection process, and included in relevant contracts. Specific actions to support the management and minimisation of waste generated by contractors during decommissioning will include: Ensuring that waste management issues are clearly addressed within the contractor interface documents; Identifying specific roles and responsibilities within PUK and its contractors within the Guinevere Decommissioning Waste Management Plan; Engaging with contractors to identify effective technical solutions that support waste minimisation and the reuse and recycling of waste, where possible; and,
Establishing specific audit and monitoring schedules within relevant contracts.
10.3.2 Measuring and Monitoring Performance
Measuring and monitoring performance is an important element of PUK’s SEMS and a number of mechanisms are in place to do this (PUK, 2016e, 2016f). Specific areas of focus related to waste management during the decommissioning of the Guinevere installation, will be: Monitoring legislative compliance; and Measuring performance against stated targets.
A range of methods will be used to ensure effective monitoring of waste management activities including regular waste statistic tracking and auditing of contractor and disposal sites.
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11 ENVIRONMENTAL MANAGEMENT This section describes the arrangements that will be put into place to ensure that the mitigation and other measures of control, including the reduction or elimination of potential impacts are implemented and conducted effectively. This section also serves to outline the key elements of relevant corporate policies and the means by which PUK will manage the environmental aspects of the Guinevere installation decommissioning operations. 11.1 Introduction PUK hold ISO 14001 standard certification and therefore have relevant documentation to support the decommissioning process from the perspective of environmental standards. PUK operates under a Safety and Environmental Management System (SEMS), which forms part of the PUK Operating Management System (POMS). The POMS provides the framework for PUK to achieve safe and reliable operations day-in and day-out and ensures compliance with PUK’s Health, Safety, Security and Environment (HSSE) Policy. In addition to enabling the implementation of identified mitigation and control measures, the SEMS provides the means to monitor the effectiveness of these measures through check and environmental performance. The SEMS, by design, will enable PUK to control activities and operations with a potential environmental impact and provide the assurance on the effectiveness of the environmental management. 11.2 Scope of the SEMS The SEMS provides the framework for the management of Health and Safety Executive (HSE) issues within the business. The SEMS is intended for application to all of PUK’s activities as directed under the OSPAR recommendation 2003/5, promoting the design, use and implementation of Environmental Management Systems (EMS) by the Offshore Industry. PUK, as a business, is centred on oil and gas exploration activities both onshore and offshore, with the offshore components of their business including seismic and drilling operations. As a relatively small operator, PUK resource such projects through the utilisation of contractors, should these not be available within the business itself. The SEMS focuses on: Clear assignment of responsibilities; Excellence in HSSE performance; Sound risk management and decision making; Efficient and cost effective planning and operations; Legal compliance throughout all operations; A systematic approach to HSSE critical business activities; and Continual improvement.
11.3 Principle of the SEMS The following sub-sections describe the principles followed though the application of the SEMS. 11.3.1 Improvement Programmes and the Management of Change The purpose of employing an improvement programme is to: Ensure the continuous development of the PUK policy commitment. Introduce changes and innovations that ensure the achievement of performance standards where current performance is below expectations.
The SEMS also makes provision for the management of change. Changes may occur for a number of reasons, and at a number of levels. A ‘management of change’ procedure specifies the circumstances under
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GUINEVERE DECOMMISSIONING PROJECT ENVIRONMENTAL IMPACT ASSESSMENT which formal control of change is required to ensure that significant impacts remain under control and/or new impacts are identified, evaluated and controlled. 11.3.2 Roles and Responsibilities PUK will review existing environmental roles and responsibilities for staff participating in the Guinevere installation DP. These will be amended and recorded in individual job descriptions to ensure that they take into account any changes required for the management of the impacts identified in this EIA. 11.3.3 Training and Competence The competence of staff with environmental responsibilities is a critical means of control. The SEMS, in conjunction with the Human Resources (HR) department of PUK allows for the appointment of suitably competent staff. The development and implementation of training programmes facilitates understanding and efficient application 11.3.4 Communication Internal environmental communication generally employs existing channels such as management meetings, minutes, poster displays, etc. External communication with stakeholders and interested parties is controlled through a communication programme. This establishes links between each stakeholder, the issues that are of concern to them, and the information they require to assure them that their concerns and expectations are being addressed. This EIA and the associated consultation process will be used to design the ongoing communication programme. Communication and reporting will employ information derived from the monitoring programme. 11.3.5 Document Control The control of the SEMS documents is managed in the PUK Document Control System. 11.3.6 Records Records provide the evidence of conformance with the requirements of the SEMS and of the achievement of the objectives and targets in improvement programmes. The PUK SEMS specifies those records that are to be generated for these purposes, and controls their creation, storage, access and retention. 11.3.7 Monitoring and Audit Checking techniques employed within PUK’s SEMS are a combination of monitoring, inspection activities and periodic audits. The requirement for monitoring and inspection stems from the need to provide information to a number of different stakeholders, but primarily regulators, and PUK management. As such, there is a requirement for the results of monitoring and inspection to be integrated with the PUK internal and external communication programme. Monitoring and inspection activities focus on: Checks that process parameters remain within design boundaries (process monitoring); Checks that emissions and discharges remain within specified performance standards (emissions monitoring); and Checks that the impacts of emissions and discharges are within acceptable limits (ambient monitoring).
11.3.8 Incident Reporting and investigation The PUK SEMS stipulates documented procedures to control the reporting and investigation of incidents. 11.3.9 Non-confidence and Corrective Action The checking techniques outlined above are the means of detecting error or non-conformances. PUK’s SEMS includes procedures for the formal recording and reporting of detected non-conformance, the definition of appropriate corrective action, the allocation of responsibilities and monitoring of close out.
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11.3.10 Review PUK’s SEMS includes arrangements for management review. This provides the means to ensure that the EMS remains an effective tool to control the environmental impacts of operations, and to re-configure the EMS in the light of internal or external change affecting the scope or significance of the impacts. Of particular importance is the role management review plays in the definition and implementation of the improvement programme, and the management of change. 11.4 Summary of Environmental Commitments PUK has made a number of commitments within this EIA in order to reduce the potential environmental and socioeconomic impacts from the Guinevere installation decommissioning, as far as practicable. These commitments, along with the appropriate section in this EIA (where applicable), are summarised in Table 11-1. Table 11-1 Summary of environmental commitments
Issue Commitment EIA Section Vessels will be audited as part of selection and pre- mobilisation. Work programmes will be planned to optimise vessel time in the field All generators and engines will be maintained and operated to the manufacturers’ standards to ensure maximum efficiency. Atmospheric emissions Fuel consumption will be minimised by operational Section 5 practices and power management systems for engines, generators and other combustion plant and maintenance systems. Vessels will use ultra-low sulphur fuel in line with MARPOL requirements. All mitigation measures will be incorporated into contractual documents of subcontractors. Machinery and equipment will be in good working order and well-maintained. Helicopter maintenance will be undertaken by contractors in line with manufacturer and regulatory requirements. The number of vessels using dynamic positioning will Underwater noise Section 6 be minimised. To minimise potential impacts to marine mammals from decommissioning operations, PUK will conform to JNCC protocols for minimising risk to marine mammals from underwater noise throughout operations. Cutting and lifting operations of subsea equipment will be controlled and any impact on seabed sediments will be minimised. Seabed impact The requirements excavation will be assessed on a Section 7 case-by-case basis. Internal cutting will be used preferentially where access is available.
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Issue Commitment EIA Section All anchors will be completely removed from the seabed following decommissioning operations. Rock placement (if required) will take place using a ROV, controlled fall pipe equipped with cameras, profilers and other sensors as required. This will ensure rock is only placed within the planned footprint, minimising seabed disturbance. Vessel orientation will be reviewed and selected to minimise the requirements for rock whilst allowing for the safe locating of the accommodation work vessel and access, i.e. crane reach to undertake essential scopes of work. Post-removal seabed surveys will be undertaken to identify significant anomalies and dropped objects. Onshore impact Licensed contractors will be used at permitted sites Section 8 PUK have undertaken a site-specific shipping assessment prior to the Guinevere decommissioning operations (Anatec, 2017). Prior to commencement of operations, the appropriate notifications will be made and maritime notices posted. All vessel activities will be in accordance with national and international regulations. Shipping Appropriate navigation aids will be used in Section 8 accordance with the consent to locate conditions to ensure other users of the sea are made aware of the presence of vessels. The number of vessels travelling to or standing by at Guinevere will be kept to a minimum A mandatory 500 m safety zone will remain around the Guinevere NUI during the decommissioning activities. On-going consultation with fisheries representatives. Post-decommissioning seabed clearance. Overtrawlability trials during decommissioning and Fisheries periodically thereafter. Section 8 Materials left in situ will be mapped and the UK Hydrographical Office (UKHO) and Kingfisher informed. The inventories will be minimised prior to removal and transport to disposal yard. The OPEPs have been produced in accordance with the Merchant Shipping (Oil Pollution Preparedness, Accidental spills and Response & Co-operation Convention) Regulations Section 9 dropped objects 1998 and the Offshore Installations (Emergency Pollution Control) Regulations 2002. PUK have specialist oil spill response services provided by Oil Spill Response Limited (OSRL) and are
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Issue Commitment EIA Section members of the Oil Pollution Operator’s Liability Fund (OPOL). Local shipping traffic will be informed of proposed decommissioning activities and a standby/ support vessel will monitor shipping traffic at all times. In the event of an accidental spill to sea, vessels will implement their Shipboard Oil Pollution Emergency Plan (SOPEP). PUK will conduct all operations in a controlled manner with trained personnel using suitable equipment. All vessels will have suitable skill kits and an efficient spill response process is in place. PUK routinely replace perishable equipment such as hoses, and a management programme is implemented in order to ensure their integrity. Prior to transfer, visual checks are undertaken by trained personnel in communication with the standby vessel. Observed leaks are reported and dealt with immediately by competent personnel and reported to the appropriate authorities. Items will be secured to prevent loss wherever practicable. Post-decommissioning surveys will be undertaken to assess the presence and potential recoverability of any lost objects. Key environmental responsibilities, duties, communication, reporting and interface management arrangements of PUK and any main Environmental contractors involved in the decommissioning Section 10 responsibilities activities will be agreed, documented and communicated at the appropriate stages of the project. A waste management plan will be developed and put into place before the decommissioning activities commence. This plan will ensure that staff will undergo appropriate training and will be notified of Waste Section 11 disposal requirements for each waste type. Opportunities where recover materials destined for landfill can be reduced, or otherwise recycled or reused, will be actively sought out. The commitments made within this EIA will be incorporated into operational work programmes, Delivery of plans and procedures. - commitments Programmes will be tracked to ensure that commitments and mitigation measures are implemented throughout the project.
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12 CONCLUSIONS An EIA forms an integral part of the PUK SEMS ensuring that adequate environmental considerations are incorporated into the DP of the Guinevere installation. This EIA presents the findings of the EIA, providing sufficient information to enable a robust evaluation to be made of the potential environmental and socioeconomic consequences of the proposed decommissioning activities. The Guinevere installation is located in a relatively sensitive area of the southern North Sea (Section 3): All four Annex II species (harbour porpoise, bottlenose dolphin, grey seals and harbour seals) known to occur in UK offshore waters have been sighted within Quadrant 48 and the surrounding quadrants of the Guinevere Field. The installation is located 4 km from the boundary of the southern North Sea cSAC, which is designated for the Annex II species harbour porpoise. The installation is also located 12 km from the North Norfolk Sandbanks and Saturn Reef SAC, which is designated for Annex I habitats including ‘Sandbanks which are slightly covered by sea water all of the time’ and ‘Biogenic reefs formed by cold water corals.’ Following the identification of the interactions between the proposed Guinevere decommissioning activities and the local environment, the assessment of all potentially significant environmental and socioeconomic impacts, and key environmental concerns identified as requiring consideration for impact assessment (including those raised by stakeholders) were investigated in the following sections: Energy use and atmospheric emissions (Section 5); Underwater noise (Section 6); Seabed impacts (Section 7); Societal impacts (Section 8); and Accidental events (Section 9); and Waste (Section 10). Mitigation to avoid and/ or reduce the environmental concerns highlighted above is in line with industry best practice. PUK has an established SEMS process (Section 11), which will ensure that proposed mitigation measures are implemented and monitored to achieve or better the outcome presented in this EIA. PUK is aware that a number of oil and gas fields/ installations in the southern North Sea are currently being decommissioned or are reaching the end of their operational life. As a consequence, the potential for additive or cumulative impacts within the southern North Sea will be increased in the short-term. Decommissioning activities may temporarily contribute to overall gaseous emissions in the southern North Sea, but the impact of this is estimated to be very minor in context with total UKCS emissions associated with the oil and gas industry (Section 5). Underwater noise will also be increased during decommissioning mainly due to the use of explosives for cutting the well tubing and the presence of vessels, but will be transient and is not expected to have a significant cumulative impact (Section 6). Activities resulting from the decommissioning of the Guinevere installation are expected to create a maximum seabed impact of 0.017 km2 (Section 7). If required, the long-term presence of rock-placement will lead to the introduction of organisms associated with hard substrates over an extended period (Section 7). The decommissioning of any stabilisation material in situ is unlikely to have a significant impact on other sea users (i.e. fishing) (Section 8). Other than a minor contribution to overall emissions, decommissioning activities are not anticipated to cause any transboundary impacts. Overall, the EIA has evaluated the environmental risk reduction measures and this document concludes that PUK have, or intend to, put in place sufficient safeguards to mitigate the potential environmental and
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