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Brae Area Decommissioning

Environmental Impact Assessment (EIA)

Scoping Report

Prepared for:

Marathon Oil UK LLC Aberdeen, UK

Prepared by: Ramboll Environ UK Limited

Edinburgh, UK

Date: February 2016

Project or Issue Number:

UK12_21217

Contract No: UK12_21217 Issue: 8 Author Felicity Arthur/Sarah Cressy/ Peter Bruce

(signature):

Project Manager/Director Nathan Swankie

(signature):

Date: 10th February 2016

This report has been prepared by Ramboll Environ with all reasonable skill, care and diligence, and taking account of the Services and the Terms agreed between Ramboll Environ and the Client. This report is confidential to the client, and Ramboll Environ accepts no responsibility whatsoever to third parties to whom this report, or any part thereof, is made known, unless formally agreed by Ramboll Environ beforehand. Any such party relies upon the report at their own risk.

Ramboll Environ disclaims any responsibility to the Client and others in respect of any matters outside the agreed scope of the Services.

Version Control Record

Issue Description of Status Date Reviewer Initials

Author Initials

8 Final Issue for Consultation 10/02/2016 NS PB

Marathon Oil UK LLC Brae Area Decommissioning

Scoping Report

UK12_21217_8 Ramboll Environ

Contents

1 Introduction 1

1.1 Regulatory Context 1

1.2 Purpose of this Report 1

1.3 Scoping and the Environmental Impact Assessment (EIA) Process 2

2 Brae Area Decommissioning Programmes 5

3 Decommissioning Activities 8

3.1 Transportation of Workers and Materials 8

3.2 Topsides Preparation 8

3.3 Platform Subsea Installations Decommissioning 9

3.4 Topsides Removal 9

3.5 Drill Cuttings Piles Decommissioning 9

3.6 Steel Jacket Removal 10

3.7 Area Wide Subsea Installations Decommissioning 10

3.8 Well Decommissioning 11

4 Scoping Methodology 12

4.1 Approach to the Identification of Activity/Receptor Interactions 12

4.2 Multi-Stage Scoping Process 12

5 Stage 1: Preliminary Scoping 15

5.1 Stage 1 Scoping Summary 15

5.2 Stage 1 Effect Rating – Summary Matrices 15

5.3 Habitat Regulations Assessment (HRA) Screening 19

6 Stage 2 - Detailed Scoping 20

6.1 Stage 2 Scoping Summary 20

7 EIA technical studies 23

7.1 Designated Sites and Species 23

7.2 Seabed Disturbance Effects 23

7.3 Water Quality Effects 23

7.4 Noise Effects 24

7.5 Socio-economic Effects 24

7.6 Accidental Events 24

7.7 Cumulative Effects and Transboundary 24

7.8 Issues Scoped Out 25

List of Annexes

Annex A: Environmental Baseline

Annex B: Preliminary Scoping Parameters: Frequency/Likelihood; Magnitude and Environmental Effect/Risk Matrices


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Annex C1: Activity/Receptor interactions scoped as ‘high’ potential for significant environmental effect

Annex C2: Activity/Receptor interactions considered ‘medium’ potential for significant environmental effect and therefore taken forward to Stage 2 scoping

Annex C3: Activity/Receptor interactions considered ‘low’ potential for significant environmental effect and therefore scoped out of the EIA

Annex D1: Detailed Scoping Parameters: Sensitivity; Duration of Impact; Geographic Extent.

Annex D2: Summary of Stage 2 Scoping Outputs

Annex D3: Schedule of Mitigation Commitments

List of Tables

Table 2.1: Marathon Oil Brae Area Production Platforms 6

Table 2.2: Marathon Oil Brae Area Subsea Installations 7

Table 4.1: Definitions of Potential for Significant Effect 12

Table 5.1: Stage 1 Scoping - Brae Alpha, Brae Bravo and East Brae Platform Decommissioning 16

Table 5.2: Stage 1 Scoping for Area Wide Subsea Installations 17

Table 5.3: Legend for Matrices 18

Table 6.1: Stage 2 Scoping - Brae Alpha, Brae Bravo and East Brae Platform Decommissioning 21

Table 6.2: Stage 2 Scoping for Subsea Installations 22

Table A.1: Seabirds likely to be present in the area of the Brae Area 30

Table B.1: Frequency/Duration of an Activity (Planned) / Likelihood (Accidental) of the Activity 36

Table B.2: Magnitude of the Change 36

Table B.3: Scoping Effect Category Matrix 37

Table C.1 : Activity/receptor interactions scoped in for consideration within the EIA 39

Table C.2: Activity/receptor interactions for further scoping consideration 45

Table C.3: Activity/receptor interactions scoped out for consideration within the EIA 51


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Table D.1: Duration of an Effect 64

Table D.2: Summary of Stage 2 Scoping 66

Table D.3. Schedule of Scoping Stage Mitigation Commitments 77

List of Figures

Figure 1.1: Location and Summary Schematic of Brae Area Infrastructure 3

Figure 1.2 Overview of the EIA Process 4

Figure A.1: Digital Terrain Models of Drill Cuttings Piles at Brae Alpha, Brae Bravo and East Brae (Marathon Oil, UK Ltd (2013)(2)) 27


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UK12_21217_8 1 Ramboll Environ

1 Introduction

Marathon Oil UK LLC (Marathon Oil) has commenced planning for the decommissioning of the Brae Area in the UK sector of the central North Sea. The Brae Area lies approximately 170 miles (274 km) north-east of Aberdeen, as illustrated in Figure 1.1, principally within three UK Blocks: 16/7a, 16/3a and 16/3b. Marathon Oil is the operator and equity partners are TAQA Bratani Limited, TAQA Bratani LNS Limited, Centrica Resources Limited, and JX Nippon Exploration and Production (U.K.) Limited.

1.1 Regulatory Context

The decommissioning of offshore oil and gas installations and pipelines on the United Kingdom Continental Shelf (UKCS) is controlled through the Petroleum Act 1998 (as amended by the Energy Act 2008). The Petroleum Act requires Marathon Oil to prepare a Decommissioning Programme (DP) to request permission for decommissioning. The DP would include a summary of an Environmental Impact Assessment (EIA).

The requirement for an EIA under the terms of the Offshore Production and Pipelines (Assessment of Environmental Effects) Regulations 1999, as amended (the EIA Regulations) is set out within DECC guidance (DECC, 2011). In addition, subsequent licence applications under the Marine and Coastal Access Act (2009) will require to be supported by an appropriately scoped EIA and resultant Environmental Statement (ES).

1.2 Purpose of this Report

This Scoping Report is to be used as the basis for consultation with relevant stakeholders on the proposed scope of the technical assessments of the EIA. This Scoping Report is structured to provide:

a summary of the proposed decommissioning activities based on information provided by Marathon Oil;

a description of the potential environmental receptors within the Brae Area based on publically available information and previous surveys (see Annex A);

details of potential interactions between decommissioning activities and environmental receptors;

a description of the multi-stage process of scoping used to identify potential for significant environmental effects (see Annex B)1; and

the identification of proposed scope of the technical assessments.

It is noted that the scoping process will remain iterative throughout the EIA process. A further review of the scope of the EIA may be required throughout the ongoing development of the DPs, should there be a material change in parameter or method within the DPs. Under these circumstances potential for additional significant effect over and above the scope currently identified within this scoping report will be considered and consulted upon as appropriate.

1 ‘Significant’ environmental effects are identified with reference to the criteria set out in Section 4 of this report.


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1.2.1 Scoping Questions

In formulating any response to the considerations set out within this scoping report, it may be helpful to consider the following questions:

Does the description of the project and level of available data relating to current environmental conditions provide sufficient information to support the proposed scope of the EIA?

Have the potential significant effects been suitably identified and considered?

1.2.2 Contact Details

Please direct comments on the proposed scope of the EIA to:

Email: [email protected]

The consultation period for representations on the content of the proposed environmental statements will be open for four weeks from the issue of the report, closing 9th March 2016.

1.3 Scoping and the Environmental Impact Assessment (EIA) Process

This Scoping Report and the consultation responses received will inform a single, integrated EIA process for the decommissioning of the whole of the Brae Area. However, it is proposed that the Brae Area will be brought forward for decommissioning through two separate DPs covering:

East Brae Platform with Braemar infrastructure; and

Brae Alpha and Bravo Platforms with West Brae (including Sedgwick), Central Brae and all associated pipelines and subsea structures.

As a result, the EIA process will be reported as two separate Environmental Statements (ESs), in order to support the two separate proposed DPs.

The overall EIA process is illustrated by a flow chart in Figure 1.2.


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Figure 1.1: Location and Summary Schematic of Brae Area Infrastructure


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Figure 1.2 Overview of the EIA Process


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2 Brae Area Decommissioning Programmes

The proposed activities would include the decommissioning of the following structures and materials:

platform jackets;

platform topside modules;

subsea wellhead infrastructure and drilling templates;

flowlines and umbilicals;

pipelines and cables;

drill cuttings piles; and

protection structures and other seabed debris.

The Brae Area includes three production platforms: Brae Alpha, Brae Bravo and East Brae. The three platforms are supported on steel jackets with modular topsides. Brae Bravo has a secondary jacket supporting the flare, which is connected to the main platform by a steel bridge.

A summary of the platform assets included within the scope of the proposed DPs is included in Table 2.1. All measurements are approximate.


Scoping Report


Table 2.1: Marathon Oil Brae Area Production Platforms

Brae Alpha

Location UK Block 16/7a, 259 km north-east of Aberdeen

Water Depth 112 m

Production Start Date 1983

Substructure Steel Description

8 legged steel jacket, >17,300 tonnes

Topsides Description 25 modules, >30,200 tonnes (dry), >34,000 tonnes (operating)

Accommodation 211

Wells 34 (1 to Central Brae)

Brae Bravo


Water Depth 99 m



8 legged steel jacket, > 18,700 tonnes

Topsides Description 28 modules, >36,200 tonnes (Dry), >42,000 tonnes (Operating)

Accommodation 191

Wells 28 (2 to Central Brae)

East Brae


Water Depth 116 m



4 legged steel jacket, > 10,000 tonnes

Topsides Description 10 modules, >20,200 tonnes (Dry), >22,500 tonnes (Operating)

Accommodation 188

Wells 21

In addition to the production platforms, Marathon Oil operates three equity subsea installations in the form of Central Brae, West Brae (including Sedgwick) and Braemar. Subsea installations also include a network of connecting flowlines, chemical injection and control umbilicals, pipelines and utility/power cables. Table 2.2 provides a summary of the subsea installations included within the scope of the proposed DPs. All measurements are approximate.


Scoping Report


Table 2.2: Marathon Oil Brae Area Subsea Installations

Central Brae

Water Depth 105 m


Weight > 650 tonnes

Number of Wells 8

Distance from Host 7 km from Brae Alpha

West Brae and Sedgwick

Water Depth 107 m


Weight > 140 tonnes

Number of Wells 10

Distance from Host 8.8 km from Brae Alpha

Braemar

Water Depth 120 m


Weight > 20 tonnes

Number of Wells 2 (1 suspended)

Distance from Host 12.5 km from East Brae

Flowlines/Umbilicals

Total Length of flowlines >75 km

Total length of umbilicals >38 km

Pipelines /Cables

Total length of pipelines >195 km

Total length of submarine cables

>57 km

Liquids from the Brae Area are exported via the Forties pipeline to Cruden Bay, and then on to Kinneil near Grangemouth. Gas is transported via the St Fergus SAGE pipeline.

The Marathon Oil operated Brae Area platforms, pipelines and infrastructure are also used by a number of third parties. Decommissioning of third party infrastructure and tie-ins with the Brae Area infrastructure will be the responsibility of the third party operator and therefore are excluded from consideration here.


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3 Decommissioning Activities

This scoping report considers the potential for significant environmental effects associated with the potential offshore decommissioning activities2 (including alternative options). At the time of writing this scoping report, the consideration of the alternative options for decommissioning activities is ongoing as part of a parallel comparative assessment (CA) process.

The CA process will consider the potential to leave elements of the Brae area infrastructure in situ. In the event that the CA process identifies leaving items, such as the sub-structure footings for Brae Alpha, Brae Bravo and East Brae platforms in situ, a derogation application (under OSPAR Decision 98/3) would be required; however at the time of writing no decision has yet been reached. For this reason, the scoping process has considered both partial and full removal of some elements of infrastructure, where relevant.

For the purpose of this scoping exercise it has also been assumed that removal and/or management of wastes will follow all relevant methodologies, consents and discharges as set out within the Brae Area Decommissioning Waste Management Strategy (WMS) documents. The principal, overarching objectives being:

protection of the environment and achievement of compliance with environmental and waste legislation and industry standards in order to satisfy Marathon Oil’s Duty of Care with respect to wastes including (but not limited to) the principles of the waste hierarchy as established by the European Waste Framework Directive (implemented at national level by country specific regulations and regulated in Scotland by SEPA);

Stakeholder satisfaction (e.g. customer/client/regulatory authority) in relation to their expectation of continual improvement in environmental and sustainability management, this includes meeting project targets and objectives with respect to waste management;

Deliverance of a resource efficient decommissioning process, achieving both waste reduction and improved business efficiency and cost savings.

3.1 Transportation of Workers and Materials

This activity relates to general worker and materials movement and covers anticipated supply vessel and helicopter movements throughout the duration of the decommissioning activities. Vessel activity specifically associated with particular tasks are considered under the individual activity.

3.2 Topsides Preparation

This relates to activities required to ensure hydrocarbons and hazardous materials have been removed from the topside infrastructure, all processing plant has been isolated from the reservoir and pipelines have been cleaned, with all conductors, casing, tubing and other well equipment removed.

2 Activities were identified during an informal environmental scoping methodology workshop with Marathon Oil held 12th

December 2014 in Marathon Oil offices and supplemented through further, ongoing discussion and a further environmental

scoping workshop held on 4th March 2015.


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3.3 Platform Subsea Installations Decommissioning

This relates to the activities required to decommission those subsea installations directly associated with Brae Alpha, Brae Bravo, East Brae and Braemar, including mattresses, grout bags, formwork, risers, umbilicals and pipelines, and the drill template at East Brae. This would include all installations within the platform jackets, or where there would be the potential to directly disturb drill cuttings piles. This scoping report assumes that risers, umbilicals and pipelines will be cleaned and flushed. Where removal is selected through the CA process, removal would be via lift vessel or crane vessel.

For the purposes of this scoping exercise it has also been assumed that a post decommissioning debris survey would be undertaken within a 500 m radius of each platform location and a 200 m corridor along the pipelines.

3.4 Topsides Removal

Four options for topsides removal have been considered as part of this scoping exercise:

removal by a single lift;

removal by reverse installation involving modular removal by lift vessel;

demolition to small transportable sized pieces and then removal; or

hybrid methodology comprising elements of both modular removal and demolition.

3.5 Drill Cuttings Piles Decommissioning

Drill cuttings piles have been identified and quantified beneath the Brae Alpha, Brae Bravo and East Brae platforms. Biological and contaminant sampling has been completed for the Brae Alpha, Brae Bravo and East Brae drill cuttings piles and these have been used to inform this scoping report.

A Stage 1 OSPAR assessment (under the terms of OSPAR Recommendation 2006/5) was undertaken (Marathon Oil, 2008) and concluded that the drill cutting piles located at all three platforms could be expected to fall below the thresholds set out within this recommendation and could therefore be left in place to degrade naturally. Further assessment has been carried out based on a survey programme commissioned by Marathon Oil, with samples recovered from the drill cuttings piles in 2013 and 2015 (Fugro, 2013; Fugro, 2013 (2), Fugro, 2015; Fugro, 2015 (2)). Fugro calculated OSPAR screening criteria on the basis of leachate testing results (Fugro, 2015(3)). The assessments utilised the methodology set out within UKOOA (2000 and 2000(2)). Even under the worst case scenarios, the estimated values are well below the thresholds set out within OSPAR 2006/5 (as described above) and may therefore be left in situ to degrade naturally.

Notwithstanding this, Marathon Oil have proactively commissioned a Net Environmental Benefit Analysis (NEBA) to complete further evaluation of the management options for the Brae Area drill cuttings piles in order to ensure best practice and to ensure that any decision as to drill cuttings pile management draws on the strongest available evidence base.

The NEBA assessment is currently underway for three different options for drill cuttings piles management, comprising:

leave in situ to degrade naturally;

removed for onshore disposal; and

relocate from current location and redistribute across the surrounding seabed.


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3.6 Steel Jacket Removal

The following options for steel jacket removal have been considered for the Brae Alpha, Brae Bravo and East Brae jackets:

Partial removal of upper jacket by Section Cut and Lift using a Heavy Lift Vessel (HLV);

Full removal of the complete jacket by Section Cut and Lift using an HLV; and

Full removal of complete jacket by Single Lift Vessel (SLV) using a vessel such as the Allseas vessel – Pioneering Spirit.

3.6.1 Flare Stack and Bridge Removal (Brae Bravo only).

The flare stack and bridge associated with Brae Bravo will be removed in its entirety using a lift vessel. The footings of the flare tower jacket will be removed to 3 m below the seabed.

3.7 Area Wide Subsea Installations Decommissioning

3.7.1 Subsea Drill Template and Wellhead Removal

This scoping report assumes that the wellheads at Braemar, West Brae (including Sedgwick) and the drill template at Central Brae will be removed.

3.7.2 Pipeline and Flowline Decommissioning

Pipelines, umbilicals and power cables within the Brae Area have been installed in a number of configurations, including: surface laid; trenched; rock covered; and trenched with mattress protection. Pipelines considered under this heading are those pipelines running between platforms, where there is no potential to disturb drill cuttings piles (those which are not considered under Section 3.3 above). All measurements provided in the description of decommissioning activities are approximate.

3.7.3 Pipeline and Flowline Characteristics

Within the Brae Area, available data indicates approximately 80 km of pipelines are surface laid; 35 km are partially trenched with surface-laid sections around the pipeline ends and in the 500 m exclusion zones around platforms; 28 km are partially trenched except for short surface-laid sections around crossings; and 12 km are trenched and rock covered.

It has been assumed that the full 117 km length of the Brae Alpha to Forties Charlie Oil export trunk line is surface laid.

It has been assumed that approximately 23 km of the chemical control and electrical-hydraulic umbilicals associated with the flowlines from the subsea developments are buried with the flowlines, with the exception of the umbilical for the West Brae (including Sedgwick) flowline which is understood to be rock covered, whereas the flowline is trenched. Of the remaining umbilicals, it is estimated between 1.5 km and 2.2 km are surface laid with mattress protection, 12 km are trenched and rock covered.

An estimated total of between 64 km to 69 km of power cables are assumed to be buried, with mattress protection provided to surface laid sections located within approximately 100 m to 200 m of the platforms.

All pipelines would be isolated, flushed, purged and cleaned. The CA process relating to pipeline decommissioning is currently ongoing but for the purposes of this scoping exercise,


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anticipated impacts associated with both leaving pipelines, umbilicals and cables in situ, and with removal, have been considered.

3.8 Well Decommissioning

Well Plug and Abandonment (P&A) will be managed under existing permitting requirements. Well P&A will be delivered as the host platforms reach cessation of production (CoP) and as the market availability of appropriate vessels allows. As such, well P&A has not specifically been considered as an activity to be covered within this Scoping Report.


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4 Scoping Methodology

4.1 Approach to the Identification of Activity/Receptor Interactions

The scoping methodology draws on best practice guidance to identify definitions of the potential significant environmental effects. Potential significant environmental effects are considered to be those activity/receptor interactions assigned a Medium or High category. The categorisation of effect has been made with reference to the summary criteria set out in Table 4.1 (a more detailed methodology for allocating categories is provided in Annex B).

Table 4.1: Definitions of Potential for Significant Effect

Categories Definition

High A high potential for significant environmental effect or an unacceptable risk associated with an unplanned or accidental event which would require alterations to the proposed activity and/or development of effect/risk-specific mitigation proposals in order to eliminate/mitigate to an acceptable level.

High potential activity/receptor interactions at stage 1 will be taken forward into the detailed EIA process.

Medium A medium potential for significant environmental effect or risk associated with an unplanned or accidental event that may be acceptable, but only if further investigated and/or appropriately mitigated through the implementation of best practice/generic mitigation.

Medium potential activity/receptor interactions at stage 1 will be taken forward into the Stage 2 Detailed Scoping process

Low A low potential for significant environmental effect or risk associated with an unplanned or accidental event that is considered to be of little consequence and can be further reduced by generic mitigation and controls.

Low potential activity/receptors interactions will be scoped out from further assessment.

Negligible Negligible potential for significant environmental effect or risk associated with an unplanned or accidental event that is considered to be inconsequential. Often will not require mitigation or control.

Insignificant activity/receptors interactions will be scoped out from further assessment.

No Impact/ Positive No potential for significant environmental effect or a positive environmental effect. No identified risk of accidental or unplanned event.

Where no activity/receptors interaction is identified, this will be documented and discounted.

Where a potentially positive activity/impact interaction is identified, this will be documented.

4.2 Multi-Stage Scoping Process

The aim of this scoping process is to ensure a focused and proportionate EIA and ES, targeted to the specific requirements of the proposed Brae Area decommissioning activities. To achieve this aim, the EIA has been scoped by means of a multi stage scoping process. These stages comprise:


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4.2.1 Preliminary scoping (Stage 1)

Stage 1 scoping includes:

the identification of the proposed decommissioning activities that could interact with the environment (biological, physical and human);

the identification of potential environmental receptors based on publically available information and field specific information available from previous surveys (as outlined in Annex A);

the completion of environmental effect matrices to identify potential interactions between decommissioning activities and specific environmental receptors; and

the allocation of an initial effect category based on the Table 4.1 criteria using professional judgement.

At the conclusion of Stage 1, the initial effect categories are used as follows:

High potential activity/receptor interactions are taken forward into the detailed EIA process;

Medium potential activity/receptor interactions are taken forward into Stage 2 – Detailed Scoping Process; and

Low/insignificant or no potential activity/receptor interactions are scoped out from further assessment as part of the EIA.

Where interactions have been categorised across a range of effect levels (for example low – high potential for significant environmental effect), these have been allocated to the highest category within the matrices. A range arises when the impact magnitude has the potential to vary (e.g. accidental events could vary from a small oil release to a substantial oil spill from a vessel) and/or where only a subsection of receptors may be affected (e.g. where a high risk of potential effect from underwater noise is anticipated on marine mammals, where the same noise may be anticipated to have a low potential to result in significant effects on seabirds).

4.2.2 Detailed scoping (Stage 2)

This stage provides an additional level of scoping consideration for those potential activity/receptor interactions identified as ‘Medium’ at Stage 1, in order to further characterise the potential for environmental effect, considering the following factors:

a qualitative assessment of the sensitivity of the receptor, based on a scale of high, medium and low, with reference to criteria set out in Annex D1;

the duration of the effect, based on the criteria for long, medium and short term in Annex D1;

information available on the geographic extent of potential interactions, based on local, regional and national/international levels; and

the anticipated standard and best practice working methods to which Marathon Oil is committed to using and the extent to which they would avoid or reduce the environmental effect or risk of accidental event.

As with the Stage 1 scoping, the effect categories allocated at Stage 2 have been used to define the proposed scope of the EIA, with Medium and High activity/receptor interactions taken forward into the EIA process.


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4.2.3 Further Scoping Consideration (Stage 3)

The CA process may rule out some potential activity/receptor interactions. As such, it is anticipated that further consideration would be given to reducing the scope of the EIA prior to completion of the detailed technical impact assessment based on the outcomes of the CA process.

This document reports on both Stage 1 and Stage 2 scoping, which has been sufficient for the majority of issues to confirm the proposed scope of the technical assessment prior to preparation of the Environmental Statements. The ESs would provide further commentary on further scoping stages (Stage 3).


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5 Stage 1: Preliminary Scoping

5.1 Stage 1 Scoping Summary

The potential for activity/receptor interactions have been grouped into environmental effect categories as follows:

Designated Sites/Species Disturbance Effects: this includes the consideration of potential effects associated with seabed disturbance or the removal of subsea installations on sites or species designated for protection under the Habitats Directive3. The consideration of potential effects associated with underwater noise and pollution on marine mammals are considered separately below.

Seabed Disturbance Effects: this includes potential for effects on marine benthos, geology, natural seabed sediments and drill cuttings piles associated with seabed disturbance.

Noise Effects: this includes potential for effects on fish, seabirds and marine mammals.

Water Quality Effects: this includes potential for direct effects on water quality and secondary/indirect effects on plankton, fish, shellfish and marine mammals associated with the potential for contamination of water quality through either the disturbance of drill cuttings pile sediments or planned discharges of waste water, chemicals or oils to the sea.

Socio-economic and Other Effects: this includes potential for effects on commercial fisheries, shipping and navigation, human health, recreation and tourism, marine archaeology.

Atmospheric Emissions Effects; this includes consideration of likely consumption of natural resources associated with vessel movements and the emissions to atmosphere, with the potential for local air pollution, global climate change and acidification effects.

Accidental Events: this includes a consideration of potential risk to water quality and supported marine ecosystems, and other users of the sea as a result of accidental release of contaminants.

5.2 Stage 1 Effect Rating – Summary Matrices

Table 5.1 provides a summary of the Stage 1 effect categorisation for the activity/receptor interactions identified for Brae Alpha, Brae Bravo and East Brae platforms. Table 5.2 provides a summary of the Stage 1 effect categorisation for decommissioning subsea installations (area wide). Table 5.3 provides a legend for the colours used in Table 5.1 and 5.2. The reference provided in each cell of the matrices relates to the rationale provided in Annex C1, C2 and C3, for example, reference C3.1 is found in Annex C3.

3 Council Directive 92/43/EEC on the Conservation of Natural Habitats and of Wild Fauna and Flora


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Table 5.1: Stage 1 Scoping - Brae Alpha, Brae Bravo and East Brae Platform Decommissioning

Decommissioning Activity Des

ign

ated

Sit

es/

Sp

ecie

s D

istu

rban

ce

Eff

ects

Sea

bed

Dis

turb

ance

E

ffec

ts (

mar

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s,

geo

log

y, n

atu

ral s

eab

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ile)

No

ise

Eff

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s (f

ish

, m

arin

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als,

se

abir

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Wat

er Q

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s (w

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, sh

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ffec

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(co

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(en

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Acc

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ven

ts (

ris

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wat

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and

su

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Transportation of materials to and from Brae Area

C3.1 C3.10 C3.15 C3.19 C3.23 C3.25 C3.26

Topsides Preparation C3.2 C3.11 C3.16 C3.20 C3.23 C3.25 C1.5

Platform Subsea Installations Removal#

C3.3 C2.1 C2.4 C1.4 C3.24 C2.11 C1.6

Topsides Removal C3.4 C3.12 C2.5 C3.21 C3.24 C2.11 C1.6

Drill Cuttings Piles (Remove / Relocate)

C3.5 C2.1 C2.1 C1.4 C3.24 C2.11 C1.6

Drill Cuttings Piles (left in situ) C3.6 C3.13 C3.17 C2.8 C3.24 C3.25 C3.27

Steel Jacket - Full Removal^ C3.7 C2.1 C1.2 C1.4 C3.24 C2.11 C1.6

Steel Jacket – Partial Removal* C3.8 C2.1 C1.2 C2.8 C2.10 C2.11 C1.6

*(footings left in situ); # (directly associated with the platform); ^ (including Brae Bravo Flare Jacket removal)


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Table 5.2: Stage 1 Scoping for Area Wide Subsea Installations


ign

ated

Sit

es/

Sp

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s D

istu

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ects

Sea

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Dis

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No

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s (f

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se

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Wat

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s (w

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atio

n,

recr

eati

on

)

Atm

osp

her

ic E

mis

sio

n

Eff

ects

(en

erg

y u

se,

clim

ate

chan

ge,

air

q

ual

ity)

Acc

iden

tal E

ven

ts (

ris

k to

wat

er q

ual

ity

and

su

pp

ort

ed m

arin

e lif

e)

Subsea Installations* (drill templates, wellheads, mattresses, formwork) – removal

C3.9 C2.2 C2.7 C2.9 C3.24 C2.11 C1.6

Subsea Installations (Central Brae Template) - removal

C3.9 C2.2 C1.3 C2.9 C3.24 C2.11 C1.6

Braemar Subsea Installations (wellhead and flow line tie back to East Brae) - removal

C1.1 C.2.2 C2.7 C2.9 C3.24 C2.11 C1.6

Pipelines / Cables / Flowlines / Umbilicals – full or partial removal

C3.9 C2.3 C2.7 C2.9 C3.24 C2.11 C1.6

Pipelines / Cables / Flowlines / Umbilicals – left in situ

C3.9 C3.14 C3.18 C3.22 C3.24 C3.25 C3.28

* including West Brae and Sedgwick


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Table 5.3: Legend for Matrices

Legend Effect Category

High

Medium

Low

Negligible/ No Impact / Positive

Stage 2 - Low (downgraded from medium)

Stage 2 – Medium (taken forward to EIA)

5.2.1 High Potential for Significant Environmental Effect

A high potential for significant environmental effect was identified as follows:

seabed disturbance (and effects on designated sites) through the removal of the Braemar wellhead protection structures and flowlines to East Brae;

noise effects on marine mammals associated with steel jacket removal and subsea installation (Central Brae template) removal;

water quality effects and effects on supported marine life associated with drill cuttings piles removal or disturbance as a result of full steel jacket removal and platform subsea installation removal; and

accidental events associated with topsides preparation, removal and steel jacket and subsea installation removal.

Habitats Regulations Assessment (HRA) is considered in Section 5.3 below. Potential environmental effects categorised as high are described further in Annex C1. These will be taken forward for further consideration within the EIA.

5.2.2 Medium Potential for Significant Environmental Effect

A medium potential for significant environmental effect was identified as follows:

seabed disturbance associated with steel jacket removal at Brae Alpha, Brae Bravo and East Brae;

seabed disturbance associated with the removal of subsea installations (area wide) as defined in Table 2.2;

Noise Effects on marine mammals, fish and seabirds associated with removal of area wide subsea installations and topsides;

water quality effects and effects on supported marine life associated with drill cuttings piles (left in situ) at Brae Alpha, Brae Bravo and East Brae and the removal of area subsea installations);


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socioeconomic effects, specifically related to commercial fisheries, associated with steel jacket partial removal at Brae Alpha, Brae Bravo and East Brae; and

atmospheric emissions and resource use associated with energy use and vessel emissions during topside preparation, removal, steel jacket removal at Brae Alpha, Brae Bravo and East Brae and the area wide removal of subsea installations.

Potential environmental effects categorised as ‘medium’ are discussed within Annex C2 and were taken forward to more detailed scoping analysis (see Stage 2 below) before confirming the proposed scope of the EIA technical assessments.

5.2.3 Low, Insignificant or No Potential for Significant Environmental Effect

Those activity/receptor interactions which are categorised as ‘low’, ‘negligible’ or ’no impact/positive’ and which are therefore not considered likely to give rise to significant environmental effect have been scoped out from further consideration within the EIA. Potential environmental effects categorised as ‘low’ ‘negligible’ or ’no impact/positive’ are discussed within Annex C3.

5.3 Habitat Regulations Assessment (HRA) Screening

Neither Brae Alpha, Brae Bravo or East Brae platforms or associated subsea infrastructure lie within any sites designated for protection under the Habitats Directive (Council Directive 92/43/EEC) and no currently designated features have been identified associated with these platforms. Likewise the Central Brae template and wellheads and other subsea installations at West Brae and at Sedgwick lie outside any designated sites.

Potential for significant effect on the Braemar Pockmarks SAC as a result of decommissioning activities at Braemar and along the associated flowlines to East Brae will be considered within the EIA and sufficient information will be provided within the East Brae and Braemar ES to allow the Competent Authority – in this case DECC - to give due consideration to the potential for significant effects on the Braemar pockmarks SAC.

An evaluation of available ROV footage of the Brae Area infrastructure has been completed. No evidence of biogenic reef forming organisms e.g. Lophelia spp has been identified on Brae Area infrastructure. As a result, the consideration of potential effects on designated species has been scoped out of the EIA. Further pre-decommissioning survey to check for the presence of designated species would be completed prior to the decommissioning activities taking place.


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6 Stage 2 - Detailed Scoping

Those activity/receptor interactions identified as having ‘Medium’ potential for significant environmental effect during Stage 1 scoping have been given further scoping consideration as detailed below.

6.1 Stage 2 Scoping Summary

Table 6.1 provides a summary of the Stage 2 effect categorisation for the activity/receptor interactions identified for Brae Alpha, Brae Bravo and East Brae platforms. Table 6.2 provides a summary of the Stage 2 effect categorisation for area wide decommissioning of subsea installations. Environmental receptors have been grouped by effect as described previously.

Where, following additional consideration, it is concluded that insufficient evidence exists to justify an amendment to the effect categorisation (i.e. the interactions remain ‘Medium’ in Table 6.1 and 6.2), the activity/receptor interaction in question has been taken forward into the detailed EIA process for further analysis.

Effects downgraded to ‘Low’ or ‘Insignificant’ following further consideration during the Stage 2 scoping, will not be considered further within the EIA, however any generic/best practice mitigation on which the scoping decision depends will be itemised and carried forward into the schedule of commitments to be included within the final ESs.

The further consideration given to activity/receptor interactions has been summarised within Annex D2. The scoping stage schedule of mitigation commitments is provided in Annex D3.


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Table 6.1: Stage 2 Scoping - Brae Alpha, Brae Bravo and East Brae Platform Decommissioning


ign

ated

Sit

es/

Sp

ecie

s D

istu

rban

ce

Eff

ects

Sea

bed

Dis

turb

ance

E

ffec

ts (

mar

ine

ben

tho

s,

geo

log

y, n

atu

ral s

eab

ed

sed

imen

t an

d d

rill

cutt

ing

s p

ile)

No

ise

Eff

ect

s (f

ish

, m

arin

e m

amm

als,

se

abir

ds)

Wat

er Q

ual

ity

Eff

ect

s (w

ater

qu

alit

y, p

lan

kto

n,

fish

, sh

ellf

ish

, mar

ine

mam

mal

s)

So

cio

-eco

no

mic

an

d

Oth

er E

ffec

ts

(co

mm

erci

al f

ish

erie

s,

ship

pin

g/n

avig

atio

n,

recr

eati

on

)

Atm

osp

her

ic E

mis

sio

n

Eff

ects

(en

erg

y u

se,

clim

ate

chan

ge,

air

q

ual

ity)

Acc

iden

tal E

ven

ts (

ris

k to

wat

er q

ual

ity

and

su

pp

ort

ed m

arin

e lif

e)

Transportation of materials to and from Brae Area

Topsides Preparation

Subsea Installations Removal# D2.1 D2.3 D2.7

Topsides Removal D2.3 D2.7

Drill Cuttings Piles (Remove / Relocate)

D2.1 D2.3 D2.7

Drill Cuttings Piles (left in situ) D2.5

Steel Jacket - Full Removal D2.2 D2.7

Steel Jacket – Partial Removal* D2.1 D2.5 D2.6 D2.7

*(footings left in situ); # (directly associated with the platform)


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Table 6.2: Stage 2 Scoping for Subsea Installations


ign

ated

Sit

es/

Sp

ecie

s D

istu

rban

ce

Eff

ects

Sea

bed

Dis

turb

ance

E

ffec

ts (

mar

ine

ben

tho

s,

geo

log

y, n

atu

ral s

eab

ed

sed

imen

t an

d d

rill

cutt

ing

s p

ile)

No

ise

Eff

ect

s (f

ish

, m

arin

e m

amm

als,

se

abir

ds)

Wat

er Q

ual

ity

Eff

ect

s (w

ater

qu

alit

y, p

lan

kto

n,

fish

, sh

ellf

ish

, mar

ine

mam

mal

s)

So

cio

-eco

no

mic

an

d

Oth

er E

ffec

ts

(co

mm

erci

al f

ish

erie

s,

ship

pin

g/n

avig

atio

n,

recr

eati

on

)

Atm

osp

her

ic E

mis

sio

n

Eff

ects

(en

erg

y u

se,

clim

ate

chan

ge,

air

q

ual

ity)

Acc

iden

tal E

ven

ts (

ris

k to

wat

er q

ual

ity

and

su

pp

ort

ed m

arin

e lif

e)

Subsea Installations* (drill templates, wellheads, mattresses, formwork) – Removal

D2.1 D2.4 D2.5 D2.7

Subsea Installations (Central Brae Template)

D2.1 D2.5 D2.7

Braemar Subsea Installations (wellhead and flow line tie back to East Brae)

D2.1 D2.4 D2.5 D2.7

Pipelines / Cables / Flowlines / Umbilicals – full or partial removal

D2.1 D2.4 D2.5 D2.7



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7 EIA technical studies

The EIA technical studies will draw on available literature, existing survey data and reports including but not limited to, those listed within Annex A.

The following technical studies will be delivered in support of the Brae Area EIA. No additional baseline surveys involving primary data collection are proposed.

7.1 Designated Sites and Species

Sufficient information will be provided within the EIA to allow consideration by the Competent Authority of the potential for significant effect on the Braemar Pockmarks SAC as a result of the decommissioning of the Braemar wellhead, suspended well and flowlines as required to undertake a Habitat Regulations Assessment (HRA) under the Habitats Directive4.

7.2 Seabed Disturbance Effects

The assessment of seabed disturbance effects will include consideration of the potential for effects on marine benthos, geology, natural seabed sediments and drill cuttings piles sediments. The study will be undertaken using baseline information previously collected for the ongoing Brae Area NEBA study.

Consideration will be given to:

the potential for significant effect on both soft sediment and hard substrate benthic communities as a result of jacket removal (with and without footings) (including removal of marine growth) at each of the production platforms (Brae Alpha, Brae Bravo and East Brae), including Priority Marine Features as defined by the Marine (Scotland) Act 2010; and

the potential for significant seabed disturbance as a result of the full or partial removal of the subsea installations associated with the Braemar wells, flowlines/umbilicals and pipelines/cables.

Potential for significant effects as a result of short term sediment disturbance resulting from removal of other Brae Area subsea infrastructure (West Brae and Sedgwick wellheads, flowlines, Central Brae drill template and other subsea installations) where resettlement may be expected to be rapid with limited potential for the formation of persistent mounds has been scoped out the EIA.

7.3 Water Quality Effects

The assessment of water quality effects will include consideration of the potential for effects on water quality, plankton, fish and shellfish, benthos and marine mammals.

Within this workscope further consideration will be given to:

the potential for significant effect as a result of increases in contaminant levels in the water column and in surrounding seabed sediments as a result of drill cuttings piles

4 Council Directive 92/43/EEC on the Conservation of Natural Habitats and of Wild Fauna and Flora.


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removal or disturbance as a result of jacket removal at the three platforms, Brae Alpha, Brae Bravo and East Brae.

The detailed scope of this assessment will draw on and be integrated with the ongoing NEBA study currently being delivered in support of the Comparative Assessment process.

7.4 Noise Effects

The assessment of underwater noise will include the potential for effects on marine mammals as a result of steel jacket removal for the three main platforms, and the removal of other subsea installations (including the potential use of explosives).

The study will be undertaken using baseline information previously collected and reported in the technical reports on fish, shellfish and marine mammals referenced in Annex A.

Potential for significant effects on marine mammals and seabirds as a result of topside removal has been scoped out of the EIA. Potential for significant effects on fish and seabirds associated with jacket removal has been scoped out of the EIA.

7.5 Socio-economic Effects

Further consideration will be given to the potential for significant socio-economic effects on demersal commercial fishing activities as a result of the proposed decommissioning programme, particularly associated with the full or partial removal (and derogation to leave footings in situ) for the Brae Alpha, Brae Bravo and East Brae platform jackets.

7.6 Accidental Events

The assessment of accidental events will give consideration to the potential for significant effect on water quality and supported marine ecosystems as a result of:

accidental release of contaminants during topside preparation for removal;

accidental spills associated with vessel activities; and

risk of dropped objects during decommissioning, particularly associated with lift operations.

7.7 Cumulative Effects and Transboundary

Cumulative effects fall into one of three categories, as follows:

The potential for individual activity/receptor interactions associated with each of the Brae Area decommissioning activities to combine and have a significant cumulative effect will be considered where there is the potential for the activity/receptor interaction to be either spatially or temporally concurrent, for example in combination effects on marine mammals associated with discharges to sea and underwater noise.

In addition the potential for cumulative effects to result from the addition or combination of activities to decommission East Brae and Braemar, with the activities proposed to decommission Brae Alpha, Brae Bravo and other area wide subsea installations, and vice versa will be considered.

Finally, consideration will be given to the potential for cumulative effects associated with the addition or combination of the Marathon Oil Brae Area decommissioning activities, with other known proposed DPs submitted to DECC by other operators, where it is considered likely that there would be a spatial or temporal overlap (e.g. those third party assets shown on Figure 1.1). Where there is no valid DP, there may


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be insufficient information to provide a meaningful cumulative effects assessment, in which case the ES will acknowledge the potential for cumulative effect, and set out a proposed process through which the potential interactions between DPs would be communicated and managed between operators.

The potential effects of each of the decommissioning activities will also be considered in respect to any implications for the territory of another country, in this case potentially significant effects which may extend across the Norwegian boundary line 4.4 km to the East of the East Brae platform, where their occurrence has the potential to result in environmental and/or socio-economic impacts across international borders.

7.8 Issues Scoped Out

7.8.1 Atmospheric Emissions

It is noted that the potential emissions associated with decommissioning would represent a reduction in emissions relative to the normal operational emissions associated with operating the Brae Area platforms and infrastructure. However, the comparative consideration given to ensuring that energy use and air quality effects will be as low as reasonably practical will be documented within the section of the ESs describing Alternatives/Comparative Assessment. All vessels will comply with MARPOL 73/78 Annex VI on air pollution; plant will comply with relevant air pollution regulations (The Offshore Combustion Installations (Prevention and Control of Pollution) (Amendment) Regulations 2007. On this basis it is considered that there is no potential for significant effect as a result of atmospheric emissions and this activity/receptor interaction has been scoped out of the EIA.


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Annex A: Environmental Baseline


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This section summarises available information relating to the likely environmental characteristics of the offshore environment in the area of the Brae area.

Geology and Sediments

Surface geology of the seabed is primarily determined by the reworking of seabed sediments by tides and sea waves.

Parts of the Brae area have been mapped as deep circalittoral mud (European Nature Information System (EUNIS) classification A5.37) which is described as ‘mud and cohesive sandy mud in the offshore circalittoral zone, typically below 50-70m depth’ (Gatliff et al., 1994). To the south, seabed sediments in the Brae area comprise very fine to medium sands (ranging to well-sorted to very poorly sorted). Environmental monitoring surveys indicate a gradient in sediment type from north (finer and muddier) to south (coarser sediments with less mud).

Monitoring undertaken at Brae Bravo (Fugro, 2013, Fugro, 2013 (2)) indicates that sediments have a low organic and carbonate content, with metal contents within the range of natural background concentrations. Immediately adjacent to and under the Brae area platforms, mounds of previously discharged drill muds and cuttings are known to exist which will contain elevated concentrations of hydrocarbons and some metals (see Figure A.1) (Marathon Oil, UK LLC (2013) (2)). Mounds range in height from 7.59 – 11.45 m high (Brae Alpha being the highest), with a minimum observed depth of 92.33 m bsl (at Brae Bravo).

Figure A.1: Digital Terrain Models of Drill Cuttings Piles at Brae Alpha, Brae Bravo and East Brae (Marathon Oil, UK Ltd (2013)(2))

The seabed in the Brae area is relatively flat, with depths averaging between 90 - 140 m.

In the central and northern North Sea the spreads of soft muds are locally characterised by small depressions or ‘pockmarks’, seabed pockmarks are shallow seabed depressions likely caused by the venting of fluids gases into the water column (Hartley, 2005) (discussed further in Section: Designations). The pockmarks identified in the vicinity of the Brae Area range in size from a diameter of 5 - 10 m and a maximum depth of 0.5 m, to larger less frequent pockmarks with a diameter of 50 - 130 m and a maximum depth of approximately 5 m (Hartley, 2005) . The Braemar Pockmarks to the north of the Brae area, in the region of the Braemar infrastructure, are designated as a Special Area for Conservation (SAC).


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Bathymetry and Hydrography

The East Shetland Atlantic Inflow is the dominant current in the region, with the Fair Isle current dominating the local hydrography around the Brae Area. Non-tidal currents in the Brae Area are dependent on meteorological conditions and are therefore irregular in nature but generally have an easterly set. The northern North Sea experiences the highest 50 year extreme maximum wave height in the North Sea of 30 - 32 m with a corresponding wave period of 18-19 seconds (OSPAR, 2000). However, the mean wave height for the Brae Area is much lower, at 2.3 m.

During the summer, the temperature and nutrient content of the central and northern North Sea is determined by the formation of a thermal stratification at approximately 30 - 50 m depth. This results in reduced vertical mixing, lowering the temperature and nutrient concentrations at depth. Increased wave strength and frequency in autumn, caused by stronger winds, increases vertical mixing in the water column and breaks down the thermocline.

Water Quality

The offshore areas of the northern North Sea have some of the best water quality in the North Sea. Levels of anthropogenic radionuclides in seawater in the region are low compared to the naturally occurring radionuclides and concentrations of trace metals in the seawater of the region are also expected to be low (OSPAR, 2000). Nutrient levels (including nitrate and phosphate levels) in the region vary seasonally, primarily influenced by the inflow of Atlantic water, stratification and utilisation by phytoplankton. Nutrient levels decrease in spring with reduced water inflow and the start of phytoplankton blooms (DECC, 2001). The salinity in the central and northern North Sea is fairly constant, rising slightly in the summer.

Plankton

The plankton composition within the Brae area is expected to reflect the composition found in this area of the North Sea. The Atlantic inflow to this region introduces extra nutrients allowing the area to sustain higher primary production by plankton than further south in the North Sea. Physical factors, such as stratification, have a dominant role in the composition of plankton communities in the central and northern North Sea (DECC, 2001). Phytoplankton communities in the North Sea are dominated by diatoms, dinoflagellates and smaller flagellates.

Zooplankton biomass follows a seasonal variation in primary productivity (caused by changes in phytoplankton), with a peak in May followed by a sharp decline in the winter. The rate of population response in zooplankton is much slower than phytoplankton, which allows algal populations to bloom (DECC, 2001); furthermore, as a result of the slower response, much of the phytoplanktonic production within the central and northern North Sea is thought to sink to the seabed rather than being consumed by zooplankton, providing a major source of carbon and energy to support the offshore marine ecosystem. Phytoplankton is dominated by copepods, mainly Calanus species (C. finmarchicus and C. helgolandicus), though larger zooplankton such as krill (euphausiids), salps and doliolids (thaliacea) and jellyfish (siphonophores and medusae) (DECC, 2001) can also reach large densities and provide a primary food source for fish and whales.


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Benthos

The benthic communities in the central and northern North Sea often show a characteristic relationship to sediment type in terms of biomass, productivity, diversity and species composition. Monitoring undertaken at Brae Bravo (Marathon Oil UK LLC, 2013 (2)) has indicated that the composition of benthic communities is also influenced by distance and bearing from the platform jacket and footings.

Therefore, on the basis of the fine sediments identified within the Brae Area, communities in the region may be expected to correspond closely to those identified by Basford et al., (1990) from the deeper water silty sand habitats within the North Sea, either:

Group III (characterised by the brittlestars Amphiura filiformis and Amphiura chiajei, the scaphopod mollusc Antalis entalis and the cumacean Brachydiastylis resima); or

Group IV (characterised by the polychaetes Lumbrineris fragilis and Levinsenia gracilis, and the amphipod Eriopisa elongata).

The deep circalittoral mud (EUNIS classification A5.37) benthic habitats mapped within the Brae area can support a variety of faunal communities, depending upon the level of silt/clay and the organic composition of the sediment. Communities are typically dominated by polychaetes but often with high numbers of bivalves such as Thyasira spp., echinoderms and foraminifera (EUNIS, 2012):

Capitella spp: Polychaete annelid worm which is typically used as a bio-indicator of disturbed marine habitats as it is known to require organically enriched sediment to support normal physiological development;

Paramphinome jeffreysii: Polychaete worm identified as a defining species in the macro-faunal assemblage of the EUNIS habitat classification for offshore circa-littoral sandy mud; and

Thyasira sarsi: Bivalve mollusc typically found in the north-central North Sea and associated with hydrocarbon enriched sediments.

With the exception of the bivalve mollusc Arctica islandica and the potentially the cold water coral Lophelia pertusa, the fauna of the Brae Area does not contain large, long lived species. Arctica islandica is widely distributed in the North Sea, though the Arctica found in the seabed surveys around the Brae area are typically small, young specimens (Marathon Oil UK LLC, 2013 (2)). Evaluation of available ROV footage of the Brae area infrastructure is currently ongoing and therefore the presence of biogenic reef forming organisms such as Lophelia spp has not yet been confirmed.

Fish, Shellfish and Cephalopods

Several fish species are known to present in the area surrounding the Brae Area and use the area for spawning and/or nursery grounds; these include the Norway pout (Tisopterus esmarkii), Nephrops, mackerel (Scomber scombrus), haddock (Melanogrammus aeglefinus) and blue whiting (Merlangus merlangus) (CEFAS, 2001; DTi (2001) (2); O&G UK, 1998). Spawning grounds extend over large areas of the North Sea, with eggs often developing on the seabed or in the water column, making them vulnerable to pollutants and disturbance.

A number of fish species known to be present within marine waters are protected under UK or international legislation, though few of these have distributions that extend into the offshore waters of the northern and central North Sea (DTi (2001) (2)). During zooplankton


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abundance the following protected elasmobranch species may occur in small numbers: basking shark (Cetorhinus maximus), tope (Galeorhinus galeus) and porbeagle (Lamna nasus). The common skate (Raja batis) and the Angel Shark (Squatina californica) can also be found at low densities.

Seabirds

Seabirds are present in the central and northern North Sea throughout the year, though densities in the Brae area tend to be lower due to the distance from coastal colonies.

Seabird densities in the Brae area are at their lowest in late spring/early summer when many birds are at their coastal colonies nesting and foraging distances out to sea are reduced (see Table A.1). Species and birds remaining in the offshore areas during late spring/early summer are often dominated by immature birds or non-breeders. At the end of the breeding season, the diversity and density of seabirds offshore increases as breeding birds leave their colonies and disperse into the North Sea. Birds and their chicks are particularly vulnerable to surface pollutants when they are gathering for breeding season and when they undergo a moult of primary feathers (which leaves them flightless) (i.e. Guillemots are most sensitive during July during their moult).

Table A.1: Seabirds likely to be present in the area of the Brae Area

Species Months Present in the North Sea

Fulmar (Fulmarus glacialis) All year

Gannet (Morus bassanus) May to February

Common gull (Larus canus) July – February

Herring gull (Larus argentatus) July – April

Great black-backed gull (Larus marinus) November – February

Kittiwake (Rissa tridactyla) All year

Guillemot (Uria aalge) All year

Little auk (Alle alle) November – February

Puffin (Fratercula arctica) April – September

Source: Stone et al, 1995

Marine Mammals

Twenty seven species of cetacean (which include whales, dolphins and porpoises) have been recorded in the waters around the British Isles, although only seven are regularly sighted in proximity of the Brae area. The most commonly sighted species is the harbour porpoise (Phocoena phocoena), though the range of the Atlantic white-sided dolphin (L. actus), white-beaked dolphin (Lagenorhynchus albirostris), Risso’s dolphin (Grampus griseus), killer whale (Orcinus orca), minke whale (Balaenoptera acutorostrata) and long-finned pilot whale (Globicephala melas) are also known to extend into the North Sea (Joint Nature Conservancy Committee (JNCC), 2003).

The most abundant species in the North Sea (including grey and harbour seals, minke whales, harbour porpoises and white-beaked dolphins) are important predators, influencing


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the food chain by feeding on a wide range of prey including a number of commercially important fish species (CEFAS, 2001) .

Designations

Seabed pockmarks supporting benthic communities rare to the North Sea are known to exist in the area immediately surrounding the Braemar infrastructure, including the designated Braemar Pockmarks Special Area of Conservation (SAC). This SAC has been described as ‘a series of crater-like depressions on the sea floor reflect the Annex I habitat ‘Submarine structures made by leaking gases’. Braemar pockmarks SAC has a global assessment grade of A (i.e. excellent conservation value) (JNCC, 2012), with a specific benthic assemblage associated with the carbon structures. The boundary of the SAC overlaps with the location of the Braemar infrastructure.

The occurrence of seabed pockmarks indicates potential gas or fluid release, causing suspension and winnowing of sediments and carbon structures. Pockmarks are recognised as potentially providing sheltered habitats for a variety of marine organisms, as well as being active gas seeps which may be of ecological significance due to:

potential utilisation of methane and its by-product, hydrogen sulphide, by chemosynthesisers; and

formation of hard substrate suitable for colonisation by certain benthic organisms.

Commercial Fisheries

The North Sea is an important fishing ground, with Peterhead the main landing port for the Brae area. The commercial species comprise (Xodus 2015; CEFAS, 2001):

pelagic species such as herring (Clupea harengus), mackerel (Scomber scombrus), horse mackerel (Trachurus trachurus);

demersal species such as cod (Gadus morhua), haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus) and saithe (Pollachius virens); and

shellfish such as Nephrops(Nephrops norvegicus).

Spawning and nursery grounds for various commercially important species are located in the vicinity of the Brae area, including: cod, haddock, Norway pout, saithe, nephrops and mackerel (Xodus, 2015).

Commercial fishing in the vicinity of the Brae area is dominated by demersal and shellfish fisheries, with fishing effort peaking during the spring and autumn (Xodus, 2015). The pelagic fishery peaks for herring in May to September and for mackerel in August to February (Xodus, 2015).

The gear types used for fishing in the Brae area are trawlers and seine nets which were found to account for 100 % of fishing effort in terms of fishing days from 2009 – 2013 (within ICES rectangle 46F1). The shellfish (Nephrops) fishery is the most productive in terms of landings value and the pelagic fishery is the most productive in terms of tonnage (Xodus, 2015).

The average annual economic value of fish landings within 12 nm of each jacket is £1,058,842; this represents a small component (0.2%) of the total landings value by Scottish vessels in 2013, highlighting the relatively low commercial value of the study area (Xodus 2015).


Scoping Report


Other Sea Users and Recreation and Tourism

The North Sea contains some of the busiest shipping routes in the world (DTi (2002) (3)) though a significant proportion of the shipping activity consists of ferries and vessels on fixed routes. A small proportion of peacetime military exercises also takes place within the North Sea, though these activities are mainly concentrated off the south coast of the UK.

The North Sea has been extensively explored for oil and gas, with several production fields currently in operation. Infrastructure comprises platforms (including topsides and jackets), pipelines, drilling templates, drill cuttings piles and other associated infrastructure. Oil and gas activities have been known to result in drilling discharges from exploration and development wells, produced water discharges, accidental oil spills and various other minor discharges (DTi (2002) (3)).

There are no military uses known in the vicinity of the Brae area. The Atlantic Crossing Telecommunication cable is charted to the north of the Brae area.

In respect of recreation and tourism, activities in the offshore North Sea are limited to the occasional yachts in passage.

Marine Archaeology

No designated wreck sites or known marine archaeological features are located within the Brae Area (DTi (2002) (3)).

References

Basford, D J., Eleftheriou, A., and Raffaelli, D., (1990). The infauna and epifauna of the northern North Sea. Netherlands Journal of Sea Research, Vol 25, 165 – 173.

BMT Cordah for CNR International (2013): Environmental Assessment of Options for the Management of the Murchison Drill Cuttings Pile. Rep Ref: A.CNR.038. CNRI Ref. MURDECOM_BMT_EN_STU_00132.

BP (2011): Miller Decommissioning Programme. MLR-A-D0-PM-PRO-00217.

CEFAS (2001): North Sea Fish and Fisheries, Technical report TR_003.

CNR International (2013): Murchison Facilities Decommissioning Environmental Statement. Revised Post-Statutory Consultation. MURDECOM-BMT-EN-REP-00198.

CNRI, 2012. Murchison Decommissioning Comparative Assessment report. Murdocom_CNR_PM_REP_00225.

Council Directive 92/43/EEC on the Conservation of Natural Habitats and of wild fauna and flora.

Curtis, T. Nesse, S. and Picken, G,B. (2001): Guidelines for Energy and Emissions Calculation in Offshore Decommissioning. Society of Petroleum Engineers (SPE). SPE 66498.

DECC (2011). Decommissioning of Offshore Oil and Gas Installations and Pipelines under the Petroleum Act 1998.

DECC (2009): Guidance Notes on the Offshore Petroleum Production and Pipelines (Assessment of the Environmental Effects) Regulations 1999 (as amended).

DECC (2001), Strategic Environmental Assessment of the “Mature Areas of the Offshore North Sea”, SEA 2, Consultation Document.


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Department of Trade and Industry (DTi) (2001): Technical Report TR_003, Technical Report Produced for Strategic Environmental Assessment – SEA2, North Sea Fish and Fisheries.

DTi (2001) (2): Strategic Environmental Assessment - SEA2, Technical Report 003 - Fish & Fisheries.

DTi (2002) (3): Strategic Environmental Assessment - SEA2 Technical Report 007 - Existing activities.

ENVIRON (2014). Brae Field Decommissioning EIA Strategy.

EUNIS Habitat classification (2007) – Revised descriptions 2012. Excel spreadsheet. http://www.eea.europa.eu/data-and-maps/data/eunis-habitat-classification#tab-european-data.

Fairfield Energy (2012): Dunlin Alpha Decommissioning Environmental Statement and Environmental Impact Assessment.

FUGRO EMU Ltd (Fugro), 2013. Brae Bravo Cuttings Pile Characterisation Survey UKCS Block 16/7a. Fugro EMU Doc Ref J/1/20/2386-1(3)

FUGRO EMU Ltd (Fugro), 2013 (2). Brae Bravo Environmental Monitoring Survey UKCS Block 16/7A. September 2013. Project Number J/1/20/2386

FUGRO EMU Ltd (Fugro), 2015. Brae Alpha Pre-Decommissioning Environmental Survey UKCS Block 16/7A. Fugro EMU on behalf of Marathon Oil Decommissioning Services LLC. March 2015 Doc Ref J/3/20/2805

FUGRO EMU Ltd (Fugro), 2015 (2). East Brae Cuttings Pile Characterisation Survey UKCS Block 16/3A. April and May 2015. Project Number J/3/20/2805

FUGRO EMU Ltd (Fugro), 2015 (3). Brae Field Cuttings Pile Leachate Analysis Report, November 2015, Project Number J/3/20/2805

Gatliff, R.W., Richards, P.C., Smith, K., Graham, C.C., McCormac, M., Smith, N.J.P., Long, L., Cameron, T.D.J., Evans, D., Stevenson, A.G., Bulat, J. and Ritchie, J.D. 1994. United Kingdom offshore regional report: the geology of the Central North Sea. HMSO, London.

Hartley, J.P. (2005) Seabed Investigations of Pockmark Features in UKCS Block 16/3. Report to Joint Nature Conservation Committee. Aberdeenshire: Hartley Anderson Marathon Oil (October 2014) Brae Field Decommissioning Slide Pack.

Joint Nature Conservation Committee (2012). Braemar Pockmarks SAC Selection Assessment: Version 4.1.

Joint Nature Conservation Committee (2003), Atlas of Cetacean distribution in north-west European waters.

Marathon Oil UK LLC. (2013). Corporate Responsibility (CR) Risk Management.

Marathon Oil UK LLC (2013) (2): NCS 3D mapping Survey of Brae Alpha, Brae Bravo and East Brae Cuttings Piles. Marathon Oil UK LLC. (2009) West Brae Production Consent Environmental Statement.

Marathon Oil UK LLC, 2008. OSPAR Recommendation 2006/5 in a Management Regime for Offshore Cuttings Piles: Stage 1 Screening of the Cuttings Piles at Marathon UK Ltd North Sea installations. Marathon Oil Decommissioning Services LLC. June 2008, Aberdeen

Marathon Oil UK LLC. (2002). Braemar Field Development Environmental Statement.

Oil and Gas UK (2014): HSO88 Guidance on Risk Related Decision Making Issue 2.


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Oil and Gas UK (2013). Decommissioning of Pipelines in the North Sea Region.

Oil & Gas UK (1998): Fisheries Sensitivity Maps in British Waters.

OSPAR Commission for the Protection of the Marine Environment of the North-East Atlantic (2000): Quality Status Report 2000 Region II Greater North Sea.

OSPAR Commission for the Protection of the Marine Environment of the North-East Atlantic (1998) Decision 98/3 on the Disposal of Disused Offshore Installations. Ministerial Meeting of the OSPAR Commission. Sintra 22/23 July 1998.

Stone, C.J. et al, (1995), An Atlas of Seabird Distribution in North-West European waters, 326 pages, A4 softback, ISBN 1 873701 94 2.

UKOOA, 2000. Phase I Summary Report. UKOOA Decommissioning Committee. January 2000, Aberdeen, Doc Ref 29003500

UKOOA, 2000(2). Phase II Research & Development Programme. UKOOA Decommissioning Committee. August 2000.

Xodus Group (2014) (1): Brae Bravo Comparative Assessment: Comparison of Energy Use and Emissions. A-1000057-S02-REPT-004.

Xodus Group (2014) (2): Brae Bravo Decommissioning: Comparative Assessment. Comparison of Underwater Noise Emissions and potential impact. A-10000057_S02_REPT_006.

Xodus Group (2015) Fishing Intensity & Socioeconomic Study. A-100057-S03-REPT-003.


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Annex B: Preliminary Scoping Parameters: Frequency/Likelihood; Magnitude and Environmental Effect/Risk Matrices


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Evaluating Potential Frequency

The criteria used to evaluate frequency in respect to planned activities are set out within Table B.1 below.

With respect to accidental events, rather than frequency, the likelihood of an identified risk occurring has been considered. The criteria used to evaluate likelihood of an accidental event occurring is also set out within Table B.1 below.

Table B.1: Frequency/Duration of an Activity (Planned) / Likelihood (Accidental) of the Activity

Frequency/Duration of an Activity (Planned Activities)

Likelihood (Accidental Events)

1: High frequency (activity occurring multiple times (>3) daily or for more than 3 hours daily or for a duration of > 1 year).

1: High - More than 10 times in Project Lifetime.

2: Medium frequency (activity occurring at least once a day or for a period of up to 3 hours daily or for a duration of > 6 months but < 1 year).

2: Medium - 5 – 10 times in Project Lifetime.

3: Low frequency (activity occurring at least once a week or for a duration of > 7 days but < 6 months).

3: Low - 3 – 5 times in Project Lifetime.

4: Infrequent (activity occurring at least once a month or one off event over project lifetime for > 24 hours but < 7 days).

4: Infrequent - Twice in Project Lifetime.

5: Highly infrequent (less than a monthly occurrence or one off event over project lifetime for < 24 hours).

5: Highly Infrequent/Remote – Unlikely to occur in the Project Lifetime, once or never.

Evaluating Potential Magnitude

The magnitude of the potential change, based on scale of high, medium, small, neutral and positive/no change based on an assessment across three categories, as set out in Table B.2.

Table B.2: Magnitude of the Change

Magnitude Description

1: High If an identified impact would:

Result in the complete loss of, or loss of integrity and/or functionality of an environmental feature; result in national or international concerns from stakeholders.

Major consequences to the environment.

2: Medium If an identified impact would:

Result in loss of a significant proportion of an environmental feature with potential risk to integrity and/or functionality of that feature; result in regional concerns from stakeholders.

Moderate consequences to the environment.


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Table B.2: Magnitude of the Change

Magnitude Description

3: Small If an identified impact would:

Result in loss of small parts of an environmental feature, not affecting integrity and/or functionality; result in local concerns from stakeholders.

Minor consequences to the environment.

4: Neutral If the activity under consideration follows best practice guidance, is anticipated to have negligible impact on the receiving environment and there is limited interest from stakeholders.

No or very minor consequences to the environment.

5: Positive/No Impact

If an identified impact would result in:

Long-term improvement of an environmental feature, improving its functionality; and/or

Long-term improvement of ecosystem services, improving functionality.

If an impact would have:

No impact on environmental features, and therefore have no effect on their integrity and/or functionality.

Table B.3 summarises the activity/receptor interaction and sets out the basis for allocating the potential environmental effect or risk category. A summary definition of each category is provided in Table 4.1.

Table B.3: Scoping Effect Category Matrix

Frequency/Likelihood

Magnitude 1 2 3 4 5

1 High High High Medium Medium

2 High High Medium Medium Low

3 Medium Medium Low Low Negligible

4 Low Low Negligible Negligible Negligible

5 No Impact/ Positive

No Impact/ Positive

No Impact/ Positive

No Impact/ Positive

No Impact/ Positive


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Annex C1: Activity/Receptor interactions scoped as ‘high’ potential for significant environmental effect


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Table C.1 : Activity/receptor interactions scoped in for consideration within the EIA

Reference (see Table 5.1 and 5.2)

Technical Study Area

Activity/receptor interaction

Infra- structure affected

Initial effect category5

Discussion

C1.1

Seabed Disturbance (Designated Sites and Species)

Removal of Braemar wellhead and flowlines to East Brae and potential effects on seabed pockmarks, benthic communities and natural seabed sediments.

Braemar infrastructure and flow lines

Medium to High In the Brae Area, the seabed comprises silt and clay (mud) in the surface few metres, underlain by increasingly stiff silts and clays. Seabed pockmarks supporting benthic communities rare to the North Sea are known to exist in the area immediately surrounding the Braemar wellhead, suspended well and associated flowlines. The Braemar wellhead is located approximately 90 m south of the Braemar pockmarks SAC designation boundary, and the Suspended Well (16/03c-12) is located within the SAC boundary.

Seabed disturbance and subsequent resettlement has the potential to disturb and/or smother benthic organisms. Benthic assemblage associated with the pockmarks may also be subject to localised disturbance/smothering.

On this basis the potential for significant effect is considered to be medium to high. This issue will be considered in more detail as part of the EIA.

Consideration of the likely effects on the Braemar Pockmarks Special Area of Conservation (Habitat Regulations

5 In the case of ‘accidental events’ the risk grading could be low – high depending on the extent of any accidental event.


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Discussion

Assessment (HRA)) will be taken forward as part of the EIA process.

C1.2 Noise Effects (fish, marine mammals, seabirds)

Full or partial removal of the platform jacket structure and potential to affect noise sensitive species of marine mammals.

Brae Alpha, Brae Bravo and East Brae

High It is anticipated that noise generation from both cutting operations and from vessel activity would result in underwater noise which would represent a potential change from ambient conditions.

These works have the potential to result in noise impacts to marine mammals (disturbance and/or displacement). Early calculations completed in relation to this activity (Xodus, 2014) indicate the potential for behaviour disturbance to marine mammals from cutting over a range of up to 10 km. Disturbance from vessel noise may extend up to 3 km for larger crane vessels. As such, jacket removal is considered to have a high potential to result in significant environmental effect on marine mammals.

See consideration of effects on fish under reference C2.6. There is considered to be a medium potential for jacket removal to affect noise sensitive species of fish and seabirds. This is considered further in Annex D2.

C1.3 Removal of subsea installations through the use of explosives and the potential for

Central Brae template

High These works have a high potential to result in significant noise effects to marine mammals (disturbance and/or displacement). Further consideration will be given to the use of explosives as part of the EIA process.


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Discussion

noise effects on marine mammals.

C1.4 Water Quality Effects (water quality, plankton, fish, shellfish, marine mammals)

Removal or disturbance to the drill cuttings piles either through:

i) removal or relocation of the drill cuttings piles; and

ii) removal of the steel jacket footings, or removal of the subsea installations directly associated with the platforms e.g. umbilicals, risers, cables, pipelines/flowlines, drill templates. Potential to mobilise sediments and for elevated levels of contaminants in the water column, with secondary effects on marine species (benthos, fish and shellfish) and water quality.


High Stage 1 OSPAR assessment (Marathon, 2008) concluded that drill cuttings piles at all three platforms fall below the specified OSPAR thresholds and therefore may be left in situ to degrade naturally.

Removal or disturbance of the drill cuttings piles would result in remobilisation of contaminants beneath the platforms with resultant localised changes to sediments, organic carbon content and water quality with contaminants in the water column. This has the potential to indirectly affect benthic species, fish and shell-fish and marine mammals.

The scope of this assessment will be developed in parallel with ongoing Net Environmental Benefit Analysis (NEBA) in support of the Comparative Assessment for cuttings pile management.


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Discussion

C1.5 Accidental Events Accidental release of contaminants during topside preparation affecting water quality with secondary effects on marine ecosystems.


Low – High Topside preparation has been taken to include activities required to ensure hydrocarbons and chemicals have been removed; all processing plant has been shut down and isolated from the reservoir; and all conductors, casings, tubing and other well equipment removed. There is the potential for an unplanned spill (hydrocarbons, hazardous materials or cleaning materials) which would result in elevated levels of contaminants reaching water column and seabed. Scale of spill would be dependent on activity and chemicals/contaminants being handled, as such there is range of risk from low to high. Further consideration will be given to the potential for significant environmental effect from accidental or unplanned events as part of the EIA process.

C1.6 Risk of accidental spills associated with vessel activities.

Risk of dropped objects, particularly during lift operations.

Topside preparation, removal, jacket removal and subsea installation removal

Drill cuttings piles (remove/relocate)

Low – High A range of vessels of types, sizes will be required to facilitate decommissioning activities. Risk of accidental spills from vessel activity will remain throughout the decommissioning programme particularly associated with, but not limited to, topside preparation, topside removal and jacket removal. Further consideration will be given to the potential for significant environmental effect from accidental or unplanned events as part of the EIA process.


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Discussion

Further consideration of the potential effects associated with dropped objects during the main lifts will be given within the accidental events section of the EIA.


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Annex C2: Activity/Receptor interactions considered ‘medium’ potential for significant environmental effect and therefore taken forward to Stage 2 scoping


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Table C.2: Activity/receptor interactions for further scoping consideration




Infrastructure affected

Initial Effect Category

Discussion

C2.1 Seabed Disturbance Effects (marine benthos, geology, natural seabed sediment and drill cuttings pile)

Disturbance to natural seabed sediments and drill cuttings pile sediments during jacket removal with or without footings) and removal or preparation of footings, risers, umbilicals etc. to leave in situ.

Potential effects on both soft sediment and hard substrate benthic communities.

Localised disturbance to seabed during removal of flare stack jacket at Brae Bravo and potential effects on benthic communities.

Effects associated with drill cuttings pile removal or relocation.

Brae Alpha, Brae Bravo, East Brae

Low - Medium

In the event of derogation, certain decommissioning activities will be required in order to leave risers, umbilicals and other infrastructure in situ underlying the known extent of drill cuttings piles beneath Brae Alpha, Brae Bravo and East Brae.

An estimated 1,400 Te each (Brae Alpha and Brae Bravo) and 460 Te (East Brae) of hard substrate benthic assemblage (not designated) on the jacket legs is anticipated to require removal by water jetting prior to jacket lift. This could result in the loss of potentially ecologically valuable hard substrate habitat and/or disturbance to natural seabed sediments.

Potential disturbance to natural seabed sediments and/or drill cuttings pile sediments during decommissioning activities which mobilise sediment into the water column (temporary local increase in turbidity). Potential indirect effects include smothering benthic communities (including Priority Marine Features as defined by the Marine (Scotland) Act 2010. Potential for water quality effects are considered separately.

Taken forward into Stage 2: detailed scoping

C2.2

Localised disturbance to seabed during removal of area wide subsea installations affecting benthic communities and natural seabed sediments.

Central Brae template, West Brae and Sedgewick wellheads and

Low - Medium

Seabed sediment disturbance by removal of infrastructure as well as settlement of marine growth removed from infrastructure by water jetting prior to removal, and potential for effects on benthic communities.



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Discussion

Braemar Infrastructure

C2.3

Localised disturbance to seabed in event of pipeline/cable, flowline/umbilical removal affecting benthic communities, natural seabed sediments and water quality.

Pipeline/cable, flowline/umbilical

Medium It is known that a combination of surface laid, trenched and rock-covered sections of pipeline exist. Removal of surface laid pipelines would result in surface silt being mobilised into the water column, however this would be expected to settle quickly and in a similar composition to that found before the pipeline removal. It has been assumed that adequately trenched or rock-covered pipelines would remain in place in accordance with DECC guidelines (DECC, 2011).

Overall there is considered to be a medium potential for significant effect.


C2.4 Underwater noise

Removal of pipeline/ cable / flowline / umbilical, risers and other subsea infrastructure directly associated with the platform and potential to affect noise sensitive species including fish and marine mammals.

Pipeline/ cable / flowline / umbilicals associated with Brae Alpha, Brae Bravo, East Brae

Medium Vessel activity, and physical removal of pipeline /cable / flowline / umbillical, may result in underwater noise from cutting operations which would represent a potential change from the ambient conditions during operations.


C2.5 Topside removal and potential to affect noise sensitive species including


Medium It is anticipated that noise generation from vessel activity would result in underwater noise which would represent a potential change from ambient conditions.


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Discussion

fish, seabirds and marine mammals.


C2.6 Jacket removal and potential to affect noise sensitive species of fish and seabirds.

Drill Cutting Piles (Remove/ Relocate


Medium It is anticipated that noise generation both from cutting activity, and associated vessel activity would result in underwater noise which would represent a potential change from ambient conditions.


C2.7 Removal of pipelines/ cables / flowlines / umbilicals and the potential to affect noise sensitive species including fish and marine mammals.

Pipelines/ cables / flowlines / umbilicals (area wide)

Medium Vessel activity, and physical removal of pipeline /cable / flowline / umbilical, may result in underwater noise from cutting operations which would represent a potential change from the ambient conditions during operations.



Localised disturbance of drill cuttings pile contaminants when left in situ

Steel Jacket – Partial Removal


There would be a limited potential for disturbing the drill cuttings piles associated with activities such as water jetting off the jacket structures. Further consideration is given to potential for significant effects in Stage 2: detailed scoping.


Localised seabed disturbance during the area wide removal of pipelines/cables / flowlines / umbilicals and other subsea installations resulting in potential direct effects on water quality

Pipelines/ cables / flowlines / umbilicals (area wide) and other subsea installations

Low - Medium

Seabed disturbance during cutting and lifting activities leading to local mobilisation of sediments with effects on water clarity (turbidity) and quality in a local area, result in changes water column, with potential effects on plankton.



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Discussion

and indirect effects on plankton, fish and shellfish and marine mammals.

Any discharges to sea from the cleaning of pipelines/flowlines will be managed and assessed under the existing permitting regime (e.g. The Offshore Petroleum Activities (Oil Pollution

Prevention and Control) Regulations 2005 (as

amended), UK Oil Pollution Prevention, Offshore Chemical Regulations 2002 Chemical Permit). As such, these discharges have been scoped out of the decommissioning EIA.

C2.10 Socio-economic and Other Effects (commercial fisheries, shipping/ navigation, recreation, marine archaeology)

Potential for steel jacket footings presenting a long term hazard to demersal fisheries.


Medium There is already a 500 m safety zone around surface infrastructure in place, and it is assumed that this will remain in place for the duration of the decommissioning works. This represents no change from existing conditions.

Following removal of the jacket (with the a derogation agreed to leave the footings in situ), the footings and cutting piles would continue to present an obstruction on the seabed preventing demersal trawl fishing As such it is proposed that the safety zone would be retained to mitigate fishing risks.

Taken forward into Stage 2: detailed scoping to consider potential socioeconomic effect.

C2.11 Atmospheric Emission Effects (energy use, climate change, air quality)

Emissions to air will occur as a result of vessel movements associated with topside removal, jacket removal (including Brae Bravo flare stack), drill cuttings pile removal

All infrastructure Medium Potential for environmental effect relates to energy use (resource use) as a result of vessel movements. Climate change effects and air quality effects relate primarily to CO2 emission as a primary greenhouse gas and also NOx and particulates. Further consideration is given to natural resource use, air


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Discussion

and pipeline and other subsea installation removal, with implications for energy use.

quality and climate change effects in Stage 2: detailed scoping.


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Annex C3: Activity/Receptor interactions considered ‘low’ potential for significant environmental effect and therefore scoped out of the EIA


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Table C.3: Activity/receptor interactions scoped out for consideration within the EIA






Discussion

C3.1

Designated Sites and Species Disturbance

Transportation of Materials and Personnel to and from Brae Area


Negligible Transportation of Materials and Personnel to and from the Brae Area would be conducted primarily by helicopter with infrequent vessel use. There is no potential for interaction with designated sites or species.

Birds are considered to be sensitive to airborne noise (as a result of helicopter movements) which could cause displacement. However given the low frequency at which movements would occur and low magnitude of change (low consequence) for bird populations it is considered unlikely to result in more than a negligible impact.

C3.2



No Impact Topside preparation activities would have no interaction with designated sites or species.

C3.3

Subsea Installations Removal, including removal of marine growth by water jetting

Brae Alpha, Brae Bravo, East Brae, Area Wide infrastructure (excluding Braemar)

Low Excluding the Braemar infrastructure, there would be no interaction between the removal of subsea installations and designated sites.

Displacement or disturbance of species of interest from noise and Vessel Presence and decommissioning activities are likely to be low

6 In the case of ‘accidental events’ the risk grading could be low – high depending on the extent of any accidental event.


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Discussion

frequency, short duration and as such small magnitude of change for this activity.

An evaluation of available ROV footage of the Brae Area infrastructure has been completed. No evidence of biogenic reef forming organisms e.g. Lophelia spp has been identified. Further pre-decommissioning survey to check for the presence of designated species would be completed prior to the decommissioning activities taking place.

Overall the potential for significant environmental effect is considered to be low.

C3.4

Topsides Removal Brae Alpha, Brae Bravo, East Brae

No Impact Topside removal activities would have no interaction with designated sites or species.

C3.5

Drill Cutting Piles (Remove/ Relocate)


No Impact No impacts are predicted during standard operating conditions on designated sites and species since there are no currently designated or proposed Special Areas of Conservation or Special Protection Areas in the vicinity of the Brae Alpha, Brae Bravo or East Brae drill cuttings piles.

C3.6

Drill Cutting Piles (left in situ)


No Impact Drill cuttings piles left in situ would have no interaction with designated sites or species.

C3.7

Steel Jacket – Full Removal, including removal of marine


Low Jacket removal activities would have no interaction with designated sites.

Displacement or disturbance of species of interest from noise and Vessel Presence and


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Discussion

growth by water jetting

decommissioning activities are likely to be low frequency, short duration and as such small magnitude of change for this activity.



C3.8

Steel Jacket – Partial Removal


Low Jacket removal activities would have no interaction with designated sites.

Displacement or disturbance of species of interest from noise and Vessel Presence and decommissioning activities are likely to be low frequency, short duration and as such small magnitude of change for this activity.



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Discussion

Overall the potential for significant environmental effect is considered to be low...

C3.9

Pipeline/ Cable/ Flowline and Umbilical (removal or left in situ)

Area Wide Infrastructure (excluding Braemar and East Brae tie-back)

Low Displacement or disturbance of species of interest from noise and Vessel Presence and decommissioning activities are likely to be low frequency, short duration and as such small magnitude of change for this activity.


Where infrastructure would be left in place, there would be no potential for interaction with designated sites or species.


C3.10

Seabed Disturbance Effects (marine benthos, geology, natural seabed sediment

Transportation of Materials and Personnel to and From Brae Area


Negligible Seabed disturbance is likely to be negligible with the majority of transportation using helicopter flights with occasional/ infrequent vessel movements.

C3.11 Topsides Preparation


No Impact No seabed disturbance is predicted during topsides preparation - all operations would be conducted above water.


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Discussion

C3.12

and drill cuttings pile)

Topsides Removal Brae Alpha, Brae Bravo, East Brae

Low There is the potential for physical disturbance to the seabed and suspension of sediment into the water column associated with anchoring vessels. It is considered that site survey data would be used to select appropriate anchor locations resulting in a small magnitude of change and, overall, a low impact.

C3.13



Low Stage I OSPAR assessment (Recommendation 2006/5) undertaken for each of the drill cuttings piles concludes that drill cutting pile sediment fall below the OSPAR screening thresholds. Therefore the drill cutting piles may be left in situ to degrade naturally.


C3.14

Pipelines/cables, flowlines/umbillical (left in situ)

Area wide subsea pipelines/cables, flowlines/umbilicals

No Impact - Low It has been assumed that adequately trenched or rock-covered pipelines/cables, flowlines/umbilicals would remain in situ in accordance with DECC guidelines (DECC, 2011). This would result in no impact on natural seabed sediments or benthic communities. Additional rock covering of infrastructure may be required; however this would be over a local extent and is considered to represent a low potential to result in significant environmental effect.


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Discussion

C3.15 Noise effects (fish, marine mammals, seabirds)



Negligible - Low Low frequency and small magnitude disturbance to birds flying in the area due to the noise produced by the helicopters. Assessed as low potential for significant environmental effect.

Infrequent and small magnitude of change associated with vessel movements required to transport materials/personnel to and from the Brae Area. Majority of transportation will be by helicopter. Assessed as negligible potential for significant effect on fish or marine mammals.



Low Vessel activity associated with decommissioning has been considered against the existing vessel activity in the area. Topside decommissioning will result in infrequent short term vessel noise, which is unlikely to represent more than a small/local change from the ambient conditions.

As a result a low potential for significant environmental effect has been identified.

C3.17 Drill Cutting Piles (left in situ)


No Impact No underwater noise source if drill cuttings piles left in situ. No impact.

C3.18 Pipeline/ cable/ flowline/ umbilical – left in situ

Area wide infrastructure

No Impact No underwater noise source if installations left in situ. No impact.


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Discussion




No Impact There are no planned discharges to sea associated with transportation of materials and personnel by helicopter, and negligible pollution to water quality associated with infrequent vessel use. No impact is anticipated.



No Impact Any discharges to sea from topsides preparation will be managed and assessed under the existing permitting regime (e.g. The Offshore Petroleum Activities (Oil Pollution Prevention and Control) Regulations 2005 (as amended), UK Oil Pollution Prevention, Offshore Chemical Regulations 2002 Chemical Permit). As such, these discharges have been scoped out of the decommissioning EIA.


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Discussion

C3.21 Topsides Removal Brae Alpha, Brae Bravo, East Brae

No Impact Topsides will be free from gross hydrocarbon. Other stored chemicals or potential contamination sources present during operation of the platforms will have been removed during the Topsides preparation for decommissioning. As such there will be no potential source of pollution associated with the topside removal activity. Any discharges of waste water, chemicals and oils to sea will be managed and assessed under the existing permitting regime (e.g. (Oil Pollution Prevention and Control) Regulations 2005 (as amended), UK Oil Pollution Prevention). As such, these discharges have been scoped out of the decommissioning EIA.

C3.22 Pipeline/ cable/ flowline/ umbilical – left in situ

Area wide infrastructure

No Impact Any discharges to sea from the cleaning of pipelines/flowlines will be managed and assessed under the existing permitting regime (e.g. The Offshore Petroleum Activities (Oil Pollution Prevention and Control) Regulations 2005 (as amended), UK Oil Pollution Prevention, Offshore Chemical Regulations 2002 Chemical Permit). As such, these discharges have been scoped out of the decommissioning EIA.


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Discussion




No Impact Operations would take place only on the platforms. There is no potential for interaction with other sea users.


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Platform subsea installations removal;

Topsides Removal;

Drill Cutting Piles (Remove/ Relocate;

Drill Cutting Piles (left in situ);

Steel jacket – full removal;

Subsea Installations Removal;

Pipeline/ cable/ flowline/ umbilical – removal and left in situ


No Impact There is a 500 m safety zone in place around the platforms, and it is assumed that this will remain in place for the duration of the decommissioning works to avoid conflict with navigation or commercial fishery interests. As such there would be no change from ambient conditions.

Drill cuttings would only be left in situ where a derogation was in place to leave the steel jacket footings in place. In this scenario the 500 m safety zone would remain in place around the platforms, in order to prevent interaction between commercial fishing and the remaining contaminated sediments associated with the drill cuttings piles.

Where pipelines / cable/ flowline/ umbilical are proposed to be left in situ it is assumed that they would be either trenched or suitably rock covered such that there would be no interaction with commercial fishery interests. It has been assumed that adequately trenched or rock-covered pipelines would remain in place in accordance with DECC guidelines (DECC, 2011) and that there would be no potential to create berms on the seabed.

There are no RYA racing areas, sailing areas, recreational cruising routes, dive sites, sea angling sites, windsurfing locations or education research locations in the area.

No designated wreck sites or known marine archaeological features are located within the Brae Area.

Full removal of infrastructure would allow the area to potentially become suitable for pelagic


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Discussion

and demersal fishing. No Impact / potential positive effect.

C3.25 Atmospheric Emission Effects (energy use, climate change, air quality)


Topside Preparation


Pipelines/ cables/ flowlines/ umbilicals – removal and left in situ


Negligible Energy use and emissions associated with helicopter or infrequent vessel movements during the decommissioning works would comprise a small or neutral magnitude of change resulting in minor or very minor consequences in terms of air quality or climate change effect. Given the meteorological conditions, emissions will likely disperse rapidly. All vessel will comply with MARPOL 73/78 Annex VI on air pollution; plant will comply with relevant air pollution regulations (The Offshore Combustion Installations (Prevention and Control of Pollution) (Amendment) Regulations 2007.

On this basis the overall potential for significant environmental effect is considered to be negligible. The potential for significant effect as a result of this activity/receptor interaction has therefore been scoped out of the EIA.

C3.26 Accidental Events



Low There is only potential for accidental spills in the event of a transport accident. This is considered to be a highly infrequent/remote possibility with a potential medium magnitude of change. Overall the risk of accidental spill is considered low.


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Discussion

C3.27 Drill Cutting Piles (left in situ)


Low The only accidental event that might occur would be linked to dropped items or water jetting of steel jackets and other infrastructure resulting in unintended/unplanned disturbance to the drill cuttings piles. A Stage 1 OSPAR assessment (under the terms of OSPAR Recommendation 2006/5) was undertaken in 2008 (updated in 2015 following additional sampling) and concluded that the drill cutting piles located at all three platforms fall below the thresholds set out within this recommendation and could therefore be left in place to degrade naturally. Any accidental mobilisation of contaminants would be short term and localised, and therefore low risk.

C3.28 Accidental Events


Brae Alpha, Brae Bravo, East Brae and area wide subsea installations

Negligible It has been assumed that only adequately trenched or rock-covered pipelines would remain in place in accordance with DECC guidelines (DECC, 2011). Additional rock cover would be added where necessary to reduce the potential risk associated with ‘snagging’ of fishing nets.

The result is a negligible risk of significant environmental effect.


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Annex D1: Detailed Scoping Parameters: Sensitivity; Duration of Impact; Geographic Extent.


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Considering Potential Sensitivity

The sensitivity of the receptor is based on consideration of known information relating to the following four characteristics:

Adaptability (how well a receptor can avoid or adapt to an effect);

Tolerability (the ability of a receptor to be either affected or unaffected);

Recoverability (how well a receptor recovers following exposure to an effect); and

Value (the scale of importance).

These parameters would vary according to each technical discipline and thus, sensitivity is a concept that has been applied to individual disciplines/receptors based on professional judgement.

Considering Potential Duration of Effect

The duration of an effect is based on an assessment across four categories, long-term, medium term, short term and very short term as set out in Table D.1.

Table D.1: Duration of an Effect

Duration Description

1: Long Term Recovery to original state in more than 10 years, or not at all.

2: Medium Term Recovery to original state in more than a year, but less than 10 years.

3: Short Term Recovery to original state in more than one month, but less than a year.

4: Very Short Term Recovery to original state in less than one month.

Considering Potential Geographical Extent

The geographical extent of an impact is based on an assessment across three categories, local, regional and national/international.


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Annex D2: Summary of Stage 2 Scoping Outputs


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Table D.2: Summary of Stage 2 Scoping

Reference (table 6.1 and 6.2)




Stage 1 effect category

Discussion Stage 2 effect category

D2.1 Seabed Disturbance

Disturbance to seabed during partial removal of jackets, risers, pipelines (other than surface laid, see below) umbilicals, power cables and other subsea installations, with resultant potential effects on benthic communities, natural seabed sediments and cuttings pile sediments. Disturbance may also occur during preparation for the footings to be left in situ.

All (excluding Braemar)

Low - Medium

Seabed disturbance would occur throughout the duration of the decommissioning programme, associated with a range of proposed decommissioning activities. This would result in the potential mobilisation of sediment into the water column, including potential contaminants.

Geographical Extent

It is anticipated that impacts would be focused in proximity to the installation, though the potential for sediment and contaminant movement may be influenced by variations in localised water currents over time. Sediment would be expected to re-settle quickly as a result impacts would occur at a local scale only.

Sensitivity

Natural turbidity in the water column would be dependent on meteorological conditions and tides, but is not expected to be high. The seabed comprises silt and clay (mud) in the surface few metres, underlain by increasingly stiff silts and clays. (Hartley 2005).

Disturbance of the sediment in the surface area would be expected to be short term, with resettlement occurring rapidly, with limited potential for the formation of persistent mounds. Impacts would be focused in close

Low


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proximity to the installation/route of subsea infrastructure or cables.

Mitigation

Cutting and lifting operations associated with the removal of subsea infrastructure would be controlled by ROV to ensure accuracy in all activities and therefore minimise the potential for seabed sediment disturbance.

Summary

The potential for significant effect as a result of this activity/receptor interaction is considered low to positive and has therefore been scoped out of the EIA.

D2.2 Seabed disturbance

Disturbance to seabed during full removal of jackets, footings, drill cuttings piles.

All (excluding Braemar)

Low - Medium

Cuttings pile removal (to surface for onshore treatment and disposal) could be expected to result in 90 – 95% recovery rate of cuttings pile dredged material (BMT Cordah, 2013). However, assuming the use of a closed recovery system (CNRI, 2013), effects would arise as a result of the re-suspension of drill cuttings by placement of the suction dredge in the pile; and through) the likely requirement to back-flush the dredge in order to dislodge any debris that becomes lodged within the suction hose. Back-flushing of the suction dredge would be considered to be the worst case disturbance scenario, as it is expected that this would result in the discharge to sea of the

Low - Medium


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entire contents of the closed system hose, from the suction dredge to the vessel on the surface (CNRI 2012). In this regard, further assessment is required to evaluate the potential effect of back-flushing on the adjacent soft bottom habitat.

The benthic communities in the Brae Area typically comprise deeper water sand communities. Typical species may include Priority Marine Features as defined by the Marine (Scotland) Act 2010. The potential for significant effect on this assemblage remains scoped in to the EIA.

D2.3 Noise Topside removal; platform subsea installation removal and drill cuttings piles removal or relocation with the potential airborne noise to affect noise sensitive seabirds and underwater noise to affect fish and marine mammals.


Medium The frequent movement of vessels associated with current operations within the area indicate that a certain degree of habituation and tolerance in marine mammals to vessel related underwater noise can reasonably be assumed. Vessel movements associated with topside removal would be intermittent, spanning a period of time dependent on the final chosen method of removal. Vessel movement associated with the removal of drill cuttings piles has been estimated at 1928 workdays. Disturbance from vessel underwater noise may extend up to 3km for larger crane vessels. Noise from vessel activity may also displace/disturb seabirds within 100m (Xodus, 2014). Vessel noise is

Low


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not considered to be a significant source of disturbance to fish.

Impacts associated with vessel activity are likely to be temporary. Disturbance from vessel underwater noise may extend up to 3km for larger vessels Under these circumstances, should displacement or disturbance occur to an individual it is considered likely that these individuals would recover and return to the location following cessation of the decommissioning activity.

Seabirds have the potential to be affected by the noise and presence of vessels, either directly or indirectly through prey displacement. In general the Brae Area has lower densities of seabird activity in comparison to other areas of the central North Sea due to the distance from coastal colonies, with the lowest densities during late spring/early summer (Stone 1995). However the frequent movement of vessels and industrial activity in the area indicates that the bird species which habituate the Brae Area would be tolerant to vessel presence and associated noise impacts.

The potential for significant effect as a result of this activity/receptor interaction is considered to be low has therefore been scoped out of the EIA.


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D2.4 Pipeline and subsea installation removal and potential to produce underwater noise with effects on noise sensitive fish and marine mammals.

Pipelines and other subsea installations

Medium Marine mammals are considered to be highly sensitive and have the potential to be affected by the noise and presence of vessels, directly, or indirectly through prey displacement. In general, marine mammals are considered to show the highest sensitivity to noise, although effects on fish species such as cod and herring remain possible over 4-5km from source. All cetaceans are listed in Annex IV of the EC Habitats Directive (92/43/EEC) as species being in need of strict protection. In general, the area has lower densities of marine mammals than in other areas, though numbers are likely to increase during the summer months. It is noted that the North Sea contains some of the busiest shipping routes in the world, though the Brae Area is relatively light, dominated by oilfield supply boats and fishing boats. However, the frequent movement of vessels and industrial activities in the area indicates that the species present would be tolerant to vessel presence and associated impacts.

The duration or effects is considered to be short term due to the common occurrence of vessel movements in the North Sea, it is considered that should any impacts associated with displacement and disturbance occur, the species would recover and return

Medium


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to these locations at the cessation of the decommissioning activities.

Noise from the vessels and cutting activities may displace/disturb marine mammals (and to a lesser extent, fish) in the immediate vicinity and in the wider area (due to noise travelling long distances underwater).

Overall the effect of cutting operations means that the potential for significant effect remains medium and is scoped in to the EIA..

D2.5 Water Quality Effects (water quality, plankton, fish, marine mammals)

Localised disturbance of drill cuttings pile contaminants when left in situ and potential effects on benthic communities, natural seabed sediments and drill cuttings piles sediments.


Low - Medium

In the event that drill cuttings piles will be left in situ, impacts will be limited to localised seabed disturbance and subsequent resettlement of sediment associated with marine organisms (e.g. water jetting off structures) falling to the seabed and potentially disturbing the drill cuttings piles. Disturbance would be limited to the surface/upper layers of the drill cuttings piles where contamination as a result of natural remediation processes is already reduced. Stage 1 OSPAR assessment (Marathon, 2008) concluded that drill cuttings piles at all three platforms fall below the specified OSPAR thresholds and therefore may be left in situ to degrade naturally

The potential for significant effect as a result of this activity/receptor interaction has therefore been scoped out of the EIA.

Low


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D2.6 Socio-economic and Other Effects (commercial fisheries, shipping/navigation, recreation, marine archaeology)

Derogated footings presenting a long term hazard to demersal fisheries.


Medium The North Sea represents an important fishing ground in European and North Atlantic context, with Peterhead the main landing port for the activities including in the Brae Area. Commercial species comprise pelagic species (herring, mackerel, horse mackerel), demersal species (cod, haddock, whiting and saith) and shellfish (Nephrops). The gear types used for fishing are trawlers and seine nets which were found to account for 100 % of fishing effort in terms of fishing days from 2009 – 2013 (within ICES rectangle 46F1) (Xodus, 2015).

A 500 m safety zone around surface infrastructure is in place, and it is assumed that this will remain in place for the duration of the decommissioning works. This represents no change from existing conditions.

In the longer term, it has been estimated that full removal would result in fishermen regaining access to approximately 2,500 m2 (Xodus, 2015). In the event of derogated footings, the immediate area of the jacket footprint, approximately 70 x 50 m per platform would remain inaccessible, however consideration would be given to maintaining the existing 500 m safety zone.

In the event of derogation the presence of the footings would be marked on relevant charts and communicated to other sea users through

Low/Medium

(Scoped into Stage 3 Scoping to consider implications of comparative assessment analysis.)


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the normal communication channels (for example, FishSAFE).

It is recognised that the area around the platforms forms a very small part of the much greater Fladen Ground fishery, and therefore effort and landings from the area are low at a national UK level. Any short-term or long-term potential impacts from decommissioning (of platforms or other infrastructure, such as pipelines) should therefore be viewed in this overall context.

The potential for significant effect as a result of this activity/receptor interaction is considered likely to be low/medium at this stage. Further consideration will be given to the potential for significant effects following the completion of the Comparative Assessment studies and will be reported as part of the Environmental Statements.

D2.7 Atmospheric Emission Effects (energy use, climate change, air quality)

Emissions to air will occur as a result of vessel movements associated with subsea installations removal, topside removal, drill cuttings piles

All infrastructure Medium The greatest concern relates to the potential for emissions with global warming potential (GWP) and the contribution to climate change. Emissions with GWP anticipated as a result of Brae Area decommissioning activities include (but are not limited to) carbon dioxide (CO2) associated with vessel emissions. In addition nitrogen oxide (NOx) emissions associated with vessel emissions

Low


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removal, jacket removal with implications for energy use.

can result indirectly in an increase in ozone (03) and nitrous oxide (N20), with GWP.

Preliminary Energy Use and Emissions calculations have been completed to inform the Comparative Assessment process (Xodus, 2014 (1)) and will be given due account within the Comparative Assessment decision making process. As such the potential to minimise emissions to As Low as Reasonable Practicable (ALARP) is already inherent within the DP. The comparative consideration given to ensure ALARP options in terms of Energy Use and Air Quality will also be documented within the Alternatives/Comparative Assessment section of the ESs. Overall, the potential emissions associated with decommissioning would represent a reduction in emissions relative to the normal operational emissions associated with operating the Brae Area platforms and infrastructure.

Localised air quality sensitive receptors in close proximity to the Brae Area are limited. Human receptors will be limited to offshore operators on vessels and/or nearby infrastructure. Ecological receptors would be limited to seabirds which would be transient through the area.

Contributions of the emissions would be at a local scale, within approximately 100m of the


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source in addition, due to the offshore location and dominant wind climate (Beaufort 4 – 6) emissions would disperse rapidly.

All vessels will comply with MARPOL 73/78 Annex VI on air pollution; plant will comply with relevant air pollution regulations (The Offshore Combustion Installations (Prevention and Control of Pollution) (Amendment) Regulations 2007.

The potential for significant effect as a result of this activity/receptor interaction has therefore been scoped out of the EIA.


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Annex D3: Schedule of Mitigation Commitments


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Table D.3. Schedule of Scoping Stage Mitigation Commitments

Reference Activity/Receptor Interaction

Mitigation Commitment

Designated Sites/Species

Disturbance to biogenic reef forming species settled on hard surfaces during removal of jackets, footings, risers, pipelines, flowlines, umbilicals, power cables and other subsea installations.

An evaluation of available ROV footage of the Brae Area infrastructure has been completed. No evidence of biogenic reef forming organisms e.g. Lophelia spp has been identified on Brae Area infrastructure. Further pre-decommissioning survey to check for the presence of designated species would be completed prior to the decommissioning activities taking place.

Seabed disturbance

Disturbance to seabed during removal of footings, risers, pipelines, flowlines, umbilicals, power cables and other subsea installations, with resultant potential effects on benthic communities, natural seabed sediments and cuttings pile sediments. Disturbance may also occur during preparation for the footings to be left in situ.

Cutting and lifting operations associated with the removal of subsea infrastructure would be controlled by ROV to ensure accuracy in all activities and therefore minimise the potential for seabed sediment disturbance.

Underwater Noise

Topside preparation and removal and potential for vessel activity to affect noise sensitive species including seabirds, fish and marine mammals.

All equipment will be maintained to manufacturers’ specifications.

Number of vessels travelling or on standby in the Brae Area at any one time will be kept to a minimum.

Socioeconomic and Other Effects

Derogated footings presenting a long term hazard to demersal fisheries.

In the event of derogation the presence of the footings would be marked on relevant charts and communicated to other sea users through the normal communication channels (for example, FishSAFE).

The existing 500 m safety zone around each platform would be maintained.

Atmospheric Emission Effects

Emissions associated with vessel activity during decommissioning activities.

All vessels will comply with MARPOL 73/78 Annex VI on air pollution; plant will comply with relevant air pollution regulations (The Offshore Combustion Installations (Prevention and Control of Pollution) (Amendment) Regulations 2007.

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