Wheatstone Project Oil Spill Environmental Response Plan

8/18/2019 Wheatstone Project Oil Spill Environmental Response Plan

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Please note that prior to being published, some information in the approved Oil SpillEnvironmental Response Plan has been redacted, as approved by the Minister on27/11/2013, on the basis that it is company confidential.

© Chevron Australia Pty Ltd

Document No: WS0-0000-HES-PLN-CVX-000-00092-000 Revision: 1

Revision Date: 30 October 2013

IP Security: Public

Wheatstone ProjectWheatstone Oil Spill EnvironmentalResponse Plan


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Wheatstone Project Document No: WS0-0000-HES-PLN-CVX-000-00092-000

Wheatstone Oil Spill Environmental Response Plan Revision: 1

Revision Date: 30/10/2013

© Chevron Australia Pty Ltd Public Page 2

Printed Date: 28/11/2013 Uncontrolled when printed

TABLE OF CONTENTS

ACRONYMS, ABBREVIATIONS AND TERMINOLOGY ....................................................... 6

1.0 BACKGROUND ............................................................................................................ 9

1.1 Project Overview .................................................................................................. 9

1.2 Proponent ............................................................................................................ 9 1.3 Scope and Objectives .......................................................................................... 9

1.4 Environmental Approvals ................................................................................... 12

1.5 Public Availability ............................................................................................... 12

1.6 Review, Approval and Revision of this Plan ....................................................... 12

2.0 PROJECT DESCRIPTION .......................................................................................... 14

2.1 Onshore Footprint .............................................................................................. 14 2.1.1 LNG Plant ............................................................................................. 14 2.1.2 Domgas Plant ....................................................................................... 14

2.2 Offshore and Nearshore ..................................................................................... 14 2.2.1 Shipping Channel ................................................................................. 14 2.2.2 Materials Offloading Facility .................................................................. 15 2.2.3 Product Loading Facility ....................................................................... 15 2.2.4 Dredging and Dredge Spoil Disposal .................................................... 15 2.2.5 Platform ................................................................................................ 15 2.2.6 Subsea System .................................................................................... 16 2.2.7 Trunkline and Shore Crossing .............................................................. 16 2.2.8 Discharge Lines .................................................................................... 16 2.2.9 Construction Vessels ............................................................................ 17

3.0 HYDROCARBON SPILL SCENARIOS....................................................................... 18

3.1 Overview ............................................................................................................ 18

3.2 Spill Modelling .................................................................................................... 18 3.2.1 Rationale .............................................................................................. 18 3.2.2 Methodologies ...................................................................................... 19 3.2.3 Results ................................................................................................. 20

3.3 Zone of Potential Influence ................................................................................. 22

4.0 POTENTIAL HYDROCARBON EFFECTS ON ENVIRONMENTAL RECEPTORS .... 25

4.1 Impact Factors ................................................................................................... 25 4.1.1 Sensitivity ............................................................................................. 25 4.1.2 Toxicity ................................................................................................. 25 4.1.3 Cumulative Effects................................................................................ 26

4.2 Ecological Effects ............................................................................................... 26 4.2.1 Habitat Effects ...................................................................................... 26 4.2.2 Fauna Effects ....................................................................................... 33

5.0 RESOURCES AT RISK .............................................................................................. 41

5.1 Overview ............................................................................................................ 41

5.2 Identified Sensitive Receptors ............................................................................ 41 5.2.1 Matters and species of NES ................................................................. 41 5.2.2 Provincial Bioregion Ecosystem............................................................ 48 5.2.3 Oil Spill Response Atlas ....................................................................... 52

5.3 Resource Protection Prioritisation ...................................................................... 65

5.4 Net Environment Benefit Analysis ...................................................................... 66

6.0 ENVIRONMENTAL RESPONSE STRATEGIES ......................................................... 68

6.1 Overview ............................................................................................................ 68 6.2 Source Control ................................................................................................... 71


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6.2.1 Single Point, Transfer Equipment and Ruptured Vessel Control ........... 71 6.2.2 Well Capping (Stack) ............................................................................ 71 6.2.3 Well Intervention ................................................................................... 72

6.3 Monitoring and Evaluation .................................................................................. 73 6.3.1 Aerial Surveillance ................................................................................ 73 6.3.2 Vessel Surveillance .............................................................................. 74

6.3.3 Surface Plume Tracking ....................................................................... 74 6.3.4 Satellite Surveillance ............................................................................ 74 6.3.5 Spill Trajectory Modelling...................................................................... 75

6.4 Containment and Recovery ................................................................................ 75 6.4.1 Boom Selection and Deployment .......................................................... 76 6.4.2 Skimmer Selection and Deployment ..................................................... 78

6.5 Assisted Natural Dispersion ............................................................................... 79

6.6 Chemical Dispersant Application ........................................................................ 80 6.6.1 Surface Application............................................................................... 82 6.6.2 Sub-surface Application ........................................................................ 82

6.7 Fauna Protection Measures ............................................................................... 84

6.7.1 Exclusion, Hazing and Deterrents ......................................................... 84 6.7.2 Pre-emptive Capture and Removal ....................................................... 84

6.8 Oiled Fauna Response ...................................................................................... 84 6.8.1 Capture, Collection and Holding of Oiled Fauna ................................... 85 6.8.2 Fauna Rehabilitation ............................................................................. 86 6.8.3 Carcass Disposal ................................................................................. 87

6.9 Shoreline Protection and Deflection ................................................................... 87 6.9.1 Shoreline Protection ............................................................................. 87 6.9.2 Shoreline Deflection .............................................................................87

6.10 Shoreline Clean-up ............................................................................................ 88 6.10.1 Natural Recovery .................................................................................. 91

6.10.2 Absorbents ........................................................................................... 91 6.10.3 Sediment Relocation ............................................................................ 91 6.10.4 Manual Clean-up .................................................................................. 92 6.10.5 Mechanical Clean-up ............................................................................ 92 6.10.6 Pumps and Vacuums ........................................................................... 92 6.10.7 Low-pressure Flushing ......................................................................... 93 6.10.8 High-pressure Flushing ........................................................................ 93 6.10.9 Flooding/Deluging ................................................................................ 94

6.11 Waste Management ........................................................................................... 94

7.0 IMPLEMENTATION STRATEGY ................................................................................ 96

7.1 Overview ............................................................................................................ 96

7.2 Emergency Management Structure .................................................................... 96 7.3 Tiered Spill Response Approach ........................................................................ 97

7.4 Division of Responsibility .................................................................................... 98

7.5 Response Arrangements .................................................................................... 99 7.5.1 Initiation ................................................................................................ 99 7.5.2 Response Actions, Support and Escalation .......................................... 99 7.5.3 Termination ........................................................................................ 100

8.0 SPILL RESPONSE CAPABILITIES .......................................................................... 101

8.1 Minimum Training and Competency Levels ...................................................... 101

8.2 Current Manning Capacity ................................................................................ 102

8.3 Equipment and Materials .................................................................................. 103

8.4 Chemical Dispersants ...................................................................................... 103

8.5 Waste Facilities ................................................................................................ 105


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8.6 Response Timing ............................................................................................. 106

8.7 Simulated Response Testing ........................................................................... 106

8.8 Insurances ....................................................................................................... 108

9.0 REPORTING ............................................................................................................. 110

9.1 Annual Compliance Reporting .......................................................................... 110

9.2 Non-compliance Reporting ............................................................................... 110 9.3 Other Reporting ............................................................................................... 110

10.0 REFERENCES.......................................................................................................... 111

TABLES

Table 1.1: Requirements of Commonwealth Ministerial Conditions: EPBC 2008/4469

relevant to this Plan ......................................................................................... 13 Table 3.1: Worst-case Hydrocarbon Spill Scenarios ............................................................. 19

Table 3.2: Dissolved Aromatic In-water Threshold Values Applied as Part of the ModellingStudy ............................................................................................................... 23

Table 3.3: In-water (entrained) Threshold Values Applied as part of the Modelling Study..... 23

Table 5.1: Sensitive Resources and Key Receptors within and adjacent to the combinedZPI ................................................................................................................... 42

Table 5.2: Description of Provincial Bioregions within and adjacent to the combined ZPI ..... 49

Table 5.3: Protection Priority Ranking .................................................................................. 65

Table 6.1: Overview of Spill Response Strategies to be employed in first 24 hours .............. 69

Table 6.2: Overview of Spill Response Strategies to be employed after first 24 hours .......... 70

Table 6.3: Boom Selection Matrix ......................................................................................... 77 Table 6.4: Skimmer Selection Matrix .................................................................................... 79

Table 6.5: Recommended Clean-up Methods ...................................................................... 89

Table 7.1: Chevron Emergency Response Organisation ...................................................... 96

Table 7.2: Hydrocarbon Spill Tiers ....................................................................................... 97

Table 7.3: Emergency Response Team and Tier Level ........................................................ 98

Table 8.1: Current Manning Capabilities (as at August 2013) ............................................. 102

Table 8.2: Dispersant Resource Capability ......................................................................... 104

Table 8.3: Third Party Waste Facilities and Capacities to Receive Oily Wastes ................. 105

Table 8.4: Emergency Response Arrangement Testing ..................................................... 106

Table 8.5: Exercise Categories .......................................................................................... 107

Table 8.6: Response Times to and from various locations within the Chevron Operational Area ............................................................................................................... 109

FIGURES

Figure 1.1: Location of Wheatstone Project Infrastructure .................................................... 10

Figure 1.2: Nearshore Project Infrastructure ......................................................................... 11

Figure 3.1: Minimum Time for Potential Shoreline Exposure (Scenario 4) ............................ 21

Figure 3.2: Zone of Potential Influence developed from combined modelling outputsScenarios 1-4................................................................................................... 24

Figure 4.1: Oil Spill related Threats to Sea Turtles ............................................................... 37


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Figure 4.2: Impact Pathways ................................................................................................ 38

Figure 5.1: State and Commonwealth Marine Reserves and Project Marine Facilities ......... 46

Figure 5.2: Key Ecological Features ..................................................................................... 47

Figure 5.3: Provincial Bioregions within and adjacent to the ZPI........................................... 51

Figure 5.4: Overview over the Oil Spill Response Atlas Figures ........................................... 53

Figure 5.5: Oil Spill Response Atlas – Montebello Islands .................................................... 54

Figure 5.6: Oil Spill Response Atlas – Barrow Island ............................................................ 55

Figure 5.7: Oil Spill Response Atlas – South Barrow Island .................................................. 56

Figure 5.8: Oil Spill Response Atlas – Airlie Island ............................................................... 57

Figure 5.9: Oil Spill Response Atlas – Thevenard Island ...................................................... 58

Figure 5.10: Oil Spill Response Atlas – Peak to Bessieres Islands ....................................... 59

Figure 5.11: Oil Spill Response Atlas – Muiron Islands ........................................................ 60

Figure 5.12: Oil Spill Response Atlas – North West Cape .................................................... 61

Figure 5.13: Oil Spill Response Atlas – Turquoise Bay to Torpedo Bay ................................ 62

Figure 5.14: Oil Spill Response Atlas – Sandy Point to Turquoise Bay ................................. 63

Figure 5.15: Oil Spill Response Atlas – Beacon Point to Sandy Point .................................. 64

Figure 5.16: NEBA Process for Selecting Protection Priorities and Response Strategies ..... 67 Figure 6.1: Decision Guidelines for use of Dispersants on the Sea Surface ......................... 83

Figure 7.1: Tier 1 Spill Response Plans Initiation ................................................................. 99

APPENDICES

APPENDIX A ENVIRONMENTAL RECEPTORS AND PROTECTION PRIORITY ... 120

APPENDIX B INCIDENT ACTION PLANS ............................................................... 124

APPENDIX C TRAINING AND COMPETENCY MATRIX ......................................... 136 APPENDIX D SPILL RESPONSE EQUIPMENT AND MATERIALS ........................ 143

APPENDIX E ACTION TABLE ................................................................................. 149


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ACRONYMS, ABBREVIATIONS AND TERMINOLOGY

ABU Australasia Business Unit

AEMT Asset Emergency Management Team

AMOSC Australian Marine Oil Spills Centre

AMSA Australian Maritime Safety Authority

ANSIA Ashburton North Strategic Industrial Area

APASA Asia Pacific Applied Science Associates

APPEA Australian Petroleum Production and Exploration Association

bbl Barrel(s)

BOP Blow-out Preventers

BHD Backhoe Dredge

BPPH Benthic Primary Producer Habitat

Chevron Chevron Australia Pty Ltd

CMT Crisis Management Team

Construction

Phase

For the purposes of this plan, the Construction Phase will encompass any

proposal-related construction activities within the terrestrial and marine

disturbance footprints, excluding commissioning activities and investigatory

works such as, but not limited to, geotechnical, geophysical, biological and

cultural heritage surveys, baseline monitoring surveys and technology trials.

CSD Cutter suction dredge

Cth Commonwealth

DBNGP Dampier-to-Bunbury Natural Gas Pipeline

DMP Department of Minerals and Petroleum (WA)

Domgas Domestic gas

DoT Department of Transport (WA)

DOTE Department Of The Environment (Cth) – formerly Department of Sustainability,

Environment, Water, Population and Communities (SEWPaC)

DPA Dampier Port Authority (WA)

DPaW Department of Wildlife and Parks (WA) - formerly Department of Environment

and Conservation (WA)

Draft EIS/ERMP The Environmental Impact Statement/Environmental Review and Management

Programme

EMP Environment Management Plan

eNGO Environmental Non-Government Organisation

EP Act (WA) Environmental Protection Act 1986

EPBC Environment Protection and Biodiversity Conservation

EPBC Act (Cth) Environmental Protection and Biodiversity Conservation Act 1999

EPBC 2008/4469 The Commonwealth Primary Environmental Approval and conditional

requirements for the Wheatstone Project. Commonwealth Government of Australia, Minister for Sustainability, Environment, Water, Populations and

Communities, Hon. Tony Burke, 22 September 2011, as amended from time to


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time.

ERO Emergency Response Organisations

ESI Environmental Sensitive Index

ft Feet

ha hectare(s)

HES Health, Environment and Safety

HFO Heavy Fuel Oil

HMA Hazard Management Agency

HR Human Resources

IBC Intermediate Bulk Container

IC Incident Commander

ICS Incident Command System

IEMT Installation Emergency Management Team

km Kilometre(s)

kn Knot(s)

kPa Kilopascal(s)

L Litre(s)

LAT LAT means lowest astronomical tide

LNG Liquefied Natural Gas

m Metre(s)

mAHD Metres above Australian Height Datum (approximately the height above meansea level)

MARPOL International Convention for the Prevention of Pollution from Ships

MDO Marine Diesel Oil

MOF Materials Offloading Facility

MSCF Thousands of Standard Cubic Feet

MTPA Million tonnes per annum

Nearshore Marine habitat from the 20 m contour to the shoreline

NEBA Net Environmental Benefit Analysis

NES National Environmental Significance

NOAA National Oceanic and Atmospheric Administration.

NOPSEMA National Offshore Petroleum Safety and Environmental Management Authority

OE Operational Excellence

Offshore Marine habitat beyond the 20 m contour to the shoreline

OIM Offshore Installation Manager

OPGGSA Offshore Petroleum and Greenhouse Gas Storage Act

ORT Onsite Response Team

OSA Oiled Shoreline Assessment


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OSCAR Online System for Comprehensive Activity Reporting

OSERP Oil Spill Environmental Response Plan

OSRL Oil Spill Response Limited

OSRO Oil Spill Response Organisation

PIC Person In Charge

PIN Pilbara Inshore bioregion

PIO Pilbara Offshore bioregion

(The) Plan The Wheatstone Oil Spill Environmental Response Plan

PLF Product Loading Facility

ppb Parts Per Billion

PPE Personal Protective Equipment

ppm Parts Per Million

Project Nearshore and offshore marine facilities, trunkline, and Onshore Facility

Practicable Means reasonably practicable having regard to, among other things, local

conditions and circumstances (including costs) and to the current state of

technical knowledge (taken from the EP Act)

Proponent Chevron Australia Pty Ltd

RORO Roll-on, Roll-off

SERT Site Emergency Response Team

SIA Strategic Industrial Area

SIC Shared Infrastructure Corridor

SOPEP Shipboard Oil Pollution Emergency Plan

SPOC Single Point of Contact

SWRP Subsea Well Response Project

T Tonnes

TPH Tonnes Per Hour

TSHD Trailing suction hopper dredge

TVI Thevenard Island

WA Western Australia

ZPI Zone of Potential Influence


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1.0 BACKGROUND

1.1 Project Overview

Chevron Australia Pty Ltd (Chevron) will construct and operate a multi-train Liquefied NaturalGas (LNG) and domestic gas (Domgas) plant near Onslow on the Pilbara Coast, Western

Australia. The Wheatstone Project (the Project) will process gas from various fields locatedoffshore in the West Carnarvon Basin. Ashburton North Strategic Industrial Area (ANSIA) isthe approved site for the LNG and Domgas plants.

The Project requires installation of gas gathering, export and processing facilities inCommonwealth and State waters and on land. The initial Project will produce gas fromProduction Licences WA-46-L, WA-47-L, WA-48-L and WA-49-L, located 145 km offshorefrom the mainland, approximately 100 km north of Barrow Island and 225 km north of Onslow,and will also process gas to be produced from other offshore production licences locatednearby operated by Apache Corporation. Figure 1.1 shows the location of the WheatstoneProject.

The ANSIA site is located approximately 12 km south-west of Onslow along the Pilbara coastwithin the Shire of Ashburton. The initial Project will consist of two LNG processing trains,each with a capacity of approximately 5 million tonnes per annum (MTPA). Environmentalapproval was granted for a 25 MTPA plant to allow for the expected further expansions. TheDomgas plant will be a separate but co-located facility and will form part of the Project.Development of the Domgas plant also covers onshore pipeline installation by DBPDevelopment Group under a pipeline contract to build, own and operate the pipeline totransport gas to the existing Dampier-to-Bunbury Natural Gas Pipeline (DBNGP)infrastructure. Figure 1.2 shows the onshore and nearshore project footprint.

1.2 Proponent

Chevron Australia is the proponent and the company taking the action for the Project onbehalf of its joint venture participants Apache Corporation, Tokyo Electric Power Company(TEPCO), Kuwait Foreign Petroleum Exploration Company (KUFPEC), Shell and KyushuElectric Power Company (Kyushu).

1.3 Scope and Objectives

The Plan has been prepared with the objective of demonstrating Chevron’s preparedness forand response to, any hydrocarbon spills, including from offshore wells and infrastructure,pipelines, the onshore facility, construction vessels and operation vessels associated with theWheatstone Project, including the capacity to respond to a spill and mitigate the environmentalimpacts on the Commonwealth marine area and habitat of Environment Protection and

Biodiversity Conservation (EPBC) listed species.

This Plan provides a high level framework for a response to a hydrocarbon spill and details theprocesses and strategies which may be considered, where relevant and practicable. Thedetailed response and implementation of strategies are covered in individual Oil SpillOperational Response Plans or similar documents.

The scope of this Plan is limited to Commonwealth marine area and habitats of listed species,with priority given to identified sensitive areas and habitats and the construction phase of theproject. The Operation Phase of the Wheatstone Project is not included within the scope ofthis Plan. The spill scenarios related to the Operations Phase of the Project will be dealt within an update to this Plan, or a separate Plan. The staged approval of this Plan does not in any

way affect the environmental risks, management or performance of Chevron’s hydrocarbonspill response preparedness and capacity detailed within this Plan.


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Figure 1.1: Location of Wheatstone Project Infrastructure


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Figure 1.2: Nearshore Project Infrastruc ture


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1.4 Environmental Approvals

The Wheatstone Project was assessed through an Environmental Impact Statement under theCommonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act).The Commonwealth Minister for Sustainability, Environment, Water, Population andCommunities approved the Wheatstone Project on 22 September 2011 (EPBC 2008/4469)

with a variation to EPBC 2008/4469 Conditions 44, 45, 55, 56 and 66 made pursuant tosection 143 of the EPBC Act. Other amendments may be made from time to time and if so willbe reflected in the next revision of this Plan. This Plan has been prepared to meet therequirements of EPBC 2008/4469 Condition 47 (Table 1.1).

1.5 Public Availabili ty

EPBC 2008/4469 Condition 2 requires that Chevron retains information relevant to theimplementation of the Wheatstone Project. In the event that this Plan, or parts of this Plan, isrequired to be implemented, the final reports from the implemented Plan will be madeavailable to DOTE and the public. EPBC 2008/4469 Condition 8 requires Chevron to publishthis Program on its website within one month of being approved, unless otherwise agreed to inwriting by the Minister.

1.6 Review, Approval and Revision of this Plan

Chevron is committed to conducting activities in an environmentally responsible manner andaims to implement reviews of its environmental management actions as part of a program ofcontinuous improvement. This commitment to continuous improvement means that theProponent will review the Plan to address matters such as the overall effectiveness,environmental performance, changes in environmental risks and changes in businessconditions on an as needed basis (e.g. in response to new information).

EPBC 2008/4469 Conditions 5 and 6 requires that Chevron may only implement theWheatstone Project otherwise than in accordance with the provisions of this Plan which

regulate the matters of national environmental significance (NES) relevant to this Plan fromthe date of approval of any variation to this Plan by the Commonwealth Minister. Amendmentsto activities and management may be made without an amendment to the Plan where thoseamendments do not increase the risk level, and where the regulator is notified of thoseamendments before being implemented.


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Table 1.1: Requirements of Commonwealth Ministerial Conditions: EPBC 2008/4469relevant to this Plan

No. Condition Section

47 The person taking the action must develop and submit to the Minister forapproval, an Oil Spill Environmental Response Plan (OSERP) that

demonstrates the response preparedness of the person taking the action for

any hydrocarbon spills, including from offshore wells and infrastructure,

pipelines, the onshore facility, construction vessels and operation vessels.

This must include the capacity to response to a spill and mitigate the

environmental impacts on the Commonwealth marine area and habitat of

EPBC listed species. The OSERP must include, but is not limited to:

This Plan

47a Identification of sensitive areas or habitats that may be impacted by apotential spill, as determined by site-specific modelling of worst casescenario spills, including an eleven week uncontrolled release.

5.2

47b Specific response measures for those sensitive areas or habitats andprioritisation of those areas during a hydrocarbon spill response.

5.3

6.0

47c A description of resources available for use in containing andminimising impacts in the event of a spill and arrangements foraccessing them.

8.0

47d A demonstrated capacity to respond to a spill at the site and measuresthat can feasibly be applied within the first 48 hours of a spill occurring.

7.0

8.0

47e Details of the insurance arrangements that have been made in respect

of paying the costs associated with operational and scientificmonitoring, as outlined in the Oil Spill Operational and ScientificMonitoring Program required under condition 50 and repairingenvironmental damage arising from potential hydrocarbon spills, asdetermined necessary from the results of the Operational and ScientificMonitoring Program.

8.8

47f Training of staff in spill response measures and identifying roles andresponsibilities of personnel during a spill response.

8.1;

Appendix C

47g Procedures for reporting oil spill incidents to the department. 9.0


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2.0 PROJECT DESCRIPTION

The description of key characteristics which follows has been included for the purpose ofcontextualising the management and monitoring measures which are required under this Plan.Project characteristics may be amended from time to time, for example under section 45C ofthe EP Act. The key Project characteristics which are detailed in this Plan should therefore beread as subject to any project amendments which are made from time to time.

2.1 Onshore Footprint

The onshore Project Footprint totals approximately 3300 ha. The Project comprises the initialconstruction of a LNG processing facility, Shared Infrastructure Corridor (SIC) andaccommodation village. The LNG processing facility covers an area approximately 1010 haand will be constructed on a raised pad. The accommodation village pad and SIC covers anarea approximately 1000 ha and will be designed predominantly above a 1:100 year floodevent.

Infrastructure will be designed to retain natural drainage through engineering and design

solutions such as culverts, sedimentation ponds, a silt fence around the construction area andplacement of rock at surface water release points to reduce erosion. Roads and fill sourcescover an area approximately 980 ha. Access roads will be sealed. Part of the AccommodationVillage Construction Road has been altered to align with the current pastoral tracks. TheDomgas pipeline covers an area of approximately 320 ha.

2.1.1 LNG Plant

The LNG Plant located in Ashburton North Strategic Industrial Area (ANSIA) will initiallycomprise of two LNG trains operating at a capacity of approximately 9 MTPA, expanding to itsmaximum capacity of 25 MTPA with up to six LNG trains in operation. LNG will be initiallystored in two 180 000 m3 LNG tanks, expanding up to four 180 000 m3 tanks. For export, the

LNG is pumped from the storage tanks to the loading arms at the LNG carrier berths and intoLNG carriers for delivery to foreign or domestic markets.

Condensate will also be stored in tanks of approximately 120 000 m3 and pumped to thecondensate berth to transfer to tankers via the loading arms. Initially, two tanks are proposedwith additional tanks being added as throughput increases over time, up to a maximum of fourcondensate storage tanks. The LNG plant will operate with up to eight elevated flarestructures; three high pressure flares with approximate height of 125 m, three low pressureflares with approximate height of 45 m and two marine flares with approximate height of 45 m.

2.1.2 Domgas Plant

Initially one domgas plant is proposed for the two-train Foundation Project. Up to four domgasplants may be required when the Project reaches capacity. The domgas plant will operate at acapacity of approximately 15% heating value of LNG produced. The domgas pipeline willconnect to the existing DBNGP via an onshore pipeline which is to be built, owned andoperated by DBP Development Group under a pipeline contract to Chevron.

2.2 Offshore and Nearshore

2.2.1 Shipping Channel

The shipping channel extends up to 18 km across the inner continental shelf, passing SaladinShoal, Hastings Shoal, Gorgon Patch and Weeks Shoal. The channel will allow LNG andcondensate tankers access to the Product Loading Facility (PLF). A navigation channel and a

turning basin will enable the LNG and condensate carriers to safely access and depart the


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berths at the PLF. The channels and basin may need to be dredged periodically to maintainthe required depth.

2.2.2 Materials Offloading Facil ity

The Materials Offloading Facility (MOF) provides an offloading facility for heavy-lift ships, Roll-

on, Roll-off (RORO) vessels, heavy-lift carriers and barges delivering pre-fabricated modules,equipment and bulk material (steel fabricated pipe, piles and other construction bulk materials)and vessel access for marine contractors during construction. Pilot boat and tug movementsassociated with the arrival and departure of the LNG and condensate carriers are berthed atthe MOF. The MOF provides a base for marine operations craft such as tugs, security and linehandling vessels. Breakwater(s) at the MOF entrance, extending from the shoreline, create asafe operating environment inside the basin during normal conditions and during a cyclone.

An access channel and turning basin provides access to the main navigation channel.

2.2.3 Product Loading Facility

The PLF at up to 2.5 km in length provides export facilities for up to three LNG tankers, or upto two LNG tankers and one condensate tanker. It includes a jetty and mooring dolphins. The

PLF has the potential to carry wastewater discharge pipe(s). There may be up to two wastewater discharge lines from the onshore facilities to the PLF or within the area designated asModerate level of Environmental Protection. The PLF is likely to carry a roadway and a doublepipe rack from the shore to the PLF operations platform from where loading operations will becontrolled. The pipe rack will accommodate LNG and condensate loading lines, an LNGvapour return line, fire water pipework and communications cabling.

2.2.4 Dredging and Dredge Spoil Disposal

Initial dredging will take place to create the temporary access channel which will become partof the MOF and approach channel. The channels and basin may need to be dredgedperiodically to maintain the required depth. In total, the dredging of the shipping channel,

turning basin, tanker berths and MOF will create up to approximately 45 Mm3

of dredge spoiland up to approximately 3 Mm3 dredge spoil for the trunkline. The dredge spoil will bedisposed at up to five designated sites- three near-shore and two offshore (see Figure 1.2).The bulk of the material will be placed at spoil ground C with smaller volumes potentially beingplaced at sites A, B, D and E.

2.2.5 Platform

The Wheatstone Platform will be a manned facility 145 km offshore located in the WestCarnarvon Basin in approximately 70 m water depth (LAT). The Platform provides the initialtreatment of gas and natural gas condensate to be transported via trunkline to the onshoreLNG processing facility.

The platform comprises a steel gravity based structure. Located on the Platform facility are:

♦ Separation trains that separate the gas and liquids from the well fluids for processing

♦ Gas compressors, including associated coolers

♦ Gas dehydration trains

♦ Condensate dewatering trains

♦ PW treatment and overboard disposal

♦ Mono Ethylene Glycol (MEG) storage, and regeneration

♦ Living Quarters

♦ Associated utilities such as the seawater cooling system, chemical storage, firewater,power generation and drainage systems.


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2.2.6 Subsea System

The Project will utilise an all subsea concept for wells and manifolds with currently up to 35subsea production wells drilled during the life of the Project.

Each well will be fitted with an arrangement of valves, controls and instrumentation referred toas a “christmas tree” located on the seafloor. Safety valves are proposed to be installed ineach well to enable isolation of the gas reservoir that will close automatically in the event of amechanical failure or loss of system integrity. A “choke” valve will also be included to controlthe fluid flow and pressure from the well to the flowline.

Each group of wells will use “well jumpers” to connect them to their “cluster manifolds”. Eachcluster manifold will serve between one and eight wells. From these cluster manifolds, tie-inspools will transfer fluids to the feed gas flowline(s). Production fluids will be transported alongthe feed gas flowline(s) to the Platform.

An umbilical bundle connected to the platform will support the operation of the wells andmanifolds. These umbilicals will comprise of electrical power and signal lines, control lines andchemical injection lines.

2.2.7 Trunkline and Shore Crossing

The trunkline transports treated gas and condensate subsea from the offshore facilities to theonshore processing facilities. It consists of one pipeline extending approximately 225 km fromthe Wheatstone platform (see Figure 1.1 for location of the Wheatstone platform) to the shorecrossing (see Figure 1.2 for shore crossing location). Nearshore the trunkline may bestabilised, to prevent movement. This is done by the use of trenching and engineered backfillin order to minimise impact on shipping, stabilise the pipeline under cyclonic conditions andprotect the pipeline from hazards.

Micro-tunnelling allows the trunkline to cross the shore and connect to the onshore plantfacility with the least impact on coastal processes and mangrove habitat. A tunnel diameter ofapproximately 2 m will be created close to the onshore plant location and will exitapproximately 1 km from the shoreline at 2 m water depth. The trunkline is pulled through thetunnel underneath the beach.

2.2.8 Discharge Lines

There may be up to two waste water discharge lines from the onshore facilities to the PLF orwithin the area designated as Moderate level of Environmental Protection. During operationswaste water including reverse osmosis (RO) brines and filter backwash water, stormwater

contaminated with hydrocarbons, clean stormwater and hydrostatic test water will be treatedat an onshore treatment facility prior to being discharged to the sea via the outfall pipeline.There will be one Produced Water (PW) pipeline up to 50 km long that will discharge offshoreat 20 m depth contour.


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2.2.9 Construction Vessels

There are a number of vessels associated with the dredging, trenching, pipelay, and backfill,materials transport and offshore installation activities. These may include:

♦ Trailing Suction Hopper Dredges (TSHDs)

♦ Cutter Suction Dredges (CSDs)♦ Backhoe Dredges (BHDs)

♦ Hopper barges

♦ Fourth generation pipelay vessel (dynamic positioning)

♦ Second generation pipelay barge

♦ Side stone dumping vessel or Fall pipe vessel

♦ Heavy-lift and Roll-on/Roll-off vessels

♦ A range of ancillary equipment including support tugs, crane and work barges/pontoons,multicats and or supply vessels and various support launches.


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3.0 HYDROCARBON SPILL SCENARIOS

3.1 Overview

Construction activities for the Wheatstone Project are divided into three distinct constructionscopes as listed below:

1. Drilling and Completions

a. Production Drilling and Well Site Completions.

2. Upstream:

a. Trunkline and flowlines installation

b. Secondary stabilisation of the trunkline

c. Dewatering and drying of the trunkline

d. Microtunnel activities

e. Jacket and topsides installation.

3. Downstream:

a. Dredging of the shipping channel, PLF and MOF

b. PLF Construction

c. MOF Construction

d. Module delivery

e. Onshore Construction.

As it is not feasible for spill modelling to be undertaken for every possible spill scenarioassociated with the project, and as modelling can only provide a prediction of thehydrocarbon’s fate, the scenarios chosen to be modelled was selected to provide an indicationof the scale of impact and types of receptors that may be affected should a spill occur. Thisapproach is taken as a means to demonstrate Chevron’s ability to deal with any spill at anylocation within the permit areas or otherwise associated with construction activities.

To determine the worst case spill modelling scenarios the scope of works for each workactivity were reviewed and a spill scenario which reflected the most likely impact toCommonwealth marine waters, Matters of NES or habitat of EPBC listed species wereselected. An overview of the four scenarios that were selected from this process is detailed inthe Section 3.2.

3.2 Spill Modelling

3.2.1 Rationale

A worst case credible spill scenario is defined for the purpose of this Plan as a hydrocarbonspill scenario with the potential to cause the most significant environmental impacts to habitatsof EPBC listed species or Matters of NES in order to identify specific sensitive areas orhabitats. Modelled Spill scenarios include:

♦ Scenario 1: Diesel fuel spill within the MOF, was selected as it represented a greatestpossible Standard Diesel spill close to shore and with the potential to impact onMangroves and other sensitive intertidal receptors.

♦ Scenario 2: Marine Diesel Oil (MDO) spill at a location in Western Australia (WA) State

waters approximately 10 km off the coast, represents the greatest potential loss of MDOwhich might occur during bunkering of the dredging fleet in the nearshore zone and at a


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location with the greatest risk of impact to nearshore habitats such as coral reefs andoffshore islands.

♦ Scenario 3: Heavy Fuel Oil (HFO) spill at the boundary of Commonwealth/State watersrepresents the largest potential loss of HFO and is associated with bunkering the offshorepipelay vessel.

♦ Scenario 4: 11 week uncontrolled well blow-out at the IAG-1E production was selected asit has the highest identified hydrocarbon flow rate, is located in relatively shallower water islocated relatively closer to sensitive shorelines and therefore has the potential to cause thegreatest shoreline impacts in comparison to the other Wheatstone production wells.

The four scenarios identified as the worst case potential spills for the Wheatstone projectduring construction were chosen due to the type and volume of hydrocarbon that couldpotentially be released and the proximity to potentially sensitive areas or habitats. Details ofthe hydrocarbon spill scenarios are provided in Table 3.1.

Table 3.1: Worst-case Hydrocarbon Spill Scenarios

Scenario Location Type Spill Event Volume/ rate

1 Materials Offloading

Facility

Standard Diesel

Fuel

Instantaneous

release

2.55 m3

2 WA state waters

(10 km from shore)

Marine Diesel Oil Surface release over

6 hours

265.5 m3

3 WA state /

Commonwealth

waters boundary

Heavy Fuel Oil Surface release over

6 hours

850 m3

4 Iago Production Well:

IAG -1E

Gas Condensate

(condensate gas

ratio = 24.1

bbl/MSCF)

11 week well blow-

out

26 300 (bbl/day)

3.2.2 Methodologies

Standard but separate modelling techniques were used for the selected spill scenariossubject to the hydrocarbon type, volume released and location of the spill in question. Themethodologies used are briefly described below.

Scenario 1: Standard Diesel Spill at the MOF was modelled as part of the EnvironmentalImpact Statement/Environmental Review and Management Program and the results havebeen used to inform this Plan. Modelling was completed using the MIKE 21/3 SA model (DHI2009) which describes the spreading and weather of hydrocarbon spill in an aquaticenvironment under the influence of local hydrodynamic properties. The model providesinformation on spill location and trajectory, hydrocarbon thickness on the sea surface, and theevolution of the spill hydrocarbon’s physiochemical properties. Model results are presented as

a series of probability maps which show the likelihood of the spill trajectory combined with thelikelihood of the potential impact on a specific receptor. The outputs from the model includelikely maximum hydrocarbon surface thickness (mm), minimum time of arrival at the receptor


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location (hours) and the probability (percentage) of hydrocarbon of 0.001 mm (~1 g/m 2) ormore reaching any given area.

Scenarios 2, 3 and 4: Probabilistic modelling of sea surface and shoreline exposure wasconducted using a three-dimensional trajectory and fates model; SIMAP. The SIMAP model isable to track hydrocarbons at very low concentrations/thickness; however, biological relevant

modelling thresholds were determined for the three scenarios modelled on the basis of adetailed literature review (APASA 2013), see Section 3.3.

3.2.3 Results

3.2.3.1 Scenario 1 - Diesel Spill at the MOF

The model was run for multiple simulations for each season over three years with the resultsindicating that a diesel spill at the MOF poses a risk, if uncontained, to nearshore habitatsalong the coastline extending from Coolgra Point to the Ashburton Delta.

3.2.3.2 Scenario 2 - Nearshore MDO Spil l

Simulations were run during all seasonal conditions. The minimum time for the firsthydrocarbon to contact was one hour at the Southern Group of Islands1. The Southern Groupalso recorded the greatest probability of shoreline contact during all seasons. The highestprobability of contact was determined for a spill occurring during the winter.

3.2.3.3 Scenario 3 - Offshore HFO Spill

Simulations were run during all seasonal conditions. The minimum time for the firsthydrocarbon to contact the shorelines was seven hours at the Southern Group of Islands. TheSouthern Group also had the greatest probability of shoreline contact during all seasons.

3.2.3.4 Scenario 4 - Well Blow-out

Simulations run during all seasons identified:

♦ No shoreline exposure during winter season

♦ During the summer season, there is a 16% probability of shoreline contact occurring atboth Barrow Island and the Montebello islands. During the transitional season there is a14% probability of shoreline contact at the Montebello islands

♦ The predicted minimum time before hydrocarbon exposure of any shoreline was 358 hours(~15 days) under any conditions

♦ Zones of high or moderate exposure to dissolved hydrocarbon (aromatics) in the upperwater column (top 10 m) are not predicted to occur within waters adjacent to sensitive

coastal environmental receptors including islands and the Ningaloo Coast♦ Zones of moderate exposure to entrained hydrocarbon are predicted to occur in coastal

waters adjacent to the Montebello Islands, Barrow Island, Ningaloo Coast, SouthernGroup of Islands and Muiron Islands under all seasonal conditions.

Where the spill models predicted hydrocarbons had the potential to wash ashore,accumulation models were then used (Shoreline near shore intertidal exposure) to determinewhich shorelines had the potential to be affected. Based upon the credible worst casescenario Figure 3.1, depicts the minimum time for shoreline exposure associated with theshorelines predicted to have the potential of accumulations greater than 100 g/m2.

1 The Southern group comprises Thevenard Island, Bessier Island, Serrurier Island, Airlie Island and the Rivoli Islands


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Figure 3.1: Minimum Time for Potential Shoreline Exposure (Scenario 4)Note: Timing for spill contact with receptors for other relevant scenarios (Scenario 2 and 3) areexpected to occur within 48hrs though over a much smaller area than Scenario 4 shown above.


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3.3 Zone of Potential Influence

The hydrocarbon spill modelling assessed the probability of hydrocarbon contact with the seasurface, subsurface and shorelines at a given set of thresholds which were selected based onpublished scientific data. This information was subsequently used to determine the Zone ofPotential Influence (ZPI). A probability of hydrocarbon exposure to the environment of greater

than 10% has been selected for the purposes of determining the extent of the ZPI for the Plan.The probability of exposure of 10% and above defines the area which has a potential forenvironmental impact for up to 90% of the simulated conditions. This is considered to be areasonable representation of the likelihood of exposure of the environment to hydrocarbons inthe event of a spill due to the following:

♦ The ZPI represents a series of credible worst case scenarios across the project and themodelling outputs do not consider any spill prevention, mitigation or response.

♦ The ZPI represents a composite of the modelling information for surface, entrained anddissolved hydrocarbons across all three seasons (summer, winter and transition); and alldescribed spill scenarios.

Figure 3.2 shows the predicted ZPI resulting from combined modelling outputs at relevantthreshold criteria. Thresholds of exposure (surface, dissolved, entrained) used within the spillmodelling runs in the assessment of ecological impact are based on a review of relevantliterature. The dosage level (threshold value × duration) was used to assess the potential forexposure to subsea habitats and species by entrained and dissolved aromatic hydrocarbons.

A threshold of 10–25 g/m2 thickness was selected to define the ZPI for surface exposure. Thisis based on literature reviews of hydrocarbon effects on aquatic birds and marine mammals byEngelhardt (1983), Clark (1984), Geraci and St. Aubin (1988), and Jenssen (1994)(referenced within APASA 2013), that suggest the threshold thickness of hydrocarbonrequired to impart a lethal dose to an intersecting wildlife individual is 10 g/m2. Scholten et al.(1996) indicates that a hydrocarbon layer of 25 g/m2would be harmful for birds that contact theslick. This surface slick threshold was chosen as it defines the lower parameters at whichthere may be a potentially significant impact to marine mammals and sea birds should theevent occur (APASA 2013).

A threshold of 50–400 parts per billion (ppb) was selected to define the ZPI for dissolvedaromatics. This is based on global data from French et al. (1999) and French-McCay (2002,2003) (referenced within APASA 2013) which showed species sensitivity (fish andinvertebrates) to dissolved aromatics exposure greater than four days (96-hour LC50) underdifferent environmental conditions varied from 6– 400 μg/l (ppb). A range of 50 –400 ppb wasidentified to cover 95% of aquatic organisms tested, which included species exposed during

sensitive life stages (eggs and larvae). This dissolved aromatics threshold reflects thehydrocarbon concentration at which there may be a potentially significant impact to the marineenvironment (refer to Table 3.2).


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Table 3.2: Dissolved Aromatic In-water Threshold Values Appl ied as Part of theModelling Study

Trigger Value forDissolved Aromatic

Concentrations fo r a 96-

hour LC50 (ppb)

Equivalent Dosageof Dissolved Aromatics

(ppb.hrs)

Range of Sensitive SpeciesPotentially Impacted from

Acute Exposure

PotentialLevel of

Exposure

6 576Very sensitive species

(99th percentile)

Low exposure

50 4800 Average sensitive species

(95th percentile)

Moderate

exposure

400 38 400Tolerant sensitive species

(50th percentile)

High

exposure

The ZPI for entrained exposure was defined at 100–500 ppb as APASA (2013) suggest this

range could serve as an acute lethal threshold to 95% and 50% of biota respectively. Althoughthe ANZECC guidelines (2000) have the lowest trigger levels for total hydrocarbons in waterset at 10 ppb, a relatively long exposure time is required for these concentrations to besignificant. The threshold of 100 ppb was set here to indicate the zones where acute exposurecould potentially occur over shorter durations should the event occur (refer to Table 3.3).

Table 3.3: In-water (entrained) Threshold Values Applied as part of the Modelling Study

Trigger Value forEntrained Oil

Concentrations (ppb)

Equivalent Dosage ofEntrained Oil

(ppb.hrs)

Range of Sensitive SpeciesPotentially Impacted from

Acute Exposure

PotentialLevel of

Exposure

10 960Very sensitive species

(99th percentile) Low exposure

100 9600 Average sensitive species

(95th percentile)

Moderate

exposure

500 48 000Tolerant sensitive species

(50th percentile)

High

exposure


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Figure 3.2: Zone of Potential Influence developed from combined modelling outputsScenarios 1-4.


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Wheatstone Oil Spill Environmental Response PlanRevision: 1




4.0 POTENTIAL HYDROCARBON EFFECTS ONENVIRONMENTAL RECEPTORS

A number of different factors determine the degree of effects that can be expected from ahydrocarbon spill. These can be grouped into degrees of severity, such as heavy, long-

lasting effects, intermediate levels of effects, and comparatively little or no effects (NAS1985). The following factors are important in determining the levels of impact on biota:

♦ Geographic location

♦ Hydrocarbon dosage and impact area

♦ Application of dispersants

♦ Oceanographic and meteorological conditions

♦ Hydrocarbon type.

4.1 Impact Factors

4.1.1 Sensitivity

Sensitivity to toxic compounds varies greatly by species, by life stage within a particularspecies, and by individuals. In general, younger stages are more sensitive than adults (forexample, eggs and larvae are often more sensitive than adult fish), but some exceptionsexist (NAS 1985).

Hydrocarbon impacts between species groups, and within species, vary. Within species,individual characteristics may determine the degree of impact, including age, sex andcontamination history. As an example, a study on kelp shrimp found that animals that hadbeen previously exposed to naphthalene (a component of hydrocarbon) had less tolerance tothe compound. In contrast, pink salmon exhibited the opposite effect; fish that were

previously exposed to naphthalene had significantly greater tolerance when tested later withbioassays (Rice and Thomas 1989).

4.1.2 Toxicity

Toxicity is defined as, "The inherent potential or capacity of a material to cause adverseeffects in a living organism" (Rand and Petrocelli 1985). Concentration, duration of exposure,and sensitivity of the receptor organism all determine the toxic effect.

4.1.2.1 Acute Effects

Acute toxicity refers to immediate impacts that result in death of the organism. One acuteeffect of hydrocarbon on shoreline organisms is the physical process of smothering (NAS1985). Intertidal invertebrates and some plants may be especially sensitive to smothering.

Acute effects can also result from the toxic components of the hydrocarbon. Acute toxicity isdependent on the toxic properties of the hydrocarbon (a combination of the hydrocarbon typeand weathering), and the concentration and dose that the organism receives.

4.1.2.2 Chronic Effects

Some toxic effects may not be evident immediately, or may not cause the death of theorganism. These are called chronic or sub lethal effects, and they can impact an organisms'physiology, behaviour, or reproductive capability. Chronic effects may ultimately impact thesurvival rates of species affected. Chronic effects are harder to detect than acute effects andmay require more intensive studies conducted over a longer period of time.


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Many chronic effects result from stress responses in the physiology of an organism, such asincreased metabolism, increased consumption of oxygen, and reduced respiration rate.These can be short term responses, but over extended periods of time, may cause otherimpacts to the organism. A common chronic response is reduced growth rates, for examplein benthic organisms that live in chronically oiled sediments.

For plants, primary productivity or photosynthesis may be affected. Effects on reproductionfrom chronic exposure to hydrocarbon in sediments have been documented for benthic fishspecies. Changes in behaviour have also been noted for several species of fish andinvertebrates when exposed to hydrocarbon. One mechanism of impact of a sub lethal effectis the disturbance of an organism's chemosensory ability.

4.1.2.3 Bioaccumulation

Bioaccumulation can be defined as the uptake of a contaminant by an organism from waterdirectly or through consumption of contaminated food. Organisms that live in a contaminatedenvironment, for example, mussels in oiled sediments, may appear to be healthy but stillcontain elevated levels of petroleum compounds in their tissue. Some components of

hydrocarbon can be bioaccumulated by marine organisms, particularly the group of longerlasting compounds known as polycyclic aromatic hydrocarbons (PAH). PAHs are found inHFO, MDO and condensate at varying concentrations.

4.1.2.4 Biomagnification

Biomagnification is defined simply as the magnification of concentrations of a contaminantover two or more trophic levels. One concern with bioaccumulation is that contaminatedorganisms (such as oysters) may be eaten by higher trophic level organisms (such as birds).If biomagnification was occurring, the higher level predator (the bird) could concentratecontaminants to a level which would cause toxic effects. In the case of organisms that areharvested by humans, concerns about biomagnification may cause restrictions on collecting

shellfish or other items consumed by humans. However, biomagnification is not usually amajor concern with petroleum compounds originating from hydrocarbon spills (Hayes et al1992).

4.1.3 Cumulative Effects

The potential exists for cumulative impacts associated with the toxicity of both spilledhydrocarbons and subsequently applied chemical dispersant, which may account for thehigher levels of impacts that are observed for some species in comparison to the presence ofhydrocarbon or dispersant along, however, there are limited studies comparing these effectswhere hydrocarbon concentrations in the exposure medium have been well quantified.

4.2 Ecological Effects

Some ecological effects that alter predator-prey interactions may result from a spill and resultin changes in species composition or relative numbers of species in an area. This may becaused by the elimination of predators due to mortality.

4.2.1 Habitat Effects

4.2.1.1 Water column

Hydrocarbons in or on the water column have the potential to impact free-living organisms aswell as subtidal/intertidal habitats. The level of impact is determined by the type ofhydrocarbon (e.g. its toxicity/persistence), as well as the duration and intensity of exposure(e.g. weathered hydrocarbon compounds are less toxic than fresh) and the presence ofdispersants. The presence of hydrocarbons can occur as (i) surface slicks, (ii) dispersed intothe water column (commonly termed entrained); or (iii) dissolved into the water column.


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Hydrocarbons in the water column are small droplets (


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Biological toxic impacts to the associated community can be severe. Smothering andcontamination leads to mortality or shifts in density of the rich coral reef fauna and flora, andassociated marine predators. Hydrocarbon and dispersant may affect coral reproductionthrough exacting a high energy cost causing a reduction in fecundity of adult corals (NOAA2010). In addition, early developmental forms (like coral larvae) are particularly sensitive totoxic effects, and oil slicks can significantly reduce larval development and viability (Lane andHarrison 2000, Negri and Heyward 2000, Mercurio et al. 2004). It is likely that oil effectsoccur in sub lethal forms, such as reduced photosynthesis and growth making corals moresusceptible to natural disturbances such as coral bleaching (NOAA 2010). In addition to coralthemselves, hydrocarbons may also adversely affect the associated fish, invertebrates andplants in the coral reef community.

Clean-up activities, such as placement of booms and use of dispersants may impact coralreefs (NOAA 2010). Boom anchors can physically impact corals and the use of dispersantsover shallow submerged reefs may have more of an impact than the hydrocarbon exposure(NOAA 2010).

A number of dispersants have been identified as being potentially toxic to corals. Ardrox6120 was found to be toxic to planula larvae of the scleractinian corals Acropora tenuis,Platygyra sinensis and Goniastrea aspera with very high rates of larval mortality atdispersant concentrations of ≥75 ppm within 12 to 24 hours (Lane and Harrison 2000), however it is noted that this concentration is relatively high in comparison to exceptdispersant concentratios in the field.

The potential toxicity of dispersants to early life history stages of coral have also beenreported including the potential inhibition of fertilization success in Acropora tenuis (EC50 1.7 ppm) (Harrison 1999). While Ardrox 6120 appeared to be more toxic to coral gametes thanHFO alone (Harrison 1994). Settlement and survival of the larvae of P. astreoides andM. faveolata have been shown to decrease with exposure to high concentrations (50 ppm

and 100 ppm) of Corexit 9500 (Goodbody-Gringley et al. 2013) and in Acropora millepora exposed to Corexit 9527 (Negri & Heyward 2000).

In studies on symbiotic zooxanthallae, no impacts on cell density were found where coralswere exposed to Corexit 9527, and the zooxanthellae cells appeared undamaged even whentheir host tissue was damaged severely during short-term exposure (Scarlett et al. 2004).

Macroalgae Communities

Little data exists with regard to the impact of oil to macroalgae beds in tropical intertidalareas (Volkman et al. 1994). Studies conducted in temperate waters off Rhodes Islandfollowing the World Prodigy spill of marine diesel (Peckol et al. 1990) identified no significantimpacts on subtidal macroalgae communities and mixed effects on growth rates of intertidal

macroalgae communities. The study identified a strong correlation with distribution patternswhere macroalgae in low energy, sheltered intertidal areas were most strongly affected ascompared to higher energy intertidal areas.

Macroalgae are generally able to withstand the effects of oil more effectively than susceptibleanimals. Volkman et al. 1994 demonstrated the ability of algae to be exposed to highvolumes of hydrocarbon pollution and recover that was likely due to the new growth thatoriginates from the base of the organism. In addition, a layer of mucilage is present on mostspecies, preventing the penetration of toxic aromatic fractions (Volkman et al. 1994). Thiswas also reported by Connell et al. (1978), who suggested that fine hairs, complex frondarrangement, and the thickness of the mucilage covering may determine how much oil istrapped within or on the surface of the algae, thus determining its chance of survival.However, direct application experiments have shown that exposure to oil causes adepressive effect on algal photosynthesis. Aquatic biota of reduced diversity have been


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proposed (Velasquez, et al. 1973) and documented (McCauley, 1966; Straughan, 1970,1972; Straughan & Abbott, 1971; Cooper & Wilhm, 1975) to result from chronic exposure tooil or refinery effluents. Conversely, there are numerous reports of algal proliferationfollowing contamination (Perkins, 1968).

A number of dispersants have been identified as being potentially toxic to macroalgae.

Slickgone NS was tested on macroalgae germination (Hoormosia banksii), with a reportedEC50 >100 ppm (AMSA 2013). A review by Lewis and Pryor (2013) reports a range oftoxicities to different dispersants from 0.7 ppm of Corexit 9500, 20 ppm of Corexti 9527 andup to 27 000 ppm for other products impacting on germination of brown algae. Studies onadult plants only report sublethal impacts

Seagrass Communi ties

There are little data available with regard to the interaction between seagrass and petroleumhydrocarbons within a tropical intertidal environment, with most data describing impacts intemperate areas on seagrass communities from crude oil, rather than lighter hydrocarbonsincluding MDO and condensate (Volkman et al. 1994). Potential direct impacts identified

include mortality due to smothering and chemical toxicity. Indirect impacts could include areduction of photosynthesis due to reduced light, decrease in suitable habitat, accumulationof potentially carcinogenic or mutagenic substances and a reduction in seagrass tolerance toother stress factors (Peters et al. 1997 and Zieman et al. 1984). The degree of impact isdependent on the seagrass species, the type of hydrocarbon spilt and the degree of contact(Taylor & Rasheed 2011). Studies have found that seagrasses are able to withstand short-pulsed direct contact events with oil without prolonged negative impacts, provided thatsuccessive contact events are minimised (Taylor & Rasheed 2011).

Seagrass disperses predominantly through vegetative (clonal) growth, and secondarilythrough sexual reproduction and seed dispersal, carried by tides and currents. Halophila spp.are able to regenerate quickly from seeds stored in the sediments (Longstaff and Dennison,

1999) and are often the first species to colonise disturbed areas (Waycott et al., 2004;Waycott et al., 2005). A study by Nakaoka and Aioi (1999) found that it took two months for apatch within a seagrass bed that was removed of H. ovalis to reach the same state ofcolonisation prior to disturbance. Provided that the sediments are not contaminated,seagrass beds should be able to be recolonised after an oil-related mortality event ofseagrasses by seagrass populations in surrounding areas providing that sufficient natural oranthropogenic remediation has occurred.

Seagrass-dependant fauna such as epifauna, crustaceans, molluscs and fish, may also beimpacted (NOPSEMA 2012). The decline in cover of seagrass may have indirect impacts onthe juvenile life stages of recreationally and commercially important fish and crustaceanspecies that utilise seagrass meadows as a nursery ground (Skilleter et al. 2005). Dugongs,

which feed on seagrass meadows, may also be potentially affected by consumption ofhydrocarbon-contaminated seagrass.

A number of dispersants have been identified as being potentially toxic to seagrasses.Testing of Corexit 9527 and Ardrox 6120 both resulted in impacts on seagrassphotosynthesis within the first hour of exposure, at concentrations between 1 and 2% w/v,however this concentration range is relatively high compared to anticipated fieldconcentrations. For Thalassia testudinum, the 96-h LC50 concentration for Corexit 9527 wasreported as 200 ppm (Baca and Getter 1984) and a 48-hour EC50 value of 55 ppm wasreported for Zostera marina (Scarlett et al. 2005). Moderate effects on seagrassphotosynthesis were also observed for Slickgone LTSW and Corexit 9500 over a 4 hourexposure while Shell VDC was reported to result in photosynthetic stress after 10 hours ofexposure (Macinnis-Ng and Ralph 2003, Wilson & Ralph 2012).


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Clean up activity can have impacts on macroalgae and seagrass beds, particularly physicaldamage from trampling and boat activity in shallow water (Law et al. 2011). Dispersants canalso encourage the breakdown of the waxy cuticle of seagrasses, allowing greaterpenetration of hydrocarbons into leaves and increasing phytotoxicity.

Rock Pavement

Intertidal rock pavement constitute habitats for a variety of marine flora and fauna, typicallymicroalgae and invertebrate species, these organisms have adapted to high stress levels,with periods of desiccation, predation and sometime strong wave energies. This highlystressful environment creates zonation, especially in high energy environments (IPIECA2012).

The impact of a potential oil spill on a rock pavement environment depends on its topographyand flora and fauna communities which inhabit the substrate. Steep or vertical rock faces ona wave exposed coast is unlikely to have any impact from an oil spill event, while a graduallysloping rock platform in low energy environments, sheltered bays and inlets can trap oil(IPIECA 2012).

4.2.1.3 Shorelines

Observations of previous oil spills have provided the foundation for determining the potentialimpacts from hydrocarbons on shorelines and their associated biological communities.Previous spills have shown that the potential impact of oil on intertidal habitat is influenced bythe following:

♦ Shoreline type

♦ Exposure to wave and tidal energy

♦ Analysis of the natural persistence of the oil

♦

Productivity and sensitivity of biological resources♦ The ease of facilitating clean-up operations.

The potential impacts from hydrocarbons on each of the four coastal shoreline habitats aresummarised below.

Rocky Shore

The immediate effects of an oil spill on rocky shores are typically toxicity effects on thebenthos and high mortalities of associated wildlife (Yamamoto et al. 2003). The severity,distribution and persistence of rocky shore impacts can differ widely depending on the typeand volume of oiled spilled, characteristics of the affected shore and the tide and weatherconditions (Stevens et al. 2008).

Rocky shores which are exposed to wave action and the scouring effects of tidal currents areamongst habitats most resilient to the effects of a spill, and they tend to self-clean relativelyrapidly. Oil can be held offshore by waves reflecting off exposed steep shorelines anddeposited oil is rapidly removed on exposed shorelines from rock faces. On sheltered rockyshorelines oil adhere readily around the high tide mark; forming a distinct band where thelower part of the rock face stays wet, that could impact the communities of the upper zone.

Topographically complex rocky shoreline habitats that encompass a range of microhabitatssuch as cracks, crevices, rock pools and overhangs are at a heightened risk of impact from aspill as they often provide sites of oil pooling and persistence. These complex microhabitats

tend to retain water during low tides and so are populated by diverse fauna assemblages;including communities of highly adapted species of grazers and filter-feeders. Impacts toorganisms inhabiting these areas may include death from smothering, chronic toxicity and


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sub lethal effects from the exposure to hydrocarbons and their toxic fractions (Holdway et al.1997).

Sheltered rocky rubble slopes have the greatest potential for long-term persistence of oil,causing long-term contamination of the subsurface sediments due to the potential for oil topenetrate and persist in surficial sediments, if present. Impacts to the rich biological

communities of the lower intertidal zone would be largely dependent on the level of entrainedhydrocarbon in the water column.

The greatest impacts are likely to be encountered by birds when present at nesting coloniesor feeding in nearshore waters (Michel and Hayes 1992). The impact of response activities tomitigate hydrocarbon damage, such as cleaning with detergents, high pressure or hot waterwashing or scrubbing may also have impacts.

Sandy Beaches

The natural processes and physical characteristics of sandy beaches determines theirsusceptibility to an oil spill. Natural processes such as extent of tidal range and wave energy

influence the extent of spread and layering of oil on beaches: a high energy, wave dominatedbeach typically experience more spread and less layering than a low energy beach. Physicalcharacteristics, such as capillary action, grain size and permeability influence the depth ofpenetration into the sand. Fine grained sandy beaches are less sensitive to oil pollution thanother sandy substrates due to their comparably sparse infauna and/or epifauna and oilcannot penetrate too deeply, also making the beach relatively easy to clean. Biologicalimpacts from exposure to spilled oil or toxic fractions of oil on sandy beaches includetemporary declines in infaunal and epifaunal populations, which can also affect feedingshorebirds and seabirds (Michel and Hayes 1992).

Mangroves and Depositional Shorelines

Mangroves are particularly susceptible to the impacts of a hydrocarbon spill as they are

dependent on oxygen-supplied via pores in their aerial roots (Getter et al. 1984). The toxiccomponents of hydrocarbons can also damage cell membranes in the subsurface roots,impair the normal salt exclusion process and the resulting influx of salt interferes with theplants ability to maintain osmotic balance (IPIECA 2011).

Oil adheres readily to the vegetation in mangrove habitat and may form multiple bands ofcoating, depending on the tidal stage at the time of exposure to the oil. Large surface slickstypically persist through multiple tidal cycles smothering vegetation. The oil may also poolwithin sediments at the base of vegetation and deeply into burrows and prop root cavities.Thick vegetation can restrict contamination to the shoreward fringe depending on the type ofoil; heavier refined products penetrate vegetated areas to a lesser extent.

Biological impacts can be severe. Smothering and contamination may lead to mortality ofplants, seedlings and propagules. The associated rich fauna and flora may suffer mortality orshifts in density. Where oili

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