Wheatstone Oil Spill Operational and Scientific Monitoring Program

8/18/2019 Wheatstone Oil Spill Operational and Scientific Monitoring Program

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© Chevron Australia Pty Ltd

Document No: WS0-0000-HES-PLN-CVX-000-00093-000 Revision: 1

Revision Date: 30 October 2013

IP Security: Public

Wheatstone ProjectOil Spill Operational and ScientificMonitoring Program


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Wheatstone Project Document No: WS0-0000-HES-PLN-CVX-000-00093-000

Oil Spill Operational and Scientific Monitoring ProgramRevision: 1

Revision Date: 30/10/2013

© Chevron Australia Pty Ltd Public Page 2

Printed Date: 4/2/2014 Uncontrolled when printed

TABLE OF CONTENTS

ACRONYMS, ABBREVIATIONS AND TERMINOLOGY ....................................................... 5

1.0 BACKGROUND ............................................................................................................ 8

1.1 Project Overview .................................................................................................. 8

1.2

Proponent ............................................................................................................ 8

1.3 Objectives ............................................................................................................8

1.4 Scope ................................................................................................................. 11 1.4.1

Relevant Project Phase ........................................................................ 11

1.4.2 Relevant Tiers of Spill ........................................................................... 11 1.4.3 Costs .................................................................................................... 12

1.5 Environmental Approvals ................................................................................... 14

1.6 Public Availability ............................................................................................... 15

1.7 Review, Approval and Revision of this Program ................................................. 15 1.7.1 Provision for Periodic Review ............................................................... 15 1.7.2 Peer Review ......................................................................................... 15

2.0

PROJECT DESCRIPTION .......................................................................................... 16

2.1 Offshore Facilities .............................................................................................. 16 2.1.1 Well Design and Control Procedures .................................................... 16 2.1.2 Trunkline and Shore Crossing .............................................................. 16

2.2 Nearshore Facilities ........................................................................................... 16 2.2.1 Materials Offloading Facility .................................................................. 17 2.2.2

Product Loading Facility ....................................................................... 17

2.3 Construction Vessels.......................................................................................... 17

3.0

HYDROCARBON SPILL SCENARIOS ....................................................................... 19

3.1

Overview ............................................................................................................ 19

3.1.1

Worst Case Credible Spill Scenario ...................................................... 19 3.2 Definition of the Tiered Response ...................................................................... 20

3.2.1

Zone of Potential Impact and the Environment that May Be Affected.... 21

3.2.2 Biological Thresholds to determine the Zone of Potential Impact .......... 22 3.2.3

Probability of Hydrocarbon Exposure .................................................... 23

3.2.4 Modelling results................................................................................... 23

4.0 POTENTIAL HYDROCARBON EFFECTS ON ENVIRONMENTAL RECEPTORS ..... 26

4.1 Overview ............................................................................................................ 26

4.2 Toxicity ............................................................................................................... 26

4.3 Sensitivity ........................................................................................................... 26

4.4 Acute Effects ...................................................................................................... 26

4.5

Chronic Effects ................................................................................................... 26

4.5.1 Bioaccumulation ................................................................................... 27 4.5.2

Biomagnification ................................................................................... 27

4.6 Ecological Effects ............................................................................................... 27

4.7 Receptor Specific Effects ................................................................................... 27 4.7.1 Water column ....................................................................................... 27 4.7.2 Seabed ................................................................................................. 28 4.7.3

Shorelines ............................................................................................ 31

4.7.4 Shorebirds and Seabirds ...................................................................... 33 4.7.5 Marine Megafauna ................................................................................ 35 4.7.6

Fish and fish communities .................................................................... 39

5.0

THE ENVIRONMENT THAT MAY BE AFFECTED ..................................................... 41

5.1 Provincial Bioregion Ecosystem Characterisation ............................................... 41


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5.2 Resources at Risk .............................................................................................. 45

5.3 Matters and species of NES ............................................................................... 48

5.4 Oil Spill Response Atlas ..................................................................................... 56

6.0 MONITORING PROGRAM OVERVIEW ..................................................................... 69

6.1 Implementation................................................................................................... 70

7.0

REPORTING ............................................................................................................... 78

7.1 Annual Compliance Reporting ............................................................................ 78

7.2

Non-compliance Reporting ................................................................................. 78

7.3

Other Reporting .................................................................................................. 78

8.0 REFERENCES ............................................................................................................ 79

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

relevant to this Program ................................................................................... 14

Table 3.1: Worst-case Credible Tier 3 Hydrocarbon Spill Scenarios ..................................... 20

Table 3.2: Possible Triggers for determining Response Tier Level ....................................... 21

Table 3.3: Dissolved Aromatic In-water Threshold Values Applied as Part of theModelling Study ............................................................................................... 22

Table 3.4: In-water (entrained) Threshold Values Applied as part of the Modelling Study ..... 23

Table 3.5: Summary of shoreline contact probability and minimum time to shore –surface expression* of the spill......................................................................... 25

Table 5.1: Description of Provincial Bioregions within the combined ZPI and EMBA ............ 42

Table 5.2: Matters of NES and Resources at Risk ................................................................ 47

Table 5.3: Commonwealth and State Marine Reserves in the EMBA ................................... 49

Table 5.4: Key Ecological Features ...................................................................................... 54

Table 6.1: OPS and SCI initiation and termination criteria .................................................... 71

FIGURES

Figure 1.1: Location of Wheatstone Project Infrastructure ...................................................... 9

Figure 1.2: Wheatstone Production Well Site Locations ....................................................... 10

Figure 1.3: Wheatstone Combined Zones of Potential Impact for the Construction Phase ... 13

Figure 2.1: Schematic of the Field Layout............................................................................. 18

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

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

Figure 5.1: Provincial Bioregions of the EMBA ..................................................................... 44

Figure 5.2: Map indicating the level of baseline data available for geographical areaswithin the EMBA .............................................................................................. 46

Figure 5.3: State and Commonwealth Marine Reserves and Project Marine Facilities ......... 52

Figure 5.4: Key Ecological Features ..................................................................................... 55

Figure 5.5: Overview over the Oil Spill Response Atlas figures ............................................ 57

Figure 5.6: Oil Spill Response Atlas – Montebello Islands .................................................... 58

Figure 5.7: Oil Spill Response Atlas – Barrow Island ............................................................ 59

Figure 5.8: Oil Spill Response Atlas – South Barrow Island .................................................. 60

Figure 5.9: Oil Spill Response Atlas – Airlie Island ............................................................... 61


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Figure 5.10: Oil Spill Response Atlas – Thevenard Island .................................................... 62

Figure 5.11: Oil Spill Response Atlas – Peak to Bessieres Islands ....................................... 63

Figure 5.12: Oil Spill Response Atlas – Muiron Islands......................................................... 64

Figure 5.13: Oil Spill Response Atlas – North West Cape .................................................... 65

Figure 5.14: Oil Spill Response Atlas – Turquoise Bay to Torpedo Bay ................................ 66

Figure 5.15: Oil Spill Response Atlas – Sandy Point to Turquoise Bay ................................. 67 Figure 5.16: Oil Spill Response Atlas – Beacon Point to Sandy Point................................... 68

Figure 6.1: An Overview of the Operational and Scientific Monitoring Programs .................. 70

Figure 6.2: Oil Spill Operational and Scientific Monitoring Program ImplementationStrategy and Timelines .................................................................................... 77

APPENDICES

APPENDIX A ACTION TABLE ................................................................................... 99

APPENDIX B EPBC LISTED SPECIES ................................................................... 103

APPENDIX C

HYDROCARBON PROPERTIES ....................................................... 114


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ACRONYMS, ABBREVIATIONS AND TERMINOLOGY

ABU Chevron Pty Ltd Australasia Business Unit

AEMT Chevron Pty Ltd Asset Emergency Management Team

ANSIA Ashburton North Strategic Industrial Area

APASA Asia Pacific Applied Science Associates

API gravity American Petroleum Institute gravity: a measure of how heavy or light a

petroleum hydrocarbon is compared to water

bbl Barrel(s)

bbl/MSCF Barrels per million standard cubic feet

bbl/d Barrels per day

BOP Blow-out preventers

CAR Compliance Assessment Report

Chevron Chevron Australia Pty Ltd

CMA Commonwealth Marine Area

Construction

Phase

For the purpose of this Program the Construction Phase will encompass

activities undertaken to construct the production wells for the Project

cST centiStokes

Cth Commonwealth

DBNGP Dampier-to-Bunbury Natural Gas Pipeline

DEC Department of Environment and Conservation (WA) – currently Department of

Parks and Wildlife (WA)Dissolved

hydrocarbon

Dissolved hydrocarbon refers to the water soluble component of petroleum

hydrocarbons. These components will dissolve into the water column and can

be hazardous to aquatic organisms because of the acute toxicity of certain

compounds common to all petroleum liquids.

Domgas Domestic gas

DOTE Department of the Environment – formerly SEWPaC

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

Programme

EMBA Environment that May Be Affected is defined for the purpose of this plan as an

area that extends beyond the combined ZPI boundary to reflect the possibleneed to monitor reference sites and/or areas within which changes in

environmental quality associated with a spill may occur, but where these

changes would not result in a significant impacts to matters of NES and CMA.

EMP Environment Management Plan

EMT Chevron Pty Ltd Emergency Management Team

eNGO Environmental Non-Government Organisation

EP Act (WA) Environmental Protection Act 1986

EPA Environmental Protection Authority (WA)

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

EPBC 2008/4469 The Commonwealth Primary Environmental Approval, and conditional


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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

time.

Final EIS/RTS Final Environmental Impact Statement/Response to Submissions on the

Environmental Review and Management Programmeha hectare(s)

HES Health, Environment and Safety

Hydrocarbon Hydrocarbon refers to petroleum hydrocarbons including gas condensate. The

term ‘hydrocarbon’ and the term ‘oil’ may be used interchangeably throughout

this Program.

IEMT Chevron Pty Ltd Incident Emergency Management Team

IMCRA Integrated Marine and Coastal Regionalisation of Australia

km kilometre(s)

LAT Lowest astronomical tide

LNG Liquefied Natural Gas

m metre(s)

mAHD Metres above Australian Height Datum (approximately the height above mean

sea level)

MOF Materials Offloading Facility

MTPA Million tonnes per annum

Nearshore Marine habitat from the 20 m contour to the shoreline

NES Matters of National Environmental Significance

OE Operational Excellence

Offshore Marine habitat beyond the 20 m contour to the shoreline

Oil Oil refers to petroleum hydrocarbons including gas condensate. The term ‘oil’

and the term ‘hydrocarbon’ may be used interchangeably throughout this

Program.

OPS Operational studies for the Oil Spill Operational and Scientific Monitoring

Program OSERP Oil Spill Environment Response Plan

OSRA Oil Spill Response Atlas

PAH Polycyclic Aromatic Hydrocarbons

(The) Panel Technical Advisory Panel

PIN Pilbara Inshore bioregion

PIO Pilbara Offshore bioregion

ppb Parts per billion

(The) Program Oil Spill Operational and Scientific Monitoring Program

PLF Product Loading Facility

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

Practicable Reasonably practicable having regard to, among other things, local conditions

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


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knowledge (taken from the EP Act)

Proponent Chevron Australia Pty Ltd

SCI Scientific studies for the Oil Spill Operational and Scientific Monitoring Program

SEWPaC Department of Sustainability, Environment, Water, Population and Communities

(Cth) – currently Department of Environment (Cth)SIC Shared Infrastructure Corridor

Southern Group of

Islands

Includes Thevenard Island, Serrurier Island, Bessier Island, Peak Island, Tent

Island and the Rivoli Islands

Summer season Defined for the purpose of this Program as the meteorological period each year

including October, November, December, January, February and March.

TD Total depth (in relation to well drilling activity)

Transitional

season

Transitional season is defined for the purpose of this Program as the

meteorological periods each year between the Summer and Winter seasons

(April and September)

MS 873 Ministerial Statement No. 873: The State (WA) Primary Environmental Approval,

and conditional requirements for the Wheatstone Project. Government of

Western Australia, Minister for the Environment; Water, Hon. Bill Marmion MLA,

30 August 2011 as amended from time to time.

Middle Group of

Islands

Includes the Mangrove Islands, Great Sandy Island, North Sandy Island and

Mary Ann group of Islands

SME Subject Matter Experts

WA Western Australia

Winter season Winter season is defined for the purpose of this Program as the meteorological

period each year including May, June, July and August

Worst case

maximum credible

hydrocarbon spill

scenario

A worst case maximum credible hydrocarbon spill scenario is defined for the

purpose of this Program as a hydrocarbon spill scenario with the potential to

cause the most significant environmental impacts

ZPI Zone of Potential Impact is defined for the purpose of this Program to represent

the maximum geographical extent predicted to be subject to significant impacts

to listed threatened and migratory species of the EPBC Act and CMA from a

credible worst case hydrocarbon spill scenario.


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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 process gas producedfrom Production Licences WA-46-L, WA-47-L, WA-48-L and WA-49-L, located 145 kmoffshore from the mainland, approximately 100 km north of Barrow Island and 225 km northof Onslow and will also process gas to be produced from other offshore production licenceslocated nearby operated by Apache Corporation. This Project excludes the extraction of gasfrom the Julimar-Brunello fields (WA-49-L) and the transportation of that gas in flow lines

from the wells to the Wheatstone Platform (Julimar Development Project). ApacheCorporation is the proponent of the Julimar Development Project.

Figure 1.1 shows the location of the Wheatstone Project and Figure 1.2 shows the locationsof the Wheatstone production wells within the Production Licences. The ANSIA site islocated approximately 12 km south-west of Onslow along the Pilbara coast within the Shireof Ashburton. The initial Project will consist of two LNG processing trains, each with acapacity of approximately 5 million tonnes per annum (MTPA), and a Domgas plant.Environmental approval was granted for a 25 MTPA LNG facility and associated Domgasplant to allow for the expected further expansions. The Domgas plant will be a separate butco-located facility and will form part of the Project. The development of the Domgas plantalso includes onshore pipeline installation to tie-in to the existing Dampier-to-Bunbury Natural

Gas Pipeline (DBNGP) infrastructure.

1.2 Proponent

Chevron is the proponent and the operator of the Project on behalf of its joint ventureparticipants Apache Corporation, Tokyo Electric Power Company (TEPCO), Kuwait ForeignPetroleum Exploration Company (KUFPEC), Shell and Kyushu Electric Power Company(Kyushu).

1.3 Objectives

The objective of the Oil Spill Operational and Scientific Monitoring Program (the Program orOSOSMP) is to provide a suite of monitoring plans that will be enacted (if appropriately

triggered) in the event of a hydrocarbon spill, during the Construction Phase of the Project, toinform spill response (operational plans) operations and clean up and to determine thepotential extent and impacts on Environmental Protection and Biodiversity Conservation Act1999 (EPBC Act) listed threatened and migratory species (matters of National EnvironmentalSignificance [NES]) and the Commonwealth Marine Area (CMA) (scientific plans).


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Figure 1.1: Location of Wheatstone Project Infrastructure


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Figure 1.2: Wheatstone Production Well Site Locations


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1.4 Scope

This Program has been prepared with a focus on protecting EPBC Act listed threatened andmigratory species and the CMA to meet the requirements of EPBC 2008/4469 Condition 50(Table 1.1). The Program provides a series of operational and scientific plans that will beimplemented (if appropriately triggered), in the event that a hydrocarbon spill attributable to

the Project occurs in the marine environment during the Construction Phase (as defined inSection 1.4.1).

The operational plans (termed OPS plans in this Program) will be undertaken to guide andinform response strategies for the spill. Scientific plans (termed SCI plans in this Program)will assist in determining the potential extent of impacts from the spill from responsestrategies, infer ecosystem consequences, and potential environmental remediation ofimpacts on the CMA and EPBC Act listed threatened and migratory species required as aresult of the spill (refer to Section 6.0 for further details).

1.4.1 Relevant Project Phase

For the purpose of this Program the Construction Phase relates to the Project phase tocomplete the following construction scopes:

1. Drilling and Completions:a. Production Drilling and Well Site Completions.

2. Upstream:a. Trunkline and flow lines installationb. Secondary stabilisation of the trunklinec. Dewatering and drying of the trunklined. Microtunnel activitiese. Jacket and topsides installation.

3. Downstream:

a. Dredging of the shipping channel, PLF and MOFb. PLF Constructionc. MOF Constructiond. Module deliverye. Onshore Construction.

The operations phase for the Project is not dealt with in this Program. Credible worst casehydrocarbon spill scenarios relevant to the operations phase of the Project will be dealt within an update to this Program, or a separate Program, that will be submitted for review andapproval by the Department of the Environment (DOTE).

1.4.2 Relevant Tiers of Spill

The Program is focussed on Tier 3 hydrocarbon spills due to the potential significantconsequences of Tier 3 spills to the environment. A Tier 3 hydrocarbon spill is defined inSection 3.2. The consequence of a Tier 3 spill scenario, compared to a Tier 2 and Tier 1 spillscenario, is potentially significant due to the likely extended duration (highest potentialrelease volume) and subsequent widespread exposure of the environment to the releasedhydrocarbons presenting risks to sensitive receptors. The risks to sensitive receptors may befrom direct or indirect hydrocarbon exposure as well as detrimental effects from containmentstrategies and or clean-up actions.


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1.4.3 Costs

Condition 54 of EPBC 2008/4469 provides that in the event of a hydrocarbon spill the persontaking the action will cover the costs associated with the operational and scientific monitoringprograms, set out within this plan, in the event of a hydrocarbon spill attributable to theProject. Costs associated with operational and scientific monitoring programs instigated and

undertaken by other parties in response to a hydrocarbon spill attributable to the Project willnot be covered by the Proponent unless approval by the Proponent has been provided inwriting. Costs associated with environmental remediation will be covered by the Proponent tothe extent determined necessary by the operational and scientific monitoring programs(EPBC 2008/4469 Condition 54). Costs of remediation associated with, or as a result of,operational and scientific monitoring programs instigated and undertaken by other parties inresponse to a hydrocarbon spill attributable to the Project will not be covered by theProponent unless approval by the Proponent has been provided in writing. Approval of thethird party costs associated with operational and scientific monitoring and environmentalremediation will be provided on a reimbursable basis and may only be provided by Chevronmanagement, subject to approval of relevant joint venture partners (JVP), and on the adviceof the Chevron ABU Asset Emergency Management Team (AEMT). The AEMT is tasked

with managing hydrocarbon spill response.


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Figure 1.3: Wheatstone Combined Zones of Potential Impact for the ConstructionPhase


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1.5 Environmental Approvals

The Wheatstone Project was assessed through an Environmental ImpactStatement/Environmental Review and Management Programme (EIS/ERMP) assessmentprocess under the WA Environmental Protection Act 1986 (EP Act) and the CommonwealthEPBC Act. The Commonwealth Minister for Sustainability, Environment, Water, Population

and Communities approved the Wheatstone Project on 22 September 2011 (EPBC2008/4469) with variations to EPBC 2008/4469 conditions 44, 45, 55, 56 and 66 madepursuant to section 143 of the EPBC Act. Other amendments may be made from time to timeand if so will be reflected as appropriate in the next revision of this Program. This Program has been prepared to meet the requirements of EPBC 2008/4469 Condition 50 (Table 1.1).

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

No. Condition Section

50 The person taking the action must develop and submit to the Minister forapproval, an Oil Spill Operational and Scientific Monitoring Program

(OSOSMP) that will be implemented in the event of a hydrocarbon spill to

determine the potential extent and impacts of such a spill on the

Commonwealth marine area and EPBC Act listed threatened and migratory

species, including, but not limited to:

This Program

50 a Triggers for the initiation and termination of the OSOSMP, including, but not

limited to, spill volume, composition, extent, duration and detection of

impacts

Section 6.1 ,

Table 7-1,

and OPS and

SCI programs

respectively

50 b A description of the studies that will be undertaken to determine theoperational response, potential extent of impacts, ecosystem consequences

and potential environmental remediations required as a result of the oil spill

OPS and SCI programs

respectively

50 c Inclusion of sufficient baseline information on the biota and the environment

that may be impacted by a potential hydrocarbon spill, to enable an

assessment of the impacts of such a spill

Section 5.0

and OPS and

SCI programs

respectively

50 d A strategy to implement the OSOSMP, including timelines for delivery of

results and mechanisms for the timely peer review of studies

OPS and SCI

programs

respectively

50 e Provision for periodic review of the program Section 1.7

54 In the event of hydrocarbon spill the person taking the action must pay all

costs associated with all operational and scientific monitoring undertaken in

response to the spill and all costs associated with any environmental

remediation determined necessary by the results of the approved OSOSMP

Section 1.4

EPBC 2008/4469 Conditions 5 and 6 requires that Chevron may only implement theWheatstone Project otherwise than in accordance with the provisions of this Program whichregulate the matters of NES relevant to this Program from the date of approval of anyvariation to this Program by the Commonwealth Minister.


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1.6 Public Availabili ty

EPBC 2008/4469 condition 8 requires Chevron to publish this Program on its website withinone month of being approved, unless otherwise agreed to in writing by the Minister.EPBC 2008/4469 Condition 2 requires that Chevron retains information relevant to theimplementation of the Wheatstone Project. In the event that this Program, or parts of this

Program, is required to be implemented the final reports from the implemented Operational(OPS) and Scientific (SCI) studies will be made available to DOTE and the public uponrequest.

1.7 Review, Approval and Revision of this Program

Chevron is committed to conducting activities in an environmentally responsible manner andaims to implement reviews of its environmental management actions as part of a programmeof continuous improvement. This commitment to continuous improvement means that theProponent will review the Program, including individual monitoring programs, to addressmatters such as the overall effectiveness, environmental performance, changes inenvironmental risks and changes in business conditions on an as needed basis (e.g. in

response to new information).

1.7.1 Provision for Periodic Review

EPBC 2008/4469 Condition 50e requires Chevron to make provision for periodic review ofthe operational and scientific monitoring plans within this Program. To reflect currentscientific practice in operational and scientific monitoring, Chevron will review the Programperiodically, approximately every five years, and include peer review in the review processwhen this is required. The requirement for peer review will be determined based on thedegree of change in scientific practice.

An update to this Program, or a separate Program, will be submitted for approval to DOTE inaccordance with EPBC 2008/4469 Condition 50 for the Operations Phase of the Project.

1.7.2 Peer Review

EPBC 2008/4469 Condition 50d requires Chevron to provide mechanisms for the timely peerreview of studies. Chevron engaged a Technical Advisory Panel (Panel) to advice on theformulation and review of this Program. Chevron intends that the Panel continue to be themeans by which independent specialist scientific knowledge and peer review can begarnered to assist in the revision and update process outlined in Section 1.7.1 to deliver arobust and ‘fit for purpose’ Program.

In the event of a hydrocarbon spill triggering the requirements for implementation of thisProgram, or components of the Program, the relevant triggered SCI plans will be subject to a

peer review. The peer review will be conducted upon completion of the reports generated bythe relevant studies. The peer review of studies may be undertaken by the Panel ifappropriate. In the event that Panel members are involved in the development andimplementation and reporting of the studies Chevron will identify peer reviewers outside thePanel. The peer reviewers will be selected based on relevant experience and skill setsappropriate to individual operational and scientific plans.


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2.0 PROJECT DESCRIPTION

The Project facilities and activities described in the following have been included for thepurpose of contextualising the management and monitoring measures which are requiredunder this Program. Project characteristics may be amended from time to time. The key

Project characteristics which are detailed in this Program should therefore be read as subjectto any project amendments which are made from time to time.

2.1 Offshore Facil ities

The construction of offshore facilities includes a subsea system, platform and trunkline whichare detailed in the following sections.

The key characteristics of the offshore Project facilities include a platform and a subseaconcept for wells and manifolds. The Wheatstone Platform will be a manned facility 145 kmoffshore located in the West Carnarvon Basin in approximately 70 m water depth (LAT). ThePlatform provides the initial treatment of gas and natural gas condensate (hydrocarbonliquids) to be transported via trunkline to the onshore LNG processing facility. The platform

comprises a steel gravity based structure. The subsea concept for wells and manifoldscurrently includes up to 35 subsea production wells drilled during the life of the Project.

2.1.1 Well Design and Contro l Procedures

Each well will be fitted with an arrangement of valves, controls and instrumentation referredto as a “christmas tree” located on the seafloor. Safety valves will be installed in each well toenable isolation of the gas reservoir that will close automatically in the event of a mechanicalfailure or loss of system integrity. A “choke” valve will also be included to control the fluid flowand pressure from the well to the flow line. Each group of wells will use “well jumpers” toconnect them to their “cluster manifolds”. Each cluster manifold will serve between one andeight wells. From these cluster manifolds, tie-in spools will transfer fluids to the feed gas flow

line(s). Production fluids will be transported along the feed gas flow lines(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 linesand chemical injection lines. A schematic of the field layout is provided in Figure 2.1.

2.1.2 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 kmfrom the Wheatstone platform to the shore crossing. See Figure 1.1 for location of theWheatstone platform and Figure 1.2 for shore crossing location.

Nearshore the trunkline will be stabilised, to prevent movement. This is done by the use oftrenching and engineered backfill to minimise impact on shipping, stabilise the pipeline undercyclonic conditions and protect 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 diameterof approximately 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 Nearshore Facil ities

The construction of nearshore facilities will include a Materials Offloading Facility (MOF),

Product Loading Facility (PLF) and associated shipping channel, which are detailed in thefollowing sections.


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2.2.1 Materials Offloading Facility

The 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 formarine contractors during construction.

Pilot boat and tug movements associated with the arrival and departure of the LNG andcondensate carriers are berthed at the MOF. The MOF provides a base for marineoperations craft such as tugs, security and line handling vessels. Breakwater(s) at the MOFentrance, extending from the shoreline, create a safe operating environment inside the basinduring normal conditions and during a cyclone. An access channel and turning basinprovides access to the main navigation channel.

2.2.2 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. ThePLF is likely to carry a roadway and a double pipe rack from the shore to the PLF operationsplatform from where loading operations will be controlled. The pipe rack accommodates LNGand condensate loading lines, an LNG vapour return line, fire water pipe work andcommunications cabling.

2.3 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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Figure 2.1: Schematic of the Field Layout


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3.0 HYDROCARBON SPILL SCENARIOS

3.1 Overview

Construction activities for the Wheatstone Project are divided into three distinct constructionscopes including Drilling and Completions, Upstream and Downstream activities (refer to

Section 1.4.1 for further details).

In order to prepare this Program and to meet the requirements of EPBC 2008/4469Condition 50 the scope of works for construction activities were reviewed and a spill scenariowhich reflected the most likely impact to EPBC Act listed threatened and migratory speciesand CMA were selected. Several credible spill scenarios of varying Tiers (Section 3.2.4) were modelled to inform risk assessment processes. The risk assessment of the crediblehydrocarbon spill scenarios established that there are no significant environmental risks fromthe credible Tier 2 or Tier 1 spill scenarios and as a result it was determined that only aTier 3 hydrocarbon spill will attract the monitoring response set out within this Program.

Furthermore, the assessment established that the activities of concern for a Tier 3 spill to the

environment from the Project during the Construction Phase include bunkering activitiesassociated with the dredging fleet and pipeline installation vessels and the production welldrilling. The hydrocarbons of concern include Heavy Fuel Oil (HFO), Marine Diesel Oil(MDO) and gas condensate. Further details of these hydrocarbons are found in Appendix C(Company Confidential). Consideration of relevant Tier 3 hydrocarbon spill scenarios foractivities associated with the operations phase of the Project will be included in an update, ora separate or revision, of his Program for the operations phase.

3.1.1 Worst Case Credible Spill Scenario

A worst case maximum credible scenario is defined for the purpose of this Program as ahydrocarbon spill scenario with the potential to cause the most significant environmental

impacts. The three scenarios identified as the worst case credible hydrocarbon spills for theProject during the Construction Phase were chosen due to the type and volume ofhydrocarbon that could potentially be released and the proximity to potentially sensitive areasor habitats. Modelled Spill scenarios include:

♦ Scenario 1: Marine Diesel Oil (MDO) spill at a location in Western Australia (WA) Statewaters 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 alocation with the greatest risk of impact to nearshore habitats such as coral reefs andoffshore islands.

♦ Scenario 2: Heavy Fuel Oil (HFO) spill at the boundary of Commonwealth/State waters

represents the largest potential loss of HFO and is associated with bunkering the offshorepipelay vessel.

♦ Scenario 3: 11 week uncontrolled well-blow at the IAG-1E production was selected as ithas the highest identified hydrocarbon flow rate, is located in relatively shallower waterand is located relatively closer to sensitive shorelines; therefore has the potential tocause the greatest shoreline impacts in comparison to the other Wheatstone productionwells.

Details of the hydrocarbon spill scenarios are provided in Table 3.1.


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Table 3.1: Worst-case Credible Tier 3 Hydrocarbon Spill Scenarios

Scenario Location Type Spill Event Volume/ rate

1 WA state waters

(10 km from shore)

Marine Diesel Oil Surface release over

6 hours

265.5 m3

2 WA state /

Commonwealth

waters boundary

Heavy Fuel Oil Surface release over

6 hours

850 m3

3 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 Defin ition of the Tiered Response

Marine pollution response is based on a graduated scale of response whereby the amount ofresources mobilised for a response and the agency in control will vary according to the scaleand location of the incident. The levels, or response Tiers, are defined according to:

♦ The amount and source of resources deployed

♦ The levels of support and higher level management activated

♦ The spill volume and composition of hydrocarbon

♦ The location of the spill, potential extent of impact and ecosystem consequences.

Table 3.2 will be used to assist in determining response Tier level (adapted from WestPlan -MOP guidelines, DoT 2010). The Tier level is determined by the most severe trigger levelmet by the spill, e.g. if only one trigger is met by the spill for Tier 3 the spill is determined tobe a Tier 3 spill.


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Table 3.2: Possible Triggers for determining Response Tier Level

Tier 1

♦ Spill size (0–10 tonnes)

♦ Potential for Environmental Damage / Harm = Low (not significant)

♦ Potential for Economic Damage / Harm = Low (not significant)

♦ Pollution incident is within Tier 1 capability

Tier 2

♦ Spill size (10–1000 tonnes)

♦ Potential for Environmental Damage / Harm = Moderate (local or short-term significance)

♦ Potential for Economic Damage / Harm = Moderate (local or short-term significance)

♦ Pollution incident exceeds Tier 1 capability

Tier 3

♦ Spill size (>1000 tonnes)

♦ Potential for Environmental Damage / Harm = High (regional or long-term significance)

♦ Potential for Economic Damage / Harm = High (regional or long-term significance)

♦ Pollution incident exceeds Tier 2 capability

3.2.1 Zone of Potential Impact and the Environment that May Be Affected

The respective Zones of Potential Impact (ZPI) for the three modelled scenarios arepresented in Figure 1.3. The ZPIs represent the combined output of stochastically modelled

spills for three defined meteorological seasons; summer, winter and transitional. The ZPIsare inclusive of entrained, dissolved aromatic and surface expression of spills and representsthe maximum geographical extent predicted to be subject to moderate or high threshold levelimpacts to EPBC Act listed threatened and migratory species and the CMA. Each of themodelled scenarios reflects a combined plot of 100 (HFO scenario) and 50 (MDO and gascondensate scenarios) repeated simulation outputs for each season (refer to Appendix D).The Program also includes reference to the Environment that May be Affected (EMBA) thatextends beyond the combined ZPI boundary to reflect the possible need to monitor referencesites and/or areas within which changes in environmental quality associated with a spill mayoccur, but where these changes are predicted to only potentially result in low levels ofimpacts to EPBC Act listed threatened and migratory species and the CMA. The EMBAprovides the broad area within which EPBC Act listed threatened and migratory species and

the CMA relevant to this Program are identified. The distributions and abundances within theEMBA have been identified through:

♦ A range of environmental surveys conducted by Chevron

♦ Data sharing agreements with other oil and gas Operators

♦ Information gathered from other Third Party sources (including literature reviews)

♦ Outputs generated from the Protected Matters Search Tool

♦ Outputs generated from the Conservation Values Atlas.


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Section 5.0 provides an overview of the EMBA, including listed threatened and migratoryspecies of the EPBC Act and CMA for the Program. Further details on relevant baseline dataare provided within individual OPS and SCI monitoring plans.

3.2.2 Biological Thresholds to determine the Zone of Potential Impact

The hydrocarbon spill modelling assessed the likely probability of hydrocarbon contact withthe sea surface and shorelines. This exposure was calculated using a three-dimensionaltrajectory and fates model, SIMAP. The model is able to track hydrocarbons to levels that arevery low, however, to ensure meaningful levels are applied in terms of biological importancethreshold levels for biological impacts were determined based on literature reviews (APASA2013).

Thresholds of exposure (surface, dissolved, entrained) used within the spill modelling runsfor use in the assessment of ecological impact are based on a review of relevant literature.The dosage level (threshold value × duration) was used to assess the potential for exposureto 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.This is based on literature reviews of hydrocarbon effects on aquatic birds and marinemammals by Engelhardt (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/m 2. Scholten et al.(1996) indicates that a hydrocarbon layer of 25 g/m2would be harmful for birds that contactthe slick. 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 duringsensitive life stages (eggs and larvae). This dissolved aromatics threshold reflects thehydrocarbon concentration at which there may be a potentially significant impact to themarine environment.

Table 3.3: Dissolved Aromatic In-water Threshold Values Appl ied as Part of theModelling Study

Trigger Value for

Dissolved AromaticConcentrations fo r a 96-

hour LC50 (ppb)

Equivalent Dosage

of Dissolved Aromatics

(ppb.hrs)

Range of Sensitive SpeciesPotentially Impacted from Acute Exposure

PotentialLevel ofExposure

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


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The ZPI for entrained exposure was defined at 100–500 ppb as APASA (2013) suggest thisrange could serve as an acute lethal threshold to 95% and 50% of biota respectively. Although the ANZECC guidelines (2000) have the lowest trigger levels for total hydrocarbonsin water set at 10 ppb, a relatively long exposure time is required for these concentrations tobe significant. The threshold of 100 ppb was set here to indicate the zones where acuteexposure could potentially occur over shorter durations should the event occur.

Table 3.4: In-water (entrained) Threshold Values Applied as part of the ModellingStudy

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

3.2.3 Probability of Hydrocarbon Exposure

A probability of hydrocarbon exposure to the environment of greater than 10% has beenselected for the purposes of determining the extent of the ZPI for the Program. Theprobability 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

in the event of a well-blow out scenario due to the following:

♦ The ZPI represents a credible worst case scenario and the modelling output does notconsider any spill prevention, mitigation and response capabilities.

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

♦ The modelling output represents simulations of the same spill scenario under different,randomly sampled conditions that were based on inputs from extensive datasets;including local winds and currents (APASA 2013). The simulations were repeated aminimum of 50 times per season to ensure that the predicted transport and weathering ofthe hydrocarbon spill simulation were subject to a range of wind and current conditions;

including outliers such as cyclonic events.

3.2.4 Modelling resul ts

The modelling results presented in the following provide background information on how theZPIs were determined. Definition of the ZPI is provided in Section 3.2.1.

3.2.4.1 Marine Diesel Oil 6 Hour Surface Release Scenario

Results of the MDO scenario for the nearshore dredging fleet vessel collision scenario at thedetermined thresholds and probability identified:


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♦ Shoreline exposure is predicted to be likely at the Southern Group of Islands1 for all threeseasons (>50 %).

♦ Maximum shoreline exposure probability is 92 % for specific sections of the shorelines ofthe Southern Group of Islands in the winter season.

♦ Shoreline exposure is predicted likely at specific sections of the shorelines of the

Southern Group of Islands within 1 hour (absolute shortest time to contact) for all threeseasons.

♦ Potential low entrained exposure was predicted for all three seasons in the watersurrounding the spill location.

3.2.4.2 Heavy Fuel Oil 6 Hour Surface Release Scenario

Results of the HFO scenario for the offshore pipelay vessel collision scenario at thedetermined thresholds and probability identified:

♦ Shoreline exposure is predicted to be unlikely in any season, the probability of shorelinecontact is 5 % and less.

♦ In the unlikely event that shoreline exposure was to occur the absolute shortest time tocontact would be approximately 6 days to contact at specific sections of the shorelines ofthe Montebello Islands in the winter season.

♦ HFO is likely to break into small tar balls over time, the tar balls that are formed as aresult of the spill can be expected to wash up onto shorelines and/or sink as a result ofaccumulation of suspended sediments.

♦ Under all seasonal conditions, the modelling predicted no exposure to dissolved aromaticor entrained hydrocarbons of any meaningful level.

3.2.4.3 IAG-1E Well Blow-Out Scenario

Results of the well blow-out scenario for IAG – 1E at the determined thresholds andprobability identified:

♦ Shoreline exposure is not predicted to occur 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 (Table 3.5)

♦ The predicted minimum time before hydrocarbon exposure of any shoreline was358 hours (~15 days) under any conditions (Table 3.5)

♦ 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 sensitivecoastal environmental receptors including islands and the Ningaloo Coast

♦ Zones of moderate exposure to entrained hydrocarbon are predicted to occur in coastalwaters adjacent to the Montebello Islands, Barrow Island, Ningaloo Coast, SouthernGroup of Islands and Muiron Islands under all seasonal conditions.

1

Southern Group of Islands refers to: Thevenard Island, Serrurier Island, Bessier Island, Peak Island,Tent Island and the Rivoli Islands


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Table 3.5: Summary of shoreline contact probability and minimum t ime to shore –surface expression* of the spill

Location SeasonShoreline contact

probability(above 10 g/m

2)

Minimum time to shore(hours ) (above 10 g/m

2)

Marine Diesel Oil Scenario

Southern Group of

Islands

Summer 66% 1

Transitional 88% 1

Winter 92% 1

Middle Group of

Islands2

Summer42% 30

WA Mainland Summer 32% 14

Muiron Islands Winter 18% 44

Heavy Fuel Oil Scenario

N/A Summer - -

N/A Transitional - -

N/A Summer - -

IAG-1E Well Blow-Out Scenario

Montebello Island

Summer 16% 537

Transitional 14% 358

Barrow Island Summer 16% 859

* Note – shoreline contact probability and minimum time to shore for entrained hydrocarbonis likely to be similar to surface expressions of oil

2

Middle Group of Islands refers to Mangrove Islands, Great Sandy Island, North Sandy Island andMary Ann group of Islands


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4.0 POTENTIAL HYDROCARBON EFFECTS ONENVIRONMENTAL RECEPTORS

This section provides an overview of the potential effects from hydrocarbon exposure toenvironmental receptors within the EMBA. The purpose of this section is to provide

contextual information for each of the OPS and SCI plans. The monitoring techniquesproposed in each of the OPS and SCI plans consider chronic and acute effects based on thecharacteristics of MDO, HFO and condensate hydrocarbons for the Project.

4.1 Overview

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

♦ Oceanographic and meteorological conditions

♦ Hydrocarbon type.

4.2 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.

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

4.4 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 toxicitydepend on the toxic properties of the hydrocarbon (a combination of the hydrocarbon typeand weathering), and the concentration and dose that the organism receives.

4.5 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 the


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survival 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.

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 other

impacts 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.

4.5.1 Bioaccumulation

Bioaccumulation can be defined as the uptake of a contaminant by an organism from water

directly 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 ofhydrocarbon 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. However, the percentage of PAH present are significantlyhigher in HFO as compared to MDO and condensate.

4.5.2 Biomagnification

Biomagnification is defined simply as the magnification of concentrations of a contaminantover two or more trophic levels. One concern with bioaccumulation is that contaminated

organisms (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 bioaccumulation may cause restrictions on collectingshellfish or other items consumed by humans. However, PAH compounds do not usuallyreside in the tissue for long periods of time before they are depurated. Thus, biomagnificationis not usually a major concern with petroleum compounds originating from hydrocarbon spills(Hayes et al 1992).

4.6 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.

4.7 Receptor Specif ic Effects

4.7.1 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). The presence ofhydrocarbons can occur as (i) surface slicks, (ii) dispersed into the water column (commonlytermed entrained); or (iii) dissolved into the water column. Hydrocarbons in the water column

are small droplets (


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Entrained hydrocarbons are generally considered a short term phenomenon andhydrocarbons either become diluted within the water column; or return to the surface whenmixing energy (wave action) is reduced (Oceans Studies Board, 2003).

Circulation patterns play an important part in transporting hydrocarbon compounds whichwhen transported may result in contact with resources and sensitive receptors. Empirical

evidence has demonstrated that surface hydrocarbons move downwind about 3% of the windvelocity. In the presence of surface water currents, an additional movement at 100% of thecurrent velocity may also occur. Close to land, the strength and direction of any tidal currentsshould also be considered when predicting oil movement, whilst further out to sea thecontribution of other ocean currents predominate over the cyclic nature of tidal movement(International Tanker Owners Pollution Federation Limited 2011).

While the biomass of plankton in the North-West Marine Region is not high, there is arelatively high diversity of some planktonic species (Hallegraeff 1994). Oil slick episodeshave the possibility to induce mass mortality events in zooplankton and in copepods inparticular. Sub-lethal effects induced by the PAH water-soluble fraction are known to affectcopepod physiology, feeding and fecundity, which can lead onto abundance and diversityimpacts (Varela et al. 2006). It is also known that hydrocarbons affect copepodchemosensory abilities resulting in induced behaviour stresses and the subsequent feeding,mate seeking and predator avoidance adaptive responses (Barry 2000). Hydrocarbons areknown to have non-lethal effects on plankton and then bioaccumulate through the food chainto toxic levels in apex predators (Seuront 2010).

4.7.2 Seabed

Habitats considered to be at greatest risk to hydrocarbon contamination are located withinthe coastal zone. However, in the event of a subsurface spill, or where dispersants are usedin response activities, habitats in deeper waters may be at risk of exposure and should alsobe considered. The extent to which a spill affect seabed habitats in any area depends on a

complex suite of interacting physical, chemical and biological factors. For all marine seabedprimary producer habitats, mortality can result from hydrocarbon covering photoreceptorsand pores for oxygen exchange (NOPSEMA 2012). All other organisms can still be wholly orpartially smothered by hydrocarbon which can inhibit normal breathing, feeding andreproducing activities (NOPSEMA 2012).

4.7.2.1 Deep-water Hard Substrate

Impacts on submerged banks and shoals are expected to be similar to those described forother seabed habitats from a hydrocarbon spill. Because of the depth of some of theregionally significant habitats (e.g. escarpments along the North West Shelf), these habitatsare considered to be at a lower risk to hydrocarbon contamination. However, these habitats

support sizable populations of commercially important bottom feeding species as well asresident populations of protected marine species and there is a need to consider the effectsof oil on deep-water hard substrates. Many previous assessments conducted following majoroil spills have shown benthic distribution patterns reflective of oceanographic conditions,rather than exhibiting toxicity effects (Feder & Blanchard, 1998). However, the DeepwaterHorizon spill showed evidence of impaired benthic condition within the near-field zone (withinabout 3 km of the wellhead), as well as identification of stressed benthic communities out toabout 15 km to the south-west. Hydrocarbon stress in deep-water corals was identified asvarying degrees of tissue loss, sclerite enlargement, and excess mucous production,bleaching and covering of a brown flocculent material.

4.7.2.2 Subtidal Pavement

Few studies have been made on hydrocarbon spill impacts on epibenthic communities orrocky subtidal habitats (Law et al. 2011). The lack of substrate that could retain a persistent


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hydrocarbon contamination means that any impacts are only likely to be due to the acuteeffects of the dispersed hydrocarbon. Small crustacean (i.e. small crabs), some bivalves andsurface grazing snails have been identified as the main casualties in hydrocarbon spills(Gesteria and Dauvin 2000, Kingston et al. 1997).

Studies on sub lethal effects on subtidal pavement species are limited. It may be assumed

that the effects that have been described for intertidal species, that bioaccumulatehydrocarbon in the water column, may also be relevant to shallow subtidal species (e.g. Reidand MacFarlane 2003, Pendoley 1992). There have been very few studies of the effects ofcleanup activities on subtidal rock habitats. Potential effects may occur from increasedconcentrations of dispersed hydrocarbon in water following dispersant spraying or intertidalflushing operations.

4.7.2.3 Soft-subst rate communi ties

Dispersed hydrocarbons in water and hydrocarbon bound to shoreline sediments can makeits way to the seabed and contaminate subtidal sediments. High concentrations of dispersedhydrocarbon can affect sediment epifauna and filter feeders without becoming bound within

the sediment (Law et al. 2011). Some groups of sediment fauna are more sensitive tohydrocarbon that others. Amphipods, filter-feeding bivalves and burrowing urchins have beenidentified as main casualties at a number of hydrocarbon spills (e.g. Dauvin 1998, Mooreet al. 1987). Studies of impacts from hydrocarbon spills on subtidal sediment meiofauna havenot shown a consistent response (Moore et al. 1987), although reductions in abundance ordiversity are likely.

4.7.2.4 Coral Reefs

Spilled hydrocarbons can adversely affect subtidal coral communities through the dispersalof hydrocarbon into the shallow subtidal areas or by dissolution of toxic hydrocarbons into thewater column. Corals may be killed by exposure to hydrocarbon and there are differences in

the tolerance by coral species. Branching corals appear to be among the most susceptible,whereas massive corals are more tolerant.

There are three primary modes of exposure for coral reefs in oil spills:

1) Direct oil contact is possible when surface oil is deposited on intertidal corals that livenear the surface of the water and become exposed with the tides.

2) Rough seas and light, soluble oil can combine to mix the oil into the water below thesurface, where it can impact corals. Corals are exposed to less oil beneath the watersurface, but the lighter oil components that mix easily are often the most toxic.

3) Subsurface oiling can occur when heavy oils weather, or mix with sediment material.This increases the density of the oil to the point where it may actually sink, potentiallysmothering corals.

Direct contact with spilled oil can lead to coral death, but depends on coral species, growthform, life stage, and type/duration of oil exposure. Longer exposure to lower levels of oil maykill corals, as well as shorter exposure to higher concentrations. Death may not beimmediate, but rather take place long after the exposure has ended. Notably, only few coralreefs are routinely exposed during normal low tides and as such both surface exposure andexposures to entrained and/or dissolved hydrocarbons must be considered.

Biological toxic impacts to the associated community can be severe. Smothering and

contamination leads to mortality or shifts in density of the rich coral reef fauna and flora, andassociated marine predators. Hydrocarbon and dispersant may affect coral reproduction


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through 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.

Cleanup 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).

4.7.2.5 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 Island

following 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 intertidalmacroalgae 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. Thus it is apparent that the effects to macroalgaeare related to direct contact with oil and residence time.

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). This

was 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 beenproposed (Velasquez et al 1973) and documented (McCauley, 1966; Straughan, 1970, 1972;Straughan & Abbott, 1971; Cooper & Wilhm, 1975) to result from chronic exposure to oil orrefinery effluents. Conversely, there are numerous reports of algal proliferation followingcontamination (Perkins, 1968).

4.7.2.6 Seagrass Communities

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 identifiedinclude 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).


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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.

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.

4.7.2.7 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 (IPIECA2011).

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 2011).

4.7.3 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 by

the 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 cleanup operations.

The potential impacts from hydrocarbons on each of the four coastal shoreline habitats aresummarized below. The operational program summary of potential impacts fromhydrocarbons on shorelines concentrates on the behaviour of hydrocarbons in an intertidalenvironment used to inform response strategies.


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Wheatstone Oil Spill Operational and Scientific Monitoring Program