coastal processes monitoring and management plan · 2018-03-01 · ansia . ashburton north...

© Chevron Australia Pty Ltd

Document No: WS0-0000-HES-PLN-CVX-000-00070-000 Revision: 3

Revision Date: 29/9/15

IP Security: Public

Wheatstone Project Coastal Processes Monitoring and Management Plan

Wheatstone Project Document No: WS0-0000-HES-PLN-CVX-000-00070-000

Coastal Processes Monitoring and Management Plan Revision: 3 Revision Date: 29/09/2015

© Chevron Australia Pty Ltd Public Printed Date: 22/10/2015 Uncontrolled when printed

TABLE OF CONTENTS

ACRONYMS, ABBREVIATIONS AND TERMINOLOGY ....................................................... 5 1.0 BACKGROUND ............................................................................................................ 9

1.1 Project Overview .................................................................................................. 9 1.2 Proponent ............................................................................................................ 9 1.3 Objectives ............................................................................................................ 9 1.4 Scope ................................................................................................................. 12 1.5 Environmental Approvals ................................................................................... 12 1.6 Stakeholder Consultation and Public Availability ................................................ 16 1.7 Endorsement by an Independent Coastal Engineering Expert ............................ 16 1.8 Review, Approval and Revision of this Plan ....................................................... 16

2.0 PROJECT DESCRIPTION .......................................................................................... 17 2.1 Materials Offloading Facility ............................................................................... 17 2.2 Product Loading Facility ..................................................................................... 17 2.3 Shipping Channel ............................................................................................... 17 2.4 Dredging and Dredge Spoil Disposal .................................................................. 17

3.0 EXISTING ENVIRONMENT ........................................................................................ 19 3.1 Metocean Conditions.......................................................................................... 19 3.2 Geology & Geomorphology ................................................................................ 20 3.3 Shoreline Morphology, Tidal Creeks & Lagoons ................................................. 20

3.3.1 Ashburton Delta .................................................................................... 20 3.3.2 Hooley Creek ........................................................................................ 25 3.3.3 The Eastern Beaches ........................................................................... 26 3.3.4 Onslow Town Beach & Seawall ............................................................ 26

3.4 Coastal processes .............................................................................................. 27 3.5 European Heritage ............................................................................................. 30

4.0 RISK ASSESSMENT .................................................................................................. 31 4.1 Littoral Sediment Transport ................................................................................ 31 4.2 Shoreline Morphology (Erosion Trend) ............................................................... 31 4.3 Tidal Creeks and Lagoons ................................................................................. 32 4.4 Recreational Amenity ......................................................................................... 32 4.5 Onslow Seawall .................................................................................................. 32 4.6 Heritage Sites .................................................................................................... 33 4.7 Summary ............................................................................................................ 33

5.0 MONITORING ............................................................................................................. 34 5.1 Overview ............................................................................................................ 34 5.2 Routine Monitoring ............................................................................................. 35

5.2.1 Site Inspection ...................................................................................... 35 5.2.2 Geomorphic Inspection ......................................................................... 35 5.2.3 Topographic Survey ............................................................................. 35 5.2.4 Nearshore Hydrographic Survey ........................................................... 35 5.2.5 Hooley Creek Survey ............................................................................ 36 5.2.6 Community Consultation ....................................................................... 36 5.2.7 Mangrove Monitoring ............................................................................ 36

5.3 Triggered Monitoring .......................................................................................... 40 5.3.1 Triggered Topographic/Hydrographic Survey ....................................... 40




5.3.2 Aerial/Satellite Imagery Capture ........................................................... 40 5.3.3 Recreational Amenity Inspection .......................................................... 40 5.3.4 Seawall Condition Assessment ............................................................. 40 5.3.5 Heritage Site Assessment .................................................................... 40

5.4 Other Monitoring ................................................................................................ 40 5.4.1 Bypass Monitoring ................................................................................ 41 5.4.2 Contingency Monitoring ........................................................................ 41

5.5 Summary ............................................................................................................ 41 6.0 ENVIRONMENTAL MANAGEMENT TRIGGERS & ACTIONS................................... 42

6.1 Littoral Sediment Transport ................................................................................ 42 6.2 Shoreline Morphology (Erosion Trend) ............................................................... 45 6.3 Tidal Creeks and Lagoons ................................................................................. 47 6.4 Recreational Amenity ......................................................................................... 48 6.5 Onslow Seawall .................................................................................................. 48 6.6 Heritage Sites .................................................................................................... 49 6.7 Contingency Management Actions ..................................................................... 50

7.0 REPORTING ............................................................................................................... 51 7.1 Annual Compliance Reporting ............................................................................ 51 7.2 Non-compliance Reporting ................................................................................. 51 7.3 Incident and Other Reporting ............................................................................. 51

8.0 REFERENCES ............................................................................................................ 52

TABLES

Table 1-1: Requirements of WA Ministerial Statement No. 873 relevant to this Plan ............ 13 Table 1-2: Requirements of Commonwealth Ministerial Conditions: EPBC 2008/4469

relevant to this Plan ......................................................................................... 15 Table 3-1: Estimated Baseline Net Littoral Transport Rates................................................. 28 Table 5-1: Monitoring and Relevant Environmental Receptors ............................................. 34 Table 5-2: Summary of Coastal Process Monitoring Methods and Frequencies ................... 41 Table 6-1 Management Triggers and Actions relating to Littoral Sediment Transport .......... 42 Table 6-2 Ambient and Recovery Targets for Shoreline Morphology ................................... 45 Table 6-3 Management Triggers and Actions relating to Shoreline Morphology of the

study area ........................................................................................................ 46 Table 6-4 Management Triggers and Actions relating to Hooley Creek ............................... 47 Table 6-5 Management Triggers and Actions relating to Ashburton Delta ........................... 48 Table 6-7 Management Triggers and Actions relating to the Onslow Seawall ...................... 49 Table 6-8 Management Triggers and Actions relating to Heritage Sites .............................. 49

FIGURES

Figure 1-1: Location of the Wheatstone Project Infrastructure .............................................. 10 Figure 1-2: Key Coastal Features and Relevant Project Facilities ........................................ 11 Figure 2-1: Nearshore Marine Facilities ................................................................................ 18 Figure 3-1: Components of the Ashburton Delta ................................................................... 21 Figure 3-2: Entrance Point looking east (April 2012) ............................................................. 22 Figure 3-3: Entrance Point looking west toward the Project site (April 2012) ........................ 22




Figure 3-4: Ashburton Eastern Delta (1963-2009) ................................................................ 24 Figure 3-5: Hooley Creek Entrance Bar and Creek System (2009) ....................................... 25 Figure 3-6: Hooley Creek Entrance Bar (1963-2009) ............................................................ 26 Figure 3-7: Littoral Transport and Net Erosion and Accretion Rates .................................... 29 Figure 3-8: Recorded Coastal European Heritage Sites Adjacent to the Project ................... 30 Figure 5-1: Topographic and Hydrographic Survey Zones. .................................................. 37 Figure 5-2: Cross-section Channel-Throat Monitoring Locations .......................................... 38 Figure 5-3: Links between the CPMMP and the MAMTCPMP .............................................. 39 Figure 6-1: Sand Bypassing Extraction and Disposal Areas ................................................. 43 Figure 6-2: Indicative Beach Nourishment Process ............................................................. 44

APPENDICES

APPENDIX A CONSERVATION SIGNIFICANT SPECIES APPENDIX B ACTION TABLE




ACRONYMS, ABBREVIATIONS AND TERMINOLOGY

Term Definition

AHD Australian Height Datum – see m AHD

ANSIA Ashburton North Strategic Industrial Area

Arcuate beach A shore with an arc-shaped, concave plan form, often comprised of a sandy beach between two erosion resistant features which provide structural control (e.g. rocky headlands)

Bitterns Concentrated seawater, formed as a waste product of solar salt operations.

CEO Chief Executive Officer

Chenier A discrete, elongated, vegetated marine beach ridge comprised of sand or shell which is stranded on a coastal mudflat or marsh, roughly parallel to a prograding shoreline. When cheniers are distributed across a wide plain, that feature is called a 'chenier plain'

Chenier spit A chenier that is joined to the mainland at one end but not the other, thus forming a spit

Chevron Chevron Australia Pty Ltd

Coast A strip of land of indefinite width that extends from the shoreline inland to the first major change in terrain features.

Coastal Processes Collective term covering the action of natural forces on the shoreline, and nearshore seabed

Construction Defined as the construction and commissioning of a Facility including any excavation and/or dredging but excludes temporary, minor, preliminary and investigatory works, geotechnical, geophysical, biological and cultural heritage surveys, staging works, baseline surveys, monitoring, technology trials, and works consented to by OEPA.

CPMMP Coastal Processes Monitoring and Management Plan

CRG Community Reference Group

Cth Commonwealth

Cyclone Event For this report, a cyclone event is defined as the passage of a tropical cyclone which may plausibly have affected coastal stability through the generation of high waves, water levels or currents. As the effect of a tropical cyclone is strongly influenced by system intensity, path and duration, cyclone events have been simply defined as - a Category 4 or 5 tropical cyclone passing within 300km of Onslow and

causing onshore winds (from NW through NE); - a Category 1, 2 or 3 tropical cyclone within 100km of Onslow and causing

onshore winds;

Delta A landform comprised of branched or interleaved channels and alluvial deposits occurring at the mouth of a river due to high riverine sediment supply

Domgas Domestic gas

Downdrift The direction of predominant movement of littoral materials

DOTE Department of The Environment -formerly Department of Sustainability, Environment, Water, Population and Communities (Cth)




Term Definition

EIS/ERMP Draft and final Environmental Impact Statement/Environmental Review and Management Programme

EP Act Environmental Protection Act 1986

EPBC Act (Cth) Environment 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, with variations to EPBC 2008/4469 conditions 44, 45, 55, 56 and 66 made pursuant to section 143 of the EPBC Act, as amended from time to time.

Erosion Trend An average shoreward movement of the coastal profile between MSL and HAT, when compared against the corresponding profile measured three years previously, unless the beaches have experienced more than 5m erosion during a tropical cyclone. In such an event, the trend shall be established by separately considering periods before and after the cyclone.

Fluvial Processes associated with rivers and streams and the deposits and landforms created by them

ha hectare(s)

HAT Highest Astronomical Tide

HES Health, Environment and Safety

Km kilometre(s)

LiDAR Light Detection and Ranging

Littoral sediment transport

The movement of sediment in the littoral zone by waves and currents (parallel movement = alongshore drift; perpendicular movement = cross-shore transport)

Littoral Zone A general term for the coastal zone influenced by wave action.

LNG Liquefied Natural Gas

m metre(s)

Mm3 Million cubic metres

m AHD Metres above Australian Height Datum (approximately the height above mean sea level)

MAMTCPMP Mangrove, Algal Mat and Tidal Creek Protection Management Plan

Management Actions

Management activities, measures, actions, strategies, undertakings or directives which may:

1. Correct or improve upon management actions which have been ineffective 2. Attenuate, minimise, mitigate impacts the Proposal would otherwise have

on the environment if the action were not taken or 3. Ensure compliance with conditions, or any monitoring or management

triggers established by those conditions.

Metocean The combination and interaction of meteorological and oceanographic factors (e.g. wind, waves, and currents)

MOF Materials Offloading Facility

MSL Mean Sea Level




Term Definition

MTPA Million tonnes per annum

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 by MS 903, MS 922, MS 931 and Attachments 1 to 4 and amended from time to time.

Nearshore Marine Facilities

Includes the Shipping channel, PLF, Materials MOF, Dredge spoil disposal site A and discharge lines

NES National Environmental Significance

OEPA Office of the Environmental Protection Authority

Offshore Marine habitat beyond the 20 m contour from the shoreline

Operations For the purposes of this Plan operations is taken to mean operation of the nearshore marine facilities by the Proponent only.

Other Marine Facilities

Includes Dredging, Trunkline, Trunkline shore crossing and Offshore Accommodation Vessels.

p.a. per annum

(The) Plan Coastal Processes Monitoring and Management Plan

PLF Product Loading Facility

Port Facilities Any facilities under the operational control of the Dampier [now Pilbara] Port Authority as defined in Ministerial Statement 873,

PPA Pilbara Ports Authority (includes the former Dampier Port Authority)

Practicable Means as 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)

Prevailing The direction from which the wind / sediments most frequently originate

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

Proponent Chevron Australia Pty Ltd

RORO Roll-On, Roll-Off [vessels]

RTK Real Time Kinematic

Sediment Sinks Point or area at which sediment is irretrievably lost from a coastal cell, such as an estuary, or a deep channel in the seabed, under non-cyclonic conditions, without mechanical intervention such as dredging or sand-bypassing operations.

Shoal A detached mound of any material (except rock or coral), typically composed of sand, silt or small pebbles that has a relatively shallow depth. Similar continental or insular shelf features of greater depths are usually termed banks. Shoals may develop from a detached portion of a deltaic or tidal spit

Significant Erosion/Accretion Event

A notable change in the geomorphology of a key coastal feature which is greater than would otherwise be expected under non-cyclonic conditions, derived from baseline and monitoring data and which presents a risk to the maintenance of target values. A significant erosion/accretion event may include a notable decrease in spit or beach widths; the appearance of an extensive erosion scarp(s); or a notable constriction or closure of tidal creek/lagoon entrance.




Term Definition

Spit A small point of land or a narrow shoal projecting into a body of water from the shore

Surge The water level above normal expected tide levels for that point in time, usually due to a combination of pressure, wind and wave setup during a storm or cyclone

Trunkline One subsea partially buried pipeline to the shore crossing

Trunkline shore crossing

Up to 6 tunnels installed by micro-tunnelling technique up to 1400 m long

Updrift The direction opposite to that of the predominant movement of littoral sediments

WA Western Australia




1.0 BACKGROUND

1.1 Project Overview Chevron Australia Pty Ltd (Chevron) is constructing and will operate a multi-train Liquefied Natural Gas (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 located offshore in the West Carnarvon Basin. Ashburton North Strategic Industrial Area (ANSIA) is the approved site for the LNG and Domgas plants.

The Project requires installation of gas gathering, export and processing facilities in Commonwealth and State waters and on land. The initial Project will produce gas from Production Licences WA-46-L, WA-47-L, and WA-48-L, 145 km offshore from the mainland, approximately 100 km north of Barrow Island and 225 km north of Onslow, and will also process gas from Production Licence WA-49-L operated by Woodside Petroleum Limited. Figure 1-1 shows the location of the Project.

The ANSIA is located approximately 12 km south-west of Onslow along the Pilbara coast within 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). Environmental approval was granted for a 25 MTPA plant to allow for the expected further expansions. The Domgas plant will be a separate but co-located facility and will form part of the Project. The Domgas plant will tie-in to the existing Dampier-to-Bunbury Natural Gas Pipeline infrastructure via third party DBP Development Group Pty Ltd Domgas pipeline. Figure 1-2 shows key coastal features and relevant project facilities.

1.2 Proponent Chevron is the proponent and the company taking the action for the Project on behalf of its joint venture participants Woodside Petroleum Limited, PE Wheatstone Pty Ltd a company part-owned by Tokyo Electric Power Company, Kuwait Foreign Petroleum Exploration Company and Kyushu Electric Power Company.

1.3 Objectives The Coastal Processes Monitoring and Management Plan (the Plan) establishes procedures which provide for the management and monitoring of Project attributable environmental impacts consistent with the requirements of Condition 9 in WA Ministerial Statement 873 (MS 873) and Condition 32 in the Commonwealth Ministerial Approval (EPBC 2008/4469). The objectives of the Plan are to:

♦ Minimise change to littoral sediment transport ♦ Minimise an erosion trend under non-cyclonic conditions in the position of the mean sea

level shoreline and dune vegetation line between the nearshore marine facilities and Beadon Creek

♦ Maintain the functionality of Hooley Creek ♦ Maintain the functionality of the Ashburton Delta and avoid destabilisation of the chenier

that impounds the coastal lagoon east of Entrance Point ♦ Minimise the impacts on the recreational value of beaches between the nearshore marine

facilities and Beadon Creek ♦ Minimise the reduction in the integrity and performance of the Onslow seawall ♦ Minimise the reduction in the integrity and values of heritage sites between the Ashburton

Delta and Beadon Creek




♦ Protect habitat for listed species, including sawfish species, from the changes to coastal process (Conservation Significant Species relevant to the Plan are listed in Appendix A).

Figure 1-1: Location of the Wheatstone Project Infrastructure




Figure 1-2: Key Coastal Features and Relevant Project Facilities




1.4 Scope The Plan has been prepared to address potential impacts to coastal processes associated with the Project’s nearshore marine facilities, during construction and prior to operational control of the ‘Port Facilities’ by Pilbara Ports Authority (PPA). It details the environmental management and monitoring measures to be implemented in order to manage coastal processes adjacent to the Project. The nearshore marine facilities and construction activities which are relevant to the Plan are detailed in Section 2.0.

When implemented, the Plan will provide Chevron the information required in order to identify and manage coastal process impacts attributable to the Project following construction of all relevant nearshore marine facilities. This Plan does not apply to the Port Facilities once under the operational control of the PPA.

1.5 Environmental Approvals The Project was assessed through an Environmental Impact Statement / Environmental Review and Management Program (EIS/ERMP) assessment process under the WA Environmental Protection Act 1986 and the Commonwealth Environment Protection and Biodiversity Conservation Act 1999.

The Project was approved by the WA Minister for Environment; Water on 30 August 2011 by way of MS 873 and as amended by Ministerial Statement No.903, Ministerial Statement No.922, Ministerial Statement No.931 and Attachments 1 to 4. The Commonwealth Minister for Sustainability, Environment, Water, Population and Communities approved the Project on 22 September 2011 (EPBC 2008/4469) with variations to EPBC 2008/4469 conditions 44, 45, 55, 56 and 66 made pursuant to section 143 of the EPBC Act. Other amendments may be made from time to time and if so will be reflected in the next revision of this Plan.

The sections in this Plan which are noted to meet MS 873 are noted in Table 1-1.

The sections in this Plan which are noted (in Table 1-2) to meet the conditions of EPBC 2008/4469 shall be read and interpreted as only requiring implementation of EPBC 2008/4469 for managing the impacts of Project-attributable changes to coastal processes on the EPBC Act listed species noted in Appendix A. The implementation of matters required only to meet the requirements of MS 873 are not the subject of EPBC 2008/4469. Similarly, the matters required to be implemented only to meet the requirements of EPBC 2008/4469, only apply to matters of National Environmental Significance (NES) and are not the subject of MS 873.

Wheatstone Project Document No: WS0-0000-HES-PLN-CVX-000-00070-000 Coastal Processes Monitoring and Management Plan Revision: 3 Revision Date: 29/09/2015


Table 1-1: Requirements of WA Ministerial Statement No. 873 relevant to this Plan

No. Condition Section

9-1 The Proponent shall ensure that construction and operation of the nearshore marine facilities (as defined in Schedule 1) achieve the following outcomes as far as is practicable as measured under the Coastal Processes Monitoring and Management Plan:

the Plan

i minimise change to littoral sediment transport; 4.1, 6.1

ii minimise an erosion trend under non-cyclonic conditions in the position of the mean sea level shoreline and dune vegetation line between the nearshore marine facilities and Beadon Creek;

4.2, 6.2

iii maintain the functionality of Hooley Creek; 4.3, 5.2.5, 5.4, 6.3

iv maintain the functionality of the Ashburton Delta and avoid destabilisation of the chenier that impounds the coastal lagoon east of Entrance Point;

4.3, 6.3

v minimise the impacts on the recreational value of beaches between the nearshore marine facilities and Beadon Creek; 4.4, 5.3.3, 6.4

vi minimise the reduction in the integrity and performance of the Onslow seawall; and 4.5, 5.3.4, 6.5

vii minimise the reduction in the integrity and values of heritage sites between the Ashburton Delta and Beadon Creek. 4.6, 5.3.5, 6.6

9-2 Prior to construction of the nearshore marine facilities (as defined in Schedule 1), unless otherwise approved by the CEO, the Proponent shall develop a Coastal Processes Monitoring and Management Plan to be approved by the CEO. The Plan shall include:

i site inspection of beach, entrance bar and seawall condition between the Ashburton Delta and Beadon Creek; 5.2.1, 5.2.2, 5.3.4

ii beach, chenier and spit/entrance bar width using a combination of topographic surveys and aerial photography/satellite imagery;

5.2.3, 5.3.1, 5.3.2, 5.4




iii beach profile using on-ground photography; 5.2.1, 5.4

iv mangrove habitat monitoring; [see Note] MAMTCPMP

v hydrographic survey of the nearshore area; 5.2.4, 5.4.2

vi community liaison strategy to obtain feedback on impacts on recreational values; 5.2.6

vii site inspection of heritage locations to assess the condition and potential threats to European heritage locations; 5.3.5

viii a table showing the type of monitoring and monitoring frequency for each of the coastal features to be protected under condition 9-1;

5.5

ix management triggers relevant to achieving the outcomes specified in condition 9-1; 6.0

x management actions that will be implemented in the event that management triggers are likely to be exceeded. 6.0

9-3A The Proponent shall provide relevant stakeholders with a draft copy of the Coastal Processes Monitoring and Management Plan required under condition 9-2, and provide those stakeholders a reasonable opportunity to comment on the plan before it is submitted to the CEO for approval under condition 9-2.

1.6

9-4 The Proponent shall report any non-achievement of the management trigger referred to in condition 9-2, along with measures taken and/or proposed to be taken, and strategies to be implemented in response to the non-achievement, to the CEO within 21 days of the non-achievement being identified.

7.0

9-5 The Proponent shall make the Plan required under condition 9-2 publically available in a manner approved by the CEO 1.6

NOTE: Mangrove monitoring for the Wheatstone project is detailed in the Wheatstone Mangrove, Algal Mat and tidal Creek Protection Management Plan [WS0-0000-HES-PLN-CVX-000-00066-000]



Table 1-2: Requirements of Commonwealth Ministerial Conditions: EPBC 2008/4469 relevant to this Plan


32. A Coastal Processes Monitoring and Management Plan (CPMMP), to protect habitat for listed species, including sawfish species, from changes to Coastal Processes. The program should include the following:

This Plan

a. An appropriate monitoring plan and sites to be used to collect baseline data and monitor changes to the functionality of the Ashburton River Delta, including the chenier that impounds the coastal lagoon east of Entrance Point, Hooley Creek and other tidal creeks, which may be inhabited by sawfish, during and after construction;

5.0

b. Appropriate trigger levels and management actions to ensure no impacts to the functionality of sawfish habitat at the Ashburton River Delta, Hooley Creek, and other tidal creeks containing potential habitat for the sawfish.

6.0

33. The CPMMP must be reviewed and endorsed by an independent coastal engineering expert prior to submission of CPMMP to the Minister for approval.

1.7




1.6 Stakeholder Consultation and Public Availability

Chevron undertook consultation with the following relevant stakeholders, with comments received taken into consideration during the initial development of the Plan:

♦ Shire of Ashburton. ♦ Onslow Salt ♦ Dampier Port Authority (now Pilbara Port Authority)

MS 873 Condition 9-3A (Table 1-1) requires that Chevron provides an opportunity for the following relevant stakeholders to comment during the initial development of the Plan, as agreed with the Office of the Environment Protection Authority (OEPA):

♦ WA Office of the Environment Protection Authority – Marine Branch ♦ WA Department of Environment and Conservation ♦ WA Department of Transport ♦ The Wilderness Society ♦ Cape Conservation Group.

The approved Plan will be made publicly available on Chevron’s website in a manner approved by the CEO of the OEPA (MS 873 Condition 9-5).

1.7 Endorsement by an Independent Coastal Engineering Expert As required by Condition 33 (EPBC 2008/4469) this revision of the Plan has been reviewed and endorsed by an independent coastal engineering expert prior to submission to the Minister for approval. A copy of all the recommendations made by the independent coastal engineering expert and an explanation of how these recommendations have been implemented, or an explanation of why Chevron does not propose to implement certain recommendations has been provided to the Minister.

1.8 Review, Approval and Revision of this Plan Chevron is committed to conducting activities in an environmentally responsible manner and aims to implement reviews of its environmental management actions as part of a programme of continuous improvement. This commitment to continuous improvement means that Chevron may review the Plan to address matters such as the overall effectiveness, environmental performance, changes in environmental risks and changes in business conditions on an as needed basis (e.g. in response to new information). Consistent with this commitment, this revision of the plan has been updated based on a review undertaken after the completion of construction of all relevant nearshore facilities. The review has resulted in a revision to the project descriptions, existing environment, risk assessment, monitoring program and management triggers/actions within the Plan.

MS 873 Condition 24-1 requires that Chevron may only implement an amendment to this Plan from the date of the amendment. Significant amendments may only be implemented from the date of approval of the amendment by the CEO Significant amendments are those amendments which alter the obligations of Chevron that is, they are not minor or administrative.

EPBC 2008/4469 Conditions 5 and 6 require that Chevron may only implement the Project otherwise than in accordance with the provisions of this Plan which regulate the matters of NES relevant to this Plan from the date of approval of any variation to this Plan by the Commonwealth Minister.




2.0 PROJECT DESCRIPTION

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

2.1 Materials Offloading Facility The Materials Offloading Facility (MOF) has been completed and provides an offloading facility for heavy-lift ships, Roll-on, Roll-off (RORO) vessels, heavy-lift carriers and barges all 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. The MOF provides a base for marine operations craft such as Pilot boat, tugs, security and line handling vessels. Breakwater(s) at the MOF entrance, extending from the shoreline, create a calm operating environment inside the basin during normal conditions and provide a safe haven for vessels to berth during a cyclone.

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 up to two LNG tankers and one condensate tanker. It includes a jetty and mooring dolphins. The PLF is likely to carry a roadway and a double pipe rack from the shore to the PLF operations platform from where loading operations will be controlled. The pipe rack will accommodate LNG and condensate loading lines, an LNG vapour return line, fire water pipework and communications cabling. See Figure 2-1.

2.3 Shipping Channel The shipping channel extends approximately 18 km across the inner continental shelf passing Saladin Shoal, Hastings Shoal, Gorgon Patch and Weeks Shoal, and ending around 5 km east of Thevenard Island (see Figure 1-2). The channel will be approximately 260 m wide and 13.5 m deep allowing LNG carriers and condensate tankers access to the PLF and non-trading vessels access to the MOF. The navigation channel and turning basin (see Figure 2-1) will enable the LNG and condensate carriers to safely access and depart berths at the PLF.

2.4 Dredging and Dredge Spoil Disposal Dredging to create the MOF and approach channel and install the trunkline has been completed. In total, the dredging of the shipping channel, turning basin, tanker berths and MOF generated approximately 25.6 Mm3 of dredge spoil and up to approximately 1.6 Mm3 dredge spoil for the trunkline. The bulk of the sediment has been placed at dredge spoil placement site C with smaller volumes placed at sites D and E (Figure 1-2).




Figure 2-1: Nearshore Marine Facilities




3.0 EXISTING ENVIRONMENT

Characterisation of the coastal environment in the vicinity of the Project has been undertaken as part of the environmental impact assessment, as described in the Wheatstone EIS/ERMP and Damara (2010). In addition, two baseline topographic surveys were undertaken in October 2012 and April 2013, prior to the commencement of construction of the MOF breakwaters. A nearshore hydrographic baseline survey was undertaken in April 2013. These surveys, together with the characterisation undertaken as part of the Wheatstone EIS/ERMP provide a basis for qualitative and quantitative assessments of changes to coastal processes, including potential Project-attributable impacts.

For the purposes of this Plan, the study area is defined as the shoreline and nearshore areas between False Entrance on the western edge of the Ashburton Delta complex and Beadon Creek to the east of the town of Onslow. The shoreline is defined as the land potentially affected by marine processes, extending landward from the mean sea level contour and the permanent vegetation line. The nearshore is defined as the subtidal area adjacent to the shoreline, where the majority of littoral sediment transport takes place, and for monitoring purposes extends seaward from the mean sea level contour to -2.5 m AHD.

3.1 Metocean Conditions The Onslow region experiences an arid, subtropical climate, with distinct wet-dry seasonality. The summer wet season is characterised by hot and humid weather and a south-south-westerly sea breeze system. By contrast, the winter dry season is cooler and drier, with a weaker sea breeze system and more frequent easterly winds.

Tropical cyclones occur during the summer months (typically November to April), causing short periods of intense winds and rainfall. Cyclones typically pass to the north-west of the study area, often tracking parallel to the North-West Shelf. Extreme metocean conditions during tropical cyclones have the potential to dramatically alter the coastal state, with such changes potentially including erosion of the beach and dune profile or overtopping of highly dynamic spits during elevated wind and wave conditions.

The mean annual rainfall, observed at Onslow Airport, is 312 mm with rain typically falling during tropical cyclones, summer thunderstorms and winter storms. Rainfall events can result in highly variable runoff and flow through rivers and creeks in the region. High flow events have the potential to dramatically change the morphology of tidal creeks, overflow channels, mudflats and shoreline entrance regimes through scour and sediment transport processes.

The significant change from outside Thevenard and Bessieres Islands through to the nearshore region indicates the degree of sheltering between the two locations due to the effects of friction, diffraction and refraction. Nearshore, the boundary effect of the coast causes all currents to run nearly shore-parallel.

The key water level processes affecting Onslow include tides, cyclonic surges, seasonal variation and inter-annual mean sea level variations. The spring tide range is 1.9 m, and cyclonic storm surges of up to 0.8 m have been recorded in Beadon Creek, with anecdotal or inferred evidence of much higher events, particularly on the exposed coast. The most extreme elevated water levels are generally associated with onshore wind events caused by tropical cyclones passing to the west of Onslow. However, more frequent moderate surges may also be generated by tropical cyclones travelling parallel to the coast, and this is likely to be a result of shelf wave formation. The seasonal timing of tidal and mean sea level peaks provides increased potential for extreme water level events to occur as a result of late season tropical cyclones in March or April.




3.2 Geology & Geomorphology The characteristic coastal dynamics of the Pilbara, with rocky features providing strong structural control over shoreline position (Semeniuk 1996), are appropriately interpreted using sediment cell concepts in which sediment sources, transport pathways, and sediment sinks (loss areas) are identified.

The hard-rock geology between Tubridgi Point and Cape Preston provides a fixed framework for the shoreface to the 50 m isobath. At least two deltaic complexes comprised of coalescing limestone structures contribute to the geologic framework; one crossed by the Ashburton River, the other forming the undulating pavement supporting the catchments of Hooley Creek and Four Mile Creek. The limestone structures include lithified forms of antecedent shorelines, beach ramps, fringing coral reefs, rock platforms, paleo-river channels, overbank basins and topographic rises.

Limestone occurs as discontinuous outcrops along the coast between Casugrina Point and Beadon Creek (Figure 1-2). The outcrops include low aeolianite bluffs at the seaward margin off the frontal dunes; platform and bluff along the southern shore of the lagoon near the Project site and in the vicinity of Four Mile Creek, where it joins a beach-rock ramp sloping seaward onto a subtidal pavement. These outcrops influence coastal processes in a number of ways. Firstly, the low bluff along the shore of the lagoon inhibits, but does not prevent development of a sandy beach along the shore. Second, breaks between rock outcrops are areas of potential coastal instability, i.e. areas where erosion is most likely to occur under prolonged storm conditions or reduced sediment availability. Third, away from Casugrina Point, the updrift, eastern margin of breaks between outcrops commonly have frontal dunes which are higher than those landward of the adjacent outcrops.

The western, (Ashburton) compartment is a single sediment cell extending over 70 km from approximately Tubridgi Point to Coolgra Point. Its distinguishing geomorphological features include the active delta and tidal creeks of the Ashburton River, long sandy beaches and dunes as well as island chains running approximately parallel to the shore. Functioning of the western (Ashburton) compartment as a sediment cell is especially relevant to marine and coastal management at Ashburton North because disruption of one part of the cell is highly likely to affect the stability of the coast downstream.

The cell has two sectors: west of the mouth of the Ashburton River between Tubridgi Point and Entrance Point; and the eastern shore from the river mouth to Coolgra Point. Sediment in the western sector is largely marine sediment reworked by erosional processes acting on the shoreface and beach as well as by littoral drift along the shore. In contrast to this, sediment in the eastern sector including the coast of the proposed development site, is largely of fluvial origin and reworked as chenier spits migrating eastwards from the mouth of the Ashburton River

3.3 Shoreline Morphology, Tidal Creeks & Lagoons The following sections describe the coastline extending from the Ashburton Delta in the south-west, to Onslow Town Beach in the north-west. Key features include the active, deltaic complex of the Ashburton River, tidal creeks, sandy beaches, coastal dunes, rock outcrops and pre-existing coastal structures.

3.3.1 Ashburton Delta The Ashburton Eastern Delta is situated approximately 5 km east of the main Ashburton River channel, and is hydraulically connected to the river via a secondary entrance channel located on the eastern side of the delta (False Entrance) and other narrow channels. The Ashburton Eastern Delta is characterised by outer barrier spits, and internal lagoon areas




and by the presence of a well-established mangrove community within a network of relict cheniers and tidal creeks (Figure 3-1).

Figure 3-1: Components of the Ashburton Delta

The variable flow of the Ashburton River has built the delta system along a north-west facing, rocky shore. At any point in time, the Ashburton River typically flows along one main tributary, which carries the majority of water and sediment discharge. A number of other channels are present as paleochannel’s on the floodplains; these may carry fluvial flood waters, contain tidal creeks, or form billabongs during wet seasons. Under extreme flood events, channel avulsion can occur (i.e. a change in the main channel position), and this is typically associated with river systems bearing a high sediment load, under relatively low wave and tide conditions (Coleman & Wright 1975). There are three general entrance locations that intermittently migrate, close up and break open (see Figure 3-2 and Figure 3-3).




Figure 3-2: Entrance Point looking west (April 2012)

Figure 3-3: Entrance Point looking east toward the Project site (April 2012)




The shape of the Ashburton Eastern Delta and sandy barrier spits is also indicative of a coastal environment subject to strong eastward littoral transport. Barrier spits are a substantial store of unstable sediment, and which typically progressively migrate landward and alongshore through wave action. Due to their low elevation the spits are particularly vulnerable to change during cyclone activity and flood events, which includes spit deflation and the formation of 'new' entrance channels which connect lagoons areas and tidal creeks within the delta to the ocean. At the site of an active channel, a local salient and entrance shoal structure commonly forms, which may be rapidly destabilized if the river or tidal flow switches to an alternate channel.

The capacity for the Ashburton River to episodically release massive sediment loads during floods contributes significantly to the dynamic nature of the coast around the Ashburton Delta. The coarse fraction is generally deposited near the ocean entrance channel where it accumulates to form an extensive delta and acts as a sediment source for alongshore transport. Growth of the delta, including barrier spits, generally follows period of high river flow, with erosion during periods of low flow.

Significant changes to configuration of the Ashburton Eastern Delta are evident in the historic shoreline movements (Figure 3-4). Changes include internal channel movements, evolution of coastal barrier spits (through either seaward or landward migration) and switching of entrance channels. The following features of the creek entrance and bars are noted in the historic shoreline movement records:

♦ Barrier spits between 1963 and 1973 experienced significant growth after severe tropical cyclone impacts in the early 1960s;

♦ In 1973, the location of the spit on the western side of Entrance Point was also located 300m further offshore than its location in 2009.

♦ False Entrance, which is connected to the main Ashburton River channel, closed between 2001 and 2004.

♦ The eastern spit at Entrance Point migrated eastwards between 1973 and 2008 by approximately 2.2 km. The rate of migration has been in the order of 100 m/yr since 1993 following significant flood events between 1995-2000 and the spit welded to shore after 2004 which has contributed to a significant build-up of sediment in the vicinity of the Project site. The spit impounds a shallow lagoon which is approximately 50 m wide for much of its length.

♦ The barrier spit on the eastern side of Entrance Point is expected to progressively migrate eastward, and may contribute to an increased supply of sand to the Project site in the future.




Figure 3-4: Ashburton Eastern Delta (1963-2009)

The Ashburton Delta and river support valuable habitats, such as mangroves communities, which are important for the conservation of listed species, including juvenile turtles and sawfish. Listed species potentially inhabiting the Ashburton Delta are listed in Appendix A. The green sawfish (P. zijsron) have been recorded in the Ashburton delta while the freshwater sawfish (Pristis microdon) has been recorded upstream in the Ashburton river system. Both species are protected within Western Australian State Waters under the Fish Resources Management Act.

Medium density nesting by the Flatback turtle (Natator depressus), corresponding to an estimated nesting population of 100-500 female turtles, has been recorded at the beaches on the western side of the Ashburton Delta, approximately 4 km to the west of the ANSIA (Chevron 2015). Other than this, very little marine turtle nesting activity occurs on the mainland beaches between Locker Point and Onslow (Pendoley Environmental 2009). Data from turtle surveys undertaken since 2009 indicate that there is a low level of flatback turtle nesting, corresponding to an estimated nesting population of 13-16 female turtles, on Sunset Beach (Chevron 2015). However, all recorded nesting activity observed on the mainland beaches is of very low density with large sections of beach likely experiencing no nesting activity at all (Pendoley 2009).




3.3.2 Hooley Creek Hooley Creek is a fluvial overflow channel and tidal creek located immediately to the East of Ashburton North. It has three distinct tidal channels, with a single ocean inlet formed at the eastern end of a broad barrier sand spit (Figure 3-5). The spit and entrance are highly dynamic with the spit having been deflated and rebuilt a number of times, influencing tidal exchange to the creek systems (Figure 3-5). The cross-sectional structure of the creeks behind the barrier spit is largely determined by historic flood events; during strong runoff flooding, the channels are scoured to a larger cross-sectional width, while during low flow conditions the channels gradually narrow toward a smaller cross-sectional width. The continued functionality of Hooley Creek is therefore dependent on tidal flushing via an unobstructed ocean inlet. The cross-sectional area of the channels provides an indicative geomorphic marker of the hydraulic exchange between the ocean and tidal creek network, along with the relative supply of littoral sediment. Consequently, the channel morphology provides a proxy indicator of both the functionality of the tidal creek network as a fringing coastal habitat (exchange efficiency) and maintenance of littoral transport (sand supply). Under constrained flows or high alongshore supply, the channel tends to close; whilst under enhanced flow or when starved of sediment supply, the channel is likely to open.

The Hooley Creek system also supports valuable habitats, including mangrove communities, which are important for the conservation of listed species, such as juvenile turtles and sawfish. Listed species potentially inhabiting Hooley Creek are listed in Appendix A. The green sawfish (P. zijsron) has been recorded in Hooley creek and is also protected within Western Australian State Waters under the Fish Resources Management Act. In addition, Hooley Creek is used by nearby Onslow Salt for bitterns discharge.

Figure 3-5: Hooley Creek Entrance Bar and Creek System (2009)




Figure 3-6: Hooley Creek Entrance Bar (1963-2009)

3.3.3 The Eastern Beaches The shoreline between Hooley Creek and Beadon Point consists of discontinuous limestone outcrops, sandy beaches and frontal dune systems. The dunes are of variable height, width and vegetation, and are vulnerable to erosion during extreme weather conditions. The shoreline is intersected by Four Mile Creek, a tidal creek ~2 km east of Hooley Creek. The beach extending from Four Mile Creek to Beadon Point is known locally as Sunset Beach and holds high recreational value to the residents of Onslow for four-wheel driving and fishing. Turtle tracks and nesting have been observed at Sunset Beach, however the beach is not considered nesting habitat for turtles due to the low numbers of individuals that visit the beach and the high level of anthropogenic impacts to this location associated with recreational beach driving and feral animal predation.

3.3.4 Onslow Town Beach & Seawall Onslow Town Beach, between Beadon Point and Beadon Creek, has high recreational value and has also experienced significant historic change, including response to construction of a




rock training wall at Beadon Creek. This structure caused accretion to the south and erosion to the north of the beach between Beadon Creek and Beadon Point, prompting construction of a seawall to limit the potential for storm erosion to affect the town site.

The Onslow seawall was constructed in 1958/59 to provide protection to the town site from coastal erosion (MRA 2002). In 2002, works were conducted on the seawall to repair damage caused by Tropical Cyclone Vance. In 2012, prior to construction of the MOF, the condition of the seawall was assessed using a modified version of the US Army Corps of Engineers Repair, Evaluate, Maintain and Rehabilitate (USACE-REMR) technique (Oliver et al. 1998; USACE 2006) which is a standard procedure for evaluating the physical condition and performance of rock armoured breakwaters. The most northern section of the seawall was found to be in poor condition, while the remaining sections to the south were found to be in good condition with no significant defects. The beach in front of the seawall has experienced historic fluctuations in width both over time and alongshore. In 2012, beach width varied from 4 m at the north-west end to 35 m toward the south-east.

3.4 Coastal processes The study area is a highly dynamic coastal system, with high seasonal and interannual variability in littoral sediment transport and the potential for large fluxes of water and sediment from the adjacent tidal floodplain complex. The major transport path in the cell is eastwards along the shore, at the beachface, with much of the sediment being supplied as littoral drift along spits fed from the Ashburton River. There is also some evidence of sediment movement along slope breaks on the inner shelf and perhaps across the shelf pavement. Although these are not as substantial as the littoral pathway they may have ramifications for dispersion of dredged sediment placed on the shoreface and the rate of sedimentation for dredged navigation channels. Sediment sinks include long chenier spits, coastal dunes and inshore shoals as well as deposition on mudflats by tidal creeks.

At a local scale the active delta of the Ashburton River has been produced by the interaction of low to intermediate wave energy, strong littoral drift, micro- to meso-tidal fluctuations and modally low to moderate fluvial discharge; all of which may be overwhelmed by extreme conditions during tropical cyclones. The active deltaic plain is highly dynamic and provides a source of sediment for intermittent accumulation at the mouths of the Hooley Creek – East Creek tidal creek complex.

Sediment is exchanged between the coastal wetlands (salt flats and mud flats) and inshore waters via the tidal creeks. The dominant sediment transport mechanism apparently switches between two extremes. First, erosional scour of the salt flat and mud flat margins occurs as water levels fall after flood inundation by fluvial run off. Second, the tidal creeks may deposit silty sands and mud on the mudflats in places where the flood-tide flows are dominant and/or fluvial run-off is hindered.

Sediments from the Ashburton Delta contribute to a prevailing net eastward sediment transport through the combined effects of waves and currents. However, the prevailing eastward sediment transport is subject to mild reversal during winter and large, short-term transport pulses in either direction during tropical cyclones.

Estimates of net littoral transport rates within each sediment cell located between Ashburton Delta and Onslow Town Beach are shown in Table 3-1 and illustrated in Figure 3-7. These rates have been derived from long term analysis of shorelines from aerial imagery between 1963-2009 (Damara 2010) and suggest a notable decrease in transport rates east of Ashburton North. Numerical modelling results also estimated a net average eastward transport range of 20 000 to 60 000 m³/yr (DHI 2010).




Table 3-1: Estimated Baseline Net Littoral Transport Rates. Section Net Littoral Transport Rates (m³/yr)

Min Max Ashburton Eastern Delta 60,000 105,000

Ashburton North 60,000 105,000

Hooley Creek Entrance Bar 35,000 70,000

Hooley Creek to Four Mile Creek 15,000 40,000 NOTE: Minimum and maximum transport rates are based on shoreline movement analysis

Erosion and accretion trends between Ashburton Delta and Beadon Creek have been examined using photogrammetric analysis of historic aerial imagery from 1963, 1973, 1986, 1993, 2001, 2004, 2007 and 2009. Despite very high variability of forcing conditions, historic photographs show that many of the terrestrial features along the shoreline (such as dunes and lagoons) have maintained a similar position for decades, suggesting coastal dynamics are typically cyclic rather than progressive. Local coastal features experiencing significant change include the deltas, cheniers and spits at the mouths of tidal creeks.

The north-west facing coastline between the Ashburton River entrance and Entrance Point receded by approximately 50 m between 1973 and 2004. Imagery from 1993 and 2001 suggests a reasonably consistent trend of shoreline erosion in the order of 1.5 m/yr. Following a period of major flood events from 1995-2000, significant growth of the shoals and spits around the Ashburton Delta has occurred. Growth has included eastward migration of a barrier spit (Ashburton Eastern Chenier) east of Entrance Point. The spit gradually elongated, welding to the coast in 2005, which contributed to significant sand build-up in the vicinity of the Project site. The cycle of change occurring since the 1990s follows a similar pattern to that which occurred after a severe tropical cyclone caused destabilisation of spits in the early 1960s.

The Hooley Creek entrance is highly dynamic and is susceptible to both runoff flooding and tropical cyclone impacts due to its low elevation. This was illustrated by the complete deflation of the spit during TC Vance in 1999. Under typical sediment transport conditions, eastward migration of sand results in growth of the entrance spit and shoal, which is evident in recovery of the spit since 2001. Since 2004, development of the spit has been particularly rapid, and is likely to be a response to increased sediment supply following welding of the Ashburton Eastern Chenier to shore after 2004. The Hooley Creek entrance is strongly influenced by alongshore sediment transport, with the capacity to intermittently close if average littoral transport exceeds 6000 m3 per month (Damara 2011b).

The entrance to Four Mile Creek has historically shifted, with an orientation to the east observed in 1963 before shifting to the west between 1973 and 1986. Further westerly migration of the spit and entrance channel has been evident since 2001.

Sunset Beach has been largely accretionary over the historic record, with erosion of the primary dune and deflation of the foredune occurred during extreme cyclones, including the February 1963 cyclone and TC Vance in 1999. These events were followed by periods of recovery, including rebuilding of the foredune. Recovery of up to 20m of dune erosion following TC Vance occurred within approximately 5 years.




Figure 3-7: Littoral Transport and Net Erosion and Accretion Rates




3.5 European Heritage The Ashburton River region was first settled by Europeans in 1879, and an increase in the size of coastal trading vessels and siltation at the river landing led to attempts to construct a sea jetty and a connecting tramline in 1897. This jetty was destroyed by a cyclone before completion, and a second sea jetty was constructed further west in 1901 (Figure 3-8). The second jetty did not function well and was abandoned after a third jetty was built at Beadon Point. The remains of the two original jetties are limited to some wooden posts and scattered artefacts, however both land and seabed areas area are registered under the Heritage of Western Australia Act 1990. The site is also listed on the Shire of Ashburton’s municipal inventory, which was compiled under the direction of the Heritage of Western Australia Act 1990.

Figure 3-8: Recorded Coastal European Heritage Sites Adjacent to the Project




4.0 RISK ASSESSMENT

Potential coastal process changes attributable to the Wheatstone Project, and their consequent environmental impacts were assessed prior to commencement of construction of nearshore facilities, using a risk assessment framework incorporating impact likelihood and consequences. Potential coastal process impacts associated with the construction and/or presence of nearshore facilities include the installation of the MOF and Shipping channel, and the effects of interrupting naturally occurring coastal sediment transport. The PLF is expected to be a permeable structure with relatively wide spacing between pile bents, and thus is not considered relevant in terms of potential impacts to coastal processes.

The Project has now completed construction of the MOF breakwaters east of Ashburton delta and dredging of the shipping channel. The following nearshore facilities have been identified as presenting a continued risk and have been re-assessed to determine the ongoing potential to influence Coastal Processes and features between the Ashburton Delta and Beadon Creek:

♦ Presence of the MOF; and ♦ Presence of the Shipping channel and turning basin

Areas potentially at risk include the East Ashburton Chenier (west of the Project), the Hooley Creek spit and eastern beaches including Sunset Beach and Onslow Town Beach. Potential impacts associated with these nearshore facilities/activities are described in the context of the following receptors:

♦ Littoral Sediment Transport ♦ Shoreline Geomorphology ♦ Tidal Creeks and Lagoons ♦ Recreational Amenity ♦ Onslow Seawall ♦ European Heritage Sites

4.1 Littoral Sediment Transport The majority of littoral transport is anticipated to be captured on the updrift (western) side of the MOF breakwaters under non-cyclonic conditions, with the dredged navigation areas offshore also potentially trapping sediment transported during higher energy conditions. This interruption, without management, would likely cause downdrift beach erosion (east of the MOF). Sand bypassing, expected to be required approximately every 5 years, is proposed to minimise change to littoral sediment transport.

There is a distinction between the potential impacts caused by interruption of the alongshore transport under non-cyclonic (prevailing) conditions, and those occurring immediately following cyclone impact. This is because under cyclonic conditions sediment transport is expected to undergo a reversal in direction which could result in erosion on the western of the MOF.

4.2 Shoreline Morphology (Erosion Trend) The presence of the MOF and Shipping Channel may modify the morphology of the beaches to the east through sediment starvation resulting in an erosion trend. An arcuate beach is




expected to form in the sheltered zone immediately to the east of the MOF as a result of this starvation, with this process evident in the 18 months since construction of the breakwaters first commenced. Similar impacts are also possible further to the east though are likely to occur over longer timeframes, while a reduction in post-storm erosion recovery rates is also possible.

Erosion and reduction in beach width of these shoreline features may cause impacts to the functionality of tidal creeks and lagoons at Hooley Creek and Four Mile Creek and non-cyclonic conditions and the East Ashburton Chenier under cyclonic conditions, as well as to the recreational amenity of Sunset Beach, structural stability of the Onslow Seawall, and exposure of heritage sites adjacent to the MOF. No impacts are anticipated to the western beaches of the Ashburton Delta due to prevailing eastward littoral sediment transport and the lee created by Entrance Point when transport reversals occur under cyclonic conditions (refer Section 3.4).

Conversely, under cyclonic conditions, or following sand-bypassing, there is a low risk of accumulation of sediments in the beaches and nearshore subtidal areas immediately east of the MOF though the likelihood of such impacts are much lower due to the anticipated frequencies of cyclones/sand bypassing campaigns. Accumulation has the potential to result in the closure/restriction of Hooley creek which could impact the functionality of the tidal creek system.

4.3 Tidal Creeks and Lagoons Three tidal creeks and coastal lagoons are present within the study area; the Ashburton Eastern Delta Entrance and lagoon, Hooley Creek and Four Mile Creek. Hooley Creek and the Ashburton Delta eastern lagoon are recognised as valuable mangrove and tidal creek habitats which support a variety of marine fauna, including EPBC listed species such as sawfish and juvenile turtles.

The interruption of littoral sediment transport and potential subsequent changes to erosion and accretion trends all have the potential to alter and destabilise the entrance morphology of these tidal creeks and lagoons. These changes may cause a reduction in tidal flushing due to closure of the tidal creek entrances or constriction of the tidal channels, or an increase in tidal flushing due to erosion or deflation of entrance bars and cheniers. Both outcomes would affect water quality, habitats including mangroves, and fauna within the creeks and lagoons. Changes in accessibility and tidal exchange may also subsequently reduce or alter the utilisation within the creeks and lagoons by listed species. Therefore, maintenance of the functionality of the tidal creeks and lagoons relies on entrance bars remaining intact, and entrance channels remaining open.

4.4 Recreational Amenity The beaches within the study area utilised for a range of recreational purposes. Sunset Beach which extends from Beadon Point to Four Mile Creek is primarily used for fishing and four-wheel driving, while Onslow Town beach is used for beach walks and swimming. The tidal creeks and adjacent beaches are used for fishing, boating and crabbing. For the purposes of this Plan, recreational amenity is defined as four-wheel vehicle beach access and beach widths suitable for recreational activities. The key risks to recreational amenity due to alteration of coastal processes include a reduction in beach access, width, compaction and smoothness.

4.5 Onslow Seawall The Onslow Seawall extends for approximately 900 m along the north-west section of Onslow Town Beach. The beach fronting the seawall protects it from damage during extreme




metocean conditions, and historic erosion trends have caused damage to the structure in the past. The interruption to littoral sediment transport by the Project, and subsequent possible erosion trends, has the potential to cause further damage to the seawall through exposure to metocean forces.

4.6 Heritage Sites Sites with European heritage values have been identified along the coast between the Ashburton River and Beadon Creek, (Damara 2010b). The majority of European heritage sites are landward of the coastal dunes, which means that effective beach management should protect these sites. However, some artefacts and heritage sites located across the shoreline and in the shallow marine waters to the west of the MOF may be at risk of exposure or damage due to erosion. In addition, potential sand management actions implemented under this Plan may also potentially impact some sites.

4.7 Summary In summary potential project-attributable impacts were identified which may occur following construction of nearshore facilities, associated with the interruption of littoral sediment transport under both non-cyclonic and cyclonic conditions. The following impacts are considered to present a medium residual risk:

♦ Erosion of the Hooley Creek entrance bar under non-cyclonic conditions, which may potentially threaten the functionality of the tidal creek and the mangrove habitats located on the landward side of the lagoon flats

♦ Erosion of the beaches east of the MOF under non-cyclonic conditions, including Sunset Beach and Onslow Town Beach which may potentially threaten beach amenity, the coastal defence of Onslow Town Site

♦ Reduced post-cyclone recovery rates for the beaches east of the MOF, including Sunset Beach and Onslow Town Beach which may potentially threaten beach amenity, the coastal defence of Onslow Town Site

♦ Closure / restriction of the entrance regime of Hooley Creek caused by downdrift accretion during an intense sediment transport reversal during cyclonic conditions which may potentially threaten the functionality of the tidal creek

The following potential impacts are considered to present a Low residual risk:

♦ Destabilisation of the beach and chenier on the east side of Ashburton delta caused by downdrift erosion driven by an intense sediment transport reversal during cyclonic conditions which may potentially threaten the functionality of the delta and the mangrove habitats located on the landward side of the lagoon flats and European heritage sit

♦ Closure / restriction of the entrance regime of Hooley Creek following beach nourishment activities immediately east of the MOF, which may potentially threaten the functionality of the tidal creek

♦ Erosion of Sunset Beach reducing recreational amenity ♦ Erosion of Onslow Town Beach impacting the integrity of the Onslow seawall

While the western Ashburton Delta beaches are recognised as providing nesting habitat for flatback turtles, these beaches are not expected to be impacted by changes to coastal processes arising from the Wheatstone project. Monitoring associated with potential project attributable impacts to these beaches is managed under the Wheatstone Conservation Significant Marine Fauna Interaction Management Plan (Chevron, 2015).




5.0 MONITORING

5.1 Overview The coastal monitoring program, described in the following sections, is designed to identify and quantify the impacts to coastal process during the Post-construction phase for Wheatstone nearshore marine facilities. The monitoring targets the project-specific risks outlined in Section 4.0 and addresses the requirements of Conditions 9-1 (MS 873) and 32.a (EPBC 2008/4469) (Table 5-1). Post-Construction monitoring is designed to continue as described below for 5 years commencing April 2015. The Post-construction monitoring program consists of three components:

♦ Routine monitoring, completed at the frequency outlined in this Plan (Section 5.2); ♦ Triggered monitoring, undertaken in response to defined triggers measured during

routine monitoring (Section 5.3); and ♦ Other monitoring, undertaken to determine the effectiveness of sand bypassing

campaigns and respond to unexpected project impacts (Section 5.4).

Table 5-1: Monitoring and Relevant Environmental Receptors

Monitoring Component

Min

iste

rial

Con

ditio

n

Factor

Litto

ral

Sed

imen

t Tr

ansp

ort

Sho

relin

e M

orph

olog

y

Tida

l Cre

eks

and

Lago

ons

Rec

reat

iona

l A

men

ity

Ons

low

S

eaw

all

Her

itage

S

ites

Rou

tine

Site Inspection 9-2-i 9-2-iii

Geomorphic Inspection 9-2.i 9-2.iii 9-2.vii

Topographic Survey 9-2-ii 32.a *

Hydrographic Survey 9-2.v *

Hooley Creek Survey 9-2.v

Community Consultation 9-2.vi Mangrove Monitoring - MAMTCPMP 9-2.iv

Trig

gere

d

Topographic / Hydrographic Survey 9-2-ii

Aerial/Satellite Imagery Capture 9-2-ii

Recreational Amenity Inspection 9-2-vi

Seawall Condition Assessment 9-2-i

Heritage Site Assessment 9-2.vii

Oth

er Bypass All

Contingency All * Littoral Sediment Transport is determined through the combination of topographic and hydrographic survey methods




Where practicable, Post-Construction Monitoring activities will be carried out during suitable tides and at the transition between the wet and dry seasons (notionally in April and October), as appropriate, to facilitate the observation of potential net changes that have occurred since between monitoring events.

5.2 Routine Monitoring Routine monitoring includes monthly, twice yearly and annually scheduled survey activities as well as ongoing community consultation. Routine monitoring data will be used to:

1. Monitor the rate of littoral sediment transport interruption and associated accretion updrift of the MOF and to subsequently inform the need and nature of sand bypassing operations; or

2. Identify the occurrence of a Significant Erosion/Accretion Event which may require management intervention prior to the need for sand bypassing operations.

5.2.1 Site Inspection Site inspections including the collection of on-ground photo-records will be undertaken monthly, where practicable, at key locations within the study area. On-ground photographs will be collected at fixed locations and directions. Site inspections will be used to assist the identification of Significant Erosion/Accretion Events. Information collected during routine site inspections will be reviewed to identify the need for Triggered Monitoring and/or associated management response.

5.2.2 Geomorphic Inspection A geomorphic inspection of key coastal features will be completed twice yearly by a qualified coastal specialist to identify coastline condition at regular intervals along the shoreline (Figure 5-1). Observations will be recorded on a standard proforma and include information on erosion or accretion, sediment characteristics and the extent of sedimentary features. During the geomorphic inspection, photographs will be captured at the fixed locations recorded during baseline surveys (Figure 5-1). These photographs will provide a continuous record of the coastline and will inform planning of potential sand bypassing and/or beach nourishment activities. The Onslow seawall will be visually assessed during geomorphic inspections for evidence of damage, breach or undermining. Any European heritage artefacts (e.g. jetty pylons) observed during the site inspection will be noted, with a description, location and photograph recorded.

5.2.3 Topographic Survey Topographic surveys will be obtained twice yearly to quantify changes in the sub-aerial coastal features above the water line within the study area. Topographic surveys will be captured using a technique (or combination of techniques) capable of generating a comprehensive digital surface elevation model. Where practicable, the survey should extend from ~0.0 m AHD (the landward limit of hydrographic surveys; Section 5.2.4) to landward of the 3.5 m AHD contour (Figure 5-1).

5.2.4 Nearshore Hydrographic Survey Nearshore Hydrographic surveys will be captured annually to document the sub-tidal morphology of the coastal system. The hydrographic surveys will cover the longshore extent shown in Figure 5-1 extending to a depth of at least -2.5 m AHD. The hydrographic surveys shall have a maximum vertical tolerance of 0.3 m.




5.2.5 Hooley Creek Survey The channel morphology of Hooley Creek will be surveyed twice yearly as an indicator of the functionality of this tidal creek system. This survey involves collecting RTK-GPS spot depths along fixed transects (Figure 5-2). The elevations will be used to calculate the cross-sectional area (below 0.0 m AHD) of the tidal creek channels to document the potential for hydraulic exchange with external marine waters. As an alternative method, swathe measurements such as multi-beam or side-scan sonar may also be used.

5.2.6 Community Consultation Ongoing consultation and liaison with the Onslow community will be undertaken to identify any impacts on the recreational amenity of beaches in the study area. The Onslow Community Survey, completed on an annual basis, will include questions relating to the recreational values and amenity of local beaches. Relevant information regarding sand bypassing and other planned management actions will be presented to the Onslow Community Reference Group as relevant.

5.2.7 Mangrove Monitoring Monitoring of mangrove habitats consistent with the requirements of Condition 9-2.iv (MS 873) are implemented through the Wheatstone Mangrove, Algal Mat and Tidal Creek Protection Monitoring Plan (MAMTCPMP). Monitoring under the MAMTCPMP focusses on biological and structural habitat factors such as mangrove distribution, mangrove health and condition, turbidity, sedimentation (within the mangroves), onshore hydrological regime and other human impacts. Monitoring for mangrove habitats under this Plan focusses on the geophysical factors impacting on tidal exchange and physical protection from ocean driven wind and wave energy.

Potential restrictions or temporary closures of the channel entrances observed during monitoring undertaken under this Plan will be used to inform relevant management measures in the MAMTCPMP. This may require assessment of the mangrove monitoring frequency identified in the MAMTCPMP. Similarly, surveys of mangrove health and habitat condition (e.g. groundwater conditions, sedimentation/erosion) in the MAMTCPMP will inform the effectiveness of channel and lagoon entrance management in the CPMMP.

Continuous feedback between these programmes is important for effective environmental outcomes in relation to listed species habitat within these systems. Figure 5-3 illustrates the linkage between the MAMTCPMP and the CPMMP for the relevant monitoring aspects and environmental factors.




Figure 5-1: Topographic and Hydrographic Survey Zones.




Figure 5-2: Cross-section Channel-Throat Monitoring Locations




Figure 5-3: Links between the CPMMP and the MAMTCPMP




5.3 Triggered Monitoring Triggered monitoring will be conducted on an as needed basis, subject to the outcomes of routine monitoring. Triggered monitoring will be constrained to a targeted area as determined by a coastal specialist.

5.3.1 Triggered Topographic/Hydrographic Survey If a Significant Erosion/Accretion Event is detected during monthly routine site inspections, a targeted topographic or hydrographic survey of the affected area will be completed using methods consistent with the methods undertaken during routine monitoring (refer Section 5.2). This targeted topographic/hydrographic survey is intended to quantify the extent of the erosion and provide a baseline from which coastal recovery can be assessed.

5.3.2 Aerial/Satellite Imagery Capture Aerial or satellite imagery will be collected, as appropriate, and reviewed as part of desktop assessments. In conjunction with the review of on-ground photography (Section 5.2.1), the review of satellite imagery is intended to enable identification of shoreline changes associated with erosion trends and or following management responses such as sand bypassing. Collected aerial/satellite imagery will therefore be used to observe the widths, sizes, and positions of affected barrier spits / cheniers, lagoon entrances, tidal creek channels and other shoreline features.

5.3.3 Recreational Amenity Inspection In the event of community concerns or complaints regarding recreational amenity within the study area, further investigations will be completed during the next routine geomorphic inspection (Section 5.2.2). These investigations will be specific to the nature of the complaint, but may include measures or assessments of beach access, compaction and width.

5.3.4 Seawall Condition Assessment In the event that twice yearly seawall inspections indicate a reduction in the structural integrity of the Onslow Seawall, a formal seawall condition assessment will be completed during the same routine survey. The condition assessment will be conducted by a coastal engineer using a modified version (consistent with baseline surveys) of the US Army Corps of Engineers Repair, Evaluate, Maintain and Rehabilitate (USACE-REMR) technique (Oliver et al. 1998; USACE 2006).

5.3.5 Heritage Site Assessment In the event that an unrecorded European heritage artefact is discovered during routine monitoring, or sand bypassing is planned for an area within 20m of a recorded heritage site, the artefact(s) will be managed consistent with the requirements of the Wheatstone Cultural Heritage Impact Mitigation Strategy (Chevron 2013). Information regarding the location and condition of the heritage artefact will be collected and an assessment of potential risk to its integrity / values will inform bypassing or management planning.

5.4 Other Monitoring Other Monitoring will be undertaken on an as needed basis subject to the outcomes of routine monitoring, triggered monitoring and/or sand bypassing plans. Other monitoring is intended to support management actions as described in Section 6.0 and to enable flexibility in the monitoring program to survey coastal features within the study area that experience potential unforeseen project-attributable impacts.




5.4.1 Bypass Monitoring Bypass monitoring will be undertaken prior to, during and immediately following sand bypassing activities to ensure that the outcomes of these activities are consistent with objectives of the Plan. The locations, methods and timing of bypass monitoring activities will be dependent on the volume of sediment to be bypassed, the method of bypassing to be employed and the location of extraction and beach nourishment activities. Monitoring may include a subset of the methods described in Section 5.2 or Section 5.3, such as:

♦ On-ground photographs and Aerial/Satellite imagery to be collected at the bypassing and/or nourishment sites, continuing for an appropriate period following completion of bypassing.

♦ Community consultation, including public notices, notification of the CRG and maintenance of a complaints register.

♦ A check for heritage sites within the work areas prior to commencement of sand extraction.

5.4.2 Contingency Monitoring Contingency monitoring may be considered for areas or times outside of routine monitoring survey zones/schedules. These may include hydrographic surveys of nearshore areas adjacent to the Ashburton delta, Sunset Beach and Onslow Town Beach. Contingency monitoring may also be implemented should contingency management actions be required (as described in Section 6.7).

5.5 Summary The frequencies at which specific monitoring activities are conducted are detailed in Table 5-2, consistent with the requirements of Condition 9-2.viii (MS873).

Table 5-2: Summary of Coastal Process Monitoring Methods and Frequencies

Monitoring Component Frequency

Rou

tine

Site Inspection Monthly

Geomorphic Inspection Twice yearly

Topographic Survey Twice yearly

Hooley Creek Survey Twice yearly

Hydrographic Survey Annual

Community Consultation Ongoing

Mangrove Monitoring See MAMTCPMP

Trig

gere

d

Topographic / Hydrographic Survey

When triggered

Aerial/Satellite Imagery Capture

Recreational Amenity Inspection

Seawall Condition Assessment

Heritage Site Assessment

Oth

er Bypass Dependent on bypassing /

nourishment campaign

Contingency Dependent on contingency scenario




6.0 ENVIRONMENTAL MANAGEMENT TRIGGERS & ACTIONS

The triggers and management actions described in this section address the risk to coastal processes and features as a result of the nearshore facilities at Ashburton North, while recognising that the area can experience a high degree of natural variability. A key element of this Plan is to ensure that littoral sediment transport is maintained using an adaptive approach to sand management via bypassing and/or beach nourishment. The management triggers are assessed using the monitoring data (Section 5.0) and indicate the potential requirement for mitigation. The implementation of management actions may be subject to the consultation and/or approval of relevant stakeholders (Section 1.6).

6.1 Littoral Sediment Transport Periodic sand bypassing is intended to minimise the changes to historic patterns of littoral sediment transport, consistent with the requirements of Condition 9-1.i (MS873). This is achieved by transferring accumulated sediment from a designated extraction area occurring on the updrift (western) side of the MOF to the downdrift (eastern) side (Table 6-1). However sand bypassing must be carefully managed, as large pulses of sediment transport following bypassing can result in additional sedimentation and smothering issues.

Sand bypassing is triggered when a net accretion sediment volume in the Extraction Area exceeds 200,000 m3. The Extraction Area is shown in Figure 6-1 and is designated as the area extending 800m due west of the MoF occurring between the -2.5 m AHD contour and the +3.5 m AHD baseline contour (as measured during the October 2012 Baseline LiDAR survey). Based on predicted net accretion rates, and assuming no impacts are detected on the downdrift side of the MOF in the intervening period, sand bypassing is expected to occur approximately every 5 years.

Given the potential variation in erosion trends under varying conditions, a flexible and adaptable sand management approach is required to address the risk to littoral sediment transport interruption which incorporates beach nourishment at potentially multiple locations. As natural sediment transport is likely to re-establish 1-2 km east of the MOF, Disposal Area DA1 (Figure 6-1) is identified as the primary location for the placement of bypassed sediment. However, other locations (DA2-DA4; Figure 6-1) may also be utilised. The selection of locations and volumes of sand placed within the study area is therefore subject to a combination of the measured sand and other factors, such as the potential for bypassed sand to constrict the Hooley Creek entrance or cause navigation hazards. An indicative decision tree demonstrating how beach nourishment activities may be managed is shown in Figure 6-2.

The planning and execution of any sand bypassing operation, including selection of preferred techniques, and design of associated monitoring will be determined on a case-by-case basis.

Table 6-1 Management Triggers and Actions relating to Littoral Sediment Transport

Management Trigger Management Action

Routine topographic & hydrographic surveys indicate >200 000 m3 of sediment accumulated within the extraction zone (Figure 6-1) relative to baseline.

Sand bypassing operations will commence within 12 months of reporting.




Figure 6-1: Sand Bypassing Extraction and Disposal Areas




Figure 6-2: Indicative Beach Nourishment Process




6.2 Shoreline Morphology (Erosion Trend) Management of shoreline morphology is intended to minimise erosion trends, consistent with the requirements of Condition 9-1.ii (MS873). This is contingent on maintaining target widths of beaches, cheniers and spits within the study area (Table 6-2), or a rate of recovery consistent with historic patterns in the case of a natural erosion event. Maintenance of cheniers and spits is also intended to help maintain the functionality of tidal creeks and lagoons, consistent with the requirements of Conditions 9-1.iii and 9-1.iv (MS873) and 32.a (EPBC 2008/4469). Ambient and recovery management triggers are specified (Table 6-3), with recovery triggers to be implemented where shoreline morphology has been changed following a natural, non-project attributable erosion event in the study area (e.g. as a result of a tropical cyclone).

Table 6-2 Ambient and Recovery Targets for Shoreline Morphology

Feature Location Target

Ambient Targets – Minimum Average Width

Beaches

Sunset Beach 40 m – between 1 m AHD contour and 3.5 m AHD baseline contour*

Four Mile Creek to Hooley Creek

20 m – between 1 m AHD contour and 3.5 m AHD baseline contour *

MOF to Hooley Creek 40 m – between 1 m AHD contour and 3.5 m AHD baseline contour *

Spits / Entrance Bars / Cheniers

Four Mile Creek, Hooley Creek, East Ashburton Delta

20 m – between 1 m AHD contours on seaward and landward sides

Recovery Target – Percentage of sediment volume lost to erosion

Erosion-affected area As defined by survey

Recovery rate of 20% p.a. by volume above 0 m AHD contour until pre-erosion event condition is achieved

*3.5 m AHD baseline-contour - as measured during the October 2012 LIDAR survey.

The detection of a Significant Erosion Event during monthly routine site inspections triggers a desktop assessment carried out by a coastal specialist. The aim of this assessment will be to determine the cause of erosion (i.e. whether a metocean event such as a tropical cyclone or a project attributable change) and the need for a triggered topographic survey. A topographic survey will be carried out where the changes are greater than those expected under non-cyclonic conditions, as derived from baseline and monitoring data.

For a Significant Erosion Event induced by a metocean event, the affected coastal area is to be assessed against the ‘recovery’ target until the shoreline has recovered to its condition observed prior to the erosion event. Coastal sections unaffected by the observed Significant Erosion Event are to continue to be assessed against the ambient targets during routine topographic surveys.

For a project attributable Significant Erosion Event, potential management actions, such as beach nourishment are to be considered and implemented subject to engagement with relevant stakeholders.




Table 6-3 Management Triggers and Actions relating to Shoreline Morphology of the study area

Management Triggers Management Actions

Routine site inspection data indicates a Significant Erosion Event in the study area.

Desktop assessment will be undertaken by coastal specialist to identify cause of erosion and requirement for a triggered topographic survey in the area of erosion.

Assessment to be completed within one month of the routine site inspection.

Desktop assessment confirms requirement for triggered topographic survey.

A triggered topographic survey to be completed to quantify change associated with Significant Erosion Event.

For change induced by metocean events, apply ‘Recovery’ target to area affected by the metocean event, as defined by triggered topographic survey. Recovery target to be measured during routine topographic surveys.

Coastal specialist to determine the requirement for additional management, such as nourishment or other contingency management action (Section 6.7).

Routine topographic survey determines that widths between the MOF and Sunset Beach are below Ambient Targets or recovery is below Recovery Target as described in Table 6-2.

Beach nourishment at appropriate location (DA1-DA4) to be commenced within 6 months of completion of the survey report.

Routine topographic survey determines that widths between the MOF and Ashburton Delta are below Ambient Targets or recovery is below Recovery Target as described in Table 6-2.

Within one month of completion of survey report, coastal specialist to investigate risk of chenier destabilisation and determine requirement for additional management such as nourishment or other contingency management action (Section 6.7).




6.3 Tidal Creeks and Lagoons Management of tidal creeks and lagoons is intended to maintain the functionality of Hooley Creek and the Ashburton Delta coastal lagoon east of Entrance Point, consistent with the requirements of WA State Conditions 9-1.iii and 9-1.iv (MS873) and Commonwealth Condition 32.b (EPBC 2008/4469). This is contingent on maintaining habitat for EPBC listed species and mangroves, and ensuring tidal exchange through tidal creek entrances (Table 6-4). The maintenance of cheniers and entrance bars is to be managed via the Shoreline Morphology management triggers and actions (Section 6.2). In addition to the management measures described herein mangrove habitat is to be managed through the implementation of the MAMTCPMP.

Routine site inspections and Hooley creek surveys are designed to detect potential Significant Accretion Events, and the risk of closure or constriction of Hooley Creek and the Ashburton Eastern Delta Entrances. The detection of a Significant Accretion Event triggers a desktop assessment by a coastal specialist to determine the cause of the accretion, constriction and/or closure, and the subsequent potential requirement for excavation or opening.

Table 6-4 Management Triggers and Actions relating to Hooley Creek


Routine site inspection data indicates closure of Hooley creek entrance

Desktop assessment will be undertaken by coastal specialist to identify cause of closure and if project-attributable the requirements for excavation/reopening.

Assessment will be completed within one month of the routine site inspection.

Routine Hooley Creek survey indicates:

• Entrance channel (Section B) cross-sectional area (below 0 m AHD) is less than 50 m2 over two consecutive surveys; and/or

• Average cross-sectional area of the channel (excluding section B) measured below 0.0 m AHD relative to baseline over two consecutive surveys has either

o reduced by more than 50%; or o increased by more than 100%

Investigate cause of constriction/expansion during twice yearly routine reporting to determine requirement for excavation of channel / nourishment of Hooley creek spit.

Subsequent management actions to be determined following engagement with relevant stakeholders.




Table 6-5 Management Triggers and Actions relating to Ashburton Delta


Routine site inspection data indicates closure of Ashburton Eastern Delta Entrance for a period lasting longer than three months.

Desktop assessment will be undertaken by a coastal specialist to identify cause of closure and, if project-attributable, the requirements for reopening.

Assessment will be completed within one month of the site inspection.

6.4 Recreational Amenity Management of recreational amenity in the study area is intended to maintain the recreational value of the beaches between the MOF and Beadon Creek, consistent with the requirements of Condition 9-1.v (MS873). This is contingent on maintaining access and sufficient beach width and compaction for recreational purposes, particularly on Sunset Beach and Onslow Town Beach (Table 6-6).

Concerns or complaints raised by the community with respect to recreational amenity within the study area are to be assessed, as required, during the next twice yearly monitoring survey. The findings of the assessment are to be reported to the Community Reference Group and Shire of Ashburton. Potential management actions are to be determined subject to the outcomes of the assessment and consultation with the Shire of Ashburton.

Table 6-6: Management Triggers and Actions relating to Recreational Amenity

Management Triggers Management Action

Community concern regarding recreational amenity on Onslow Town Beach or Sunset Beach.

An assessment will be completed by a coastal specialist during the next twice yearly survey and reporting, in relation to the cause of the potential impact to recreational amenity.

A report of the findings will be provided to the Community Reference Group and Shire of Ashburton within three months of completion of the survey report.

Subsequent management actions will be determined in consultation with the Shire of Ashburton.

6.5 Onslow Seawall Management of the Onslow Seawall is intended to minimise the reduction in integrity and performance, consistent with the requirements of Condition 9-1.vi (MS873). This is contingent on maintaining sufficient beach width in front of the seawall to prevent damage from metocean forces (Table 6-7).




If evidence of a reduction in the structural of the integrity of the seawall is detected, or the beach width immediately adjacent to the seawall is measured below the target width a formal seawall condition assessment (Section 5.3.4) will be triggered. Potential management actions relating to the Onslow Seawall are to be determined subject to the outcomes of the formal assessment and consultation with the Shire of Ashburton.

Table 6-7 Management Triggers and Actions relating to the Onslow Seawall


Evidence of a reduction in structural integrity of the seawall is observed during the twice yearly site inspection.

A Seawall Condition Assessment will be undertaken during the routine geomorphic inspection. Investigate cause during twice yearly routine reporting.

A report of the findings will be provided to the Shire of Ashburton within three months of completion of the inspection report.

Subsequent corrective actions will be determined in conjunction with the Shire of Ashburton.

Routine topographic surveys determine that the average beach width, measured as the distance between the toe of the seawall and the 1.0 m AHD contour, is less than 5 m along the entire length of the seawall

Investigate the cause during twice yearly routine reporting.

A report of the findings will be provided to the Shire of Ashburton within three months of completion of the survey report.


6.6 Heritage Sites Management of heritage sites is intended to minimise reductions in integrity and value, consistent with the requirements of Condition 9-1.vii (MS873). This is contingent on maintaining records of heritage artefacts within the study area, and minimising disturbance to heritage artefacts through coastal erosion or sand bypassing (Table 6-8). Management triggers and actions in this section are consistent with the Wheatstone Cultural Heritage Impact Mitigation Strategy (Chevron 2013)

Table 6-8 Management Triggers and Actions relating to Heritage Sites


Opportunistic discovery of European heritage artefact during routine monitoring and/or sand bypassing.

The discovered European heritage artefacts will be reported to the Chevron Heritage Advisor.




Exposure of previously buried but known European heritage sites or artefacts as a result of shoreline erosion.

Integrity of known European heritage sites and artefacts within the coastal zone will be monitored, with options for artefact recording or preservation in the event of threat from further coastal erosion.

Coastal management works (e.g. sand bypassing) planned for an area within 20 m of a recorded European heritage site or artefact.

Identified European heritage sites that have not been removed will be identified on work plans and maps. Disturbance of heritage sites will not commence without appropriate approvals.

6.7 Contingency Management Actions Contingency management actions may be required to ensure that an adaptive management framework can be implemented under the plan. Contingency management may be triggered based on the results of routine monitoring, investigations into unexpected coastal impacts or through the detection of unintended outcomes from sand bypassing activities. Contingency management may include actions such as installation of beach control structures, compaction of recreational beaches, revegetation, change in bypassing frequency, and alternative options for beach nourishment. Contingency management actions may also require consultation with relevant stakeholders prior to finalisation.




7.0 REPORTING

This section provides a framework for external reporting to regulatory authorities relevant to this Plan, including scheduled and unplanned reporting.

7.1 Annual Compliance Reporting Consistent with MS 873 Condition 4 and EPBC Approval Condition 3, Chevron is required to submit an Annual Compliance Assessment Report to the CEO of the EPA (or publish on its website). As part of the preparation of an Annual Compliance Report, Chevron will assess its compliance with this Plan in the relevant period. An action table is provided in Appendix B to assist with identification of management actions listed within this Plan.

7.2 Non-compliance Reporting Any potential non-compliance, relevant to this Plan, will be reported to the CEO of the EPA within seven days of that potential non-compliance being known as required by MS 873 Condition 4-5.

Any potential non-compliance, relevant to this Plan, will be reported to the Commonwealth Department of The Environment within seven days of that potential non-compliance being known.

7.3 Incident and Other Reporting Consistent with Condition 9-4 (MS 873), Chevron will report any non-achievement of the management trigger referred to in Condition 9-2, along with any measures taken and/or proposed to be taken, and strategies to be implemented in response to the non-achievement, to the CEO of the OEPA, within 21 days of the non-achievement being identified.




8.0 REFERENCES

Chevron (2013). Wheatstone Project Cultural Heritage Impact Mitigation Strategy. Chevron Australia Pty Ltd.

Damara (2010) Coastal Geomorphology of the Ashburton River Delta and Adjacent Areas, Report 82-01-01, May 2010. Appendix P1 of Wheatstone Draft EIS/ERMP. Chevron Australia Pty Ltd.

Damara (2011a). Geoheritage Features of the Onslow Embayment: Coastal landforms, coral reefs and wrack lines. Report 82-04-RevA, Damara WA Pty Ltd, Innaloo, Western Australia.

Damara (2011b) Hooley Creek Tidal Inlet. Inlet Dynamics and Entrance Stability. Report 82-05-Rev0, Damara WA Pty Ltd, Innaloo, Western Australia.

DHI Water & Environment (2010). Wheatstone Project. Coastal Impacts Modelling. Appendix P2 of Wheatstone Draft EIS/ERMP. Chevron Australia Pty Ltd.

Oliver, J, Plotkin, D, Lesnik, J, Pirie, D (1998) Condition and Performance Rating Procedures for Rubble Breakwaters and Jetties, Technical Report REMR-OM-24, U.S. Army Construction Engineering Research Laboratory, Champaign, IL. <http://owww.cecer.army.mil/techreports/plorub/plorubb.remr.post.pdf>

Pendoley Environmental Pty Ltd. (2009). Wheatstone Project Marine Turtle Beach Survey, Onslow Mainland Area and Nearby Islands, 25 January – 6 February 2009. Unpublished report for Chevron Australia Pty Ltd.

RPS. (2010). Technical Appendix - Marine Turtles. Unpublished report for Chevron Australia Pty Ltd., March 2010.

Semeniuk, V. (1996). Coastal forms and Quaternary processes along the arid Pilbara coast of north-western Australia. Palaeogeography Palaeoclimatology Palaeoecology. 123 (36982): 49-84.

United States Army Corps of Engineers: USACE. (2006) Coastal Engineering Manual. EM 1110-2-1100.




APPENDICES

CONTENTS

APPENDIX A CONSERVATION SIGNIFICANT SPECIES ......................................... 54 APPENDIX B ACTION TABLE ................................................................................... 55




Appendix A Conservation Significant Species

Common name Scientific name Relevant Conservation Act

EPBC1 WCA2 FRMA3

Saltwater Crocodile Crocodylus porosus Protected Not Listed Not Listed

Loggerhead Turtle Caretta caretta Endangered Not Listed Not Listed

Green Turtle Chelonia mydas Vulnerable Rare Not Listed

Hawksbill Turtle Eretmochelys imbricata

Vulnerable Rare Not Listed

Flatback Turtle Natator depressus Vulnerable Rare Not Listed

Green Sawfish Pristis zijsron Vulnerable Rare Protected

Freshwater Sawfish Pristis microdon Vulnerable Rare Protected

Narrow Sawfish Anoxypristis cuspidata Not Listed Not Listed Protected

1. Environment Protection Biodiversity Conservation Act 1999 (Commonwealth) 2. Wildlife Conservation Act 1950 (Western Australia) 3. Fisheries Resource Management Act 1994 (Western Australia)




Appendix B Action Table Section Actions

5.1

Where practicable, Post-Construction Monitoring activities will be carried out during suitable tides and at the transition between the wet and dry seasons (notionally in April and October), as appropriate, to facilitate the observation of potential net changes that have occurred since between monitoring events.

5.2

Routine monitoring includes monthly, twice yearly and annually scheduled survey activities as well as ongoing community consultation. Routine monitoring data will be used to:

1. Monitor the rate of littoral sediment transport interruption and associated accretion updrift of the MOF and to subsequently inform the need and nature of sand bypassing operations; or

2. Identify the occurrence of a Significant Erosion/Accretion Event which might require management intervention prior to the need for sand bypassing operations.

5.2.1

Site inspections and on-ground photo-records will be collected monthly, where practicable, at fixed, key locations within the study area with photographs to be collected facing all directions from a designated photo-point. Site inspections will be used to assist the identification of Significant Erosion/Accretion Events. Information collected during inspections/photo-records will be reviewed approximately to identify the need for Triggered Monitoring and/or prompt management response.

5.2.2

A geomorphic inspection of key coastal features will be completed twice yearly by a qualified coastal specialist to identify coastline condition at regular intervals along the shoreline (Figure 5-1). Observations will be recorded on a standard form and include information on erosion or accretion, sediment characteristics and the extent of sedimentary features. During the geomorphic inspection, photographs will be captured at the fixed locations recorded during baseline surveys (Figure 5-1). These photographs will provide a continuous record of the coastline and will inform planning of potential sand bypassing and/or beach nourishment activities. The Onslow seawall will be visually assessed during geomorphic inspections for evidence of damage, breach or undermining. Any European heritage artefacts (e.g. jetty pylons) observed during the site inspection will be noted, with a description, location and photograph recorded.

5.2.3

Topographic surveys will be obtained twice yearly to quantify changes in the aerial coastal features within the study area. Topographic surveys will be captured using a technique (or combination of techniques) capable of generating a comprehensive digital surface elevation model. Where practicable, the survey should extend from ~0.0 m AHD (the landward limit of hydrographic surveys; Section 5.2.4) to landward of the 3.5 m AHD contour (Figure 5-1).

5.2.4

Nearshore Hydrographic surveys will be captured annually to document the sub-tidal morphology of the coastal system. The hydrographic surveys will cover the longshore extent shown in Figure 5-1 extending to a depth of at least -2.5 m AHD. The hydrographic surveys shall have a maximum vertical tolerance of 0.3 m.




5.2.5

The channel morphology of Hooley Creek will be surveyed twice yearly as an indicator of the functionality of this tidal creek system. This survey involves collecting RTK-GPS spot depths along fixed transects (Figure 5-2). The elevations will be used to calculate the cross-sectional area (below 0.0 m AHD) of the tidal creek channels to document the potential for hydraulic exchange with external marine waters. As an alternative method, swathe measurements such as multi-beam or side-scan sonar may also be used.

5.2.6

Ongoing consultation and liaison with the Onslow community will be undertaken to identify any impacts on the recreational amenity of beaches in the study area. The Onslow Community Survey, completed on an annual basis, will include questions relating to the recreational values and amenity of local beaches. Relevant information regarding sand bypassing and other planned management actions will be presented to the Onslow Community Reference Group as relevant.

5.2.7

Potential restrictions or temporary closures of the channel entrances observed during monitoring undertaken under this Plan will be used to inform relevant management measures in the MAMTCPMP. This may require assessment of the mangrove monitoring frequency identified in the MAMTCPMP. Similarly, surveys of mangrove health and habitat condition (e.g. groundwater conditions, sedimentation/erosion) in the MAMTCPMP will inform the effectiveness of channel and lagoon entrance management in the CPMMP.

5.3 Triggered monitoring will be conducted on an as needed basis, subject to the outcomes of routine monitoring. Triggered monitoring will be constrained to a targeted area as determined by a coastal specialist.

5.3.1

If a Significant Erosion/Accretion Event is detected during monthly routine site inspections, a targeted topographic or hydrographic survey of the affected area will be completed using methods consistent with the methods undertaken during routine monitoring (refer Section 5.2). This targeted topographic/hydrographic survey is intended to quantify the extent of the erosion and provide a baseline from which coastal recovery can be assessed.

5.3.2

Aerial or satellite imagery will be collected, as appropriate, and reviewed as part of desktop assessments. In conjunction with the review of on-ground photography (Section 5.2.1), the review of satellite imagery is intended to enable identification of shoreline changes associated with erosion trends and or following management responses such as sand bypassing. Collected aerial/satellite imagery will therefore be used to observe the widths, sizes, and positions of affected barrier spits / cheniers, lagoon entrances, tidal creek channels and other shoreline features.

5.3.3

In the event of community concerns or complaints regarding recreational amenity within the study area, further investigations will be completed during the next routine geomorphic inspection (Section 5.2.2). These investigations will be specific to the nature of the complaint, but may include measures or assessments of beach access, compaction and width.

5.3.4

In the event that twice yearly seawall inspections indicate a reduction in the structural integrity of the Onslow Seawall, a formal seawall condition assessment will be completed during the same routine survey. The condition assessment will be conducted by a coastal engineer using a modified version (consistent with baseline surveys) of the US Army Corps of Engineers Repair, Evaluate, Maintain and Rehabilitate (USACE-REMR) technique (Oliver et al. 1998; USACE 2006).




5.3.5

In the event that an unrecorded European heritage artefact is discovered during routine monitoring, or sand bypassing is planned for an area within 20m of a recorded heritage site, the artefact(s) will be managed consistent with the requirements of the Wheatstone Cultural Heritage Impact Mitigation Strategy (Chevron 2013). Information regarding the location and condition of the heritage artefact will be collected and an assessment of potential risk to its integrity / values will inform bypassing or management planning.

5.4

Other Monitoring will be undertaken on an as needed basis subject to the outcomes of routine monitoring, triggered monitoring and/or sand bypassing plans. Other monitoring is intended to support management actions as described in Section 6.0 and to enable flexibility in the monitoring program to survey coastal features within the study area that experience potential unforeseen project-attributable impacts.

5.4.1

Bypass monitoring will be undertaken prior to, during and immediately following sand bypassing activities to ensure that the outcomes of these activities are consistent with objectives of the Plan. The locations, methods and timing of bypass monitoring activities will be dependent on the volume of sediment to be bypassed, the method of bypassing to be employed and the location of extraction and beach nourishment activities.

6-1 The planning and execution of any sand bypassing operation, including selection of preferred techniques, and design of associated monitoring will be determined on a case-by-case basis.

6-1 [If] Routine topographic & hydrographic surveys indicate >200 000 m3 of sediment accumulated within the extraction zone (Figure 6-1) relative to baseline

[Then] Sand bypassing operations will commence within 12 months of reporting.

6-2

[If] Routine site inspection data indicates a Significant Erosion Event in the study area.

[Then] Desktop assessment will be undertaken by coastal specialist to identify cause of erosion and requirement for a triggered topographic survey in the area of erosion.

Assessment to be completed within one month of the routine site inspection.

6-2

[If] Desktop assessment confirms requirement for triggered topographic survey.

[Then] A triggered topographic survey to be completed to quantify change associated with Significant Erosion Event.

For change induced by metocean events, apply ‘Recovery’ target to area affected by the metocean event, as defined by triggered topographic survey. Recovery target to be measured during routine topographic surveys.

Coastal specialist to determine the requirement for additional management, such as nourishment or other contingency management action (Section 6.7).

6-2

[If] Routine topographic survey determines that widths between the MOF and Sunset Beach are below Ambient Targets or recovery is below Recovery Target as described in Table 6-2.

[Then] Beach nourishment at appropriate location (DA1-DA4) to be commenced within 6 months of completion of the survey report.




6.2

[If] Routine topographic survey determines that widths between the MOF and Ashburton Delta are below Ambient Targets or recovery is below Recovery Target as described in Table 6-2.

[Then] Within one month of completion of survey report, coastal specialist to investigate risk of chenier destabilisation and determine requirement for additional management such as nourishment or other contingency management action (Section 6.7).

6-3

[If] Routine site inspection data indicates closure of Hooley creek entrance.

[Then] Desktop assessment will be undertaken by coastal specialist to identify cause of closure and if project-attributable the requirements for excavation/reopening.

Assessment will be completed within one month of the routine site inspection.

6-3

[If] Routine Hooley Creek survey indicates:

• Entrance channel (Section B) cross-sectional area (below 0 m AHD) is less than 50 m2 over two consecutive surveys; and/or

• Average cross-sectional area of the channel (excluding section B) measured below 0.0 m AHD relative to baseline over two consecutive surveys has either

o reduced by more than 50%; or o increased by more than 100%.

[Then] Investigate cause of constriction/expansion during twice yearly routine reporting to determine requirement for excavation of channel / nourishment of Hooley creek spit.

Subsequent management actions to be determined following engagement with relevant stakeholders.

6-3

[If] Routine site inspection data indicates closure of Ashburton Eastern Delta Entrance for a period lasting longer than three months.

[Then] Desktop assessment will be undertaken by a coastal specialist to identify cause of closure and, if project-attributable, the requirements for reopening.

Assessment will be completed within one month of the site inspection.

6-4

[If] Community concern regarding recreational amenity on Onslow Town Beach or Sunset Beach.

[Then] An assessment will be completed by a coastal specialist during the next twice yearly survey and reporting, in relation to the cause of the potential impact to recreational amenity.

A report of the findings will be provided to the Community Reference Group and Shire of Ashburton within three months of completion of the survey report.





6-5

[If] Evidence of a reduction in structural integrity of the seawall is observed during the twice yearly site inspection.

[Then] A Seawall Condition Assessment will be undertaken during the routine geomorphic inspection. Investigate cause during twice yearly routine reporting.

A report of the findings will be provided to the Shire of Ashburton within three months of completion of the inspection report.

Subsequent corrective actions will be determined in conjunction with the Shire of Ashburton.

6-5

[If] Routine topographic surveys determine that the average beach width, measured as the distance between the toe of the seawall and the 1.0 m AHD contour, is less than 5 m along the entire length of the seawall.

[Then] Investigate the cause during twice yearly routine reporting.

A report of the findings will be provided to the Shire of Ashburton within three months of completion of the survey report.


6-6

[If] Opportunistic discovery of European heritage artefact during routine monitoring and/or sand bypassing.

[Then] The discovered European heritage artefacts will be reported to the Chevron Heritage Advisor.

6-6

[If] Exposure of previously buried but known European heritage sites or artefacts as a result of shoreline erosion.

[Then] Integrity of known European heritage sites and artefacts within the coastal zone will be monitored, with options for artefact recording or preservation in the event of threat from further coastal erosion.

6-6

[If] Coastal management works (e.g. sand bypassing) planned for an area within 20 m of a recorded European heritage site or artefact.

[Then] Identified European heritage sites that have not been removed will be identified on work plans and maps. Disturbance of heritage sites will not commence without appropriate approvals.

7.1

Consistent with MS 873 Condition 4 and EPBC Approval Condition 3, Chevron is required to submit an Annual Compliance Assessment Report to the CEO of the EPA (or publish on its website). As part of the preparation of an Annual Compliance Report, Chevron will assess its compliance with this Plan in the relevant period. An action table is provided in Appendix B to assist with identification of management actions listed within this Plan.

7.2 Any potential non-compliance, relevant to this Plan, will be reported to the CEO of the EPA within seven days of that potential non-compliance being known as required by MS 873 Condition 4-5.

7.2 Any potential non-compliance, relevant to this Plan, will be reported to the Commonwealth Department of the Environment within seven days of that potential non-compliance being known.




7.3

Consistent with Condition 9-4 (MS 873), Chevron will report any non-achievement of the management trigger referred to in Condition 9-2, along with any measures taken and/or proposed to be taken, and strategies to be implemented in response to the non-achievement, to the CEO of the OEPA, within 21 days of the non-achievement being identified.

coastal processes monitoring and management plan · 2018-03-01 · ansia . ashburton north...

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