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360 Environmental Pty Ltd

Learmonth Habitat

Surveys Prepared for:

Subsea 7

August 2017

360 Environmental Pty Ltd

Disclaimer

This report is issued in accordance with, and is subject to, the terms of the contract between the Client and 360 Environmental Pty Ltd, including, without limitation, the agreed scope of the report. To the extent permitted by law, 360 Environmental Pty Ltd shall not be liable in contract, tort (including, without limitation, negligence) or otherwise for any use of, or reliance on, parts of this report without taking into account the report in its entirety and all previous and subsequent reports. 360 Environmental Pty Ltd considers the contents of this report to be current as at the date it was produced. This report, including each opinion, conclusion and recommendation it contains, should be considered in the context of the report as a whole. The opinions, conclusions and recommendations in this report are limited by its agreed scope. More extensive, or different, investigation, sampling and testing may have produced different results and therefore different opinions, conclusions and recommendations. Subject to the terms of the contract between the Client and 360 Environmental Pty Ltd, copying, reproducing, disclosing or disseminating parts of this report is prohibited (except to the extent required by law) unless the report is produced in its entirety including this cover page, without the prior written consent of 360 Environmental Pty Ltd.

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2003AF Learmonth Habitat Surveys Subsea7

360 Environmental Pty Ltd i

Executive Summary

Subsea 7 (Australia) Contracting Pty Ltd (Subsea7) is investigating the option to build a new Pipeline Bundle fabrication site in Western Australia (the Project) to further support growth within the Asia Pacific region. Subsea 7 has installed over 78 Pipeline Bundles in the North Sea, three in Australia and eight in Africa.

Learmonth (Exmouth) was chosen as the preferred site, pending the outcomes of initial baseline studies (including this study) and the results of a hydrographic survey. The primary objective of this study was to characterise and map the key benthic habitats along and adjacent to the proposed bundle launch route off Heron Point, Western Australia.

The initial survey area covered the proposed bundle launch route, along which benthic habitats are likely to be disturbed, plus an approximately 400m buffer to the north and south and a ~2 km buffer offshore.

Intertidal and subtidal habitats off Heron Point were surveyed in December 2016. Three intertidal and five subtidal benthic community and habitat (BCH) types were recorded within the survey area. Unvegetated soft sediment was the dominant habitat type (86.7%) with macroalgae and filter feeder-dominated reef habitats also present, all of which commonly occur within the shallow coastal waters of tropical north-west Australia.

The Marine Ecosystems Branch of the Environmental Protection Authority (EPA) was then consulted and a Local Assessment Unit (LAU) defined to allow the consideration of potential impacts at an appropriate scale. Intertidal and subtidal BCH within the LAU were then surveyed in May/June 2017. Five principal subtidal BCH types were recorded across the LAU; Soft sediment, Soft sediment with sparse seagrass, Soft sediment with filter feeders, Reef with macroalgae and Reef with filter feeders. Sparse seagrass (Halodule uninervis and patchy Halophila ovalis) was recorded in one area at densities ranging from 2% (trace) to 15%. Within the Bay of Rest several mangrove species were recorded; Grey Mangrove (Avicennia marina), Stilted Mangrove (Rhizophora stylosa) and the Club mangrove (Aegialitis annulata).

Ten subtidal infauna samples were collected using a Van Veen grab. The infaunal community structure was investigated by examination of the individual and species numbers recorded. The greatest number of species recorded in any sample was 27 and highest number of individuals was 80. Multi-Dimensional Scaling (MDS) analysis and dendrogram indicated that no site was clearly different from the rest, nor was any sites particularly similar to each other. The inshore sites at Heron Point (IS-1 and IS-2) were around 38% similar and sites IS-7 and IS-11 (both ~3.5 km offshore) were approximately 60% similar. The site with sparse seagrass cover (SEA-G) was least similar to any other site.

Worst-case potential losses of BCH have been calculated based on a 100 m wide disturbance footprint. This is considered highly conservative (worst case) given the


360 Environmental Pty Ltd ii

Bundle Launchway will be less than 20 m wide as it crosses the shoreline. The proportional losses of each BCH type within the LAU based on this scenario range from 0% (no loss) for mangroves, seagrass and turf algae, to 7.5% for soft sediment with filter feeders.

The BCH types identified are all likely to be well represented elsewhere in Exmouth Gulf, although surveys have generally been limited to those targeting seagrass habitats, or those undertaken in support of other infrastructure projects.


360 Environmental Pty Ltd iii

Table of Contents 1 Introduction .................................................................................................. 1 2 Previous Studies ........................................................................................... 3 2.1 Seagrass ................................................................................................................ 3 2.2 Macroalgae ............................................................................................................ 5 2.3 Mangroves ............................................................................................................. 5

3 Learmonth Planning and Conservation Status .............................................. 6 4 Commercial Fishing Activities ....................................................................... 8 5 State Guidance ............................................................................................ 9 5.1 Environmental Principles, Factors and Objectives (EPA 2016a) ............................ 9 5.2 Benthic Communities and Habitats (EPA 2016b) .................................................. 9 5.3 Protection of Benthic Communities and Habitats (EPA 2016c) ........................... 11 5.4 Local Assessment Unit ......................................................................................... 12

6 Survey Methods ......................................................................................... 15 6.1 Survey Area ......................................................................................................... 15 6.2 Intertidal Habitats ................................................................................................ 15 6.3 Subtidal Habitats .................................................................................................. 18 6.4 Video imagery analysis ......................................................................................... 20

7 Survey Results ........................................................................................... 24 7.1 Intertidal habitats ................................................................................................. 24 7.2 Subtidal habitats .................................................................................................. 30

8 Habitat Mapping ......................................................................................... 44 9 Initial impact assessment ............................................................................ 46 9.1 Historic impacts to BCH within the LAU .............................................................. 46 9.2 Potential future impacts to BCH within the LAU ................................................. 47 9.3 Consequences for biological diversity and ecological integrity ............................ 48

10 Discussion .................................................................................................. 50 11 Limitations .................................................................................................. 51 12 References ................................................................................................. 52


360 Environmental Pty Ltd iv

List of Tables

Table 1 Intertidal habitats identified during survey ......................................................... 24

Table 2 Mangrove habitats identified during survey at the Bay of Rest ......................... 26

Table 3 Subtidal habitats identified during survey .......................................................... 30

Table 4 Coverage of each BCH type within the Heron Point area .................................. 35

Table 5 Subtidal habitats identified within wider LAU .................................................... 36

Table 6 Univariate analysis results for infauna samples ................................................. 40

Table 7 Coverage of each BCH type within the LAU ..................................................... 44

Table 8 Coverage of each BCH type within the LAU ..................................................... 48

List of Figures

Figure 1 Site location and Project Envelope ................................................................. 2

Figure 2 The main boundaries of the Exmouth Gulf Prawn Fishery, extent of fishery closed waters, and area trawled in 2014 (DoF 2015) ........................................... 8

Figure 3 Existing and nominated reserve boundaries .................................................. 13

Figure 4 Local Assessment Unit ................................................................................. 14

Figure 5 Intertidal survey track (5 December 2016) ................................................... 16

Figure 6 Bay of Rest mangroves inspection (2 June 2017) ........................................ 17

Figure 7 Underwater video camera in tow frame ........................................................ 18

Figure 8 Subtidal survey transects (6-9 December 2016) .......................................... 21

Figure 9 Subtidal survey transects (30 June to 1 June 2017) .................................... 22

Figure 10 Infauna sampling locations ........................................................................ 23

Figure 11 Photograph locations ................................................................................. 28

Figure 12 Bay of Rest mangroves inspection (Track and Photographs) .................... 29

Figure 13 Substrate types recorded at Heron Point ................................................. 32

Figure 14 Subtidal habitat types at Heron Point ....................................................... 33

Figure 15 Multibeam and subtidal survey transects (Heron Point) ........................... 34

Figure 16 Substrate types within the LAU ................................................................ 38

Figure 17 Subtidal habitat types within the LAU ...................................................... 39

Figure 18 Infauna community MDS plot (top) and Dendrogram (bottom) ................ 41


360 Environmental Pty Ltd v

Figure 19 Habitat map ............................................................................................... 45

List of Appendices Appendix A Field Log Sheets .............................................................................. 55 Appendix B Video Transect Waypoints with corresponding Habitat Data ........... 56 Appendix C Infauna Data .................................................................................... 57 Appendix D Infauna sample photographs ............................................................ 58


360 Environmental Pty Ltd 1

1 Introduction

Subsea 7 (Australia) Contracting Pty Ltd (Subsea 7) is investigating the option to build a new Pipeline Bundle fabrication site in Western Australia (the Project) to further support growth within the Asia Pacific region. Subsea 7 has installed over 78 Pipeline Bundles in the North Sea, three in Australia and eight in Africa.

Towed Pipeline Bundles are multi flowline, control and injection lines encased within a larger carrier pipe between two towhead structures. The towhead structures range from simple valve structures to complex subsea processing structures. Bundle technology advantages are well established, including removal of specialist pipeline installation vessels, onshore fab and pre-commissioning, improved thermal and flow assurance capability. The system, which has been fully function tested onshore, is then launched and transported to its offshore location using the Controlled Depth Tow Method (CDTM). The CDTM was developed by Subsea 7 and involves the transportation of a Pipeline Bundle configuration suspended between two tow vessels. Upon arrival at a field, the Pipeline Bundle is manoeuvred into final location, the carrier pipe and towhead are then flooded to lower the Pipeline Bundle to the seabed and stabilise it in its final location.

The key bundle launch site requirements were defined as follows:

Land parcel of approximately 10 km by 1 km;

Proximity to the coast and a ‘level’ shore crossing (no significant coastal cliffs etc);

Access to deep water (>10 m at low tide) within a short distance of the shoreline; and

Land free from significant planning or environmental constraints and with suitable zoning and tenure (or potential for suitable zoning/tenure).

Learmonth (Exmouth) was chosen as the preferred site, pending the outcomes of initial baseline studies (including this study) and the results of a hydrographic survey.

The primary objective of this study was to characterise and map the key benthic habitats along and adjacent to the proposed bundle launch route off Heron Point (Figure 1).

CREATED APPROVED REVISIONCHECKED

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DATEPROJECT NO

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- LOCALITY MAP SOURCED FROM LANDGATE 2006- PROJECT ENVELOPE SOURCED 360 ENVIRONMENTAL 2017- ROADS SOURCED MRWA 2012- PROPOSED ACCESS ROAD SOURCED SUBSEA7 2017- SITE LAYOUT SOURCED SUBSEA7 2017- BUNDLE TOW ROUTE SOURCED UBSEA7 2017- IMAGERY SOURCED FROM LANDGATE 2013 (© Western Australian Land Information Authority 2017)

0

HORIZONTAL DATUM AND PROJECTION

COPYRIGHT: THIS DOCUM ENT IS AND SHALL REMAIN THE PROPERTY OF 360 ENVIRONMENTAL. THIS DOCUMENT MAY ONLY BE USED FOR THE PURPOSE FOR WHICH IT WAS COMM ISSIONED AND IN ACCORDANCE WITH THE TERMS OF ENGAGEMENT FOR THE COMMISSION. 360 ENVIRONMENTAL DOES NOT HOLD ANY RESPONSIBILITY FOR THE MISUSE OF THIS DOCUMENT.

a 10 Bermondsey St, West Leederville, 6007 WAt (08) 9388 8360f (08) 9381 2360w www.360environmental.com.au

- NOTE THAT POSITION ERRORS CAN BE >5M IN SOME AREAS

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Figure 1Site Location and Project Envelope

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PREPARED FOR



2 Previous Studies

The Department of Conservation and Land Management (CALM, now the Department of Biodiversity Conservation and Attractions) (1994) reported the western shore of Exmouth Gulf to be comprised of narrow beaches backed by dunes and fronted by sand and rock flats. The invertebrate fauna along the western shore was noted as being diverse and abundant, with an area of hard substrate to the north of the Bay of Rest supporting extensive soft corals and sponges. The Bay of Rest was noted as supporting a small but complex mangal system, distinct from that found along the eastern shore.

Historically there have been a number of surveys targeting subtidal benthic habitats in the Exmouth Gulf, including McCook et al. (1995), Hutchins et al. (1996) and Loneragan et al. (2003). McCook et al. (1995) published the first survey of seagrass communities of the east coast of the Gulf. Loneragan et al. (2003) surveyed the region for a Fisheries Research and Development Corporation project and the Department of Fisheries (WA) has since been undertaking annual surveys which largely follow the methods and sites established by Loneragan et al. (2003).

The studies to date have revealed the following information about the subtidal benthic habitats of the Gulf:

All the seagrass species found in the Gulf have tropical affinities and are predominantly fast growing ephemeral species;

The seagrasses in the Gulf undergo a marked seasonal cycle of growth and senescence;

There have been observations of a significant increase in seagrass biomass from October to November/December;

The seasonal cycle produces the least biomass from August to September and the most biomass from November to March;

Vegetated habitat is abundant in waters less than 2.5 m deep;

Algae is abundant throughout the year and are likely to have the greatest overall contribution to productivity; and

Seagrass and algae provide critical nursery habitat for fish and prawns (particularly tiger prawns).

2.1 Seagrass

Historically, the following seagrass species have been recorded for Exmouth Gulf:

Cymodocea angustata;

Cymodocea serrulata;



Halodule uninervis;

Halophila ovalis;

Halophila spinulosa;

Syringodium isoetifolium; and

Thalassodendron ciliatum.

McCook et al. (1995) undertook a survey in late September 1994 and found the seagrass communities in the shallow mid-east of the Gulf consisted of sparse and often patchy C. serrulata and C. angustata, lying between low tide level and 5 m water depth. Occasional small but dense beds of H. uninervis and S. isoetifolium were also identified in this area. Seagrasses were rare or absent below 5 m depth and in the areas of greatest abundance, percent cover was rarely greater that 5%. The low abundance of seagrass in the areas surveyed was attributed to the lack of suitable substrate; with the observed substrate either hard or mobile coarse sediments (McCook et al. 1995).

Loneragan et al. (2003) undertook qualitative surveys of habitat type in June 1999. Quantitative survey sites were then located and visited in November 1999, December 1999, October 2000, November 2000 and December 2001. After the initial survey, sites were relocated to within the 0-2.5 m depth zone as the June survey had found little evidence of vegetated substrates at depths > 2.5 m.

Loneragan et al. (2003) detected significant seasonal change in cover and biomass between surveys carried out in the same year, e.g. between October 2000 and November 2000. The dramatic increase in seagrass biomass in this short period suggests that the seagrass productivity in Exmouth Gulf exhibits a seasonal cycle consistent with other tropical marine systems in Australia. Lanyon and Marsh (1995) found that tropical seagrass communities have shown two to four fold differences in seagrass abundance depending on season, with a minimum in August to September and a maximum in November to March. The seagrasses found by McCook et al. (1995) in September (towards the end of the dry season) are likely to have been less abundant than they would have been one to two months later, at the beginning of the wet season.

From August 2013 to March 2015 (18 months), surveys of seagrass abundance were undertaken in the Exmouth Gulf region under the Western Australian Marine Science Institution (WAMSI) Dredging Science Node Project 5.3 (Vanderklift et al. 2016). The locations surveyed (South Muiron Island, Bundegi and Exmouth Gulf) encompassed a range in water clarity from clear to turbid. The Bundegi site was located approximately 40 km north of the proposed development site and the Exmouth Gulf sits (G1 and G2) were located approximately 25 km east of the proposed development site. At the Exmouth Gulf sites five species were recorded; Halodule uninervis, Halophila ovalis, Halophila spinulosa, Syringodium isoetifolium and Cymodocea angustata. At Bundegi two species were recorded; H. ovalis and H. uninervis. Bundegi and Exmouth Gulf have similar trends in cover, which tended to be highest in late summer (March 2015) and



lowest in winter, though the peak density of different species varied from November (H. ovalis) to March (H. spinulosa) (Vanderklift et al. 2016).

The levels of photosynthetically active radiation (or PAR) near the seafloor was lowest at the Exmouth Gulf sites, with a maximum in summer (December) and a minimum in winter (June). To provide a biologically meaningful reference point for these measurements, the PAR was compared against reported values for the onset of saturating light intensities for photosynthesis in H. uninervis (Ek). At light intensities above Ek the plants will not be light-limited. For H. uninervis, reported Ek values span a wide range, from approximately 50 to 300 μmol m-2 s-1 (Campbell et al. 2007, Lee et al. 2007, Collier et al. 2012, Ow et al. 2015). At the Exmouth Gulf sites PAR did not exceed 300 μmol m-2 s-1 on approximately 30 days of the 529 day study (or 0.1% of the time).

At the Exmouth Gulf sites, light intensity failed to exceed 9 μmol m-2 d-1 on 23 occasions; 6 of these lasted for more than 9 days and the longest event lasted for 31 days, indicating that the seagrasses at these sites are naturally subject to long durations of low light levels (Vanderklift et al. 2016). A measure of the Light Attenuation Coefficient (LAC), which describes how quickly (with depth) PAR is attenuated within the water column, was collected at a number of locations within the mapping area (refer 360 Environmental 2017).

2.2 Macroalgae

Algae in Exmouth Gulf includes a wide range of groups, from filamentous epiphytes such as Hydroclathrus, Padina, Sporochnus, Dictyota, Asparagopsis, Lauencia, Dictymenia tridens, Graciaria and Hypnea to perennial macrophytes, notably Sargassum decurrens and other Sargassum species. The ephemeral phaeophyte Hydroclathrus was particularly abundant and there were large amounts of surface drift and attached algae present (McCook et al. 1995).

2.3 Mangroves

As part of a study into mangrove forest structure and growth along the arid coast of the Pilbara region, permanent plots were established in the Bay of Rest to enable long-term measurements of trunk growth, net biomass production and tree survival (AIMS 2017).

At each location, three to four permanent plots were established in canopy forests of Avicennia marina and Rhizophora stylosa, the dominant mangrove tree species in the region. All trees in each plot were tagged and measured. Where seedlings occurred in the understorey, they were also tagged to follow their growth and survival.

Preliminary data indicated that the soils contained significantly higher concentrations of dissolved nutrients than soils from the wet tropics, consistent with the slow growth rates. Crabs were found to exert a strong influence (negative) on recruitment from seedlings (AIMS 2017).



3 Learmonth Planning and Conservation Status

The conservation values of Exmouth Gulf are recognised in several State government publications, policies and guidelines:

In 1975, the Conservation Through Reserves Committee recognised its conservation significance and recommended that a series of studies on biophysical characteristics of the tidal and supra-tidal flats of Exmouth Gulf be conducted (EPA 1975);

The fringe of arid zone mangroves along the east coast of Exmouth Gulf is recognised as being of ‘regional significance’ in EPA Guidance Statement No. 1 (EPA 2001);

The salt flats, mangrove creeks and inshore waters are within an indicative area recommended for reservation in the report ‘A Representative Marine Reserve System for Western Australia by the Marine Parks and Reserves Selection Working Group’ referred to as the Wilson Report (CALM 1994); and

The coastal waters along the east coast of Exmouth Gulf have been recommended for the ‘maximum’ level of ecological protection in the Department of Environment document Pilbara Coastal Water Quality Consultation Outcomes, (DoE 2006). The objectives for ‘maximum’ water quality protection are that there be no contamination and no detectable change from natural variation in water quality.

To protect the ecosystem services and recreational enjoyment that are provided along the east coast and south of Exmouth Gulf, the coastal waters have been a permanent nursery closure area for trawling since 1983, and were recommended as a ‘Fish Habitat Protection Area’ in the draft Fisheries Environmental Management Plan for the Gascoyne Region (Shaw 2002).

Consolidating this body of complementary policy instruments and guidelines, the Ningaloo Coast Regional Strategy Carnarvon to Exmouth, was endorsed by the WA Government and released by the WA Planning Commission in 2004 (WAPC 2004). The strategy recommends that the southern and south-eastern mangrove areas of Exmouth Gulf and adjacent coastal waters become marine protected areas, consistent with the findings of the Wilson Report (CALM 1994).

The EPA emphasised its established position on the regional significance of the Exmouth Gulf mangroves and their status as a ‘critical asset’ of the environment during its assessment of the proposed Yannarie Solar Salt project (EPA 2008).



The mangroves along the south-western end of Exmouth Gulf are described in the EPA’s Guidance Statement 1 (EPA 2001) as ‘Area 1: Bay of Rest’ and are classified as being of ‘Very High’ importance.

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5 State Guidance

5.1 Environmental Principles, Factors and Objectives (EPA 2016a)

The EPA’s Statement of Environmental Principles, Factors and Objectives (EPA 2016a) presents the principles of the Environmental Protection Act 1986, the environmental factors (those parts of the environment that may be impacted by an aspect of a proposal) and the objectives for each factor.

For the factor ‘Benthic Communities and Habitat’ (BCH) the objective is:

“To protect benthic communities and habitats so that biological diversity and ecological integrity are maintained.”

5.2 Benthic Communities and Habitats (EPA 2016b)

The recently released (13 December 2016) Benthic Communities and Habitats (EPA 2016b) lists the considerations of environmental impact assessment (EIA) for the factor Benthic Communities and Habitats to include:

application of the mitigation hierarchy to avoid and minimise impacts to benthic communities and habitats, where possible;

the benthic communities and habitat types affected by the proposal and their significance;

the alternative design options considered, and the management measures and approaches proposed, to avoid and minimise impacts to benthic communities and habitats;

the spatial and temporal scale of the residual impacts to benthic communities and habitats from the proposal, in combination with historical and approved losses, and the flow-on implications for ecological integrity and biodiversity;

the current state of knowledge of the affected benthic communities and habitats, including the services they provide, and the level of confidence underpinning the predicted residual impacts;

the risk posed to benthic communities and habitats and their associated environmental values and ecological integrity should those predictions be incorrect; and

whether proposed mitigation measures are technically and practically feasible.



Where Benthic Communities and Habitats has been identified as an environmental factor the EPA is likely to require the proponent to provide information or studies within the following broad topics:

appropriate scale mapping showing the types of benthic communities and habitats and their distribution extending to the edge of the zone of influence of the proposal;

assessment of the environmental values and significance of the benthic communities likely to be impacted at relevant scales (i.e. local, regional and state-wide);

identification of the threats and pressures the proposal is likely to have on the benthic communities and associated habitats and prediction of the extent, severity and duration of direct and indirect impacts (this is likely to involve predictive modelling to determine the ‘most likely worst case’ and ‘most likely best case’ loss scenarios);

description of the likely consequences for ecological integrity and biological diversity;

the likely impact that any changes in the benthic communities and/or habitat will have on other dependent factors;

design options and management measures and approaches to be implemented to avoid and/or minimise impacts on benthic communities and habitat;

cumulative impacts from other existing and approved developments in order to determine whether the proposal, in combination with other developments, will significantly impact benthic communities and/or their habitat, and any consequent impacts to ecological integrity and biodiversity;

proposed methods for determining actual losses of benthic communities and their habitats resulting from implementation of the development, and evaluation against the predicted loss;

analyses of the above to a standard consistent with recognised published guidance where available; and

specification of how the results of monitoring and evaluation of actual impacts on benthic communities and habitats will be publically reported.



5.3 Protection of Benthic Communities and Habitats (EPA 2016c)

The recently released (13 December 2016) Technical Guidance - Protection of Benthic Communities and Habitats (EPA 2016c) sets out:

a) the EPA’s contemporary approach for considering activities which may directly or indirectly cause impact or serious damage to, or irreversible loss of, benthic communities and habitats;

b) considerations for impact mitigation and how they should be applied; c) a framework for considering cumulative loss of benthic communities and habitats

and the potential consequences for marine ecological integrity and biological diversity;

d) the EPA’s expectations for information to be supplied by proponents for EIA; and e) the boundaries of a local assessment unit for the Port of Port Hedland that

replaces Environmental Protection Bulletin 14 (EPA 2011) and is to be used when assessing benthic impacts and cumulative losses of benthic communities and habitats in the area.

EPA (2016c) supersedes Environmental Assessment Guideline No. 3 - Protection of Benthic Primary Producer Habitats in Western Australia’s Marine Environment (EAG 3) (EPA 2009) which focussed on the Benthic Primary Producer Habitat (BPPH) components of BCH. EPA (2016c) lists BCH to include filter feeder communities growing on hard or soft substrates that may include sponges, ascidians, soft corals or hydroids; soft substrate infaunal communities that may include worms, molluscs and crustaceans; and hard and soft substrate benthic primary producer communities such as coral reefs, algal-dominated biogenic reefs, algal-dominated rocky reefs, seagrass meadows and mangrove forests. Algal mats and salt marshes growing on intertidal sand/mud flats are also classed as benthic primary producer communities. Benthic habitats are areas of seabed that have the necessary attributes, such as substrate type, water depth and clarity, degree of exposure to wave energy, to support these communities.

EPA (2016c) provides a risk-based spatial assessment framework for assessing environmental impacts on BCH and provides the means for evaluating cumulative losses (i.e. historic and proposed losses) of BCH within defined sub-ecosystem areas called local assessment units (similar to the approach presented in EAG 3).

A key difference between the approach previously recommended (EPA 2009) and that now recommended (EPA 2016c) is that the previous Cumulative loss guidelines (six categories of marine ecological protection each with allocated ‘allowable’ loss threshold) have been dropped. Instead, the predicted losses are to be considered in the context of objectives and targets within relevant management plans (EPA 2016c).



5.4 Local Assessment Unit

EPA (2016c) states that “Local assessment units (LAUs) are location specific and should be configured to take into account aspects of the local marine environment such as bathymetry and position of offshore reefs/islands, substrate type, water circulation patterns, exposure to waves and currents and biological attributes such as habitat types. Wherever possible, other variables related to the functional ecology of the system, (e.g. the length scales of key ecological processes such as trophic connectivity and larval dispersion) should also be considered when defining LAU boundaries. Other relevant information such as administrative (e.g. zoning schemes within marine conservation reserves) and jurisdictional (e.g. State coastal waters) boundaries should also be taken into account. All things considered, in WA’s marine environment LAUs would typically be approximately 50 km2 (e.g. a rectangular area defined by a 10 km stretch of coastline extending 5 km offshore (or to the limit of State Waters)). Larger or smaller LAUs will be considered if well justified.”

Several areas of Exmouth Gulf in proximity to Heron Point have been recognised for their environmental value, as follows:

An area of arid zone mangroves along the west coast of Exmouth Gulf (named the Bay of Rest) is recognised as being of ‘regional significance’ in EPA Guidance Statement No. 1 (EPA 2001);

The salt flats, mangrove creeks and inshore waters are within an indicative area recommended for reservation in the report ‘A Representative Marine Reserve System for Western Australia by the Marine Parks and Reserves Selection Working Group’ referred to as the Wilson Report (CALM 1994) (Figure 11); and

The coastal waters along the east coast of Exmouth Gulf (reflecting the areas recommended for reservation above) have been recommended for the ‘maximum’ level of ecological protection in the Department of Environment document Pilbara Coastal Water Quality Consultation Outcomes (DoE 2006).

Given the location of the preferred site at Heron Point within the area previously nominated for reservation, and within the Bay of Rest mangrove area (EPA 2001), an LAU was developed based on these datasets (Figure 12). The LAU was developed to be broadly consistent with the general guidance presented in Section 4.2 of EPA (2016), and utilizes the existing mapped boundaries of the above proposed conservation zones. The proposed LAU was discussed with the Marine Ecosystems Branch of the EPA, and endorsed, prior to the completion of habitat mapping across this area.

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COPYRIGHT: THIS DOCUMENT IS AND SHALL REMAIN THE PROPERTY OF 360 ENVIRONMENTAL. THIS DOCUMENT MAY ONLY BE USED FOR THE PURPOSE FOR WHICH IT WAS COMMISSIONED AND IN ACCORDANCE WITH THE TERMS OF ENGAGEMENT FOR THE COMMISSION. 360 ENVIRONMENTAL DOES NOT HOLD ANY RESPONSIBILITY FOR THE MISUSE OF THIS DOCUMENT.


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Figure 4 Local Assessment Unit


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6 Survey Methods

6.1 Survey Area

The initial Survey Area, in which groundtruth surveys were undertaken in December 2016, covered the proposed bundle launch route, along which benthic habitats are likely to be disturbed, plus an approximately 400m buffer to the north and south and an approximately 1 km buffer offshore.

Following discussions with the Marine Ecosystems Branch (MEB) of the Office of the Environmental Protection Authority (OEPA), a Local Assessment Unit (LAU) was developed to be broadly consistent with the general guidance presented in Section 4.2 of EPA (2016), and utilizing the existing mapped boundaries of proposed conservation zones (refer Figure 3 and Section 8.1 for further details).

Additional surveys within the LAU, which encompasses a total area of 83 km2, were completed in May/June 2017.

6.2 Intertidal Habitats

Intertidal habitats at Heron Point were visually inspected on a low spring tide on 5 December 2016 (Figure 5). The low tide at Exmouth was predicted to occur at 08:13 (WST) with a depth of 0.55 m above Chart Datum (BoM 2016). The survey was conducted between 08:20 and 09:50, with the tide observed to be rising from approximately 08:45 (WST).

A visual inspection of the northern mangroves within the Bay of Rest, to the south of Heron Point, was completed on 2 June 2017 (Figure 6).


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6.3 Subtidal Habitats

6.3.1 Habitat mapping

As reported from previous habitat mapping exercises in Exmouth Gulf, it was not possible to consistently differentiate reef, algae and seagrass areas from aerial imagery alone. Therefore groundtruth surveys, using towed video, were undertaken to enable such habitats to be mapped, and to provide more detailed information on these habitats.

A towed video system consisting of a standard definition video camera mounted on a tow frame (Figure 7) was used to record video footage at each survey location. The system was deployed from the stern of the vessel and towed at a speed of 1-2 km/h, at a height of approximately 0.2 m from the seabed. Footage was recorded directly to a hard drive, and a system-integrated GPS recorded the survey position at approximately 10 m intervals.

Figure 7 Underwater video camera in tow frame

A small Van Veen grab was used to confirm the sediment type and key species (if not able to be determined from the video footage).

An initial towed underwater video survey was undertaken off Heron Point in the period 6-9 December 2016, aiming to capture the period of peak seagrass biomass. Refer to Appendix A for field notes. A total of 47 towed video transects were conducted in the survey area offshore of Heron Point (Figure 8).

A follow-up survey was completed in May/June 2017 to characterise and map BCH throughout the LAU (Figure 9).

6.3.2 Soft sediment infauna characterisation

Subtidal infauna samples were collected using a Van Veen grab. Samples were wet sieved (through a 1mm sieve) offshore, using seawater, to separate the infauna from the fine sediments. The retained samples were then stored in 100% ethanol prior to transport to the laboratory for analysis.



The laboratory processing of samples for benthic infauna involved two processes:

Sample sorting—the separation of biological material from sediment, shell-hash, and other non-living biological material retained by the selected mesh size (e.g. 1.0 mm); and

Species identification and enumeration—the accurate identification (using stereomicroscopy) of all benthic macrofauna found in a sample to the lowest reliable taxonomic level and the accurate counting of the number of benthic macrofauna in each taxonomic category.

A single sample was collected at each site (Figure 10) for the analysis of the infauna community. The infaunal community structure was investigated by examination of the individual and species numbers recorded within each sample and by the use of multivariate analysis methods through use of PRIMER 5.0 software (Clarke & Warwick 2014).

Multivariate methods measure the similarity coefficients between samples. Hierarchical clustering (CLUSTER) was used to assess the similarity of sites based on the faunal components. The procedure generates a dendrogram indicating the relationships between sites based on a similarity matrix. Sample photographs (pre-sieving) are provided in Appendix D.



6.4 Video imagery analysis

On return to the office the video record was reviewed and data corresponding to each GPS waypoint collected along each transect. A number of habitat descriptors were recorded from approximately 30 second sections of video footage (representing an approximately 10 m long stretch of seabed), including:

Dominant seabed type (e.g. soft sediment, reef);

The percentage cover of flora (macroaglae or seagrass);

The abundance of fauna of different genera/species (e.g. sponges, soft corals, hard corals); and

Other features or mobile fauna as visible within the footage.

The GPS waypoints collected along each video track were then classified according to the seabed and habitat data (refer Appendix B). The classified video data was then overlayed with the backscatter data obtained from a multibeam survey off Heron Point to allow the accurate extrapolation of the data beyond the video tracks. The data was further extrapolated across the remainder of the LAU, assisted by the interrogation of aerial imagery.


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