Wallaroo Common User Export Facility Marine Ecological Assessment
Report for T-Ports Pty Ltd
J Diversity Pty Ltd
Rev 0, October 2020 Wallaroo Marine Ecological Assessment, October 2020
Cover photo: seagrass swimmer crab Nectocarcinus integrifrons in Posidonia sinuosa seagrass habitat. Photo: J. Brook, June 2020.
Disclaimer The findings and opinions expressed in this publication are those of the author and do not necessarily reflect those of T-Ports Pty Ltd. While reasonable efforts have been made to ensure the contents of this report are factually correct, the author does not accept responsibility for the accuracy and completeness of the contents. The author does not accept liability for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the contents of this report.
Revision history Rev Date Comment Author Reviewed A 19/08/2020 Initial Draft J. Brook M. Richardson B 10/09/2020 Modified according to review J. Brook M. Richardson C 21/09/2020 Modified according to review J. Brook M. Richardson and new information D 2/10/2020 Issued to client for circulation J. Brook
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Table of Contents 1 Introduction ...... 7 2 Methods...... 8 2.1 Habitat mapping ...... 8 2.1.1 Existing information...... 8 2.1.2 Towed camera survey ...... 8 2.1.3 Map generation...... 12 2.2 Dive surveys ...... 12 2.2.1 Reef surveys ...... 12 2.2.2 Seagrass surveys ...... 12 2.3 Literature review...... 12 3 Results...... 13 3.1 Towed camera surveys ...... 13 3.1.1 Proposed transhipment area alternatives ...... 13 3.1.2 Proposed breakwater...... 14 3.2 Dive surveys ...... 16 3.2.1 Reef surveys ...... 16 3.2.2 Seagrass surveys ...... 17 3.3 Breakwater footprint habitat map...... 24 3.4 Ecological values ...... 26 3.4.1 Megafauna ...... 26 3.4.2 Macroalgae ...... 26 3.4.3 Invertebrates...... 26 3.4.4 Fishes and sharks ...... 27 3.4.5 Seabirds and shorebirds...... 27 3.4.6 Marine pests ...... 27 3.5 Fisheries and Aquaculture ...... 28 3.5.1 Spencer Gulf Prawn Fishery ...... 28 3.5.2 Blue crab fishery...... 30 3.5.3 Marine Scalefish Fishery ...... 32 3.5.4 Central Zone Abalone fishery...... 33 3.5.5 Aquaculture...... 36 4 Impact Assessment ...... 37 4.1 Direct loss of habitat from breakwater construction ...... 37
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4.2 Indirect impacts on habitats during breakwater construction ...... 38 4.3 Indirect impacts on habitats due to changed coastal processes ...... 38 4.4 Impacts on seagrass from operations at the breakwater...... 38 4.5 Impacts on benthic habitats from transhipment point operations...... 38 4.6 Introduction of marine pests ...... 39 4.7 Underwater noise ...... 39 4.8 Vessel interactions with marine megafauna ...... 41 4.9 Impacts on birds...... 44 4.10 Impacts on fisheries and aquaculture...... 45 5 Conclusions ...... 45 6 References ...... 46 Appendix A. Records of macroalgae within the Atlas of Living Australia search area...... 51 Appendix B. Records of macroinvertebrates within the Atlas of Living Australia search area...... 52 Appendix C. Records of fishes and elasmobranchs within the Atlas of Living Australia search area...... 54
Table of Figures Figure 1. Existing mapping at 1:100,000 (DEW 2020a, Edyvane 1999) Existing Mapping at 1:100 (DEW 2020b, c, Miller et al. 2009) ...... 9 Figure 2. Habitat mapping 1:100 near the proposed causeway. Source: DEW 2020c, Miller et al. 2009...... 10 Figure 3. Regional perspective of habitats surrounding the proposed breakwater. Source: DEW 2020a, c...... 10 Figure 4. Water depth below lowest astronomical tide (LAT) near the proposed breakwater. Source: Flinders Ports 2020...... 11 Figure 5. Major habitat classes recorded on towed camera surveys in the proposed transhipment area alternatives...... 14 Figure 6. Towed camera habitat points over the proposed causeway footprint. State benthic habitat boundaries and habitat descriptors (DEW 2020) are shown (in red) for comparison...... 15 Figure 7. Locations of dive transects within reef habitat (2 x 50 m) and seagrass habitat (4 x 30 m) with respect to towed camera habitat points...... 16 Figure 8. Habitat map of the area surrounding the proposed breakwater...... 25 Figure 9. Spencer Gulf Prawn Fishery catch reporting blocks, prawn survey sites and bycatch survey sites near the proposed breakwater and PTAAs...... 29 Figure 10. Spencer Gulf Prawn Fishery footprint, based on 40% of the total effort during 2001/02– 2017/18. Source: Noell et al. 2019...... 30 Figure 11. Blue Crab Fishery catch reporting blocks near the proposed breakwater and PTAAs...... 31 Figure 12. Locations of Blue Crab Fishery survey locations in Spencer Gulf. Source: Beckmann & Hooper 2019...... 32
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Figure 13. Marine Scalefish Fishery catch reporting blocks near the proposed breakwater and PTAAs...... 34 Figure 14. Central Zone Abalone Fishery Spatial assessment units (SAUs) near the proposed breakwater and PTAAs...... 35 Figure 15. Aquaculture zones and leases/licences near Wallaroo. Source: PIRSA 2020...... 36 Figure 16. Atlas of Living Australia records of southern right whales in South Australia and near Wallaroo. Source: ALA (2019)...... 42 Figure 17. Shipping routes in and adjacent to Spencer Gulf, based on received Automatic Identification System data. Source: Izzo & Gllanders (2015), using data from www.marinetraffic.com...... 44 Table of Tables Table 1. Fauna recorded using Reef Life Survey method. F=fish survey, I/CF=invertebrate/cryptic fish survey...... 18 Table 2. Fauna recorded during seagrass transects. Common names follow Edgar (2008)...... 19 Table 3. Area of habitats mapped with the proposed breakwater footprint...... 24 Table 4. Introduced species near the proposed breakwater...... 28 Table 5. Indicative SEB offset payments in the Native Vegetation Fund...... 37
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Table of Plates Plate 1. Bare sediment with trace of macroalgae...... 13 Plate 2. Bare sediment with about 1% cover of macroalgae...... 13 Plate 3. Bare sediment with about 5% cover of macroalgae...... 13 Plate 4. Bare sediment with cover of sparse Halophila and 1–2% cover of macroalgae...... 13 Plate 5. Sargassum sp. Subgenus Sargassum with red filamentous epiphytes. Grey amorphous sponge to left, little weed whiting Neoodax balteatus near bottom centre...... 20 Plate 6. Ball coralline Jania microarthrodia (centre) and peacockweed Lobophora variegata...... 20 Plate 7. Caulerpa brownii...... 20 Plate 8. Rubble, including some pebbles covered with encrusting coralline macroalgae...... 20 Plate 9. Razor clam Pinna bicolor...... 20 Plate 10. Yellow encrusting sponge ...... 20 Plate 11. Yellow ball sponge ...... 21 Plate 12. Grey amorphous sponge...... 21 Plate 13. Brown macroalga Caulocystis cephalornithos ...... 21 Plate 14. Green coral Plesiastrea versipora ...... 21 Plate 15. Purple urchin Heliocidaris erythrogramma ...... 21 Plate 16. Posidonia australis with brown filamentous epiphytes...... 21 Plate 17. Mauve-mouthed ascidian Polycarpa viridis...... 22 Plate 18. Soft sponge ...... 22 Plate 19. Compound ascidian Botryllus schlosseri on Posidonia sinuosa ...... 22 Plate 20. Seagrass swimmer crab Nectocarcinus integrifrons...... 22 Plate 21. Queen scallop Equichlamys bifrons ...... 22 Plate 22. Grooved abalone Haliotis scalaris ...... 22 Plate 23. Bare sea star Uniophora nuda ...... 23 Plate 24. Smooth seaweed crab Naxia aurita...... 23 Plate 25. Southern biscuit star Tosia australis...... 23 Plate 26. Nudibranch Doriopsilla carneola ...... 23 Plate 27. Sea tulip Pleuroploca australasia...... 23 Plate 28. Southern sea cucumber Australostichopus mollis...... 23
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1 Introduction T-Ports are proposing a grain export facility near Point Hughes, Wallaroo, with inshore loading of barges with grain that is subsequently transferred to vessels up to Panamax class at a transhipment point approximately ten kilometres offshore. The inshore infrastructure includes an L-shaped breakwater comprising a causeway perpendicular to the shore which extends about 500 m offshore from the beach leading to a berthing/loading area approximately 200 m long, parallel to the shore. The breakwater would be constructed using rock and infill material sourced from land and there will be some piling required during construction of the berthing area. Operation of the terminal would involve 6–7 visits annually from Cape or Panamax size vessels, each requiring approximately 15 barge transfers. These operations would replace traditional grain loading of vessels at Wallaroo and Port Adelaide. This marine assessment describes: marine habitats within and surrounding the breakwater footprint (including a two-metre buffer) and within three potential transhipment area alternatives (PTAAs) each of 0.5 nautical mile radius. taxa recorded within a search area of 13 km radius, which includes all marine waters in Wallaroo Bay between Point Riley and Warburto Point, and within 10 km of any of the PTAAs. fisheries that operate within the region potential impacts of the construction or operation of the project on the above values and management/mitigation measures that could be adopted.
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2 Methods 2.1 Habitat mapping 2.1.1 Existing information Broad scale (1:100,000) mapping using satellite imagery (DEW 2020a, Edyvane 1999) indicates bare sand within and surrounding the proposed transhipment area alternatives (PTAAs) (Figure 1). However, video transects by DEW (2020b) and SARDI (PB & SARDI 2003) to the south of the PTAAs show that there is considerable heterogeneity within the ‘bare sand’ area, with habitats generally transitioning from west to east that include reef, bryozoans, sparse Posidonia seagrass, Halophila and dense Posidonia seagrass (Figure 1). Broad scale mapping of the area between the PTAAs and the causeway shows seagrass extending inshore to the proposed berthing area and part of the causeway. Habitat mapping of the inshore area (to a variable distance of 2–6 km offshore) has been superseded by finer scale mapping (1:10,000) using aerial photography, acoustic mapping and towed camera surveys (DEW 2020b, c, Miller et al. 2009), but this also shows seagrass (of various densities) extending the same distance inshore (Figure 1, Figure 2). The 250 m section of proposed causeway inshore from the mapped seagrass is designated as reef with a 100 m length of sand close to shore (Figure 2). A regional perspective of marine habitats (combining broad- and fine-scale mapping) is provided by Figure 3. Bathymetry data near the proposed breakwater (Figure 4) and the northern PTAA (not presented here) are also available. 2.1.2 Towed camera survey Towed camera surveys were undertaken at the three PTAAs and the causeway footprint on 16 and 17 June 2020, respectively. The surveys used a composite standard definition camera aimed 45° below horizontal, streaming to a screen on the vessel. Custom software was used by a trained marine ecologist to assign habitat attributes to GPS points as the footage was viewed live. The main features recorded were the percentage cover of seagrass and macroalgae as ranges: <1, 1–5, 5–10, 10–20% and increments of 20% thereafter. High definition video and still images were captured using a downward-facing GoPro Hero 4 camera. Additional post-field processing and quality assurance was undertaken to ensure the habitat point data were consistent with the video and field notes. Navigation was assisted by a geographical information system, which was used to show: the position of the vessel relative to the PTAA boundaries or breakwater footprint (approximate version only available at time of survey); additional habitat mapping data (see above); and the habitat data already accumulated during the towed camera survey.
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Figure 1. Existing mapping at 1:100,000 (DEW 2020a, Edyvane 1999) Existing Mapping at 1:100 (DEW 2020b, c, Miller et al. 2009)
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Figure 2. Habitat mapping 1:100 near the proposed causeway. Source: DEW 2020c, Miller et al. 2009.
Figure 3. Regional perspective of habitats surrounding the proposed breakwater. Source: DEW 2020a, c. 10 Wallaroo Marine Ecological Assessment, October 2020
Figure 4. Water depth below lowest astronomical tide (LAT) near the proposed breakwater. Source: Flinders Ports 2020.
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2.1.3 Map generation Habitat boundaries were drawn manually, informed by various information sources, including:
the habitat point data acquired during the towed camera survey observations of seagrass and reef cover during the dive surveys (see Section 2.2.1) aerial photography sourced through ArcGIS mapping software.. previous habitat mapping data The boundaries were converted to a polygon shapefile and habitat classes assigned to each polygon. 2.2 Dive surveys Surveys were undertaken on 17 June 2020 by scuba divers within reef and seagrass habitat, with locations determined in the field based on the results of habitat mapping. 2.2.1 Reef surveys Reef habitat was surveyed using the Reef Life Survey (2015) methods, which is based on 50 m transects along a consistent depth profile. Each transect is comprised of 20 evenly-spaced photoquadrats of habitat, a survey of fish within 5 m either side of the transect line, and a search for mobile invertebrates and cryptic fish within 1 m either side of the transect line. Only species whose adult stage has a size exceeding five centimetres were recorded. The Reef Life Survey methods have been applied across southern Australia, including more than 200 sites in South Australia, allowing the results to be put into a regional context. 2.2.2 Seagrass surveys A similar methodology to the reef surveys was applied to the seagrass habitat, but with a transect length of 30 m and searching limited to one metre on one side of the line. This was considered appropriate because of the generally lower diversity of mobile invertebrates and fish over seagrass communities and the opportunity it provided (in both a spatial and practical sense) for greater replication of transects within the seagrass habitat. 2.3 Literature review A variety of reports and databases were consulted to collect and collate existing information on the ecological features of a search area with 13 km radius centred between the three PTAAs, which provides a search area that includes all marine waters within 10 km of each PTAA and the proposed breakwater are included incorporates all the marine area incorporating the proposed breakwater and the PTAAs. Important sources of information included:
Atlas of Living Australia (ALA) records, which include records from the South Australian Museum, other museums, the State Herbarium, the Biological Database of South Australia and credible citizen science databases including iNaturalist. EPBC Act 1999 Protected Matters Search Tool (PMST) Regional summaries including The Natural History of Spencer Gulf (Shepherd et al. 2014) and Marine Assets of Yorke Peninsula (Baker 2015) SA Government environmental spatial datasets (e.g. DEW 2020c) Previous ecological studies (e.g. McDonald 2007, PB & SARDI 2002), and Spencer Gulf Prawn Fishery bycatch surveys (Currie et al. 2009, Burnell et al. 2015). Fishery assessment reports (Beckmann & Hooper 2019, Noell & Hooper 2019, Steer et al. 2020, Burnell et al. 2019).
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3 Results 3.1 Towed camera surveys 3.1.1 Proposed transhipment area alternatives The substrate within all three PTAAs was coarse sand with shell fragments and occasional pebbles, with a variable sparse cover of macroalgae of up to about 5% (Plate 1 to Plate 3). Macroalgal cover on most transects was <1% in the northern and south-eastern PTAAs, and 1–5% in the south- western PTAA. Across the 43 transects there were only a few, isolated sponges, ascidians or bryozoans, and no razor clams or mobile invertebrates or fish were observed. A number of transects in the south-eastern PTAA had a dense cover of sparse Halophila (equating to an overall cover of 5– 10%) (Plate 4, Figure 5).
Plate 1. Bare sediment with trace of macroalgae Plate 2. Bare sediment with about 1% cover of macroalgae
Plate 3. Bare sediment with about 5% cover of Plate 4. Bare sediment with cover of sparse macroalgae Halophila and 1–2% cover of macroalgae.
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Figure 5. Major habitat classes recorded on towed camera surveys in the proposed transhipment area alternatives.
3.1.2 Proposed breakwater The seafloor along the majority of the berthing section of the breakwater footprint was bare sand with a sparse (<5%) cover of mixed Posidonia sinuosa, Zostera nigricaulis and Halophila australis (Figure 6). In the southern corner of the berthing section, the seagrass transitioned to dense (>65%) Posidonia sinuosa and extended for about 70 m inshore along the causeway section before transitioning to reef, which was unbroken for about 80 m then interspersed with patches of dense Posidonia australis for about 120 m (Figure 6). There was a clear transition within the reef habitat after the first 30 m to reef dominated by the purple urchin Heliocidaris erythrogramma. Towed camera transects did not continue inshore from a shallow, sandy surf zone about 100 m from shore.
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Figure 6. Towed camera habitat points over the proposed causeway footprint. State benthic habitat boundaries and habitat descriptors (DEW 2020) are shown (in red) for comparison.
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3.2 Dive surveys Two 50 m transects were undertaken within reef habitat using the Reef Life Survey method (Section 2.2.1), and four 30 m transects within seagrass habitat (Section 2.2.2) (Figure 7).
Figure 7. Locations of dive transects within reef habitat (2 x 50 m) and seagrass habitat (4 x 30 m) with respect to towed camera habitat points. 3.2.1 Reef surv ys Continuous reef on Transect 1 (Figure 7), at a depth of 3.5 m, was dominated by a dense cover of e Sargassum sp. subgenus Sargassum with red filamentous macroalgal epiphytes, i.e. growing on the Sargassum (Plate 5). Understorey macroalgae include the ball coralline Jania microarthrodia, peacockweed Lobophora variegata (both Plate 6), Brown’s Caulerpa Caulerpa brownii (Plate 7) and the red lobed macroalga Peyssonnelia sp. The continuous reef was interspersed with patches of rubble that were generally unvegetated except for a patchy cover of encrusting coralline macroalgae (Plate 8). Sessile invertebrates included razor clam Pinna bicolor (Plate 9), hammer oyster Malleus meridianus and sponges with various colours and morphologies including yellow encrusting (Plate 10), yellow ball (Plate 11) and grey amorphous (Plate 12). The mobile invertebrate fauna included 1– 3 individuals of each of ten mollusc, crustacean and echinoderm species (Table 1), including some undersize greenlip abalone Haliotis laevigata. Four fish species (five individuals) from the fish and cryptic fish surveys, including little weed whiting Neoodax balteatus (Plate 5), southern cardinalfish Vincentia conspersa.
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Transect 2 (Figure 7), at a depth of 2.5 m, also had a dominant cover of Sargassum sp. subgenus Sargassum with red filamentous macroalgal epiphytes, with the large brown macroalga Caulocystis cephalornithos also present (Plate 13). The understorey species were similar to Transect 1, and areas of rubble, sponges, razor clams and hammer oysters were again present, along with the stony coral Plesiastrea versipora (Plate 14). The mobile invertebrate fauna was less diverse than Transect 1, and was dominated by the purple urchin Heliocidaris erythrogramma (Plate 15), at a density of 3/m2. The most common fish species was the little weed whiting, and there were incidental (off-transect) sightings of a dusky morwong Dactylophora nigricans, moonlighter Tilidon sexfasciatus and Shaw’s cowfish Aracana aurita, as well as a giant Australian cuttlefish Sepia apama. There were traces of Posidonia australis among the reef habitat, and inshore from Transect 2 there were patches of dense P. australis (Plate 16). 3.2.2 Seagrass surveys Seagrass survey transects were located haphazardly1 within the area of dense Posidonia sinuosa identified during the towed camera surveys (Figure 7). The depths of the four transects were 6.2, 6.5, 4.8 and 5.3 m, respectively. The seagrass fauna was dominated by sessile invertebrates including razor clam Pinna bicolor, mauve-mouthed ascidian Polycarpa viridis (Plate 17) and soft sponges (Plate 18). Epiphytic organisms (growing on seagrass blades) included the cryptogenic2 species Botryllus schlosseri (Plate 19). The mobile invertebrate fauna included 13 crustacean, mollusc or echinoderm species, including three incidental, off-transect observations (Table 2). The seagrass swimmer crab Nectocarcinus integrifrons (Plate 20), queen scallop Equichlamys bifrons (Plate 21) and abalone Haliotis spp. (Plate 22) were recorded on more than one transect.
1 i.e. not strictly random but located in such a way to emulate randomness. 2 i.e. uncertain origin, potentially introduced
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Table 1. Fauna recorded using Reef Life Survey method. F=fish survey, I/CF=invertebrate/cryptic fish survey.
Transect 1 Transect 2 Off- Species Photo Common name F I/CF F I/CF transect Crustaceans Nectocarcinus tuberculosus Red swimmer crab 3 3 Paguristes frontalis Southern hermit crab 1 1 Schizophrys aspera Red sea toad 1 Molluscs Ceratosoma brevicaudatum Short-tailed Ceratosoma 3 2 Haliotis laevigata Greenlip abalone 2 4 Haliotis scalaris Plate 22 Grooved abalone 3 Haliotis spp. Abalone undifferentiated 1 Pinna bicolor Plate 9 Razor clam 12 10 Pleuroploca australasia Plate 27 Sea tulip 2 Pterynotus triformis Fluted murex 1 Sepia apama Giant Australian cuttlefish 1 Echinoderms Australostichopus mollis Plate 28 Southern sea cucumber 1 1 Heliocidaris erythrogramma Plate 15 Purple urchin 3 303 Tosia australis Plate 25 Southern biscuit star 2 4 Fishes Aracana aurita Shaw’s cowfish 1 Brachaluteres jacksonianus Pygmy leatherjacket 1 Dactylophora nigricans Dusky Morwong 1 Eocallionymus papilio Painted stinkfish 1 Neoodax balteatus Plate 5 Little weed whiting 2 6 Nesogobius spp. Goby undifferentiated 2 Pempheris klunzingeri Rough bullseye 1 Tilodon sexfasciatus Moonlighter 1 Vincentia conspersa Southern cardinalfish 1
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Table 2. Fauna recorded during seagrass transects. Common names follow Edgar (2008).
Species Common name Photo S1 S2 S3 S4 Incidental Mean (s.e.) Echinoderms Australostichopus mollis Southern sea cucumber Plate 28 1 0.25 (0.25) Tosia australis Southern biscuit star Plate 25 1 0.25 (0.25) Uniophora nuda Bare seastar 1 - Crustaceans Naxia aurita Smooth seaweed crab Plate 24 1 - Nectocarcinus integrifrons Seagrass swimmer crab Plate 20 1 1 0.5 (0.29) Paguristes frontalis Southern hermit crab 1 0.25 (0.25) Molluscs Astralium sp. (A gastropod) 1 0.25 (0.25) Equichlamys bifrons Queen scallop Plate 21 1 1 0.5 (0.29) Doriopsilla carneola (A nudibranch) Plate 26 1 - Haliotis spp. (Abalone) 2 1 0.75 (0.48) Pinna bicolor Razor clam Plate 9 10 4 5 6 6.25 (1.31) Pleuroploca australasia Red whelk Plate 27 2 0.5 (0.50) Sessile invertebrates Ascidiacea sp. (A large ascidian) 1 0.25 (0.25) Polycarpa viridis Mauve-mouthed ascidian Plate 17 11 33 31 68 35.75 (11.84) Porifera sp. Sponge - hard 2 1 0.75 (0.48) Porifera sp. Sponge - soft Plate 18 4 3 6 10 5.75 (1.55) Tethya sp. Golf ball sponge 1 0.25 (0.25)
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Plate 5. Sargassum sp. Subgenus Sargassum with Plate 6. Ball coralline Jania microarthrodia (centre) red filamentous epiphytes. Grey amorphous and peacockweed Lobophora variegata. sponge to left, little weed whiting Neoodax balteatus near bottom centre.
Plate 7. Caulerpa brownii Plate 8. Rubble, including some pebbles covered with encrusting coralline macroalgae.
Plate 9. Razor clam Pinna bicolor Plate 10. Yellow encrusting sponge
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Plate 11. Yellow ball sponge Plate 12. Grey amorphous sponge
Plate 13. Brown macroalga Caulocystis Plate 14. Green coral Plesiastrea versipora cephalornithos
Plate 15. Purple urchin Heliocidaris erythrogramma Plate 16. Posidonia australis with brown filamentous epiphytes
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Plate 17. Mauve-mouthed ascidian Polycarpa Plate 18. Soft sponge viridis
Plate 19. Compound ascidian Botryllus schlosseri on Plate 20. Seagrass swimmer crab Nectocarcinus Posidonia sinuosa integrifrons
Plate 21. Queen scallop Equichlamys bifrons Plate 22. Grooved abalone Haliotis scalaris
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Plate 23. Bare sea star Uniophora nuda Plate 24. Smooth seaweed crab Naxia aurita
Plate 25. Southern biscuit star Tosia australis Plate 26. Nudibranch Doriopsilla carneola
Plate 27. Sea tulip Pleuroploca australasia Plate 28. Southern sea cucumber Australostichopus mollis
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3.3 Breakwater footprint habitat map The towed camera habitat point transitions from sparse mixed seagrass to dense Posidonia, and from the latter to reef, are not consistent with the State Benthic Habitat mapping by DEW (Figure 2, Figure 5). However, they are consistent with darkness transitions readily discernible3 from aerial imagery (Figure 5), and the transition from sparse to dense seagrass is consistent with a depth change from 5 to 4 metres below LAT (Figure 4). Boundaries between the three aforementioned habitat classes, have been inferred from the aerial imagery. It should be noted that there is a small (<20 m) offset between the habitats observed during the towed camera surveys and their representation as georeferenced habitat points, partly due to lag of the camera behind the towing vessel, and partly due to short delays in logging habitat transitions in the field. These issues could be addressed through post-field processing, but it is not considered necessary given the utility of the aerial imagery. The inshore transects showed patchiness in the reef and Posidonia australis habitat, and the towed camera points alone are not sufficient to infer habitat classes across the width of the causeway section of the breakwater (Figure 5). It was noted, however, that the patches of P. australis were dense and homogeneous, and these have been related to dark patches on the aerial photography. No attempt has been made to distinguish between reef and seagrass in the areas to the east and west of the causeway. The large area of nearshore/intertidal sand identified by DEW (Figure 5) was clearly discernible from the aerial imagery, and a thin band of intertidal reef was inferred from the darker area inshore from this sand on the aerial imagery, and from photographs by Bebbington (2015). The area of each habitat mapped within the breakwater footprint is summarised in Table 3 and an overall map of the vicinity of the breakwater footprint is provided in Figure 8.
Table 3. Area of habitats mapped with the proposed breakwater footprint
Habitat Area (hectares) Sparse mixed seagrass 1.2 Dense Posidonia sinuosa 0.6 Reef 0.7 Dense Posidonia australis 0.2 Sand 0.4 Intertidal reef 0.03
3 On a computer screen
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Figure 8. Habitat map of the area surrounding the proposed breakwater.
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3.4 Ecological values 3.4.1 Megafauna Marine mammals with records in the area include:
southern right whale Eubalaena australis, with SA Museum records near the coast between Point Riley and Warburto Point, from August 1987, July, September and October 1992 and June 2013 humpback whale Megaptera novaeangliae, with one SA Museum record from June 1992 at Point Riley, 6 km north of the proposed breakwater. long-nosed fur seal Arctocephalus forsteri, with one SA Museum record from September 2011 about 2.6 km north-east of the proposed breakwater. common dolphin Delphinus delphis, with five records during May to October between 1991 and 2000 near the coast between Point Riley and 2.5 km south of the proposed breakwater Indian Ocean bottlenose dolphin Tursiops aduncus, with five records during January 1989, September 2003 and April 2010 near the coast between Point Riley and Warburto Point The southern right whale is listed as Endangered Vulnerable under the EPBC Act 1999 and the South Australian National Parks and Wildlife Act 1972, and the humpback whale is listed as Vulnerable under both Acts. A number of other marine mammals and turtles were identified by the PMST as potentially occurring or having habitat in the search area, but for which there are no known records or important habitats in the study area, including: Bryde's whale Balaenoptera edeni pygmy right whale Caperea marginata dusky dolphin Lagenorhynchus obscurus Australian sea lion Neophoca cinerea Australian fur seal Arctocephalus pusillus loggerhead turtle Caretta caretta green turtle Chelonia mydas leatherback turtle Dermochelys coriacea 3.4.2 Macroalgae Macroalgal species with records in the search area are listed in Appendix A. Most records were from Bird Island, Point Riley, a location 10 km north-west of Point Riley, or beach-washed specimens within 0.5–2 km north of the proposed breakwater. There is a record from about 1 km north-east of the proposed causeway for the brown macroalga Dilophus angustus which is classified as Vulnerable by Cheshire et al. (2000) because there are less than five records of it. 3.4.3 Invertebrates Marine invertebrate species with records in the search area are listed in Appendix B. Most records were from Wallaroo Bay between Point Hughes and Point Riley, with a few records offshore from prawn bycatch surveys, including near the northern PTAA. There were no species listed under relevant legislation (see Section 4).
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3.4.4 Fishes and sharks Fishes and sharks with records in the search area are listed in Appendix C. Most were Museum Victoria records from a study in October 2005 at sites about 3.5 km north of the proposed breakwater. The PMST suggested that the Vulnerable white shark Carcharodon carcharias and migratory Porbeagle Lamna nasus or their habitat may be found in the search area. There was one record for white shark near Point Riley, about 6 north of the proposed breakwater. The PMST suggested that 25 species from the family Syngnathidae (sea horses, sea dragons and pipefish) or their habitat may be present in the search area. Syngnathids are all protected under the South Australian Fisheries Management Act 2007 and are Listed Marine species under the EPBC Act 1999. There is one ALA (iNaturalist) record of a pipefish from the genus Stigmatophora about 1.5 km north-east of the proposed breakwater. Many Syngnathids are associated with seagrass, and may be present within the proposed breakwater footprint, going undetected during the dive survey because of their cryptic nature. Beam trawls by McDonald (2007) in seagrass near Warburto Point, about 10 km south-west of the proposed breakwater, recorded eight Syngnathid species, of which the most common were spotted pipefish Stigmatopora argus, longsnout pipefish Vanacampus poecilolaemus, brush-tailed pipefish Leptoichthys fistularius and wide-bodied pipefish Stigmatopora nigra. 3.4.5 Seabirds and shorebirds The vast majority of records of marine birds and shorebirds within the search area are from Warburto Point and Bird Island Conservation Park, 8–10 km south-west of the proposed breakwater. These areas provide breeding habitat for a number of species including Sooty Oystercatcher Haematopus fuliginosus (listed as Rare under the National Parks and Wildlife Act 1972), Caspian Tern Hydroprogne caspia, Crested Tern Thalasseus bergii, Pied Cormorant Phalacrocorax varius, Little Pied Cormorant P. melanoleucos and Silver Gull Chroicocephalus novaehollandiae, and the Fairy Tern Sternula nereis (listed as Endangered under the National Parks and Wildlife Act 1972) has also been recorded there (Durant et al. 2019, Caton et al. 2006). Bird Island and Warburto Point also provide habitat for migratory shorebirds, including Ruddy Turnstone Arenaria interpres (listed as Rare under the National Parks and Wildlife Act 1972), Curlew Sandpiper Calidris ferruginea and Red-necked Stint C. ruficollis. 3.4.6 Marine pests Ten introduced species have been recorded at coastal locations within 20 km of the proposed breakwater (Wiltshire et al. 2010, iNaturalist 2020) (Table 4). These include two pest species of most concern within South Australia (PIRSA undated a), namely the European fan worm and vase tunicate, the former of which has also been declared ‘noxious’ under the Fisheries Management Act 2007 (PIRSA 2019). Other than the species found near the coast (Table 4), no introduced species have been recorded within 50 km of the PTAAs.
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Table 4. Introduced species near the proposed breakwater. Locations Point Wallaroo Moonta Port Species Common name Riley Jetty Bay Hughes Alexandrium tamarense (a microalga) Y Ulva lactuca Broadleaf sea lettuce Y Amathia verticillata Spaghetti bryozoan Y Schizoporella errata Branching bryozoan Y Sabella spallanzanii European fan worm Y Mytilus galloprovincialis Blue Mussel Y Pinctada sugillata Pearl oyster Y Ciona robusta Vase tunicate Y Botrylloides leachii Ladder ascidian Y Y Y Botryllus schlosseri Star ascidian Y
3.5 Fisheries and Aquaculture The main fisheries in mid Spencer Gulf are the Spencer Gulf Prawn Fishery, Blue Crab Fishery (Spencer Gulf Zone), Central Zone Abalone Fishery and the Marine Scalefish Fishery. The seagrass, unvegetated soft bottom and tidal flats within a 50 km section of coast extending from north of Point Riley to Cape Elizabeth collectively provide habitat, including spawning and nursery grounds that support these fisheries, for a range of species including King George whiting, snapper, western Australian salmon, Australian herring, southern sea garfish, southern calamary, blue swimmer crab, western king prawn and razor clams (Bryars 2003). Food chains of the offshore prawn and crab fisheries in the nutrient-poor waters of South Australia are generally based on detritus, including that exported offshore from shallow water seagrasses. There are also zones allowing aquaculture in deep (>15 m) areas with relatively high current flow that are considered suitable for both finfish and subtidal shellfish aquaculture (PB & SARDI 2003, PIRSA 2017). 3.5.1 Spencer Gulf Prawn Fishery The Spencer Gulf Prawn Fishery (SGPF) has 39 licence holders. The target species is the western king prawn Melicertus latisullcatus. Commercial catches are reported for spatial blocks spanning 30–1000 km2, which are grouped into fishing regions. The PTAAs are within Block 45 of the Wallaroo region (Figure 9), which is one of three regions that have collectively accounted for 63–84% of the annual total SGPF harvest since 1990/91 (Noell & Hooper 2019). The Wallaroo region accounted for about
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32% and 44% of the total SGPF harvest during the 2016/17 and 2017/18 fishing seasons, and Block 45 accounted for 2–6% of the total SGPF harvest in 2016/17 and 2–10% in 2017/184. The areas of most importance to the fishery can be inferred from their footprint during 2001–2018, and suggests that the PTAAs may be within an area of moderate historical fishing intensity (Figure 10). Surveys of prawns have been undertaken twice each year to measure prawn biomass and inform fishing strategies (Noell et al. 2019). A number of these overlap with the south-eastern and south- western PTAAs (Figure 9). Bycatch surveys were undertaken in 2007 and/or 2013 (Currie et al. 2009, Burnell et al. 2015), but outside the PTAAs (Figure 9).
Figure 9. Spencer Gulf Prawn Fishery catch reporting blocks, prawn survey sites and bycatch survey sites near the proposed breakwater and PTAAs.
4 Note that the estimated range for the 2016/17 year assumes that the pre-Christmas catch (confidential for Block 45) is similar to 2017/18. It would be possible to make a data request, at some expense, for more precise and accurate annual catches from Block 45.
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Figure 10. Spencer Gulf Prawn Fishery footprint, based on 40% of the total effort during 2001/02–2017/18. Source: Noell et al. 2019. 3.5.2 Blue crab fishery The Spencer Gulf Sector (SGS) of the commercial Blue Crab Fishery has four licence holders. Commercial catches are reported to PIRSA for spatial blocks typically spanning about 160 km2 unless truncated by the coastline, but have only been published as ranges at that scale (Beckmann & Hooper 2019)5. The northern and south-western PTAAs and a sliver of the south-eastern PTAA are within Block 41, and the south-eastern PTAA is largely within Block 42, which has an area of 120 km2 (Figure 11). In 2017/18, Block 41 accounted for 0–3% of the total harvest of the SGS, the lowest catch for the past decade for that block, from which harvest had been up to 16–21% of the total harvest for the SGS. In 2017/18, Block 42 accounted for 6–11% of the total harvest of the SGS, which was the highest for that block for the past decade (Beckmann & Hooper 2019). Fishery independent surveys are undertaken annually during winter at 60 sites within Spencer Gulf. Two of those sites appear to be within the south-eastern PTAA (Figure 11, Figure 12).
5 More precise annual catches for Blocks 41 and 42 may be obtainable, at a cost, by request to SARDI.
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Figure 11. Blue Crab Fishery catch reporting blocks near the proposed breakwater and PTAAs.
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Figure 12. Locations of Blue Crab Fishery survey locations in Spencer Gulf. Source: Beckmann & Hooper 2019.
3.5.3 Marine Scalefish Fishery The Marine Scalefish Fishery allows harvest of more than 60 species including fish, sharks, molluscs, crabs and worms by more than 300 licence holders throughout South Australian marine waters using a variety of methods including hauling nets, handlines, longline and squid jigs. The main species, collectively accounting for 60% of the fishery by weight and 70% by value, are King George whiting Sillaginodes punctata, southern sea garfish Hyporhamphus melanochir, southern calamary Sepioteuthis australis and Snapper Chrysophrys auratus (Steer et al. 2020), although the latter is the subject of a three year closure established in November 2019. The spatial distribution of catches is reported using relatively large fishing blocks. The PTAAs and proposed breakwater are towards the southern end of Block 23, which covers almost 2,200 square kilometres (Figure 13).
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In 2018 this block yielded 6–25 t each of King George whiting, Australian salmon Arripis truttacea and yelloweye mullet Aldrichetta forsteri, 10–35 t of snapper, 26–50 t each of garfish, calamary, yellowfin whiting Sillago schomburgkii and snook Sphyraena novaehollandiae, and 51–75 t of Australian herring Arripis georgeana. The catches for mullet, snook and herring were the largest in the state (Steer et al. 2020). 3.5.4 Central Zone Abalone fishery The Central Zone Abalone Fishery allows harvest of greenlip abalone Haliotis laevigata and blacklip abalone H. rubra from an area extending from Tumby Bay on eastern Eyre Peninsula to the Murray Mouth, including the waters surrounding Kangaroo Island (PIRSA 2012). Reporting of catches for the fishery is based on fishing blocks of variable area, which are amalgamated into spatial assessment units (SAUs) that are intended to reflect distinct abalone populations. The proposed breakwater and the PTAAs are at the northern end of the Cape Elizabeth SAU (Figure 14).There has been negligible (0.05 tonnes total) blacklip catch from the Cape Elizabeth SAU since 2000, but it has accounted for <2 tonnes of the annual greenlip catch during 2014–2018, and 4–5 tonnes during 2010–2013, with an overall contribution of 4.9% of the total catch during 2009–2018 (Burnell et al. 2019). The PTAAs do not provide any suitable habitat for abalone. Six greenlip abalone below the minimum harvest size limit were recorded during surveys of reef within the proposed breakwater footprint of the causeway (Table 1), which indicates that this site would not be a commercially viable abalone fishing ground. It should be noted that most of the greenlip catch for this fishery comes from the Tiparra Reef SAU, which is within the Cape Elizabeth SAU and about 9 km south of the PTAAs and West Yorke Peninsula SAU, south of the Cape Elizabeth SAU (Figure 14), with about 34% and 25% of the total catch during 2009–2018, respectively (Burnell et al. 2019).
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Figure 13. Marine Scalefish Fishery catch reporting blocks near the proposed breakwater and PTAAs.
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Figure 14. Central Zone Abalone Fishery Spatial assessment units (SAUs) near the proposed breakwater and PTAAs.
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3.5.5 Aquaculture Aquaculture at Wallaroo is managed under the Aquaculture (Zones – Eastern Spencer Gulf) Amendment Policy 2017 (PIRSA 2017). This provides for areas near Wallaroo that exclude aquaculture, including the proposed breakwater, and two areas deemed suitable for aquaculture (Figure 15). The Wallaroo (West) subtidal aquaculture zone allows for filter feeding organisms and algae, and the Wallaroo (East) subtidal aquaculture zone allows for the same as well as aquaculture activity involving the use of supplementary feed, including finfish (but not tuna). There are currently three 50 ha sites licensed to farm blue mussel Mytilus galloprovincialis within the Wallaroo (East) subtidal aquaculture zone (Figure 15), but no farming has occurred on these sites since 2011 as the mussels farmed did not yield the growth results that were expected and necessary to make it a profitable aquaculture venture (PIRSA 2017). There is also a 20 ha lease to the east of the zone (Figure 15),
Figure 15. Aquaculture zones and leases/licences near Wallaroo. Source: PIRSA 2020.
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4 Impact Assessment The following potential impacts of the project on the marine environment at Wallaroo include: Direct loss of seagrass and reef habitat due to breakwater construction Indirect impacts on habitats from construction activities Indirect impacts on habitats from sedimentation arising from changed coastal processes Indirect impacts on seagrass from propeller wash Direct loss of seagrass from anchoring in a transhipment area Introduction of marine pests Noise from piling and vessels (construction and operation) Vessel interactions with marine megafauna 4.1 Direct loss of habitat from breakwater construction Construction of the proposed breakwater would result in the loss of about 0.7 ha of macroalgae- covered reef, 0.2 ha of dense Posidonia australis seagrass, 0.6 ha of dense P. sinuosa seagrass, and about 1.2 ha of sparse (1-5% cover) seagrass (Table 3). Although some mobile species may successfully relocate during construction, the loss of invertebrates and the more sedentary fish, including a number of Syngnathid species, is expected. It is considered that the loss of reef or seagrass habitat would have negligible impact on associated fauna populations because it represents a very small proportion of the available habitat in the region. The proposed breakwater is within an area of tens of thousands of hectares of seagrass (Figure 3). Reef habitat extends along the coast for more than 5 km to the south and north from Point Riley, and there are more than 5000 ha of reef south of Cape Elizabeth (Figure 3). The breakwater structure would provide artificial reef habitat which, despite not having exactly the same characteristics as the displaced reef, would provide habitat supporting increased production of reef fauna and would also increase the extent of reef/seagrass ecotone habitat. The loss of seagrass during construction would require a significant environmental benefit (SEB) offset under the provisions of the Native Vegetation Act 1991 and Native Vegetation Regulations 2017, which could be in the form of a payment to the Native Vegetation Fund. A more detailed assessment is required to determine the required payment, but expected ranges and indicative values are provided in Table 5, and suggest an indicative value of $55,000 as total payment into the fund.
Table 5. Indicative SEB offset payments in the Native Vegetation Fund
Seagrass community Area SEB offset expected SEB offset (hectares) cost range indicative cost Sparse mixed seagrass 1.2 $24,800–60,800 $32,800 Dense Posidonia sinuosa 0.6 $7,100–33,800 $15,700 Dense Posidonia australis 0.2 $5,700–$13,900 $6,500 Total $55,000
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4.2 Indirect impacts on habitats during breakwater construction Disturbance to or addition of sediment during construction could result in impacts on surrounding seagrass communities through light reduction or sedimentation, and reef communities may also be impacted by sedimentation. A monitoring program would be established to quantify any impacts on seagrass extent or reef fauna in the relevant areas, and an additional SEB offset would be applied in the event of further seagrass loss. 4.3 Indirect impacts on habitats due to changed coastal processes Sand is predicted to accumulate on the western side of the breakwater at a rate of 9,750 m3/year, and on the eastern side of the breakwater (due to a reversal of the longshore sediment transport), at a rate of 1,400 m3/year (Cardno 2020). This may result in smothering of seagrass and reef habitat. Sand is also predicted to slowly recede to the east of the harbour, with a potential net deficit of about 10,000 m3/year. Reduction in sand supply offshore could result in loss of Posidonia australis habitat amongst reef patches in the area. A monitoring program would be established to quantify any impacts on seagrass extent or reef fauna in the relevant areas, and an additional SEB offset would be applied in the event of further seagrass loss. 4.4 Impacts on seagrass from operations at the breakwater Propeller wash during operation (particularly the departure of laden vessels) may result in winnowing of sediment from the seafloor and subsequent indirect impacts on seagrass though light reduction or scouring. There is also the potential for cascading impacts from erosion at the face of seagrass meadows. A monitoring program would be established to quantify any impacts on seagrass extent near the berthing area, and an additional SEB offset would be applied in the event of further seagrass loss. 4.5 Impacts on benthic habitats from transhipment point operations Anchoring of bulk-carrier vessels at defined transhipment points and associated dragging of chains would disturb areas that are predominantly bare sand, with only sparse (<5%) cover of macroalgae at all PTAAs, and the seagrass Halophila at the south-eastern PTAA (Figure 5). The area impacted would be reduced to a radius of a few hundred metres if anchoring occurred consistently at the midpoint of the PTAA. The Halophila seagrass recorded at the south-eastern PTAA extends for at least several kilometres to the south (Figure 2). Halophila is a colonising/ephemeral species characterised by short turnover times and early sexual maturity (within months), with low resistance to disturbance but ability to recover rapidly, assisted by a seed bank (Kilminster et al. 2015). There may therefore be opportunities for Halophila to re- establish during the winter period when the transhipment point is not used. Transhipment vessels would not anchor but would be tethered to the larger vessel during unloading, and no physical or permanent structures would be constructed at the transhipment locations.
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4.6 Introduction of marine pests The most common vectors of marine pests are ballast water and biofouling of vessel hulls (Hewitt & Campbell 2010), but other marine infrastructure used during construction such as anchors and mooring lines can also act as vectors. Introduced marine species can rapidly multiply after a disturbance, removal of competitive indigenous species, or provision of unoccupied hard surfaces, such as the proposed breakwater. More than 250 introduced marine species have been recorded in Australia (DAWE 2020a), including 49 species in Spencer Gulf (Wiltshire et al. 2010, Dittman et al. 2010, iNaturalist 2020). Some introduced species may have adverse effects on native species, through predation, competition, or displacement or by carrying disease, and are referred to as introduced marine pests (DAWE 2020a). Ten introduced species were recorded within 20 km of the proposed breakwater, including two priority pest species, the European fan worm Sabella spallanzanii and vase tunicate Ciona robusta, both recorded at Wallaroo Jetty and/or Marina, 1–2 km to the north (Section 3.4.6). The vase tunicate is not likely to spread by larval dispersal (Petersen & Svane 1995). European fan worm larvae been found to disperse distances up to 20 km in Port Phillip Bay in Victoria, and could settle on the proposed breakwater, but would be unlikely to establish outside the relatively sheltered bays (Currie et al. 2000). New incursions of species such as the Northern Pacific sea star Asterias amurensis could result in degradation of habitat on a broader scale, as has occurred in the Derwent River and Port Phillip Bay (Parry 2001). A range of mitigation measures, including all obligations under the Biosecurity Act 2015, would reduce the likelihood of such new incursions. In particular, ships would comply with the Australian Ballast Water Management Requirements (DAWR 2020b), which include discharge of ballast water before entering Australian waters. The TSV(s) would take on ballast at the transhipment location and dispose of this water at the wharf, effectively only bringing Gulf waters into the harbour which already has the potential to occur through natural mixing processes. 4.7 Underwater noise The primary noise source would be impact piling of up to eight piles and sheet piling along the berthing area during construction, and there would be noise associated with the movement of various vessels during construction and the TSV(s) during operation. The noise associated with impact piling is impulsive in character with multiple pulses occurring from impacts at a rate of 30 to 60 per minute, generally at low frequencies, i.e. between 100 Hz and 1 kHz (DPTI 2012). Each pulse typically occurs over about 0.1 seconds for 90% of the impact sound energy, but sound levels can be expressed as a sound exposure level (SEL) which standardises the sound exposure duration to a period of one second. SELs for piling are typically in the range 170–225 dB6. Factors that influence the source level include the size, shape, length and material of the pile, the weight and drop height of the hammer, and the seabed material and depth (DPTI 2012). The continuous SEL, resulting from exposure to multiple blows, increases the sound level by 10 times the logarithm of the number of blows, which could be up to 30 dB in a typical day of piling. Noise thresholds to protect various marine fauna groups from hearing loss have been determined (DPTI 2012, Resonate 2018, NOAA 2018, Popper et al. 2014). The most sensitive group is baleen
6 re 1μPa at 1 m
39 Wallaroo Marine Ecological Assessment, October 2020 whales, including humpback and southern right whales, which are susceptible to low frequency sound and can be exposed to temporary or permanent hearing loss at sound levels of 168 dB and 183 dB, respectively. Most fauna groups, including fish, turtles, eared seals (including the Australian sea-lion) and dolphins would also be exposed to hearing loss near the noise source, but the noise level reduces by a factor of 15–25 times the logarithm of the distance (DPTI 2012). Modelling for other projects has shown that fauna groups are typically safe from hearing loss within tens or perhaps hundreds of metres from a typical day of impact piling activity, with the exception of baleen whales which may require a distance of the order of kilometres (e.g. Resonate 2018). For hearing loss to occur within the predicted safe distances, the affected fauna would need to remain within those distances for the full duration of the piling activity. However, the fauna groups assessed are generally quite mobile and likely to move a sufficient distance from the piling activity to prevent hearing loss. Such behavioural changes are not considered to have a significant impact on these species, as none of them rely on the study area for important ecological processes such as breeding or feeding. A range of mitigation measures, consistent with the South Australian Underwater Piling Noise Guidelines (DPTI 2012) and conditions imposed on other projects (e.g. DEE 2018) could be adopted to reduce the risk to baleen whales:
Piling between November and April when baleen whales are unlikely to be present. Soft-start, whereby piling impact energy would be gradually increased over a 10 minute time period at the commencement of piling (or after a break of more than 30 minutes), alerting marine fauna to the piling operations and enabling them to move away to distances where injury is unlikely. Pile type selection, e.g. the use of concrete piles. Bubble curtains. The pile would be encircled by bubbles from air streaming from closely spaced release points encircling the pile. Safety zones (a Shutdown Zone buffered by an Observation Zone) which would be searched prior to commencement of piling by a suitably trained observer and monitored thereafter, with piling to cease if the relevant fauna were observed. The radius of the Shutdown Zone is 100–1000 m depending on the noise level that the relevant species are exposed to (DPTI 2012) but could be refined through modelling. With the adoption, where appropriate, of the above management measures, the distances required to achieve protection from the piling noise would be short relative to the mobility of the species, therefore piling would have a negligible impact on marine fauna including baleen whales, sharks and turtles. Sound pressure levels associated with different vessel types are highly variable but can reach 190 dB, at a range of frequencies. Sound pressure levels would drop by about 10, 20, 30 and 40 dB within distances of 3, 10, 30 and 100 metres, respectively (URS 2011). Published thresholds for hearing loss from continuous noise show that all fauna groups suggest that permanent hearing loss (and injury or mortality) would not occur below a cumulative sound exposure level of 199 dB, and temporary hearing loss would not occur below 180 dB (URS 2011, Resonate 2018). Therefore, permanent hearing loss (or worse) would not occur at the source and temporary hearing loss would not occur
40 Wallaroo Marine Ecological Assessment, October 2020 beyond a few metres from the source. As for piling noise, there would likely be behavioural responses which would help to prevent acoustic trauma but otherwise be of little consequence. 4.8 Vessel interactions with marine megafauna Marine mammals are considered to be the most likely fauna to be impacted by vessel collision due to their need to surface to breathe. Dolphins and seals are considered to be less susceptible to vessel strikes than whales due to their greater mobility, but dolphins tend to investigate or bow ride vessels (DEWNR 2007). Although all types and sizes of vessels may hit whales, most lethal and serious injuries to whales are caused by relatively large vessels, including bulk carriers (Laist et al. 2001). For most Australian reports of vessel strikes with whales, the species was unknown, but otherwise the humpback and southern right whale (SRW) were most commonly reported. SRWs are considered vulnerable to vessel strike due to their presence in near-shore waters during critical life phases such as calving, slow swimming behaviour and time spent on the surface (DEE 2016).There have been four recorded SRW strikes within South Australian waters, outside of Spencer Gulf, of which two or three were fatal (Kemper et al. 2008, Spencer Gulf Ports Link 2013, IWC 2020). An SRW carcass was found at Tumby Bay and the cause of death attributed to a vessel strike, but it was not certain that the strike had occurred in Spencer Gulf (Iron Road 2015). Despite the obligation under the EPBC Act 1999 to report any collisions that may result in a cetacean being injured or killed, it is likely that some go undetected or are not reported (DEE 2016). It is reasonable to assume that the incidence is low given the very low number of dead or injured whales reported along the South Australian coastline, but it is nevertheless difficult to reach conclusions on the rate of vessel strike in Australia based on incomplete and potentially biased data (Peel et al. 2016). A preferable approach is to relate the risk to densities of vessels and whales (IWC 2020). Bulk carrier shipping routes within Spencer Gulf are confined mainly to deeper channels (Figure 17). Southern right whales during their winter migration generally occupy shallow sheltered bays within 2 km of shore and within water depths of less than 10 m (Charlton 2017). Records within Spencer Gulf also provide evidence of this coastal affinity (Figure 16). Cape and Panamax ships are expected to slow to around 11 knots as they enter Spencer Gulf (Iron Road 2014). Laist et al. (2001) found that 89 per cent of collision accounts in which whales were killed or seriously injured involved vessels moving at 14 knots or faster.
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Figure 16. Atlas of Living Australia records of southern right whales in South Australia and near Wallaroo. Source: ALA (2019).
There were about 360 large (>80 m) vessel calls to the existing ports and transhipment points at Whyalla, Port Pirie, Port Bonython and Wallaroo in 2012, with the number expected to triple by 2020 (Bailey et al. 2012), but more recent statistics suggest a total of about 250, including 81 and 6 from Port Pirie and Wallaroo, respectively (Flinders Ports 2019) and 48 and 112 from Port Bonython and Whyalla, respectively (pers. comm., Brendan Curtis, OMC International). In addition to ships, the waters of Spencer Gulf are used by a number of smaller commercial boats (including barges) and some proportion of about 50,000 recreational vessels registered annually in South Australia (DPTI 2015). The project would involve 6–7 bulk carrier vessel calls at Wallaroo, with a seasonal bias towards harvest time (summer) rather than whale migrations (winter). The overall number of bulk carrier calls for grain export from South Australia (which is determined by the size of the harvest) would be unchanged, but there may be a net increase in bulk carrier vessels to Wallaroo and perhaps to Spencer Gulf (transferred from Gulf St Vincent). There would also be approximately 15 TSV movements associated with each vessel call at Wallaroo, but these are unlikely to have a significant impact on SRWs which rarely visit the area, as demonstrated by the following two datasets:
The Atlas of Living Australia includes about 3000 South Australian southern right whale sighting records totalling more than 12,000 individuals, mainly sourced from the SA Museum (Atlas of Living Australia 2019). About 65 per cent of the sightings and 80 per cent of the individuals were recorded in the aggregation areas identified above. The remaining sightings
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were spread along the coastline, including about 200 records in Spencer Gulf, north of Port Lincoln (Figure 16). SA Museum records at Wallaroo (between Bird Island and Point Riley) are from August 1987 (one individual about 2 km north-east of the proposed causeway), July, September and October 1992 (social group of four) and June 2013 (one individual).
The South Australian Whale Centre has maintained a log of sightings by community members since 1997 (SA Whale Centre 2019). It has logged about 3000 sightings across the state, but there is an obvious reporting bias, with more than 80 per cent of these sightings from Encounter Bay, where the Whale Centre is based. Nevertheless, there have been 60 sightings reported from Spencer Gulf, of which eight were from the eastern coast. The closest sighting north of the proposed causeway was at Tickera Point (13 km north) in August 1997 and beyond that three sightings near Port Augusta, the most recent being in 2010. To the south there were four sightings around the foot of the Peninsula (>100 km away) during winter 1998, 1999, 2003 and 2005. It is concluded that the additional vessel movements may result in a marginal increase in the likelihood of whale collision within Spencer Gulf, but not to an extent that would impact on populations.
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Figure 17. Shipping routes in and adjacent to Spencer Gulf, based on received Automatic Identification System data. Source: Izzo & Gllanders (2015), using data from www.marinetraffic.com.
4.9 Impacts on birds There are few records of seabirds or shorebirds near to the proposed breakwater, and it is not known to be significant bird habitat. The nearest significant bird habitat, at Bird Island and Warburto Point, 8–10 km south-west of the proposed breakwater, would not be affected by its construction or operation.
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4.10 Impacts on fisheries and aquaculture The project would have negligible impact on inshore habitats used by various life stages of fished species, due to the small footprint of the project relative to the extent of these habitats in central Spencer Gulf (Section 4.1). The PTAAs are likely to have been previously fished by the Marine Scalefish, Blue Crab and Spencer Gulf Prawn Fisheries. Licence holders in these fisheries would be unable to operate within the selected transhipment area while bulk-carriers are anchored. However, no measurable impact on annual catches or costs are expected, because the area is small relative to the scale of the fishery, and the restrictions are temporary. Similarly, the loss of a small area of inshore reef and seagrass is not expected to have a measurable impact on licence holders of the Marine Scalefish Fishery. Use of the south-eastern or south-western PTAAs could potentially impede prawn surveys in spring and autumn, but use of the south-western PTAA would probably not impede crab surveys which occur in winter. There is no suitable habitat for the Central Zone Abalone Fishery within the PTAAs, and the inshore reef area does not support commercially viable populations of abalone. The PTAAs are situated offshore from the Wallaroo (West) and Wallaroo (East) subtidal aquaculture zones, and transhipping operations would not have any impact on aquaculture operations within those zones. Most of the south-eastern PTAA lies within an aquaculture exclusion zone. 5 Conclusions The project would result in the direct loss of a very small fraction of the total seagrass and reef habitat in the region. The loss of seagrass habitat would be offset by a payment of $55,000 (a preliminary estimate that could potentially be doubled). The loss of reef habitat would be offset to some degree by the artificial reef provided by the breakwater. There may be additional local indirect losses of seagrass during construction and operation of the breakwater, through turbidity and sedimentation, which may require additional offsets once the extent has been quantified. Use of the south-eastern PTAA would likely result in the loss of Halophila seagrass. Other impacts from the project, including underwater noise, introduced pests and interactions with marine megafauna can be minimised through the adoption of various management measures. The project is not expected to impact the sustainability, annual catches or operational costs of commercial fisheries in the region, but the use of the south-western and south-eastern PTAAs would potentially impact stock assessment surveys for the Spencer Gulf Prawn Fishery.
45 Wallaroo Marine Ecological Assessment, October 2020
6 References Atlas of Living Australia (2019), Eubalaena australis (Desmoulins, 1822) southern right whale, viewed 18 February 2019,
46 Wallaroo Marine Ecological Assessment, October 2020
Currie, D.R., Dixon, C.D., Roberts, S.D., Hooper, G.E., Sorokin, S.J. and Ward, T.M. (2009). Fishery- independent by-catch survey to inform risk assessment of the Spencer Gulf Prawn Trawl Fishery Report for PIRSA Fisheries (pp. 121). South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2009/000369 1. SARDI Research Report Series No. 390. 121pp. DAWE (2020a), Marine Pests, Department of Agriculture, Water and the Environment, Australian Government, Canberra, viewed 16 May 2020, http://www.agriculture.gov.au/pests-diseases- weeds/marine-pests. DAWE (2020b), Australian Ballast Water Management Requirements, Version 8, Department of Agriculture, Water and the Environment, Australian Government, Canberra. DEE (2016), Draft National Strategy for Mitigating Vessel Strike of Marine Mega-fauna, Department of the Environment and Energy, Commonwealth of Australia, Canberra. DEE (2018), Notification of REFERRAL DECISION - not controlled action if undertaken in a particular manner Port Adelaide Outer Harbor Channel Widening Project, SA (EPBC 2017/8033). Department of the Environment and Energy, Canberra, ACT. DEW (2020a), EGIS data: Marine Benthic Habitats, viewed September 2020, http://location.sa.gov.au/lms/Reports/ReportMetadata.aspx?p_no=1224&pu=y&pa=dewnr. Department for Environment and Water, Adelaide, South Australia. DEW (2020b), EGIS data: Benthic Habitat Survey Sites, viewed September 2020, http://location.sa.gov.au/lms/Reports/ReportMetadata.aspx?p_no=1234&pu=y&pa=dewnr. Department for Environment and Water, Adelaide, South Australia. DEW (2020c), EGIS data: State Marine Benthic Habitats, viewed September 2020, http://location.sa.gov.au/lms/Reports/ReportMetadata.aspx?p_no=1233&pu=y&pa=dewnr. Department for Environment and Water, Adelaide, South Australia. DEWNR (2007), Adelaide Dolphin Sanctuary – Reference Paper 1: Dolphins, Department of Environment, Water and Natural Resources, Government of South Australia Dittman, S, Cameron, S & Conlon, K (2010), Increasing knowledge on introduced species in the marine environments of the Eyre Peninsula. Report to the Eyre Peninsula Natural Resources Management Board. DPTI (2012), Underwater Piling Noise Guidelines, Department of Planning, Transport and Infrastructure, Government of South Australia, Adelaide.
DPTI (2015), Boat Registrations, viewed June 2015, https://data.sa.gov.au/dataset/boat- registrations. Department of Planning, Transport and Infrastructure. Adelaide. DSEWPaC (2012), Conservation Management Plan for the Southern Right Whale: A Recovery Plan under the Environment Protection and Biodiversity Conservation Act 1999 2011–2021, Department of Sustainability, Environment, Water, Population and Communities, Canberra. Durant M, Ling H, and Hope F (2019), Northern and Yorke Coastal Management Action Plan, Legatus Group and Greening Australia, report to Natural Resources Board, Northern and Yorke, Clare. Edgar, GJ (2008), Australian Marine Life – The Plants and Animals of Temperate Waters, 2nd Edition, New Holland, Sydney.
47 Wallaroo Marine Ecological Assessment, October 2020
Edyvane, K (1999), Conserving Marine Biodiversity in South Australia Part 2, Identification of Areas of High Conservation Value in South Australia, SARDI Report Number 39, PIRSA, F2007/000565-9. SARDI Research Report Series No. 816. Flinders Ports (2019), Annual Summary Report, viewed April 2020, http://www.flindersports.com.au/portstatistics3.html Flinders Ports (2020), Wallaroo T-Ports Proposed Common User Export Facility Soundings. Gaylard, S, Nelson, M & Noble, W (2013), Nearshore Marine Aquatic Ecosystem Condition Reports – Lower Spencer Gulf bioregional assessment report 2010. Environment Protection Authority, Adelaide. Hewitt, CL & Campbell, ML (2010), The relative contribution of vectors to the introduction and translocation of marine invasive species, Report for the Department of Agriculture, Fisheries and Forestry, the National Centre for Marine Conservation and Resource Sustainability, Australian Maritime College, University of Tasmania, Launceston. iNaturalist (2020), Introduced marine species in South Australia's Journal. https://www.inaturalist.org/projects/introduced-marine-species-in-south-australia, viewed 16 June 2020
Iron Road (2014), Central Eyre Iron Project Infrastructure Environment Protection and Biodiversity Conservation Act 1999 (Cth). Referral to Australian Government. Iron Road (2015), Central Eyre Iron Project Environmental Impact Statement. IWC (2020), Ships strike database. International Whaling Commission. https://portal.iwc.int Izzo, C and Gillanders BM (2015), Spencer Gulf Ecosystem and Development Initiative. Interactions between whales and vessels: causes and mitigation options – with reference to southern Australia. Report to the Board of the Spencer Gulf Ecosystem and Development Initiative. February 2015. Kemper, C, Coughran, D, Warneke, R, Pirzl, R, Watson, M, Gales, R & Gibbs, S (2008), Southern right whale (Eubalaena australis) mortalities and human interactions in Australia 1950–2006’, Journal of Cetacean Research and Management, vol. 10, no. 1, pp. 1–8. Kilminster, K, McMahon, K, Waycott, M, Kendrick, GA, Scanes, P, McKenzie, L, O'Brien, KR, Lyons, M, Ferguson, A, Maxwell, P, Glasby, T and Udy J (2015), ‘Unravelling complexity in seagrass systems for management: Australia as a microcosm’, Science of the Total Environment 534:97–109 Laist DW, Knowlton AR, Mead JG, Collet AS and Podesta M (2001) Collisions between ships and whales, Marine Mammal Science 17(1): 35-75 McDonald, B (2007), The influence of seagrass habitat architecture and integrity on associated faunal assemblages, PhD thesis, School of Biological Sciences, Faculty of Science and Engineering, Flinders University. Miller, D., Westphalen, G., Jolley, A. M. and Eglinton, Y.(2009). Marine Habitats of the Northern and Yorke NRM Region. Final Report to the Northern and Yorke Natural Resources Management Board for the project: Sustaining Marine Biological Health. Prepared by the Department for Environment and Heritage, Coast and Marine Conservation Branch. NOAA (2018). 2018 Revisions to: Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 2.0): Underwater Thresholds for Onset of Permanent
48 Wallaroo Marine Ecological Assessment, October 2020 and Temporary Threshold Shifts. U.S. Dept. of Commer., NOAA. NOAA Technical Memorandum NMFS-OPR-59, 167 p. National Marine Fisheries Service. Noell, C. J. and Hooper, G. E. (2019). Spencer Gulf Prawn Penaeus (Melicertus) latisulcatus Fishery. Fishery Assessment Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2007/000770-10. SARDI Research Report Series No. 1029. 60pp. Parry, GD (2001), The distribution, abundance and population dynamics of the exotic seastar Asterias amurensis during the first three years of its invasion of Port Phillip Bay. Technical Report, Marine and Freshwater Research Institute, Victoria. Peel, D, Smith, JB & Childerhouse, S (2016), Historical data on Australian whale vessel strikes, presented to the IWC Scientific Committee, SC/66b/HIM/05. Petersen JK, Svane I (1995). Larval dispersal in the ascidian Ciona intestinalis (L.): Evidence for a closed population. Journal of Experimental Marine Biology and Ecology 186: 89–102. PIRSA (2012), Management Plan for the South Australian Commercial Abalone Fishery. Adelaide. Primary industries and Regions South Australia Fisheries and Aquaculture, 85pp. PIRSA (2013), Management Plan for the South Australian Commercial Marine Scalefish Fishery. PIRSA Fisheries and Aquaculture, Adelaide, 143pp. The South Australian Fishery Management Series, Paper No. 59. PIRSA (2017), Report Supporting the Aquaculture (Zones – Eastern Spencer Gulf) Amendment Policy 2017. Primary Industries and Regions, South Australia. Popper, A. N., Hawkins, A. D., Fay, R. R., Mann, D. A., Bartol, S., Carlson, T. J., Coombs, S., Ellison, W. T., Gentry, R. L., Halvorsen, M. B., Løkkeborg, S., Rogers, P. H., Southall, B. L., Zeddies, D. G. and Tavolga, W. N. (2014). ASA S3/SC1.4 TR-2014 Sound Exposure Guidelines for Fishes and Sea Turtles: A Technical Report prepared by ANSI-Accredited Standards Committee S3/SC1 and registered with ANSI. Springer Briefs in Oceanography. Springer and ASA Press. Reef Life Survey (2015), Standardised survey procedures for monitoring rocky & coral reef ecological communities. Reef Life Survey Program. Resonate (2018), Kangaroo Island Plantation Timbers EIS: Environmental Noise Impact Assessment. SA Whale Centre (2019), Live Sightings Log, South Australian Whale Centre, viewed 19 February 2019,
49 Wallaroo Marine Ecological Assessment, October 2020
Wiltshire, K, Rowling, K & Deveney, M (2010), Introduced marine species in South Australia: a review of records and distribution mapping, South Australian Research and Development Institute (Aquatic Sciences), Adelaide, SARDI Publication No. F2010/000305-1, SARDI Research Report Series No. 468.
50 Wallaroo Marine Ecological Assessment, October 2020
Appendix A. Records of macroalgae within the Atlas of Living Australia search area.
Green macroalgae (Phylum Chlorophyta) Red macroalgae (Phylum Rhodophyta) Acetabularia calyculus Areschougia congesta Caulerpa cactoides Bostrychia moritziana Caulerpa scalpelliformis Bostrychia tenuissima Chlorodesmis baculifera Botryocladia sonderi Cladophora valonioides Caloglossa leprieurii Codium spongiosum Capreolia implexa Enteromorpha compressa Centroceras clavulatum Ceramium cliftonianum Brown macroalgae (Phylum Ochrophyta, Ceramium pusillum Class Phaeophyceae) Cliftonaea pectinata Caulocystis cephalornithos Dasya kraftii Caulocystis uvifera Dictyomenia harveyana Cladostephus spongiosus Dictyomenia tridens Colpomenia sinuosa Dipterosiphonia dendritica Cystophora expansa Echinothamnion hystrix Dictyota fastigiata Gelidium pusillum Dilophus angustus Gloiosaccion brownii Dilophus gunnianus Haliptilon roseum Feldmannia paradoxa Haloplegma duperreyi Lobophora variegata Hypnea ramentacea Lobospira bicuspidata Laurencia filiformis Ralfsia verrucosa Laurencia majuscula Sargassum decurrens Lejolisia aegagropila Sargassum linearifolium Millerella pannosa Scaberia agardhii Peyssonnelia capensis Sphacelaria rigidula Polysiphonia blandii Zonaria crenata Polysiphonia decipiens Polysiphonia scopulorum Porphyra lucasii Protokuetzingia australasica Ptilocladia pulchra Rhabdonia clavigera Rhabdonia verticillata Rhodymeniocolax austrina Solieria robusta Spyridia filamentosa Wollastoniella myriophylloides
51 Wallaroo Marine Ecological Assessment, October 2020
Appendix B. Records of macroinvertebrates within the Atlas of Living Australia search area.
Sponges (Phylum Porifera) Bryozoans Fenestraspongia intertexta Amathia verticillatum Holopsamma laminaefavosa Echinoderms Cnidarians Allostichaster polyplax Halopteris campanula Anthaster valvulatus Nemertesia procumbens Coscinasterias calamaria Heliocidaris erythrogramma Arthropods Holothuria hartmeyeri Accalathura bassi Meridiastra atyphoida Alpheus villosus Meridiastra gunnii Ampelisca euroa Nectria pedicelligera Ampithoe ngana Peronella peronii Bircenna nichollsi Petricia vernicina Callipallene micrantha Rowedota epiphyka Cyproidea ornata Temnopleurus michaelseni Erugosquilla grahami Tosia australis Halicarcinus ovatus Hatschekia pagrosomi Ascidians (Phylum Chordata, Class Asicidaceae) Ibacus peronii Stolonica australis Leptomithrax gaimardii Mallacoota euroka Melicertus latisulcatus Metapenaeopsis crassissima Naxia aurita Nectocarcinus integrifrons Notorchestia australis Ovalipes australiensis Ozius truncatus Paguristes brevirostris Paguristes frontalis Palaemon intermedius Portunus armatus Protorchestia ceduna Schizophrys rufescens
52 Wallaroo Marine Ecological Assessment, October 2020
Molluscs Abranda modestina Lima vulgaris Argalista rosea Lorica volvox Astralium aureum Malleus meridianus Astralium squamiferum Mimachlamys asperrima Atrina tasmanica Munditia tasmanica Australaria australasia Musculus nanus Austrocochlea constricta Mytilus galloprovincialis Austrolittorina unifasciata Nassarius pyrrhus Barbatia pistachia Nerita atramentosa Brachidontes erosus Notoacmea flammea Brachidontes rostratus Octopus australis Bulla quoyii Paramontana rufozonata Callistochiton antiquus Pecten fumatus Ceratosoma brevicaudatum Phasianella australis Cernuella virgata Plesiotrochus monachus Chama ruderalis Pterochelus triformis Clanculus plebejus Pupoides adelaidae Cleidothaerus albidus Pupoides myoporinae Cochlicella acuta Reticunassa compacta Cominella eburnea Rhyssoplax calliozona Cominella lineolata Rhyssoplax tricostalis Conuber conicus Rissoina nivea Conus anemone Scutellastra peronii Dentimitrella semiconvexa Scutus antipodes Diloma concamerata Sepia apama Donax deltoides Sepia novaehollandae Elachorbis tatei Sepiadarium austrinum Electroma virens Sepioteuthis australis Eoacmaea calamus Sinumelon bitaeniata Equichlamys bifrons Sinumelon flindersi Eucrassatella donacina Siphonaria diemenensis Eucrassatella kingicola Siphonaria zelandica Euprymna tasmanica Solemya australis Fusinus australis Stomatella terminalis Gastrocopta margaretae Succinea australis Gazameda iredalei Tawera lagopus Hapalochlaena maculosa Thalotia conica Ischnochiton contractus Theba pisana Ischnochiton variegatus Trichomya hirsuta Ischnochiton virgatus Zeacumantus diemenensis Katelysia peronii
53 Wallaroo Marine Ecological Assessment, October 2020
Appendix C. Records of fishes and elasmobranchs within the Atlas of Living Australia search area.
Acanthaluteres spilomelanurus Omegophora armilla Acanthaluteres vittiger Parablennius tasmanianus Aracana aurita Parapercis haackei Aracana ornata Parapercis ramsayi Arnoglossus micrommatus Parapriacanthus elongatus Arnoglossus muelleri Parazanclistius hutchinsi Atherinason hepsetoides Parequula melbournensis Brachaluteres jacksonianus Pelates octolineatus Callorhinchus milii Platycephalus bassensis Chelmonops curiosus Platycephalus richardsoni Cristiceps australis Platycephalus speculator Cynoglossus broadhursti Pristiophorus nudipinnis Diodon nicthemerus Pseudocaranx wrighti Engraulis australis Pseudorhombus jenynsii Eocallionymus papilio Repomucenus calcaratus Etrumeus teres Rhycherus filamentosus Eubalichthys mosaicus Sardinops sagax Favonigobius lateralis Scobinichthys granulatus Foetorepus calauropomus Scomber australasicus Genypterus tigerinus Sillaginodes punctata Gonorynchus greyi Sillago bassensis Gymnapistes marmoratus Siphamia cephalotes Haletta semifasciata Siphonognathus argyrophanes Heteroclinus perspicillatus Siphonognathus attenuatus Heterodontus portusjacksoni Siphonognathus radiatus Heteroscarus acroptilus Stigmatopora argus Hyperlophus vittatus Stigmatopora nigra Hypnos monopterygius Sutorectus tentaculatus Kanekonia queenslandica Thamnaconus degeni Lepidotrigla papilio Thyrsites atun Leptatherina presbyteroides Thysanophrys cirronasus Leptoichthys fistularius Trachurus declivis Lophonectes gallus Trachurus novaezelandiae Maxillicosta meridianus Trygonorrhina dumerilii Maxillicosta scabriceps Upeneichthys vlamingii Mustelus antarcticus Urolophus gigas Nelusetta ayraud Vanacampus poecilolaemus Neoodax balteatus Vincentia badia Neosebastes bougainvillii Vincentia conspersa Neosebastes pandus Zebrias penescalaris Neosebastes scorpaenoides Zeus faber
54 Wallaroo CUEF - Construction Water Quality Management Plan
Objectives The objective of the water quality monitoring plan is to ensure that construction of the proposed breakwater does not harm the seagrass and reef communities surrounding it. Description of receiving environment The breakwater, comprising a causeway perpendicular to the coast leading to a berthing area parallel to the coast, is surrounded by a mixture of habitats (Figure 1), including (from offshore to inshore):
• Sand with a sparse (<5%) cover of mixed seagrass species, including Posidonia sinuosa, Zostera nigricaulis and Halophila australis, in depths of 6–7 m (below lowest astronomical tide). • Moderately dense (50-80%) cover of Posidonia sinuosa, in depths of 5–6 m • Reef covered with macroalgae dominated by Sargassum sp. with an understory of red, green and brown macroalgae, at depths less than 4 m. • Patches of dense Posidonia australis amongst the reef, in depths less than 3 m • Bare sand in the surf zone • Intertidal reef on the shore
Figure 1. Habitat map of the area surrounding the proposed breakwater. Potential impacts and desired outcomes Construction involves the placement of 1,000 m3 per day, for 107 days, of core material generally formed of very coarse gravel and cobbles, with very little fines (particles <75 μm diameter). Based on a conservative assumption that up to 1.5% of this material would be fines (Cardno 2020), approximately 1,600 m3 of fines would be placed with potential for suspension and resuspension in the water column. The same amount of fines disturbed during a dredging program would be within the range classified as ‘Medium’ risk (EPA 2020).
Turbidity reduces the light available to seagrass and macroalgae, potentially inhibiting photosynthesis. The default water quality guideline for turbidity South Australian coastal waters is 10 NTU (ANZECC/ARMCANZ 2000).
Hydrodynamic modelling of the plume dispersion shows that total suspended solids (TSS), representing turbidity1, can spike above 10 mg/L for several hours during construction within 100 m of the proposed causeway (Cardno 2020). These spikes are generally modulated by the tides, such that turbidities drop below 10 mg/L to the south-west and north-east of the proposed breakwater during the incoming and outgoing tides, respectively (Cardno 2020). The spikes occur between the hours of construction, where were assumed to be 7am to 5pm (Cardno 2020). Such a regime would provide for an additional 1–6 hours of sunlight per day (albeit at a low angle of incidence), depending on the season, while turbidities are near ambient levels. Modelling showed that resuspension of sediments (e.g. by a storm) could result in levels remaining higher than 10 mg/L for several days (Cardno 2020).
Given that the seagrass species concerned are resilient to low levels of light for periods lasting weeks to months, particularly Posidonia species (Westphalen et al. 2005), the predicted regime of light reduction is considered unlikely to have an impact. The focus of monitoring would be to ensure that the predicted tide-related respite from elevated turbidity levels (>10 NTU) was occurring as predicted by the modelling, and that the elevated turbidity levels were restricted to within 100 m of the point of placement.
It will be important to monitor background sites, in order to understand the net impact of the placement of core material on light availability. This is particularly relevant during times when the ambient turbidity is sufficiently high to inhibit photosynthesis regardless of construction activities.
A risk analysis similar to that undertaken for a dredging project with similar potential to produce a turbid plume would yield a mixture of low, medium and high risks (EPA 2020):
• The amount of spoil is at the upper end of the medium risk range, and the percentage of fines near the lower end of this range • The lack of organic material indicates low risk, with possible medium risk for resuspended sediment • Sensitive habitats within the plume area indicate high risk • A construction period of 15 weeks is indicative of high risk (c.f. <8 weeks for medium risk)
1 The ratio between TSS (mg/L) and turbidity (NTU) may vary from 1:1. For example, for the Outer Harbor Channel Widening Project it was 3:1 (BMT WBM 2017), which would provide a conservative outcome in this context. Even if the ratio were inverted, it would not change the general nature of the modelling results with spikes of exceedance but otherwise generally low values of TSS. Sampling design The parameters to be measured are turbidity (NTU) and dissolved oxygen (mg/L). Weather conditions (wind speed and direction, swell, cloud cover), depth and tides would also be recorded.
Monitoring would occur at (Figure 2):
• two background sites (B1 and B2), each at least 500 m north-east and south-west from the proposed breakwater, noting that modelling predicted occasional turbidity increases of up to 3 NTU at a point 300 m north-east of the breakwater (Cardno 2020). • two impact sites (I1 and I2), each 100 m north-east and south-west of the core material placement point • two intermediate sites (M1 and M2), each 200 m north-east and south-west of the core material placement point
Monitoring during construction would occur at hours 2, 5 and 8 of each 10 hour construction day. It could be set around the tide turn and mid-tide, but should be 3 hours max interval.
Baseline monitoring would not be essential in the context of the overall monitoring program design, but would be desirable as the information provided could be used to adjust trigger values and reduce the likelihood of environmental risk, or conversely, of unnecessary hold time. If baseline data are to be collected, there should be a minimum of 20 sampling events during a period of the same duration and season as the proposed construction period, at sites B1, B2 and I1 (or I2). If baseline data are collected, water samples should be taken and used to establish a relationships between TSS and turbidity.
Figure 2. Proposed water quality monitoring sites for construction of the proposed breakwater. Note that sites I1, I2, M1, M2 are in relation to core material placement near the end of the causeway, and would be further inshore at earlier stages of construction. Sampling procedures Sampling would use a portable water quality meter capable of measuring turbidity, DO (mg/L) and depth (e.g. TPS 90FL-T). The meter would be calibrated daily according to manufacturer’s instructions and applicable standards, with details recorded.
Sampling sites would be located using a handheld GPS, and depth measurements taken using the WQM (sample depth) and vessel depth sounder (maximum depth). Sampling would occur near surface, 1 m from the seabed and mid-depth.
Triggers and management actions Turbidity
The following events would result in cessation of core material placement:
Trigger Management Rationale Action Turbidity at I1 or I2 is greater Suspend core Exceedance of 10 NTU for all measurement than 10 NTU for all three material events would show that turbidities are not measurement events in a single placement modulated by tides to the extent predicted. day, until turbidity UNLESS at the relevant If turbidity levels are close to ambient Turbidity at B1 and B2 is greater site is below 10 values or if ambient values are sufficiently than 20 NTU NTU and high that photosynthesis is already being OR UNLESS review impeded, then there would be no benefit in Turbidity at the impact site with monitoring suspending construction activity. exceedance (I1 or I2) is less than program. 120% of the turbidity at B1 and B2. Turbidity at M1 or M2 is more Review Turbidity levels such as the above would than 10 NTU higher than at B1 or monitoring suggest that the turbidity plume (defined by B2 program 10 NTU above ambient) extends beyond the predicted maximum radius of 100 m. Dissolved oxygen < 4.0 mg/L Report to Low dissolved oxygen levels arising as a appropriate result of construction activity would result authorities only from resuspension of sediment during construction. There would be no benefit in suspending the placement of core material, which is free of organic material.
Reporting Reports detailing the monitoring, including raw data in an Excel spreadsheet, would be provided fortnightly.
If any baseline monitoring were to occur, a report would be provided at least 15 business days prior to commencement of construction. Wallaroo CUEF - Intertidal reef survey
Methods The area of reef that would be replaced by the construction of the causeway is 40 m along the shoreline and approximately 10 m width (Figure 1). The area was surveyed on 9 April 2021, leading up to low tide at 10:54 am. Five quadrats each 1 m x 1 m were placed randomly along each of three transects parallel to the shore - the uppermost section of the reef, mid-section and lowest section of the reef. Mobile invertebrates were scored as counts and sessile invertebrates (e.g. encrusting worms) and macroalgae were recorded as an approximate percentage cover range. Counts were considered complete when all loose rocks had been examined, and basement sand or rock had been exposed. Results The dominant organisms were the gastropods Nerita atramentosa and Austrocochlea constricta (Figure 2), and limpets, including Notoacmea spp. (Figure 3). Other species recorded included the rockpool star Parvulastra exigua (Figure 4), a grapsid crab and isopods. The average abundance of these organisms for each transect are provided in Table.
There were traces of the encrusting worm Galeolaria caespitosa in some quadrats. Quadrats in the upper transect had a cover of seagrass wrack in the range 5–80%, and quadrats in the lower transect had a cover of turfing macroalgae in the range 1–30%. There were also traces of the membranous green macroalgae Ulva in several quadrats.
The species recorded are typical of intertidal communities in sheltered to moderately exposed South Australian intertidal reefs, but the species richness is relatively low compared with other surveys, e.g. Benkendorff & Thomas (2007). References Benkendorff, K., Thomas, D. (2007) Intertidal Biodiversity Assessment of the Fleurieu Peninsula, S.A. Report to the S.A. Department of Environment and Heritage. Flinders University, Adelaide.
Edgar, GJ (2008), Australian Marine Life – The Plants and Animals of Temperate Waters. 2nd Edition, New Holland, Sydney.
Figure 1. Intertidal area with quadrat along mid-level Figure 2. Dominant gastropods Austrocochlea constricta transect. Note that about 30% of the intertidal reef was (left) and Nerita atramentosa (right) submerged at the time of the photograph.
Figure 3. Limpets Notoacmea spp. with an isopod to right Figure 4. Rockpool star Parvulastra exigua of centre.
Table 1. Mean abundance of organisms recorded on three intertidal survey transects parallel to the shoreline (lower, mid, upper). Common names follow Edgar (2008). Mean abundance (with standard error) Species Common name Lower Mid Upper Austrocochlea constricta Ribbed winkle 5.80 (3.14) 27.00 (3.78) 0.40 (0.40) Nerita atramentosa Western black crow 1.40 (0.68) 9.80 (2.75) 0.60 (0.40) Bembicium spp. Conniwink 0 0 1.00 (0.63) Lottidae Limpets 8.60 (6.91) 30.40 (5.07) 1.80 (1.11) Mytilidae Mussels 0.20 (0.20) 0 0 Parvulastra exigua Rockpool star 1.60 (1.36) 0 0 Grapsidae Grapsid crab 0.20 (0.20) 0 0 Isopoda Isopods 0.40 (0.40) 0.20 (0.20) 2.00 (1.14)
Coastal Processes Modelling Report Wallaroo Grain Terminal
Coastal Processes Modelling Report
Wallaroo Grain Terminal
NW30000
Prepared for T-Ports
8 December 2020
8 December 2020 Cardno i Coastal Processes Modelling Report Wallaroo Grain Terminal
Contact Information Document Information
Cardno (NSW/ACT) Pty Ltd Prepared for T-Ports ABN 95 001 145 035 Project Name Wallaroo Grain Terminal
Level 9 - The Forum File Reference Coastal Processes Modelling 203 Pacific Highway Report - Rev 2.docx St Leonards NSW 2065 Australia Job Reference NW30000
www.cardno.com Date 8 December 2020 Phone +61 2 9496 7700 Version Number 2 Fax +61 2 9439 5170
Author(s):
Chris Scraggs Effective Date 8/12/2020 Principal Coastal Engineer
Approved By:
Doug Treloar Date Approved 8/12/2020 Senior Principal Coastal Engineer
Document History
Version Effective Date Description of Revision Prepared by Reviewed by
A 08/07/2020 Draft CJS/HS PDT 0 16/07/2020 Draft Final CJS PDT 1 20/07/2020 Draft Final - Revised CJS PDT 2 08/12/2020 Final CJS PDT
© Cardno. Copyright in the whole and every part of this document belongs to Cardno and may not be used, sold, transferred, copied or reproduced in whole or in part in any manner or form or in or on any media to any person other than by agreement with Cardno.
This document is produced by Cardno solely for the benefit and use by the client in accordance with the terms of the engagement. Cardno does not and shall not assume any responsibility or liability whatsoever to any third party arising out of any use or reliance by any third party on the content of this document.
Our report is based on information made available by the client. The validity and comprehensiveness of supplied information has not been independently verified and, for the purposes of this report, it is assumed that the information provided to Cardno is both complete and accurate. Whilst, to the best of our knowledge, the information contained in this report is accurate at the date of issue, changes may occur to the site conditions, the site context or the applicable planning framework. This report should not be used after any such changes without consulting the provider of the report or a suitably qualified person.
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Table of Contents
1 Introduction 1 2 Sediment Data 2 3 Mean Weighted Mean Wave Direction (MWMWD) Assessment 3 4 LITDRIFT Modelling 6 4.1 Model Setup 6 4.2 Modelling Results 11 4.3 Shoreline Effects 16 4.4 Seagrass Wrack 18 4.5 Potential Sand Bypassing Methods 19 5 Summary and Discussion 20 6 References 21 Particle Size Distribution Tables
Table 3-1 Calculated Pre and Post Development Energy Weighted Mean Wave Directions and Changes 5 Table 4-1 Shore Normal Directions applied in This Study 10 Table 4-2 Results for the Shoreline Orientation Assessment 13 Table 4-3 Potential LST Rates Across Western, Centre and Eastern Profiles for Pre and Post Development Conditions 15
Figures
Figure 2-1 The Locations of the Cross-shore Profiles where Sediment Samples were collected for Mean Grain Diameter Determination 2 Figure 3-1 The Locations of the Wave Extraction Points for EWMWD Assessment 4 Figure 3-2 EWMWD Calculated at Different Contour Lines at the Wallaroo Harbour Site for Pre and Post Development Conditions 5 Figure 4-1 The Location of the Western, Centre and Eastern Profiles at the Wallaroo Harbour Site 6 Figure 4-2 The Bathymetry of Centre, Western and Eastern Profiles used for Litdrift Modelling 7 Figure 4-3 Relative Wave Coefficient Versus Wave Direction at Nearshore Extraction Location of -1.5 m MSL along Western Profile 8 Figure 4-4 Relative Wave Coefficient Versus Wave Direction at Nearshore Extraction Location of 0.0 m MSL along Western Profile 8 Figure 4-5 Relative Wave Coefficient Versus Wave Direction at Nearshore Extraction Location of -1.5 m MSL along Centre Profile 9 Figure 4-6 Relative Wave Coefficient Versus Wave Direction at Nearshore Extraction Location of 0.0 m MSL along Centre Profile 9 Figure 4-7 Relative Wave Coefficient Versus Wave Direction at Nearshore Extraction Location of -1.5 m MSL along Eastern Profile 10
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Figure 4-8 Relative Wave Coefficient Versus Wave Direction at Nearshore Extraction Location of 0.0 m MSL along Eastern Profile 10 Figure 4-9 Schematic showing the effect of changes in shoreline orientation on longshore transport (DHI, 2020). 11 Figure 4-10 Q-α Curve for Western Profile Assuming No Sand Is Available on the Profile Seaward of Approximately -0.50 m MSL 12 Figure 4-11 Q-α Curve for Centre Profile Assuming No Sand Is Available on the Profile Seaward of Approximately -0.50 m MSL 12 Figure 4-12 Q-α Curve for Eastern Profile Assuming No Sand Is Available on the Profile Seaward of Approximately -0.50 m MSL 13 Figure 4-13 Time-Series of Modelled Sediment Transport Across Centre Profile for Existing Case 14 Figure 4-14 Time-Series of Modelled Sediment Transport across the Centre Profile for Post-Development Condition 14 Figure 4-15 Shoreline Evolution for Full Causeway Case 17 Figure 4-16 Shoreline Evolution for Part Trestle Case 18 Figure 4-17 Schematic Drawing showing the Effect of Offshore Breakwaters on the Shoreline 19
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1 Introduction
The proposed Wallaroo harbour is located in an area that has complex bathymetric features and significant shoreline changes in plan alignment and seabed characteristics. Based on a review of aerial photography, the shoreline in the area is also predominantly rocky with interspersed areas of sand forming perched beach sand areas. The purpose of these investigations has been to investigate the likely effects of the proposed harbour works on the regional shoreline and within the harbour itself. These investigations required the estimation of mid-term longshore sediment transport characteristics in the shoreline region near the harbour. Storm-caused cross-shore sediment transport has not been assessed, but will become smaller within the harbour area. The Longshore Sediment Transport (LST) calculations were undertaken using the LITDRIFT module of the DHI LITPACK Littoral Processes FM modelling system. This module simulates the sediment transport (net and gross) under time-varying wave and water level conditions across realistic shore normal seabed profiles that are based on survey and spatially variable sediment characteristics – where the data is available. The sediment transport modelling has been undertaken along three profiles in both the pre and post development scenarios to estimate the potential LST rates at the Wallaroo harbour site. All modelling scenarios were undertaken using a timestep by timestep basis over 2010 (1-year of wave climate data) developed from SWAN wave modelling for each of the three selected shore normal locations. It should be noted that for the centre profile, two additional simulations were undertaken using ten years of record-by- record wave climate data (December 2009 to December 2019) in order to investigate the seasonal or even monthly variations of LST rates at the site. This document presents the outcomes of this sediment transport/coastal processes study.
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2 Sediment Data
Five sediment samples were collected by the Client, one each along five cross-shore profiles proposed by Cardno. The red lines shown in Figure 2-1 indicate the locations of these cross-shore profiles – taken near mean sea level on each profile. Putting the most western sample result aside, (with d50 of 1.112mm), the mean D50 at the Wallaroo harbour site is 0.125mm. This value was used as input for the LITPACK sediment transport modelling.
Figure 2-1 The Locations of the Cross-shore Profiles where Sediment Samples were collected for Mean Grain Diameter Determination
Note that the most western sample has a median grain size of 1.112mm, which is approximately ten times larger than the sand to the east. This indicates that very little sand is transported around the headland to the site. Particle size distribution plots for the five samples are provided in Appendix A.
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3 Mean Weighted Mean Wave Direction (MWMWD) Assessment
Cardno has undertaken an assessment of the potential impacts of the proposed harbour on the adjacent beaches due to altered wave directions that would be caused by the presence of the harbour breakwater. Potential long-term morphological impacts to the beach, specifically changes to the alignment/orientation of the beach due to altering the prevailing directionality of the incident wave energy at the shoreline, may occur. This has been assessed through an analysis of the Energy Weighted Mean Wave Direction (EWMWD) at selected output points along the shoreline inside the harbour, as well as both sides of the proposed breakwater for the existing and developed cases. Changes to the mean wave direction at the shoreline could reasonably be expected to cause long term shoreline recession/accretion along the beach (depending on the nature - direction and magnitude, of any changes). This assessment involved: 1. Re-running the SWAN wave model described in the wave modelling study to extract wave conditions along the shoreline at various depths (-4.5, -1.5 and 0.0m MSL bed level contours), as shown in Figure 3-1; 2. Updating the SWAN model to include the proposed harbour and re-running the long-term wave climate; and 3. Calculating the energy weighted mean wave direction for nine locations along the regional coastline for the pre and post developed cases; Figure 3-2 presents an aerial image of the site, overlaid with the computed weighted mean wave directions for the existing case and the developed case. These parameters are also presented in Table 3-1. This figure shows that the mean weighted mean wave directions for the existing case indicate a low, north-easterly directed net sediment transport rate due to the wave direction being nearly perpendicular to the shoreline, but oriented slightly west of normal. The modelling indicates that there will be minor changes to the mean weighted mean wave direction to the east and west of the harbour, with a slight anti-clockwise rotation (in the order of 1 degree) predicted to the west of the harbour, and a larger clockwise rotation (up to 10 degrees) to the east. In the lee of the harbour breakwater, the modelling predicts large changes to the EWMWD, with the model indicating that the EWMWD will rotate by over 60 degrees (clockwise). Based on this EWMWD assessment, it is likely that the construction of the harbour will cause changes to the shoreline as described below: • The net sediment transport rate to the west of the harbour will be largely the same as it is in the present situation. This means that the north-easterly directed transport will likely be blocked by the new harbour, thereby resulting in accumulation of sand in this section of the beach. More north-westerly waves will be blocked by the breakwater, thereby preventing removal of this accumulated sand by those waves; • The sediment transport in the lee of the harbour breakwater will reverse, transporting sand towards the south-west - albeit at a low rate. This change will cause the gradual formation of a beach (accumulation of sand) within the harbour, eventually, but slowly, reaching the eastern side of the breakwater at the shoreline, and consequent shoreline erosion to the north-east, up to the major change in shoreline alignment about 250m away, between the points C and E, see Figure 3.1; • Although the model is predicting only small changes to the weighted mean wave direction to the east of the proposed harbour, it is likely that this shoreline will recede slowly due to the blocking of sand from the south and the transport of sand into the lee of the breakwater.
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Figure 3-1 The Locations of the Wave Extraction Points for EWMWD Assessment
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Figure 3-2 EWMWD Calculated at Different Contour Lines at the Wallaroo Harbour Site for Pre and Post Development Conditions
Table 3-1 Calculated Pre and Post Development Energy Weighted Mean Wave Directions and Changes Energy Weighted Mean Wave Direction (º N) Point Existing Developed Change W4.5 308.7 308.2 0.5 W1.5 318.2 317.5 0.7 W0.0 318.4 316.9 1.5 C4.5 305.7 9.0 -63.3 C1.5 318.6 354.8 -36.2 C0.0 315.2 338.0 -22.8 E4.5 307.9 316.1 -8.2 E1.5 321.6 326.4 -4.8 E0.0 322.8 325.1 -2.3
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4 LITDRIFT Modelling
Cardno has undertaken longshore sediment transport modelling using the LITDRIFT module of the LITPACK coastal processes modelling system developed by the Danish Hydraulics Institute. It is used internationally for assessment of coastal processes. LITDRIFT computes longshore sediment transport from a time-series of wave and water level parameters. Natural beach profiles, graded sediments, currents, wind and local roughness can be included. Generally, the highest transport rate occurs in the breaking wave zone.
4.1 Model Setup
4.1.1 Profiles For this study, longshore sediment transport has been modelled for three shore normal profiles as indicated in 0. The bathymetric details of these profiles have been derived from the bathymetric and topographic data provided by WGA, and are presented in Figure 4-2.
Figure 4-1 The Location of the Western, Centre and Eastern Profiles at the Wallaroo Harbour Site
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Figure 4-2 The Bathymetry of Centre, Western and Eastern Profiles used for Litdrift Modelling
For this study, based on aerial imagery and the site photographs, the modelling has assumed that there is no sand on the profile below a seabed level of ~ -0.50m MSL.
4.1.2 Shore Normal Direction A key input to the sediment transport assessment is the direction of the normal to the shoreline. This parameter has a large effect on longshore sediment transport calculation. For example, where the direction of wave propagation may be 1 degree from the normal, but has erroneously been determined to be 2 degrees, the calculated transport rate is doubled; being directly proportional to this angle. Understanding that it is exceptionally difficult to determine a shore normal direction reliably using a contour map and protractor, one needs to adopt a different approach. Note also that the wave model also ‘feels’ the seabed differently in a numerical sense, depending upon model grid set-up. At this site, the bathymetry is very complex, meaning that the nearshore contours are not aligned in any particular direction – not parallel. Therefore, in order to select a representative shore normal direction, a series of wave modelling simulations were undertaken. The aim of these simulations was to model an offshore wave propagating to shore, from various directions. The simulation that resulted in the highest nearshore wave height (i.e. has the least amount of dispersion due to refraction), was then considered as representative of the overall shore normal direction. The results of this assessment in terms of relative wave coefficient versus wave direction at the nearshore extraction locations (-1.5 m MSL and 0.0 m MSL), are depicted in Figure 4-3 to Figure 4-8. The calculated shore normal direction for each profile used for LITDRIFT modelling is presented in Table 4-1. It is noted that for each profile, the shore normal direction is the average of wave direction at extraction locations of -1.5 m MSL and 0.0 m MSL where the maximum relative highest wave coefficient is calculated. This choice is based on common wave breaking depths, including tidal variation. In some cases, the wave coefficients were similar at the -1.5m MSL contour for a range of directions. In these cases, the direction was chosen to be the direction with the largest wave coefficient within +/- 10 degrees of the shoreline orientation measured from satellite imagery.
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1.9
) 1.8
s,BC 1.7 /H 1.6 s,insh 1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8
Relative Wave Coefficient (H Coefficient Wave Relative 0.7 0.6 300 305 310 315 320 325 330 335 340 345 350 355 Wave Direction at Extraction Point of -1.5 m MSL (TN)
Figure 4-3 Relative Wave Coefficient Versus Wave Direction at Nearshore Extraction Location of -1.5 m MSL along Western Profile
Figure 4-4 Relative Wave Coefficient Versus Wave Direction at Nearshore Extraction Location of 0.0 m MSL along Western Profile
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1.9
) 1.8
s,BC 1.7 /H 1.6 s,insh 1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8
Relative Wave Coefficient (H Coefficient Wave Relative 0.7 0.6 300 305 310 315 320 325 330 335 340 345 350 355 Wave Direction at Extraction Point of -1.5 m MSL (TN)
Figure 4-5 Relative Wave Coefficient Versus Wave Direction at Nearshore Extraction Location of -1.5 m MSL along Centre Profile
Figure 4-6 Relative Wave Coefficient Versus Wave Direction at Nearshore Extraction Location of 0.0 m MSL along Centre Profile
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1.9
) 1.8
s,BC 1.7 /H 1.6 s,insh 1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8
Relative Wave Coefficient (H Coefficient Wave Relative 0.7 0.6 300 305 310 315 320 325 330 335 340 345 350 355 Wave Direction at Extraction Point of -1.5 m MSL (TN)
Figure 4-7 Relative Wave Coefficient Versus Wave Direction at Nearshore Extraction Location of -1.5 m MSL along Eastern Profile
Figure 4-8 Relative Wave Coefficient Versus Wave Direction at Nearshore Extraction Location of 0.0 m MSL along Eastern Profile
Table 4-1 Shore Normal Directions applied in This Study
Profile Representative Shore Normal Direction (ºN)
Western 319.0
Central 327.5
Eastern 334.5
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4.2 Modelling Results
4.2.1 Q-Alpha Curves The longshore transport is highly sensitive to the orientation of the shoreline normal. A change in the shoreline normal will affect the angle between the approaching waves and the shoreline normal, which is one of the key parameters for longshore sediment transport. This is illustrated in Figure 4-9, in which a coastline is shown for two different shoreline orientations. Waves are in both cases approaching the shoreline from the east. The beach in the left panel has a shoreline normal towards south-east which causes longshore transport towards south (indicated by the blue arrow). The shoreline normal in the right panel is oriented towards north-east, which causes transport towards north (indicated by the blue arrow). Changes to shoreline orientation occur naturally in response to seasonal variations in the wave climate and in response to long term trends in erosion/deposition. The shoreline orientation will in particular change if changes to the upstream sediment supply occur. E.G., if sediment is blocked at a point along the shoreline, then the downstream shoreline will turn up against the predominant waves such that the longshore transport on the downstream beach is also zero. For embayed beaches such as the shoreline in Wallaroo the shoreline is often close to its equilibrium condition, which is the shoreline orientation at which the net transport is zero. Estimates of the equilibrium orientation of a shoreline may be calculated by use of numerical models, in which the annual longshore transport is calculated for different orientations of a shoreline. The calculated longshore transport is then shown as a function of the shoreline orientation thus forming a so-called Q-α curve.
Figure 4-9 Schematic showing the effect of changes in shoreline orientation on longshore transport (DHI, 2020). Figure 4-10 to Figure 4-12 show the Q-α curves for the three profiles. These figures show both the variation of the potential gross-transport (red curve) and the potential net transport (blue curve). Note that the gross- transport is defined to be positive irrespective of direction, and the net transport is defined positive for transport towards the north-east and negative towards the south-west. The figures show that the net transport is towards the north-east for shoreline orientations larger than approximately 300 degrees N and that the net potential transport for the present shoreline orientation is towards north-east. Turning the shoreline orientation clockwise (increasing the angle of shoreline orientation) will increase the magnitude of the net transport towards the north. The slope of the net transport i.e. the change in net transport per degree change in shoreline orientation, gives a measure of the sensitivity of the net transport to changes in shoreline orientation. The sensitivity of the net transport to changes in shoreline orientation is, according to the figures, constant near the present orientation and is roughly 280 to 350 m3/deg, depending on the profile. The results of the findings from the analysis are tabulated in Table 4-2.
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Figure 4-10 Q-α Curve for Western Profile Assuming No Sand Is Available on the Profile Seaward of Approximately -0.50 m MSL
Figure 4-11 Q-α Curve for Centre Profile Assuming No Sand Is Available on the Profile Seaward of Approximately -0.50 m MSL
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Figure 4-12 Q-α Curve for Eastern Profile Assuming No Sand Is Available on the Profile Seaward of Approximately -0.50 m MSL
Table 4-2 Results for the Shoreline Orientation Assessment
Profile Equilibrium Angle Current Angle Sensitivity Net Transport (m3/deg) (m3/year)
Eastern 304* 335 349 16,350
Central 299 327 335 11,500
Western 295* 319 283 9,650
* These values have been extrapolated
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4.2.2 Potential Longshore Sediment Transport Rates The results from the LITDRIFT coastal processes modelling system show a seasonally varying longshore transport. The pre and post development modelling results in terms of time-series of sediment transport rates over the 10 years modelled period for the centre profile are presented in Figure 4-13 and Figure 4-14, respectively. Note the calculated LST is described as potential because it depends on the availability of sand. The model results display a yearly cycle. The sediment transport tends to occur mostly during winter, compared with comparatively low sediment transport predicted during the summer months. For the existing condition, the modelling indicates that the winter wave climate will mostly transport sand towards the north east with a cumulative net transport of 151,500 m3 towards the north-east predicted over the 10-year simulation period. This equates to an existing transport rate of 15,150 m3/year. Conversely, once constructed the model is predicting that the winter waves will tend to transport the sand to the south west, though with a lower order of magnitude. A total net transport of 13,500 m3 towards the south-west is predicted by the model over the same period, which equates to an annual potential net drift of 1,350 m3/year into the harbour because of a reduction in wave heights and change in wave directions. The summary of the potential longshore sediment transport rates for the western, centre and eastern profiles is provided in Table 4-3.
Figure 4-13 Time-Series of Modelled Sediment Transport Across Centre Profile for Existing Case
Figure 4-14 Time-Series of Modelled Sediment Transport across the Centre Profile for Post-Development Condition
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Table 4-3 Potential LST Rates Across Western, Centre and Eastern Profiles for Pre and Post Development Conditions
Pre-Development LST Rates [m3/Yr] Post-Development LST Rates [m3/Yr] Simulation Simulation Shore Normal Profile Simulation Period No. Duration (Yr) Direction (º TN) Net Transport Gross Transport Net Transport Gross Transport
1 Western 1/01/2010-1/01/2011 1 319 9,650 11,600 9,750 11,450
2 Centre 1/01/2010-1/01/2011 1 327.5 11,550 21,350 -1,300 1,350
3 Eastern 1/01/2010-1/01/2011 1 334.5 16,350 16,600 11,500 11,850
4 Centre 1/12/2009-1/12/2019 10 327.5 15,150 17,050 -1,350 1,400
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4.3 Shoreline Effects The results of the wave and sediment transport investigations have been applied to the investigation of the likely shoreline changes that would be the consequence of the construction of the breakwater and harbour area revetment and wharf area. The changed potential longshore transport rates presented in Table 4-3 have been used to estimate the time required for these shoreline changes to develop, noting that once these new shoreline forms have developed to the point where they are in quasi-equilibrium with the modified energy- weighted mean wave directions, they will only undergo seasonal and storm related changes from then-on. Based on T-Ports discussions with South Australian government bodies, two cases have been developed. They are: 1. Shoreline changes associated with the proposed causeway and breakwater design, and 2. Replacing the innermost part of the causeway structure, say 125m, with a trestle structure that would allow sediment transport in the littoral zone and not impede seagrass wrack transport to the same extent, but still have some shoreline effect. Note the shoreline changes for a longer trestle structure would be very similar to those predicted in this report, as the main changes to the shoreline are due to the blocking of waves from the shore parallel section of the harbour. The results of these assessments are presented in Figure 4-15 and Figure 4-16. They show: 1. Full Causeway Case – Approximate shoreline widenings of 50m and 70m on the western and eastern sides of the causeway, respectively, developing over periods of 1 to 3 and 10 to 15 years, approximately. These areas of shoreline progradation would generally form on sandy areas. 2. Part Trestle Case – A salient developing in the lee of the breakwater and port area, eventually developing over a period of about 5 to 15 years, perhaps covering some seagrass. Both design alternatives would require ongoing monitoring of shoreline changes, and then, if those changes affect seagrass areas, public amenity or port operations in a deleterious manner, remedial action will be required; but be preceded by further coastal processes investigations based on Nearmap images and/or shoreline survey data.
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Figure 4-15 Shoreline Evolution for Full Causeway Case
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Figure 4-16 Shoreline Evolution for Part Trestle Case
4.4 Seagrass Wrack The proposed causeway design would likely lead to un-natural accumulation of seagrass wrack, probably on both sides of the structure; but in different volumes. Decaying seagrass is a natural product, but in large quantities can cause toxic conditions and environmental harm. An example case where Cardno has project experience is at Port Geographe, located south of Perth in Western Australia. This is a canal estate development having an ocean entrance maintained by training walls. At this site there is significant wrack accumulation that requires annual pick-up and transport to the general downdrift side by trucking. This process also picks-up beach sand. Both of the port causeway alternatives discussed above would change the wrack movement/accumulation environment. Unlike beach sand, which requires a wave driven current for transport, and will generally cease once a new quasi-equilibrium state has developed, wind-driven currents would cause continuing wrack accumulation in both cases. Accumulation would generally be in the beach-progradation zones shown in Figure 4-15 and Figure 4-16. This situation should be monitored together with sand accumulation, on an annual basis. Depending on the net wrack transport direction, there may be a need to transport accumulated wrack from the vicinity of the
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causeway – most likely to a location about 300m east of the port at site that is agreed with EPA, but spread out in the littoral zone, not be placed in a single ‘heap’.
4.5 Potential Sand Bypassing Methods Three potential sand bypassing methods have been proposed by the Client. Based on the modelling undertaken, the following recommendations are made:
Option 1 – Installation of nearshore culverts within the causeway The wave and sediment transport modelling indicate that there will be a reversal of sediment transport on the eastern side of the causeway in the lee of the harbour. Therefore, culverts are not expected to provide any significant benefit as sediment will be transported into the culverts from both ends. This would likely result in the culverts becoming blocked and they are therefore not recommended.
Option 2 - Suspended jetty structure from shore Replacing a portion of the causeway with an open jetty will mean that the facility will act essentially like a detached breakwater. The wave climate in the lee of the breakwater will be substantially reduced, and with significant changes in direction due to diffraction compared to the current, natural situation. The shoreline will respond by forming a salient, which will generally accrete until it is in equilibrium with the altered wave climate. Once it reaches quasi-equilibrium the net transport across the salient will be close to zero, and will have a similar downdrift effect as a solid causeway given the bulk of the transport is predicted to occur very close to shore. This process is described below in Figure 4-17.
Figure 4-17 Schematic Drawing showing the Effect of Offshore Breakwaters on the Shoreline
Option 3 - Dredging and pumping of accreted sand and dumping location A third option to be considered is dredging the accumulated sand updrift of the causeway and placing it on the downdrift (eastern) side. Of the options presented, this option would result in the least downstream effects. As noted earlier, the potential longshore sand transport rates presented in this report are likely to be over-estimated. Therefore, should this option be implemented it is recommended that the frequency of dredging be based upon routine monitoring of the shoreline position to the north and south of the port – land or aerial surveys on an annual basis until the magnitude of the real outcome has been determined.
It is also recommended that any sand that is bypassed be placed east of the eastern-most profile studied in this report to ensure that it does not return into the port area.
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5 Summary and Discussion
This report presents the outcomes of the coastal processes assessment undertaken for the proposed harbour development at Wallaroo. Two assessments have been carried out, the first being an assessment of the weighted mean wave direction for both the pre and post development cases. This assessment provides a qualitative description of the shoreline changes caused by the new harbour. This assessment indicates that: • The net sediment transport rate to the west of the harbour will be largely the same as it is in the present situation. This means that the north-easterly directed net transport will likely be blocked by the new harbour, resulting in accumulation in this section of the beach. More north-westerly waves will be blocked by the breakwater thereby preventing removal of this accumulated sand by those waves; • The sediment transport in the lee of the harbour breakwater will reverse, transporting sand towards the south-west - albeit at a low rate. This change will cause the gradual formation of a beach (accumulation of sand) within the harbour, eventually, but slowly, reaching the eastern side of the breakwater at the shoreline, and consequent shoreline erosion to the north-east, up to the major change in shoreline alignment about 250m away, between the points C and E, see Figure 3.1; • Although the model is predicting only small changes to the weighted mean wave direction to the east of the proposed harbour, it is likely that this shoreline will recede slowly due to the blocking of sand from the south and the transport of sand into the lee of the breakwater. Based on the above assessment, further modelling was undertaken using DHI’s LITDRIFT coastal processes model to quantify the potential sediment transport rates. This assessment generally concurred with the weighted mean wave direction assessment in that the longshore transport to the west of the harbour will be relatively unchanged, the sediment transport will reverse on the eastern side of the harbour, and further east there is a slight reduction in transport predicted. The potential net sediment transport rates are approximately 10,000 to 15,000 m3 /year in the existing case; however, once the harbour is constructed the model indicates that the sediment will: 1. Accumulate on the western side of the breakwater. The rate of potential accumulation is predicted to be 9,750 m3/year; 2. Accumulate on the eastern side of the breakwater due to a reversal of the longshore sediment transport. This is predicted to be a very slow process, with a net westerly directed potential transport of 1,400 m3/year predicted; and 3. Slowly recede to the east of the harbour. The net transport to the east of the harbour is predicted to decrease somewhat, however there will be a potential net deficit of about 10,000 m3/year. The shoreline will eventually reach a new equilibrium position after the construction of the new harbour. This equilibrium position depends on the type of structure that will be constructed. The estimated equilibrium shoreline positions for a full causeway and a ‘hybrid’ structure are presented in Figure 4-15 and Figure 4-16. A qualitative assessment of seagrass wrack has also been undertaken to estimate the likely areas to be affected by wrack accumulation. Wrack transport differs from sand transport, in that the primary mechanism of wrack transport is wind driven currents rather than being wave driven. Because of this, wrack will accumulation will continue, even after the shoreline has reached an equilibrium position. Because of this, it is recommended that the accumulation of wrack be monitored and together with sand accumulation, on an annual basis. Depending on the net wrack transport direction, there may be a need to transport the accumulated wrack from the vicinity of the causeway. Note that this study has assessed potential sediment transport, which assumes there is sufficient available sand for these rates to occur. Based on the available satellite imagery, and also site photographs, it appears that there is a lot of shallow rock in the area. This means that the sediment transport rates presented in this report are likely larger than what is occurring in reality. It is therefore recommended that should any sand bypassing be designed to accommodate up to the rates presented in this report, noting that the majority of this transport is predicted to occur during the winter months. However, the implementation of any sand bypassing should be based upon routine monitoring of the shoreline position to the north and south of the port – land or aerial surveys on an annual basis until the real outcome has been determined.
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6 References
Cardno, “Coastal Modelling Report, Rev 0 – Wallaroo Grain Terminal. Job Ref: NW30000”, Cardno, Sydney, Australia, 2020. DHI, “Littoral Processes FM - Littoral Processes Module User Guide”, Danish Hydraulics Institute, Copenhagen, Denmark, 2019.
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Wallaroo Grain Terminal
APPENDIX
PARTICLE SIZE DISTRIBUTION
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Environmental CERTIFICATE OF ANALYSIS Work Order : EN2003981 Page : 1 of 3 Client : CARDNO (NSW/ACT) PTY LTD Laboratory : Environmental Division Newcastle Contact : Christopher Scraggs Contact : Address : Level 9 The Forum 203 Pacific Highway Address : 5/585 Maitland Road Mayfield West NSW Australia 2304 St Leonards NSW 2065 Telephone : ---- Telephone : +61 2 4014 2500 Project : Wallaroo Grain Terminal Date Samples Received : 15-Jun-2020 08:40 Order number : 4081 Date Analysis Commenced : 23-Jun-2020 C-O-C number : ---- Issue Date : 25-Jun-2020 09:02 Sampler : ---- Site : ---- Quote number : EN/024/18 - Primary Work Only No. of samples received : 5 No. of samples analysed : 5 This report supersedes any previous report(s) with this reference. Results apply to the sample(s) as submitted. This document shall not be reproduced, except in full. This Certificate of Analysis contains the following information: l General Comments l Analytical Results Additional information pertinent to this report will be found in the following separate attachments: Quality Control Report, QA/QC Compliance Assessment to assist with Quality Review and Sample Receipt Notification. Signatories This document has been electronically signed by the authorized signatories below. Electronic signing is carried out in compliance with procedures specified in 21 CFR Part 11. Signatories Position Accreditation Category Aleksandar Vujkovic Laboratory Technician Newcastle - Inorganics, Mayfield West, NSW Dian Dao Sydney Inorganics, Smithfield, NSW
R I G H T S O L U T I O N S | R I G H T P A R T N E R Page : 2 of 3 Work Order : EN2003981 Client : CARDNO (NSW/ACT) PTY LTD Project : Wallaroo Grain Terminal General Comments
The analytical procedures used by ALS have been developed from established internationally recognised procedures such as those published by the USEPA, APHA, AS and NEPM. In house developed procedures are fully validated and are often at the client request. Where moisture determination has been performed, results are reported on a dry weight basis. Where a reported less than (<) result is higher than the LOR, this may be due to primary sample extract/digestate dilution and/or insufficient sample for analysis.
Where the LOR of a reported result differs from standard LOR, this may be due to high moisture content, insufficient sample (reduced weight employed) or matrix interference.
When sampling time information is not provided by the client, sampling dates are shown without a time component. In these instances, the time component has been assumed by the laboratory for processing purposes. Where a result is required to meet compliance limits the associated uncertainty must be considered. Refer to the ALS Contact for details.
Key : CAS Number = CAS registry number from database maintained by Chemical Abstracts Services. The Chemical Abstracts Service is a division of the American Chemical Society. LOR = Limit of reporting ^ = This result is computed from individual analyte detections at or above the level of reporting ø = ALS is not NATA accredited for these tests. ~ = Indicates an estimated value. l ALS is not NATA accredited for the analysis of bulk density in a soil matrix. Page : 3 of 3 Work Order : EN2003981 Client : CARDNO (NSW/ACT) PTY LTD Project : Wallaroo Grain Terminal Analytical Results
Sub-Matrix: SOIL Client sample ID 1 2 3 4 5 (Matrix: SOIL) Client sampling date / time [15-Jun-2020] [15-Jun-2020] [15-Jun-2020] [15-Jun-2020] [15-Jun-2020] Compound CAS Number LOR Unit EN2003981-001 EN2003981-002 EN2003981-003 EN2003981-004 EN2003981-005 Result Result Result Result Result EA051 : Bulk Density ø Bulk Density BULK_DENSITY 1 kg/m3 1200 1180 1120 1060 1150 EA150: Particle Sizing +75µm ---- 1 % 97 96 97 98 96 +150µm ---- 1 % 81 40 20 7 30 +300µm ---- 1 % 70 1 <1 <1 <1 +425µm ---- 1 % 68 <1 <1 <1 <1 +600µm ---- 1 % 65 <1 <1 <1 <1 +1180µm ---- 1 % 48 <1 <1 <1 <1 +2.36mm ---- 1 % 23 <1 <1 <1 <1 +4.75mm ---- 1 % 5 <1 <1 <1 <1 +9.5mm ---- 1 % <1 <1 <1 <1 <1 +19.0mm ---- 1 % <1 <1 <1 <1 <1 +37.5mm ---- 1 % <1 <1 <1 <1 <1 +75.0mm ---- 1 % <1 <1 <1 <1 <1 EA150: Soil Classification based on Particle Size Clay (<2 µm) ---- 1 % 1 2 2 2 2 Silt (2-60 µm) ---- 1 % 1 <1 <1 <1 <1 Sand (0.06-2.00 mm) ---- 1 % 67 98 98 98 98 Gravel (>2mm) ---- 1 % 31 <1 <1 <1 <1 Cobbles (>6cm) ---- 1 % <1 <1 <1 <1 <1 EA152: Soil Particle Density Soil Particle Density (Clay/Silt/Sand) ---- 0.01 g/cm3 2.49 2.64 2.69 2.55 2.71 Coastal Processes Modelling Report Wallaroo Grain Terminal
About Cardno Cardno is a professional infrastructure and environmental services company, with expertise in the development and improvement of physical and social infrastructure for communities around the world. Cardno’s team includes leading professionals who plan, design, manage and deliver sustainable projects and community programs. Cardno is an international company listed on the Australian Securities Exchange [ASX:CDD].
Contact Level 9 - The Forum 203 Pacific Highway St Leonards NSW 2065 Australia
Phone +61 2 9496 7700 Fax +61 2 9439 5170
Web Address www.cardno.com
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Core Placement Plume Dispersion Modelling
Wallaroo Grain Terminal
NW30000
Prepared for T-Ports Pty Ltd
22 December 2020
22 December 2020 Cardno i Core Placement Plume Dispersion Modelling Wallaroo Grain Terminal
Contact Information Document Information
Cardno (NSW/ACT) Pty Ltd Prepared for T-Ports Pty Ltd ABN 95 001 145 035 Project Name Wallaroo Grain Terminal
Level 9 - The Forum File Reference Plume Modelling Report - 203 Pacific Highway Rev B.docx St Leonards NSW 2065 Australia Job Reference NW30000
www.cardno.com Date 22 December 2020 Phone +61 2 9496 7700 Version Number 0 Fax +61 2 9439 5170
Author(s):
Hadi Sadeghian Effective Date 22/12/2020 Senior Coastal Engineer
Approved By:
Chris Scraggs Date Approved 22/12/2020 Principal Coastal Engineer
Document History
Version Effective Date Description of Revision Prepared by Reviewed by
A 05/10/2020 Draft Report for Review HS CS/PDT B 22/12/2020 Draft Final PDT CJS/HS
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Table of Contents
1 General 1 1.1 Introduction 1 1.2 Scope of Work and Task Objectives 3 1.3 General Study Approach 3 2 Project Datum and Conventions 4 2.1 Units 4 2.2 Coordinate system 4 2.3 Vertical Reference Level 4 2.4 Time Reference 4 2.5 Direction Conventions 4 3 Inputs and Assumptions 5 3.1 Fine Sediment Characteristics 5 3.2 Fine Sediment Release Rate 5 4 Hydrodynamic and Plume Dispersion Modelling 6 4.1 DELFT 3D 6 4.2 Model Setup 7 5 SEDIMENT PLUME MODELLING 10 5.1 Breakwater Construction Scenarios 10 5.2 Results 11 5.3 Seabed Sedimentation Assessment 22 6 Conclusions 29 7 References 30 Appendices
Appendix A Time Series Plots – Tidal Appendix B Time Series Plots - Summer Appendix C Time Series Plots - Winter Appendix D Time Series Plots – Post Construction (Tides) Appendix E Time Series Plots – Post Construction (Typical Storm) Appendix F Time Series Plots – Post Construction (Extreme Storm)
Tables
Table 5-1 Summary of Model Scenarios 10
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Figures
Figure 1-1 Wallaroo Port Locality Plan 2 Figure 4-1 DELFT3D Model Grids and Bathymetry (every second grid line shown) 8 Figure 4-2 DELFT3D Model Grids and Bathymetry – Zoomed to the Site – every second grid cell shown on the intermediate grid 9 Figure 5-1 Breakwater Construction Stages Simulated in the Model 11 Figure 5-2 Time series output points 12 Figure 5-3 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 1 (Location A and tides only) 13 Figure 5-4 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 2 (Location B and tides only) 14 Figure 5-5 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 3 (Location C and tides only) 15 Figure 5-6 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 4 (Location A and summer conditions) 16 Figure 5-7 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 5 (Location B and summer conditions) 17 Figure 5-8 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 6 (Location C and summer conditions) 18 Figure 5-9 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 7 (Location A and winter conditions) 19 Figure 5-10 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 8 (Location B and winter conditions) 20 Figure 5-11 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 9 (Location C and winter conditions) 21 Figure 5-12 Initial Sediment Thickness Map Assumed in the Model 22 Figure 5-13 Maximum predicted TSS due to resuspension – tides only simulation 24 Figure 5-14 Predicted 90th Percentile TSS concentration due to resuspension – typical storm simulation 25 Figure 5-15 Predicted 90th Percentile TSS concentration due to resuspension – extreme storm simulation 26 Figure 5-16 Predicted sedimentation and erosion of the deposited fines under tidal conditions 27 Figure 5-17 Predicted sedimentation and erosion of the deposited fines under typical storm conditions 27 Figure 5-18 Predicted sedimentation and erosion of the deposited fines under extreme storm conditions 28
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1 General
1.1 Introduction T-Ports are in the final stages of designing their new grain transhipment port at Wallaroo, within Spencer Gulf, South Australia. Figure 1-1 describes the location of Wallaroo Port. The general arrangement plan of the port is also shown in Appendix A of Cardno 2020a [1]. As part of the design process, Cardno (NSW/ACT) Pty Ltd was commissioned to undertake a number of coastal processes studies. They included: 1. Spectral wave modelling to estimate the extreme, peak-event wave conditions at the site for a range of ARI, together with associated water levels; 2. Detailed harbour tranquillity modelling using a phase resolving numerical model to estimate the at- berth wave conditions for port operations assessment; 3. Sediment transport and shoreline erosion assessment; and 4. Construction-period suspended sediment plume modelling to assess the potential extent of any turbid plumes due to the placement of core material. This report presents the outcomes of the construction plume assessment; scope items 1 to 3 have been previously reported in Cardno 2020a [1] and 2020b [2].
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Figure 1-1 Wallaroo Port Locality Plan
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1.2 Scope of Work and Task Objectives The scope of the suspended sediment plume dispersion modelling study specifically included: > Hydrodynamic Model Development > Baseline Hydrodynamic Modelling > Fine Sediment Transport and Dispersion Modelling The objectives of the plume dispersion modelling study were to: > Estimate the quantities of fine sediment released/suspended into the water column during the construction activities; > Determine the likely temporal extents of the construction plumes; and > Evaluate any increase in fine suspended sediment concentrations above ambient values due to the construction activities, This report presents the hydrodynamic model development, baseline hydrodynamic modelling and the fine sediment transport and dispersion modelling study results.
1.3 General Study Approach The general study methodology was as follows: > Sediment parameters and fines release rates were estimated by Cardno on the basis of the findings of sediment sampling and particle size definition analyses and the core placement construction rate and daily construction times, all of which were provided by the client. > A Delft3D-FLOW hydrodynamic model was used to establish the tidal water levels and currents over 31 days covering a full month, including two spring-neap tidal cycles; > A Delft3D-SED fine sediment transport (cohesive silt) model was developed and two-way coupled to the FLOW hydrodynamic model to simulate the advection-dispersion of the suspended sediments released as part of the construction activities. > Fine sediment releases were simulated for three different hydrodynamic scenarios, namely a tide-only condition and two tide plus wind conditions representative of summer and winter, and for three different construction phases (total 9 simulations). > Results were presented in terms of suspended sediment concentrations at the surface, mid-depth and near- bed layers of the water column. > The resuspension and dispersion of the deposited sediment post construction was investigated under ambient and storm conditions.
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2 Project Datum and Conventions
2.1 Units The SI System of Units has been used.
2.2 Coordinate system All coordinates are in MGA zone 53 and are based on the GDA94 spheroid.
2.3 Vertical Reference Level All elevations are in meters and referenced to Australian Height Datum (AHD), unless otherwise noted.
2.4 Time Reference All data related to time are given in the local time system, which is GMT + 9.5 hours – Central Standard Time
2.5 Direction Conventions Wave direction: The direction from which the waves are coming (i.e. coming from convention), and is measured clockwise from true north. A wave with a direction of 0º is coming from the north, and 90º is coming from the east, for example. Wind direction: The direction from which the wind is blowing (i.e. coming from convention), and is measured clockwise from true north. A wind with a direction of 0º is coming from the north, and 90º is coming from the east, for example. Flow: Flow directions refer to the direction towards which the flow occurs. Directions of the flow are always given clockwise with respect to true north. The unit is degrees. Nomenclature: To assist in distinguishing the different direction conventions, the following naming conventions are adopted in this report. Where the direction is “going to”, the direction is referred to as “…wards”, and where the direction is “coming from”, the direction is referred to as “…erly”, thus an eastward current is flowing towards the east and easterly winds and waves are coming from the east.
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3 Inputs and Assumptions
3.1 Fine Sediment Characteristics Sediment plumes associated with the construction of the breakwaters would mainly be associated with core placement. Based on the proposed work schedule, the rate of core placement would be about 150t/hour. The core will generally be formed of very coarse gravel and cobbles, with very little fines (<75µm), because that material is unsuitable for core construction. Nevertheless, for plume modelling purposes it has been assumed as a worst case that 1.5% of the core material is <75µm, which could be generated from grinding and degradation of the core material during transport from the quarry to the site, as well as residual surface dust. Suspended sediment plume simulations have been undertaken for three basic construction stage scenarios; they were:- 1. Early stage construction when dumping is near the shoreline and work will be in shallow water and suspended sediment concentrations will be highest, but current speeds lowest; 2. At the central section of the main breakwater arm to represent a mid-construction time period; and 3. At the seaward end of the main breakwater where current speeds are slightly higher. In all of the cases, the simulations covered a 1-month period. An average particle fall velocity of 0.4mm/s (van Rijn, 1990) was adopted for this study. Similar fall velocities have been found to be appropriate for previous fine sediment investigations undertaken by Cardno at Cairns, Botany Bay and Bowen. At Cairns, port authority dredging records were used to calibrate the siltation model.
3.2 Fine Sediment Release Rate As stated earlier, during construction, fine sediments have the potential to be suspended in the water column due to resuspension of fines on the seabed, as well as due to a small fraction of fines within the core material. For this study, we have assumed that an equivalent of 1.5% of the core material would be resuspended during the construction phase, leading to a total (core and re-suspended seabed sediments), sediment source rate in the model of 0.625 kg/s. Based on information provided by WGA, the construction activities would occur for 10 hours per day, 7 days per week. Therefore, this rate has been applied to the model between the hours of 7am and 5pm (local time). Additional fine material may be generated by the degradation of armour rock when it is transported to the site from the quarry. However, sediment plumes associated with the placement of armour rock are unlikely to occur because these rocks are individually placed on the breakwater, rather than being dumped/tipped as occurs with the core material. Armour rock is also typically stockpiled on site before it is placed; hence the amount of fine material released into the sea from the armour rock will not cause any perceivable plume. These armour rocks could also be washed off before placement if significant fines/dust on them are observed.
The total volume of core material to be placed below HAT is 107,000 m3, or 235,400t. Assuming a conservative estimate of 1.5% of this core material would degrade into fines, this equates to a total of 3,531t of fine material released over the construction period.
The volume of core material above HAT is estimated to be 30,000 m3. This material will have some fines intermixed with it; however, it will not be washed out because it will be contained within a geotextile filter fabric. Even without the geotextile, these fines would leech out very slowly over a number of years during periods of heavy rainfall, and would not result in any noticeable increase in turbidity due to the high level of dilution.
Moreover, based on a core-construction scheduled time of 107 days and an estimated overall breakwater length of about 600m, construction will proceed at a rate of 5 to 6m/day – faster in nearshore shallow areas, more slowly in the deeper and wider offshore areas.
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4 Hydrodynamic and Plume Dispersion Modelling
The scope of works to be undertaken by Cardno included modelling the potential temporal extent and magnitude of the sediment plumes associated with the proposed breakwater and reclamation works in the water column near the port site. In order to undertake these studies, a 3-Dimensional hydrodynamic model is required. For this study, Cardno’s existing 2D model of the Spencer Gulf has been applied, and which has been coupled with 3-Dimensional models of the area around Wallaroo nested dynamically within the greater Spencer Gulf model system.
4.1 DELFT 3D The Delft3D modelling system includes wind, pressure, tide and wave forcing, three dimensional current, stratification, sediment transport, cooling water and water quality descriptions and is capable of using rectilinear or curvilinear coordinates. Delft3D is comprised of several modules that provide the facility to undertake a range of studies. All studies generally begin with the Delft3D-FLOW module. From Delft3D-FLOW, details such as velocities, water levels, density, salinity, vertical eddy viscosity and vertical eddy diffusivity can be provided as inputs to the other modules. The wave and sediment transport modules work interactively with the FLOW module through a common communications file.
4.1.1 Hydrodynamic Numerical Scheme The Delft3D FLOW module is based on the robust numerical finite-difference scheme developed by G. S. Stellling (1984) of the Delft Technical University in The Netherlands. Since its inception, the Stelling Scheme has had considerable development and review by Stelling and others. The Delft3D Stelling Scheme arranges modelled variables on a staggered Arakawa C-grid. The water level points (pressure points) are designated in the centre of a continuity cell and the velocity components are perpendicular to the grid cell faces. Finite difference staggered grids have several advantages including: • Boundary conditions can be implemented in the scheme in a rather simple way; • It is possible to use a smaller number of discrete state variables in comparison with discretisations on non-staggered grids to obtain the same accuracy; and • Staggered grids minimise spatial oscillations in the water levels. Delft3D can be operated in 2D (vertically averaged) or 3D mode. In 3D mode, the model uses the σ-coordinate system first introduced by N Phillips in 1957 for atmospheric models. The σ-coordinate system is a variable layer-thickness modelling system, meaning that over the entire computational area, irrespective of the local water depth, the number of layers is constant. As a result a smooth representation of the bathymetry is obtained. Also, as opposed to fixed vertical grid size 3D models, the full definition of the 3D layering system is maintained into the shallow waters and until the computational point is dried. From a user point of view, the construction of a 3D model from a 2D model using the σ-coordinate system in Delft3D is effected by entering how many layers are required and the percentage of the depth for each layer. It is most common to define more resolution at the surface and at the bed where the largest vertical gradients occur. Boundary conditions can also be adjusted from depth averaged to specific discharges and concentrations per layer also. Horizontal solution is undertaken using the Alternating Direction Implicit (ADI) method of Leendertse for shallow water equations. In the vertical direction (in 3D mode) a fully implicit time integration method is also applied. Vertical turbulence closure in Delft3D is based on the eddy viscosity concept.
4.1.2 Wetting and Drying of Intertidal Flats Many estuaries and embayments contain shallow intertidal areas; consequently Delft3D incorporates a robust and efficient wetting and drying algorithm for handling this sort of phenomenon. Careful refinement in the intertidal areas and appropriate setting of drying depths to minimise discontinuous movement of the boundaries ensures oscillations in water levels and velocities are minimised and the characteristics of the intertidal effects are modelled accurately.
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4.1.3 Conservation of Mass Problems with conservation of mass, such as a ‘leaking mesh’, do not occur within the Delft3D system. However, whilst the Delft3D scheme is unconditionally stable, inexperienced use of Delft3D, as with most modelling packages, can result in potential mass imbalances. Potential causes of mass imbalance and other inaccuracies include: - • Inappropriately large setting of the wet/dry algorithm and unrefined inter-tidal grid definition; • Inappropriate bathymetric and boundary definition causing steep gradients; and • Inappropriate timestep selection (i.e. lack of observation of the scheme’s allowable Courant Number condition) for simulation
4.2 Model Setup
4.2.1 Grid Resolution and Extent The hydrodynamic model system that was set up for this investigation consisted of a four-grid nested model layout. The four grids were nested and prepared using domain decomposition procedures. Hence the computations on each grid were run dynamically in parallel. The model grids are presented in the MGA53 coordinates system. The model grid system applied to this study consisted of an outer grid of approximately 1km resolution covering the whole of the Spencer Gulf, and which was run in depth averaged mode. Within the outer grid lies a series of nested grids with the following resolutions: • Nest A is 150m; • Nest B is 50m; and • Nest C is 10m. The bathymetry for the model was interpolated to the computational grid using the Delft3D-Quickin module. The survey data provided by the Client formed the base for depth information around Wallaroo. Bathymetry of outside of this area has been derived from AUS Nautical Charts. Figure 4-1 and Figure 4-2 depict the model extent and bathymetry. The three nested models were run in 3D model with 5 equidistant sigma vertical layers.
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Figure 4-1 DELFT3D Model Grids and Bathymetry (every second grid line shown)
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Figure 4-2 DELFT3D Model Grids and Bathymetry – Zoomed to the Site – every second grid cell shown on the intermediate grid
4.2.2 Boundary Conditions Offshore tidal boundary conditions were extracted from a combination of the DTU10 (Technical University of Denmark Tidal Model), which is based on a finite element solution of the global tides with data assimilated from seventeen years of satellite altimeter readings. The methodology of the global tide models is described in Cheng and Anderson (2010). DTU10 provides up to twelve tidal constants on a 1/8 degree resolution full global grid. The tides are provided as complex amplitudes of earth-relative sea-surface elevation for ten primary (M2, S2, N2, K2, K1, O1, P1, Q1, S1 and M4) harmonic constituents. Four additional constituents (Mf, Mm, MS4 and MN4) were sourced from the TPx07.2 tide model, which uses along-track averaged altimeter data from the TOPEX/Poseidon and Jason (on TOPEX/Poseidon tracks since 2002) satellites.
4.2.3 Timestep A time step of 6 seconds was adopted to fulfil accuracy requirements based on the Courant Number.
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5 SEDIMENT PLUME MODELLING
The proposed construction of the breakwaters has the potential to cause some re-suspension of fine sediments during the placement of material on the seabed.
5.1 Breakwater Construction Scenarios A total of nine simulations have been undertaken as described below in Table 5-1. The release points and breakwater construction sequence assumed in the model are shown in Figure 5-1. Note that the simulations included partial construction of the breakwater up to the release point, as shown as the yellow areas in Figure 5-1. Each simulation has been run for a period of 24 days, with an additional 7 days hydrodynamic equilibrium warm-up period. Sediment was input to the model at a constant rate between 7am and 5pm each day during the simulation period. The sediment was introduced to the model at an equal concentration and mass in each vertical grid cell. These simulations assume stationary discharge points for 24 days, but as shown above, the construction of the core is likely to proceed at an overall rate of 5 to 6m/day – about 130m over the adopted duration of each simulation. Hence, these modelling scenarios will lead to very conservative construction period depths of fine silt deposition that would eventually be dispersed more widely. Based on the construction period parameters and the estimated rate of fine sediment production in the water column during construction, the total mass of fine sediment placed in the sea about the breakwater is ~2,890t. As
Table 5-1 Summary of Model Scenarios
Scenario Release Point Environmental Conditions
1 A No wind (tides only)
2 B No wind (tides only)
3 C No wind (tides only)
4 A Summer (January 2018) wind and tides
5 B Summer (January 2018) wind and tides
6 C Summer (January 2018) wind and tides
7 A Winter (July 2018) wind and tides
8 B Winter (July 2018) wind and tides
9 C Winter (July 2018) wind and tides
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Figure 5-1 Breakwater Construction Stages Simulated in the Model
5.2 Results Figures 5-3 to 5-11 present contour plots of the simulated suspended sediment concentrations from each model scenario. These are presented as the 90th percentile TSS concentration plots in mg/L above background concentration. These plots do not represent a snapshot in time, but rather provide a statistical representation of the range of plume extents and concentration. The percentile values represent the percent of time in which the plume is predicted to be at or below the values presented in the plots whilst the construction operations are taking place. The TSS values presented in the 90th percentile plots define the TSS concentration that is exceeded for only 10% of the time at each grid point – that is, these concentrations are exceeded for only 10% of the time Suspended concentration plots have been provided for the surface, mid-depth and bottom layers of the model. The model is predicting that the plume will be generally confined to the area around the construction works, with the model predicting that the excess TSS concentration would drop below 10 mg/L within 100m of the point of construction work. Time series plots of the predicted suspended sediment concentration at the nine output locations presented in Figure 5-2 are provided in Appendices A through C.
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Figure 5-2 Time series output points Based on the modelling results the following has been observed: • The highest suspended sediment concentrations occur during the Location A simulations. Location A is in very shallow water, and therefore the concentration of suspended sediment is higher. However, the extent of the plume is considerably smaller than what is predicted at Locations B and C; • The plume tends to spread perpendicularly to the shoreline (i.e. in a NE-SW alignment), with the greatest extent predicted during the summer simulations and at Location C; • During winter the model indicates that the plume will travel further offshore than under calm or summer conditions due to the predominant winds from the south-west; • In all simulations the 90th percentile suspended sediment concentration falls below 10 mg/L within 100m of the source point (construction point);
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Figure 5-3 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 1 (Location A and tides only)
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Figure 5-4 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 2 (Location B and tides only)
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Figure 5-5 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 3 (Location C and tides only)
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Figure 5-6 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 4 (Location A and summer conditions)
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Figure 5-7 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 5 (Location B and summer conditions)
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Figure 5-8 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 6 (Location C and summer conditions)
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Figure 5-9 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 7 (Location A and winter conditions)
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Figure 5-10 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 8 (Location B and winter conditions)
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Figure 5-11 Predicted 90th Percentile Suspended Sediment Concentration during Scenario 9 (Location C and winter conditions)
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Based on these results, the typical SS plume width is about 150m – see the figures above. Hence, over the approximate 600m of breakwater length, and adopting the estimated total released mass is 2890t, together with a silt dry bulk density of 1,000kg/m3, the average initial deposition depth is about 3cm. However, based on the modelling results, the sedimentation is likely to be thicker inshore in shallower water (due to less dispersion), compared to the deeper areas.
5.3 Seabed Sedimentation Assessment Effects on seabed fauna and flora depend on the total depth of deposition, as well as the rate of deposition. Hence the SS modelling results described above have been used describe upper limit deposition depth contours – that is, based on 24 days-long simulation periods, deposition depths will be greater than would be the case with daily construction progress at 5 to 6m/day. Hence, the following post-processing analyses have been undertaken. A siltation depth map (Figure 5-12) was prepared from the modelling cases described above have been used as an initial, post-construction deposition maps and the resuspension and dispersion of these fines has been investigated under: • Tidal conditions; • Typical storm conditions (1m significant wave height); • Extreme storm conditions (1 year ARI wave conditions).
Figure 5-12 Initial Sediment Thickness Map Assumed in the Model
Each simulation has been run for a 14 day period, assuming constant wave conditions, and would therefore be considered conservative. The modelling has also assumed that the storms occur immediately after the construction of the harbour, that is, no consolidation of the sediment has been assumed in the modelling parameters. This is a conservative assumption. The assumptions included in the model were: • Dry bulk density of the sediment = 500 kg/m3 • Critical shear stress for erosion = 0.2 N/m2 • Critical shear stress for deposition = 1000 N/m2
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The modelling results are presented below in Figures 5-13 to 5-15 in terms of the 90th percentile suspended sediment concentration during the simulation period, as well as the predicted change in bed level (i.e. erosion and deposition) at the end of the simulation. Note that the modelling has assumed that only the deposited sediment from the core placement is able to be transported and the existing seabed is unerodable. These figures show that under tidal conditions, re-suspension of the deposited fines is limited. The TSS concentration under tidal conditions is predicted to be less than 1 mg/L. During the storm conditions, the deposited sediment becomes resuspended and then dispersed. The 90th percentile TSS concentration plots indicate that the TSS concentration exceeds 15 mg/L outside the harbour facility for about 10% of the time during storm conditions. Slightly higher concentrations are predicted inside the harbour due to the sheltering it provides (up to 30 mg/L). The time series plots presented in Appendices E and F show that the TSS concentration is predicted to reach up to 180 mg/L at the start of the storm, but then drops to less than 10 mg/L after 2 days. This is due to the amount of deposited sediment on the seabed being completely eroded after this period. The sedimentation and erosion plots (figures 5-16 to 5-18) show that under storm conditions, the model is predicting the deposited sediment outside of the port to be nearly completely eroded after 14 days. The model is predicting that some of the eroded material will deposit inside the harbour, with an approximate thickness of about 3 cm.
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Figure 5-13 Predicted 90th Percentile TSS concentration due to resuspension – tidal simulation
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Figure 5-14 Predicted 90th Percentile TSS concentration due to resuspension – typical storm simulation
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Figure 5-15 Predicted 90th Percentile TSS concentration due to resuspension – extreme storm simulation
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Figure 5-16 Predicted sedimentation and erosion of the deposited fines under tidal conditions
Figure 5-17 Predicted sedimentation and erosion of the deposited fines under typical storm conditions
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Figure 5-18 Predicted sedimentation and erosion of the deposited fines under extreme storm conditions
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6 Conclusions
A Delft3D hydrodynamic and cohesive sediment transport model was developed to quantitatively assess the advection-dispersion of fine suspended sediment plumes associated with the proposed breakwater construction activities for the Wallaroo Grain Terminal. A total of nine modelling scenarios consisting of three construction phases and three environmental conditions for each construction phase were simulated to predict the suspended sediment concentrations due to the construction work. Fine sediment release rates were estimated based on the core placement productivity rate and a conservative assumption that up to 1.5% of fines (based on mass), would be released during construction. Overall, the magnitudes of suspended sediment concentration above background concentration are similar for all of the scenarios. As expected, suspended sediment concentrations are the greatest at the near-bed region, reducing towards the surface due to vertical mixing and particle settling. For all of the scenarios, the 90th percentile suspended sediment concentrations typically remain below 10 mg/L in the whole study area except within a 100m radius of the construction point. In this assessment, typical (representative) parameter settings have been used as input to the model. However, the results are unlikely to be sensitive to these parameter settings, and it is concluded that any material brought into suspension during the construction operation will have a limited extent of dispersion, and will mainly re-settle onto the seabed close to the release locations. An assessment of the potential resuspension of the freshly deposited fines after the construction period has also been undertaken. This included simulating the resuspension and dispersion of the fines under ambient (tidal) and storm conditions. Under ambient conditions, the modelling indicates that resuspension of the deposited fines is low, with the predicted maximum TSS concentration being less than 1 mg/L. Under storm conditions (typical and extreme), the wave action stirs up the freshly deposited sediment, causing resuspension. Due the limited amount of sediment on the seabed, the modelling indicates that at the start of a storm the TSS concentration could approach 180 mg/L, however this will rapidly reduce as the amount of sediment available for resuspension diminishes. The model indicates that the majority of the sediment would be resuspended and dispersed within approximately 2 days of the storm starting. The post construction resuspension assessment has assumed the storms occur immediately after the construction of the port, when the material is not consolidated and easily resuspended. This material will consolidate over time, which, if not dispersed by wave action, will reduce in thickness and the critical shear stress for resuspension will increase.
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7 References
[1] Cardno, “Coastal Modelling Report - Wallaroo Grain Terminal,” 2020.
[2] Cardno, “Coastal Processes Modelling Report - Wallaroo Grain Terminal,” 2020.
[3] L. van Rijn, Principles of Sedimentation and Erosion Engineering in Rivers, Estuaries and Coastal Seas, Netherlands: Aqua Publications, 2012.
[4] R. Whitehouse, R. Soulsby, W. Roberts and H. Mitchener, Dynamics of Esturaine Muds - A manual for practical applications (HR Wallingford), London, UK: Thomas Telford Publishing, 2000.
[5] Jiang. J., Han. H., Karunarathna. A., “Best Practice for Sediment Plume Dispersion Model Application,” in Australasian Coasts & Ports 2019 Conference, Hobart, 2019.
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Wallaroo Grain Terminal
APPENDIX
TIME SERIES PLOTS – TIDAL
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Wallaroo Grain Terminal
APPENDIX
TIME SERIES PLOTS - SUMMER
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Wallaroo Grain Terminal
APPENDIX
TIME SERIES PLOTS - WINTER
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Wallaroo Grain Terminal
APPENDIX
TIME SERIES PLOTS – POST CONSTRUCTION (TIDES)
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Wallaroo Grain Terminal
APPENDIX
TIME SERIES PLOTS – POST CONSTRUCTION (TYPICAL STORM)
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Wallaroo Grain Terminal
APPENDIX
TIME SERIES PLOTS – POST CONSTRUCTION (EXTREME STORM)
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About Cardno Cardno is a professional infrastructure and environmental services company, with expertise in the development and improvement of physical and social infrastructure for communities around the world. Cardno’s team includes leading professionals who plan, design, manage and deliver sustainable projects and community programs. Cardno is an international company listed on the Australian Securities Exchange [ASX:CDD].
Contact Level 9 - The Forum 203 Pacific Highway St Leonards NSW 2065 Australia
Phone +61 2 9496 7700 Fax +61 2 9439 5170
Web Address www.cardno.com
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