Metro Mining. Chapter 19 - Coastal Environment. Environmental Impact Statement

Transcription

1 Metro Mining Chapter 19 - Coastal Environment Environmental Impact Statement

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3 Table of Contents 19 Coastal Environment Project Overview Regulatory Framework Environment Protection and Biodiversity Conservation Act Sustainable Planning Act Coastal Protection and Management Act State Planning Policy July Coastal Management Plan Objectives and Performance Outcomes Protection Objective Performance Outcomes Assessment Method Proposed Coastal Activities Alternative Options Existing Environment and Coastal Processes Regional Setting Estuary Type Bathymetry and Morphology Coastal Processes Water Level Tidal Conditions Waves Storm Surge River Flows Sediment Transport Sea Level Rise Coastal Soils Shoreline and Bank Evolution Water Quality Sediments and Particle Size Distribution Potential Impacts Water Level Local Hydrodynamics Morphology and Longshore Transport Vessel Generated Waves Sediment Transport Propeller Wash Acid Sulfate Soils Climate change, Sea Level Rise and Storm Inundation Shoreline and Bank Evolution Offshore Transhipment Area and Bulk Vessels Cumulative Impacts Management and Mitigation Measures Water Level Local Hydrodynamics Morphology and Longshore Transport Vessel Generated Waves Sediment Transport and Propeller Wash Acid Sulfate Soils Climate Change, Sea Level Rise and Storm Inundation i

4 Shoreline and Bank Evolution Offshore Transhipment Marine Monitoring Program Qualitative Risk Assessment Summary Commitments ToR Cross-reference List of Figures Figure 19-1 Tidal circulation in the Gulf of Carpentaria Figure 19-2 Hydrographic survey of Skardon from November Figure 19-3 Hydrographic survey of Skardon from August Figure 19-4 Hydrographic survey of Skardon from August Figure 19-5 Hydrographic survey of Skardon from September Figure 19-6 Hydrographic survey of Skardon from April Figure 19-7 September 2009: long-section shown by dashed black line and approx. chainage in km Figure 19-8 Predicted tidal signal based on 275 days of measured data at the Skardon River Barge Ramp for an 8 month period Figure 19-9 Bathymetry of Skardon River (September 2009) with bed features noted Figure Skardon River bathymetry showing the model calibration locations (mouth site and upstream site) Figure Current speed (m/s) showing measured and modelled values (Mouth (upper figure) Upstream (bottom figure)) Figure Hydrodynamic model current extract locations (Ebb Bar, Mouth, Mid and Barge) Figure Skardon River peak flood tide currents Figure Skardon River peak ebb tide currents Figure Seasonal wave roses over a 24 year period Figure 19-16: Catchment delineation of the Skardon River and creeks to the south Figure Conceptualisation of sediment transport at the ebb bar of the Skardon River Figure Acid Sulfate Soils distribution and location of proposed development options Figure Aerial Photograph of Skardon River from Figure Aerial photograph of Skardon River from Figure Features of the coastline adjacent to the Skardon River Figure Skardon River sediment particle size and distribution Figure Sand waves recording bulk mobilisation processes along the proposed channel alignment within the mid estuary reaches Figure Active bed ripples showing sediment mobilisation over the seabed adjacent to the proposed BLF (PaCE, 2014 side scan sonar) Figure Spatial distribution of vessel generated wave risk Figure Propeller wash visualisation Figure location of the sub-bottom profiling work at the proposed RoRo location Figure The depth of soft sediments along the proposed RoRo shore location of less than 1m Figure Speed management plan ii

5 List of Tables Table 19-1 Tidal planes Table 19-2 Existing current velocities (m/s) within the proposed channel alignment extracted from the hydrodynamic model at four locations (Ebb Bar, Mouth, Mid and Barge) Table 19-3 Summary statistics for speed (m/sec) recorded from the mouth and upstream locations Table 19-4 Projected sea level increases to Table 19-5 Predicted mass of sediment eroded and resultant SSC from the propeller jet Table 19-6 Qualitative risk assessment coastal environment Table 19-7 Commitments coastal environment Table 19-8 ToR cross-reference coastal environment iii

6 19 Coastal Environment This chapter, in accordance with the Terms of Reference (ToR) (refer to Table 19-8), describes the coastal environment and the coastal processes potentially affected by the Bauxite Hills Project (the Project). The assessment focusses on the proposed activities in the Skardon River and the offshore transhipment area. This chapter provides measures to avoid and mitigate the impacts on the coastal environment and processes. The technical assessment was conducted by Ports and Coastal Environmental Pty Ltd (PaCE) and is provided in Appendix B3 Marine Ecology and Coastal Processes. The following Environmental Impact Statement (EIS) chapters contain impact and management information relevant to the coastal environment: Chapter 4 Land (acid sulfate soils); Chapter 6 Marine Ecology; Chapter 7 Matters of National Environmental Significance; Chapter 9 Water Quality; and Chapter 17 Transport (shipping activities) Project Overview Aldoga Minerals Pty Ltd (Aldoga), a 100% owned subsidiary of Metro Mining Limited (Metro Mining), proposes to develop the Project located on a greenfield site on the western coastline of Cape York, Queensland, approximately 35 kilometres (km) northeast of Mapoon. The Project will include an open cut operation, haul roads, Barge Loading Facility (BLF), Roll on/roll off (RoRo) facility, transhipping and will produce and transport up to 5 million tonnes per annum (Mtpa) of ore over approximately 12 years. The mine will not be operational during the wet season. The Project is characterised by several shallow open cut pits that will be connected via internal haul roads. The internal haul roads will be connected to a main north-south haul road that will link with the Mine Infrastructure Area (MIA), BLF and RoRo facility located to the north of the pits on the Skardon River. Bauxite will be screened in-pit and then hauled to the product stockpile using road train trucks. Bauxite from the Project is suitable as a Direct Shipping Ore (DSO) product (i.e. ore is extracted and loaded directly to ships with no washing or tailings dams required). Bauxite will be transported by barge via the Skardon River to the transhipment site, approximately 12 km offshore, and loaded into ocean going vessels (OGVs) and shipped to customers. No dredging or bed-levelling for transhipping is proposed as part of this Project. OGVs of between 50,000 to 120,000 tonne (t) each will be loaded at the transhipment anchorage site. Vessels will be loaded and bauxite will be transported to OGVs 24 hours per day with barges having an initial capacity of approximately 3,000 t to meet early production volumes, increasing up to 7,000 t as the Project reaches a maximum production volume of 5 Mtpa. The construction of the mine is due to commence in April 2017 and is expected to take seven months to complete. The first shipment of bauxite is planned for October The Project will be 100% fly-in fly-out (FIFO) due to its remote location. The Project will operate over two 12 hour shifts per day for approximately eight months of the year and is expected to employ up to 254 employees 19-1

7 during peak operations. In addition to the workforce, it is expected that the Project will result in the employment of additional workers through local and regional businesses servicing the accommodation camp and the construction and operation of the mine Regulatory Framework The coastal environment, in Queensland, is governed by several legislative instruments, policies and guidelines. Those relevant to the Project activities include: Environment Protection and Biodiversity Conservation Act 1999 (Cth); Sustainable Planning Act 2009; Coastal Protection and Management Act 1995; State Planning Policy July 2014; and Queensland Coastal Plan Environment Protection and Biodiversity Conservation Act 1999 The Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) defines coastal water of a State or the Northern Territory as the sea within three nautical miles of the baseline of the territorial sea and adjacent to that State or Territory (s227). This includes marine or tidal waters that are inside that baseline but are not within the limits of a State or that Territory such as Skardon River. The lowest astronomical tide (LAT) along the coast is generally described as the baseline Sustainable Planning Act 2009 The Sustainable Planning Act 2009 (SP Act) and Sustainable Planning Regulation 2009 seek to achieve sustainable planning outcomes through managing the process by which development takes place, managing the effects of development on the environment and continuing the coordination and integration of local, regional and state planning. Under the SP Act approval is required for development within the coastal zones but outside the mining leases. The BLF and the RoRo facility is therefore considered assessable development and required approval under the SP Act Coastal Protection and Management Act 1995 The Coastal Protection and Management Act 1995 (CPM Act) aims to provide protection and management of Queensland s coastal zone and coastal resources (s3). The Act provides regulatory provisions for the assessment of development for the purposes of the SP Act when development is located within a coastal management district and for work within a tidal area. Certain works carried out in coastal zones can be assessable under the SP Act State Planning Policy July 2014 The State Planning Policy July 2014 (SPP) underpins Queensland s planning system via a comprehensive set of principles. The SPP is supported by 16 state interest guidelines, including one specific to the coastal environment, SPP state interest guideline Coastal environment (SPP 19-2

8 Coastal environment). As per the SPP Coastal environment the development of the Project and the associated activities will be undertaken in a way that minimises disruption to coastal processes Coastal Management Plan The Coastal Management Plan is prepared under the CPM Act and provides management assistance for coastal land in Queensland to ensure the objectives of the CPM Act are met. The Coastal Management Plan also provides specific management actions for coastal areas in Queensland. No specific management actions under this plan are required Objectives and Performance Outcomes Protection Objective The coastal protection objectives are to ensure that the: Activity is developed and operated in a way that avoids environmental harm including impacts on terrestrial, estuarine, coastal and marine environmental values (EVs); Activity is developed and operated in a way that avoids and minimises adverse impacts on coastal processes, resources and scenic amenity of important natural coastal landscapes, views and vistas; Activity is to be carried out in accordance with best practice environmental management; and Performance outcomes correspond to the relevant policies, legislation and guidelines and that sufficient evidence is supplied (including through studies and proposed management measures) that show these outcomes can be achieved Performance Outcomes The performance outcomes relevant to the coastal environment are: Bank erosion and impacts to landside and benthic habitats will be managed through refining shipping activities; Acid sulfate soils and potential acid sulfate soils will be managed to prevent or minimise effects on EVs; and Activities conducted in the marine environment will be carried out in a way that will prevent or minimise any adverse impacts on surrounding waters or coastal habitats Assessment Method The coastal processes section of this EIS has incorporated the following: Literature collation and review of all available relevant information; Description of the existing physical coastal processes and EVs; Assessment of the potential impacts of the proposed development on existing coastal processes and the coastal environment; 19-3

9 Review and interpretation of anticipated shipping movements and BLF; and Detailing the potential impacts and identifying any mitigation or management measures that may be required. This assessment focussed on the development and activities within the Skardon River and the offshore transhipment area. Please refer to Appendix B3 Marine Ecology and Coastal Process for more information regarding the assessment method taken for the technical report Proposed Coastal Activities This section details the marine construction and operational processes required to establish the Project. The elements that are associated with the marine environment include the: BLF; RoRo facility; Marine operations and barge route; Barge moorings; and Offshore transhipment area. The aforementioned marine elements are discussed in detail in Chapter 2 Description of the Project. Deepening (i.e. bed-levelling or dredging) of the proposed barge route, including the ebb tide bar and BLF is not required to execute the construction and operational works for the Project Alternative Options The current design of the marine operations minimises development impact on the marine environment and associated coastal processes, where possible. The proposed construction design undertaken by Metro Mining incorporates a number of low (or lower) environmental impact options: Selection of low scale mining methods and export tonnages; Selection of dry screening over wet method beneficiation; Selection of the BLF and RoRo location; Selection of a transhipment anchorage area; Use of smaller capacity low draft marine equipment (avoiding the need for any dredging or bedlevelling works); and Adoption of pylon trestle based construction methods for the development of the BLF to cross sensitive coastal saltmarsh, mangrove and potential seagrass habitats with minimal disturbance. 19-4

10 Further details regarding the selection of the above Project design options, and the alternative scenarios that were assessed, are included in Chapter 2 Description of the Project Existing Environment and Coastal Processes Regional Setting The Gulf of Carpentaria is a large and relatively shallow body of water which is enclosed on three sides by the Australian mainland and bounded on the north by the Arafura Sea. It is 480 km wide and 640 km long with an area of approximately 310,000km2 and a maximum water depth of 70m. The tidal wave enters from the northwest (the Arafura Sea) and propagates clockwise around its amphidromic point (a nodal point about which the tide rotates). A diagrammatic representation of the tidal circulation within the Gulf of Carpentaria (WorleyParsons, 2010) is shown at Figure The circulation within the Gulf can be set up due to the wind stress applied by tropical cyclones at the water surface driving wind induced currents and residual water level circulations. The eastern shoreline current is parallel to the coast at the peak flood and ebb stages of the tide. Tidal signals around the Gulf of Carpentaria are semi-diurnal in the north, decreasing rapidly towards a diurnal signal in the south. At Skardon River the tide signals are mixed. M2 Amphidrome (a) Flood tide (b) Ebb tide Current vector Surface elev. Figure 19-1 Tidal circulation in the Gulf of Carpentaria Source: WorleyParsons, 2010 The Gulf of Carpentaria can be subject to seasonal fluctuations in sea level (up to 0.5m) as a result of trade winds (e.g. during the monsoon) and forcing from the Arafura Sea (Wolanski, 1993). These seasonal sea level fluctuations can result in large areas only being inundated by tides in the summer months (during the monsoon), as a result these areas cannot support mangrove or freshwater vegetation and therefore form salt flats. In addition, circulation within the Gulf can also be set up due to the wind stress applied by tropical cyclones at the water surface driving wind induced currents and residual water level circulations. 19-5

11 There are existing trading ports within the Gulf of Carpentaria located at Karumba and Weipa. They provide facilities for large bulk carriers used to export concentrate from local mines. In addition, the Port of Skardon River was declared a port in February 2002, but to date limited shipments of product (kaolin) have been shipped via the port. Commercial fishing fleets are also prevalent in gulf waters during the prawn and fin-fish seasons. The climatic conditions are discussed in Chapter 3 Climate. The scenic amenity of the area is discussed in Chapter 4 Land Estuary Type The Skardon River is described as a Tidal Creek (TC) as it has a low freshwater input with lowgradient, seaward sloping coastal flats (Ryan et al., 2003). These systems are primarily influenced by tidal currents (refer to Section ) and as a result they comprise of straight, sinuous or dendritic tidal channels that taper and shoal to landward. The mudflats which surround the creeks tend to be high relative to the tidal planes, with seawater being mainly confined to the tidal channels except during high tide on spring tides. Due to the strong tidal currents and large tidal ranges, the waters are usually highly turbid Bathymetry and Morphology For this assessment five hydrographic surveys of the Skardon River are available from 1998 to 2015 (Figure 19-2 to Figure 19-6). All of the surveys extend at least from the ebb tidal delta offshore of the entrance up to the port location. The number of transects undertaken during each hydrographic survey along the main river channel is variable which means that a direct comparison between all years at all locations is not possible. The most extensive survey was undertaken in September 2009 when the majority of the channel from the ebb tidal delta to upstream of the port was included. This section focuses on the change in bed elevation between the hydrographic surveys to develop an understanding of the river morphology and its changes. The bed elevation along the approximate deepest section of the channel is shown in Figure 19-7 for a long-section of the Skardon River from the ebb tidal delta to the existing barge ramp location; the location of the long section is shown in Figure This shows that the bathymetry in the area between the entrance, including the entrance, and the port area has been relatively stable from 1998 to 2015 (with some small changes close to the entrance between 1998 and 2002). Conversely, the channel bathymetry offshore of the entrance has been more dynamic. It is important to note that over the 17 year period only a single tropical cyclone tracked close to Skardon River and this was a Category 1 (the lowest of the five categories) system. Strong winds and large waves during a tropical cyclone have the potential to result in significant sediment transport along the shoreline adjacent to the Skardon River mouth. Accordingly, this could result in significant bathymetric changes to the area offshore of the Skardon River mouth including the channel. As such, the bathymetric changes over the 17 years of data should be considered to represent relatively calm conditions. 19-6

12 Figure 19-2 Hydrographic survey of Skardon from November 1998 Figure 19-3 Hydrographic survey of Skardon from August

13 Figure 19-4 Hydrographic survey of Skardon from August 2007 Figure 19-5 Hydrographic survey of Skardon from September

14 Figure 19-6 Hydrographic survey of Skardon from April

15 Figure 19-7 September 2009: long-section shown by dashed black line and approx. chainage in km 19-10

16 Coastal Processes Coastal process studies have previously been undertaken in the Gulf of Carpentaria for the Rio Tinto Amrun Bauxite Project (formerly known as the South of Embley Project) EIS, located approximately 95 km from the Project, and the Pisolite Hills Project focussed on Port Musgrave, approximately 25km to the south of the Project. These studies involved models and analysis of collected field data, for the Amrun Project there was particular focus in relation to the significant levels of dredging, that were subsequently approved. Similarly, the nearby SRBP has undertaken modelling work in relation to their proposed bed-levelling works. No site specific modelling has been conducted for this Project as no dredging or bed-levelling is proposed. The following coastal processes and environments are discussed below: Water level; Tidal conditions; Waves; Storm surge; Sediment transport; Sea level rise; Coastal soils; and Shoreline evolution Water Level The Gulf of Carpentaria can be subject to seasonal fluctuations in sea level (up to 0.5 m) as a result of trade winds (e.g. during the monsoon) and forcing from the Arafura Sea (Wolanski, 1993). These seasonal sea level fluctuations can result in large areas being inundated by tides in the summer months (during the monsoon). These seasonally inundated areas cannot support mangrove or freshwater vegetation and therefore form salt flats Tidal Conditions Tidal Water Levels The closest available tidal data is recorded in Weipa (Humbug Point), approximately 93 km south of the Project. Tidal plane information is also available at Cullen Point and Vrilya Point but these are based on less data than for Weipa and are not considered as accurate. In addition, eight months of measured water level data at the Skardon River Barge Ramp has been used to predict approximate tidal planes, these were calculated based on the guidelines in the Australian Tides Manual, Special Publication No. 9 (PCTMSL, 2011). The tidal plane information for the four locations is shown in Table The tidal planes show similar tidal levels and ranges at Weipa and Cullen Point, with a larger tidal range at Vrilya Point and Skardon River Barge Ramp

17 Table 19-1 Tidal planes Tidal Plane Wiepa LAT (m) Cullen Point LAT (m) Vrilya Point LAT (m) Skardon River Barge Ramp LAT (m) Highest Astronomical Tide 3.4 Mean High High-Water Mean Low High-Water Mean Sea Level Mean High Low-Water Mean Low Low-Water In tidal creeks amplification of the tidal wave can occur within the creek which locally elevates water levels inside the system and on the surrounding intertidal flats. It is likely that the increased tidal levels within Skardon River relative to Weipa and Cullen Point are at least partially a result of local amplification of the tidal wave within the river. It is expected that similar tidal levels and ranges to Cullen Point and Weipa would occur offshore of the mouth of the Skardon River. The timing of high and low waters at Skardon River Barge Ramp were within 20 minutes of Weipa. The measured water level at the Skardon River Barge Ramp was processed to remove any residual water levels, the resultant predicted water levels are shown in Figure 2-7. The tidal signal at Skardon River is predominantly diurnal with a small semi-diurnal signal which results in a consistent small second high and low water each day. The eight month overview of the tidal signal highlights the variability in the tidal signal, with significant differences between successive lunar cycles (29.5 day cycle). In addition, it also highlights the variability in the semi-diurnal signal over time. Figure 19-8 Predicted tidal signal based on 275 days of measured data at the Skardon River Barge Ramp for an 8 month period

18 Storm Tide There is limited storm surge data available for the Skardon River. A detailed storm tide assessment has been carried out at Weipa by WorleyParsons (2008) which can be used to provide an indication of likely storm tide conditions for the Skardon River. The assessment found that the potential for a high storm tide (combined tide and surge) to occur at Weipa was reasonably low, with a 100 year ARI of approximately 2m AHD (compared to an HAT level of 1.63m AHD). The reasons for the predicted relatively low storm tide level was mainly a result of less intense cyclones tending to occur in the area and the likelihood that a rare severe cyclone crosses at the same time as a spring high tide is very low. Based on this analysis and combined with high water levels for the Skardon River expected to be similar as at Weipa, the storm tide levels for the Skardon River are expected to be comparable to Weipa and therefore storm tides are not considered to present a significant risk in the area Tidal Currents Skardon River is categorised as a tidal creek where tidal currents are the dominant processes. The tidal action drives the transport of sediment into the estuary. Currents within the estuary are influenced by the channel depth and orientation and the difference in tidal range inside and outside the estuary. The sheltered conditions eventually allow the coarser sediment fractions to settle out of suspension. Tidal creeks are usually highly turbid due to the strong tidal currents generated by the macro-tidal ranges allowing fine sediments to remain in suspension during spring tides. The currents within the creek will be influenced by the channel depth and orientation along with the difference in tidal range through the creek. Bed Form Features The bathymetry of the main channel in Skardon River along with areas with different bed forms is shown at Figure The highest tidal current speeds in an estuary tend to occur close to the entrance. Due to the configuration of the Skardon River, the peak speeds are expected to occur at the constriction of the entrance where a flatbed occurs. The flat bed indicates that the flow velocity exceeds the speed at which ripples and mega ripples form, with peak current speeds potentially exceeding 1m/s. Offshore of the entrance mega ripples and sand waves occur in the main channel where current speeds remain high due to the constrained channel focusing the flow, and where the ebb tidal delta forms the tidal currents are much lower as wave action will start to dominate this area. These offshore features indicate active coastal processes and the natural sand transport of sand across the entrance to the river (natural sand bypassing). Inside of the entrance some channel braiding occurs, these features result from the tidal current speeds reducing away from the entrance and the coarser sediment being deposited. The areas of ripples further upstream indicate that relatively high (>0.5m/s) peak current speeds are likely to occur in these areas as well and that sand is still present. Another patch of flatbed is situated between two ripples/sand waves, again indicating elevated current velocities. Further upstream where the Port of Skardon River is located is a relatively flat bed with no obvious bed forms brought about by current velocities, this indicates that lower current speeds occur in this area (peak current speeds <0.5m/s) and it is likely that the bed material has a higher percentage of fine grained silts and clays than further downstream

19 Figure 19-9 Bathymetry of Skardon River (September 2009) with bed features noted Modelled To facilitate impact assessment processes a calibrated hydrodynamic model has been developed for the study area (PaCE, 2016). Locations of the calibration sites for this investigation along with the extent of the model grid and the interpolated bathymetry are shown in Figure The hydrodynamic model was calibrated against measured water level and current data. The measured tidal currents were analysed as part of a harmonic analysis to remove the influence of any residual events and ensure the currents used for the calibration were due to solely astronomical forcing (the tide). Time series plots for the calibration of current speed are shown in Figure The plots show that the model is capable of consistently predicting current speed at the two data collection sites

20 Figure Skardon River bathymetry showing the model calibration locations (mouth site and upstream site) Note: Blue = measured, Red = modelled Includes measured water level data (mahd) Figure Current speed (m/s) showing measured and modelled values (Mouth (upper figure) Upstream (bottom figure)) 19-15

21 Four locations along the proposed navigation channel have been analysed from the model, including the Barge, Mid, Mouth and Ebb Bar locations (Figure 19-12). These locations describe a range in mean current velocities between 0.11m/s and 0.41m/s, with peak velocities ranging between 1.06m/s and 0.48m/s (Table 19-2). Peak flood and peak ebb tide current velocities from the wider study area and channel alignment are presented within Figure and Figure Figure Hydrodynamic model current extract locations (Ebb Bar, Mouth, Mid and Barge) Table 19-2 Existing current velocities (m/s) within the proposed channel alignment extracted from the hydrodynamic model at four locations (Ebb Bar, Mouth, Mid and Barge) Tidal Plane SRBP Barge Mid Mouth Ebb Bar Depth (m MSL) Average Speed (m/s) Median Speed (m/s) th Percentile Speed (m/s) th Percentile Speed (m/s) Maximum Speed (m/s)

22 Figure Skardon River peak flood tide currents Figure Skardon River peak ebb tide currents 19-17

23 Measured Project Specific Tidal Data PaCE deployed two data logging stations on the Skardon River, one at the river mouth and one upstream of the existing barge ramp. The logging stations recorded, tidal depth range, temperature and current speed and direction, from the 22 April 2015 to 29 July Current speed was greatest from the mouth location, reporting a mean of 0.27 metres per second (m/sec). The upstream location reported approximately half that current velocity with a mean of 0.14 m/sec. A summary of the speed statistics is presented Table Table 19-3 Summary statistics for speed (m/sec) recorded from the mouth and upstream locations Location Valid N Mean Min Max Median Upper Quartile Lower Quartile Mouth 17, Flood 8, Ebb 9, Barge 28, Flood 13, Ebb 14, ) Temporary fouling of the tilt sensor may have resulted in this maximum figure Waves Previous investigations by WorleyParsons (2010) at Port Musgrave showed that based on the wave buoy measurements at Weipa, the wave climate in the area is seasonal. Wave activity is highest in the wet season and during tropical cyclones and monsoon events. In the dry season wave heights in the Gulf are generally small and calm conditions prevail. To further define the offshore wave climate for the Skardon River, wave data was extracted from the closest grid point using the WAVEWATCH III (WW3) hindcast model. The data includes 24 years of information and shows the seasonal wave conditions (Figure 19-15) for the offshore environment. Similar to the WorleyParsons (2010) data, the dry season (spring, summer and part of autumn) is characterised by small waves of less than 1 m from the east to southeast for a low period (peak wave period less than 4s) (locally generated wind waves). These waves are generated by the dominant east-southeast winds during the dry season, resulting in calm conditions along the east coast of the Gulf as the waves generated by the winds are from the east to east-southeast. The largest waves are from the west to west-northwest and can have peak wave periods of up to 14s. These waves occur during the wet season (summer and part of autumn). Tropical cyclones or monsoon swells during the wet season could exceed the WW3 data wave heights and wave directions are anywhere from north to southwest. The area offshore of the constricted entrance to the Skardon River will be influenced by both offshore generated swell waves and locally generated wind waves. Based on the offshore wave climate this area will tend to be exposed to waves during the wet season, with waves occurring from the west to the northwest. These swell waves will drive sediment transport along the shoreline adjacent to the Skardon River and also influence sediment transport at the ebb tide delta and the Skardon River channel offshore of the entrance. The larger tropical cyclone or monsoon offshore swell wave events have the potential to result in significant and rapid changes to the ebb tidal delta and the morphology of the channel offshore of the entrance to Skardon River. Due to the narrow entrance of the Skardon River (approximately 300 m) combined with the complex and relatively shallow bathymetry of the ebb tidal delta and the offshore channel, swell waves are not expected to propagate inside the Skardon River. The area upstream of the entrance 19-18

24 will only be influenced by locally generated wind waves and the locally generated wind waves will be small and very short period given the dominant wind directions do not align with the estuaries main axis. Based on this, along with the dominance of tidal currents within the river, locally generated wind waves in the estuary are not considered to be a significant process. Figure Seasonal wave roses over a 24 year period 19-19

25 Storm Surge There is limited storm surge data available for the Skardon River. A detailed storm tide assessment has been carried out at Weipa by WorleyParsons (2008) which can be used to provide an indication of likely storm tide conditions for the Skardon River. The assessment found that the potential for a high storm tide (combined tide and surge) to occur at Weipa was reasonably low, with a 100 year Average Recurrence Interval (ARI) of approximately 2 metre Australian Height Datum (mahd) (compared to a highest astronomical tide (HAT) level of 1.63 mahd). The relative storm tide level is predicted to be low mainly as a result of less intense cyclones tending to occur in the area and the low likelihood that a rare severe cyclone crosses at the same time as a spring high tide. The storm tide levels for the Skardon River are expected to be comparable to Weipa given the similar high water levels. Therefore storm tides are not considered to present a significant risk in the area. During storm surges, lowering or scarping of the existing inlet profile is anticipated. The response to the aforementioned impacts will depend on the likelihood and depth of firmer underlying strata. It is also anticipated that wave run up will result in the transport of sediment into the littoral system during severe storms, when surge is combined with high tide. Storm tide inundation is discussed and figures are presented in Chapter 11 Flooding and Regulated Structures River Flows A hydrological assessment of the Skardon River was undertaken by SRK Consulting Pty Ltd (2013). The assessment included catchment delineation and hydrological modelling to determine monthly cumulative yields and average flows for each of the catchments (Figure 19-16). Based on this assessment the features associated with the Skardon River are as follows: Approximately 30 km long; Total catchment area of approximately 480 km2; The catchment has suffered little disturbance; The freshwater discharge is highly seasonal with significantly higher flows in the wet season (December to April); and The mean annual discharge is 730,000 megalitres (ML). The Queensland Wetlands 2009 map series shows that Skardon River (Map 7374) is predominantly made up of an estuarine system. The Skardon River is a Tidal Creek, these typically have low freshwater inputs and are primarily influenced by tidal currents (Ryan et al., 2003). This agrees with the findings of the hydrological assessment, further demonstrating that the Skardon River is dominated by tidal processes and that freshwater flows are relatively low

26 Source: SRK Consulting Pty Ltd, 2013 Figure 19-16: Catchment delineation of the Skardon River and creeks to the south Sediment Transport Sediment transport in the Skardon River is driven by two primary processes. These primary processes are: Tidal currents that dominate the sediment transport, in an offshore direction in the channel through the ebb bar. Sand is transported as suspended load and bedload along the channel in the ebb bar until it reaches the offshore edge of the bar. Some of the sediment will then be deposited in deeper water on the offshore slope of the bar, promoting offshore growth of the bar, while some sediment will be transported in a net southerly direction due to wave action (as described below); and Waves that dominate the sediment transport along the offshore edge of the ebb bar as this is where the wave energy is highest. The waves drive a net southerly longshore transport along the shoreline (estimated to be approximately 10,000 cubic metres (m 3 ) (WorleyParsons, 2010)) due to the dominant wave direction (west-northwest) and the shoreline orientation. This longshore drift predominantly occurs in the summer (some also occurs in autumn) when the waves are largest. During winter and spring very little wave action occurs as the dominant wind direction is from the east and there is no offshore swell. The wave action allows sediment to be transported along the edge of the bar (it can be over the entire bar during extreme events) allowing sediment to be transported around the river mouth by longshore transport. A concept model of the aforementioned processes at the Skardon River ebb bar is presented in Figure

27 Figure Conceptualisation of sediment transport at the ebb bar of the Skardon River Sea Level Rise The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report, states that sea levels have risen by 0.19 m since the beginning of the 20 th century (Church et al., 2013). The rate of sea level rise has been increasing, with global average rates over the last century of 1.7 millimetres (mm) per year and rates between 1993 and 2010 of 3.2 mm per year. A number of projected sea level rise scenarios are detailed in the IPCC Fifth Assessment Report based on future emissions, resulting in the potential sea level rise by 2100 ranging from 0.28 to 0.98 m. The projections from Church et al. (2013) are presented in Table Table 19-4 Projected sea level increases to 2100 Sea Level Rise (m) Range Low Emissions Scenario High Emissions Scenario Min Max The land elevation where the proposed upstream BLF and RoRo facilities are to be located is in excess of 4 mahd and is therefore considered sufficiently high that sea level rise or storm tide inundation over the 12 year Project life are not considered to be issues

28 Coastal Soils Sampling for ASS has been undertaken as a screening for surface marine sediments within the Skardon River (RPS, 2015) and adjacent to potential development locations by Metro Mining. Available data has been screened for ASS under the Guidelines for Sampling and Analysis of Lowland Acid Sulfate Soils (ASS) in Queensland (QASSIT, 1998). The proposed Metro Mining barge facility and RoRo have been plotted over available ASS distribution mapping published by Geosciences Australia (2015) (Figure 19-18). The National Acid Sulfate Soils Atlas identifies portions of the proposed stockpile and conveyor alignment of the BLF and the RoRo as being located within or adjacent to a thin band of potential ASS material which surrounds the Skardon River along its western shoreline at these locations (Figure 19-18). A description of the physical and chemical characteristics of soils and sediments within the terrestrial, estuarine, coastal and marine environment is discussed in Chapter 4 Land. Skardon River Sediments Ten surface sediment samples, collected by RPS, from the river bottom and banks of the upper river reaches to the entrance and immediate offshore sediments, were sampled for ASS assessment. The findings outline the potential for actual ASS or potential acid sulfate soils (PASS) impact should marine sediments be disturbed, placed on-shore, or otherwise exposed to oxidation processes. Total Actual Acidity (TAA) is measure of the soluble and exchangeable acidity already present within soil/sediment. TAA for all samples remained below the QASSIT action criteria. Only one location exceeded the QASSIT Action criteria for net PASS. Further detail is discussed in Appendix B3 Marine Ecology and Coastal Processes. Figure Acid Sulfate Soils distribution and location of proposed development options 19-23

29 Shoreline and Bank Evolution Historical aerial photography from 1989 has been compared with recent aerial photography from 2014 to determine changes to the Skardon River mouth, banks and adjacent shoreline over the last 26 years (Figure and Figure 19-20). The photographs show that there has been little change in the mouth or banks of the Skardon River over this period, indicating that the river has been stable. The configuration of the channel offshore of the Skardon River mouth and the adjacent shoreline has also not changed significantly over this period, with the main difference being a slight change in the smaller channel configuration immediately to the northwest of the river mouth. Furthermore, the existing configuration of the shoreline to the north and south of the mouth of the Skardon River shows a depositional trend, with the shoreline showing signs of prograding and beach ridges being present (Figure 19-21). This shows that the orientation, location and width of the channel and adjacent shoals offshore of the river mouth, the river mouth and the adjacent shoreline have been stable (or prograding) over this period. However, there remains a risk that a change in the offshore channel alignment due to a future extreme event such as a tropical cyclone could result in significant change to the bed morphology in this area. As part of a previous investigation at Port Musgrave, WorleyParsons (2010) undertook an assessment of the longshore sediment transport along the shoreline to the north and south of the estuary mouth and found the following: There is high variability in the net annual sediment transport; The dominant net longshore transport direction is to the south (rates approximately three times higher than the northerly transport); and Average net annual longshore transport for the area is approximately 10,000 m 3 /year but the rate is strongly dependent on high energy events such as tropical cyclones or strong monsoon winds. As the orientation, configuration and exposure of the shoreline adjacent to the mouth of Port Musgrave is similar to the shoreline adjacent to the mouth of the Skardon River it is expected that similar longshore sediment transport conditions would occur at both locations. As such, the longshore transport conditions from Port Musgrave are considered to provide a reasonable representation of the conditions at Skardon River. Sediment which is transported along the shoreline to the mouth of the Skardon River will be transported into the complex configuration of sand shoals and the ebb tidal delta (Figure 19-21) and eventually bypass the river mouth. These shoals and the delta act as stores of sediment which allow sediment transported by longshore drift to bypass the river mouth during certain events. Fringing mangroves are present along the banks of the majority of the Skardon River (Figure 19-21). The mangrove vegetation will act to stabilise the sediment along the banks by attenuating both locally generated wind waves and tidal currents. The mangroves therefore help to create a depositional environment along the river banks. The presence of fringing mangroves throughout the estuary indicates that the banks of the river are currently stable and accreting

30 Figure Aerial Photograph of Skardon River from 1989 Figure Aerial photograph of Skardon River from

31 Figure Features of the coastline adjacent to the Skardon River Water Quality Regional Context Typical of northern Australian estuaries, both the chemical and physiochemical water properties of the Skardon River are driven by wet and dry season conditions. During the dry season, (typically eight months of the year) freshwater flows reduce significantly and may ceases to provide input to the system (Ridd and Stieglitz, 2002). The dry season has an average rainfall between 1.1 mm and 64.9 mm per month (April to November) with the lowest rainfall occurring in August. The bulk of the freshwater input into the rivers of Cape York occurs during the wet season, where they are inundated by short lived but sometimes intensive flooding (Wolanski and Ridd, 1986). Rainfall during these months averages between 93 mm and mm a month (December to April). The highest rainfall typically occurs in January. The Skardon River is described as a partially well-mixed tidal creek systems (Wolanski, 1986, Wolanski and Ridd, 1986). During the dry season, water cycles in the rivers are driven by evapotranspiration (Wolanski and Ridd, 1986) which leads to an increase in salinity within the upper reaches of the estuaries as the dry season progresses (Wolanski and Ridd, 1986; Cyrus and Blaber, 1992; Ridd and Stieglitz, 2002). This salinity maximum zone is a characteristic of the Skardon River and the adjacent Wenlock and Ducie Rivers during the dry season (Wolanski, 1986). Turbidity is also influenced by the seasonal rainfall, with turbidity levels lower during the dry season, particularly towards the end of the season (Cyrus and Blaber, 1992). The dry season reduction in ambient turbidity provides increased benthic light to seagrasses

32 The seasonal drivers described above influence ambient water quality on a broad temporal scale (seasons). However, it is also important to recognise that shorter scale and rapid changes in water quality can occur within these highly variable coastal environments on a daily, or even hourly basis, particularly within the mangrove and estuary systems Skardon River Ambient Water Quality Water quality of the Skardon River is discussed in detail in Chapter 9 Water Quality. The following provides a summary of the ambient water quality of the Skardon River. A combination of vessel based and logger based water quality physico-chemical and chemical marine water quality investigations have been undertaken within the Skardon River since Key findings of the investigations are: There is very high natural variability in turbidity in the Skardon estuary; Salinity within the Skardon River is dependent upon season (wet/dry) and distance upstream from the entrance. During the wet season, increased freshwater flows from the catchment act to reduce salinity within the river, mixing with higher salinity waters entering through the river mouth. During the dry, increases in salinity are recorded as freshwater flows into the system decrease and then stop, estuarine waters become more tidally influenced and any standing water left in the upper tributaries become affected by evaporation; The Skardon River presents a ph range of 7-8 within the entrance and lower estuary, reducing as sites progress up the estuary and beyond the existing barge facility ( ). There is a strong correlation between tides and ph; Dissolved oxygen reduces as distance from the entrance increases. There is a high correlation between Dissolved Oxygen and tidal exchange; Total nitrogen and total phosphorous concentrations recorded levels above the adopted ANZECC screening criteria within the Skardon River during the survey period, indicating a potential natural elevation of these nutrients in the relatively undisturbed catchment; The metals suite identified several elevations in metals, including copper and zinc compared to the ANZECC criteria. Similar trends in ratios are reflected in analysis for aluminium and iron, indicating a potential natural elevation of these nutrients in the relatively undisturbed catchment; and The full suite of hydrocarbons (C6-C36) remained non detectable from all survey locations during both the wet and dry seasons. Despite an absence of any substantial anthropogenic inputs, background water quality has recorded elevations in nutrients (total nitrogen and phosphorus) and metals (zinc, copper, aluminium and iron) as compared to the ANZECC criteria. These findings are considered a function of natural processes within northern tropical systems, rather than influences from contamination or catchment based affects. Water quality conditions of the Skardon River exhibit no obvious problematic affects associated with historical Kaolin mining, or existing land use, and the system is considered a near natural system with respect to water quality. In the absence of adjacent anthropogenic inputs, naturally occurring elevations in nutrients (nitrogen and phosphorous) and some metals are considered a 19-27

33 feature of these biologically productive, turbid and tidally dominated tropical estuary systems. Reductions in dissolved oxygen and variability in salinity, turbidity and oxygen reduction potential are considered representative of the naturally occurring processes of the Skardon River Sediments and Particle Size Distribution The sediments of the Skardon River are largely unimpacted by development, with limited impact from the nearby historical kaolin operations. Sediment investigations have been undertaken in 2014 and 2015 in the Skardon River, mouth of the Skardon River, ebb bar area (bed-levelling area) and offshore transhipment area. Analysis for particle size (gravel, sand, silt/clay) depicts a general decrease in silt and clays and increase in sands as locations progress from upstream to downstream nearer the river entrance (see Figure 19-22). Entrance and offshore samples confirm a dominant sand profile with equal proportions of minor gravel and silt/clay. The conditions presented at the river entrance reflect active nearshore bar conditions with extensive sorting of sediment fractions by wind, waves and currents leading to a dominant coarser sediment fraction. Samples adjacent to the proposed Metro Mining barge landing (RoRo) facility present relatively equal combinations of gravels (37% - shells) and sands (45%) and reduced silt and clay fractions (17%). Figure Skardon River sediment particle size and distribution Benthic video adjacent to the proposed Metro Mining facilities confirms the role of tidal currents in mobilising fine sediments, sands and even lighter gravels along the river bed. Sand waves and ripples can also be observed within multibeam bathymetric survey (see Figure 19-23) and side scan survey (see Figure 19-24) undertaken within the reaches adjacent to the proposed Metro Mining facilities. Such features are observed throughout the lower and mid estuary reaches of the Skardon River. These features are indicative of sand fraction mobilisation processes. Laboratory findings from particle size analysis are provided within Appendix B3 Marine Ecology and Coastal Processes. Still images extracted from benthic habitat video within the lower and mid estuary reaches have identified relatively coarse surface sands. These conditions reflect the distribution of current regimes anticipated

34 Figure Sand waves recording bulk mobilisation processes along the proposed channel alignment within the mid estuary reaches Figure Active bed ripples showing sediment mobilisation over the seabed adjacent to the proposed BLF (PaCE, 2014 side scan sonar) 19-29

35 19.7 Potential Impacts Some components of the proposed Project have the potential to directly and indirectly impact on coastal processes including sediment transport and water quality during construction and operational phases of the Project. An assessment of the potential adverse and beneficial impacts associated with the Project on the marine and coastal environment is provided in this section. The assessment details the magnitude and extent of any impacts. Cumulative impacts associated with this Project and the Proposed Skardon River Bauxite Project (SRBP) are discussed in Section 19-8 and mitigation measures or monitoring activities detailed in Section This section details the potential impacts to the coastal processes as a result of the Project activities Water Level The Project mining operations are not expected to significantly increase or decrease the existing natural water balance of the Skardon River through changes to surface water runoff, baseflow discharge or changes to the existing surface water groundwater interactions. These issues are covered in Chapter 10 Water Resources, Appendix E1 Groundwater Technical Report and Appendix E2 Surface Water Technical Report Local Hydrodynamics The Project will provide a minor small scale impact on the system hydrodynamics at the proposed BLF, RoRo and mooring locations. Minor changes in current flow from pile construction and barge moorings will result from a reduction in channel cross-sectional area, which in turn will result in localised increased tidal currents. The barges themselves may also induce altered current patterns and may lead to localised erosion of underlying soft sediments within the berth pocket, by way of increased current velocities during flood and ebb tidal flows and during manoeuvre of the barges and tugs via propeller wash. The RoRo facility will provide a partial barrier to current flow and dynamics. Rather than a laminar flow along the bank, the construction of the RoRo will develop current eddies and slight alterations to current and sediment movement processes. Depending upon prevailing currents, these processes may result in altered erosion and sediment deposition processes on a local scale. Similar minor changes in current velocities may also be expected surrounding the mooring blocks for barge moorings. Localised mobilisation of soft sediments may be expected within the immediate vicinity of these features. The proposed new wharf on piles and the associated barge mooring dolphins would result in a small localised reduction in channel cross-sectional area, which in turn will result in localised increased tidal currents. In addition, the proposed upgrades to the existing barge ramp could result in minor localised impacts to the tidal currents depending on the exact specification of the upgrade works. As the impacts will be small and restricted to the areas directly adjacent to the structures, and as the area already has marine port facilities present, the impacts on the coastal processes are not considered to be significant. The absence of the need for deepening or widening the berth pocket, or access route for the barge operation means overall hydrodynamic function will remain as per the existing predevelopment case. The proposed development is not expected to have any impacts on the river flushing as there is no change to the tidal prism of the Skardon River

36 Morphology and Longshore Transport Given no alterations in bathymetry is proposed within the ebb bar (i.e. no bed-levelling is proposed), no changes to bar morphology or sediment transport processes would be predicted Vessel Generated Waves The passage of barges within the Skardon River will generate wake waves depending upon vessel speed and water depth. Given the proposed production rates, barge sizes and operational period, an estimated 6 to 7 barge movements are anticipated through the river each day of operations (3 to 4 loaded and 3 to 4 empty). Refer to Chapter 17 Transport for further details on vessel movements. As mangroves are present along the majority of the banks of the Skardon River, vessel wake waves are expected to be attenuated by the established mangrove vegetation. However, several reaches of the proposed channel present limited mangrove cover, and various locations present exposed or unvegetated conditions (lower estuary and river entrance). Seagrass is also present within the lower intertidal and immediate subtidal areas. Given these parameters there is a risk that erosion of some exposed areas of the river bank or shallow beds could occur. The BLF, RoRo area, and the entrance to the Skardon River estuary present the most restricted portions of the estuary at a width of approximately 300 m. The remainder of the downstream river system width ranges between 400 to 750 m. Within the mid and upper estuary areas the proposed barge channel would come within 100 m of the river banks. The following presents a spatial risk assessment for vessel wake wave impact. The spatial risk assessment is presented in Figure and includes water depth, distance to channel, habitat type, shoreline condition and sediment type. Modelling for vessel wake waves was conducted by PaCE (2016) for four depth ranges expected through the river (4.5 m, 6 m, 8 m and 12 m) (Figure 19-25). The plot shows that although wave heights of up to 0.25 m can occur directly adjacent to the vessel, the heights quickly degrade to less than 0.07 m at 50 m away from the vessel sailing line and less than 0.05 m 150 m away from the vessel sailing line. There are two locations within the Skardon River where the navigation channel is relatively close to the channel bank, including: Upstream close to the proposed wharf the centreline of the channel is 80 m away from the west bank of the river. This area has a minimum depth of approximately 6 m. The wave height at the bank is predicted to be less than 0.05 m. This size of the anticipated wave is not expected to result in erosion of the bank, especially considering the stability and vegetated nature of the bank; and The mouth of the Skardon River is relatively constrained and as a result the centreline of the channel is 100 m away from the south bank of the river. This is a deep section of the river with a minimum depth of close to 8 to 12 m when the barge could navigate the entire river, and so the wave height at the bank is predicted to be less than 0.03 to 0.04 m. Again, this size wave is not expected to result in erosion of the bank. The majority of the Skardon River shoreline extends more than 300 to 400 m from the proposed sailing line. Ambient waves within the Skardon River are anticipated to be low given the protected nature of the waterway. Although wind generated waves up to 0.3 m have been observed within the lower 19-31

37 estuary and inner entrance during strong easterly conditions (Riku Koskela, pers. comm, 2016), such conditions are short lived (hours). Typical wave conditions within the lower estuary are predicted to be below 0.1 m. The mid estuary surrounding the proposed BLF is even more protected, and wave heights are expected to be lower. Estimates from protected estuarine systems of the Tweed River (NSW), similar to the conditions presented at the Skardon River (wider lower estuary and constricted mid and upper estuary), resulted in typical natural wind generated wave heights of less than 0.05 m (SMEC, 2012). Similar conditions are expected to occur within the protected waters of the Skardon River. The Project is not anticipated to affect waves within the study area or ebb bar environments. No bed- levelling or dredging is proposed which would influence bathymetry such that ambient wave dynamics would be effected. Figure Spatial distribution of vessel generated wave risk 19-32

38 Sediment Transport Notwithstanding the variations observed in the sediment sampling undertaken by PaCE, the sand and gravel fraction appear to dominate the channel areas throughout the Skardon River. Mangrove and bank environments may possess greater silt and clay fractions as materials deposit along these shorelines. However, these environments will not be open to significant perturbations beyond the initial construction period at the BLF and RoRo. Samples taken from within the Skardon River (i.e. the mouth of the Skardon River to the BLF) for assessment reflect shoreline sediment conditions, not exposed to the ambient current velocities predicted by hydrodynamic modelling. Consequently, estimates of particle size distribution, metals and nutrient concentrations are considered conservative, with these sediments not having been exposed to strong tidal currents and ambient shear stresses. Review of bathymetric survey data (multibeam sonar) has identified physical evidence of active sediment sorting and mobilisation along the proposed channel alignment. Features such as ripples, sand waves, isolated rock and broad rocky patches are indicative of active sediment migration processes. Modelling undertaken by Gulf Alumina indicates that sediments within the channel (barge area, mid estuary and ebb bar crossing) will be exposed to short lived episodic erosive forces during the minimum barge operating depth periods. As water levels increase, these forces are reduced, and erosion processes are not predicted. Scour is also predicted at the proposed transhipment area for laden vessels leaving the area; however, impacts are not anticipated to be significant given the typical Over time, regular sediment disturbance via propeller wash is anticipated to: Sort sediments and potentially armour the channel alignment (increase coarse fraction); Continue erosive processes until bed shear stresses reduce sufficiently (in deep unconsolidated sediments); or Encounter consolidated underlying strata such as clay or rock or gravels. While not considered a significant factor for coastal processes, it is noted the Project is also proposing one water release point from the site, being from a sediment dam associated with the MIA. Chapter 9 Surface and Groundwater quality and Appendix A3 Conceptual Erosion and Sediment Control Plan identify the design parameters and management processes for the sediment containment structures. Chapter 20 Draft Environmental Authority (EA) Conditions, identified the proposed mine water release monitoring associated with this release point. Based on the standards implemented under the ESCP and the conditions proposed in the Draft EA, the potential for this release point to have any significant impact on sediment levels within the Skardon River is considered low. Spillage of bauxite during loading or transhipment may impact upon the physical nature of the adjacent sediments, introducing additional gravel fractions to the sediment matrix. Given the inert nature of bauxite, spillages are not considered a contamination risk

39 Propeller Wash Vessel and Barge Movement Vessel movements generate a current field behind the ships propeller, this is commonly referred to as the propeller wash (Figure 19-26). While the impacts of these forces may not be significant for smaller vessels, the operation of tugs, such as proposed by Metro Mining (27m, 2400HP), has the potential to generate substantial bed shear forces and propeller wash velocities. Figure Propeller wash visualisation The impact from propeller wash is dependent upon a number of variables including: Water depth; Vessel speed Horsepower; Propeller size and depth; Under keel clearance; Sediment properties (particle size); Bed armoring; Ambient currents and bed shear stress; and Erosion potential

40 In conjunction with these factors, the proximity of sensitive benthic habitats helps define the likelihood and consequence of potential impact as a result of increased turbidity, reduced benthic light and altered erosion and deposition regimes. The Skardon River is a shallow estuary system with the potential to be influenced by propeller wash from larger vessels and bauxite barges. A significant portion of the outer limits of the access route through the outer ebb tide bar have been surveyed at <2.5m (MSL). These areas present increased potential for mobilisation due to propeller wash during the passage of vessels. Sediments through the outer bar are dominated by sands and gravel fractions, though patches of increased finer fractions have been identified. The risks of sediment mobilisation remain high due to the shallow depths. Modelling shows reduced currents and associated bed shear. This area is a natural zone for deposition as some materials move south over the bar and some are transported seaward from the Skardon River mouth. The bed is flat and limited features are described from the bathymetry. Increased risks from propeller wash may be experienced here. As the channel works its way from the outer ebb bar to the inner bar, the proposed route deepens slightly from 2.5 to 4.5m (MSL). Sediments remain dominated by sands though increased bed features show active transport of sediments (Figure 2-8). Currents increase within the inner bar and natural scour has developed deeper pockets. Reduced risks of propeller wash may be experienced here. Current logger data, hydrodynamic modelling and review of benthic bed features (sand waves, ripples, flat sections) indicate that the lower and mid estuary reaches are natural zones of sediment mobilisation. The currents (>0.5m/s to ~1.0m/s) and the bed features described within these reaches do not favour fine gran sediment deposition, and suggest potential lower risks of sediment mobilisation by propeller wash. Sediments are more likely to be dominated by coarser fractions. Water depths within the lower and mid estuary reaches are generally >4.5m (MSL), though a shallower patch (within the vicinity of the channel dog leg) may present increased mobilisation potential. The upper estuary reaches (toward the BLF and RoRo facilities) record lower ambient velocities (0.5 to 0.2m/s) and an absence of significant bed features as compared to the lower reaches (Figure 2-8). Due to these reduced velocities the upper estuary is likely to show reduced bed shear and an associated increase in fine fraction sediments. The risks of propeller wash may be considered greater from these reaches. As reported by PaCE (2016) for the proposed Gulf Alumina project, the predicted impact from propeller wash appears most significant during lower tidal stages. Analysis of four locations within the Skardon River at high water and mean sea level indicates a reactively low intensity erosion processes (i.e g sediment mobilised per every 1m of vessel track) (Table 19-5). While propeller wash forces are expected to cause increased bed shear velocities between m from the barge propellers, the suspended sediment generated through the water column is modelled at a range of 0 to 2.8 mg/l within the river (Pace, 2016). For locations over the ebb bar these concentrations may increase to 40 mg/l

41 Table 19-5 Predicted mass of sediment eroded and resultant SSC from the propeller jet Site Average Erosion Rate (kg/s/m 2 ) Mass of Sediment Eroded per metre of vessel track (kg) Predicted SSC resulting from the erosion per metre of vessel track (mg/l) MSL MHHW MSL MHHW MSL MHHW Barge Mid Mouth Ebb Bar Note that the calculations are for a single metre of the barge track The higher suspended sediment concentrations at the ebb bar site will not occur for long because sediments are predominantly made up of sand and as such will quickly settle out (medium sized sand settles at 0.03m/s (1.8m/minute)) once the barge has passed. When interpreting the results it is important to consider the following: Erosion resulting from the propeller wash of the barge is expected to predominantly be within the center of the navigation channel (predicted maximum width of approximately 15 m). The only area where an impact outside of the navigation channel would occur is adjacent to the BLF and RoRo when the barges maneuver onto the berths and propeller wash is perpendicular to the channel; Erosional processes associated with propeller wash are expected to occur over a 60 second period 6-8 times each day at the BLF and RoRo facilities; Once released, sediments would be open to deposition. Finer sediments will be mobilised to the current and be suspended within the ambient flow, heavier fractions may suspend for a short period before settling within or adjacent to the channel alignment. The currents of the Skardon River are high and would result in a broad distribution; It is expected that in the upstream areas there will be highly consolidated sediment under the softer surface layer assumed in this assessment. The consolidated sediment would be expected to have critical erosion thresholds in excess of 1N/m 2 and as such any erosion resulting from the propeller jet would be significantly reduced once the softer surface sediment has been eroded; Along the ebb bar where the highest bed shear stresses are predicted due to the propeller wash, it is likely that as the sand sized sediment is eroded by the propeller wash the bed would become armored as coarser gravel sized sediment is left (material on the ebb bar is up to 25% gravel). This would protect the bed from future erosion as the critical erosion threshold for resuspension of granule sized gravel is approximately 50N/m 2 ; and Resuspension of existing bed material due to propeller wash is not predicted from any location during Mean High High-Water. Measured mean dry season surface column turbidity was recorded at ~ 4 NTU, and total suspended solids concentration between 10 mg/l to 1 mg/l (overall site means for TSS recorded during vessel survey ranged between ~2 mg/l to 5 mg/l). These dry season TSS concentration and associated turbidity measures, appear to be at or above the predicted modelled propeller wash outputs of 0 to 2.8 mg/l (within the river). Given these findings, it is considered unlikely that the barge propeller wash impact would substantially elevate turbidity to levels significantly above ambient concentrations within the Skardon River itself

42 Operations at BLF and RoRo Facilities The operation of the proposed BLF and the RoRo will increase the potential for propeller wash. Operations would require the manoeuvring of barges and other supply vessels to facilitate loading, departure and arrivals. The barges will be operating both within the channel and perpendicular to the channel during these periods. Propeller wash during these periods may direct increased currents and bed shear forces over adjacent shallow water environments and associated seagrass beds. Acoustic Imaging (2015) undertook a limited extent of sub-bottom profiling in the area of the proposed BLF and RoRo facilities and in the area near the existing Skardon River Port facility. The area of sub-bottom profiling for the RoRo is shown in Figure 19-27, with Figure showing the depth of shallow sediments along the bank of the Skardon River where the RoRo is proposed has a maximum depth of approximately 1m. Any impacts from propeller wash in this area are likely to be limited to the 1 m of soft sediments, before encountering the harder sediments that are unlikely to be impact from prop-wash disturbance. Figure location of the sub-bottom profiling work at the proposed RoRo location 19-37

43 Figure The depth of soft sediments along the proposed RoRo shore location of less than 1m Given the limited potential volume of sediment that can be disturbed, the risk of any significant level of sedimentation occurring due to prop-wash is further reduced. The extent that these impact upon benthic light, deposition and ambient turbidity regimes will depend upon the timing of operations (high/low water), prevailing current speeds, direction of currents (ebb/flood) and the sediment matrix being disturbed. Figures have been developed as a schematic to demonstrate the potential impact areas adjacent to these facilities and are shown at Figure 2-60 and Figure 2-61 in Appendix J of Appendix B3 of this EIS Acid Sulfate Soils The river based sediment sampling undertaken by PaCE confirms elevated potential acid sulfate soils (PASS) concentrations within the upper estuary and adjacent to the proposed BLF and RoRo. Sediments within the proposed RoRo, conveyor alignments and barge loading areas have the potential to create acid drainage problems should these be exposed to oxidising conditions. However, given the proposed piling construction methods (refer to Chapter 2 Description of the Project) the risk is considered low. The Queensland Acid Sulfate Soil Technical Manual: Soil Management Guidelines (Dear et al., 2002) identifies piles as a low impact construction method for acid sulfate soils (ASS) impacted areas. The Australian Standard (AS) Piling Design and Installation (Standards Australia, 1995) is the guideline used to assist the use of piles in soils that contain pyrite or are saline. The guidelines also advise research on concrete performance in sulfaterich environments. The presence of minor ASS and PASS was also reported from limited shore based sampling undertaken by Metro Mining and indicates that shoreline construction, excavations and construction of any associated revetments may need to more broadly consider ASS and PASS distribution. The data reported from the vicinity of the potential barge loading and RoRo areas identified elevations within the upper 1.0m, with little impact risks being identified at depth. While sediments within the vicinity of the BLF and RoRo have the potential to create acid drainage problems should these be exposed to oxygenated conditions or oxygenating processes, given the 19-38

44 proposed piling construction methods the risk is considered low. Excavation works required for construction of the causeway and the base for the RoRo have a higher potential to generate acid runoff. Further details including sample results and proposed management and mitigation measures are contained in Chapter 4 Land Climate change, Sea Level Rise and Storm Inundation The land elevation where the proposed upstream port facilities (BLF and RoRo facility) are located is in excess of 4 mahd and is therefore considered sufficiently high that sea level rise or storm tide inundation over the 12 year Project life are not considered to be issues. While these facilities are modelled within the potential flood zone of the Skardon River (Chapter 11 Flooding and Regulated Structures and Appendix E2 Surface Water Technical Report), they are constructed on the assumption that during the wet season the RoRo will likely be under a variable level of water, and the BLF has flexibility to rise and fall within the modelled Skardon River levels. These facilities are considered unlikely to have any direct impact to or by changes in water levels within the Skardon River or associated coastal areas. The proposed Project infrastructure has been shown to result in negligible impacts at a local scale to the hydrodynamics, waves and sediment transport. These impacts are not expected to be exacerbated as a result of climate change Shoreline and Bank Evolution As discussed above, the lack of proposed bed-levelling operations significantly minimises the potential coastal process risks associated with the Project. Limited potential sediment movements from the construction of the BLF and the RoRo, and from prop-wash and wake impacts associated with barge movements are not considered to have potential to cause significant changes to the existing coastal processes associated with shoreline or bank evolution. Given no alterations in bathymetry is proposed within the ebb bar, no changes to bar morphology or sediment transport processes are anticipated Offshore Transhipment Area and Bulk Vessels The offshore transhipment area location was selected on the basis of benthic habitat and sediment surveys (undertaken by PaCE, 2015) which identified very low density benthic communities and sediments that are sand dominant. This location will minimise impacts to marine ecology from offshore anchoring and bauxite transhipment. Offshore transhipment of bauxite from barges to bulk vessels will not involve any permanent structures in the marine environment and therefore there are expected to be no impacts on coastal processes and the physical marine environment from structures. It is expected that the fine grained sediment in the offshore transhipment area will be eroded from the bed in the area impacted by the bulk vessel propeller wash, while the coarser grained sediment will remain with local bedload transport occurring. It is therefore expected that over time the sea bed will become armoured with coarser sediment protecting the sediment below from further erosion. Further information about the potential impacts on benthic habitat, marine ecology and Commonwealth marine waters associated with shipping is at Chapter 6 Marine Ecology and Chapter 7 Matters of National Environmental Significance

45 19.8 Cumulative Impacts Gulf Alumina is proposing to establish a very similar operation on the Skardon River and represents a similar investment in infrastructure and target tonnages. Gulf Alumina are proposing a purpose built barge operating from the existing facility footprint areas, rather than barges and tugs at a new development locations proposed by Metro Mining. Gulf Alumina are proposing bed-levelling to improve barge access over the ebb tide bar while Metro Mining is not. The bed-levelling proposes to achieve a depth of -2.2 mlat in a channel that is 70m wide and follows the path of maximum depth within the Skardon River based on bathymetrical data. The total volume estimated is 46,450 m 3. The shallowest bed level along the proposed navigation channel is -1.0 below LAT (maximum depth of material to be moved/dredged is therefore 1.2m). The bed-levelling activity is predicted to result in a relatively small, localised sediment plume and the ebb bar. The extent of the plume during bed-levelling is anticipated to be limited to the area directly offshore of the ebb bar. The plume does not extend within the Skardon River or along the shoreline to the north or south of the ebb bar. The bed-levelling activity, proposed by Gulf Alumina, is not expected to result in any impacts to the longshore sediment transport at the shoreline to the south or around the ebb bar adjacent to the Skardon River. The construction process for both projects is very similar with regards to barge infrastructure. A short construction period during the dry season would be targeted by both operations. The Gulf Alumina project presents reduced clearing on mangrove habitat by way of construction of the BLF access corridor and associated RoRo facility for the supply of equipment and materials. The Gulf Alumina facility is situated at the start of seagrass habitat distribution, and as such lesser seagrass will be passed by barges and vessel traffic. Should both projects proceed over the same period the Skardon River would be exposed to a significant increase in vessel traffic. To meet the basic annual tonnages and weekly bulk carrier loading targets described by the proponents, up to 100 barge movements would be required within the Skardon River each week (~3,600 movements annually). These movements would be accompanied by additional movements associated with fuel and materials supply. Bulk carriers and coastal freighters service the existing trade requirements within the Gulf of Carpentaria for bauxite export, fuel, cattle and general supplies. These vessels operate within designated shipment routes several km to the west of the proposed transhipment locations. The transhipment areas are both undeveloped locations largely undisturbed by anthropogenic processes. Approximately 140 bulk carriers are required to service both projects each year (70 each for SRBP and the Project). The nearby port of Weipa processes approximately 500 bulk carriers annually, exporting some 30 million tons of bauxite. The additional carriers required for the SRBP represent an approximate 14% increase in bulk carrier movements for the region. A further 14% is attributable to the Project, increasing bulk carrier movements within the wider region by nearly 28% (both projects combined). The impacts to coastal processes and the physical marine environment associated with such traffic volumes include vessel wake wave impacts, propeller wash turbidity and water quality impacts. It is assumed that both projects would utilise the same navigation channel (other than the section between Gulf s and Metro Mining s wharves) which would double the incidence of propeller wash within the navigation channel. Both projects would also present impacts to adjacent seagrass beds 19-40

46 with respect to propeller wash. Metro Mining s proposed tug and barge operation is expected to present a smaller footprint for propeller wash. Propeller wash has been described as a localized impact within the navigation channel given the identified conditions and the results of modelling with regards to impacted water quality. Alteration to mobilisation and deposition processes in specific areas, such as the wharf facilities has the potential for longer-term impacts to seagrass beds. The operation of transhipment zones will be duplicated, as will the potential for propeller wash during departure of the bulk carriers. However, given an absence in significant benthic habitat, the localised impact of propeller wash, the broad expanse of immediate alternative habitat and the distances between the two operations, the impacts attributable to propeller wash within the transhipment areas may be considered separate processes and an effective increase in marine pressures will not occur. The distances between the two locations will facilitate mitigation of impacts. Propeller wash impacts from the transhipment process are not considered cumulative. Neither project presents a significant impost on water quality outside the process of propeller wash. The relatively close proximity of both projects in the Skardon River could result in a cumulative impact to water quality due to construction and operational spillages or chemical releases. This is particularly the case given the ebb and flood of the river whereby the tides will move any impacts up or down stream past the other operations. Generally the likelihood of such events occurring are small, and with appropriate mitigation practices and operational standards any increase will be of a minor concern. Whilst the increase risks of hydrocarbon spillages may be considered of higher importance given the doubling of infrastructure and hydrocarbon movements through the river it is unlikely that two significant spill events would occur at the same time. Notwithstanding having two operations capable to respond to a larger spill event will act to reduce the overall cumulative risk. Both projects are expected to implement onshore sediment management control at the marine infrastructure areas, which will minimise potential for cumulative impacts. The barges exporting bauxite will provide the bulk of vessel movements for both projects. These vessels are relatively large and slow, with both projects expected to operate at speeds of between 4-6 knots in the River, with neither project resulting in significant vessel wake wave heights at the shoreline. As bed-levelling is only proposed for the SRBP, there will not be cumulative impacts from multiple bed-levelling operations. As for propeller wash the two proposed transhipment locations would generally experience only localised impacts to water and sediment quality. The sites are separated over several kilometres and the risks of potential pollutant releases are perceivably very small. Water and sediment impacts from the transhipment process are not considered cumulative

47 19.9 Management and Mitigation Measures The management measures discussed in the following sections are responding to the potential impacts identified in Section In some instances, the lack of any identified impact has resulted in no specific management or mitigation being required. In addition, many of the management and mitigation measures that are indirectly relevant for coastal processes have already been identified in other Chapters within this EIS, and where appropriate reference has been given to these chapters. The overarching approach that Metro Mining is taking for the coastal environment is to undertake regular and ongoing monitoring to confirm our current assessment of minimal impacts. If, through the monitoring process, an unexpected impact is identified, Metro Mining would propose to notify the regulatory authority and implement an appropriate and agreed control Water Level As the Project activities are not expected to alter the existing natural water balance of the Skardon River no specific management or mitigation measures are proposed. Mitigation measures associated with surface water and groundwater that supports this position are discussed in Chapter 10 Water Resources, Appendix E1 Groundwater Technical Report and Appendix E2 Surface Water Technical Report Local Hydrodynamics The impact assessment, confirmed in Section of Appendix B3 Marine Ecology and Coastal Processes, determined that the BLF, RoRo and transhipping moorings will present minimal, localised impacts to the existing hydrodynamics Management measures that will be adopted for the RoRo facility are focussed on ensuring the change in the bank profile is minimal and therefore there is no discernible change to the local hydraulic regime (i.e. velocities and depths). Further details on the construction and management programs for the RoRo are contained in Chapter 2 Project Description and Appendix B3 Marine Ecology and Coastal Processes. Management measures for the BLF are centred around the decision to utilise piles in the design as opposed to extending the causeway through to the berth pocket. While there is 100m of causeway proposed, the potential for this relatively small extension, through relatively dense mangrove vegetation, from the landward side to impact on the river hydrodynamics is considered minimal. The use of piles in the design was chosen to minimise the loss of cross-sectional area within the river at the location of the berth pocket. This therefore minimises the extent of change to the local hydraulic regime. Further details on the construction and management programs for the BLF are contained in Chapter 2 Project Description and Appendix B3 Marine Ecology and Coastal Processes. Temporary moorings are proposed at the anchorage area for the floating cranes, as is a single mooring between the mouth of the Skardon River and the anchorage area, and cyclones moorings within the Skardon River. Details of the mooring locations and design are included in Chapter 2 Project Description. Appendix B3 Marine Ecology and Coastal Processes, describes the potential impacts from these moorings. The Marine Monitoring Plan will incorporate monitoring of sediments and benthic ecosystems around the relevant marine infrastructure

48 Chapter 10 Water Resources identifies a potential risk of obstructing or constricting Skardon River flow patterns through the construction of haul road crossings. Management for construction of the proposed haul road crossings has been detailed in Chapter 2 Project Description and Appendix A3 Conceptual Erosion and Sediment Control Plan. Culverts appropriately sized for the dry season, and low-flow crossings that are designed to overtop during the wet season, are the basic design criteria to maintain the existing hydrodynamics within the Skardon River. No construction or constriction of the existing flow regime is expected to occur. The ESCP then details how these works will be undertaken to ensure no significant sedimentation occurs within the Skardon River Morphology and Longshore Transport No alterations in bathymetry is proposed within the ebb bar (i.e. no bed-levelling is proposed), and no changes to bar morphology or sediment transport processes are predicted. Consequently no management or mitigation measures are proposed. The Marine Management Plan proposes to regularly monitor sediment levels and benthic habitats at the river mouth, and into the marine transhipping anchorage points Vessel Generated Waves The Project is not expected to affect waves within the study area or ebb bar environments. Notwithstanding the following mitigation measures are proposed to prevent damage of the coastal environment as a result of vessel generated waves: Vessel speeds, via the vessel traffic management plan as shown in Figure , (generally 4 to 6 knots within the Skardon River and less than 4 knots within 500 m of seagrass beds) and operational area restrictions to minimise any potential increased bank erosion due to the barging activity. This should be defined based on the barge vessel size and capacity as well as the transport frequency; Establish defined navigational routes that maximises the extent to which ships remain within the deep water during transit; Where practicable coordinate vessels movements outside of low tides; and Wherever possible existing native riparian vegetation around the BLF and RoRo is to be maintained. This is especially important for mangrove vegetation as it will help to prevent bank erosion due to locally generated wind waves and vessel generated waves from the barges. To identify any potential impact of vessel wakes and bank erosion, it is proposed to incorporate monitoring of the banks along the Skardon River within the propose Marine Management Plan, and, if any new areas or significantly increased existing areas of erosion are detected, to develop an appropriate action plan in consultation with the regulators

49 SKARDON RIVER knots 6 knots 4 knots 4 knots 4 knots Barge Loading Area Legend Mine Infrastructure Area Barge Loading Area Vessel Route Saltpans Mangrove Haul Road Metro Mining Mine Lease Area Bathymetric Grid Logistics Barge Facility <2m LAT - Green >2m LAT - Red R Details Date 1-01/04/ DRAWN COPYRIGHT CDM SMITH This drawing is confidential and shall only be used for the purpose of this project. DESIGNED APPROVED Notes: MD MD - CHECKED CHECKED - DATE - 01/04/ / ,000 Metres A3-1:35,000 GCS GDA 1994 MGA Zone DISCLAIMER CDM Smith has endeavoured to ensure accuracy and completeness of the data. CDM Smith assumes no legal liability or responsibility for any decisions or actions resulting from the information contained within this map. DESIGNER Figure Speed management plan DATA SOURCE MEC Mining; QLD Government Open Source Data; Australian Hydrological Geospatial Fabric (Geofabric) PRODUCT SUITE V2.1.1 DRG Ref: BES R1_VESSEL_SPEED CLIENT F:\1_PROJECTS\BES150115_Bauxite_Hill\GIS\DATA\MXD\FINAL\ERA\BES R1_VESSEL_SPEED.mxd