7 Marine and Littoral Physical Environment 7.1 Introduction · Simandou SEIA Volume III Port Chapter 7: Marine and Littoral Physical Environment 7-3 7.2.2 Legal and Other Requirements

Simandou SEIA Volume III Port Chapter 7: Marine and Littoral Physical Environment

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7 Marine and Littoral Physical Environment 7.1 Introduction This chapter presents an assessment of the changes in the marine and littoral physical environment resulting from the construction and operation of the Simandou Port and the likely resulting impacts to: geomorphological features, such as beaches and sandbanks; water quality; and sediment quality. This chapter focuses on the impacts to the above features and describes the pathways in which the impacts can occur. Changes to the wave, tidal flow or sedimentary regimes do not necessarily indicate an impact. An impact will only occur if a valued receptor is affected by the change in the physical process described. Valued receptors are defined using the criteria discussed in Section 7.2.3.2. Impacts to fresh water resources are discussed in Chapter 6: Water Environment and impacts to terrestrial soils are discussed in Chapter 5: Geology, Soils and Mineral Waste. Impacts to marine and littoral biodiversity are discussed in Chapter 13: Marine and Littoral Biodiversity. The remainder of this chapter is structured as follows: Section 7.2 describes the assessment approach; Section 7.3 presents the baseline situation; Section 7.4 presents the assessment of impacts of the port prior to mitigation; Section 7.5 describes the planned approach to mitigation of these impacts and the resulting residual

impacts; and Section 7.6 summarises the findings of the assessment. 7.2 Approach 7.2.1 Study Area The marine and littoral physical environment study area has been determined with reference to modelling studies and expert geomorphological assessment. As such this chapter defines the study area based on the modelling and predicted area of significant impacts and is also in line with the study area presented in Chapter 13: Marine and Littoral Biodiversity. Figure 7.1 provides an overview of the study area. This SEIA assesses the first offshore disposal site identified although additional disposal sites may be required in the future. Additional disposal sites will be identified through a siting criteria exercise used to support the identification of the proposed dredge disposal site. Future disposal sites are expected to be located in waters of greater than 20 m CD in a zone 15 km or more from the coastline of Kaback. Baseline surveys will be conducted at future sites as a means of addressing impacts on any sensitive habitats as well as the extent of the potential plume. This assessment will be supported with modelling exercises to establish potential impacts, especially if the plume may extend beyond the domain of the existing model. Additional dredge disposal sites will be subject to the permitting requirements in Guinea and dredge disposal at all sites will also be conducted in line with the Project Dredging and Spoil Disposal Management Plan (DSDMP).

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Figure 7.1Emplacement du port et du chenal d'approche /Location of the Port and Approach Channel

Infrastructures portuaires / Port InfrastructureCanal de dragage / Dredging ChannelSite de rejet des boues de dragage / Dredge Disposal SiteBathymétrie / Bathymetry

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7.2.2 Legal and Other Requirements In addition to the national legislation and company policies and standards described in Chapter 1: Introduction, the following legislation, standards and guidelines have been applied to the marine and littoral physical environment assessment. 7.2.2.1 National Legislation The Code for the Protection and Development of the Environment, Ordinances 045/PRG/87 and

022/PRG/89 (also known as the Environmental Code) establishes the administrative and legal framework in Guinea and sets out the fundamental legal principles to ensure the protection of environmental resources and the human environment.

Decree 201/PRG/SGG/89, concerning preservation of the marine environment against all forms of

pollution, sets out the legal framework for the control of pollution in the marine environment.

Article 4 states that vessels within Guinean territorial waters must comply with the Guinean Environmental Code.

Chapter II deals with discharges from vessels and accidents at sea. Article 14 of the Decree prohibits

hydrocarbon releases to the marine environment, except under very specific circumstances.

Chapter III deals with discharges from land based structures to the marine environment. Chapter III makes provisions for discharges from land based structures that have the potential to impact the marine environment to be prohibited or requiring a permit by the Environmental Regulator.

Chapter IV deals with discharges from offshore platforms or structures used for exploration or

extraction purposes. Article 30 prohibits any hydrocarbons or mixed discharges that may impact public health, marine fauna or flora or impact the coastal economic development or tourism.

Annex I lists substances for which discharges are prohibited.

Annex II lists substances for which discharges are subject to permitting.

Merchant Shipping Code Article 68 relates to the disposal of waste and other materials in the sea. Order of 22 June 2011 On Preventing Marine Pollution from Ships Article 8 relates to the disposal of

hydrocarbons by ships in maritime waters. Article 16 relates to the disposal of harmful liquid substances in the sea.

Public Health Code Article 45 relates to the disposal of effluent from sanitary works. Article 47 relates to

the disposal of effluent from purification plants. Articles 98 and 102 relate to waste produced by utility activities likely to impact on public health that are part of development projects.

Water Code Article 31 relates to the evacuation and discharge into the waters, at ground surface level,

to great depths of any material that could cause pollution; and Article 32 relates to the disposal of waste into inland waters

7.2.2.2 International Legislation and Standards The United Nations Convention on the Law of the Sea (UNCLOS) is the international agreement that

defines the rights and responsibilities of nations in their use of the world's oceans, establishing guidelines for businesses, the environment, and the management of marine natural resources. Part XII provides guidance on the protection of the marine environment.


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Guinea is a Party to the MARPOL 73/78 Convention, which is the main international convention covering prevention of pollution of the marine environment by ships. The Convention includes regulations aimed at preventing and minimising pollution from ships, both accidental pollution and from routine operations. Annex I to Annex V to the Convention require that ports provide adequate facilities for the reception and management of shipborne wastes.

Convention for the Cooperation in the Protection and Development of the Marine and Coastal

Environment of the Western and Central African Regions (also known as the Abidjan Convention) covers the marine environment, coastal zones and related inland waters falling within the jurisdiction of the States of the West and Central African Region, from Mauritania to Namibia inclusive. It is a comprehensive umbrella agreement for the protection and management of the marine and coastal areas and lists the sources of pollution which require control: pollution from ships, dumping, land-based sources, exploration and exploitation of the sea-bed, and pollution from or through the atmosphere.

In the absence of national or regional standards and guidelines on water and sediment quality, the following international standards are considered appropriate and have been applied as relevant. The OSPAR Convention is a Regional Convention that has worked to identify threats to the marine

environment and has organised, across its maritime area, programmes and measures to ensure effective national action to combat them. The OSPAR Commission is a mechanism by which these actions are achieved. The OSPAR commission has developed guidelines for the disposal of dredged material and has summarised the current concentration ranges used by signatories of the OSPAR Convention in the assessment of dredged material for dumping at sea. These ranges can be used as an indication of sediment quality and have been applied during the following assessment.

The Canadian Council of Ministers of the Environment (CCME) are responsible for setting guidelines

relating to contaminant levels for both water and sediments, in aquatic as well as terrestrial and atmospheric ecosystems. Canadian Environmental Quality Guidelines have been developed to provide goals for water and sediment quality in marine environments and are widely followed at an international level.

European Union Directive on Environmental Quality Standards (Directive 2008/105/EC) established a

list of priority substances in List II as an Annex to the Water Framework Directive (WFD). The UK has set water quality standards for the protection of saltwater life for List II substances. These standards can be applied to international projects as a guideline for the protection of saltwater life.

7.2.2.3 IFC Performance Standards and Guidelines IFC Performance Standard 1: Social and Environmental Assessment and Management Systems

establishes the importance of (i) integrated assessment to identify the environmental and social impacts, risks, and opportunities of projects; (ii) effective community engagement through disclosure of project-related information and consultation with local communities on matters that directly affect them; and (iii) management of environmental and social performance throughout the life of the project.

IFC Performance Standard 3: Resource Efficiency and Pollution Prevention outlines a project-level

approach to resource efficiency and pollution prevention and control in line with internationally disseminated technologies and practices.

IFC EHS Guidelines for Ports, Harbours and Terminals provides a summary of environmental, health

and safety EHS issues primarily associated with port and terminal construction and operations, along with recommendations for their management.

7.2.2.4 Corporate Standards Rio Tinto Best Practice for Dredging – A Rio Tinto Marine Stewardship Initiative (2011) provides a set of

guidelines for Rio Tinto’s current marine operations, which encompass shipping, as well as port establishment and operational activities. This document presents considerations normally associated


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with dredging programmes together with an associated set of Guiding Principles, developed to assist with corporate dredging activities.

Rio Tinto Standard E10 - Water Use and Quality Control (2008) covers all water management activities

for all types and sources of water. The intent of this standard is to ensure efficient, safe and sustainable management and protection of water resources and ecosystems in and around Rio Tinto operations. This requires an understanding of the water resources, their spatial and temporal interrelationships, their ownership in the region and the needs of catchment stakeholders.

Standard E9 - Land use stewardship (2008) aims to develop management plans, programmes and

procedures to ensure sustainable stewardship of the land that Rio Tinto owns, leases or manages. This requires an understanding of the current use and value of the land combined with its potential to fulfil corporate, community and other stakeholders’ expectations for beneficial land-uses that can be supported and sustained into the future.

7.2.3 Prediction and Evaluation of Impacts 7.2.3.1 Overview The methodology adopted for the assessment of impacts on the marine and littoral physical environment consists of: establishing baseline conditions for the port study area;

predicting and evaluating the potential magnitude of changes in baseline conditions from construction

and operation of the port, with inputs from modelling studies for the dredging and spoil disposal operations;

evaluating the significance of the effects on valued receptors pre-mitigation; identifying measures that will be taken to avoid, reduce, offset or compensate for adverse impacts and

to provide or enhance benefits from the port; and assessing residual impacts. 7.2.3.2 Value of Receptors The value of the marine and littoral physical environment receptors is judged by taking into account their importance in environmental functioning and to the local or wider community and biodiversity. The valuable marine and littoral physical environment receptors considered are geomorphological features (eg sandy beaches, mangrove shoreline, mudflats and sandbanks), water quality and sediment quality. This chapter describes changes to the physical processes, such as waves, tidal flows and the sedimentary regime due to the construction and operation of the port. However, as stated above, an impact will only occur if a valued receptor is affected by the changes to physical process caused by the port. 7.2.3.3 Magnitude of Impact Magnitude describes the change that is expected to occur to the receptor as a result of the port development. For the marine and littoral physical environment the magnitude is predicted quantitatively where possible, or qualitatively where this is not possible. Magnitude encompasses various possible dimensions of the predicted impact including: the nature of the consequence (how receptors are affected); the size, scale or intensity of the effect; geographical extent and distribution; temporal extent (duration, frequency, reversibility); and


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the probability of the impact occurring as a result of non-routine events. 7.2.3.4 Evaluation of Significance The methodology presented in Chapter 1: Introduction has been applied to this assessment using the definitions shown in Table 7.1, Table 7.2 and Table 7.3 for determining the value of the marine and littoral physical environment receptors and the magnitude of impact. Application of relevant legislation and standards are also considered in evaluating significance, including national and international legislation and standards, IFC guidelines and Rio Tinto corporate standards.


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Table 7.1 Evaluating Significance of Impacts on Geomorphological Features

Magnitude of Impact

Value of Geomorphological Feature

Negligible Small Medium Large

Impact is within the normal range of day to day variation.

Affects a small proportion of the feature, but without loss of viability and / or function to species or communities.

Affects a substantial proportion of the feature and the viability and / or function of part of the feature is reduced, but does not threaten the long-term viability of the feature or the species and / or communities dependent on it.

Affects the entire feature or a substantial proportion of the feature, where the viability and / or function of the feature is reduced and the long-term viability of the species and / or communities dependent on it are threatened.

Negligible No specific value attached to the geomorphological feature. Not Significant Not Significant Not Significant Not Significant

Low

The geomorphological feature has no global, regional or national value and is common or abundant. The feature has limited value to species or communities with no real conservation significance in expert opinion.

Not Significant Not Significant Minor Moderate

Medium

The geomorphological feature is locally rare, small or scattered, and is of value to some species of conservation interest or communities. The function provided by the feature is important locally although alternatives exist in the wider geographic region.

Not Significant Minor Moderate Major

High

The geomorphological feature has a globally limited distribution or is locally unique and a significant proportion of the feature in the study area will be affected. The geomorphological feature supports species of conservation interest and / or is of importance to communities. There are no suitable alternatives available.

Not Significant Moderate Major Critical


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Table 7.2 Evaluating Significance of Impacts on Water Quality

Magnitude of Impact

Value of Water Quality



Affects a small area of water quality, or a large area of water quality but without the loss of its viability and / or function to species of the community.

Affects a large area of water quality in the region and the viability and / or function of the water resource is reduced, but does not threaten the long-term viability of the water resource or the species and communities dependent on it.

Affects regional water quality, where the viability and / or function of the water resource is reduced and the long-term viability of the species and / or communities dependent on it are threatened.

Negligible No specific value or importance attached to the quality of the water. Not Significant Not Significant Not Significant Not Significant

Low Existing water quality is poor and has limited value to species or communities with no real conservation significance in expert opinion.


Medium

Existing water quality is moderate and is of some value to species of conservation interest or communities. The function provided is important locally although alternative areas exist in the wider geographic region.


High

Existing water quality is good and is of high value to species of conservation interest or communities. The function provided is important locally and there are no suitable alternatives available.



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Table 7.3 Evaluating Significance of Impacts on Sediment Quality

Magnitude of Impact

Value of Sediment Quality



Affects a small area of sediment quality, or a large area of sediment quality but without the loss of its viability and / or function to species and the community.

Affects a large area of sediment quality in the region and the viability and / or function of the resource is reduced, but does not threaten the long-term viability of the resource or the species and communities dependent on it.

Affects regional sediment quality, where the viability and / or function of the resource is reduced and the long-term viability of the species and / or communities dependent on it are threatened.

Negligible No specific value or importance attached to sediment quality. Not Significant Not Significant Not Significant Not Significant

Low

Existing sediment quality is poor and has limited value to species or communities with no real conservation significance in expert opinion.


Medium

Existing sediment quality is moderate and is of some value to species of conservation interest or communities. The function provided is important locally although alternative areas exist in the wider geographic region.


High

Existing sediment quality is good and is of high value to species of conservation interest or communities. The function provided is important locally and there are no suitable alternatives available.



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7.3 Baseline 7.3.1 Data Sources The baseline information presented in this chapter draws upon a number of existing data sources, as well as studies and reports that have been commissioned for the Project. Survey work has been undertaken in the Guinean Coastal Region to evaluate areas being considered as locations for the port development since 2008, including physical environment surveys both in the wider region and in the specific area of the port development (see Table 7.4). Note that some of these studies were conducted in association with an earlier proposal to establish the port at a location to the south of the current proposal site. While some environmental data are not specific to the port site considered in this SEIA, the data do provide a good indication of the range of environmental features evident in nearshore waters within the vicinity of the proposed port and as such are considered to provide a reliable baseline. On-going studies are seeking to further establish the understanding of the baseline and will feed into the Social and Environmental Management Plan (SEMP) and management of potential impacts in the longer term. In addition modelling studies have been conducted to indicate potential changes to coastal geomorphology and salinity and turbidity in the Morebaya River. Sediment plumes and sedimentation created by dredging activities have also been investigated. This chapter draws on the modelling studies conducted by Deltares (2012) (1) which are on-going and will continue to inform project design and mitigation measures as appropriate. 7.3.2 Geographical Setting The Republic of Guinea is divided into four distinct regions based on specific human, geographic and climatic characteristics. The port is situated in the geographic region known as Maritime (or Lower) Guinea, an area which encompasses the entire Guinean coastline. The Guinean coastline stretches for approximately 320 km between Guinea Bissau in the north, and Sierra Leone in the south. The port area lies in the coastal region close to the mouth of the Morebaya River in the Maférinyah Sub-Prefecture, approximately 35 km south of the capital, Conakry. The low lying coast fronted by a wide coastal shelf formed in response to sea level fluctuations in the past 20 000 years. The nearshore environment has accumulated large quantities of muds in recent geological time in response to sea level rise since the last ice age. Wave energy dissipation on the wide shelf keeps the coastline one of low energy and predominantly soft muddy shorelines. The marine and littoral physical environment in the study area is located on a shallow shelf bordering a mangrove coastline. The coastal shelf waters are typically less than 20 m deep and extend up to 130 km offshore. The inland topography transitions from mountainous areas in the east via a series of plains to the low-lying mangrove areas that border the shoreline, transected by the Morebaya River system. The Morebaya is a tidally dominant estuarine system characterised by high velocity tidal flows and relatively low freshwater input, especially in the dry season. The Morebaya River is fed from the coastal plains. Rivers further south include the Melacorée and Tana Rivers, which are fed from coastal plain, and the Forécariah River, which is a piedmont river fed by upland mountainous areas. There are settlements throughout the study area who use the littoral and coastal plain areas for agricultural activities, such as rice fields, and the beaches and mudflats for fishing activities, such as the collection of bait, positioning of fish traps and for the landing of fishing vessels. The wider coastal region and rivers are used for fishing by local fisherman. Large scale commercial fishing is concentrated in the offshore waters in the northwest of Guinea’s Exclusive Economic Zone (EEZ).

(1) Deltares (2012). Preliminary Modelling in Support of SEIA. Internal Project Engineering Studies.


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Table 7.4 Summary of Physical Environment Baseline Surveys and Studies Completed within the Guinean Coastal Region and at the Port Study Area

Topic Period and Timeframe

Level of Effort within the Study Area

Sampling Locations Survey Methodology Field team

Water Quality 2008 - dry season (March 15 to June 12) and wet season (September 24 to October 16)

14 stations were sampled in 2008, during both the dry and wet season 84 CTD profiles covering both the water and sediment sampling stations during the dry season

Estuarine areas of the Tana, Melacorée and Forécariah rivers.

The mangrove channel of the Yélitono and Mabala island region.

The marine area offshore Mabala islands.

Water samples were collected on the surface and at the bottom, where possible. Samples were analysed for nutrients, carbon, chlorophyll a, pheopigments and total suspended solids (TSS). For deep-water sampling, a single sample was approximately 1 m from the bottom for analysis of TSS and dissolved oxygen in the field laboratory. CTD data collected were temperature, salinity and turbidity versus depth.

Environnement Illimité SNC-Lavalin Environment

2011 – end of the wet season (November 27 to 30, 2011)

12 stations

CTD profiles were taken at each of the sediment sampling stations between September 23 and October 8

Forécariah and Morebaya rivers.

Île Kaback mangrove channels and streams.

One vertical profile per station was taken using a multiparameter probe to measure temperature, conductivity and oxygen. Water samples were collected from the middle of the water column for analysis of conductivity, total suspended solids (TSS), total dissolved solids, chlorophyll a, major ions and metals. Secchi disk measurements and visual water colour determination were also undertaken. CTD data collected were temperature, salinity and turbidity versus depth.


Sediment Characterisation

March 27 to April 14 2012

21 stations The proposed navigation channel and dredged sediment disposal area.

Grab samples were taken and photographed. Samples were analysed for grain size, organic matter content and contaminants.


September 22 to October 18 2011

71 stations West and south of Île Kaback and in the Forécariah River.



December 7 to December 2011

26 stations West and north of Île Kaback and in the Melacorée River.

Grab samples were taken and photographed. Samples were analysed for grain size and organic matter content


March 13 to April 6, and May 17 to June 12 2008

159 stations Coastal and offshore area and mangrove channels south of Kaback.

The Forécariah and Melacorée Rivers.



Sediment Dynamics

March 26 to May 3 2012

84 transects with ADCP Morebaya River Moored ADCP and transects. Environnement Illimité SNC-Lavalin Environment

June 9 to 23 2011 (dry season) and August 25 to September 8 2011 (the wet season).

1 moored ADCP

89 transects with ADCP Forécariah and Melacorée Rivers and offshore Matakang Island.

Moored ADCP and transects.

Bedload was calculated using dune tracking analysis (assessing changes in dune bed topography recorded during sequential bathymetric surveys).



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There is a defined wet season in the area during which there may be periodic seasonal flooding of much of the coastal area. This is not only an important cycle of use of the bogoni rice fields but also alters the nature of the local hydrological regime at these times. The baseline description with this chapter assumes the base hydrologic regime rather than conditions under an inundated flood plain. Figure 7.1 provides an overview of the study area. 7.3.3 Climate Guinea experiences a tropical equatorial climate, with a distinct wet season that typically extends from May to October. Climate data are available for Conakry, which is located approximately 35 km north of the port site and Figure 7.2 presents monthly rainfall and temperature data for Conakry between 1961 and 1990. Daily rainfall is very high during the height of the wet season (July and August) with peaks of up to 470 mm per day in July (1). Rainfall is very low or zero during the dry season between December and April. Air temperatures are reasonably constant throughout the year with a range of approximately 22 to 32°C. Figure 7.2 Historical Climate Data for Conakry – Mean Temperature and Rainfall, 1961-1990

Source: http://www.weather.gov.hk/wxinfo/climat/world/eng/africa/w_afr/conakry_e.htm

Seasonal variation, particularly in terms of precipitation, results in associated fluctuations in freshwater river flows. The Morebaya River is supplied by a small catchment that drains rapidly into the Morebaya in response to rainfall. As such, freshwater river flows primarily occur during the wet season and are greatly reduced during the dry season. There is a strong seasonal variation in the prevailing wind direction with northwesterly winds in the winter months and stronger southwesterly winds in the summer months (1). Storms in West Africa can result in a sudden, sharp increase in wind speed and tend to occur during the onset and decline of the rainy season (June to October). Gust wind speeds associated with such storms can be in the order of 25 to 40 m/s. Global climate change may alter rainfall patterns in the region, especially during the dry season when projections suggest that rainfall may increase by up to 10%. In the wet season rates are predicted to remain more consistent but may decrease by up to 5%. Changes in rainfall are anticipated to be accompanied by

(1) Social and Environnemental Baseline Studies (2008).

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an increase in storm ferocity and storm surges (1). As a result of climate change, much of coastal Guinea is at risk of sea level rise, particularly in low-lying areas including Ile Kaback and the port site. A review of current and predicted changes indicates that Guinea’s coastal zone is likely to experience the greatest perturbations in precipitation events in comparison with inland areas, however, it is currently unclear how rainfall in the Guinean Coast will evolve. Such impacts are predicted to further exacerbate current issues such as coastal erosion, saline intrusion (ie salt water penetrating further inland) and changes to river catchments, including alteration of sediment supply in coastal areas (which may affect the coastline position). 7.3.4 Physical Oceanography 7.3.4.1 Bathymetry The continental shelf off Guinea is the largest on the African continent, measuring up to 120 - 130 km wide in places, with a shallow gradient of typically less than 0.1%. Shelf waters are shallow with depths of typically less than 20 m. Prominent features include various submarine canyons where the 20 m depth contour extend shoreward. Bathymetry near the port location is presented in Figure 7.1. 7.3.4.2 Waves The port study area experiences persistent swell wave conditions that vary seasonally. The prevailing wave direction in the region is from the south and southwest in all seasons, although the wave height from this sector varies seasonally. The largest and most energetic waves approach from the south and southwest in spring and summer. In winter wave direction is more varied and waves are generally smaller (2). Ocean waves often break on the coastal shelf and their energy is largely dissipated by the time they reach the nearshore environment. Waves in the nearshore environment are primarily generated by winds rather than swell. The dominant winds are the Harmattan (3) and monsoon winds, which generate weak surface waves and variable local winds. In the dry season, Harmattan winds from the east are dominant, whereas monsoon winds from the southwest occur during the wet season (May to October but peaks in July and August). Localised storms or squalls may also generate short term increases in wave height associated with localised changes in wind speed. In summary, waves in the port study area are dominated by waves from the south and southwest in all seasons. However, wave height varies with season and waves in winter are generally smaller and have a wider range of approach directions compared to waves in summer. 7.3.4.3 Currents The Guinea Current stretches along Africa’s Atlantic coast from Guinea-Bissau to Angola (4). It flows east at approximately 3°N along the western coast of Africa and can reach velocities of near 1 m/s in the Gulf of Guinea near 5°W (5). The current consists of water from both the Equatorial Counter Current and the Canary Current. The seasonal instability of these two currents can affect the seasonal variability of the Guinea Current. The Guinea Current, like other eastern ocean boundary currents, is characterised by areas of upwelling and increased biological productivity.

(1) Christensen, J.H., B. Hewitson, A. Busuioc, A. Chen, X. Gao, I. Held, R. Jones, R.K. Kolli, W. T. Kwon, R. Laprise, V. Magaña Rueda, L. Mearns, C.G. Menéndez, J. Räisänen, A. Rinke, A. Sarr and P. Whetton (2007). Regional Climate Projections. In: Climate Change 2007: The Physical Science Basis. Cambridge University Press. (2) AECOM (2011). Wave, Hydrodynamics & Siltation Modelling Document Internal Project Engineering Studies. (3) A hot, dry trade wind that blows from the northeast or east in the western Sahara and is strongest in late autumn and winter (late November to mid-March). (4) US Aid (2007). Guinea Biodiversity and Tropical Forests 118/119 Assessment. Prepared by the Biodiversity Analysis and Technical Support Team. (5) Joanna Gyory, Barbie Bischof, Arthur J. Mariano, Edward H. Ryan. "The Guinea Current." Ocean Surface Currents (2005). Available at http://oceancurrents.rsmas.miami.edu/atlantic/guinea.html.


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The oceanographic currents of the Guinea region, and West Africa in general, are influenced by high air temperatures, high humidity, heavy rainfall and distinct dry seasons and wet seasons (1). In general, during the dry season (November - April) the Canary Current and upwelling events bring cold saline water in a south southwest trend. Currents in the littoral zone are controlled by tides, with tides propagating up to 35 km upstream in some rivers due to low riverine flows. In contrast, during the rainy season (May - October) warm, saline tropical surface currents are driven in a northerly direction by monsoon winds. Input of freshwater becomes much more important in influencing currents in the littoral zone, as precipitation can be up to 4 000 mm over some months causing periods of high river flow. Local currents in the region are driven by the tides. Current speed and direction will be variable and may be faster where tidal flows are restricted between sandbanks, which cause localised areas of scour and deposition along tidal river channels. Currents may also propagate large distances along river channels due to low freshwater input. During the dry season brackish waters may be found throughout the Morebaya River system. 7.3.4.4 Tides Tides in the region are semi-diurnal and the spring tidal range is typically higher than 3.3 m. The tidal range is primarily driven by offshore bathymetry. In coastal areas the tidal current typically flows in a north northeast direction during the flood tide and south southwest during the ebb. Tidal current velocity can reach 1.2 m/s during the spring tide and 0.7 m/s during the neap tide. 7.3.5 Coastline Characterisation The Morebaya estuary is fringed by a narrow band of mangrove behind which lie extensive bogoni rice fields. The northern bank at the river mouth on Ile Kakossa has extensive intertidal mudflats backed by a relatively wide band of mangrove, sandy beach and bogoni fields. The southern bank of the estuary mouth on Ile Kaback is also characterised by intertidal mudflats, mangrove and sandy beaches. The sandy beach on the southern bank is approximately 20 - 30 m wide and over 3 km long with well sorted (uniform) fine sand. Figure 7.3 shows examples of the sandy beaches south of Sangbon on Ile Kaback. Sand bars extend offshore in a southwesterly direction from the southern bank of the Morebaya River mouth. Outcropping of bedrock is rare in the area but two rock outcrops occur at the proposed port site. Figure 7.3 Examples of Sandy Beaches on Ile Kaback

Aerial photography from 1967 - 2007 indicates that the coastline in the study area is relatively dynamic, with areas of accretion and erosion that have altered the shape and position of the coastline over the last few decades. The banks of the Morebaya River, however, are relatively stable. The development of sand spits in the region indicates that the net direction of littoral drift is from south to north in association with the incident wave direction. Long-term changes to beach profiles in the port study area are predominantly

(1) Social and Environmental Baseline Studies (2008).


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caused by variations in the longshore sediment transport along the beaches. Longshore sediment transport rates are largely determined by the nearshore wave heights and directions with transport mostly generated by waves from oblique angles. Sediment transport rates increase with increasing angles of wave incidence and wave height. Figure 7.4 shows that the greatest coastal erosion occurs along Ile Kaback, to the south of the port site. Figure 7.4 Coastline Regression 1967-2007

Source: Baird (2008) (1)

Sandbanks in the estuary, including the sand bars on the southern margin of the estuary mouth, are highly dynamic and migrate actively due to variations in tidal and river flows. The size and locations of the sandbanks varies but their orientation remains consistent with the dominant tidal flows at the mouth of the Morebaya River. The sandbanks consist of coarse sands with surface ripples that are indicative of the locally high energy environment at the river mouth. The Morebaya River has a small catchment of approximately 450 km2 that mainly includes the marshy lowlands within 25 km of the coast. Due to the low gradients within the catchment and the wetland nature of the terrain, the sediment load within the Morebaya River is expected to be mainly mud and clay rather than coarse sand or gravel. Water quality data for the Morebaya River show high suspended sediment concentrations consistent with mud or clay-laden water. The port study area is low lying and therefore future coastal erosion rates may be influenced by sea level rise associated with global climate change. Sea level rise will be especially significant for low lying areas such as Ile Kaback. The risk of erosion is exacerbated by the encroachment of humans into the mangrove areas through the creation of bogoni. Mangroves assist with shoreline stability through the capture of sediments and dissipation of wave energy. Most of the sediments settle within the roots of the mangrove during slack water, with the ebbing water containing little sediment. This results in net sediment accretion in mangrove areas and the wider the mangrove habitat, the more sediment is captured. In areas without mangroves, the wave action on shores may gradually erode the shoreline if there is limited replenishment of sediments. Local communities on Ile Kaback have installed rudimentary structures along the coastline to provide some protection to the coast, such as the brushwood breakwaters shown in Figure 7.5. However, natural features such as mangroves remain the primary form of coastal defence in the region and are of high value to local

(1) Social and Environmental Baseline Studies (2008).


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communities to protect their land from coastal flooding. The low lying nature of the region means that any inundation is likely to cover a large area. Figure 7.5 Brushwood Breakwaters on Ile Kaback

7.3.6 Sediment Characteristics and Quality Surface seabed sediments in the Port site are dominated by very fine to fine sands and muds. Coarser sediment (coarse sand to very fine gravel) is generally found in the estuaries of rivers, including the Morebaya, where water flows are stronger and fine material is actively transported away. A band of very fine sand to mud occurs between the 5 and 10 m isobaths, originating in front of the Forécariah River and extending north and eastward toward Ile Kaback. North of Ile Kaback, the fine sand transitions into mud up to the channel of the Morebaya River, where much coarser material is observed. The variety of the sediment fractions across the region is indicative of a dynamic environment with active transport and erosional processes (1). Figure 7.6 presents the broad distribution of sediments types across the region, although samples within the classifications vary. Figure 7.7 shows textural groups and photographs of individual sediment samples within the Morebaya River and estuary. Density currents (2) are expected to occur within the Morebaya estuary, with saline mud laden water intruding into the rivers during the wet season. Fluid mud may also occur throughout the area, even outside the wet season (3). Fluid muds are a common characteristic of estuarine environments that have high levels of sediment supply. They consist of fine materials that are unable to settle completely out of solution due to influence by waves and tidal currents, typically forming a layer of high suspended sediment near the seabed.

(1) Social and Environmental Baseline Studies (2012). (2) Density currents typically consist of water, with a different density to the surrounding water eg muddy saline water that flows along the seabed. (3) Aecom (2012). Memorandum - Geomorphological Background Information for Simandou. Internal Project Engineering Studies.


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Figure 7.6 Seabed Sediment Characteristics

Source: Social and Environnemental Baseline Studies (2012).

Early indications are that baseline sediment deposition is prevented in the wet season by high river flows but in the dry season muddy sediments accumulate on banks and in the main river channels (1). Tidal currents sweeping in and out of the river mouth are likely to measure approximately 1 to 1.5 m/s on spring tides, which may be sufficient to keep some of the natural channels clear of fine muds even in the dry season. These tidal currents cause high turbidity of the water in the river (see Section 7.3.7). The tidal currents also transport sandy sediments brought down as wet season bed load and redistribute these fractions to sandbanks on either side of the river mouth. The primary sediment interaction between the river and the nearshore area is an exchange of fine suspended sediments from the river into the coastal water bodies and vice-versa. The turbidity maximum zone (where turbidity levels are highest) occurs in the lower Morebaya estuary mouth oscillating seasonally into the river during the dry season and out towards the coastal banks of the estuary mouth during the wet season. The contribution of sediments from the Morebaya River to the nearshore mudflats is believed to be low relative to the redistribution of nearshore sediments under tidal and ocean currents and most significantly wave induced mixing and resuspension. Total organic carbon (TOC) is used as a proxy for organic matter content and has been found in concentrations of up to 2% in the coastal area near the Morebaya River (2). The Morebaya River itself has TOC concentrations of up to 3% and TOC concentrations generally decrease in nearshore sediments to the south of the Morebaya estuary. Metal concentrations in sediments are generally higher in areas of fine sediment since fine sediment particles preferentially adsorb contaminants. The baseline data collected for the Project indicates that the Morebaya River sediments have lower metal concentrations than other rivers in the region and there is no discernible pattern in the spatial distribution of metals in the marine environment (3). Sediment metal concentrations from the study area have been compared with the Canadian Environmental Quality Guidelines developed by the Canadian Council of Ministers of the Environment (CCME). These Canadian guidelines are commonly used in sediment characterisation studies worldwide. The threshold effect level (TEL) represents the concentration below which adverse biological effects are expected to occur rarely and the probable effect level (PEL) defines the level above which adverse effects are expected to occur frequently.

(1) Aecom (2012). Memorandum - Geomorphological Background Information for Simandou. Internal Project Engineering Studies. (2) Social and Environnemental Baseline Studies (2012). (3) Social and Environnemental Baseline Studies (2012).


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Figure 7.7 Sediment Characteristics of Samples from within the Morebaya River and Estuary

Station 3A05 – sandy mud Station 4A01 – muddy sand


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Sediment quality in the region is generally good. Table 7.5 presents a summary of the results of sediment sampling conducted in the region during 2011. Project data and the CCME guidelines are reported in total concentrations. The maximum observed concentrations of copper, mercury, lead and zinc in sediments from the Project area were all below the TEL. The maximum observed concentrations of cadmium were above the TEL but below the PEL. The maximum observed concentrations of arsenic and chromium were above the PEL; however, the median concentrations were much lower and in the case of chromium were below the TEL. This indicates that the majority of sediment samples from the Project area contained relatively low arsenic and chromium concentrations and the maximum concentrations obtained are not typical of the area. When compared with results from other studies in Africa (Mediterranean, Guinean Gulf and India Ocean), arsenic is the only metal with higher concentrations (1). The source of potential arsenic contamination is unknown; however, arsenic was used during the twentieth century as an insecticide on fruit trees and in other agricultural practices in the study area which may have contributed to the presence of arsenic in sediments. Other than this potential source there are no significant anthropogenic sources and those detected are likely to represent natural baseline mineralogy. OSPAR levels represent the current concentration ranges used by signatories of the OSPAR Convention during the assessment of dredged material for dumping at sea. All median trace metal concentrations are either within or below the OSPAR target range (Table 7.5) indicating generally good sediment quality that can be disposed of at sea. The sediment characterisation undertaken for the Project entailed sample collection of surface sediments using a grab sampler. Deeper sediments are also expected to be of natural quality and similar in nature. Table 7.5 Total Sediment Metal Concentrations in the Port Area Relative to International Guidelines

- Canadian Council of Ministers of the Environment (CCME) and OSPAR

Trace metals Concentrations CCME OSPAR

Units Minimum Median Maximum TEL PEL Target Limit

Arsenic mg/kg 2 10 81 7.24 41.6 20 - 80 29 - 1 000

Cadmium mg/kg 0.2 0.2 3 0.7 4.20 0.4 - 2.5 2.4 - 10

Chromium mg/kg 2 40 230 52.3 160 40 - 300 120 - 5 000

Copper mg/kg 1 3 13 18.7 108 20 - 150 60 - 1 500

Mercury mg/kg 0.05 0.05 0.06 0.13 0.7 0.3 - 0.6 0.8 - 5

Nickel mg/kg 1 9 21 15.9 42.8 20 - 130 45 - 1 500

Lead mg/kg 5 5 16 30.20 112 50 - 120 110 - 1 500

Zinc mg/kg 7 23 44 124 271 130 - 700 365 - 10 000

Source: Social and Environnemental Baseline Studies (2012). Note: TEL = Threshold Effect Level and PEL = Probable Effect Level

In summary, the results of the sediment quality testing do not indicate significant contamination of sediments in the Project area. Some determinants are slightly elevated in some areas but as the median concentrations are within the OSPAR target range the sediments are deemed acceptable for disposal at sea. 7.3.7 Water Quality Water quality varies between the dry season and the wet season (2). The dry season is characterised by higher water temperature, salinity and suspended solids and lower dissolved oxygen and dissolved organic carbon. Rivers are characterised by a salinity of 30 to 35 parts per thousand (ppt) during the dry season, which is full seawater salinity, and 5 to 18 ppt during the wet season. The lower salinity in the wet season is due to dilution by increased rainfall and surface runoff. Salinity is higher nearer the river mouths compared to upstream and is highest during high tide when seawater moves into the estuary.

(1) Social and Environnemental Baseline Studies (2012). (2) Social and Environnemental Baseline Studies (2012).


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Water quality data for the Morebaya River sampled during the wet season in 2011 are presented in Table 7.6. Dissolved oxygen concentrations varied between 4.11 and 5.25 mg/l, which correspond to an oxygen saturation of between approximately 59% and 80%. Oxygen concentrations in the Morebaya River in the wet season were higher at high tide than low tide and there was no clear pattern between oxygen concentration and depth. No anoxic waters were detected in the Morebaya River. Surface oxygen concentrations in other nearby rivers have been recorded as lower in the dry season than in the wet season. Relatively high levels of aluminium and iron were found in the Morebaya River water samples, as CCME guidelines for the protection of aquatic life were exceeded for these metals (Table 7.6). However, toxic metals, that may affect marine life, are all below the CCME and threshold levels for protection of saltwater life developed under the EU Water Framework Directive priority substances programme (1), indicating overall good water quality. The levels reported in Table 7.6 are total concentrations and for unfiltered samples, and as such are directly comparable to the CCME guidelines. EQS priority substances thresholds are for dissolved and filtered samples. Dissolved concentrations are less than total concentrations for the same sample, so where total sample concentration results are compliant with a dissolved threshold this provides a conservative analysis as the dissolved concentration in the sample will always be equal or lower than the total. High levels of aluminium and iron are typical of the laterite soils found in the region and are likely to be natural baseline levels. In the wider region, high concentrations were also reported for aluminium, copper, iron, lead, zinc and molybdenum. Concentrations of nutrients such as nitrogen and phosphorus were measured at levels within the typical range for coastal waters. Accurate measurement of suspended sediment is difficult to obtain in the field and usually requires continuous monitoring over a period of time (2) combined with laboratory calibrated sampling and analysis. However, studies for the Project have shown that total suspended sediment (TSS) concentrations in the Morebaya River and offshore area are variable. These studies seem to indicate that there are no ‘typical’ TSS concentrations for these coastal waters and each coastal environment will have specific sediment and / or hydrologic characteristics. Naturally high TSS concentrations are apparent for Guinean coastal waters. Studies for the Project have measured TSS concentrations in the offshore region in the dry and wet seasons of 2008 and the dry season in 2011, and in the Morebaya River in the wet season of 2011 and dry season of 2012. In the dry season of 2008 offshore TSS concentrations were recorded as 7.8 mg/l at the water surface (no bottom measurement), while in the wet season TSS concentrations were 9.3 and 46.3 mg/l at the surface and bottom respectively. Concentrations in the dry season of 2011 were higher with peak exceeding 400 mg/l. The full range of TSS for the dry season of 2011 is presented in Figure 7.8. Note however that the results indicate the presence of potentially confounding effects of biological fouling, which is where marine microbiologic films grow on the sensor windows during long term deployment of marine instruments. The film growth causes anomalous readings which are evident in Figure 7.8 after approximately 3-4 weeks of deployment as shown by visible or higher and more erratic turbidity readings. Studies for the Project have shown that within the Morebaya River during the wet season Total Suspended Solids (TSS) were higher at low water than high water. Low water levels ranged between 150 and 310 mg/l (see Table 7.6). At high water TSS levels in the Morebaya ranged between 130 and 160 mg/l. TSS concentrations were measured in the Morebaya River in dry season of 2012 and were found to be in about the same range as in previous year (12.64 to 328.19 mg/l depending on tidal state and surface or bottom water). TSS in the Morebaya River in 2012 was higher during spring tide than neap tide. TSS values reached 328 and 258 mg/l at stations WQ07 (approximately 1 km upstream from the main port) and WQ12 (in the mouth of the estuary approximately 6.5 km downstream from the main port) during spring low tide (near the bottom). However, water sampling during the sedimentary dynamics study conducted in 2011 and 2012, showed that TSS concentration can reach up to 890 mg/l during dry season in the Morebaya River.

(1) Directive on Environmental Quality Standards (Directive 2008/105/EC) (EQSD) (2008). Available at http://ec.europa.eu/environment/water/water-dangersub/pri_substances.htm#dir_prior (2) Social and Environnemental Baseline Studies (2012).


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In summary, the baseline water quality exhibits some parameter concentrations that are higher than guidelines, likely due to the suspended sediment content, but given that no sources of anthropogenic pollutants are present these levels are likely to be natural baseline. This should be borne in mind when monitoring is being conducted and results interpreted. Table 7.6 Wet Season Water Quality Data

Parameters Units CCME EQS

Morebaya

Up river* Down river*

Low tide High tide Low tide High tide

Physical

Temperature °C 6.5–9.0 29.8 29.7 30.3 29.8

Salinity ppt 11.1 12.4 14.5 18.1

Suspended sediments mg/l 150 130 310 160

Dissolved oxygen mg/l 4.22 4.87 4.29 5.08

pH - 6.92 6.86 7.16 7.54

Nutrients

Dissolved organic carbon mg/l 13 1.7 1.4 1.7 1.5

Nitrate and Nitrite mg/l <2 <2 <4 <4

Phosphorus mg/l 0.04 0.07 0.14 0.05

Metals

Aluminium (Al) μg/l 100 1 700 1 200 2 200 1 400

Arsenic (As) μg/l 5 25 2.2 2.3 3.7 1.9

Cadmium (Cd) μg/l 0.65 <0.20 <0.20 <0.20 <0.20

Chromium (Cr) μg/l 15 6.15 5.8 10 5

Copper (Cu) μg/l 45.7 5 2.35 4.9 1.9 0.75

Iron (Fe) μg/l 300 4 000 4 200 7 200 2 600

Lead (Pb) μg/l 262 25 4.1 1.9 2.9 0.96

Zinc (Zn) μg/l 30 40 11.5 14 19 <5.0

Molybdenum (Mo) μg/l 73 2.95 2.4 3.6 8

Mercury (Mg) μg/l 0.016 <0.1 <0.1 <0.1 <0.1

Notes: All measurements were taken at mid depth. Reported levels are total and for unfiltered samples. ‘<’ denotes a result reported at or below the limit of detection of the analytical procedure. * Up river = approx. 9 km up river from the port site; down river = approx. 2.5 km down river from the main port site. Source: Social and Environnemental Baseline Studies (2012).


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Figure 7.8 Water Quality Offshore Ile Matakang

Note: PSU is equivalent to ppt


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7.4 Assessment of Impacts 7.4.1 Overview This section presents the results of the assessment of potential impacts from port construction and operation on the main features of the marine and littoral physical environment as described in Section 7.3. The assessment of impacts has addressed the types of impact introduced in Section 7.1, which are as follows: impacts to the geomorphological features; impacts to water quality; and impacts to sediment quality. Design measures that will be implemented to reduce potential impacts or maximise positive impacts are discussed within this section where relevant. Additional mitigation and residual impacts are discussed in Section 7.5: Mitigation Measures and Residual Impacts. Impacts to marine fauna and flora are considered in Chapter 13: Marine and Littoral Biodiversity and impacts to land use and access are considered in Chapter 5: Geology, Soils and Mineral Waste and Chapter 20: Land Use and Livelihoods. This assessment also considers seabed and coastal changes due to the MOF as part of the port in order to assess potential cumulative impacts that result from the port project and other on-going projects in the region. The MOF is part of advance works for the Simandou Project and a separate SEIA has been produced for it (1). 7.4.2 Impacts to Geomorphological Features 7.4.2.1 Geomorphological Impacts during Port Construction Impacts to geomorphological features in the vicinity of the port during construction may occur due to the presence of the port infrastructure along the river bank and / or from dredging and dredge spoil disposal affecting the local hydrodynamic and sedimentary regimes. The construction of the port requires the installation of infrastructure at a location approximately 5 km up the Morebaya River along the east river bank. The marine port infrastructure will consist of a 1 200 m export wharf, a transport platform and approach jetty (see Figure 7.9 for two potential wharf options). Port construction will modify the river bank and involve the installation of wharf support structures (piles) into the river bed. An approach channel, berthing pockets and turning basin will be dredged to provide vessel access to the port (and MOF) during port construction and operation. Dredging depths are in the order of 20 m below chart datum and full details are presented in Chapter 2: Project Description. Dredging of the turning basin and berths will be within the river and the access channel will be dredged from the river port location out to approximately 30 km offshore. Dredged material will be disposed at approved offshore disposal sites which will be located approximately 20 km off the coast of Ile Kaback in water depths of around 20m (a potential disposal site is shown in Figure 7.1). Construction of the port will directly alter the shape of the river bank within the port footprint (including removal of the mangrove shoreline alongside the wharf) and change the bathymetry within the access channel, berths and turning basin. These changes may also affect the local hydrodynamics and sedimentary regime causing changes to the coastline outside the port footprint. The port will alter the bed of the Morebaya River and coast and in addition to direct removal of material by dredging may cause changes in the local waves and current flows. These may in turn change the river and / or seabed and coastal morphology (including beaches) through changes in rates of sediment transport, deposition and erosion. Changes in the hydrodynamic and morphodynamic regimes will persist beyond the construction stage and throughout the operational stage. As such impacts relevant to both the construction and operational stages of the port are discussed in this section, including maintenance dredging.

(1) Simandou Project Social and Environmental Impact Assessment (SEIA) Marine Offloading Facility. November 2011.

Fandiema

Touguiyiré

Sourima

Moufoufanye

Client: Taille: Titre:A4 Figure 7.9

Quai d'exportation du port /Port Export Wharf

Projection: WGS 1984 UTM Zone

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Légende:

Vérifié par: AM

Approuvé par: KR

Projet: 0131299

Echelle: Comme Barre d’échelle

Date: 19/09/2012

Dessiné par: WB

Quai d'exportation déplacé / Relocated Export WharfInfrastructures portuaires / Port infrastructureZone de dragage / Dredging AreaTracé indicatif de la voie ferrée / Indicative Rail Alignment

Agglomération / SettlementChef lieu de préfecture / Prefecture Chief TownChef lieu de sous-préfecture / Sub-Prefecture Chief TownVillage / VillageHameau / Hamlet

Route secondaire / Secondary roadRoute tertiaire / Tertiary routeRoute quaternaire / Quaternary route

G u i n e aG u i n e a

Quai d'exportation /Export Wharf

Rampe LST / LST Ramp

Navire de minerai de fer /Iron Ore Vessel

Mouillage /Berthing Pocket

Chargeur de navire /Ship Loader

Jetée / Jetty

Port de remorqueur /Tug Harbour

MOF

Chargeur de navire /Ship Loader

Navire de minerai de fer /Iron Ore Vessel

Cercle de giration /Turning Circle

Cercle de giration /Turning Circle

Chenal de dragage /Dredging Channel

Quai d'exportation déplacé /Relocated Export Wharf


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The presence of the export wharf, approach jetty, MOF and berths will alter currents locally and affect the morphodynamic regime. This is likely to result in sedimentation and erosion surrounding the in-water structures such as piles. The design of the port components, in particular the stilted design of the export wharf, will limit the footprint in the river as far as possible. The stilted design allows water and sediments to flow underneath and reduces potential changes in the hydrodynamic and morphodynamic regime compared to a solid structure. The exact nature of the changes in the morphodynamic regime is unknown; there is likely to be scouring at the base of the piles and pockets of sediment will accumulate up-current from the base of the piles. Project vessels, especially large ore vessels and associated tugs, will also generate bow and propeller wash that may increase erosion of the river bed and / or the river banks. Changes in bathymetry caused by dredging and dredge disposal will potentially affect the seabed, sandbanks and beaches by altering the hydrodynamic regime and sediment supply to the coast. Water depths within the approach channel will be significantly deeper than the surrounding seabed and will extend approximately 30 km offshore, although with a progressively reduced dredge (channel) depth relative to the surrounding seabed in the deeper areas. Chapter 2: Project Description illustrates the dredging locations and depths. In total, an estimated 140 million (M) m3 of sediment will be dredged from the approach channel during construction and all of this sediment will be disposed at the offshore disposal site. Sediment disposal is predicted to reduce the water depths across the disposal site by approximately 5 m to 15 m water depth. The dredged area will cover approximately 1490 ha. The design of the channel seeks to minimise the dredging (both in volume and area) as far as possible. Coastlines are sensitive to changes in patterns of water flow and altered wave heights and direction. Initial modelling conducted for the Project indicates that the presence of the port access channel may cause changes in wave heights to the north and south of the channel, thus displaying a blockage effect caused by the depth of water in the access channel. This variation of wave heights around the channel is mainly due to wave refraction in the relatively shallow water adjacent to the access channel. As a result the beaches to the north and south of the dredged access channel are at risk of altered wave action, which may lead to either erosion or accretion of beach sediments. The proposed access channel consists of three sections: a deep offshore section with an orientation of 275ºN leading into a middle section oriented at 240ºN and into the innermost section which is oriented at 260ºN. Modelling conducted for the Project indicates the deep section is not expected to significantly affect the nearshore wave climate, because the predominant waves are approaching at a relatively large angle to the channel and refraction of waves will occur only during a small percentage of the time. In the middle section, some refraction is expected of the dominant waves resulting in zones of alternating wave heights, and greater influence may occur from the inner section. The exact impact of refraction such as wave shadow, or increase in wave height is highly sensitive to channel geometry, alignment and angle of wave incidence and so may vary depending on the final detailed channel design and also with varying wave conditions. Figure 7.10 shows potential areas of wave refraction and predicted changes to the coast from waves within each segment of the access channel. Wave propagation computations indicate that for the dominant wave conditions an area higher wave heights along particularly the northern part of the Kaback will result in increased net transport of sediment north with a potential erosive impact. North of the Morebaya the Kakossa shoreline may also experience an increase in erosion of a similar magnitude and certainty. Modelling predictions will be subject to refinement on the basis of additional baseline data and long term coastline monitoring. Erosion may also contribute to natural formation of a beach escarpment and changes in the profile of beaches.


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Figure 7.10 Areas of Potential Wave Refraction and Changes to the Coast from Waves

The river banks may be affected by a decrease in flow velocity along the river axis of the dredged area and accelerations of flow as it leaves the dredged areas, which can lead to erosion of the river banks adjacent to the channel. In addition the channel is expected to cause drawdown of sediment in the Morebaya River estuary as the channel seeks to fill in, which may affect the coastline including the beaches, mudflats and mangroves. Wave-induced currents transport mud and sand along the coast in the breaker zone (approximately above 7 m CD). Currently a shallow channel is present in the Morebaya River that is in dynamic equilibrium with the surrounding seabed. However, the access channel will disturb this equilibrium by trapping sediment transported in the breaker zone, which will change the sediment balance by removing sediment from the active coastal system. As well as longshore sand transport, river bedload sediment (sand-silt) and transported mud will also contribute to infilling of the channel. In dredged areas away from the river mouth in open waters, sedimentation will be predominantly from transported mud. Though this will initially mainly affect the muddy foreshore, some adverse effect on the sandy beaches is also expected. Sand trapped in the channel is estimated to lead to an overall lowering of the area around the channel by a few mm/yr to cm/yr. In the long-term, this subsidence effect may adversely affect the beaches over several kilometres at both sides of the channel. Under certain conditions the access channel may trap sand transported in a cross-shore direction from the beaches in the estuary mouth into the channel where it will


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remain trapped. Moreover, due to some lowering of the foreshore, wave action on the beaches may increase. At all times in the dredged channel, close to the seabed there will be a large increase in suspended mud concentration compared to the surface or water column average. The water column will be transported to and fro along the shore by the tidal currents and this heavily laden bottom layer will be dragged across the dredged areas resulting in sediment trapping in the dredged areas. Sedimentation of the dredged areas will continue over time and into the operation phase of the project, however, the approach channel will be maintained at depth through maintenance dredging. Impacts during port operation are discussed in detail below. Maintenance dredging will be a significant on-going project activity. The exact requirements will be determined through additional modelling and long term monitoring, but are predicted to be in the order of 20 to 50 million m3 per year and will initially utilise the same dredging disposal sites as the capital dredging. Additional disposal sites may be required at a future date in the Project as the proposed dredging disposal site is filled. The change in sediment dynamics may affect the geomorphological features in the estuary, such as the sand bars to the south of the estuary, sand flats further out in the estuary alongside the approach channel and the mudflats along the southern shore of Ile Kakossa. A number of sandbanks and a proportion of mudflat will be lost as these lie in the dredge footprint. Sandy material trapped in the dredged areas will be removed by dredging and taken out of the local sediment budget at the river mouth (1). This will lead to a sediment deficit for maintenance of some of the sandy features of the estuary mouth and some of the sandbanks on either side of the channel may be reduced in height and extent. These mobile features will also migrate from their present location depending on river floods and sediment loads. The deficit of sand trapped in the dredged areas and the changed hydrodynamics may exacerbate sandbank migration and also lead to increased intrusion or drawdown of these features into the channel. The impacts of the mud removal will be less profound since replacement mud is more readily available from the nearshore shelf of Guinea (not only from the river, which makes a small contribution to the mud accumulations in the channel on an annual basis). The disposal of dredged materials will result in localised changes to bathymetry at the disposal site (see Figure 7.1 for disposal site location). The dredge disposal site has been chosen to avoid sensitive receptors, such as areas close to the coastline, as well as meet other relevant criteria such as size and distance from the dredge locations. The semi-confined disposal site is located offshore of the Ile Kaback peninsula at around the -20 m CD contour at approximately 20 km offshore. The site lies between two sites investigated in the dredging pre-feasibility study by Baird (2008) (2). Modelling conducted for the shallower of the sites (east of the current site) found that generally there would be a slow migration of the sediment to the south and west. It is expected that some wave refraction will occur at the disposal site but that the effect near the shoreline will be very small. Geomorphological features that are reduced in size due to the changes to the morphodynamic regime (eg sand bars at the river mouth), and general deepening of the channel may allow the propagation of larger waves and storm surges further up the estuary. The approach channel may also act as a conduit for larger waves entering the estuary. The intrusion of larger waves further up the estuary may increase coastal erosion rates and the vulnerability of inland areas to coastal flooding. Storm surges may lead to flooding of the low lying land of Ile Kaback and the port site if the dykes around the rice fields are not strong enough or high enough (see Chapter 6: Water Environment). Furthermore, coastal erosion is likely to be exacerbated by the removal of mangroves from the river bank (a form of natural coastal defence) both for the Project and by local communities, by climate change (ie future sea level rise and changes in precipitation and frequency and / or severity of storm events) and ship wash. The coastal shelf seabed in the study area is considered to have low value as it is not protected, common and relatively homogeneous with no real conservation significance. The river and estuary bed in the study area is considered to be medium value as it is locally rare and is of value to some species of conservation interest and communities. Impacts to the coastal shelf seabed, river and estuary will result from depth changes due to dredging and dredged sediment disposal and alterations in currents as a result of the

(1) Aecom (2012). Preliminary Report on Supplementary 3D Wave, Hydrodynamics and Siltation Modelling. Internal Project Engineering Studies. (2)Social and Environnemental Baseline Studies (2008).


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dredging and structures, as described above. The dynamic nature of the marine and littoral system means that impacts to the seabed and river bed are likely to be experienced throughout the Morebaya estuary. Impacts to the wider seabed are likely to occur only locally to the port, dredged areas and dredge disposal site and any changes are expected to be relatively small scale, especially in comparison with natural changes and sedimentation from fluvial inputs. However, given that maintenance dredging will be carried out the impacts will persist over the lifetime of the Project. Impacts to the seabed and river bed are considered to be of medium magnitude as a significant area will be affected but the long term viability and function of the seabed in the region (ie its use by biodiversity and communities) is not threatened. The impact is therefore of minor significance for the coastal shelf seabed and moderate significance for the river and estuary bed. The sandy beaches at the mouth of the Morebaya River are considered to have medium value as they are locally rare (although alternatives exist in the wider geographic region). The beaches are a locally important feature in terms of coastal defence, fishing and fish landing sites. Impacts to sandy beaches may occur through changes in the wave regime and the drawdown of sediment from dredging of the access channel. Taking a conservative view to the assessment the magnitude of impact is considered large as the entire feature could be affected and the function of the feature may be reduced so that they no longer provide coastal defence or suitable areas for fishing. The impact is therefore of major significance. Impacts to social receptors are discussed in Chapter 20: Land Use and Livelihoods. Mangrove shorelines are considered to be of medium value as they are locally very important, play a role in coastal defence and support species of conservation interest and communities. The impacts associated with the placement of Project components and removal of the mangrove alongside the proposed export wharf will be largely site specific. Changes to the hydrodynamics may have consequences for the river bank at the port site and further downstream, which may affect the mangroves. In addition the access channel may alter the wave climate and sediment supply, which may affect mangroves on the shores of Ile Kakossa. Impacts to mangroves along the coast may occur due to drawdown of the foreshore and changes in wave regime, while other areas of mangroves may be cleared. A loss of approximately 8 ha of mangrove has been assessed as part of the MOF SEIA. In addition there is a further 100 ha of mangrove within the port boundary, which may be lost due to construction and access requirements, although it is unlikely the full 100 ha will be cleared. The mangrove lost will be near the MOF site, alongside the proposed export wharf, along the conveyor corridor and near the rail loop. Taking a conservative view to the assessment the magnitude of impact is considered to be large as a significant proportion of the feature may be affected and the function will be reduced in the long term. The impact is therefore of major significance. Sandbanks and mudflats are considered to be of medium value as they play a role in coastal defence and have some value to both species of conservation interest and communities. Impacts to sandbanks and mudflats may occur due to direct removal through dredging at the river mouth or through drawdown of sediment due to the presence of the dredge channel and removal of sandy sediments from the system, although the exact impact is unknown. Given the uncertainties and taking a conservative view to the assessment the magnitude of impact is considered large as the entire feature could be affected and the function of the feature may be reduced so that they no longer provide coastal defence or suitable areas for fauna and flora. The impact is therefore of major significance. It is acknowledged that the coastal flooding and erosion impacts associated with sediment drawdown are likely to be exacerbated by global climate change. Primarily this will be through future sea level rise, although changes in precipitation and the frequency and / or severity of storm events and surges will also contribute. It is likely that global climate change will put increasing pressure on the geomorphological features in the region, including contributing to a reduction of their size. 7.4.2.2 Geomorphological Impacts during Port Operations Impacts to geomorphological features in the vicinity of the port may occur during port operations due to the presence of the port infrastructure along the river bank and / or from maintenance dredging and dredge spoil disposal affecting the local hydrodynamic and sedimentary regimes. Once constructed the port and approach channels will continue to impact the local environment within the Morebaya River and in nearshore and offshore areas. The only difference between potential impacts to


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geomorphology from port operations compared to port construction is that maintenance dredging activities will periodically remove accumulated sediments from the approach channels, turning basin and berths and dispose of the sediment in designated offshore disposal area(s). The annual volume of sediment to be dredged and disposed of during port operations is likely to be less than the capital dredge volumes during port construction but the process of removal will be similar. Any impacts to geomorphology (seabed, sandy beaches sandbanks and mudbanks) will likely continue during port operations as result of maintenance dredging activities maintaining the channel depth and new hydrodynamic regime. Once the port is constructed there will be no on-going direct impact to mangrove habitat during port operations, however, on-going drawdown and erosion may continue to affect mangroves. Impacts to the seabed are likely to occur only locally to the port, in dredged areas and at the dredge disposal site and any changes are expected to be relatively small scale, especially in comparison with natural changes and sedimentation from fluvial and coastal inputs. However, given that maintenance dredging will be carried out the impacts will persist over the lifetime of the Project. Impacts to the seabed are considered to be of medium magnitude as a significant area will be affected but the long term function of the seabed is not threatened. The coastal shelf seabed in the study area is considered to have low value and the river and estuary bed in the study area is considered to have medium value. The impact is therefore of minor significance for the coastal shelf seabed and moderate significance for the river and estuary bed. The sandy beaches at the mouth of the Morebaya River are considered to have medium value as they are locally rare (although alternatives exist in the wider geographic region). They are of value to some species of conservation interest, are a locally important feature in terms of coastal defence and are used by local communities for landing fish. Impacts to sandy beaches may occur during Project operations through changes in the wave regime and the drawdown of sediment from maintenance dredging of the access channel. Taking a conservative view to the assessment the magnitude of impact is considered large as the entire feature could be affected and the function of the feature may be reduced so that they no longer provide coastal defence or suitable areas for wildlife. The impact is therefore of major significance. Mangrove shorelines are considered to be of medium value as they are locally very important, play a role in coastal defence and support species of conservation interest and communities. Changes to the hydrodynamics associated with the presence of the port and approach channel may have consequences for the river bank at the port site and further downstream, which may affect the mangroves. In addition, the access channel may alter the wave climate and sediment supply, which may affect mangroves on the shores of Ile Kaback and Ile Kakossa. Impacts to mangroves along the coast may occur due to drawdown of the foreshore and changes in wave regime. Taking a conservative view to the assessment the magnitude of impact is considered to be large as a significant proportion of the feature may be affected and the function may be reduced in the long term. The impact is therefore of major significance. Sandbanks and mudflats are considered to be of medium value as they play a role in coastal defence and have some value to both species of conservation interest and communities. Impacts to sandbanks and mudflats may occur due to on-going maintenance dredging at the river mouth or through drawdown of sediment due to the presence of the dredge channel and removal of sandy sediments from the system, although the exact impact is unknown. Given the uncertainties and taking a conservative view to the assessment the magnitude of impact is considered large as the entire feature could be affected and the function of the feature may be reduced so that they no longer provide coastal defence or suitable areas for wildlife. The impact is therefore of major significance.


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The direct footprint of dredging and disposal of 140 million m3 of sediment and the physical presence of port structures in the river may, result in minor impacts to the coastal shelf seabed during port construction and port operation and moderate impacts to the river and estuary bed during port construction and port operation. The drawdown of sediment from dredging of the access channel may, without mitigation, result in major impacts to sandy beaches during port construction and port operation. Clearance of shoreline mangroves and changes to the hydrodynamics and sediment regime that may further affect mangroves may, without mitigation, result in major impacts to the mangrove shoreline during port construction and port operation. The drawdown of sediment from dredging of the access channel and direct sediment removal may, without mitigation, result in major impacts to sandbanks and mudflats during port construction and port operation.

7.4.3 Impacts to Water Quality 7.4.3.1 Water Quality Impacts during Port Construction Impacts to marine and littoral water quality during construction may be caused by: sediment plumes from the dredging and disposal of dredged sediment; changes to the bathymetry as a result of dredging; discharges from vessels at sea (including sewage, oils, lubricants, bilge, ballast, wastewater and other

chemicals); discharges from onshore facilities such as sewage plants; site run-off and drainage; and unplanned spillages and pollution events. Impacts to marine fauna and flora are considered in Chapter 13: Marine and Littoral Biodiversity and impacts to non-marine surface and ground water are considered in Chapter 6: Water Environment. The coastal region within the vicinity of the Morebaya River and the Morebaya River itself experiences a range of suspended sediment concentrations depending on season, tidal state and position in the water column. Naturally high suspended sediment concentrations (highs in excess of 400 mg/l offshore (wet season) and 310 mg/l in river (low tide)) are caused by the river outflow of fine sediments and resuspension of fine sediments in the nearshore areas due to wave action and tidal currents (see Figure 7.11). Turbid water oscillates into and out of the Morebaya River under the influence of the daily tidal cycle and the extent of tidal flow in the river is estimated to be tens of kilometres (1). Turbid water transports fine sediments from both the river and the sea but predominantly from the sea into the river due to the incoming tide and density driven bottom currents.

(1) Aecom (2012). Memorandum - Geomorphological Background Information for Simandou. Internal Project Engineering Studies.


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Figure 7.11 Naturally Turbid Waters off the Guinea Coast

Source: Baird, 2008 (1)

During port construction the dredging of seabed and riverbed sediments for the access channels, berths and the turning basin will be undertaken 24 hours a day 7 days a week for 36 months using up to seven dredgers. Dredging is likely to be undertaken using a combination of small and large capacity trailer suction hopper dredgers (TSHDs) with an estimated sediment capacity of between 5 000 m3 and 30 000 m3, respectively. Figure 7.1 above shows the dredging areas and dredge disposal location. Sediment plumes may be created during dredging through the action of removing the seabed sediments, as a result of overflow of turbid water from the dredge hopper, from dredger propeller wash (depending on water depth) and to a lesser extent from the drag head on the seabed. Sediment plumes will also be created during disposal of dredged material at the designated offshore disposal sites. Sediment plumes typically influence water quality through increased sediment load and turbidity, remobilisation of contaminants and nutrients contained in the sediments and potential reduction of dissolved oxygen concentrations. In total an estimated 140 million m3 of sediment will be dredged during the port construction period, including 20 million m3 which will be dredged as part of the MOF. This assessment assumes that modern fully equipped dredgers will be utilised for the dredging works that, in accordance with Rio Tinto Guidelines, meet the standards expected of best practice dredging in terms of the methods, processes and technology utilised to minimise environmental impacts. Best practice dredging includes measures to reduce the formation and extent of sediment plumes as far as reasonably practicable, details of which are presented in Section 7.5. Results of dredge plume modelling undertaken for the Project, state that total suspended sediment (TSS) concentrations of 100 mg/l above ambient will occur within a radius of approximately 4 km of two 5 000 m3 capacity dredgers operating in parallel, with TSS concentrations exceeding 10 mg/l above ambient within a radius of 5 - 10 km of the dredgers. For two 30 000 m3 capacity dredgers working in parallel; TSS concentrations of 100 mg/l above ambient will occur within a radius of 5 - 10 km of the dredgers and TSS concentrations exceeding 10 mg/l above ambient will be apparent within a radius of about 10 km of the dredgers. These results (as shown in Figure 7.12) are based on modelling of bottom plumes only and do not account for the influence of river flows in dispersing the plumes. At the offshore disposal site, plumes with TSS concentrations of 100 mg/l above ambient will occur within a radius of one kilometre of the disposal location for the two 5 000 m3 capacity dredgers and within a radius of less than 2 km for the two 30 000 m3 capacity dredgers (ie higher sediment volumes usually means larger sediment plumes); TSS concentrations of 10 mg/l above ambient will occur within a radius of ten kilometres of the disposal location for both small and large capacity dredgers.

(1) Social and Environnemental Baseline Studies (2008).


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TSS concentrations in the study area are variable with season, tidal state and position in the water column. Offshore TSS concentrations have been recorded from 7.8 to over 400 mg/l. Within the Morebaya River sampling results indicate TSS may vary between 12.6 and 890 mg/l. Further details can be found in Section 7.3.7. As such sediment plumes of less than 10 mg/l above background caused by dredging are likely to be noticeable within the Morebaya River and coastal region, especially at times when relatively low TSS is observed; however, given the range of TSS in the region these sediment plumes are likely to be within the natural variation of the region. Changing the sediment source release location due to overflow activity from the surface to the bottom layer does not make a significant difference to the results. Processes contributing to vertical mixing of sediment, which dissipates the initial vertical distribution of sediment, seem to be dominant in the region where dredging and overflow occurs. Likewise, adding a coarser sediment fraction to the model domain does not significantly change the model results in terms of sediment plume extent and concentrations. Figure 7.12 Predicted Dredge and Dredged Sediment Disposal Plume Concentrations and Extents

Above Background (seabed)

Two operating TSHD (5 000 m3) Two operating TSHD (30 000 m3) Note: northing and easting are in kilometres.

Source: Deltares 2012 (1)

Plumes from sediment dredging and offshore sediment disposal can exert an oxygen demand, which affects the concentration of dissolved oxygen within the water column depending on the nutrient and contaminant concentrations within the sediment. Significantly reduced concentrations of dissolved oxygen can affect the health of aquatic species such as fish and invertebrates. Natural dissolved oxygen concentrations in the Project area are generally good (between 4.11 and 5.25 mg/l in the Morebaya River and offshore during the wet season) and nutrient and contaminant concentrations in the sediments are relatively low. Lee et al. (1978) (2) demonstrated that dissolved oxygen concentrations decrease only slightly for only a very short time period (5 - 10 minutes) when large amounts of sediment containing oxygen-demanding materials (1) Deltares (2012) Preliminary Modelling in Support of SEIA. Internal Project Engineering Studies. (2) Lee, G.F. (1978). Evaluation of the Elutriate Test as a Method of Predicting Contaminant Release during Open Water Disposal of Dredged Sediment and Environmental Impact of Open Water Dredged Materials Disposal, Vol. II: Data Report," Technical Report D-78-45, US Army Engineer Waterways Experiment Station, Vicksburg, MS.


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are dumped in an open water disposal site. Lee et al. (1999) (1) conclude that open water dumping of dredged sediment would rarely cause water quality problems due to oxygen demand, as relatively little dumped material mixes with the water column. Where sediments are resuspended or remain in suspension due to water movement there is a greater chance that abiotic oxygen demand associated with sediments would have an impact on water quality. Concentrations of nutrients and metals can be increased within the plume compared to the surrounding water column due to release during dredging disturbance. Initial findings from studies undertaken on sediment plumes seem to indicate that plumes from dredging and sediment disposal within the Project area are not expected to cause large increases in water column contaminant concentrations given the generally good sediment quality in the region (see Section 7.3) and current regional water quality results indicate some already relatively high levels of metals in the water column, which is likely to be associated with suspended sediment and natural for the area. The amount of nutrients that may be released into the water column as a result of dredging is also considered small in relation to those released during natural sediment resuspension and baseline surveys do not indicate excessively high nutrient concentrations in sediments to be dredged. The concentrations of nutrients and metals released into a sediment plume do not necessarily reflect the environmental effect since most of the nutrients and metals will be bound to particles, or readily re-adsorbed, and would be much less biologically available or able to contribute to toxic effects. Sediment disposal will be undertaken regularly throughout the port construction period and the disposal of the contents of each hopper will occur in slightly different areas of the approved disposal site. Based on this approach and the exposed well mixed waters at the disposal site that will prevent contamination from building up in a particular location, minor changes in water quality that occur during disposal operations are expected to recover between dumping events. Indications are that the deepening of the estuary and coastal waters for the approach channel will also be expected to affect salinity, TSS and turbidity within the river. The approach channel may allow saltwater to move further into the estuary than would naturally occur and freshwater may as a result be transported more directly out of the river and estuary along the approach channel and across the shelf rather than mixing with nearshore water (2). These altered water flows may therefore change the salinity gradient within the river and estuary. Modelling (3) conducted for the Project has evaluated the potential changes caused by the access channel through comparison between the salinity and suspended sediment concentrations under natural conditions and in the presence of the access channel. To determine the maximum potential changes within the river and outside the river mouth the impact of the channel has been evaluated during spring tides. Changes to salinity and turbidity have been analysed during the modelling by comparing the salinity and suspended sediment concentration distribution on a transect that starts 8 km offshore from the Morebaya River mouth bar, and covers some 15 km landward of the mouth bar (Figure 7.13). This transect intersects the approach channel. The deepening of the riverbed may increase salinity upstream of the port site, especially in the wet season, with the subsequent impact being apparent several kilometres upstream. Based on modelling for spring tides salinity may change from typically less than 15 ppt to greater than 20 ppt. The early findings of the modelling indicate that changes will be much lower under dry season conditions, typically 1 - 2 ppt. This is understood to result from density driven flow which may lead to a larger vertical salinity variation during high flows. Deepening of the channel may result in greater stratification and potentially reduced oxygen conditions in the deep more poorly mixed higher salinity waters potentially leading to hypoxic conditions for some parts of the year. The modelling indicates that there will be similar impacts on suspended sediment concentration with significant reductions in SSC downstream at higher river discharges with a less pronounced impact under lower discharge conditions.

(1) Lee G.F.& Associates, El Macero, CA (1999). Oxygen Demand of US Waterway Sediments. Available at http://www.gfredlee.com/od_uswaterways.pdf. (2) Herbich, JB (2000). Handbook of dredging engineering. Edition 2, illustrated. McGraw-Hill Professional. (3) Deltares (2012). Preliminary Report on Supplementary 3D Wave, Hydrodynamics and Siltation Modelling.


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Figure 7.13 Location of the Cross-shore Transect and Points 1 and 2 in the Morebaya River

Source: Deltares 2012

(1)

The port will be designed to avoid untreated and uncontrolled discharges. Potentially contaminated run-off from port areas will be treated prior to discharge in line with project standards. Suspended solids in discharges are likely to be within the natural variability given the drainage systems that are part of the port design and the high natural suspended sediment concentrations. Sewage will be treated at a wastewater treatment works (WWTW) to design criteria as presented in Chapter 2: Project Description to avoid impacts and treated wastewater will be discharged to the river. The surplus sludge produced by the WWTW will be incinerated at the LSC1 camps facility and will not affect water quality. Sewage on vessels will be treated and discharged in accordance with MARPOL requirements (ie untreated sewage will not be discharged by vessels within 12 nautical miles from the nearest land and treated, comminuted and disinfected sewage will not be discharged less than three nautical miles from the nearest land and will therefore not affect water quality). Waste oils, lubricants, bilge water and other chemicals on vessels will also be managed in accordance with MARPOL and other relevant legislation and are not expected to significantly affect water quality. Ballast water will be discharged in line with IMO Guidelines for the Control and Management of Ships’ Ballast Water to Minimise the Transfer of Harmful

(1) Deltares (2012). Preliminary Modelling in Support of SEIA. Internal Project Engineering Studies.


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Aquatic Organisms and Pathogens. No ballast water discharges will be permitted in coastal waters for vessels coming from other bioregions. Acid sulphate soils (ASS) are commonly found in low-lying coastal areas, wetlands and mangroves. The potential impacts associated with ASS in the Project area have been assessed in Chapter 5: Geology, Soils and Mineral Waste. Vessels and machinery used during port construction have the potential to accidentally spill quantities of various fuels, lubricants and other contaminants. All bulk fuel and other hazardous materials storage areas will be designed to contain spills through appropriate impermeable bases, bunding capacities and maintenance and as such no significant routine pollution from these major sources would be expected. However, it is possible that small amounts of hydrocarbons are accidentally spilled into the marine and littoral environment, either directly (eg through fuel transfer, or pipe or tank flushing) or through run-off from hardstanding areas. Large spills, however, are also possible and may occur due to accidents such as collision of vehicles or vessels, grounding of vessels, extreme weather events, poor maintenance and operational and navigational errors. For example, in the event of an accidental total release of cargo from a midsize fuel tanker, up to 30 000 - 45 000 DWT of fuel could be released into the environment, potentially affecting a large area of marine environment and coastline with secondary impacts to a large range of aquatic fauna, flora and humans that depend on the coastal and marine waters. The impact of non-routine events has been assessed in terms of the risk. This is defined as the product of the consequence of the event and the probability of occurrence (risk = probability x consequence). Water quality throughout the Morebaya estuary and coastal region is considered to be of medium value because the existing (pre-development) water quality is moderate and is of value to species of conservation interest and communities. The impact to water quality from the dredge and dredge disposal plumes during port construction is considered to be of medium magnitude since a large area will be affected and the quality of the water resource would be reduced, but the long-term viability of the water resource and the species and communities dependent on it are not threatened. The impact on water quality from the dredge and dredge disposal plume is therefore of moderate significance. The impact to water quality in the Morebaya from the potential propagation of the saline wedge up the channel and increased stratification is consider to be of medium magnitude as its affect on water quality and dissolved oxygen will be seasonally variable and occur within a specific area and depth of the channel which will be a modified environment due to on-going dredging and vessel propeller wash. The impact on water quality from salinisation and stratification is therefore of moderate significance. The impact to water quality from discharges and run-off during port construction is considered to be of small magnitude because although an area of the estuary may be affected, dispersion is expected to be rapid and long-term viability of the water resource and the species and communities dependent on it are not threatened. The impact on water quality from the discharges and run-off is therefore of minor significance. The prediction of magnitude for non-routine impacts takes into account the risk of the impact ie the probability of occurrence as well as its consequences. The impact to water quality from minor unplanned spills is considered to be of small magnitude as only a limited area is likely to be affected. The impact to water quality from major unplanned spills is considered to be of large magnitude because regional water quality may be affected and the long-term viability of the species and / or communities dependent on it may be threatened. The impact on water quality from small spills is therefore of minor significance and the impact on water quality from large spills is of major significance, however, these impacts are likely to occur in exceptional circumstances only. 7.4.3.2 Water Quality Impacts during Port Operations Impacts to water quality during port operations may be caused by: sediment plumes from maintenance dredging and disposal of dredge spoil;


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changes to the bathymetry; discharges from vessels at sea (including sewage, oils, lubricants, bilge, ballast, wastewater and other

chemicals); discharges from onshore facilities such as sewage plants ; site run-off and drainage; iron ore dust from loading facilities; and unplanned spillages and pollution events. Impacts to marine fauna and flora are considered in Chapter 13: Marine and Littoral Biodiversity and impacts to non-saline surface and ground water are considered in Chapter 6: Water Environment. Impacts to water quality from the sediment plumes developing during maintenance dredging and the disposal of sediments at the offshore disposal area will occur in the same way as during the capital dredging operations undertaken for the port construction (Section 7.4.3.1). The annual volume of sediment dredged during the maintenance dredging operations will likely be less than the capital dredge volume. Modelling to determine the estimated amount is on-going. However, the nature of the sediment will be different since it will consist mainly of recently settled fine-grained material rather than undisturbed (possibly consolidated) material of various grain sizes. The impact to water quality from the dredging and sediment disposal plumes during port operations is considered to be of medium magnitude since it is likely maintenance dredging requirements will be similar to the capital dredging requirements. The impact on water quality from the maintenance dredging and sediment disposal is therefore of moderate significance. In common with construction, the impact to water quality in the Morebaya from propagation of the saline wedge up the channel and increased stratification is considered to be of medium magnitude as its affect on water quality and dissolved oxygen will be seasonally variable and occur within a specific area and depth of the channel which will be a modified environment due to on-going dredging and vessel propeller wash. The impact on water quality from salinisation and stratification is therefore of moderate significance. The impact to water quality from discharges and run-off during port operation will also occur in a similar way as those occurring during port construction. However, iron ore dust may be created during ore loading and the dust may settle on the water and become incorporated into the water column through mixing, or settle onto port areas and subsequently enter the marine environment as run-off. However, iron ore dust is not considered to be toxic and is unlikely to affect water quality unless large quantities of dust occurs and forms surface plumes. The potential for acid sulphate soils (ASS) to occur in the Project area has been assessed in Chapter 5: Geology, Soils and Mineral Waste. The port will be designed to avoid untreated and uncontrolled discharges. Potentially contaminated run-off from port areas will be treated prior to discharge. Suspended solids in discharges are likely to be within the natural variability given the drainage systems that are part of the port design and the high natural suspended sediment concentrations. The impact of run-off and discharges (including iron ore dust) on water quality is considered to be of small magnitude because although an area of the estuary may be affected, dispersion is expected to be rapid and long-term viability of the water resource and the species and communities dependent on it are not threatened. The impact on water quality from run-off and discharges during port operations is therefore of minor significance. The impact to water quality from unplanned events such as spills is considered to the same as during port construction. The prediction of magnitude for non-routine impacts takes into account the risk of the impact, ie the probability of occurrence as well as its consequences. The impact to water quality from minor unplanned spills is considered to be of small magnitude as only a limited area is likely to be affected. The impact to water quality from major unplanned spills is considered to be of large magnitude because regional water quality may be affected and the long-term viability of the species and / or communities dependent on it may be threatened. The impact on water quality from small spills is therefore of minor significance and the impact on water quality from large spills is of major significance, however the impacts are likely to occur in exceptional circumstances only.


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Plumes from dredging and sediment disposal may, without mitigation, result in moderate impacts to water quality during port construction and port operation. Changes in the salinity, mixing and dissolved oxygen of the channel, particularly the dredged section will result in moderate significant impacts to water quality during construction and operation. Discharges and run-off may, without mitigation, result in minor impacts to water quality during port construction and port operation. Unplanned small spills may, without mitigation, result in minor impacts to water quality and unplanned large spills may, without mitigation, cause major impacts during both port construction and port operation.

7.4.4 Impacts to Sediment Quality 7.4.4.1 Sediment Quality Impacts during Port Construction Impacts to sediment quality during construction may be caused by: sediment deposition due to dredging and sediment disposal; discharges from vessels at sea (including sewage, oils, lubricants, bilge, ballast, wastewater and other

chemicals); discharges from facilities onshore, such sewage; site run-off and drainage; and unplanned spillages and pollution events. Impacts to marine fauna and flora are considered in Chapter 13: Marine and Littoral Biodiversity and impacts to terrestrial soils are considered in Chapter 5: Geology, Soils and Mineral Waste. Sediments in the region are dominated by muds and sands, with patches of coarser sediments or hard substrate. Sedimentation resulting from dredging and dredged sediment disposal may alter the natural sediment particle size distribution across a wide area, which can impact marine biodiversity (see Chapter 13: Marine and Littoral Biodiversity). Initial results of dredge plume modelling undertaken for the Project state that sedimentation rates of up to 200 kg/m2 (or 1 m depth of sediment) across a 14 day period are likely within a few hundred metres proximity to two 5 000 m3 capacity dredgers working in parallel and sedimentation rates of less than 1 kg/m2 are likely within a radius of 10 km of the dredgers (see Figure 7.14). For a pair of larger capacity dredgers (30 000 m3), sedimentation rates of up to 200 kg/m2 (or 1 m depth of sediment) across a 14 day period are expected within 500 m of the dredgers, and sedimentation rates of less than 1 kg/m2 are likely within a radius of 15 km of the dredgers. At the offshore disposal site, sedimentation rates from sediment plumes only (ie not including the actual depth of disposed sediment) of up to 200 kg/m2 (or 1 m depth of sediment) across a 14 day period are likely within a hundred metres proximity to the disposal location for 5 000 m3 capacity dredgers and sedimentation rates of less than 1 kg/m2 are likely within 10 km (see Figure 7.14). For the larger capacity dredgers (30 000 m3), sedimentation rates from sediment plumes only of up to 200 kg/m2 (or 1 m depth of sediment) across a 14 day period are likely within several hundred metres proximity to the disposal location, and sedimentation rates of less than 1 kg/m2 are likely within 15 km. The actual size and shape of the sediment plumes is dependent on the currents and tidal cycles at the time of disposal.


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Figure 7.14 Sedimentation Rate from Dredging and Dredged Sediment Disposal (kg/m2)

Two operating TSHD (5 000 m3) Two operating TSHD (30 000 m3) Source: Deltares (2012) (1)

Over time, fine sediments that have settled out of the plume over a wide area will be redistributed by tidal currents and waves. Sedimentation from the sediment disposal will be of a much greater depth (up to 5 m accumulation) but will be confined to the approved disposal site. Once released, much of the sediment is expected to drop to the sea floor as a density current and blanket the seabed. The descending plume will spread in a lateral direction. Tidal currents and waves will redistribute some of the sediments, potentially into deeper waters given the bathymetry near to the disposal site, although changes in sediment composition at the disposal site are likely to be permanent. The port will be designed to avoid untreated and uncontrolled discharges. Potentially contaminated run-off from port areas will be treated prior to discharge. Suspended solids in discharges are likely to be within the natural variability given the drainage systems that are part of the port design and the high natural suspended sediment concentrations. Discharges and run-off may reduce sediment quality, which can result in impacts to the marine life living in and on the sediment. As described in Section 7.4.3 dispersion of discharges will be rapid within the water column and it is not expected that contaminants from pollutants will be found in high concentrations in the water column. Contaminants released by discharges and run off will ultimately adsorb onto sediment particles and subsequently settle out and become incorporated into estuarine and coastal sediments. It is not expected that regional sediment quality will be significantly affected. Vessels and plant used during port construction have the potential to spill quantities of various fuels, lubricants and other contaminants if unplanned accidents occur. Spillages of pollutants such as hydrocarbons may affect sediment quality. Pollutants such as diesel will float on surface waters but may wash onto exposed sediments at low tide and along the shores. Heavy fuel oils and weathered hydrocarbons may sink through the water column and become deposited onto and incorporated into sediments. These may reduce the quality of the sediments and its potential use by fauna and flora (see Chapter 13: Marine and Littoral Biodiversity). The value of sediment quality in the region is considered to be medium since the sediments are not significantly contaminated and they are of some value to species of conservation interest and communities. (1) Deltares (2012). Preliminary Modelling in Support of SEIA. Internal Project Engineering Studies.


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The impact to sediment quality from the sediment plumes forming during dredging and sediment disposal is considered to be of medium magnitude since sedimentation will occur across a wide area in the vicinity of the dredging operations. Sedimentation at the designated disposal site, although large in extent, is still small in comparison to the overall seabed available. Overall sedimentation is expected to affect the port study area viability and function of the sediments for marine species and communities in the short to medium term but not threaten the long-term viability of the species and communities dependent on it. The impact on sediment quality from the dredge and dredge disposal plumes is therefore of moderate significance. The impact to sediment quality from discharges and run-off is considered to be of small magnitude as a wide area may be affected but no loss of viability and / or function to species and the community is expected. The impact on sediment quality from the discharges and run-off is therefore of minor significance. The prediction of magnitude for non-routine impacts takes into account the risk of the impact ie the probability of occurrence as well as its consequences. The impact to sediment quality from minor unplanned spills is considered to be of small magnitude as only a limited area is likely to be affected. The impact to sediment quality from major unplanned spills is considered to be of large magnitude because port study area sediment quality may be affected and the long-term viability of the species and communities dependent on it may be threatened. The impact on sediment quality from small spills is therefore of minor significance and the impact on sediment quality from large spills is of major significance, however, these impacts are likely to occur in exceptional circumstances only. 7.4.4.2 Sediment Quality Impacts during Port Operations Impacts to sediment quality during port operations may be caused by: sediment deposition due to dredging and sediment disposal; discharges from vessels at sea (including sewage, oils, lubricants, bilge, ballast, wastewater and other

chemicals); discharges from facilities onshore, such as sewage; site run-off and drainage; and unplanned spillages and pollution events. Impacts to marine fauna and flora are considered in Chapter 13: Marine and Littoral Biodiversity and impacts to terrestrial soils are considered in Chapter 5: Geology, Soils and Mineral Waste. Impacts to sediment quality during maintenance dredging and the disposal of sediments at the offshore disposal area will occur in the same way as during the capital dredging operations undertaken for the port construction (Section 7.4.4.1). However, as discussed in an earlier section the volume of sediment dredged during the maintenance dredging operations will be less than the capital dredging. Maintenance dredging will only involve areas that have previously been dredged and therefore the sediment being dredged will consist of recently settled components of the natural system, including fine-grained sediments mobilised from adjacent areas under the influence of currents and tides, and sediment input from the Morebaya River, rather than undisturbed (possibly consolidated) material of various grain sizes. The impact to sediment quality from the maintenance dredge and dredge disposal sedimentation is considered to be of medium magnitude since it is likely annual maintenance dredging requirements will be similar to the capital dredging requirements. The impact on sediment quality from the maintenance dredge and dredge disposal sedimentation is therefore of moderate significance. The impact to sediment quality from discharges and run-off will also occur in the same way as during port construction. However, iron ore dust may settle on the water surface or enter the marine environment as run-off during the port operation and ultimately become incorporated into the local sediments. The natural sediments in the areas are already enriched in iron given the local geology and sediment transport regimes, and incorporation of the iron ore dust is not likely to significantly affect the function, viability and quality of the sediment. The impact of run-off and discharges (including iron ore dust) on sediment quality is considered to be of small magnitude because, although a wide area may be affected, dispersion is expected to be rapid and no loss of viability or function of the community is predicted. The impact of run-off and discharges on sediment quality is therefore of minor significance.


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The impact to sediment quality from unplanned spills is considered to be the same as during construction. The prediction of magnitude for non-routine impacts takes into account the risk of the impact ie the probability of occurrence as well as its consequences. The impact to sediment quality from minor unplanned spills is considered to be of small magnitude as only a limited area is likely to be affected. The impact to sediment quality from major unplanned spills is considered to be of large magnitude because port study area sediment quality may be affected and the long-term viability of the species and human communities dependent on it may be threatened. The impact on sediment quality from small spills is therefore of minor significance and the impact on sediment quality from large spills is of major significance, however, these impacts are likely to occur in exceptional circumstances only.

The sediment plumes and disposal may, without mitigation, result in moderate impacts to sediment quality during port construction and port operation. Discharges and run-off may, without mitigation, result in minor impacts to sediment quality during port construction and minor impacts to sediment quality during port operation. Unplanned small spills may, without mitigation, result in minor impacts to sediment quality and unplanned large spills may, without mitigation, cause major impacts during both port construction and port operation.

7.5 Mitigation Measures and Residual Impacts 7.5.1 Overview This section presents the proposed mitigation of potential impacts from port construction and port operation in the three areas of impact discussed above, namely: impacts to the geomorphological features; impacts to water quality; and impacts to sediment quality. Mitigation measures relevant to marine fauna and flora are considered in Chapter 13: Marine and Littoral Biodiversity, land and marine use and access are considered in Chapter 5: Geology, Soils and Mineral Waste and Chapter 16: Socio-Economic and Community Baseline, and surface and ground water are considered in Chapter 6: Water Environment. 7.5.2 Mitigation of Impacts to Geomorphological Features The principal mitigation measures associated with potential impacts to geomorphological features relate to appropriate planning of port facilities and their locations with respect to reducing potential impacts from altered hydrodynamics. The presence of port facilities and the approach channel will alter the natural environment and the local hydrodynamics regardless of the port design. However, modelling the likely effects is useful to inform minor adjustments to port design and channel alignments, where possible, may reduce impacts. Co-location of the port with MOF, minimisation of dredged areas where possible, and locating the dredge disposal area away from sensitive receptors, such as areas near the coastline, are all useful measures to reduce potential impacts to the marine environment. The Project will conduct monitoring to assess potential impacts to the coastline. Monitoring will include: a monitoring programme will be designed based on modelling output and satellite imagery to assess

natural change alongside Project induced change; monitoring of the shape and alignment of the coastline using satellite imagery; and


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comparison of the coastline for each monitoring event with previous monitoring results to assess coastline change.

If coastal change attributed to the port development is observed during the monitoring studies, the Project will develop, regularly review and update a coastal management plan. A Dredging and Spoil Disposal Management Plan (DSDMP) will be developed, regularly reviewed and updated for the port and implemented throughout construction and operation phases, as appropriate. The DSDMP will include measures covering dredging and dredged sediment disposal strategies for all aspects of the dredging operations. Measures of relevance to potential impacts to geomorphological features are outlined below. The Contractor will be required to provide modern fully equipped dredger(s) that, in accordance with Rio

Tinto Guidelines, meet the standards expected of best practice dredging in terms of the methods, processes and technology utilised to minimise environmental impacts.

Monitoring and automation systems to improve dredging accuracy and efficiency. Dredging and sediment disposal will only occur within the specified limits (both in area and depth)

through use of appropriate positioning technology. Mangrove shoreline will be left intact, where possible without compromising navigational safety or

construction access. Following implementation of the above mitigation measures, the residual impacts to geomorphological features in the study area are expected to be as follows. 7.5.2.1 Port Construction Impacts to the Seabed during Port Construction Pre-mitigation impacts related to the seabed and river bed were classified as minor and moderate significance respectively and the mitigation measures associated with refining the design of the port and the alignment of the approach channel, development of a DSDMP and managing direct impacts on the coastal areas, while helping to reduce the potential impacts, will not significantly change the level of impact; therefore residual impacts remain as minor significance for the coastal shelf seabed and moderate significance for the river and estuary bed. Impacts to the Sandy Beaches during Port Construction Pre-mitigation impacts related to the sandy beaches were classified as major significance and the mitigation measures associated with refining the design of the port and the alignment of the approach channel, development of a DSDMP and managing direct impacts on the coastal areas will reduce the level of potential impact; therefore residual impacts reduce to moderate significance. Impacts to the Mangrove Shoreline during Port Construction Pre-mitigation impacts related to the mangrove shorelines were classified as major significance and the mitigation measures associated with refining the design of the port and the alignment of the approach channel, development of a DSDMP and managing direct impacts on the coastal areas, will reduce the level of potential impact; therefore residual impacts reduce to moderate significance. Impacts to the Sandbanks and Mudflats during Port Construction Pre-mitigation impacts related to the sandbanks and mudflats were classified major significance and the mitigation measures associated with refining the design of the port and the alignment of the approach


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channel, development of a DSDMP and managing direct impacts on the coastal areas, will reduce the level of potential impact; therefore residual impacts reduce to moderate significance. 7.5.2.2 Port Operations Impacts to the Seabed during Port Operations Pre-mitigation impacts related to the seabed and river bed were classified as minor and moderate significance respectively and the mitigation measures associated with implementing the DSDMP and managing direct impacts on the coastal areas, while helping to reduce the potential impacts, will not significantly change the level of impact; therefore residual impacts remain as minor significance for the coastal shelf seabed and moderate significance for the river and estuary bed. Impacts to the Sandy Beaches during Port Operations Pre-mitigation impacts related to the sandy beaches were classified as major significance and the mitigation measures associated with implementing the DSDMP and managing direct impacts on the coastal areas will reduce the level of potential impact; therefore residual impacts reduce to moderate significance. Impacts to the Mangrove Shoreline during Port Operations Pre-mitigation impacts related to the mangrove shorelines were classified as major significance and the mitigation measures associated with implementing the DSDMP and managing direct impacts on the coastal areas will reduce the level of potential impact; therefore residual impacts reduce to moderate significance. Impacts to the Sandbanks and Mudflats during Port Operations Pre-mitigation impacts related to the sandbanks and mudflats were classified major significance and the mitigation measures associated with implementing the DSDMP and managing direct impacts on the coastal areas will reduce the level of potential impact; therefore residual impacts reduce to moderate significance. 7.5.3 Mitigation of Impacts to Water Quality The principal mitigation measures associated with impacts to water quality are the application of Project discharge criteria and use of the best available technology and best environmental practice during dredging with regards to the dredge plume. Best available technology and best environmental practice with regards to the dredge plume will be implemented through the DSDMP and relevant measures are highlighted below together with other mitigation measures to avoid and reduce impacts to water quality as far as reasonably practicable. The dredging contractor will be required to provide modern fully equipped dredger(s) that meet the standards expected of best practice dredging, including installation of technology normally associated with modern dredgers, in line with Rio Tinto guidelines. The type and size of dredger should also be selected based on the appropriate dredging method for the material being dredged and the characteristics of the dredging areas. In addition, the dredgers will have monitoring and automation systems to improve dredging accuracy and efficiency. Dredging and sediment disposal will only occur within the specified limits (both in area and depth) through the use of appropriate positioning technology. The extent of altered water quality can be reduced (but not eliminated) through management of the dredging process, including the use of specific technology and dredging techniques; most are commonly used during major dredging programmes worldwide. Equipment, technology and methods will be used to reduce the sediment plume, sediment spillage and overflow from the hopper and the creation of suspended sediments at the seabed. In addition drag heads will be designed to improve suction efficiency (thus reducing the dilution effect), all equipment will be calibrated correctly and an assessment will be made of the feasibility to enclose nearshore and river dredging zones using silt curtains to limit the extent of sediment plume and suspended sediments, where tidal, current and wave conditions permit.


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Monitoring and auditing of potential impacts on water quality that may arise from the dredging operations will include the following. Pre-dredge water quality monitoring:

temperature, salinity, conductivity, turbidity, TSS, light penetration, dissolved oxygen, pH and potential

contaminants of concern. Operational water quality monitoring:

temperature, salinity, conductivity, dissolved oxygen, pH, turbidity, light penetration, potential

contaminants of concern and TSS overflow from the hopper to ensure excessive volumes of sediment-laden water are not discharged; and

aerial photography during intensive plume monitoring surveys to monitor size and shape of sediment

plumes. Adaptive management:

monitoring of dredging activities should be conducted to evaluate the effectiveness of impact

prevention strategies, and to allow re-adjustment of mitigation measures where necessary. Monitoring, as described above, includes monitoring of salinity and dissolved oxygen within the Morebaya River, where changes to the salinity gradient may occur with potential impacts to marine species (see Chapter 13: Marine and Littoral Biodiversity) and coastal aquifers and surface waters (see Chapter 6: Water Environment). Many of the impacts from run-off and drainage will be avoided and reduced through the implementation of best practice and application of standards for discharge. All treatment plants and discharge points will be regularly inspected and maintained to ensure correct operation and that discharge quality meets Project discharge standards. If needed, run-off will be directed through sedimentation ponds to reduce the amount of suspended solids prior to discharge. As far as possible no work will be undertaken within 50 m of any surface waterbody, especially refuelling, maintenance and washdown of vehicles and equipment. Where this is not possible, additional measures such as bunding of vehicle refuelling, maintenance and washdown areas and the collection and treatment of run-off from those areas prior to discharge, will be taken to ensure that pollution of water resources does not occur. In addition, measures will be implemented to deal with acid sulphate soils in accordance with a Project-wide Acid Sulphate Soils Management Plan, if required. An effective preventative maintenance programme will be established to ensure that all equipment that uses or contains any hazardous materials (including fuel, oil etc) is inspected regularly and maintained in good working order. Inspection and maintenance records will be available for review. An Emergency Preparedness, Prevention and Response Plan will be developed for accidental spills and discharges. The Emergency Preparedness, Prevention and Response Plan will be implemented during each phase of activity. It will include: emergency scenarios; provision and location of spill response and clean up equipment; spill containment and clean-up procedures; communication and notification protocol; training of staff; and testing and emergency drills.

Use of marine pilots, navigational aids and controlled vessel movements (vessels will be held offshore for a berth to become available) will reduce the likelihood of potential collisions and spills.


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Following the implementation of the mitigation measures described above the residual impacts to the water quality in the study area are expected to be as follows. 7.5.3.1 Port Construction Impacts to Water Quality from Sediment Plumes Associated with Dredging and Sediment Disposal during Port Construction Pre-mitigation impacts related to water quality from sediment plumes during port construction were classified as moderate significance. The mitigation measures associated with implementing best practice dredging through the Project DSDMP and monitoring water quality before and during the dredging operations, will help to limit the development and spatial extent of sediment plumes but will not change the impact significance category; therefore residual impacts remain as moderate significance. Impacts to Water Quality Associated with Channel Deepening Pre-mitigation impacts to water quality in the Morebaya from the potential propagation of the saline wedge up the channel and increased stratification is consider to be of moderate significance. Water quality monitoring will provide data on the trends in changes in water quality and monitoring of ecological communities such as fish and of fisheries as part of the wider project monitoring. This monitoring and subsequent actions where required will help to reduce the extent of residual impacts but will not change the impact significance category; therefore residual impacts remain as moderate significance. Impacts to Water Quality from Discharges and Run-off during Port Construction Pre-mitigation impacts related to water quality from discharges and run-off during port construction were classified as minor significance and the mitigation measures associated with implementing best practice, application of standards for discharges and management of run-off, will help to reduce the level of impact; therefore residual impacts reduce to not significant. Impacts to Water Quality from Small Unplanned Spills during Port Construction Pre-mitigation impacts related to water quality from small unplanned spills during port construction were classified as minor significance and the mitigation measures associated with developing an Emergency Preparedness, Prevention and Response Plan, managing vehicle refuelling and vessel movements to reduce the chance of collisions will help to reduce the level of impact; therefore residual impacts reduce to not significant. Impacts to Water Quality from Large Unplanned Spills during Port Construction Pre-mitigation impacts related to water quality from large unplanned spills during port construction were classified as major significance and the mitigation measures associated with developing an Emergency Preparedness, Prevention and Response Plan and managing vessel movements to reduce the chance of collisions will help to reduce the likelihood of a large spill and the potential impact is reduced to moderate significance. 7.5.3.2 Port Operations Impacts to Water Quality from Sediment Plumes Associated with Dredging and Sediment Disposal during Port Operations Pre-mitigation impacts related to water quality from sediment plumes during port operations were classified as moderate significance and the mitigation measures associated with implementing best practice dredging through the Project DSDMP and monitoring water quality before and during the dredging operations, will help to limit the development and spatial extent of sediment plumes but will not change impact significance category; therefore residual impacts remain as moderate significance.


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Impacts to Water Quality Associated with Channel Deepening In common with construction pre-mitigation impacts to water quality in the Morebaya from the potential propagation of the saline wedge up the channel and increased stratification is consider to be of moderate significance. Water quality monitoring will provide data on the trends in changes in water quality and monitoring of ecological communities such as fish and of fisheries as part of the wider project monitoring. This monitoring and subsequent actions where required will help to reduce the extent of residual impacts but will not change the impact significance category; therefore residual impacts remain as moderate significance. Impacts to Water Quality from Discharges and Run-off during Port Operations Pre-mitigation impacts related to water quality from discharges and run-off during port operations were classified as minor significance and the mitigation measures associated with implementing best practice, application of standards for discharges and management of run-off, will help to reduce the level of impact; therefore residual impacts reduce to not significant. Impacts to Water Quality from Small Unplanned Spills during Port Operations Pre-mitigation impacts related to water quality from small unplanned spills during port operations were classified as minor significance and the mitigation measures associated with developing an Emergency Preparedness, Prevention and Response Plan, managing vehicle refuelling and vessel movements to reduce the chance of collisions will help to reduce the level of impact; therefore residual impacts reduce to not significant. Impacts to Water Quality from Large Unplanned Spills during Port Operations Pre-mitigation impacts related to water quality from large unplanned spills during port operations were classified as major significance and the mitigation measures associated with developing an Emergency Preparedness, Prevention and Response Plan and managing vessel movements to reduce the chance of collisions will help to reduce the likelihood of a large spill and the potential impact is reduced to moderate significance. 7.5.4 Mitigation of Impacts to Sediment Quality A change in water quality can lead to changes in sediment quality through the incorporation of contaminants from the water column on and into the sediments. Consequently the water quality mitigation measures presented in Section 7.5.3 will also mitigate impacts to sediment quality. Specifically, the dredging contractor will be required to provide modern fully equipped dredger(s) that meet the standards expected of best practice dredging, including installation of technology normally associated with modern dredgers, in line with Rio Tinto guidelines. The type and size of dredger should also be selected based on the appropriate dredging method for the material being dredged and the characteristics of the dredging areas. In addition, the dredgers will have monitoring and automation systems to improve dredging accuracy and efficiency. Dredging and sediment disposal will only occur within the specified limits (both in area and depth) through the use of appropriate positioning technology. The extent of altered sediment quality can be reduced (but not eliminated) through management of the dredging process, including the use of specific technology and dredging techniques; most are commonly used during major dredging programmes worldwide. Equipment, technology and methods will be used to reduce the sediment plume, sediment spillage and overflow from the hopper and the creation of suspended sediments at the seabed through the mechanisms described in Section 7.5.3. Monitoring and auditing of potential impacts to sediment quality that may arise from the dredging operation will include the following. Pre-dredge monitoring:


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bathymetry and sediment composition of the dredged sediment disposal grounds; and sediment particle size with respect to distance from the proposed dredge areas.

Operational monitoring:

rates of sedimentation in areas adjacent to the dredging footprint and in the vicinity of sensitive

receptors; sediment stability at the dredged sediment disposal ground; sediment particle size with distance from the dredging footprint; and bathymetry of the dredged sediment disposal grounds.

Adaptive management:

monitoring of dredging activities should be conducted to evaluate the effectiveness of impact prevention strategies, and to allow re-adjustment of mitigation measures where necessary.

Many of the impacts from run-off and drainage will be avoided and reduced through the implementation of best practice and application of standards for discharge. All treatment plants and discharge points will be regularly inspected and maintained and monitoring of discharge quality will be undertaken to ensure correct operation. Run-off will be directed through sedimentation ponds to reduce the amount of suspended solids prior to discharge and vehicle refuelling, maintenance and wash down areas will be bunded and the run-off from those areas collected and treated prior to discharge. During port operations, iron ore dust generated during vessel loading may settle on the water surface or enter the marine environment as run-off and ultimately become incorporated into the local sediments. As described in Section 7.5.3, an Emergency Preparedness, Prevention and Response Plan will be developed for accidental spills and discharges. The Emergency Preparedness, Prevention and Response Plan will be implemented during each phase of activity. It will include: emergency scenarios; provision and location of spill response and clean up equipment; spill containment and clean-up procedures; communication and notification protocol; training of staff; and testing and emergency drills.

Use of marine pilots, navigational aids and controlled vessel movements (vessels will be held offshore for a berth to become available) will reduce the likelihood of potential collisions and spills. Following the implementation of the mitigation measures described above the residual impacts to the sediment quality in the study area are expected to be as follows. 7.5.4.1 Port Construction Impacts to Sediment Quality from Sediment Plumes Associated with Dredging and Sediment Disposal during Port Construction Pre-mitigation impacts related to sediment quality from sediment plumes during port construction were classified as moderate significance. The mitigation measures associated with implementing best practice dredging through the Project DSDMP and monitoring sediment quality before and during the dredging operations, will help to limit the development and spatial extent of sediment plumes but will not change the impact significance category; therefore residual impacts remain as moderate significance.


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Impacts to Sediment Quality from Discharges and Run-off during Port Construction Pre-mitigation impacts related to water quality from discharges and run-off during port construction were classified as minor significance and the mitigation measures associated with implementing best practice, application of standards for discharges and management of run-off, will help to reduce the level of impact; therefore residual impacts reduce to not significant. Impacts to Sediment Quality from Small Unplanned Spills during Port Construction Pre-mitigation impacts related to sediment quality from small unplanned spills during port construction were classified as minor significance and the mitigation measures associated with developing an Emergency Preparedness, Prevention and Response Plan, managing vehicle refuelling and vessel movements to reduce the chance of collisions will help to reduce the level of impact; therefore residual impacts reduce to not significant. Impacts to Sediment Quality from Large Unplanned Spills during Port Construction Pre-mitigation impacts related to sediment quality from large unplanned spills during port construction were classified as major significance and the mitigation measures associated with developing an Emergency Preparedness, Prevention and Response Plan and managing vessel movements to reduce the chance of collisions will help to reduce the likelihood of a large spill and the potential impact is reduced to moderate significance. 7.5.4.2 Port Operations Impacts to Sediment Quality from Sediment Plumes Associated with Dredging and Sediment Disposal during Port Operations Pre-mitigation impacts related to sediment quality from sediment plumes during port operations were classified as moderate significance and the mitigation measures associated with implementing best practice dredging through the Project DSDMP and monitoring sediment quality before and during the dredging operations, will help to limit the development and spatial extent of sediment plumes but will not change level significance category; therefore residual impacts remain as moderate significance. Impacts to Sediment Quality from Discharges and Run-off during Port Operations Pre-mitigation impacts related to sediment quality from discharges and run-off during port operations were classified as minor significance and the mitigation measures associated with implementing best practice, application of standards for discharges and management of run-off, will help to reduce the level of impact; therefore residual impacts reduce to not significant. Impacts to Sediment Quality from Small Unplanned Spills during Port Operations Pre-mitigation impacts related to sediment quality from small unplanned spills during port operations were classified as minor significance and the mitigation measures associated with developing an Emergency Preparedness, Prevention and Response Plan, managing vehicle refuelling and vessel movements to reduce the chance of collisions will help to reduce the level of impact; therefore residual impacts reduce to not significant. Impacts to Sediment Quality from Large Unplanned Spills during Port Operations Pre-mitigation impacts related to sediment quality from large unplanned spills during port operations were classified as major significance and the mitigation measures associated with developing an Emergency Preparedness, Prevention and Response Plan and managing vessel movements to reduce the chance of collisions will help to reduce the likelihood of a large spill and the potential impact is reduced to moderate significance.


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7.6 Summary of Findings Table 7.7 summarises the predicted impacts, mitigation measures and residual impacts reported in this chapter.


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Table 7.7 Impact Summary Table

Description of Impact Evaluation Prior to Mitigation

Key Mitigation Residual Impact

Impacts to the coastal shelf seabed from changes in the hydrodynamic and morphodynamic regimes due to dredging and presence of port structures.

Minor

Design of port structures and alignment of approach channel to reduce impacts, where possible.

Implementation of a Dredge and Spoil Disposal Management Plan (DSDMP), including measures to monitor dredge footprint and not exceed planned footprint and spare mangrove, where possible.

Monitoring programme to assess potential impacts to the coastline and if coastal change is attributed to the port development of a coastal management plan.

Minor

Impacts to the river and estuary seabed from changes in the hydrodynamic and morphodynamic regimes due to dredging and presence of port structures.

Moderate Moderate

Impacts to the sandy beaches from changes in the hydrodynamic and morphodynamic regimes due to dredging and presence of port structures.

Major Moderate

Impacts to the mangrove shoreline from changes in the hydrodynamic and morphodynamic regimes due to dredging and presence of port structures.

Major Moderate

Impacts to the sandbanks and mudflats from changes in the hydrodynamic and morphodynamic regimes due to dredging and presence of port structures.

Major Moderate

Impact to water quality from the dredge and dredge disposal plumes. Moderate

(Construction)

Implementation of best practice dredging, including installation of technology normally associated with modern dredgers, in line with Rio Tinto guidelines.

Implementation of a Dredging and Spoil Disposal Management Plan (DSDMP).

Use of appropriate methods and equipment to reduce the development of sediment plumes.

Monitoring of water quality before and during dredging.

Moderate

Moderate (Operation) Moderate


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Impact to water quality from dredge channel indices salinisation and stratification. Moderate

(Construction)

Monitoring of water quality.

Monitoring of ecological communities and fisheries in line with wider project monitoring programme.

Moderate


Impact to water quality from discharges and run-off. Minor (Construction)

Application of relevant legislation and guidelines regarding discharge quality.

Regular inspection and maintenance of treatment plants and discharge points.

Potentially contaminated run-off will be directed through sedimentation ponds to reduce suspended solids prior to discharge.

Avoid any activities within 50 m of any surface waterbody where possible or implement measures such as bunding of vehicle refuelling, maintenance and washdown areas and the collection and treatment of run-off from those areas prior to discharge.

Implementation of a Project-wide Acid Sulphate Soils Management Plan (if an issue).

Not Significant

Minor (Operation)

Not Significant

Impact to water quality from unplanned spills. Minor – small spills

(Construction and Operation)

Implementation of an Emergency Preparedness, Prevention and Response Plan, which contains measures to reduce risk of spills and clean up any spills that may occur.

Use of marine pilots, navigational aids and controlled vessel movements (vessels will be held offshore for a berth to become available) will reduce the likelihood of potential collisions and associated spills.

Not Significant (Construction and Operation)

Major – large spills


Moderate (Construction and Operation)


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Impact to sediment quality from the sediment plumes and disposal. Moderate

(Construction)

Implementation of best practice dredging, including installation of technology normally associated with modern dredgers, in line with Rio Tinto guidelines.

Implementation of a Dredge and Spoil Disposal Management Plan (DSDMP).

Use of appropriate methods and equipment to reduce the development of sediment plumes.

Monitoring of sediment quality before and during dredging.

Moderate


Impact to sediment quality from discharges and run-off.

Minor (Construction)

Application of relevant legislation and guidelines regarding discharge quality.

Regular inspection and maintenance of treatment plants and discharge points.

Potentially contaminated run-off will be directed through sedimentation ponds to reduce suspended solids prior to discharge.

Avoid any activities within 50 m of any surface waterbody where possible or implement measures such as bunding of vehicle refuelling, maintenance and washdown areas and the collection and treatment of run-off from those areas prior to discharge.

Implementation of a Project-wide Acid Sulphate Soils Management Plan (if an issue).

Not Significant

Minor (Operation) Not Significant

Impact to sediment quality from unplanned spills.

Minor – small spills


Implementation of an Emergency Preparedness, Prevention and Response Plan, which contains measures to reduce risk of spills and clean up any spills that may occur.

Use of marine pilots, navigational aids and controlled vessel movements (vessels will be held offshore for a berth to become available) will reduce the likelihood of potential collisions and associated spills.

Not Significant (Construction and Operation)

Major – large spills


Moderate (Construction and Operation)

Documents

7 Marine and Littoral Physical Environment 7.1 Introduction · Simandou SEIA Volume III Port Chapter 7: Marine and Littoral Physical Environment 7-3 7.2.2 Legal and Other Requirements