10. Impact Assessment and Risk Significance

Transcription

1 Browse Section FLNG Development 10 IMPACT ASSESSMENT Draft Environmental AND RISK Impact SIGNIFICANCE Statement Impact Assessment and Risk Significance 10.1 Introduction This section describes and assesses the potential credible impacts to identified environmental receptors (physical, ecological, socio-economic and cultural) from activities associated with the Browse FLNG Development. Potential impacts from unplanned events such as spills are also considered. Each section considers: The source (refer to Section 5) and characteristics of the potential impacts. Receptors sensitive to potential impacts (refer to Section 6 and Section 7). Management and mitigation measures proposed for implementation (refer to Section 9). A detailed impact assessment has been conducted for all installation, commissioning and operation related activities, and details of decommissioning-related impacts have been provided where available. Potential impacts associated with decommissioning will depend upon the chosen strategy to be confirmed nearer the time of decommissioning (Section 5.5). A decommissioning EP will be developed prior to commencement of decommissioning activities and will be subject to acceptance by the relevant regulatory authority (Section 11). Potential impacts from activities during all phases of the Browse FLNG Development have been considered in this section and aspects relevant to each development phase have been summarised in Table Table 10.2 summarises the overall residual risk of environmental impacts associated with the Browse FLNG Development after the implementation of the management and mitigation measures identified in Section 9. The residual risk is an indication of the significance of the impacts, the definitions of which are provided in the risk assessment matrix in Figure 8.2. Detailed residual risk assessment for each aspect of the Browse FLNG Development is provided in the following sections. Particular focus is given to the assessment of potential impacts to receptors associated with the presence of the Scott Reef system 8 km away from the Torosa FLNG facilities. In general, the risk of impacts from development activities at Brecknock and Calliance locations is expected to be less than the risk associated with activities at Torosa. Similarly, the residual risk assessment provided in the sections below focuses on the worst case source of impacts, as described in Section 5, generally attributed to the operation of the FLNG facilities. It is expected that the risk of environmental impacts from other components of the Browse FLNG Development, such as the drill rig and vessels (including the flotel), will be broadly less than the risk associated with the operation of the FLNG facilities. Table 10.1: Summary of Aspects Relevant to the Activities of the Browse FLNG Development Aspect Drilling Installation and Commissioning Operation Physical presence of infrastructure Vessel and helicopter movements Seabed subsidence Artificial light Underwater noise Invasive marine species Non-hazardous solid waste Hazardous waste** Hydrotest fluid * Produced water Cooling water Sewage and sullage Drain discharges Subsea control fluids Desalination brine Drill cuttings and fluids Gaseous emissions Accidental chemical and waste discharges Accidental hydrocarbon releases * Hydrotest fluids may be discharged to the environment during operations only in the event of maintenance/repairs or new tie-ins ** Hazardous waste generated throughout the development life will not be discharged to the marine environment. Decommissioning

2 160 Browse FLNG Development Draft Environmental Impact Statement Table 10.2: Environmental Risk Assessment Summary Aspect Activity Potential Impact Proposed Management Approach Physical presence of infrastructure. Permanent subsea infrastructure. FLNG facilities and with associated exclusion zones. Seabed disturbance. Creation of artificial habitat and modification of existing habitat. Localised disturbance to currents and hydrodynamic processes. Collision by, or behavioural changes to, marine fauna (e.g. migratory whales, turtles, migratory birds, whale sharks). Interference with and exclusion of commercial fishing. Interference with and exclusion of Indonesian fishers. Interference with and exclusion of shipping vessels. Interference with and exclusion of tourism operators and recreational fishers. Interference with and exclusion of other users, including scientific research and industry and commerce. Loss of benthic habitat, associated biota and alteration of geomorphology. Increased suspended sediment and sedimentation. Disturbance to marine archaeology. The selection of FLNG technology for the development of the Browse resources inherently reduces the physical footprint of the development when compared to other development themes. FLNG facility and associated infrastructure locations are away from sensitive receptors such as Scott Reef and Sandy Islet. Benthic habitat surveys have been undertaken to identify unique or sensitive habitats and biota at selected subsea infrastructure locations, to be avoided in the design process. Geophysical survey data have also been used to identify potential subsea hazards such as shipwrecks. FLNG facilities will be located away from shipping lanes and approach and exit paths to Scott Reef that traditional Indonesian fishers would likely take. The main seawater intakes on the FLNG facilities will be at 150 m depth or greater, and will have mesh screens to limit ingress of marine fauna. Each FLNG facility will be gazetted and included on navigational charts, with a notice to mariners issued through the Australian Hydrographic Service to alert any other users present in the Development area of the location on the development infrastructure and associated activities. Operational radar and vessel tracking equipment will be in place on the FLNG facilities in accordance with Marine Orders 30 (Prevention of Collisions) and Marine Orders 21 (Safety of Navigational and Emergency Procedures). The location of subsea infrastructure, in particular flowlines, has been selected to limit seabed preparation, trenching and secondary stabilisation requirements to the level necessary to ensure pipeline integrity. Marine fauna observations will be recorded during drilling and installation activities at the TRE and TRD drill centres. A 500 m petroleum safety zone around the FLNG facilities will be gazetted under S616 of the OPPGS Act. Petroleum safety zones associated with surface infrastructure will be in place for as long as this infrastructure is operating; whereby petroleum safety zones associated with the drill rig and installation vessels near Scott Reef will be temporary. Shipwrecks identified during installation activities will be avoided and reported in accordance with Historic Shipwrecks Act Drill rig moorings will be deployed and retrieved using support vessels in order to minimise drag. FLNG moorings are designed to be permanent and installed under tension, which will minimise impact to the seabed and minimise the risk of entanglement for marine fauna. No permanent moorings will be installed within the lagoon at North and South Scott Reef. In the event other users present in the Development area interact with the FLNG facilities, support vessels would be able to render assistance in line with international norms for responding to maritime emergencies. Consultation will be ongoing with commercial fishers, recreational fishing groups and other relevant stakeholders that operate in the Development area. Fishing will not be allowed onboard the FLNG facilities, drill rig and installation vessels. Risk Assessment Summary C L Residual Risk F 2 Low

3 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 161 Aspect Activity Potential Impact Proposed Management Approach Risk Assessment Summary C L Residual Risk Vessel and helicopter movements. Vessel movements. Helicopter movements. Interactions with marine fauna and bird species. Interference and vessel collisions with other users in the area. Vessels associated with the Browse FLNG Development that are greater than 300 tonnes will be fitted with the Automatic Identification System (AIS) as per IMO requirements. Operational radar and vessel tracking equipment will be in place on vessels associated with the Browse FLNG Development in accordance with Marine Orders 30 (Prevention of Collisions) and Marine Orders 21 (Safety of Navigational and Emergency Procedures). Marine fauna observations will be recorded during drilling and installation activities at the TRE and TRD drill centres. Vessels associated with the Browse FLNG Development will adhere to standard maritime safety procedures including radio contact with approaching vessels and display of appropriate navigational beacons and lights in accordance with Marine Orders 30 (Prevention of Collisions) and Marine Orders 21 (Safety of Navigational and Emergency Procedures). Condensate tankers and LNG carriers associated with the Browse FLNG Development will be directed by trained pilots during berthing operations alongside the FLNG facilities. Condensate tankers and LNG carriers associated with the Browse FLNG Development will not travel through the channel between North and South Scott Reef during routine operations. Interactions between vessels associated with the Browse FLNG Development and whale sharks will be consistent with the Whale Shark Code of Conduct (DPAW 2013), whereby vessels will not travel at speeds greater than eight knots within 250 m of a whale shark and not intentionally approach closer than 30 m of a whale shark. Interactions of helicopters associated with the Browse FLNG Development with listed species will be in accordance with EPBC Regulations 2000 Part 8 Division 8.1: Helicopters will not fly below an altitude of 1000 feet within a 300 m horizontal radius of any observed whales (unless necessary for take-off and landings). Flights will occur predominantly in daylight. Scheduled helicopter flight paths will avoid seabird roosting areas such as Sandy Islet. Vessels associated with the Browse FLNG Development will operate in accordance with EPBC Regulations 2000 Part 8 Division 8.1 and Australian National Guidelines for Whale and Dolphin Watching whereby: Vessels will not knowingly travel greater than six knots within 300 m of a whale or 100 m of a dolphin. Vessels will not knowingly approach closer than 100 m to a whale or 50 m to a dolphin (except if bow riding). Vessels will not knowingly restrict the path of cetaceans. Vessels will take direct routes where possible, whilst avoiding significant areas such as Sandy Islet. F 2 Low

4 162 Browse FLNG Development Draft Environmental Impact Statement Table 10.2 continued: Environmental Risk Assessment Summary Aspect Activity Potential Impact Proposed Management Approach Seabed subsidence. Production operations from the Browse FLNG development. Reduction in light availability to corals and associated impacts to their growth rates. Increase in wave exposure. Change in geomorphological processes associated with wavemediated transport of sediment (sand), affecting Sandy Islet s size and stability. No management and mitigation measures have been identified that meet the safety and operational requirements for the Browse FLNG Development while reducing the risk of environmental impact from seabed subsidence associated with the development. Artificial light. Drill rig, vessels and FLNG facilities. Minor disruption to behaviour (attraction/ repulsion, disorientation) to marine turtles, resulting in a minor impact on a portion of the population (i.e. green turtles at Scott Reef). Minor behavioural disturbance (attraction/ disorientation) to seabirds or migratory birds, resulting in a minor and temporary disruption to a small portion of the population. Navigation beacons and lighting will be designed in line with the safety requirements of the International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA). FLNG facilities are designed for no routine flaring through the use of non-hydrocarbon purge gas in the flare system. Flaring will only be performed as necessary for safety reasons in emergencies or process upsets as well as during start up and planned shutdowns. Lighting in each operational area of the FLNG facilities will be kept to the minimum required for safe passage when personnel are not required to be working within the area. Risk Assessment Summary C L Residual Risk E 1 Low F 2 Low

5 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 163 Aspect Activity Potential Impact Proposed Management Approach Underwater noise. Noise emissions during routine FLNG, vessel and aviation operations. Minor and temporary behavioural disturbance to protected species (e.g. cetaceans) resulting in a minor disruption to a small portion of the population. The FLNG facility design and operating philosophy is to minimise pressure drop over subsea choke valves, therefore reducing operational noise. Thrusters on the FLNG facilities will only be operated where installation and operations require active heading control. Suction piling will be selected as the preferred anchoring method where practicable. Support vessels and helicopters will operate in accordance with EPBC Regulations 2000 Part 8 Division 8.1 and Australian National Guidelines for Whale and Dolphin Watching whereby: Vessels will not travel greater than six knots within 300 m of a cetacean or turtle (caution zone) and minimise noise. Vessels will not approach closer to the cetacean than 50 m for a dolphin and/or 100 m for a whale (with the exception of bow riding). If the cetacean shows signs of being disturbed, vessels will immediately withdraw from the caution zone at a constant speed of less than six knots. Interactions between support vessels and whale sharks will be consistent with the Whale Shark Code of Conduct (DPAW 2013), where support vessels will not travel greater than eight knots within 250 m of a whale shark (exclusive contact zone) and not allow the vessel to approach closer than 30 m of a whale shark. Interactions of helicopters with listed species will be in accordance with Part 8 of the EPBC regulations 2000: Helicopters will not fly below an altitude of 1,000 feet within a 300 m horizontal radius of any observed whales (unless necessary for take-off and landings). Flights will occur predominantly in daylight. Scheduled helicopter flight paths will avoid seabird roosting areas such as Sandy Islet. If VSP is conducted at a drill centre, it will be subject to pre-start marine fauna observations and soft start procedures to ensure sensitive fauna are not in the vicinity, in accordance with EPBC Act Policy Statement 2.1 Interaction between offshore seismic exploration and whales. Marine fauna observations will be recorded during drilling and installation activities at the TRE and TRD drill centres. Risk Assessment Summary C L Residual Risk F 2 Low

6 164 Browse FLNG Development Draft Environmental Impact Statement Table 10.2 continued: Environmental Risk Assessment Summary Aspect Activity Potential Impact Proposed Management Approach Invasive Marine Species. Vessel and rig movements. Ballast water exchange. Changes to habitat structure. Predation of native species (including commercial species). Potential impact on a Listed Place (Scott Reef). FLNG facilities will be inspected by a qualified IMS inspector prior to entry into Australian waters. FLNG facilities and vessels will be treated with an antifouling coating to prevent marine growth on hulls. All vessels and drill rig required in support of the Browse FLNG Development will be required to comply with the Woodside IMS Management Plan and Contractor Information Pack for Management of IMS. The plan defines an IMS Management Area that encompasses all nearshore waters around Australia, extending from the lowest astronomical tide mark to at least 12 Nm from land and in all waters less than 50 m deep (at lowest astronomical tide). All vessels and drill rig required to meet both Commonwealth and State ballast water and biofouling legislation and guidelines including the Ballast Water Management Requirements (AQIS 2008) and the National Biofouling Management Guidance for the Petroleum Production and Exploration Industry (Commonwealth of Australia 2009). A risk assessment process to assess the likelihood of a vessel or rig introducing IMS when transiting from overseas. Vessels entering waters within three nautical miles of Scott Reef for longer than 48 hours will be inspected for biofouling and IMS, and cleaned where required. The location of FLNG facilities in deep water and distant from Scott Reef, inherently reduces the risk of transfer and successful settlement of IMS at Scott Reef. In addition, the following adaptive management framework will be implemented specifically for the construction of FLNG facilities, as follows: A hull biofouling and IMS management plan will be developed in consultation with relevant authorities and implemented during the construction phase in South Korea (approximately two years). This management plan will include an FLNG facility monitoring program, and cleaning and inspection schedule. The monitoring program will be implemented during construction of the FLNG facilities and prior to departing the construction yard. The monitoring program and cleaning and inspection schedule for each FLNG facility will be adapted based on the findings of each monitoring / inspection event. Risk Assessment Summary C L Residual Risk C 1 Medium

7 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 165 Aspect Activity Potential Impact Proposed Management Approach Nonhazardous solid waste. Hazardous solid wastes. Generation of general nonhazardous wastes from offshore activities. Disposal of food scraps and other putrescible wastes from offshore facilties. Generation of hazardous solid wastes from offshore activities. Discharge of Insoluble salts from MEG reclaim with PW discharge. Release of Naturally Occurring Radioactive Materials (NORMs) contained in sand and scale (if produced) to marine environment. Potential impacts to the environment are not anticipated as non-hazardous wastes will not be discharged to the marine environment. As a result of resulting from disposal of food scraps and putrescible wastes, minor nutrient enrichment of surrounding waters in offshore open ocean waters above known biological effect concentrations outside of the predicted mixing zone. Potential impacts to the environment are not anticipated as hazardous solid wastes will not be discharged to the marine environment. Minor and temporary water quality contamination above background levels and known biological effect concentrations outside of the predicted mixing zone as a result of NORM release. Waste storage areas on development infrastructure and vessels allow segregation into recyclable and nonrecyclable wastes. Segregated waste on development infrastructure and vessels will be securely stored through the provision of appropriate waste receptacles and suitable containment measures such as lids and netting to prevent any loss of wastes to the marine environment. Generated non-hazardous solid waste will be transported onshore to a recycling contractor or appropriate waste disposal site in accordance with MARPOL 73/78 Annex V: Garbage (as implemented in Commonwealth waters by the Protection of the Sea (Prevention of Pollution from Ships) Act 1983) and Marine Orders - Part 95: Marine Pollution Prevention Garbage. No routine discharge of non-hazardous solid waste will take place at sea in accordance with Commonwealth Protection of the Sea (Prevention of Pollution from Ships) Act Parts IIIA and IIIC. Wastes will be managed in accordance with the relevant Browse FLNG Development EPs. Hazardous waste will be segregated in hazardous waste skips and drums or holding tanks (for liquid wastes) prior to disposal. Hazardous waste will be transported to shore for disposal in accordance with MARPOL 73/78 Annex III: Packaged Harmful Substances (as implemented in Commonwealth waters by the Protection of the Sea (Prevention of Pollution from Ships) Act 1983) and Marine Orders - Part 94: Marine Pollution Prevention Packaged Harmful Substances. Waste management measures will be included in the relevant EP(s), and will specify the appropriate disposal method for hazardous waste, including NORM and mercury-contaminated solids (if encountered) deemed unacceptable for discharge at sea, in accordance with the Commonwealth Radioactive Waste Management Act 2005, National Radioactive Waste Management Bill, Code of Practice for the Safe Transport of Radioactive Material (ARPANSA 2008). Hazardous waste will not be discharged at sea in accordance with Commonwealth Protection of the Sea (Prevention of Pollution from Ships) Act Parts IIIA and IIIC and Marine Order 94 (pollution prevention packaged harmful substances). Where applicable, hazardous waste will be handled and stored in accordance with the relevant MSDS and tracked from source to its final destination. In the event that hazardous waste is discharged accidently, crew onboard the relevant FLNG facility will intervene if safe to do so to clean up any spills. In the event that hazardous waste is released to the marine environment, any surface residue will be recovered where safe to do so. Risk Assessment Summary C L Residual Risk F 0 Low F 2 Low

8 166 Browse FLNG Development Draft Environmental Impact Statement Table 10.2 continued: Environmental Risk Assessment Summary Aspect Activity Potential Impact Proposed Management Approach Hydrotest fluid. Produced Water. Discharge of hydrotest fluid. Discharge of Produced Water to the marine environment (within regulatory discharge limits). Temporary decline in water quality due to discharge of oxygen-depleted hydrotest water and associated impacts to marine organisms. Toxicity to marine organisms due to chemical additives. Minor and temporary water quality comtamination above background levels and known biological effect (i.e. thermal and toxicity) concentrations outside of the predicted mixing zone. Total flowline length has been optimised to meet operational requirements, thereby reducing the volume of hydrotest fluid required. Subsea infrastructure installation schedule will be optimised to minimise the requirement for discharge and refill of hydrotest fluid. Hydrotest fluid will be selected for environmental performance (i.e. low toxicity chemicals) while maintaining technical performance requirements. Hydrotest fluid discharge will be detailed in the relevant EP(s) developed during the detailed engineering and design studies for the development. The plan will detail hydrotesting requirements, including details on the specific chemical additives to be selected as well as likely concentrations, volumes and frequency of discharges. The discharge of hydrotest fluid will be conducted in a controlled manner to ensure adequate dilution. Prior to the FLNG facilities being installed discharges will be conducted at depth, to maximise dilution. Post FLNG facility installation, MEG, if selected as the hydrotest fluid, will be recovered to the FLNG facilities for re-use or disposal. The FLNG facilities have been designed with capability to extract and store contaminated MEG salts for disposal onshore if required. Where practicable, design of the development infrastructure has also taken into consideration opportunities to reduce the need for chemical additives, including the use of CRA piping to reduce the need for injecting inhibitor chemicals to prevent internal corrosion of flowlines. Chemicals used will be selected to have the lowest environmental toxicity rating possible whilst meeting operational performance requirements in accordance with Woodside s chemical selection procedure. The PW discharge stream will be treated using a MPPE unit to reduce concentrations of hydrocarbons. The discharge of PW at the FLNG facilities will be conducted in deep water and away from sensitive receptors such as Scott Reef. PW discharge will be conducted below the water surface to maximise dispersion. MEG and water processing systems onboard the FLNG facilities are designed to minimise mercury levels within the PW discharge stream to comply with ANZECC/ARMCANZ (2000) guidelines for 99% species protection level (i.e. < mg/l) at the edge of the mixing zone predicted using hydrodynamic modelling (Section ). PW discharge will be monitored so that its hydrocarbon content is no greater than an average of 30 mg/l over any period of 24 hours. Baseline, periodic (triennial) and for cause toxicity testing of the PW stream will be undertaken against the recognised ecotoxicity assessment methodology defined in ANZECC/ARMCANZ (2000). Risk Assessment Summary C L Residual Risk F 2 Low F 2 Low

9 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 167 Aspect Activity Potential Impact Proposed Management Approach Cooling water. Sewage and sullage. Discharge of cooling water to the marine environment. Steam system purge/drainage for maintenance, discharged to the marine environment Discharge of sewage and sullage. Minor and temporary water quality contamination above background levels and known biological effect (i.e. thermal and toxicity) concentrations outside of the predicted mixing zone. Minor nutrient enrichment of surrounding waters in offshore open ocean waters above known biological effect concentrations outside of the predicted mixing zone. Cooling water systems have been designed to be segregated from process hydrocarbon streams. Cooling water discharge will be conducted below the water surface, to increase dispersion. The discharge of cooling water at the FLNG facilities will be conducted in deep water, away from sensitive receptors such as Scott Reef. Hypochlorite will be selected to control fouling in sea water systems in line with best practice, due to its high water solubility and biodegradability. During FLNG operations, temperature and chlorine concentrations of the cooling water stream will be monitored prior to discharge. Residual chlorine levels will be monitored with a target concentration of less than 200 ppb at the point of discharge with the exception of temporary periods of shock dosing at approximately 500 ppb. Cooling water discharges will be conducted as such that the resulting temperature increase will be less than 3 C above ambient, 95% of the time at the edge the mixing zone predicted using hydrodynamic modelling (Section ). Vessels associated with the Browse FLNG Development will hold, in compliance with MARPOL 73/78 Annex IV: Sewage (as applied in Australia under Commonwealth Protection of the Sea (Prevention of Pollution from Ships) Act 1983); AMSA Marine Orders - Part 96: Marine Pollution Prevention Sewage where, for example, they will hold: Fully operational sewage, sullage and putrescible waste holding tanks. Operational onboard sewage treatment plant approved by the IMO. Valid International Sewage Pollution Prevention Certificate (ISPP). The FLNG facilities will be equipped with sewage treatment systems compliant with the MARPOL73/78 effluent specification required for discharge within 3 Nm of land despite their location greater than 3 Nm from land. This will achieve an effluent discharge of higher quality than is required by international standards. Food scraps on the FLNG facilities, drill rig and vessels will be macerated to a diameter of less than 25 mm prior to disposal overboard, in accordance with MARPOL 73/78 Annex V: Garbage (as applied in Australia under Commonwealth Protection of the Sea (Prevention of Pollution from Ships) Act 1983) and Section 26F of the Protection of the Sea (Prevention of Pollution from Ships) Act Due to the close proximity of some activities associated with the Browse FLNG Development, there will be no discharge of untreated sewage within three nautical miles from Scott Reef. Risk Assessment Summary C L Residual Risk F 0 Low F 2 Low

10 168 Browse FLNG Development Draft Environmental Impact Statement Table 10.2 continued: Environmental Risk Assessment Summary Aspect Activity Potential Impact Proposed Management Approach Drain discharges. Subsea control fluids. Desalination brine. Discharge of drain discharges potentially containing oil and grease. Discharge of subsea control fluids. Discharge of desalination brine. Potential impacts are not expected as contaminated drain discharges will not be discharged to the environment. Minor and temporary water quality contamination above background levels and known biological effect concentrations outside of the predicted mixing zone. Minor and temporary change in water quality. The drill rig and FLNG facilities will be designed to allow segregation of drainage into open and closed drain systems. Onboard the FLNG facilities, drill rig and vessels, areas of potential contamination such as machinery and bulk liquid storage areas will be bunded to capture any spilled chemicals or oil residues. Drainage from these areas will be directed to holding tanks for treatment prior to discharge. An oil-in-water separator will be available onboard the FLNG facilities, drill rig and vessels, which will be maintained and operated so that the slops/bilge stream is treated to reduce hydrocarbon concentrations below 15 ppm in accordance with MARPOL 73/78 Annex I, as applied in Australia under the Commonwealth Protection of the Sea (Prevention of Pollution from Ships) Act 1983 (Part II Prevention of pollution from oil); Marine Orders 91 (Marine pollution prevention Oil) Discharges from slop tanks will be monitored to ensure specifications are met. Where discharge specification cannot be met for FLNG facility discharges, the discharge stream will be reprocessed or sent onshore for disposal. The subsea fluid control system selected for the Browse FLNG Development will employ a spare return loop such that, under routine operating conditions, where the spare return loop is not required, all LP hydraulic fluid is returned to the FLNG facility for re-use. Subsea control fluids will be selected in accordance with Woodside s chemical selection procedure on the basis of lowest health, safety and environmental risks while meeting operational requirements. Subsea fluid usage will be monitored through the life of the development. Desalination brine discharge will be conducted below the water surface, to increase dispersion. The discharge of desalination brine at the FLNG facilities will be conducted in deep water, away from sensitive receptors such as Scott Reef. Biocides and anti-scaling agents will be selected in line with best practice based on their low inherent toxicity, suitable for use in potable water systems. During FLNG operations, desalination brine discharge concentrations will be monitored prior to discharge. Risk Assessment Summary C L Residual Risk F 0 Low F 2 Low F 2 Low

11 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 169 Aspect Activity Potential Impact Proposed Management Approach Drill cuttings and fluids. Discharge of drill cuttings and fluids at the sea surface (Brecknock and Calliance reservoirs). Disposal of drill cuttings and fluids at depth (Torosa reservoir). Increased deposition of sediments in a localised area. Localised change in water quality through increase in suspended sediment and chemical composition of drill fluids. Potential impact on a Listed Place (Scott Reef). Well count and design have been optimised to meet recovery objectives and operational requirements thereby reducing the unnecessary use of drill fluids and generation of drill cuttings. If well design characteristics do not allow use of WBFs for all well sections, NWBFs will be selected in accordance with Woodside s chemical selection procedure. Risers will be used to ensure that NWBF and associated cuttings are recirculated to the drill rig for treatment prior to discharge. Solids control equipment will be available onboard the drill rig to reduce the amount of residual drill fluids on cuttings prior to discharge. There will be no discharge of whole NWBF at sea during drilling operations. Drill cuttings will be tested to confirm that residual NWBF remaining on the cuttings are limited to a maximum amount of 10% by dry weight of base fluid, prior to discharge overboard. Given the potential sensitivities of Scott Reef coral communities to sedimentation, Woodside will adopt an adaptive management strategy for the disposal of drill cuttings from Torosa wells. For those drill centres where surface discharge of drill cuttings results in impacts to the reef, alternative drill cuttings disposal techniques will be used, which may include: Discharge from the drill rig at a sufficient depth to allow acceptable dispersion to occur. Retain cuttings, store and ship to an offshore location away from the reef for offshore disposal. Retain cuttings, store and transfer to shore for disposal. Risk Assessment Summary C L Residual Risk E 1 Low

12 170 Browse FLNG Development Draft Environmental Impact Statement Table 10.2 continued: Environmental Risk Assessment Summary Aspect Activity Potential Impact Proposed Management Approach Gaseous emissions. Gaseous emissions emitted from diesel generators used on drill rig and support vessels to generate power; power generation using diesel and from FLNG facilities. Localised reduction in air quality. The FLNG facilities have been designed to include the following energy efficiency measures: Use of cold seawater as coolant rather than coastal seawater or air cooling. Use of low pressure boil-off gas in steam boilers (recovered from the LNG storage). Recovery of the boil-off gas generated from loading of LNG carriers (instead of flaring it) and compresses it for use as fuel gas which itself uses a lower pressure for firing steam boilers, thereby reducing boil-off gas compression duty. Use of nitrogen to purge the flare stack rather than hydrocarbon gas. Use of a three stage pre-cool system rather than two stage system in the liquefaction process to gain extra efficiency. Avoiding the need to incinerate the acid gas vent stream by routing to a high point on the flare stack for safe dispersion. All equipment, process controls, alarms and safety and shut down devices designed to operate to keep efficiency of combustion high, resulting in reduced gaseous emissions. Fuel usage will be recorded for FLNG facilities, drill rig and vessels associated with the Browse FLNG Development. Emissions will be derived from fuel usage. Initial commissioning/cool down process at each FLNG facility will be conducted using imported LNG and refrigerant cargos, thereby reducing the amount of commissioning flaring required. During operations, fuel gas will be used as the preferred fuel for FLNG processes (instead of diesel or crude oil). Mercury removal conducted prior to fuel gas extraction in processing system to minimise mercury traces contained in boiler exhaust, with the majority boiler fuel used in the processing system post treatment through the MRU. Vessels will comply with MARPOL 73/78 Annex VI (Prevention of Air Pollution from Ships) requirements as defined in the Marine Order 97 (Marine Pollution Prevention, Air Pollution) (pursuant to the Commonwealth Navigation Act 1912), where, for example, they will: Hold a valid International Air Pollution Prevention (IAPP) Certificate. Implement a preventative maintenance system to maintain diesel powered equipment for efficient operation. Use low sulphur diesel when it is available. Risk Assessment Summary C L Residual Risk E 1 Low

13 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 171 Aspect Activity Potential Impact Proposed Management Approach Hydrocarbon spills. Accidental hydrocarbon release to the environment. Impact on the sensitive receptors within the predicted areal extent of a hydrocarbon spill. Coating and/or smothering, leading to contamination and mortality. Contact with surface hydrocarbons can result in vital life functions being restricted, including the ability to feed and respire as well as loss of mobility and insulation. Toxicity effects, including sublethal and lethal effects caused mainly by aromatic hydrocarbon compounds, typically the most toxic and soluble compounds in hydrocarbons. Drilling Activities During drilling, proven systems and procedures will be employed. These will be applied and supervised by highly competent and experienced personnel to minimise the potential for loss of well control, leading to well blow-out. Drilling activities will only be undertaken when metocean conditions are deemed suitable for safe operations. Reservoirs will be isolated from the surface by a minimum of two independent and verifiable barriers. The configuration of isolation barriers during the drilling phase typically includes: Overbalanced hydrostatic pressure maintained on the reservoir via the drilling fluids. Drilling fluids are contained by the cemented casing to the mud line and riser to the rig. Seabed BOPs which can be activated to shut in the well in the event that well control via overbalanced drilling fluids is lost. A 500 m petroleum safety zone will be implemented at the drill rig. Relief well plans will be prepared and submitted to the relevant regulatory authority prior to commencement of any drilling activities. Commissioning and Operational Activities Hydrotesting will be undertaken prior to commissioning to ensure integrity of subsea systems and that there are no leaks in the subsea infrastructure. The configuration of reservoir isolation barriers during the operations phase typically incudes: Production tubing from the reservoir to valving on the subsea tree. Cemented casing and associated valving on the subsea tree, plus a production packer to isolate the annulus between the casing and production tubing from the reservoir. Although not classed as a secondary barrier, a Surface Controlled Subsurface Safety Valve (SCSSSV) will be fitted on all production wells. The wells, subsea system and FLNG facilities will utilise corrosion resistant materials and be designed to protect against integrity threats (e.g. corrosion, impact, erosion, low temperature embrittlement). Wellhead valve design and configuration allowing safe operation and control of the well. FLNG facilities have been designed with a double skinned hull and compartmentalised condensate storage. FLNG facilities are designed with drain systems to prevent spills overboard (Section 5). FLNG facilities are assessed against one in 10,000 year return period weather conditions. 500 m petroleum safety zones will be maintained at the FLNG facilities. Design codes and material specifications for all risers and flowlines will be compliant with the relevant Australian and international standards. Pipelines monitoring will be undertaken including: Monitoring of corrosion protection system. Periodic inspections using side scan sonar and ROV. Post-cyclone inspections if design environmental conditions are reached. Risk Assessment Summary C L Residual Risk B 1/0 Medium / High

14 172 Browse FLNG Development Draft Environmental Impact Statement Table 10.2 continued: Environmental Risk Assessment Summary Aspect Activity Potential Impact Proposed Management Approach Hydrocarbon spills (continued). Offloading and Refuelling Activities During Drilling and Operations Condensate offtake hoses will be fitted with dry break or breakaway couplings. Scuppers and save-alls, including those around tank vents, will be in place before commencement of refuelling activities. Diesel refuelling hose inventory will be drained before disconnection. Diesel refuelling station will be isolated and equipment stowed when not in use. Offloading and refuelling hoses will be certified as suitable for a safe operating pressure range. The hoses and fittings will also be compatible with support vessel/condensate tanker pump pressures. Support vessel/condensate tanker pumps will be fitted with relief valves to allow diverting back of fluids to source in the event of excessive pressure build up in the transfer hose. Where practicable, refuelling of support vessels will be conducted in port. Tank levels will be continuously monitored to prevent overflow, and tank level indication and level alarms are provided for diesel storage tanks. All vessels will be required to have in place a Ship-Board Oil Pollution Emergency Plan (SOPEP) including oil spill response measures. Offloading and refuelling will only be undertaken when metocean conditions are deemed suitable for safe operations. Offtake vessels will be piloted during berthing and offloading operations. Offloading and refuelling will be undertaken by trained personnel using defined procedures. During refuelling, personnel will be required to maintain continuous observation and vigilance of hoses, couplings and the sea surface, allowing for the rapid shutdown of fuel pump and spill response if necessary. Responsibilities and accountabilities will be defined for response and notifications to Woodside and relevant authorities. A loading plan (volume to be transferred) will be agreed between the supply point (vessel) and the delivery point, and a pre-load checklist completed. Transfer equipment and emergency shutdown functions will be checked immediately prior to commencement of offtake. The diesel transfer pump emergency shutdown system onboard the offloading vessel will be tested at the commencement of transfer. Communication (visual and/or radio) between the support vessel/condensate tanker will be maintained throughout refuelling and offloading operations. Risk Assessment Summary C L Residual Risk

15 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE Physical Presence of Infrastructure Background This section describes the potential environmental impacts from the presence of temporary or permanent infrastructure associated with the Browse FLNG Development such as the drill rig, wells, manifolds, flowlines, umbilicals, risers and FLNG facilities. Development infrastructure will be placed on the seabed, either on a temporary basis (e.g. drill rig anchors), or long-term basis for the operational life of the Development (e.g. wells, manifolds, flowlines and FLNG facility moorings) Impact Assessment Potential impacts from the physical presence of marine infrastructure associated with the Browse FLNG Development are: Seabed disturbance. Creation of artificial habitat and modification of existing habitat. Impacts to marine fauna. Disturbance to currents and hydrodynamic processes. Interference with and exclusion of other users of the area. Seabed Disturbance Seabed features and sediment characteristics within the Development area have been determined based on geophysical, sediment sampling and video surveys (Gardline 2009), supplemented by information from relevant scientific literature. A detailed description of seabed characteristics and associated benthos within the Development area is provided in Sections to Seabed disturbance throughout the life of the Browse FLNG Development will occur due to the direct placement of subsea infrastructure onto the seabed, anchoring of vessels and drill rig, seabed preparation works and piling of foundation supports for subsea structures (FLNG mooring systems) and removal of infrastructure during decommissioning (Section 5.5). Seabed disturbance may also occur in the event of unplanned dropped objects. Potential impacts from disturbance to the seabed are: Loss of benthic habitat and associated biota. Increased suspended sediment and sedimentation. Disturbance to marine archaeology (if present). Loss of Benthic Habitat and Associated Biota Subsea infrastructure and FLNG facility mooring systems will cover a total seabed area of approximately 67 ha (0.67 km 2 ) for the life the development. In addition, to provide a stable foundation for infrastructure at the eastern entrance of the channel between North and South Scott Reef (TRD and TRE drill centres), seabed preparation works along the flowline routes may be required. To ensure adequate mechanical protection and stabilisation of operational flowlines and subsea structures at these locations, additional seabed trenching and/or rock (concrete mattresses) placement may be necessary to prevent damage to the flowlines from upheaval buckling, seabed scouring or natural phenomena such as extreme weather events (Section 5.3.2). Protection is not anticipated to be required in the rest of the Development area, including in the deep waters of the Brecknock and Calliance subsea infrastructure locations. Within the Scott Reef channel, including the adjoining deepsea fan, video observations at a small number of sampling locations indicate that this stretch of seabed supports sparse sessile epifauna and burrowing infauna (Figure 6.11). Therefore, the areas of affected habitats are expected to be similar to surrounding contiguous seabed areas. As such, the potentially impacted benthic habitats and associated biota are well represented in the region and losses will represent a very small fraction of the widespread available habitat. The loss of soft sediment habitat may be partially compensated by creation of hard substrate artificial habitat from installation of subsea infrastructure, which may be colonised by epifaunal organisms. Benthic habitat survey data has been used during the design phase of the development to identify infrastructure locations that avoid sensitive habitats. Therefore, given these considerations, the risk of impact associated with the direct loss of benthic habitat due to seabed disturbance is assessed as low. The scale of seabed disturbance from anchoring is also expected to be small. The majority of installation and support vessels will use dynamic positioning systems to maintain position as the Development area is generally too deep for most vessels to anchor (greater than 350 m) with anchoring activities generally limited to the drill rig. Deployment of anchors for the drill rig will be undertaken by support vessels, further reducing the area of disturbance by minimising anchor drag. Seabed disturbance due to anchoring will be temporary and of small scale, only affecting a fraction of the large expanses of soft substrate seabed habitats spanning the offshore environment. There will be no anchoring in the South Scott Reef lagoon waters shallower than 100 m. The deep waters of the Development area are known to support common and well-represented epifaunal assemblages typical of soft sediment habitats in the region. Benthic habitat survey data will be assessed to avoid high value habitats when selecting anchoring locations to minimise potential seabed disturbance to unique or sensitive habitats and biota. Following removal of anchors and moorings, disturbed seabed areas will be available for recolonisation by benthic organisms. The risk of seabed disturbance due to temporary anchoring is assessed as low. Increased Suspended Sediment and Sedimentation If required, seabed preparation, trenching and secondary stabilisation operations, only planned at specific locations at Torosa, has the potential to result in a temporary localised decline in water quality due to an increase in suspended sediment concentrations and increased sediment deposition impacts to sensitive adjacent benthic communities. Seabed preparation, trenching and secondary stabilisation operations are not expected to result in adverse impacts to adjacent coral habitats as seabed sediments within the channel at Scott Reef are primarily comprised of coarse material (sand and gravel). The majority of sediments suspended during these activities are therefore expected to rapidly settle on the seabed within or relatively close to the area of disturbance. A turbid plume may develop from any fines contained in the

16 174 Browse FLNG Development Draft Environmental Impact Statement sediment which will gradually dilute as it disperses down current and through the water column. Brinkman et al. (2009) have determined that, owing to strong stratification in the water column, water masses deeper than 200 m are unlikely to be upwelled and reach Scott Reef. As these activities will occur in water depths greater than 350 m, sediment suspended at the seabed due to these works is not expected to reach surface waters of Scott Reef. Strong currents in the Scott Reef channel (RPS Metocean 2008) will also assist in dispersing any sediment plume developing during these activities. Compared to natural events such as storms and cyclones, which often cause large amounts of sediment to be lifted into the water column over large areas, the turbidity generated from seabed preparation, trenching and secondary stabilisation activities will be minor. Given the short duration of any necessary seabed preparation work, the low fines content of disturbed sediments, the scarcity and patchiness of benthic fauna and anticipated recolonisation of the seabed by similar benthic fauna on cessation of works (albeit at a slow rate), the risk of impact from an increase in suspended sediments associated with seabed preparation works is assessed to be low. Disturbance to Marine Archaeology Drilling and installation activities have the potential to result in the loss of marine archaeological resources, if present. It is an offence to destroy or damage, or interfere with any shipwreck covered by the Historic Shipwrecks Act 1976, whether the shipwreck location is known or unknown. With reference to national and West Australian databases, there are no known protected historic wreck sites within the deep waters of the Browse FLNG Development, where drilling and installation activities will take place. Furthermore, geophysical investigations undertaken in the Development area did not identify any seabed features of marine archaeological potential. Thus it is unlikely that an unknown shipwreck is present within the Development area. The closest protected historic wreck, the Yarra, located at South Scott Reef, is not in close proximity to installation activities and hence will not be impacted. The risk of impact to marine archaeology is therefore assessed to be low. Creation of Artificial Habitat and Modification of Existing Habitat Infrastructure present in the Development area, such as drill rig, subsea infrastructure and FLNG facilities, has the potential to act as artificial habitat through the provision of hard surfaces for the settlement of marine organisms that would not otherwise be successful in colonising the area. Colonisation of offshore infrastructure related to the oil and gas industry is well documented, with the processes commencing potentially within hours of installation (Shulman 1985). Where permitted, colonisation of structures over time both near surface and subsurface can lead to the development of a fouling community. Investigation of the fouling communities on platforms associated with the North West Shelf Project has found that complex ecosystems can develop within two years of being in place (Farrell 1992). The presence of structures and fouling communities may provide a food source for other organisms and may support localised fish aggregations by serving as artificial reefs (Gallaway et al. 1981). Fish are thought to congregate at artificial reefs because of lower risks of predation, higher prey densities and shelter from currents (Bohnsack et al. 1991; Spanier 1996). Therefore the physical presence of infrastructure may facilitate fish production through provision of increased habitat for juveniles, and the subsequent increase in adult individuals, resulting in a minor and localised positive benefit to local fish populations. Given the small scale of the artificial habitat created, the minor positive benefits are expected to be highly localised, with no anticipated effects on EPBC Act listed species and the Commonwealth marine area as a whole. The risk of impact associated with the creation of artificial habitats from the physical presence of marine infrastructure is therefore low. Modification of existing habitat, such as a shift between soft, muddy substrate on the seabed to the hard substrate of installed infrastructure can lead to an alteration of faunal and floral assemblages. The seabed sediments in the Development area are generally soft silt and clay (Fugro 2006; Gardline 2009). In terms of epifaunal abundance, survey data indicated that throughout the deep wasters of the Development area, epifauna was limited to sparsely distributed individuals including isolated scattered sessile crinoids, anemones, glass sponges and seapens. Occasional non-sessile fauna included urchins, prawns and other decapods, holothurians and sea stars. Changes in habitat structure may prevent these species from occupying soft sediment and may attract other species more suited to harder substrates. However, as epibenthic fauna in the deep waters of the Development area is sparse and of low diversity the creation of artificial habitats is not likely to significantly alter the local community structure. The risk of environmental impact resulting from the modification of existing habitat is therefore low. Impacts to Mobile Marine Fauna Subsea infrastructure is unlikely to affect marine fauna movements as the majority of which are located on the seabed. The FLNG facilities at the sea surface and risers in the water column only represent small surface and mid-water obstacles, which may only result in minor and localised deviations, without affecting migratory movements and patterns at a population level. Low numbers of migratory birds are expected to pass in the vicinity of the Browse FLNG Development due to a lack of emergent land suitable as nesting and roosting sites (mainly due to the small size of Sandy Islet) in comparison to other sites in the region. There is potential for localised and short term effects on birds through behavioural changes, including roosting on hard surfaces, or changes in feeding patterns in nearby waters associated with localised fish aggregations in proximity to infrastructure. Attraction of seabirds to offshore structures in the oil and gas industry has been previously documented (Tasker et al. 1986; Baird 1990). The FLNG facilities, drill rig and vessels will be lit at night, and therefore visible to birds transiting the area. Such attraction may alter the natural selection process as tired, weaker birds have the opportunity to rest. These behavioural changes are however only expected to locally affect the seabird community in the Development area, with no changes at population levels.

17 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 175 Offshore infrastructure is unlikely to pose a significant entanglement or collision risk in the open waters of the Development area for marine fauna. Routine operations associated with the Browse FLNG Development will result in sensory cues sufficient for marine fauna to be aware of the presence of the infrastructure, thus minimising the risk of collision. The risers linking the flowlines to the FLNG facilities, although deemed flexible, are held under tension load and set at an appropriately spaced distance. These characteristics preclude the risers from performing in a way that would cause entanglement to cetaceans or other susceptible marine fauna. Similarly, anchors and mooring chains employed for drill rig, installation vessels and FLNG facilities are unlikely to cause entanglement of cetacean species due to the dimensions of the chains and tension loads. The risk of impacts to marine fauna from the physical presence of infrastructure associated with the Browse FLNG Development is therefore assessed to be low. Disturbance to Currents and Hydrodynamic Processes The physical presence of infrastructure is expected to cause minor and localised alterations to the hydrodynamic regime directly around infrastructure, such as localised scouring or deposition around infield flowlines. Altered water movement may affect seabed features, bathymetry and water quality, in particular suspended solids and turbidity. Due to the dynamic nature of the existing hydrodynamic processes within the Development area and the relatively small area influenced by infrastructure, any impacts are likely to be localised. The risk of environmental impact from disturbance to hydrodynamic processes associated with development infrastructure is therefore assessed to be low. Interference With and Exclusion of Other Users of the Area The physical presence of marine infrastructure, FLNG facilities and vessels may cause disruption to other users of the area. Other users may include commercial fishing fleets, traditional Indonesian fishers, shipping vessels, tourism operators including recreational fishing vessels, scientific research vessels and other industry operators (Section 7). A number of stakeholders were engaged during the stakeholder consultation process, with a focus on other marine users (Section 3). The objectives of this process were to provide information, understand key environmental and social receptors and gain feedback. This stakeholder process will be ongoing throughout the life of the Browse FLNG Development. Commercial and Recreational Fishing Current commercial and recreational fishing activities are limited within the Development area given its remote, offshore location. Although movements of vessels will be prohibited in proximity to the drill rig and FLNG facilities through the implementation of a 500 m petroleum safety zone to prevent potential interaction between other users of the area and development infrastructure, any diversions required will likely be small (approximately 1 km) when compared to the total extent of movements by vessels operating in the offshore waters of the region. The petroleum safety zones set around the drill rig and FLNG facilities represent a very small proportion of the total fishing area available to commercial or recreational fisheries and any resulting impact is considered highly localised. As the FLNG facilities are located in water depths greater than 350 m, with no known subsea features of significance for fish populations in the area, it considered highly unlikely that the loss of access/ fishing grounds within the petroleum safety zone will affect current fishing levels in the region. Furthermore, only low trawl fishing activity has been recorded in the past ten years in the vicinity of Brecknock and Calliance locations (none at Torosa), and therefore it is unlikely that fishing activities would interact with subsea infrastructure. Traditional Fishing Indonesian fishers generally visit Scott Reef between the months of July and October (Section 7.3.2). They can only legally fish at the reef by traditional methods such as reef gleaning, free-diving, hand lining and other non-mechanised methods using small, nonpowered sailing vessels. Fishing is therefore limited to shallow waters and Indonesian fishers are only present in deep water areas during transit to and from reef locations. The presence of a drill rig and installation vessels at the TRD and TRE drill centres will have the potential to slightly disrupt the approach to Scott Reef by Indonesian fishers. However, drilling and installation activities will be temporary, and will only restrict passage through a limited, deep water area of the Scott Reef system. The nearest FLNG facility to Scott Reef is BWB-TR, located approximately 8 km to the east. As the FLNG facility locations are in over 500 m of water and there are no known submerged features of significance that might shelter fish within these areas, it is highly unlikely that the exclusion of fishing/access within the exclusion zones for the FLNG facilities will disrupt current use by Indonesian fishers. Given the size and visibility of each FLNG facility and permanent manning requirements, it is highly unlikely that Indonesian fishers could accidentally collide with the FLNG facilities. Shipping The main commercial shipping routes in the area are located approximately 50 to 100 km west of the Development area; hence shipping traffic will not be affected by the physical presence of infrastructure associated with the Browse FLNG Development. The resulting risk of impacting shipping activities is therefore low. Scientific Research Within the Development area scientific research is predominately undertaken at Scott Reef. A number of marine research and monitoring programs have been ongoing, particularly those conducted by AIMS and the WA Museum. AIMS have been undertaking long-term monitoring of coral and fish communities at Scott Reef since 1993, involving up to six trips a year to the reef. The WA DOF also conducts regular monitoring and research programs in the region of the Development area to collect fishery stock assessment data for management of each relevant fishery. Research/monitoring may take place on-board existing commercial vessels or independently using

18 176 Browse FLNG Development Draft Environmental Impact Statement dedicated research vessels. Based on the frequency of the monitoring programs and through enforcement of the 500 m petroleum safety zones and ongoing consultation with relevant stakeholders, the Browse FLNG Development will not impact on scientific research activities in the Development area. Industry and Commerce The North-west Marine Region supports a number of industries including petroleum exploration and production. Of the seven sedimentary petroleum basins in the North-west Marine Region, the Northern Carnarvon, Browse and Bonaparte basins are understood to hold large quantities of gas and comprise most of Australia s reserves of natural gas. There are several approved and prospective petroleum developments in the vicinity of the Browse FLNG Development including the approved Shell Prelude FLNG and INPEX Ichthys projects located 140 km and 105 km away respectively. All facilities will be regularly serviced by offshore support vessels. Through the implementation of 500 m petroleum safety zones there is little potential for vessel interaction. The risk of physical presence of infrastructure associated with the Browse FLNG Development affecting other offshore petroleum and exploration operators in the area is assessed to be low Vessel and Helicopter Movements Background This section details the impacts associated with the movement of vessels and helicopters through all phases of the Browse FLNG Development, including: Movements within the Development area. Movements between the Development area and the potential supply chain logistics and support location(s) on the mainland. Vessel and helicopter usage for the different phases of the development are summarised in Section 5.7. As vessel movements during the decommissioning phase are unknown at this stage, this phase of the development is not currently outlined. However, it is expected that decommissioning will use similar vessels to those engaged for installation activities, albeit for a reduced duration Impact Assessment Potential impacts from the movement of vessels and helicopters associated with the Browse FLNG Development are: Interactions with marine fauna and bird species. Interference with other users in the area. Interactions with Marine Fauna and Birds Vessel interactions with marine fauna may include vessel strike, disturbance and displacement. A range of species have the potential to interact with vessels associated with the Browse FLNG Development, in addition to those species described in Section 6.3. However, the risk of interaction and resulting impacts to marine species, whether offshore or nearshore species, is similar and has been described in further detail below to apply to all marine fauna. Vessel movements can potentially result in disruption of behaviour (e.g. feeding, nursing, mating, migrating) and displacement of marine fauna. The occurrence and extent of disturbance is likely to be variable and will depend on a range of factors relating to the animal and situation. Some behavioural disturbance may occur for short periods if marine fauna are present near the surface in the vicinity of transiting vessels or landing helicopters. However, the majority of vessel activity associated with the Browse FLNG Development will occur away from recognised marine fauna feeding and aggregation areas, and vessels will take direct routes where possible, avoiding significant areas (Section 9.2.2). Furthermore, disturbance to marine fauna from vessels in transit will be of limited duration as the vessels pass through an area. The potential for disturbance to marine fauna from vessels is also intrinsically linked to associated underwater noise, which is addressed in Section The risk of vessel strike to marine fauna is inherent to movements of all vessel classes (e.g. fishing vessels, recreational vessels, cargo ships). Vessels associated with the Browse FLNG Development will be similar in design and size to other vessels that operate in the oil and gas industry throughout Australian waters. Vessel speed has been demonstrated as a key factor in collisions with marine fauna such as cetaceans and turtles, with faster vessels having a greater collision risk than slower vessels (Hazel et al. 2007; Laist et al. 2001; Lammers et al. 2003). Laist et al. (2001) suggest that the most severe and lethal injuries to cetaceans are caused by vessels travelling at 14 knots or faster. The majority of vessels associated with the development will be displacement hull vessels travelling at relatively slow speeds in accordance with standard maritime practices (expected to be four to six knots in Scott Reef channel and one to two knots when operating near development infrastructure/flng facilities). Vessels transiting to and from the Development area and the mainland may operate at higher speeds to meet operational requirements (e.g. personnel transfers); however such movements (estimated at two to three transits per week) will not represent a significant increase in vessel traffic levels associated with the potential supply chain and logistics support location(s) (Section 5.7), as well as levels observed for the wider region (Section 7.3.4). A review of collisions between ships and whales (Laist et al. 2001) reported that collision avoidance strategies dependent on detecting and actively avoiding any whales spotted on route may be ineffective for large ships with limited manoeuvrability. The study concluded that collision avoidance strategies were more effective when these consisted of avoiding areas of increased cetacean densities. As development vessels will take direct routes, avoiding significant areas such as the waters surrounding Sandy Islet and known areas of cetacean aggregation such as Camden Sound, to minimise potential interactions with marine fauna, the likelihood of interacting with cetaceans when vessels are in transit is reduced. According to recent Australian reports on ship strikes to the International Whaling Commission (IWC) (IWC 2007, 2008, 2009), the level of ship strike in Australia is regarded as low with only a minority of the recorded incidents occurring in WA in spite of the large annual migration of humpback whales in coastal waters. Considering the already established oil and gas industry

19 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 177 on the North West Shelf and the steady increase (approximately 10% per year) in humpback whale numbers (Bannister and Hedley, 2001), this would demonstrate that oil and gas vessels have no influence on the whale population from collision. Furthermore Laist et al. (2001) also noted that vessel strikes would be more significant to small cetacean populations. The risk of vessel strike to cetaceans is considered low as pygmy blue whales, humpback whales and other marine cetaceans do not occur in large numbers in the deep waters of the Development area. The majority of vessel activity will also be occurring away from recognised cetacean aggregation areas, such as the humpback whale migration corridor along the mainland coast (Section ). Activities within this area will be limited to vessels travelling to the Development area from supply chain and logistics support location(s). While transiting to and from the mainland, vessels will be travelling in accordance with best maritime practice, whereby vessel speeds will be adjusted depending on environmental conditions (e.g. visibility, metocean conditions) as required by the captain of the vessel. In inshore waters, vessels will operate in accordance with the specific requirements of each port authority managing the supply chain and logistics support location(s) these vessels are operating within. Turtles, during nesting in inter-nesting periods at Sandy Islet, may also be at risk from vessel strike whilst individuals are present on the surface or in shallow waters. Although turtles periodically return to the surface to breathe and to rest, only a small portion (3 to 6%) of their time is spent at the surface with routine dive times lasting anywhere from 15 minutes up to nearly an hour (Milton and Lutz 2003). Turtles will typically avoid vessels by rapidly diving but their ability to be able to respond in this manner is largely dependent on the speed of the approaching vessel and the surface activity of the turtle, i.e. breathing only or resting. The slow speed of development vessels while operating in areas where turtles may be present in greater numbers than in offshore deep waters, such as Scott Reef, is expected to allow turtles to avoid interaction by diving and swimming away. Impacts to marine turtles associated with vessel movements are likely to be limited to a small number of individual turtles, if any, and unlikely to threaten population viability. Whale sharks are at risk from vessel strike whilst feeding at the surface or in shallow waters where they may come into contact with vessels. Survey records indicate this species has seldom been sighted in the region of the Browse FLNG Development, suggesting only small numbers of these animals pass through the Browse Basin. Due to the small numbers of whale sharks and the lack of known aggregation areas in the Browse region, as well as the slow speed of project related vessels operating in the area, the risk of vessel strike is considered low. However, the risk of impact is increased during the installation phase, when vessel traffic will be increased. In the unlikely event of vessel strikes any related impact will not threaten overall population viability. The number of helicopter flights required during installation and operation of the development will be optimised to maximise efficiency and reduce the number of flights where operationally possible. Given the high visibility and noise levels associated with helicopter movements, bird species are expected to actively avoid interaction. In addition, seabirds and migratory shorebirds are expected to be in low numbers as the Development area does not represent a significant aggregation, nesting or roosting area for seabirds and migratory shorebirds, and where flights occur in proximity of areas of known importance to marine fauna or bird species, flight paths will actively avoid these areas where practicable. The overall risk of disturbance to marine fauna and bird species from vessel and helicopter movements leading to behavioural changes or displacement affecting overall population viability is therefore assessed to be low. Interference with Other Users in the Area Vessel movements associated with the Browse FLNG Development could potentially increase interactions with shipping and fisheries activities. The estimated vessel numbers are described in Section 5.7. The risk of impact would be greatest during the installation phase due to the increased number of vessels in transit to and from the Development area. However, even during installation, the increase in vessel traffic generated by the development represents a small incremental increase in the overall shipping traffic of the area. Similarly, given the remote location from established commercial shipping routes, the risk of impacts arising from vessels movements in the Development area on commercial shipping and navigation is assessed to be low Seabed Subsidence Background Subsidence Estimates Production activities associated with the Browse FLNG Development, through the extraction of naturally high pressured reservoir fluids, will cause a reduction in the reservoir s pressure, which has the potential to result in compaction of the geological layers leading to gradual low magnitude subsidence at the seabed. Although this is not deemed significant based on the location of the Brecknock and Calliance reservoirs, as the Torosa gas reservoir spans an area approximately 50 km by 15 km, approximately half of which lies beneath Scott Reef (Figure 5.1), seabed subsidence resulting from extraction of hydrocarbons from the Torosa reservoir has the potential to affect Scott Reef. Woodside has modelled the magnitude of subsidence and associated horizontal movements for the Browse reservoirs. Analyses have taken into account a range of parameters, including the geological/fault structure of the reservoir, its spatial dimensions, the hydrocarbon reservoir thickness and its depth, reservoir temperature and pressure as well as pore compressibility in the reservoir. These analyses have been supported by field measurements and laboratory tests on core samples obtained from exploration wells within the Browse reservoirs. Initial estimates of subsidence provided in 2011 ranged from 2.1 cm and 7.1 cm, averaging 4.4 cm over the life of the reservoir (approximately 40 to 50 years). Subsidence estimates have since been revised, reflecting Woodside s increased knowledge of the Torosa geological and reservoir characteristics. Revised estimates ranged between 2.6 cm and 8.9 cm, with average vertical seafloor movement totalling

20 178 Browse FLNG Development Draft Environmental Impact Statement approximately 5.4 cm over 40 years (0.6 to 2.2 millimetres per year (mm/yr)). This estimate remains broadly similar to the original modelling estimate and provides further confidence that subsidence, as a result of gas extraction from the Torosa reservoir, will be in the order of less than 10 cm. Average subsidence was predicted to occur over a radius of about 10 km centred on a point in deep water on the eastern side of North Scott Reef. The magnitude of subsidence is predicted to diminish away from this point up to 18 km. Beyond 20 km, the magnitude of subsidence would be virtually nil. The phenomenon of subsidence due to oil and gas production is considered rare and is mostly imperceptible or low magnitude with only a few reported instances (approximately 40) known in the industry worldwide. Instances where higher magnitude production-induced subsidence has been recorded have included reservoirs located in the offshore North Sea region (44 cm/year at Ekofisk), onshore California (22 cm/year at Wilmington and up to 20 cm/year at South Belridge), offshore Malaysia (M3), offshore Indonesia (Arun) and offshore Oman (4.5 cm/year at Yibal) Impact assessment Potential Impacts of Subsidence Potential impacts of subsidence on corals at Scott Reef are dependent on the rate of coral accretion expected at Scott Reef over the life of the development. Analyses of cores taken from the margin of Scott Reef (Collins et al. 2009) indicated that Scott Reef has previously experienced sea level changes, with five growth phases identified over the past 400,000 years, each 30 to 50 m thick, corresponding to episodes of sea level rise through time. Based on these analyses, vertical accretion rates of corals at Scott Reef were found to vary from 1.4 to 3.5 mm/yr. This indicates that corals at Scott Reef could respond successfully to sea level changes associated with production at Torosa, with predicted subsidence well within natural vertical accretion rates observed at Scott Reef. The impact of production-induced subsidence to Scott Reef and Sandy Islet would therefore be expected to be insignificant or temporarily positive. Based on subsidence resulting in a maximum 8.9 cm increase in water depth over a 40 year production period, there may be an initial period of increased coral cover on the reef flat and possibly an increase in the size or height of Sandy Islet during this period. At the end of the development life, the reef would regain its former height in relation to sea level and the coral communities at Scott Reef and Sandy Islet would be expected to return to a state similar to that observed prior to subsidence. Under this scenario there would be little impact to the availability of green turtle nesting habitat at Sandy Islet. In addition, Scott Reef and Sandy Islet experience considerable variability in sea levels over different time scales. Tides at Scott Reef are semi-diurnal with a maximum daily range of approximately 4 m. Sea levels also vary by tens of centimetres in response to large-scale oceanographic and atmospheric processes, such as the passage of mesoscale ocean eddies and inverse barometer effects with the passing of cyclonic and anticyclonic pressure systems (where sea levels increase in areas of low atmospheric pressure, and vice versa). During El Nino years, up to 20 to 30 cm increases in sea levels occur from the eastern Pacific Ocean to the eastern Indian Ocean. Satellite data (TOPEX/Poseidon) from 1992 to 2009 show intra- and inter-annual sea level variability in the vicinity of Scott Reef to be from 30 cm below to 40 cm above MSL (Cooper et al. 2010). Therefore, production-induced subsidence is deemed small in comparison to the range of natural sea level variability that is experienced at Scott Reef during the present day. Impacts of Subsidence in the Context of Climate Change Over the life of the development (approximately 40 to 50 years), it is predicted that sea levels may be affected by climate change (IPCC 2007, 2013). As a result, Scott Reef may experience a higher rate of water depth increase from climate change than due to potential production-induced subsidence alone over that timeframe. Environmental impacts associated with such increased water depths may include a reduction in light availability to corals and associated impacts to their growth rates, increases in wave exposure, and changes in geomorphological processes associated with wave-mediated transport of sediment (sand), which could affect Sandy Islet s size and stability. Sea level change estimates projected by IPCC (2007) ranged between 1.8 to 3.8 mm/yr. The worst-case highest rate of sea level change assumed atmospheric CO 2 concentration reaching 600 ppm (compared to 369 ppm in 2000). The most recent IPCC report (2013) however reports revised sea level change estimates ranging from 3 to 11 mm/year, based on worst-case atmospheric CO 2 concentrations reaching up to 936 ppm in The report also predicts that by 2100, one to two-thirds of the world s coral reefs will be subject to long-term degradation under various scenario assumptions (ranging from 0.94 to 1.6 C increase in sea surface temperature, and 0.26 to 0.63 m sea level rise). Ocean ph, expected to be 0.4 to 0.5 ph units (log scale) lower than current values by 2100, will also likely slow coral growth rates (Cooper et al. 2008; De ath et al. 2009; Hoegh- Guldberg 2005; Kleypas et al. 1999). More intense tropical cyclones will likely increase the frequency of major disturbances. Woodside commissioned AIMS to assess the potential impacts of subsidence on Scott Reef s coral habitats and Sandy Islet in the context of climate change (Cooper et al. 2010; AIMS 2012b). AIMS assessed both sea level changes due to productioninduced subsidence only and the combined sea level changes associated with a range of climate change scenarios over the life of the Torosa reservoir. Table 10.3 summarises the net change in water depth (MSL) at Scott Reef that could occur over a 40 year production period. This assessment was conducted based on the following information: The range of subsidence derived from Woodside s modelling studies. Historical coral accretion rates at Scott Reef (Collins et al. 2009). Sea level change predictions (IPCC 2007). Coral growth rates under the influence of climate changeinduced increases in sea temperature and increased ocean acidity due to increased atmospheric CO 2 concentration.

21 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 179 Table 10.3: Summary of Net Rise from MSL at Scott Reef Predicted to Occur Over a 40 Year Production Period (AIMS 2012b; Cooper et al. 2010b) Scenario Vertical Accretion (cm) (a) Net Vertical Accretion (cm) (b) Subsidence (cm) (c) Sea Level Rise (cm) (d) Subsidence & SLR (f) Net Rise in Sea Level* (cm) Subsidence only (g) SLR only (h) Best case (-4.7**) 0 (-11.9**) 0 (-6.8**) Intermediate case * 3.4 Worse case (a) Vertical accretion rates based on 1.4 to 3.5 mm/yr, for a 40 year production period (Collins et al 2009) (b) Net vertical accretion rates, incorporating declines in coral growth of 0% for best-case, 20% for intermediate-case, and 50% for worse-case from Reynaud et al. (2003); Cooper et al. (2008); De ath at al. (2009) (c) lower to upper range of estimates of production-induced subsidence provided by Baker Hughes (2012) (d) lower to upper range of estimates for sea level rise (SLR) reported by IPCC (2007) *Net rise is calculated as follows: (f) = (b)-((d)+(c)); (g) = (b)-(c); (h) = (b)-(d) **Negative values indicate that the potential for reef growth exceeds the rate of sea level rise combined with subsidence. Net rise on the reef flat would actually be zero since corals cannot grow above maximum sea level. Net vertical accretion rates for corals reflect the reduced vertical accretion rates due to potential climate change related effects on coral growth (Table 10.3). Warming sea surface temperatures will likely increase the frequency of coral bleaching events that can result in mass mortality and reduced growth rates (van Oppen and Lough 2009). In the worst case scenario, a 50% reduction in coral reef growth was assumed due to 2 C ocean warming, ph ocean acidification and Category five cyclone occurrence every three to five years (Cooper et al. 2010). The intermediate case assumes a 20% decrease in coral reef growth associated with 1 C ocean warming, -0.1 ph ocean acidification and Category five cyclone occurrence once a decade (Cooper et al. 2010). No reduction in coral reef growth was assumed in the best-case scenario with less than1 C ocean warming and little change in ocean acidity or cyclone occurrence (Cooper et al. 2010). The environmental consequences associated with water depth increasing up to 19.5 cm as a result of combined subsidence and climate change were assessed for: Reef flat habitat (0 to 5 m). Shallow water coral habitats (5 to 30 m). Deep water coral habitat (30 to 70 m). Sandy Islet. Reef Flat Reef flat habitat represents a harsh environment for coral growth due to wave exposure and periodic exposure at spring low tide. Corals in this habitat have low cover (less than 5%) and comprise stunted hardy robust forms due to tidal exposure and storm impacts (Section 6.3.2). Worst-case: With a 19.5 cm increase in MSL (7.1 cm due to subsidence), there is potential that corals on the reef flat may benefit from additional space for upward growth and increase in coral cover. Although wave exposure may increase, it is unlikely that reef flat corals would be adversely affected as they are robust forms. However, worst case climate change predictions also result in an increased frequency of coral bleaching, reduced growth due to ocean acidification, and increased damage due to cyclones. Any significant changes in reef flat coral communities due to adaptation to increased MSL and climate change related effects would occur regardless of 7.1 cm of subsidence. In the worst-case, the impact to reef flat corals contributed by production-induced subsidence would be negligible. Intermediate-case: With a 7.8 cm increase in MSL (4.4 cm due to subsidence), it is considered that the change in waveexposure and water depth conditions would not be sufficient to elicit any perceptible changes to reef flat coral communities on its own. Water depth would be within 1 to 3% of total present day sea level range. The increase in duration of tidal inundation would be slight and increases in available wave energy are likely to be minor. Increase in water depth may allow marginally more space for upward growth and increase in coral cover. However, under the intermediate climate change scenario, reef flat corals would also be susceptible to increased bleaching and ocean acidification, thereby potentially offsetting any benefits related to the increase in water depths. Overall, conditions associated with the intermediate-case scenario are unlikely to result in significant adverse impacts to reef flat corals. Any impact to reef flat corals due to climate change related effects will occur regardless of 4.4 cm of subsidence. In the intermediate case, the impact to reef flat corals contributed by production-induced subsidence would be negligible. Best-case: With a 4.7 cm net decrease in MSL (2.1 cm increase due to subsidence), reef flat corals would be expected to continue to be limited in their upward growth by sea levels. As with the present day, the vertical growth potential of reef flat corals would exceed that needed to keep pace with sea level rise and production-induced subsidence. Sea level change would be less than 1% of the daily tidal range. Overall, in the absence of climate change related impacts to coral growth, impacts to reef flat corals would be negligible.

22 180 Browse FLNG Development Draft Environmental Impact Statement Shallow-water Coral Shallow water coral habitats are the most diverse coral habitats at Scott Reef (Section 6.3.2). They are also susceptible to natural impacts such as thermally induced coral bleaching and cyclone damage and associated mortality, as demonstrated by past recent disturbances (Gilmour and Smith 2006; Gilmour et al. 2009a). Worst-case: With a 19.5 cm increase in MSL (7.1 cm due to subsidence), there is potential for increased wave action to occur, however, it is unlikely that increased wave exposure due to 19.5 cm rise in MSL would adversely impact shallow water corals on its own. Any significant impacts to shallow water corals will arise due to cyclone, bleaching and ocean acidification effects, which, under this scenario, are assumed to have the potential to occur regardless of 7.1 cm of subsidence. For instance, due to their destructive capacity, cyclones can reshape reef structures (Done 1992; Fabricius et al. 2008) and have the potential to cause a shift from a community dominated by mechanically vulnerable corals (e.g. branching, digitate, tabular and foliaceous corals) to ones dominated by robust forms (Guillemot et al. 2010). Any impacts associated with cyclone damage and climate change related effects would be expected to occur regardless of 7.1 cm of subsidence. In the worst-case scenario, the impact to shallow water coral habitat corals contributed by production-induced subsidence is assessed as negligible. Intermediate-case: A 7.8 cm increase in MSL (4.4 cm due to subsidence would equate to a 1 to 3% change compared to the total present day sea level range. This magnitude of change is not expected to result in a change in hydrodynamic or light conditions affecting reef morphology or community composition and structure. In the intermediate-case scenario, impacts on the shallow-water reef slope communities are expected to be negligible. Best-case: With a 4.7 cm net decrease in MSL (2.1 cm increase due to subsidence), alterations to hydrodynamic conditions at Scott Reef would be negligible. Conditions influencing the development of coral reef morphology, community composition and structure would remain unchanged. In the best case scenario, impacts due to subsidence are assessed as negligible. Deep-water Coral Deepwater coral habitats at Scott Reef, including sheltered deep water coral assemblage habitat, have not been susceptible to thermally induced bleaching and cyclone damage (Section 6.3.2). Worst-case: With a 19.5 cm increase in MSL (7.1 cm due to subsidence), overall impacts to deep water coral habitats are predicted to be negligible. Deepwater corals can photoacclimatise to changes in light conditions over short time scales by changing the density of zooxanthellae and/or changing the concentration of photosynthetic pigments. Given the gradual nature of the subsidence over 40 years, corals would be able to photo-acclimatise. The change in irradiance due to subsidence would be within the range of natural variability from, for example, changing cloud cover leading to fluctuations in irradiance levels. Intermediate-case: With a 7.8 cm increase in MSL (4.4 cm due to subsidence), impacts to deep water corals are not expected. Changes in irradiance would have negligible effects on the photo-physiology of corals. Best-case: With a 4.7 cm net decrease in MSL (2.1 cm increase due to subsidence), impacts to deepwater corals are not expected. Sandy Islet Sandy Islet is an unvegetated, 4.5 m high, linear-shaped sandy cay with a sandy spit at its southern end, serving as an important turtle nesting ground (Section 6.3.6) and also used for roosting by seabirds (Section 6.3.7). Based on comparison of aerial photographs, Sandy Islet has not experienced significant shift in its current position for at least the past 30 years, aided by rock outcrops along its eastern edge. The largest shifts in position over time have occurred at it southern end, while the position of its central core has not changed. In 2004, Sandy Islet was completely submerged by waves from Category five Cyclone Fay, which washed about one third of it away (AIMS 2008). Worst-case: Under this scenario, the reduced coral accretion rates due to climate change related effects would reduce the amount of carbonate material (i.e. coral-derived sand and rubble) in the sediment budget that is delivered to the cay from the surrounding reef flat. With a 19.5 cm increase in MSL (7.1 cm due to subsidence), there is potential for wave action at high tide to reduce the height of the cay. This could affect the stability of Sandy Islet due to erosional processes associated with increased wave height, and thus impacts to availability of turtle nesting habitat. A higher frequency of Category five cyclones (one every three to five years) coupled with decreased sediment budget, would mean less time for Sandy Islet to recover between intense cyclones to the extent that recovery would be unlikely. These impacts would still occur in the absence of subsidence albeit over a slightly longer time period, with the most important factor influencing the persistence of the Islet being the frequency of Category five cyclones. Given the highly variable nature of sea level rise, cyclone occurrence and sediment dynamics it is not possible to reliably predict the timing or just how much earlier any major changes to Sandy Islet might occur. Intermediate-case: With a 7.8 cm increase in MSL (4.4 cm due to subsidence), the increase in coral growth on the reef flat would be expected to increase the availability of CaCO 3 input into the sediment budget. As sea level increases, sediment movement on the reef flat may become more efficient and the height of the beach berm may increase more than the sea level increase. The 4.4 cm increase in sea level due to subsidence is assessed as a negligible impact. Best-case: With a 4.7 cm net decrease in MSL (2.1 cm increase due to subsidence), reef flat growth may contribute a small amount of extra sediment to the sediment budget, but no increase in the effectiveness in sediment transportation would occur. Sandy Islet would not be affected under the best case scenario such that impacts due to 2.1 cm subsidence are negligible.

23 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 181 The assessment undertaken by AIMS (Cooper et al. 2010; AIMS 2012b) concluded that minor seabed subsidence over the life of the Torosa reservoir affecting a part of Scott Reef and Sandy Islet is not predicted to significantly contribute to sea level changes and predicted associated impacts. The main consequence of the addition of subsidence to climate change-induced sea level rise for all scenarios would be that potential impacts would be brought forward in time. Under all climate change scenarios where a net increase in sea level is predicted, impacts due to sea level rise are forecast to occur at Scott Reef and Sandy Islet regardless of production-induced subsidence. At the end of project life, any subsidence effects will cease, while any climate change influenced effects on sea level can be expected to continue to occur. Based on the assumption that the overall elevation of Sandy Islet is 4.5 m, and the most up to date predictions of sea level rise (IPCC 2013) and subsidence (Woodside 2014), the following observations can be made: For the best-case scenario where sea level rise is lowest (3 mm/yr resulting from climate change), it would likely take approximately 1,500 years for the water depth to increase by 4.5 m in the absence of subsidence. Factoring in subsidence at a rate of 0.6 mm/year over 40 years, it would take approximately 1,492 years to increase by 4.5 m. For the worst-case scenario, (11.4 mm/yr resulting from climate change) it would likely take approximately 395 years for the water depth to increase by 4.5 m in the absence of subsidence. Factoring in subsidence at a rate of 2.2 mm/yr over 40 years, it would take approximately 387 years to increase by 4.5 m. The risk of environmental impact from subsidence resulting from the Browse FLNG Development is therefore assessed to be low Artificial Light As various components of and activities associated with the Browse FLNG Development require lighting for operational and safety reasons, light emissions will occur from FLNG facilities, drill rig and vessels during all phases of the development. The amount of light emitted varies based on a number of factors, including the location and/or placement of light fittings, intensity of the light source and light wavelength. Artificial light has the potential to disrupt biological processes that rely on natural light for visual cues. Marine fauna that are known to be either reliant on light for ecological functions or have a sensitivity to light include marine turtles, birds, fish, plankton and corals. This section discusses the potential impacts of light emissions on these sensitive receptors identified within or adjacent to the Browse FLNG Development. Light Sources and Characteristics Light emissions will be generated from two main sources: Navigational and operational lighting. Flaring. The source and duration of lighting for each phase of the Browse FLNG Development are summarised in Table 10.4 and described in Section Green turtles in the vicinity of Scott Reef, in particular nesting female green turtles at Sandy Islet, have been identified as the main ecological receptor to light emissions associated with the Browse FLNG Development. To further understand the effects of light emissions on green turtles, a line of sight assessment and a light density (luminous flux density) modelling study were conducted for the following activities, identified in Section to provide the largest contributions to light emissions: Lighting on the drill rig during drilling activities at the TRE drill centre (ERM 2010). Lighting on the FLNG facilities at Torosa, Brecknock and Calliance (Jacobs-SKM 2014). Light emissions from vessels associated with the development has not been included in the line of sight assessment and light density modelling due to the temporary and transient nature of vessel movements. Table 10.4: Source and Duration of Lighting for each Phase of the Browse FLNG Development Drill rig Activity Source FLNG facilities Vessels Drill rig FLNG facilities Type Functional and navigation lighting Functional and navigation lighting Functional and navigation lighting Flaring Duration Short term (approximately two to three months per well) Long term over life of project Long term (intermittent and transient) Continuous pilot flare (2 m flare tip length) and intermittent controlled and emergency flaring Installation & Commissioning Operation Decommissioning

24 182 Browse FLNG Development Draft Environmental Impact Statement Line of Sight Assessment Methods A line of sight assessment was undertaken to determine the maximum distance that light associated with the above activities may be visible (irrespective of the light source intensity). The maximum line of sight is based on the following: The location and height above sea level of the light source. The height above sea level of the viewing location. The distance between the light source and the viewing location. The curvature of the earth s surface. The line of sight assessment was undertaken using a Line of Sight Calculator (Kagstrom 2005) for the TRE drill rig (ERM 2010) and using Esri ArcMap viewshed analysis for the FLNG facilities (Jacobs-SKM 2014). Results A summary of the line of sight assessment results are presented in Table The line of sight assessment undertaken for the drill rig at the TRE drill centre (ERM 2010) (Figure 10.1) showed that the maximum distance that direct light may be visible extended up to: 16.6 km for main deck lights. 21 km for drill floor lights km for derrick lights km for a continuous 2 m high purge flare km for an intermittent emergency flare (indicative initial flame length of 50 m). Due to the proximity of the TRE drill centre from Scott Reef, it was therefore predicted that direct light emitted from a drill rig at this location will be visible to some extent from all areas of Scott Reef (Figure 10.1). The appearance of this visible light in terms of its size and intensity is assessed in Section The maximum distance at which direct light may be visible from any of the FLNG facilities under routine operational conditions (Jacobs-SKM 2014) (Figure 10.2) was predicted as follows: 18.8 km for deck lighting km for topside modules/cranes lighting km for the flare. In the event of emergency flaring, it is possible that light may be visible up to ten kilometres further than during normal operating conditions. Any such emergency flaring would be of a shortterm duration and therefore not assessed further. The line of sight assessment indicated that direct lights from FLNG facilities at the Torosa FLNG locations (BWB-TR and BWC) would be visible to some extent from portions or all of Scott Reef, depending on the location of the FLNG facility (Figure 10.2). Deck lights were predicted to be visible from most of North Scott Reef and from a small portion to the east of South Scott Reef, but not from Sandy Islet. Direct light emitted from the topside modules/cranes will be visible from most of North and South Scott Reef, including Sandy Islet, while light emitted by either flare was predicted to be directly visible from any location at Scott Reef. Direct light sources from FLNG facilities at Brecknock and Calliance (i.e. BWA and BWB) were not predicted to be visible from Scott Reef, with the exception of the flare at the BWA location. The flare at the BWA location was estimated to be visible from a portion of South Scott Reef, but not from Sandy Islet (Figure 10.2). Operational lighting from the Brecknock and Calliance FLNG facilities was therefore not considered for further assessment. Table 10.5: Summary of Line of Sight Assessment Location Direct light source Visibility TRE drill centre Drill rig All of Scott Reef FLNG facilities at Torosa Deck Topside modules/cranes Most of North Scott Reef and small portion to the east of South Scott Reef only Most of North and South Scott Reef including Sandy Islet Flare All of Scott Reef FLNG facility at Brecknock Flare Visible from parts of South Scott Reef only FLNG facility at Calliance All Not visible from Scott Reef

25 Figure 10.1: Line of Sight Assessment for a Drill Rig at the TRE Drill Centre (ERM 2010) Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 183

26 184 Browse FLNG Development Draft Environmental Impact Statement Figure 10.2: Line of Sight Assessment for FLNG Facilities at the BWA, BWB, BWC and BWB-TR Locations (Jacobs-SKM 2014)

27 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE Light Density Modelling Light density represents the intensity of light that arrives at or leaves a surface, as perceived by the human eye, and it is measured in Lux. The total amount of light as it arrives at a surface is referred to as illuminance, and is the parameter that has been modelled. Light density decreases as distance increases from the source of light. Table 10.6 presents background light density measurements, including night time levels which range from Lux on a moonless overcast night, to 0.1 Lux on a full moon night. These levels are consistent with a baseline survey of light density, undertaken at Scott Reef during a new moon to determine the darkest natural conditions, which resulted in light density ranging between 0.00 and 0.01 Lux (ERM and SKM 2008). The lux levels in Table 10.6 have therefore been deemed representative of light density conditions in the Development area and have been used to represent the range of background light density levels under variable natural conditions for this assessment. Scope and Methods Drill Rig at TRE drill Centre Light density levels representing a drill rig at the TRE drill centre were predicted by using light density data measured during the drilling of the Torosa South-1 well, located on the edge of the South Scott Reef lagoon (ERM and SKM 2008; ERM 2010) (Figure 10.3). Although the rig type for development drilling is yet to be confirmed, light levels are expected to be comparable. The light density from the Torosa South-1 drill rig was highest (8.9 Lux) at 100 m from the rig and lowest (0 to 0.03 Lux) at the extremities of the survey area, approximately 1.4 km from the drill rig (Figure 10.4) (ERM and SKM 2008). Light density attenuated to below 0.1 Lux between 1 and 1.4 km from the drill rig. FLNG Facilities at Torosa Light density modelling for the FLNG facilities at Torosa was based on a surface area of 20,500 m² being illuminated to an average level of 200 Lux based on current design criteria. In the modelled scenario, the broad side of the FLNG facilities was assumed to face Scott Reef at an angle of 90 degrees, which represents a worst case scenario for exposure to light. As described in Section 5.2.3, the facilities will freely weathervane around turret moorings and their actual position will reflect prevailing wind and current conditions. Modelling results were verified against light intensity measurements obtained from the Torosa South-1 drill rig. In addition to routine operational lighting from the FLNG facilities, light emissions from the flare were expected to be visible from Scott Reef based on the results of the line of sight assessment. Measurements on the light emitted from the drill rig at Torosa South-1 indicated that peak wavelengths emitted from the drill rig ranged between 530 to 620 nm, which is within the range that is visible to marine turtles (Figure 10.3) (ERM and SKM 2008). These wavelengths are expected to be comparable to those from routine light emissions from the drill rig and the FLNG facilities. Natural gas flares have been measured to have a peak spectral signature in the invisible infrared range (750 to 900 nm), with lower levels of light emitted in the range visible to turtles (Hick 1995 in Pendoley 2000). Flaring would only occur intermittently at the FLNG facilities during commissioning and shut down or upset conditions, with light emissions varying in duration and intensity. Light emissions from the flare, due to the distance of the FLNG facilities from Sandy Islet, would be expected to have limited influence in comparison to those associated with operational lighting. Light emissions associated with flaring were therefore not considered for further assessment. Table 10.6: Typical Light Density Levels (Micron Technology 2007) Light Type Light Density (Lux) Direct sunlight 100,000 to 130,000 Full daylight, indirect sunlight 10,000 to 20,000 Overcast day 1,000 Very dark day 100 Twilight 10 Deep twilight 1 Full moon 0.1 Quarter moon 0.01 Moonless clear night sky Moonless overcast night sky

28 186 Browse FLNG Development Draft Environmental Impact Statement Figure 10.3: Spectral Signature of Drill Rig Located at Scott Reef Results Drill Rig at TRE Drill Centre Modelling of light density levels for a drill rig at the TRE drill centre (Figure 10.5) predicted levels greater than 0.1 Lux up to 800 m from the rig, which is comparable to ambient light levels during full moon to twilight (ERM 2010). Between 800 m and 1.2 km from the drill rig, the model predicted light density levels comparable to ambient light levels during a quarter moon to full moon night sky (0.01 Lux to 0.1 Lux). Between 1.2 km and 12.6 km, light density levels were predicted to be lower than 0.01 Lux, which is comparable to ambient light density levels between a moonless clear night sky and a quarter moon. Beyond 12.6 km there was no measurable change to the background light density levels predicted. Based on these modelling results, the maximum predicted light density levels from a drill rig at either location reaching Sandy Islet are lower than 0.01 Lux (comparable to light levels between a moonless clear night sky and a quarter moon) (Figure 10.5). FLNG Facilities at Torosa Modelled light density levels from each FLNG facility at Torosa were predicted to be: 5 to 25 Lux out to approximately 1 km (comparable to levels between deep twilight and a very dark day). 2.5 to 5.0 Lux between approximately 1 and 1.5 km (comparable to levels at twilight). 0.5 to 2.5 Lux between approximately 1.5 and 2 km (comparable to levels between a full moon and twilight) to 0.5 Lux between approximately 2 km and 3 km (comparable to levels between a full moon and deep twilight) to 0.25 Lux between approximately 3 km and 7 km (comparable to levels between a quarter moon and deep twilight) to 0.05 Lux between approximately 7 km and 10 km (comparable to levels between a quarter moon and a full moon). Less than Lux beyond approximately 33 km (comparable to a moonless clear to overcast night sky) (Jacobs-SKM 2014).

29 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 187 For a single FLNG facility operating at the BWC or BWB-TR locations, brightness levels are expected to attenuate to less than 0.1 Lux (comparable to a full moon) within approximately 5 km of the FLNG facility (Table 10.7). The combined lighting of two FLNG facilities operating concurrently at the BWC and BWB-TR locations is predicted to generally result in slightly higher light levels in the surrounding environment. For example, the level of brightness at Sandy Islet would increase from approximately Lux for a single facility to Lux for two concurrently operating facilities (Figure 10.6). However, the overall values remain low; being less than 0.01 Lux. Brightness levels from the two facilities are also expected to remain low at Scott Reef, with levels predicted to attenuate to less than 0.1 Lux approximately 2.5 km from North Scott Reef (Figure 10.6 and Table 10.7). Therefore, for both single and concurrently operating FLNG facilities, brightness levels above the brightest natural light source at night (a full moon) are not expected to reach Scott Reef or Sandy Islet. Any lighting from FLNG facilities at the Brecknock and Calliance locations that is within line of sight of Scott Reef (i.e. the BWA FLNG flare) will not be discernable from background light levels. Results of light density modelling for the FLNG facilities are presented in Figure Table 10.7: Light Density Levels Predicted at Scott Reef and Sandy Islet (Jacobs-SKM 2014) FLNG Locations North Scott Reef South Scott Reef Sandy Islet Lux Levels Lux Levels Lux Levels Torosa BWB-TR < <0.005 Torosa BWC < < <0.005 Torosa BWB-TR and BWC <

30 188 Browse FLNG Development Draft Environmental Impact Statement Figure 10.4: Lux levels from the Torosa South-1 Drill Rig at South Lagoon, Scott Reef (ERM and SKM 2008)

31 Figure 10.5: Modelled Lux Levels from a Drill Rig at the TRE Drill Centre (ERM 2010) Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 189

32 190 Browse FLNG Development Draft Environmental Impact Statement Figure 10.6: Modelled Combined Light Density Levels from FLNG Facilities at the BWC and BWB-TR Locations (Jacobs-SKM 2014)

33 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE Impact Assessment Marine fauna that use visual cues for orientation, navigation, or other purposes may be disrupted by artificial light sources. Potential impacts to marine fauna from artificial lighting associated with the Browse FLNG Development include: Disorientation, attraction or repulsion. Disruption to natural behavioural patterns and cycles. The effects on marine fauna from artificial lighting are dependent on: Density and wavelength of the light and the extent to which light spills into areas that are significant for breeding and foraging. Timing of light spill relative to breeding and foraging activity. Resilience of the fauna populations that are affected. Marine Turtles Exposure of marine turtles to artificial light can result in changes to their natural behaviour. Witherington and Martin (2003) state that light pollution on nesting beaches is detrimental to marine turtles because it alters critical nocturnal behaviours, namely, how turtles choose nesting sites, how they return to the sea after nesting, and how hatchlings find the sea after emerging from their nests. Turtles do not perceive light in the same way as humans and are sensitive to the types of light commonly used for illumination purposes (Pendoley 2005). Research suggests that marine turtles are most sensitive to short-wavelength light in the near-ultraviolet to yellow region of the visible spectrum, from approximately 340 to 700 nm (Figure 10.3) (Witherington and Martin 2003). Marine turtle hatchlings commonly show a greater spectral sensitivity within the violet and blue region of the spectrum and are typically more sensitive to wavelengths in the range of 300 to 500 nm (Witherington 1997; Witherington and Martin 1992, 2003). Artificial lighting associated with the Browse FLNG Development will be within the visible range for marine turtles, with the spectral signature of light emissions from the drill rig at Torosa South-1 measured to be between 530 to 620 nm. Based on lighting data from the drill rig, approximately 60% of the light wavelength transmission is within the sensitive wavelength range for turtle hatchlings (300 to 500 nm) (ERM 2010), with most common artificial light sources, such as fluorescent, generating light within these wavelengths (Witherington 1997; Witherington and Martin 2003). Adult marine turtles typically require a dark location to lay eggs, although nesting populations of marine turtles have been known to continue to nest despite the introduction of artificial light (e.g. at Varanus Island and Barrow Island) (Pendoley 2005). Turtles predominately nest at Sandy Islet between November and February, and internesting turtles have been observed to aggregate primarily in an area to the south and west of Sandy Islet (Section ). Based on modelling results described above (ERM 2010; Jacobs-SKM 2014), maximum predicted direct light levels reaching Sandy Islet are less than 0.01 Lux from the TRE drill rig or Torosa FLNG facilities, with light appearing as a small lit object. No disturbance to the nesting behaviour of adult marine turtles is therefore expected from direct light visible at Sandy Islet. Adult turtles passing through the Development area may temporarily alter their normal behaviour whilst attracted to the light spill from infrastructure. Light spill of at least 0.01 Lux (i.e. at least quarter moon levels) is likely to extend 1.2 km radially from the drill rig and 15 km radially from FLNG facilities. Given the wide migratory distribution (i.e. several hundred kilometres) of adult turtles outside of nesting season and their low density presence within the Development area, the zone of influence and subsequent attraction from direct lighting is expected to be minor and a temporary disruption to a small portion of the adult turtle population. Hatchlings differ to adults in that they primarily use light as a cue to locate the ocean (Limpus 2006 in: EPA 2006). Disoriented hatchlings may perish from exhaustion, dehydration, or predation. Light levels at Sandy Islet from the drill rig or FLNG facilities are predicted to be less than 0.01 Lux, which is comparable to the light level between a moonless clear night sky and a quarter moon. At this level, light is not expected to be sufficient to alter hatchling behaviour leaving the nesting site on Sandy Islet. Any attraction of turtle hatchlings from Sandy Islet to the infrastructure would not interrupt their seaward movement as Sandy Islet is a small, low-lying sandy cay with nearby access to the water from all directions. It is noted that the drill rig at TRE, the nearest light source to Sandy Islet, will only be in that location for one or two nesting seasons. Spectral analysis of flares on Thevenard Island on the North West Shelf (Pendoley 2000) suggests that flare light does not contain a high proportion of light wavelengths within the range that is most disruptive to turtle hatchlings (300 to 500 nm). The nearest flaring light source to Sandy Islet, the drill rig at the TRE drill centre, will be approximately 7 km away and only in that location for one or two nesting seasons. The duration of controlled flaring at the drill rig typically lasts 12 hours per well. The FLNG facilities will have a continuous low volume pilot flare to maintain a flame at the flare tip. Each FLNG facility is designed such that there are no other continuous flaring sources. Flaring may occur during emergency situations however, the FLNG facilities will be located a minimum of 27 km from Sandy Islet. No disturbance to hatchling turtles from flaring is therefore expected. Once in the ocean, little is known of the extent to which hatchlings still use vision over wave direction and the earth s magnetic field (Lohmann 1992) for orientation. Consequently, it is not possible to draw conclusions regarding the impact of artificial light on their behaviour after this point. The attraction of turtle hatchlings to infrastructure could cause them to linger in an area with a higher concentration of predators that have also been attracted by the light. However, it is thought that the vision of hatchling turtles is limited in the water and that other more dominant navigational cues take over (Lohmann and Lohmann 1992; Amos 2014). A recent pilot study supported by Woodside that used acoustic telemetry to track hatchling dispersion in relation to artificial light sources at Eco Beach, WA, found that at least in the surf zone, artificial lights did not affect movement, with the hatchlings largely travelling against the direction of wave propagation (Thums et al. 2012).

34 192 Browse FLNG Development Draft Environmental Impact Statement Based on the modelling results, the TRE drill rig is the only infrastructure at a close enough distance to Sandy Islet to create sufficient light levels for potential attraction. Given that the rig will be located 7 km from Sandy Islet, attraction is considered unlikely. However, should attraction towards the direction of the drill rig occur, the fact that surface currents in the channel where the drill rig will be located are strong (averaging approximately 0.5 knots with current speeds up to and exceeding two knots depending on tidal conditions), means that conditions would not be conducive for hatchlings to linger in the vicinity of the rig should they reach it. It is anticipated that on reaching the channel, hatchlings would disperse rapidly with the current. There is extensive evidence that when hatchlings disperse offshore, sea surface currents have considerable effects on the dispersal process (Frick 1976; Salmon and Wykenen 1987; Liew and Chan 1995; Witherington 1995; Okuyama et al. 2009). Strong currents have been observed to affect the course of hatchling dispersion during the initial 24 hour swimming frenzy, and currents may be expected to have an even more significant influence as swimming activity later declines in duration and vigour. No significant impacts to hatchlings from artificial light associated with drilling activities are therefore anticipated. Birds Light from the drill rig and FLNG facilities are unlikely to attract a significant number of seabirds or shorebirds as activities are located a considerable distance from known key aggregation areas, such as Ashmore Reef (230 km), Roebuck Bay (370 km) and Eighty Mile Beach (500 km). Migratory birds that use the EAAF may fly over, or in the vicinity of, the FLNG facilities. Migratory birds are occasionally observed in very low numbers at Scott Reef, and Sandy Islet may be used as a resting point during the migration between the Northern Hemisphere and Australia. However, given its small size, Sandy Islet is not capable of supporting large numbers of individuals. There is little information available regarding how migratory birds navigate. However, many migratory birds are thought to use the earth s magnetic field, stars, the sun and polarised light patterns to determine their migratory direction (Weindler and Liepa 1999). Therefore, with migratory birds dependent on visual cues, artificial light may alter natural migratory patterns, specifically in the absence of terrestrial landmarks. Light from offshore facilities has been shown to attract migrating birds, with bird species that migrate during the night more likely to be affected (Verhejen 1985). Birds may either be attracted by the light source itself or indirectly as lighted structures in marine environments tend to attract marine life at all trophic levels, creating food sources and shelter for seabirds. Furthermore, sources of artificial light may provide enhanced capability for sea birds to forage at night. Artificial lighting may interfere with a bird s internal magnetic compass. Migratory birds require light from the blue-green part of the spectrum for magnetic compass orientation (Muheim et al. 2002; Wiltschko and Wiltschko 1995, 2001) whereas red light, the long-wavelength component of light, is more likely to disrupt magnetic compass orientation. As the measured spectral signature of light emissions from the drill rig at Torosa South-1 was between 530 to 620 nm, and the red part of the spectrum is outside of these ranges, it can be assumed that bird species magnetic compass orientation will not be disrupted. Studies in the North Sea indicate that migratory birds may be attracted to lights on offshore platforms when travelling within a radius of 3 to 5 km from the light source. Outside this area their migratory paths are likely to be unaffected (Marquenie et al. 2008). Given that a relatively small number of transiting individuals are expected to pass in the vicinity of the drill rig, the FLNG facilities and supporting vessels associated with the Browse FLNG Development, any behavioural effects such as disorientation and attraction are expected to be minor. Birds roosting at night on Sandy Islet are unlikely to be disturbed given the low level of artificial light (less than 0.01 Lux) that would be received at Sandy Islet from any permanent or temporary infrastructure in the area. Fish Numerous fish species inhabit the Development area and some may be attracted to offshore light sources. The whale shark (Rhincodon typus) is the only threatened fish species that has the potential to occur within the Development area and impacts from light emissions are not documented for this species (Commonwealth of Australia 2012). The response of fish to light emissions has been shown to differ depending on species and habit. Artificial lighting can change ambient light regimes and pose risks of increased mortality through changes to natural night time distribution and consequently alter predator and prey relationships (Marchesan et al. 2006; Nightingale and Simenstad 2001). The change in behaviour may benefit predatory fish species while other species will become more at risk of predation in areas of light spill. Artificial light may also exclude nocturnal foragers/predators from an area, allowing diurnal species to benefit from increased access to resources. The potential disturbance to fish from drill rig, vessel and FLNG facility light emissions is expected to be restricted to localised attraction. Any impacts to fish arising from light emissions are considered to be minor and highly localised to a small proportion of the populations. Plankton Zooplankton are light-dependent species displaying diurnal vertical movements (Leach and Johnsen 2003) migrating near the water surface at night to feed. Artificial light has therefore the potential to reduce the amplitude of their migration if lighting levels are sufficiently high at night (Moore et al 2000). Artificial light emissions from the FLNG facilities, drill rig and vessels could influence the migration of zooplankton from deep water to the surface, thereby affecting food supply of nocturnal plankton-feeders. Alternatively, illumination of marine waters in close proximity to facilities could provide increased feeding opportunities for predators. However, these effects are expected to be highly localised.

35 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 193 Corals Corals are susceptible to slight changes in the surrounding coral reef environment which are capable of producing adverse effects on the health of entire coral colonies (Aubrecht et al. 2008). The nearest coral habitat to the Browse FLNG Development is within Scott Reef. The environmental factors that provide cues for corals to synchronise reproductive cycles are likely to include sea temperature, lunar tidal or nocturnal moonlight cycles, and daily light/dark cycles (Harrison and Wallace 1990). Most coral species synchronise their spawning through detection of low light intensity (Aubrecht et al. 2008). As corals are able to detect illumination in the ranges caused by the moon, they are often sensitive to minor increases in nocturnal illumination, particularly in shorter wavelengths (Gorbunov & Falkowski 2002). Broadcast spawning corals at Scott Reef undergo two short and distinct periods of mass spawning which occur in spring and autumn, with autumn being the dominant spawning period (Gilmour et al. 2009a, 2009b, 2010). The nights of coral spawning at Scott Reef typically occur following a full moon and during neap tides (Gilmour et al. 2013). Light levels from drilling within the channel that reach Scott Reef are estimated to be less than 0.01 Lux (Figure 10.5) which is equivalent to a quarter moon. Light levels from the Torosa FLNG facilities are estimated to be less than 0.1 Lux (equivalent to a full moon) from the majority of Scott Reef. Only a limited portion of the eastern side of North Scott Reef is predicted to receive light levels up to 0.25 Lux, comparable to levels corresponding to a deep twilight. However these light levels would only occur at the sea surface, and as light reaching the surface near the reef will be at a low angle due to distance from facilities, a considerable portion of the light will be reflected rather than penetrate the water column (Saha 2008). Light that does penetrate the water column will be attenuated rapidly with depth, further reducing the potential for impact to coral communities. The ocean absorbs light much more rapidly than air. Blue light (less than 500 nm) penetrates furthest into seawater, while red, orange, and yellow wavelengths (greater than 550 nm) are removed through absorption (Talley et al. 2011). Peak light wavelengths emitted from the drill rig and FLNG facilities are expected to be greater than 530 nm and will be absorbed at shallow depths. Coral habitat that will be exposed to the highest levels of light will therefore be the reef flat (1 to 4 m depth), which has a low coral cover of less than 5% (Section 6.3.2). In summary, with the implementation of the management and mitigation measures detailed in Section 9.2.4, the overall level of risk associated with the lighting proposed for the development is assessed to be low Underwater Noise This section assesses the potential impacts of underwater noise from the Browse FLNG Development to identified sensitive receptors. Noise propagation underwater is influenced by a number of factors including depth, seabed substrate and the temperature and salinity of the water column. Browse FLNG Development activities that may result underwater noise emissions include: Drilling, installation and commissioning activities: Drilling. Well evaluation using VSP. Seabed preparation for Torosa flowlines. Vessel operations (propulsion, positioning and machinery). Operational activities: Subsea infrastructure operation (e.g. choke valves at subsea wellheads). FLNG facility routine operation. Condensate tanker or LNG carrier and FLNG facility (using thrusters) during produced hydrocarbon offloading. Vessel operations (propulsion, positioning and machinery). Suction piling is the preferred method for installing piles to secure the mooring lines for the FLNG facilities or any other piles for the supporting infrastructure or drill rig mooring lines. As such, a full assessment of driven piling alternatives has not been undertaken at this time. Should geotechnical investigations of the seabed at Torosa indicate that driven piling will be required, Woodside will conduct a thorough impact assessment and develop and implement noise management procedures as required. These will be detailed in the relevant EPs for submission and acceptance by the relevant regulatory authority. Indicative noise levels for key development activities are summarised in Table Increased noise emissions are expected during installation and commissioning due to the higher number of vessel movements and activities. However, this phase will be of short duration compared to the life of the project. Noise associated with decommissioning is expected to result primarily from the operation of the vessels required to decommission the facilities and remove infrastructure. Noise impacts are thus anticipated to be similar to those during installation and commissioning activities. Levels of noise associated with Browse FLNG Development activities that are audible to a marine receptor (received level) will depend on the following: Background (ambient) noise. Noise level generated by an activity at the source (source level). The spectral characteristics of the noise (frequency). The distance the marine receptor is from the noise source (range). The level of transmission loss between the noise source and the receptor. The hearing threshold and frequency sensitivity of the receptor. Underwater noise modelling has been conducted for the FLNG facilities and subsea wellheads to predict received levels due to the longer duration of noise emissions from these sources during the operational phase of the development. Details of the modelling are provided in Section

36 194 Browse FLNG Development Draft Environmental Impact Statement Table 10.8: Indicative Noise Levels for Key Development Activities Activity Indicative Noise Levels (db re 1 μpa) References Drilling 157 to 162 at 1 m (RMS) Hannay et al. 2004; McCauley 1998, 2003 Vertical seismic profiling 238 at 1 m and less than 180 within 100 m (zero to peak) Matthews 2012 Vessels 164 to 182 at 1 m (RMS) McCauley 2008; Blackwell and Green 2002; MacGillivray and Racca 2006; Austin 2004; Zykov and Hannay 2006 Wellheads 159 at 1 m and less than 120 at 500 m (RMS) McCauley 2002 Seabed trenching 178 at 1 m (RMS) Nedwell et al Helicopters 101 to 109 at 3 m water depth for altitudes of 610 to 152 m respectively Richardson et al FLNG facility during normal 192 to 201 at 1 m (RMS) (based on mean and maximum operations operational noise). Below 160 within approximately 100 m Duncan 2014 FLNG facility thrusters (two thrusters with a combined power of 10 MW) 189 (RMS) Duncan 2014 FLNG facility during offloading activities (combined facility noise and thrusters) Below 180 within 20 m, 165 within 100 m and 120 at 5 to 10 km (RMS) (based on mean and maximum operational noise) Duncan Modelling Results FLNG Facilities Modelling was completed for the production and propagation of underwater noise associated with the proposed FLNG facilities at the Brecknock, Calliance and Torosa reservoirs (i.e. BWA, BWB, BWC and BWB-TR locations) (Duncan 2014). Estimation of the source levels for the FLNG facilities (Section 5.9.2) indicates there would be an approximate 10 db difference between mean and maximum noise levels from the facilities during normal operations. Addition of thruster noise during offloading operations increases predicted noise above mean FLNG operational noise by several db, but only marginally increases it above maximum FLNG operational noise. As stated in Section 5, thrusters on the FLNG facilities would only be used during offloading activities to maintain heading, and this is anticipated to only occur approximately 10 to 20% of the time. A number of different scenarios were modelled involving FLNG facility noise during normal operating conditions and during offloading of LNG with an LNG carrier and support vessels alongside. Underwater noise from individual FLNG facilities modelled at the Brecknock (BWA) and Torosa (BWC) locations is predicted to attenuate rapidly in close proximity to the facilities (Figure 10.7) (Duncan 2014). For some proportion of the reservoir life, two FLNG facilities are expected to operate concurrently at Brecknock (BWA) and Calliance (BWB), and two facilities concurrently at Torosa (BWC and BWB-TR). Figure 10.8 and Figure 10.9 illustrate the modelled noise levels of the two Brecknock and Calliance facilities and two Torosa facilities respectively. The noise contours represent both normal operating conditions and offloading activities at both concurrent facilities. Distances of noise propagation from each FLNG facility are predicted to be similar to those from the single facilities modelled, with little cumulative effect from the operation of two facilities in relative proximity. The modelling results show that underwater noise levels from the single and concurrent FLNG facilities at Brecknock and Calliance are likely to be close to background levels in the vicinity of Scott Reef, both during normal operations and during LNG offloading activities under mean and maximum operational noise conditions (Figure 10.7 and Figure 10.8). Underwater noise from the single and concurrent FLNG facilities at Torosa during normal operations is predicted to drop below 120 db re 1 μpa approximately 4 km from the FLNG facilities under mean operational noise conditions. During LNG offloading activities, noise levels of 120 db re 1 μpa are predicted to extend to approximately 10 km away under mean operational noise conditions. Under maximum operational noise conditions, noise levels are predicted to drop below 130 db re 1 μpa approximately 5 km from the FLNG facilities and below 120 db re 1 μpa approximately 14 km away during both normal operations and offloading activities.

37 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 195 Figure 10.7: Mean and Maximum Received Noise Levels (Left and Right Respectively) from the Brecknock BWA FLNG Facility (Top) and Torosa BWC FLNG Facility (Bottom) During Normal Operations. Contours Represent Maximum Received Sound Pressure Levels at Any Depth for a Given Location

38 196 Browse FLNG Development Draft Environmental Impact Statement Figure 10.8: Mean and Maximum Received Noise Levels (Left and Right Respectively) from the Brecknock BWA and Calliance BWB FLNG Facilities During Normal Operations (Top) and Offloading (Bottom). Contours Represent Maximum Received Sound Pressure Levels at Any Depth for a Given Location

39 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 197 Figure 10.9: Mean and Maximum Received Noise Levels (Left and Right Respectively) from the Torosa BWC and BWB- TR FLNG Facilities During Normal Operations (Top) and Offloading (Bottom). Contours Represent Maximum Received Sound Pressure Levels at Any Depth for a Given Location

40 198 Browse FLNG Development Draft Environmental Impact Statement Subsea Wellheads Underwater noise from subsea wellheads was modelled to determine the geographical range over which noise from the Browse subsea wellheads might be expected to occur (Duncan 2010). The source level recorded by McCauley (2002) from an oil producing wellhead associated with the Cossack Pioneer FPSO was used in the modelling (refer to Section 5.9.2). Modelling was conducted for the subsea wellheads located at the western (TRE) and eastern (TRD) drill centres in the channel between North Scot Reef and South Scott Reef (Figure 10.10). The modelling was based on configurations of seven wellheads at the TRD drill centre and six wellheads at the TRE drill centre, spaced 20 to 40 m apart and 4.5 m above the seabed in a water depth of approximately 400 m. Received levels were calculated for cross-sections of the channel at the TRD and TRE drill centres (Figure 10.11), using two complimentary methods, the image method and the parabolic equation method (Duncan 2010). Results obtained using the two different methods were broadly consistent. However, the image method provided more accurate results close to and above the source, whereas the parabolic equation method provided the best results towards the edges of the channel where refraction becomes important (Figure 10.11). The modelling indicates that noise levels will fall below 120 db re 1 μpa within approximately 500 m of the wellheads and are not expected to propagate more than 1 km under optimal conditions. It is noted that the operating state of the Cossack Pioneer FPSO wellhead was not known at the time of measurement. However, in the absence of measured data at the Browse reservoirs, the Cossack Pioneer wellhead data is considered a reasonable proxy Impact Assessment Marine fauna use sound in a variety of functions, including social interactions, foraging, orientation, and responding to predators. Receptors identified that may potentially be impacted by underwater noise from development activities are: Marine mammals. Marine turtles. Fish. Figure compares expected sound frequencies from development-related activities with the hearing ranges of identified marine fauna. Where the frequencies overlap it can be anticipated that noise from the development activities will be audible to these receptors. Figure 10.10: Locations of Cross-sections of the Channel between North and South Scott Reef at the Locations of the TRD and TRE Drill Centres (Red Lines) for Modelling of Subsea Choke Valve Noise Propagation (colour scale is water depth in metres)

41 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 199 A B C D Figure 10.11: Cross-sections of the Channel between North and South Scott Reef at the Locations of the TRD (A and B) and TRE (C and D) Drill Centres, Showing Estimated Received Levels of Noise Based on the Measured Source Spectrum from the Cossack Pioneer Wellhead. The Top Plots were Calculated by the Image Method and the Bottom Plots using the Parabolic Equation Method

42 200 Browse FLNG Development Draft Environmental Impact Statement Underwater noise can affect marine fauna in three main ways: Injury to hearing or other organs, where hearing loss may be temporary (temporary threshold shift (TTS)) or permanent (permanent threshold shift (PTS)). Masking or interfering with other biologically important sounds, including vocal communication, echolocation, signals and sounds produced by predators or prey. Disturbance leading to behavioural changes or displacement of fauna, noting that the occurrence and intensity of behavioural changes can be highly variable and depends on a range of factors relating to the animal and situation. Sound level thresholds above which injury (TTS/PTS) or behavioural disturbance may occur vary widely between species and potentially between individuals of the same species. Thresholds above which injury may occur are not anticipated to be exceeded for any sensitive receptors by Browse FLNG Development activities and are not considered further. Table 10.9 summarises approximate threshold levels of noise that may result in behavioural disturbance to identified fauna receptors. Although behavioural responses to noise are likely to be variable and context-specific, these thresholds are widely accepted as appropriate for the assessment of impacts on receptors from underwater noise, being based on peer-reviewed and published scientific research. Table 10.9: Received Level Thresholds that may Cause Behavioural Disturbance to Fauna Receptor Approximate Received Level Threshold for Behavioural Disturbance (db re 1 μpa) Cetaceans Variable beginning at 120 to 160 Southall et al Fish Variable to greater than 90 above hearing thresholds References Popper et al. 2003; Scholik and Yan 2002a, 2002b; Xodus 2009; Hastings et al Marine turtles Greater than 170 Bartol and Musick 2003; McCauley et al Figure 10.12: Noise Frequencies for Key Development Activities Compared with Hearing Ranges of Marine Fauna.

43 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 201 Marine Mammals The Development area is not known to provide significant feeding or breeding habitats for marine mammals that result in predictable seasonal aggregations (Section 6.3.8). Potential impacts will therefore be limited to individuals that are transitory within the Development area. Humpback whales and pygmy blue whales occur in relatively low numbers with some predictability in the Development area during their annual migrations (Section 6.3.8). The main migration corridor for humpback whales is approximately 200 km to the east of the Development area within 50 to 100 km of the mainland, with low numbers further offshore. The majority of pygmy blue whales pass in deep water to the west of Scott Reef, but have been regularly recorded on noise loggers in the vicinity the reef over the migration periods. Pods of dolphins have been observed in larger numbers, but such pods are often fast moving and are therefore likely to be exposed to noise from development activities for only a short period. The levels of noise generated from the Browse FLNG Development may cause masking of acoustic cues and behavioural changes in marine mammals. Masking will mostly occur in the low frequencies (below approximately 5 KHz) as continuous noise sources associated with development activities are not likely to occur at the higher frequencies used by toothed cetaceans in echolocation (Figure 10.12). There has been relatively little behavioural observation of cetaceans exposed to continuous noise sources. However, Southall et al. (2007) conducted a review of existing studies and reported indications of no (or very limited) responses of cetaceans at received levels of noise below 120 db re 1 μpa, and an increasing probability of avoidance and other behavioural effects in the 120 to 160 db re 1 μpa range (Table 10.9). Estimated source levels of underwater noise from Development activities presented in Table 10.8 exceed these levels, and there is therefore potential for some degree of behavioural disturbance to marine mammals in proximity to the development. The onset and severity of behavioural responses in cetaceans depends on a number of factors, such as whether the frequencies and characteristics of the noise are of any biological significance to the animal; the animals activities at the time it is heard (e.g. feeding, resting, migrating, socialising); and their motivation to remain, approach or avoid. These factors can vary further between each individual or group. Another key consideration involves differentiating brief, minor, biologically unimportant reactions from profound, sustained, and/or biologically meaningful responses that may influence survival (Southall et al. 2007). For example, Croll et al. (2001) did not observe any response from feeding blue and fin whales receiving noise levels between 140 and 150 db re 1 μpa from continuous, low frequency sonar transmissions; whale movements were instead found to be influenced by the distribution and movement of prey, indicating that the generated noise levels were not a direct significant disturbance to the whales during feeding. In other instances, low-frequency baleen whale species and mid-frequency dolphin species have been observed to display avoidance behaviours and changes to vocalisations in response to received noise levels in the 120 to 160 db re 1 μpa range (Malme et al. 1984; Richardson et al. 1990; McCauley et al. 1996; Frankel and Clark 1998; Miller 2000; Buckstaff 2004; Morisaka et al. 2005; Hatch et al. 2012; Goldbogen et al. 2013). However, the behaviours observed during these studies have limited potential to cause harassment, or affect survival or population distribution (Southall et al. 2007; Hatch et al. 2012). Generally, the studies described above observed changes in whale speed, direction, orientation and vocalisation in response to introduced noise sources. These observations are not necessarily applicable to situations such as the Browse FLNG facility where an existing stationary noise source is approached from a distance by cetaceans, resulting in a more gradual increase in received noise levels. The most discernible behavioural reactions in cetaceans tend to occur at the sudden onset of noise, when noise sources change or increase suddenly, or when they occur unexpectedly (Richardson et al. 1995). Stationary and continuous industrial noise sources are typically observed to result in less dramatic avoidance reactions than moving noise sources, and in numerous cases cetaceans have been known to approach the noise source. For example, whales are often observed in close proximity to operating offshore infrastructure such as platforms and vessels that emit underwater noise. Whales have been recorded and reported to DOE by Woodside in close proximity to operating facilities such as the Nganhurra FPSO on numerous occasions. The noise source level of the Nganhurra FPSO has been recorded to be 172 db re 1 μpa (McPherson and Erbe in press), which is comparable to levels predicted close to the FLNG facilities and higher than the expected source level of the subsea wellheads (Duncan 2010, 2014). Potential impacts to marine mammals from underwater noise during the drilling, installation and commissioning phases will be of limited duration due to the temporary nature of activities in these phases of the development. Noise sensitive individuals might be expected to temporarily avoid areas where drilling, well evaluation and vessel-based activities are taking place. Startle responses from vessel and drilling activities are unlikely as source levels at the higher end of the potential range (e.g. from operation of bow thrusters or drilling) are not likely to occur suddenly in isolation. Vessels and drilling rigs will already be operating and emitting noise at lower levels prior to commencement of potentially noisier activities. While higher source levels are expected from well evaluation using VSP, any disturbance will be limited to a very short duration as this type of activity will only occur for up to 10 hours per well. As outlined in Section 9.2.5, if VSP is conducted at a drill centre, it will be subject to pre-start marine fauna observations and soft start procedures to ensure sensitive fauna are not in the vicinity, in accordance with EPBC Act Policy Statement 2.1 Interaction between offshore seismic exploration and whales. Should driven piling be required for installation of piles at Torosa, this would result in intermittent impulsive noise over short durations. For example, for the mooring lines for the FLNG facilities it is anticipated that one pile would be installed at a time at a rate of approximately one pile per day (24 piles in total). Active driving time for each pile would be expected to take between one and six hours within a 24 hour period, depending on environmental conditions, which would limit potential cumulative exposure of marine fauna to piling noise. In addition, noise management procedures would be

44 202 Browse FLNG Development Draft Environmental Impact Statement implemented to minimise the risk of impact to marine fauna, as outlined in Section Given the short duration of piling and the implementation of comprehensive noise management procedures, it is anticipated that driven pile driving would pose a low risk of potential impacts to marine fauna. Helicopter transfers will occur during all phases of the development. The level of received noise from helicopters depends on helicopter altitude, aspect and strength of noise emitted, and the receiver depth, water depth and other variables (Richardson et al. 1995). In general, helicopter noise is of short duration, peaking as the helicopter passes directly overhead. Received levels are expected to be low during transit when helicopter altitude is greatest. The highest received levels will occur at lower altitudes on approach to landing. Some behavioural disturbance may occur for short periods if marine mammals are present near the surface in the vicinity of landing helicopters. Ongoing noise sources during operational activities primarily include the FLNG facilities and subsea wellheads. Vessel noise will also continue to occur from occasional vessels associated with the development, and is only expected to generate an incremental increase to existing noise from the transit of vessels in the region. As outlined in Section , underwater noise modelling for the FLNG facilities indicates that during normal operations noise levels will drop below 120 re 1 μpa within 4 km of facilities based on mean noise levels, and drop below 130 db at 5 km from facilities at maximum levels (Figure 10.7 to Figure 10.9) (Duncan 2014). Some localised avoidance of the FLNG facilities at close proximity might therefore be expected to occur during normal operating conditions, with no significant ecological consequences anticipated. Underwater noise levels will be higher during offloading activities at the FLNG facilities. Under these conditions, noise levels are expected to drop below 130 db re 1 μpa at approximately 5 km from the source, and below 120 db re 1 μpa at 10 to 15 km from the source. At the Torosa location noise levels of 120 db re 1 μpa may reach the reef edge of Scott Reef and the eastern end of the channel between North and South Scott Reef. However, potential impacts will be temporary during offloading activities and times during which the Torosa FLNG facilities are emitting maximum underwater noise. Disturbance to marine mammals passing in proximity to Scott Reef or entering the reef system is expected to be minor as marine mammals are known to habituate to continuous noise sources and have been observed in close proximity to operating facilities at much higher noise levels. Background noise levels at Scott Reef are also naturally elevated, with levels of 90 to 100 db re 1 μpa recorded in the southern lagoon and daily spikes due to fish choruses that can raise background levels to 120 to 130 db re 1 μpa (McCauley 2008). Underwater noise levels from subsea wellheads will likely fall below 120 db re 1 μpa within approximately 500 m of the wellheads at the TRD and TRE drill centres (Duncan 2010). In addition, noise levels above 120 db re 1 μpa are not predicted to reach the top 100 m of the water column, even directly above the wellheads. Should noise levels from the wellheads be greater than predicted from measurements of the Cossack Pioneer wellheads discussed above, noise levels are still expected to be within a similar range as those generated by vessels. Potential impacts to whales and other cetaceans from increased noise levels in the vicinity of the wellheads are therefore expected to be minor and highly localised, and are not expected to cause disturbance to individuals transiting between North and South Scott Reef. In summary, increased underwater noise associated with all phases of the Browse FLNG Development may result in localised avoidance and/or behavioural disturbance in marine mammals in the vicinity of the FLNG facilities and subsea infrastructure. Given that relatively low numbers of transient marine mammals are expected to occur in the vicinity of development activities, and the Development area is not known to provide significant breeding or feeding habitats that result in predictable seasonal aggregations, only minor impacts are expected to occur, with no long-term effect at population level, as a result of noise emissions from the development. Marine Turtles Hearing has been studied in only a few individual marine turtles. Turtles have been shown to respond to low frequency sound, with indications that they have the highest hearing sensitivity in the frequency range 100 to 700 Hz (Bartol and Musick 2003). A startle response has been demonstrated to sudden noises. For example, McCauley et al. (2000) found that turtles showed behavioural responses to approaching seismic survey noise at approximately 166 db re 1 μpa, and more significant disturbance at 175 db re 1 μpa. However, such a response is less likely as seismic surveys emit pulsed sound at high source levels (greater than 200 db re 1 μpa), which is not representative of the primarily non-pulse noise sources associated with the Browse FLNG Development. Startle responses and other behavioural changes are more likely from high level pulsed noise sources such as those produced during seismic surveys compared to non-pulse sources such as vessels. The closest drilling and installation activities in proximity to turtle nesting habitat at Sandy Islet would be at the TRE drill centre approximately 7 km to the east. Modelling of noise from subsea wellheads has shown that noise levels are expected to drop below 120 db re 1 μpa at 500 m from the wellheads, which is well below noise levels at which disturbance to turtles is expected to occur (Duncan 2010). Noise from operation of the wellheads is therefore not expected to be audible in the vicinity of Sandy Islet at levels that would cause disturbance. Disruption to turtles from development noise is expected to be minor due to the transient nature of noise from drilling, installation and commissioning activities, and the low levels of noise during the operations phase in proximity to Sandy Islet. Fish Fish vary widely in their vocalisations and hearing abilities, but generally hear best at low frequencies below 1 khz (Ladich 2000). Behavioural effects of noise on fish may include changes to schooling behaviour and avoidance of the noise source (Simmonds and MacLennan 2005). Cartilaginous fish (such as sharks and rays) lack a swimbladder and are considered less sensitive to sound than bony fish. The hearing capabilities of the whale shark have not been studied, but it has been suggested that they are likely to be most responsive to low frequency sounds (Myberg 2001). Whale

45 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 203 sharks have been observed to dive upon ignition of nearby inboard vessel motors, which may be a response to the low frequency sound signature of such motors (Myberg 2001). Pelagic species may avoid sound exposure by swimming away from the source, with one example being recorded by Slotte (et al. 2004) who used sonar to observe pelagic blue whiting and Norwegian herring swimming to greater depths after exposure to a seismic source. Review work by Turnpenny & Nedwell (1994) also indicated that pelagic fish swim horizontally away from the sound source, while demersal fish most likely dive toward the bottom or into deeper waters. At some noise level, demersal fish also respond by forming tight schools and reducing their depth (McCauley et al 2000). However, fish of different sizes (ages) within a single species may show differences in behaviour (Normandeau Associates 2012). The levels of noise generated during Browse FLNG Development activities may cause some behavioural changes in fish or mask acoustic cues in the vicinity of development activities. Noise modelling predicted that noise emitted from the FLNG facilities will not increase noise levels significantly at Scott Reef, where fish are known to aggregate. As behavioural responses to noise are expected to be restricted to the immediate area of activities, no permanent changes in behaviour that could impact on long-term biological or ecological functioning of fish are expected. The impact assessment indicates that only minor behavioural disturbance is expected to occur to sensitive fauna as a result of noise emissions for drilling, installation and commissioning activities and ongoing operation of the Browse FLNG Development. The overall risk of environmental impact from underwater noise generated by the Browse FLNG Development is therefore assessed to be low Invasive Marine Species Background There is the potential for the introduction of IMS to occur at all stages of the Browse FLNG Development as vessels and drill rig will transit to and from the Development area regularly during the lifespan of the development. The most common transfer mechanisms for IMS are via uptake and discharge of ballast water or due to marine fouling on the hulls and internal niches (e.g. seawater intakes) on vessels. However, not all species that are introduced to an area outside of their natural range survive to become an IMS, with the majority of introduced species failing to establish (Williamson and Fitter 1996). The probability of successful establishment of an IMS depends on the: Infection at a source, such as a port, harbour or within coastal waters where IMS are present and reproducing. Survival of the IMS during their transfer to an area located beyond their natural range. Activities undertaken to enable a successful inoculation by the surviving IMS. Water temperatures, salinities and habitat that are sufficiently environmentally matched to permit the IMS s survival, establishment, growth and reproduction Impact Assessment Woodside has in place a comprehensive IMS Management Plan that has been developed in consultation with the relevant authorities. The FLNG facilities are currently scheduled to be built at a construction yard in Asia, where environmental conditions are anticipated to be widely different to those encountered during transit to Australian waters as well as those of the Development area. In addition, all marine infrastructure to be imported by sea for the Browse FLNG Development will be transported and installed in deep water (greater than 350 m), therefore providing unfavourable environmental conditions for IMS survival, settlement and reproduction. Similarly, LNG carriers and condensate tankers, transiting to the Development area from international ports, will travel in deep waters. In terms of ballast water exchange, all vessels mobilised from outside of Australia will undertake ballast water exchange in waters located further than 12 Nm from land and in water depths greater than 200 m. There is therefore a low likelihood of IMS introduction and settlement resulting in significant environmental impacts in the Development area, and the risk of impact is assessed to be medium Non-Hazardous Solid Waste Background Non-hazardous solid waste will be generated from FLNG facilities and vessels during all phases of the Browse FLNG Development. Solid waste will consist of: General non-hazardous waste. Putrescible waste Impact Assessment General Non-hazardous Solid Waste General non-hazardous waste may include, but is not limited to, scrap metal, packaging, wood, cardboard, paper and empty containers. This waste will not be discharged overboard and will be transferred onshore for recycling or disposal. Therefore, no impacts to the marine environment are expected from the generation of general non-hazardous waste during all phases of the development. The accidental discharge of general non-hazardous waste to the marine environment is discussed in Section Putrescible Waste Overboard disposal of food scraps and other putrescible waste will not occur within three Nm of land as well as Scott Reef, as outlined in Section Food scraps and other putrescible waste will be macerated to a diameter of less than 25 mm before disposal at sea beyond the 3 Nm limit (MARPOL 73/78 Annex IV). Impacts to the marine environment resulting from the disposal of macerated wastes are expected to be negligible. Accumulation of nutrients in surrounding waters or seabed is not expected due to the minor quantities of waste generated each day (approximately 1L/person/day with an average of 120 personnel onboard each

46 204 Browse FLNG Development Draft Environmental Impact Statement FLNG facility) and the assimilative capacity of open waters. There is potential that some opportunistic fish and oceanic seabirds may be attracted to the discharge of macerated waste either directly, in response to increased food availability or, indirectly as a result of attraction of prey species. However, given the small quantities of putrescible waste to be disposed, any attraction is likely to be localised, minor and temporary and is not expected to result in long term adverse impacts. The overall risk of environmental impact associated with the disposal of non-hazardous solid waste is therefore assessed to be low Hazardous Waste Background Hazardous waste generated during all phases of the development may include but is not limited to: Recovered solvents. Excess or spent chemicals. Paints and paint cans. Biological waste from medical facilities. Oil contaminated materials (e.g. sorbents, filters and rags). Batteries. Fluorescent light tubes. Waste oils. Mercury removal adsorbents. NORM and/or mercury contaminated extracted solids Impact Assessment Hazardous waste will not be discharged overboard and will be transferred onshore for recycling or disposal. Therefore, no impacts to the marine environment are expected from the generation of general hazardous waste during all phases of the development. The accidental discharge of hazardous waste to the marine environment is discussed in Section The overall risk of environmental impact associated with the disposal of hazardous waste is therefore assessed to be low Hydrotest Fluid Discharge Background Based on indicative reservoir layout and pipelay plans, a maximum of approximately 800 m 3 hydrotest fluid may be discharged at any one time prior to commencement of operations (volume of maximum flowline extent to be tested). In the event MEG is selected as the hydrotest fluid, MEG may be discharged to sea prior to installation of the FLNG facilities. Once the FLNG facilities are in place, MEG used as hydrotest fluids would be recovered to the FLNG facilities with only very minor volumes discharged at sea during recovery operations Impact Assessment MEG is classed as having low toxicity and has been rated to Pose Little Or No Risk (PLONOR) by OSPAR (2004). MEG is readily degradable and will dilute rapidly below levels that could cause impacts to marine biota, resulting in highly localised, temporary and minor change in water quality in the immediate vicinity of the discharge point. Due to the offshore deep water location of the discharge, the risk of environmental impact to marine biota is expected to be low. The potential impacts arising from the discharge of hydrotest fluid are: Temporary decline in water quality due to discharge of oxygen-depleted hydrotest fluid and associated impacts to marine organisms. Toxicity to marine organisms due to chemical additives. Discharged hydrotest fluid will contain chemical additives in low concentrations. Hydrotest chemicals will at a minimum have a hazard quotient (HQ) category of Silver or Offshore Chemical Notification Scheme (OCNS) Category D under the UK OCNS. The dyes to be used are non-toxic at the concentrations utilised. During discharge the dye may result in a temporary localised discoloration in the immediate vicinity of the discharge point; however, as the dye is water soluble, it will rapidly disperse in the marine environment with no anticipated toxicity effects on marine organisms. Owing to the use of oxygen scavengers in the flowlines to reduce the potential for corrosion, the hydrotest fluid discharge will be low or lacking in oxygen. Such discharge is expected to result in oxygen depletion of biota exposed to the de-oxygenated plume of hydrotest fluid until the plume has mixed sufficiently with surrounding waters. However, given the short duration of the discharge and discharge location in open oceanic waters, the impacts are expected to temporary, minor and highly localised. The biocides to be used in the hydrotest fluid are expected to degrade gradually over time while the hydrotest fluid is within the flowlines and equipment (at least 12 months) and further degrade on discharge to the marine environment, resulting in minimal environmental impact. Similarly, other additives in the hydrotest fluid will be in a diluted form, and when discharged to sea will be further rapidly diluted to extremely low concentrations that are predicted to be harmless to marine biota in the area. As the hydrotest fluid will remain inside the flowlines and infrastructure for at least 12 months, the toxicity of residual chemicals, through decay, will be markedly reduced over time. The potential for impacts to water quality and marine organisms will be limited to a small area in the immediate vicinity of the discharge point. Impacts to marine biota are therefore expected to be minor and localised. In terms of the potential for toxicity effects to coral and fish larvae at Scott Reef due to discharge of hydrotest fluid at the closest facility (BWB-TR FLNG facility), as discussed for PW (refer to Section 10.11), any sublethal impacts or mortality due to toxicity effects would not be expected to result in adverse consequences to Scott Reef or Seringapatam Reef (refer to AIMS 2012a). Discharge of hydrotest fluid at the BWC-TR facility will be short-lived and associated impacts expected to be limited to a small extent in the vicinity of the discharge, beyond which impacts to coral and fish larvae in open waters and at Scott Reef are not expected.

47 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 205 With the implementation of standard Australian industry practice measures, and the inherent controls, management and mitigation measures outlined in Section 9.2.9, environmental impacts of hydrotest fluid discharge are considered minor and unlikely to affect pelagic communities (when discharged at or near the sea surface) due to the transient presence and limited exposure or benthic communities (when discharged near the seabed) due to the sparseness of benthic fauna and fish in the deep waters of the Development area. The overall risk of environmental impact from hydrotest fluid discharge is assessed to be low Produced Water Background Produced water (PW) will be generated at each FLNG facility, and treated prior to disposal to the marine environment. The volume and composition of PW will vary over the life of the development, generally increasing over time depending on the production rates of the condensed and formation water streams. On discharge into the marine environment, PW will be subject to a number of processes which affect the composition of the PW discharge stream and thereby affect its toxicity to marine organisms, including: Dispersion and dilution by currents. Volatilisation and evaporation to the atmosphere. Adsorption to naturally-occurring particles, then settling to the seabed. Metabolisation as an energy source by pelagic and benthic bacteria, and other organisms. Degradation via chemical and photo-degradation. For example, studies undertaken on the fate of PW from Woodside s North West Shelf Project facilities determined the dispersion and degradation pathways of non-volatile hydrocarbons in PW. Of the daily discharges of these constituents in PW it was found 53% dissolved, 26% was suspended, 14% adhered to sediment, 3% settled and 4% evaporated (Burns et al. 1999). A discharge of PW to the marine environment has the potential to affect marine biota through toxicity of its components and from the temperature of the discharge stream. Toxicity of the PW discharge is dependent on the fate of the following components in the marine environment: Metals, which occur in low concentrations in PW streams, are in a low oxidative state and on entering the marine environment will rapidly oxidise and precipitate into inert forms that are non-toxic to marine organisms (E&P Forum 1994, OGP 2005). Mercury in PW streams typically occurs in trace concentrations in its relatively low toxicity forms, namely elemental mercury (Hg(0)) and with some potential for production of HgII (e.g. mercury chloride and mercury sulphide). Elemental mercury, which is relatively unreactive, has little tendency to dissolve in water and readily volatises into the atmosphere (Neff 2002). Of the different Hg forms, methyl-mercury (MeHg), is of most concern because it is readily bioavailable and can be responsible for toxicological effects at very low doses but is not expected to be produced from the reservoirs. Conversion from the other Hg forms to MeHg does not occur in welloxygenated marine waters (Neff 2002) such as those of the Development area (Gardline 2009). Instead, methylation of Hg is a natural process mediated by bacterial decomposers in anoxic environments that has the potential to occur in the deep sea (Hamdy and Noyes 1975, Neff 2002). Thus the immediate risk for bio-accumulation to occur due to trace amounts of Hg in PW discharge is remote. Trace amounts of dissolved hydrocarbon compounds remaining in the water after treatment (OGP 2005) Modelling In order to further understand the potential impacts associated with the PW discharge, in particular effects associated with the discharge s hydrocarbon content and temperature, Woodside commissioned DHI Water & Environment Pty Ltd (DHI) to model the fate and transport of discharged PW from one of the Torosa FLNG locations, as the closest discharge point to sensitive receptors at Scott Reef (DHI 2014). Modelling Methods Modelling was undertaken using a combination of hydrodynamic models to understand the behaviour of the discharge plume, comprising: The Cornell Mixing Zone Expert System (CORMIX 8.0), to describe: The behaviour of the plume with distance, in particular its width and thickness. Dilution characteristics of the discharge plume due to initial mixing under the momentum and buoyancy of the discharge flow. The calibrated and validated 3-D hydrodynamic model specific to Scott Reef and surrounds (MIKE 3 NPA), applied to describe far-field mixing and dilution under the influence of varying metocean conditions including wind and tidal and non-tidal currents. To examine potential differences in plume characteristics and dispersion during different times of the year, separate modelling runs were carried out for the summer (October to February), winter (May to July) and transitional seasons (March to April and August to September). Modelling Parameters and Assumptions Woodside identified one worse-case scenario to be modelled based on a PW maximum design rate of 1,680 m 3 /day, where the PW is discharged horizontally, below sea surface (Table 10.10). This scenario represents maximum PW processing capacity of the facilities and would not be expected to be reached until late in reservoir life.

48 206 Browse FLNG Development Draft Environmental Impact Statement The modelling included the following additional assumptions for a conservative approach to this assessment: The assessment considered the oil-in-water content to be 30 mg/l in line with former regulatory allowable concentrations stipulated in the OPGGS (E) Regulations. The model conservatively assumes that only dilution processes reduce the concentration of various components in PW. Reductions due to weathering processes (e.g. evaporation of volatile compounds) or mixing processes (e.g. wave action in the upper water column) are not taken into account. This results in an overestimation of concentrations in modelling predictions. Modelling Thresholds - PW Toxicity Based on worst case hydrocarbon content in the PW discharge stream (30 mg/l), hydrocarbon is the most toxic constituent of the PW discharge, with other contaminants such as mercury present in less toxic concentrations. The toxicity threshold used to characterise impacts to marine organisms is derived from ecotoxicological studies conducted on Browse condensate samples (ESA 2009). These ecotoxicology tests were undertaken on a broad range of taxa for which accepted standard test protocols are well-established, in accordance with ANZECC/ ARMCANZ (2000) recommendations. Procedures followed standard industry practice protocols in accordance with The Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR)/PARCOM and Concawe (1992) protocols. In total, seven ecotoxicology tests were conducted on six representative Australian species from different taxonomic groups, using predominantly tropical species (four tropical and two temperate species) (Table 10.11) and using standard test protocols with known reproducibility. The majority of the ecotoxicology tests were focused on the early life stages of test organisms, when organisms are typically at their most sensitive. Ecotoxicology tests on reef-building taxa such as scleractinian corals were not commissioned since standard test protocols do not exist for these species. The highest ANZECC/ARMCANZ (2000) protection level (99%) was conservatively adopted for the purpose of this assessment, given the relative proximity of the closest FLNG facility to Scott Reef (approximately 8 km). The threshold provides protection among the most sensitive of species. The lowest No Observed Effect Level (NOEL) for unweathered Browse condensate was found to be 20 mg/l based on both the fish imbalance and tiger prawn acute toxicity tests (Table 10.12). Using CSIRO s BurriliOZ statistical software, the Burr type III distribution curve was statistically fitted to the NOEL data to determine that the 99% species protection threshold was 0.09 mg/l of condensate and an exposure time of 96 hours. It is important to note that the vast majority of species will be more resilient to hydrocarbon concentrations at the defined threshold, which corresponds to only 1% of species having a toxic response at concentrations of 0.09 mg/l. Although corals were not among the test organisms used in the laboratory study (ESA 2009), the ANZECC/ARMCANZ (2000) approach provides a robust and sound basis for extrapolating the ecotoxicology findings from the laboratory to the protection of aquatic organisms in the environment, including sensitive species such as corals. Villanueva et al. (2008, 2011) found that toxicity effects to coral larvae and adults at significantly higher loading rates (approximately 8,000 mg/l) only occurred when exposed to condensate solutions that were undiluted or subject to few dilutions. Similarly, in a review of acute and chronic effects, Shigenaka (2001) concluded a threshold value of 20 mg/l of oil in the water column was the concentration at which sublethal effects in corals could be elicited, and transient exposure to hydrocarbon (water-soluble) concentrations less than 20 mg/l were unlikely to result in lasting harm to coral reefs. The adopted threshold value of 0.09 mg/l (equivalent to 333 dilutions or 0.3% PW) is therefore considered to be conservative for the protection of corals communities at Scott Reef including early life stages. Table 10.10: Modelled PW Discharge Scenario at the BWC FLNG Facility Scenario PW discharge at the BWC FLNG facility Discharge Rate (m 3 /day) Discharge depth (m below MSL) Pipe diameter (m) 1, PW characteristics Salinity: 25.9 ppt below ambient Temperature: 4 C above ambient Density: kilograms per metres cubed (kg/m 3 ) Hydrocarbon concentration: 30 mg/l Table 10.11: Distribution of Species Used in the Ecotoxicology Tests Organism Species Distribution Sea urchin Heliocidaris tuberculata Sub-tropical to temperate Rock oyster Saccostrea commercialis Tropical and sub-tropical Marine micro-alga Isochrysis aff. galbana Tropical and sub-tropical Marine macro-alga Hormosia banksii Temperate Penaeid prawn Penaeus monodon Tropical Barramundi fish Lates calcarifer Tropical

49 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 207 This threshold and associated dilution, when applied to the expected concentrations of other contaminants forming part of the PW discharge (including mercury), is equivalent to thresholds below those given in ANZECC/ARMCANZ (2000) (i.e. mercury less than mg/l). Modelling Thresholds Temperature The assessment criteria for evaluating potential impacts to the marine environment, from increased water temperature, was a 3 C exceedance above ambient 95% of the time, in line with ANZECC/ARMCANZ (2000). Modelling Results For the remaining 5% of the time, the model indicated that, during the short-lived slack tide period of a tidal cycle, the reduced current speeds had the potential to occasionally cause the PW plume to temporarily pool at the point of discharge. As the reversing tidal currents pick up in strength, this built-up pocket of water is transported down-current, resulting in the PW discharge diluting to below threshold concentrations at distances ranging from 2.3 and 2.7 km from the FLNG facility (summer and winter conditions respectively) (Table 10.13). Given discharge temperature of PW is only slightly warmer (4 C) than ambient water temperature, PW from the FLNG facility was predicted to cool rapidly to less than 3 C above ambient within less than 10 m from the outfall at the peak discharge rate. Owing to its salinity properties and resulting buoyancy, the PW plume was predicted to rapidly rise to the surface (DHI 2014), only narrowly spreading within the first kilometre from the discharge point. Table presents the lateral distances predicted by the model to reach the adopted hydrocarbon concentration threshold criteria at the peak PW discharge rate (DHI 2014). Assuming an oil-in-water concentration of 30 mg/l, the model indicated that the mixing zone, within which threshold values (0.09 mg/l) will be exceeded, would range between 420 m and 1 km from the FLNG facility (summer and winter conditions respectively) for 95% of the time (Table 10.13). Table 10.12: Summary of Toxicity Test Data for Water Accommodated Fraction of Torosa Condensate (ESA 2009) Toxicity test Endpoint Loading (mg condensate/l) 1hr- EL (520 to 570) 1-hr sea urchin fertilisation test NOEL 330 LOEL hr EL50 4,170 (3,500 to 5,100) 72-hr sea urchin development test NOEL 1,320 LOEL 2, hr EL50 2,780 (2,620 to 2,940) 48-hr rock oyster larval development test NOEL 1,320 LOEL 2, hr EL50 Greater than 84, hr micro-algal germination test NOEL Less than 5,300 LOEL 5, hr IL50 Greater than 5, hr micro-algal growth test NOEL 5,310 LOEL Greater than 5, hr EL hr larval fish imbalance test NOEL 20 LOEL hr EL hr Tiger prawn toxicity test NOEL 20 LOEL 40 Definitions: EL50 is the median effective loading rate It represents the loading rate of the condensate in water (grams per litre (g/l)) that is estimated to cause a defined toxic effect to 50% of the test organisms. In most instances, the EC50 and its 95% confidence limits are statistically derived by analysing the percentages of organisms affected at various test loading densities after a fixed period of exposure. IL50 is the inhibiting loading rate for a 50% effect. It represents a point estimate of a loading rate of condensate that causes 50% inhibition compared to the control, in a quantitative biological measurement, namely microalgal cell yield at the end of the test NOEL is the no-observed effect loading rate It represents the highest loading rate of the condensate for which no statistically significant effect on the test organism was observed relative to the control. LOEL is the lowest-observed-effect loading rate It represents the lowest loading rate of the condensate for which a statistically significant effect on the test organism was observed, relative to the control.

50 208 Browse FLNG Development Draft Environmental Impact Statement Table 10.13: Lateral Distance from PW Outfall at Torosa BWC FLNG Facility to achieve Threshold Criteria for Hydrocarbons and Temperature (DHI 2014) Parameter Hydrocarbons (0.09 mg/l) Temperature (3 C) Season Distance to reach Threshold Level (m) based on 95%-ile concentration value Distance to reach Threshold Level (m) based on maximum concentration value Transitional 710 2,700 Summer 420 2,300 Winter 1,000 2,700 Transitional Less than 10 Less than 10 Summer Less than 10 Less than 10 Winter Less than 10 Less than Impact Assessment Potential Toxicity Effects Open waters The model predicted that there is potential for marine organisms that are present in surface waters to be exposed to PW above threshold concentrations if encountering the plume as it is transported by prevailing currents downstream from the FLNG facility. Any potential for acute or chronic toxicity to marine organisms would be expected to be limited to within up to 2.7 km from the FLNG facility in worst case metocean conditions. However the open waters of the Development area are not known to host sensitive marine biota, due to the depths and lack of seabed features. These concentrations will only affect a limited number of species, most likely transient and well represented throughout the region. This potential for toxicity effects within these distances is however conservative given the assumptions included in the model. In reality, the actual PW discharge rates will likely be lower than the peak, subject to both weathering and wave mixing processes. In addition, the direction of the plume emanating away from the discharge point will change depending on the current direction primarily driven by the tides, such that exposure to PW discharges in waters surrounding the FLNG facility will not be continuous. Transient marine organisms likely to occur in the Development area, such as plankton and fish will likely not be exposed to the PW plume for a sufficient time to elicit a toxic response. Scott Reef The model predicted that the PW plume would disperse to below toxicity threshold concentrations within less than 3 km from the FLNG facility; therefore impacts to Scott Reef, approximately 8 km away, are not anticipated. This means that PW concentrations are far lower than those that could elicit a toxic response based on the adopted dissolved hydrocarbon threshold (requiring 333 dilutions or 0.3% PW). Jones and Heyward (2003) reported on the toxicity of PW from the Harriet A platform, which produces crude oil, condensate and gas. Significant changes in photosynthesis of isolated zooxanthellae (symbiotic algae found in corals) only occurred at relatively high PW concentrations (LOEC = 6.25% PW) based on observations after four days of continuous PW exposure. Similarly, it was found coral continuously exposed to relatively high PW concentrations (up to 10% PW) for eight days exhibited no significant change in colony photosynthesis, respiration or density of zooxanthellae. Monitoring programs have been conducted in the North Sea and Gulf of Mexico at areas with a high density of offshore platforms to investigate environmental effects of PW discharge (OGP 2005). While the presence of PW constituents was detected, monitoring did not identify adverse impacts due to PW discharge. For instance, surveys in the North Sea and Gulf of Mexico have not found elevated contaminant levels in fish tissue and in the Gulf of Mexico, monitoring found no indication of significant bioaccumulation of PW constituents in marine organisms. Coral and Fish Larvae In terms of the potential consequences of PW discharge on coral and fish larvae that may occur in waters adjacent to Scott Reef, Woodside commissioned AIMS to evaluate a scenario in which it was assumed there would be 100% mortality of coral and fish larvae within a 500 m radius of the previous development concept s Torosa infield platform as a result of PW discharge (AIMS 2012a). This scenario was highly conservative as it represents a PW toxicity level far greater than anticipated, and given that plankton will have a temporary transient presence in the plume. AIMS concluded that this scenario would be unlikely to have any detectable impact on coral recruitment or any significant impact on fish recruitment at Scott Reef and Seringapatam Reef (AIMS 2012a). Based on this study, and considering the Torosa FLNG facilities will be a further 1 km from Scott Reef, the discharge of PW from the FLNG facilities will have no effect on recruitment of coral or fish at reefs within the region. The risk of toxicity impacts to marine biota associated with the discharge of PW is assessed to be low. Potential Thermal Impacts Given only 1.3 dilutions are required for the temperature of the PW to achieve threshold temperature, thermal impacts to marine organisms are not expected to occur. With the implementation of inherent controls, management and mitigation measures detailed in Section , the risk of thermal impacts to marine biota associated with the discharge of PW is considered low.

51 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE Cooling Water Background Although cooling water will be required for vessels and rigs involved with drilling, the largest requirement for cooling water will be from the operation of the FLNG facilities for process cooling, steam condensing and equipment cooling. As such, cooling water discharges from vessels and rigs are not included in this assessment, as they will be of short durations and comprise minor volumes. Discharged cooling water from the FLNG facilities will enter the marine environment both horizontally and vertically between 5 and 20 m below the surface, the majority of which will be horizontal at approximately 5 to 6 m. Average cooling water temperatures at the point of discharge are expected to be approximately 30 ºC (up to approximately 38 ºC in the summer months), which is approximately 1 to 5 ºC above ambient seawater temperature depending on the season. From each FLNG facility the, largest single cooling water discharge from any one location is expected to be at a discharge rate of 56,000 m 3 /hr. Each FLNG facility s steam boiler will result in the discharge of water at a rate of approximately 15 m 3 /hr and temperatures of approximately 100 ºC. The cooling water discharge system will be dosed with biocide (hypochlorite) to control marine fouling. Most chlorine will react and be neutralised within the cooling water systems and further reductions in chlorine concentrations will occur due to chemical and photo-degradation processes (Snoweyink and Jenkins 1980). Dosing of cooling water with chlorine (as sodium hypochlorite) gives rise to chlorine-produced oxidants comprising weak hypochlorous acid, hypochlorite ions and hypobromous acid. The decay of these chlorine-produced oxidants is rapid in the marine environment (DHI 2011a). The decay rate of chlorine-produced oxidants is influenced by environmental factors such that toxicity and half-lives are reduced when there is reaction with organic matter, redox reactions (alteration of oxidation state) and exposure to sun light. Residual chlorine levels will be less than 200 ppb at the point of discharge with the exception of temporary periods of shock dosing at approximately 500 ppb Modelling Woodside commissioned DHI to undertake modelling to simulate the fate of the cooling water plume from the BWC FLNG facility (DHI 2014). Cooling water discharge modelling was undertaken using the same combination of near-field and far-field hydrodynamic models used for the modelling of PW discharge (Section 10.11). To reflect the rapid decay of chlorine-produced oxidants in the marine environment, a 20 minute half-life for residual chlorine was adopted in the model. To examine potential differences in plume characteristics and dispersion during different times of the year, separate modelling runs were carried out for the summer (October to February), winter (May to July) and transitional seasons (March to April and August to September). Modelling Parameters and Assumptions Parameters used for the modelling of the cooling water discharge are provided in Table The modelling took a conservative approach as it did not take account of all mixing processes due to wave action in the upper water column which will likely serve to increase the magnitude of dilution acting on the cooling water plume. This is likely to result in an underestimation of mixing and dilution and overestimation of cooling water concentrations in modelling predictions. Furthermore, in order to provide a conservative representative illustration of the spatial extent of potential for impacts, modelling plots are based on 95th percentile values and show the highest value that would be achieved for 95% of the time. Modelling Thresholds The assessment criteria for evaluating potential impacts to the marine environment from increased water temperature was a 3 C exceedance above ambient 95% of the time in line with ANZECC/ARMCANZ (2000) guidelines. A CSIRO study of the scientific literature on the toxicity effects of chlorine concluded 13 ppb was the predicted no effect concentration for acute exposure, while 2 ppb was the predicted no effect concentration in the event of chronic exposure to chlorine at the 99% species protection level (Chariton and Stauber 2008). A toxicity threshold of 2 ppb of chlorine was therefore adopted. This 99% species protection threshold can be regarded as providing protection for the most sensitive of species. It is important to note that the vast majority of species will have higher tolerance compared to this threshold, such that it will only be the most sensitive species that have a toxic response at a 2 ppb chlorine concentration. Modelling Results Owing to its temperature properties, the cooling water plume is strongly buoyant, with the plume rapidly becoming surfaceattached in the water column (DHI 2014). Table presents the lateral distances predicted by the model to reach the adopted threshold criteria for temperature and residual chlorine at the peak cooling water discharge rate (DHI 2014). Table 10.14: Modelled Cooling Water Discharge Scenario at the Torosa BWC FLNG Facility Scenario Discharge Rate (m 3 /day) Discharge Depth (m below MSL) Pipe Diameter (m) Cooling Water Characteristics Salinity: ambient Temperature: 12 C above ambient Density: kg/m 3 Residual chlorine: 200 ppb Discharge at the BWC FLNG facility 1,344, per pipe (four pipes)

52 210 Browse FLNG Development Draft Environmental Impact Statement On discharge the cooling water plume will be subject to dilution processes, which will reduce its temperature. The model indicated that temperature is expected to reduce down-current of the discharge point to below threshold levels (3ºC above ambient) within 190 m or less in winter and within shorter distances in summer and the transitional season (110 m or less and 140 m or less respectively) for 95% of the time (Table 10.15). At other times (adding up to less than 5% of the time), the model indicated that, during the short-lived slack tide period of a tidal cycle, the reduced current speeds may occasionally cause the cooling water plume to temporarily pool around the discharge point. As the reversing tidal currents pick up in strength, this built-up pocket of water will be transported downstream, resulting in dilution below threshold concentrations being achieved at further distances away from the FLNG facility (no more than 2.9 km in the transitional season, 2.5 km in winter and 1.8 km in summer) (Table 10.15). The model predicted the residual chlorine concentrations in cooling water (200 ppb) will reduce down-current of the discharge point to threshold concentration (2 ppb) within 1.4 km or less in winter and within shorter distances in the transitional and summer seasons (1.3 km or less and 1.1 km or less respectively) for 95% of the time (Table 10.15). At other times (adding up to less than 5% of the time), the model indicates that, occasionally, following a slack tide period, the thermal plume may be diluted below thresholds at further distances down-current of the discharge point (no more than 2.5 km in winter, 2.9 km in the transitional season and 1.8 km in summer) (Table 10.15) Impact Assessment The potential impacts arising from discharge of cooling water will include: Thermal impacts to marine organisms. Decline in water quality associated with lowered dissolved oxygen concentrations as a result of elevated water temperature. Toxicity effects to marine organisms due to biocide additives, in particular chlorine. The model has predicted that there is potential for marine organisms that are present in surface layer waters to be exposed to temperature and chlorine above threshold criteria if encountering the cooling water plume as it is transported down-current away from the FLNG facility discharge point. Any potential for acute or chronic toxicity or thermal impacts to marine organisms would be expected to be limited to within the distances set out in Table The potential for impact however is likely to be less given that the actual cooling water discharge plumes will likely be subject to wave mixing processes, which will hasten dilution and reduction of temperature and chlorine concentration. Elevated seawater temperatures have the potential to cause alteration of the physiological processes (especially enzymemediated processes) of exposed biota (Wolanski 1994). These alterations may cause a variety of effects, ranging from behavioural response (including attraction and avoidance behaviour), minor stress and potential mortality for prolonged exposure. The potential for thermal impacts and associated reduction in oxygen is limited due to the rapid reduction in cooling water temperature in receiving water and localised affected area. While coral bleaching can be triggered by prolonged exposure to water temperatures that are 1 to 2 C above long-term summer maxima (Hoegh-Guldberg 1999), no temperature elevations are expected at Scott Reef due to cooling water discharge. In terms of the potential for toxicity effects due to exposure to chlorine, it is important to note the direction of the plume emanating away from the discharge point will change depending on the current direction, such that exposure to cooling discharges of fixed areas surrounding the FLNG facility will not be continuous. Some pelagic marine organisms, particularly plankton but also migratory fish, will be transient within the cooling water plume. Given temporary exposure to the cooling water, it is likely that exposure times for marine organisms that enter the cooling water plume may not be of sufficient duration to elicit a toxic response. As previously assessed for the PW assessment, it would not be expected that discharge of the cooling water plume would have any detectable impact on coral recruitment or any significant impact on fish recruitment at Scott Reef and Seringapatam Reef. In conclusion, based on the modelling results, the potential for toxicity and thermal effects are expected to be temporary, localised and confined to a small portion of the water column (i.e. surface layer) and exposure of transient marine organisms is expected to be short-lived. Given the large separation distance between Scott Reef and the closest FLNG facility (approximately 8 km), impacts to Scott Reef (including coral habitats) due to cooling water discharge exposure are not expected. With the application of inherent controls, management and mitigation measures detailed in Section , the risk of environmental impacts associated with cooling water discharge are expected to be low. Table 10.15: Lateral Distance from Cooling Water Outfall at Torosa BWC FLNG Facility to achieve Threshold Criteria for Excess Chlorine and Temperature (DHI 2014) Chlorine (2 ppb) Parameter Temperature (3 C above ambient) Season Distance to Reach Threshold Level (m) based on 95% Concentration Values Distance to Reach Threshold Level (m) based on Maximum Values Transitional 1,300 2,400 Summer 1,100 2,300 Winter 1,400 3,300 Transitional 140 2,900 Summer 110 1,800 Winter 190 2,500

53 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE Sewage and Sullage Background Sewage and sullage (grey water generated from domestic processes such as dish washing, laundry and showers) will be generated on rigs, vessels and the FLNG facilities. Estimated volumes are expected to vary, up to 30 m 3 /day at maximum personnel capacity during maintenance events. The FLNG facilities are located in deep oceanic waters that are distant from sensitive receiving environments such as Scott Reef (closest being BWB-TR at 8 km). During the drilling phase, the closest temporary drill rig (and associated support vessels) used for the TRE drill centre is anticipated to be located approximately 2 km from Scott Reef. Untreated sewage will not be discharged within three nautical miles of Scott Reef Impact Assessment The offshore disposal of sewage and sullage from the FLNG facilities may result in a localised and temporary increase in the nutrient content in the water column. Scott Reef, the nearest sensitive receptor is not expected to be at risk from the discharge of treated sewage and sullage, as discharges would rapidly disperse in close proximity to the discharge points due to: The nature of the discharge is neutrally buoyant, which can reduce vertical dilution (Woodside 2008). The strong tidal currents through the channel between North and South Scott Reef create significant horizontal dispersion but limited vertical mixing (DHI 2009, RPS Metocean 2008 and Woodside 2008). The wind-driven currents are strongest near the surface (DHI 2009, RPS Metocean 2008 and Woodside 2008). Although organic materials from the discharges will likely exert biological oxygen demand (BOD) on the receiving waters, this is unlikely to reach levels below background ambient dissolved oxygen concentrations. Similarly while the nutrient inputs from discharged effluent will rapidly be taken up by phytoplankton, pronounced increases in productivity as evidenced by increased chlorophyll a concentrations are not expected. This is due to the assimilative capacity of the open ocean and nutrients are not expected to accumulate in the vicinity of the discharge locations. Given that the resulting small scale discharge will potentially give rise to minor increases above background levels in the vicinity of the discharge, the effects of discharge of sewage and sullage on the marine environment are expected to be localised, minor and temporary. The effects of sewage and sullage discharges on the water quality at Scott Reef were monitored for the Torosa-6 drill rig operating near the edge of the deepwater lagoon area at South Scott Reef (ERM and SKM 2008). The Torosa-6 drill rig using a MARPOL-approved sewage treatment plant produced approximately 10 m 3 /day of sewage/grey-water during the drilling operation, which is comparable to the rates estimated for routine operations during the Browse FLNG Development. Monitoring at stations 50, 100 and 200 m downstream of the platform and at five different water depths confirmed that discharges were rapidly diluted in the upper (less than 10 m) water layer and no elevations in water quality monitoring parameters (e.g. TN, total phosphorous and selected metals) were recorded above background levels at any station. This indicates that there are no detectable impacts due to treated sewage and sullage effluent discharges. Given the TRE drill centre location is in deeper waters and exposed to greater current speeds to that of the Torosa-6 drill rig monitored in 2008, and all other activities will be further away in deeper water environments, discharge of sewage and sullage is not expected to impact on sensitive habitats at Scott Reef. Cumulative impacts resulting from sewage and sullage discharges from up to three FLNG facilities, vessels and drill rig are not expected, given the geographic spread of the FLNG facilities (minimum of 10 km). Owing to the small volumes of sewage and sullage generated, and the application of inherent controls, management and mitigation measures outlined in Section , the risk of environmental impact associated with the discharge of sewage and sullage is low Drain Discharges Background Drainage will typically be collected and routed through drain collection tanks to slops tanks for treatment. These drain collection vessels will be equipped with an overflow arrangement ensuring that only clean water goes overboard. The overflow will only be used during periods of heavy rains in excess of the pump capacity or during operation of the fire deluge system. Drainage from within machinery spaces will be captured separately for treatment, where oil will be recovered and treated water (less than 15 mg/l oil in water) discharged overboard Impact Assessment Considering the composition of the drain discharges, and the open ocean waters of the discharge point, the discharge is expected to rapidly dilute in surrounding waters, with negligible effects on the marine environment. Accidental drain discharges with oil-in-water content greater than 15 mg/l are discussed in Section With the application of inherent controls and management and mitigation measures, the risk of environmental impact associated with drain discharge is low Subsea Control Fluids Background Operations of the subsea infrastructure of the Browse FLNG Development will result in the intermittent discharge of small volumes of subsea control fluids. The subsea control fluid to be used during operations has yet to be selected, with its exact composition depending on technical performance requirements to be further defined during latter phases of the development. However, subsea control fluids are typically water-based with additives including 40% MEG and proportionately smaller quantities of other components such as lubricants, corrosion inhibitors, biocides and surfactants, resulting in an overall low toxicity to the marine environment Impact Assessment The intermittent discharge of small volumes of low toxicity subsea control fluid may result in a minor, localised and temporary change in water quality in the deep waters of the Development area (greater than 350 m). The discharge would be rapidly diluted in the prevailing currents within metres (or less) downstream of the discharge point.

54 212 Browse FLNG Development Draft Environmental Impact Statement At the depths where these discharges will occur, benthic fauna is also expected to be sparse with no sensitive communities recorded in the deep waters of the Development area. Given these considerations, only minor, localised and temporary effects on the benthic marine environment are expected. The risk of environmental impact from the discharge of subsea control fluid is therefore low Desalination Brine Background Desalinisation brine will be generated through the production of freshwater for potable and other uses on the FLNG facilities, drill rig, installation and support vessels. The discharge of desalination brine, consisting of water with elevated salinity (typically 20 to 50% higher than the intake seawater) and low concentrations of anti-scale chemicals, is expected to be continuous throughout the life of the development, although volumes will vary depending on potable water requirements on each FLNG facility, development vessel or drill rig, where the FLNG facilities represent the most significant source of desalination brine for the Development (Section ) Impact Assessment On discharge, the desalination brine, due to its higher density, will tend to sink in the water column and will be subject to rapid dilution and dispersion in the prevailing currents. Given the desalination brine is only 20 to 50% more saline than the intake seawater (depending on the desalination process used), only a few dilutions would be required to return the brine discharge back to ambient salinity levels, which is likely to be achieved within a short distance of the discharge point. Therefore, owing to high dilution, any elevation in salinity will be highly localised at the discharge point and is unlikely to have a perceptible effect on ambient salinity concentrations in the water column. Most marine species are able to tolerate short-term fluctuations in salinity of 20 to 30% (Walker and McComb 1990), as such; temporary, localised salinity increases in the immediate vicinity of the discharge are not expected to have a medium to longterm effect on marine biota. Similarly, the potential for toxicity effects to marine biota due to dosing with anti-scale chemicals is unlikely as these chemicals have low inherent toxicity (i.e. fit for human consumption in potable water), will be consumed and neutralised in the desalination system and any remaining chemicals will be rapidly diluted on discharge. Given these considerations, only minor, localised and temporary effects to the marine environment are expected. The overall risk of environmental impact associated with discharge of desalination brine is therefore low Drill Cuttings and Fluids Background Potential environmental impacts associated with the discharge of drill cuttings and fluids include: Temporary increase in turbidity in the water column. Smothering of benthic communities and alteration of sediment particle size characteristics of seabed sediment. Toxicity to benthic communities. Decline in sediment quality associated with organic enrichment and de-oxygenation of seabed sediment and associated secondary impacts to benthic marine fauna. Change in water quality and associated toxicity to in-water organisms Modelling An assessment of drill cuttings discharge was undertaken by DHI (DHI 2011b) to model the physical fate and dispersion of drill cuttings discharges at three drilling locations closest to Scott Reef, namely the TRE drill centre (previously named TOE, approximately 2 km from South Scott Reef), the TRD drill centre (previously named TOD, approximately 3 km from North Scott Reef) and the TRA/TRB drill centre (previously named TOA, approximately 7 km from North Scott Reef) (DHI 2011b) (Figure to Figure 10.15). In particular, the assessment focused on sedimentation impacts to coral habitats at Scott Reef to inform the management approach to be adopted during drilling. Although this assessment was undertaken in support of the previous development concept for the commercialisation of the Browse resources, the parameters used for the modelling, including drilling locations and volumes, are still representative of the proposed drilling activities required for the Browse FLNG Development. Modelling Parameters and Assumptions Modelling was undertaken using the calibrated and validated 3D hydrodynamic model (MIKE 3 Classic) for Scott Reef and surrounds to run the Lagrangian-based particle module for simulating sediment dispersion, sedimentation and resuspension of the drill cuttings releases. Although actual volumes, discharge rates and scheduling of drilling activities are yet to be confirmed at this stage of the development, modelling assumptions provided for a conservative assessment of potential impacts from drill cuttings disposal, including: For modelling purposes, it was assumed seven wells could be constructed in a year at TRD and six wells could be constructed in a year at TRE. At TRA/TRB, it was assumed 12 wells could be constructed in 18 months. These assumptions are conservative as it is likely only up to four wells could be constructed in a year at each location. This assumption resulted in higher intensity of cuttings discharge than is likely to occur under actual conditions. The model considers there are no intervals between the drilling of different well sections. This assumption resulted in higher intensity of cuttings discharge than is likely to occur in reality. The drill cuttings model was based on current data from October 2006 to September 2007, which was not an El Nino or La Nina period. Whether the model does or does not use current data from El Nino or La Nina periods would not change the model findings for seabed discharge since regional flows such as Indonesian Throughflow have virtually no influence on current velocities near the seabed. The PSD of cuttings adopted in the modelling was based on cuttings PSD measured from the Torosa-5 exploration well, which is expected to provide a good proxy of cuttings expected from the proposed drilling locations for the Browse FLNG Development.

55 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 213 At each drilling location, modelling parameters included: Seabed discharge from top hole sections of each well (Section 5) equivalent to a cuttings volume of 587 m 3. Sea surface discharge from bottom hole sections of each well (Section 5) equivalent to a cuttings volume of 181 m 3. Modelling Results The modelling indicated that, at all three drill centre locations, the sea surface discharge of drill cuttings from bottom hole sections of wells resulted in incursions of sediment plumes and associated increased deposition at some parts of North and South Scott Reef including within the lagoons. However, the seabed drill cuttings discharge from top hole sections of wells resulted in sediment plumes and associated deposition of sediment confined to the deep layers of the water column with no contact with deep or shallow water coral habitats at Scott Reef. Specifically, the modelling indicated: A seabed discharge of drill cuttings generated from the top hole sections of the wells at the TRE drill centre, in water depths of 360 m, would result in a sediment plume predominantly extending westward, driven by the stronger ebb tide, with some eastward extension during the flood tide (Figure 10.13). Cuttings sedimentation would be limited to the deep waters of the channel, with no sedimentation on Scott Reef coral habitats including in the lagoons of North and South Scott Reef. Maximum net sediment deposition over the duration of the 12 month drilling program is approximately 46 cm at the TRE drill centre (Figure 10.13). A seabed discharge of drill cuttings generated from the top hole sections of the wells at TRD drill centre, in water depths of 400 m, would result in a sediment plume confined to the deep water layers of the water column (Figure 10.14). Modelling did not predict elevated suspended sediment concentrations at Scott Reef coral habitats including in the lagoons. Over the modelled 12 months of drilling activities at TRD, the expected maximum drill cuttings discharge was not predicted to result in net sedimentation at Scott Reef coral habitats including the lagoons. Net sediment deposition over the duration of the drilling program is approximately 35 cm at the TRD drill centre (Figure 10.14). A seabed discharge of drill cuttings generated from the top hole sections of the wells at the TRA/TRB drill centre, in water depths of 460 m, was predicted to be confined to the deep water layers and was not expected to reach Scott Reef coral habitats including the lagoons (Figure 10.15). Sedimentation was predicted to extend eastwards of Scott Reef, influenced by the north-west-south-east tidally-induced currents. Net sediment deposition over the duration of the drilling program is approximately 21 cm at the TRA/TRB drill centre (Figure 10.15).

56 214 Browse FLNG Development Draft Environmental Impact Statement Figure 10.13: Drill Cuttings Discharge at the Seabed at TRE Drill Centre Showing: A. Maximum TSS Concentration (mg/l) in the Bottom 2 m and B. Maximum Net Sedimentation (mm) (DHI 2011b) Note: The contour plots illustrate the overall footprint of elevated suspended solid concentrations and sedimentation over the entire course of the drilling program (12 months) at TRE. It is important to note the occurrence of elevated TSS concentrations shown in the contour plots is not representative of the TSS at any one time, and are not continuous in nature. This approach allows for the prediction of any areas at Scott Reef where elevated turbidity or sedimentation may occur over the modelled drilling period.

57 Section 10 IMPACT ASSESSMENT AND RISK SIGNIFICANCE 215 Figure 10.14: Drill Cuttings Discharge at the Seabed at TRD Drill Centre Showing: A. Maximum TSS Concentration (mg/l) in the Bottom 2 m and B. Maximum Net Sedimentation (mm) (DHI 2011b) Note: The contour plots illustrate the overall footprint of elevated suspended solid concentrations and sedimentation over the entire course of the drilling program (12 months) at TRD. It is important to note the occurrence of elevated TSS concentrations shown in the contour plots is not representative of the TSS at any one time, and are not continuous in nature. This approach allows for the prediction of any areas at Scott Reef where elevated turbidity or sedimentation may occur over the modelled drilling period.