The proposed action to be undertaken by Gippsland Skies Pty Ltd (Gippsland Skies) is marine survey investigations (‘the investigations’) including supporting activities, to support the proposed future development of the Gippsland Skies Offshore Wind Project (the ‘Project’) offshore, off west Gippsland, Victoria.

The investigations, including supporting activities, are required to provide baseline data for future environmental impact assessments for the Project. The referral area for the proposed action shown in Section 2.1 and comprises the feasibility licence area (FLA), proposed cable corridor (137km long) and a 1nm buffer area around the FLA (the ‘investigation area’). The investigation area is approximately 2,200 km2, of which approximately 107 km2 is the buffer area for the purpose of vessel manoeuvring around the FLA. The disturbance footprint of the geophysical investigation area will be less than 2,200 km2, noting that in the case of geophysical investigations, ‘footprint’ refers only to area traversed and the proposed cable route survey area will be refined prior to the survey commencing. For the benthic and geotechnical investigations, the disturbance footprint is estimated to be 0.004 km2 (0.2 ha), the calculations for which are outlined in Attachment 1 ‘Gippsland Skies Offshore Wind Project EPBC Act Referral Supporting Materials’, Section 3.1.3, page 25.

The investigations will include geophysical and geotechnical investigations, benthic habitat surveys and wind and oceanography surveys.

Geophysical investigations

The geophysical investigations will collect data for assessment of water depths, seabed topography, seabed and shallow sub-seabed conditions and identification of obstructions on the seabed. The data will inform the geotechnical investigations and environmental assessment and engineering design for the Project. The geophysical investigations are proposed to take place over three campaigns:

• Campaign 1 – proposed to commence Q4-2024/Q1-2025 subject to receipt of necessary approvals, finalisation of contracting arrangements, weather and vessel availability. Survey of the entire investigation area with indicative line spacing of 100-150 m and cross lines spaced 2 km apart (subject to optimisation). It is expected to take approximately 8-11 weeks, subject to weather. Cable corridor area to be refined prior to survey. 
• Campaign 2 – notionally proposed to commence in approximately 2027 and take 2-3 weeks (weather dependent). It will undertake detailed surveying and tighter spaced survey lines over proposed locations of wind turbine generators (WTGs), offshore substation platforms (OSPs) and inter-array cables.
• Campaign 3 - notionally proposed to commence in 2028 or 2029, will take up to four to six weeks (weather dependent) and will be a pre-construction survey to refine the location of all proposed infrastructure.

The following geophysical activities are proposed (a detailed description is provided in Attachment 1 ‘Gippsland Skies Offshore Wind Project EPBC Act Referral Supporting Materials’, Section 3.1.2, pages 14-25):

• Multibeam echosounder (MBES)
• Side scan sonar (SSS)
• Sub-bottom profiling (SBP)
• Magnetometry surveys
• 2D shallow seismic (i.e. Mini air guns. Use of this equipment is subject to the results of the SBP and is likely only to be required in deeper water and particular geology conditions).

Geotechnical investigations

Geotechnical investigations collect detailed information on the physical properties of the seabed and the underlying shallow sediments to supplement and validate the data gathered from the geophysical surveys. This will provide key data to assist with selecting the locations for the WTGs, OSPs and development of foundation designs. Most of the samples collected will be transported to an onshore laboratory for testing. Some initial geotechnical testing will be performed on the geotechnical vessel. The geotechnical investigations are proposed to take place over three campaigns:

• Campaign 1 – proposed to commence in 2025, subject to vessel availability. These preliminary investigations will take place across the investigation area and likely to take two to three months to complete, subject to weather
• Campaign 2 – likely to be split into three phases during 2027 and/or 2028, involving more detailed geotechnical investigations to inform project development. There is the potential for the second and third campaign to be condensed into one campaign. 
• Campaign 3 – are proposed to commence in 2029 for Phase 1 project and between 2029 and 2032 for all three phases, and likely to involve taking one borehole sample and one downhole cone penetration test (CPT) sample at each of the proposed WTG locations. The horizontal directional drilling exit pit location will be subject to borehole and CPT sampling in this campaign. 

The following geotechnical activities are proposed (a detailed description is provided in Attachment 1 ‘Gippsland Skies Offshore Wind Project EPBC Act Referral Supporting Materials’, Section 3.1.3, pages 25-35): 

• Seabed grab sampling
• Coring (including vibro coring, box coring or piston (or gravity) coring) 
• CPTs
• Standard penetration tests (SPT)
• Seabed sediment thermal conductivity testing 
• Borehole sampling 

Benthic habitat surveys

Boat-based benthic habitat surveys will be undertaken to develop an understanding of seafloor habitat characteristics and characterise grain type and any possible contaminants within seabed sediments. The surveys will be designed using desktop information and site-specific geophysical data. The number of samples required will be confirmed once geophysical survey data is available. Benthic survey techniques are likely to include benthic grab samples, drop down camera and drop-down video, and an intertidal walkover survey.

Wind and oceanography surveys

Data on wind speeds, ocean currents and wave heights will be collected using Floating LiDAR Systems (FLS), wave measuring buoys, and Acoustic Doppler Current Profilers (ADCP). Two FLS will be deployed in the FLA for the purpose of measuring wind speed and direction. Deployment locations have not yet been finalised for wave buoys, but FLS are notionally set to be located at 39.446712624°S and 146.157896417°E; 39.569548170° S and 146.155003589°E. These will be fixed to the seabed with cabling and an anchor/ballast weight or mooring. 

ADCPs will be deployed to measure the water current velocities within the FLA and at points along the proposed cable corridor using the doppler effect of sound waves to measure the speed and direction of currents. These could be deployed either on fixed buoys or from Unmanned Autonomous Vessels (UAV). If fixed, equipment will be located on the seabed in a trawl-resistant frame (mooring cage).

A detailed description of the surveys is provided in Attachment 1 ‘Gippsland Skies Offshore Wind Project EPBC Act Referral Supporting Materials’, Section 3.3.2 pages 38-46).

The following activities will also be carried out in parallel with the investigations and are referenced for completeness but do not form part of the proposed action that is the subject of this referral: 

• Passive acoustic monitoring surveys
• Water and sediment quality sampling
• Biological surveys (i.e. aerial surveys for birds and marine megafauna and supporting observational surveys, baited remote underwater video surveys for fish, towed camera surveys for fish and shellfish and e-dna sampling).

A detailed description of these surveys is provided in Attachment 1 ‘Gippsland Skies Offshore Wind Project EPBC Act Referral Supporting Materials’, Sections 3.4, 3.5 and 3.6, pages 43- 48).

There are several sources of environmental impacts and risks associated with the investigations, however the potential for them to cause significant environmental harm is considered minor. Potential impacts from the investigations are discussed in detail in Attachment 1 ‘Gippsland Skies Offshore Wind Project EPBC Act Referral Supporting Materials’, Sections 7,8,9 pages 102-139). The main potential impacts are summarised below: 

• Underwater sound from geophysical and geotechnical equipment and vessels that may disturb marine fauna
• Entanglement of marine fauna in towed equipment
• Vessel collision with megafauna
• Seabed disturbance
• Marine pollution from a vessel hydrocarbon spill or accidental release of waste
• Introduction of invasive marine species to the marine environment.

Environmental protection measures that will be implemented to ensure the investigations are undertaken in a manner that does not cause environmental harm are provided in Attachment 1 ‘Gippsland Skies Offshore Wind Project EPBC Act Referral Supporting Materials’, Sections 7.1 – 7.9 and Section 8, pages 102-125.