Beach Energy (Operations) Limited (Beach), propose to undertake a geophysical and geotechnical seabed assessment (seabed assessment) within the Rockhopper (T/RL3), Trefoil (T/RL2) and Yolla (T/L1) permits and open acreage within the Bass Strait in Commonwealth waters. The seabed assessment operational area is approximately 126 km from Wonthaggi, Victoria and 94 km from Stanley, Tasmania.

The seabed assessment consists of a geophysical survey and geotechnical survey and is part of the evaluation of a potential development of the Trefoil and Rockhopper fields and is required to determine the placement of a rig for the future drilling of a well within the Trefoil field and for surveying a potential pipeline tieback route to the Yolla platform.

The geophysical survey and geotechnical survey will potentially be undertaken separately and take up to 25 days and 55 day, respectively, between April 2020 and 31 December 2021. Timings of the surveys is contingent on the availability of suitable vessels, weather and the receipt of required environmental approvals
The seabed assessment consists of:
• geophysical survey to collect bathymetry data and detect seabed hazards using:
- multibeam echo sounder
- side-scan sonar
- sub-bottom profiler
- magnetometer
• geotechnical survey to collect information on the properties of the seabed and the underlying shallow sediments using:
- borehole sampling
- core sampling
- piezo cone penetrometer test

The seabed assessment area refers to the area where the geophysical and geotechnical surveys will be undertaken. This will cover a 6 km x 6 km area over the proposed well location and a 1 km x 40 km corridor from the proposed well location to the Yolla platform and has an area of 68.32 km2. As the well location has not yet been finalised the seabed assessment area will be within the operational area which covers 552 km2 Water depths within the operational area range from 64 m– 82 m.