CGG Services (Australia) Pty Ltd (CGG) proposes to acquire a multi-client 3D marine seismic survey (MSS) in the Gippsland Basin offshore Victoria. The Gippsland MSS is located in Commonwealth waters approximately 13 km east of Victorian mainland at its closest point, extending out to deep offshore waters approximately 125 km offshore. The Gippsland MSS comprises acquisition of seismic data in an Acquisition Area of a maximum area of 11, 161 km2, within a larger Operational Area of approximately 13,421 km2. The water depths within the acquisition area range from a minimum of approximately 43 m offshore from Ninety Mile Beach to 3,345 m in the Bass Canyon. The operational area is for sail line run-ins and run-outs (required to obtain full coverage), soft starts, streamer deployment / retrieval and maintenance, and line turns. 
The Gippsland MSS comprises 5 zones, each taking a maximum of one month to complete. Each zone is numbered and the order of acquisition will be determined based on advice from the CGG Gippsland MSS Scientific Advisory Committee, with the order arranged so as to minimise impacts to fishing operations, sensitive receptors such as migrating whales and spawning fish. The orientation of the survey sail lines in each zone are aligned ESE and WNW directions.
The seismic survey vessel will traverse a series of pre-determined sail lines within the acquisition area at a speed of approximately 4.5 to 5 knots. The source array will have maximum volume of 3,000 cubic inches which will be reduced to <150 cubic inches over South East Reef due to its importance for commercially important fish and invertebrate species as identified from stakeholder consultation. The sub-arrays will be fired alternately, with a shot point interval of 12.5 m. The seismic vessel will tow 8 to 12 solid streamers, with a maximum length of 7,050 m. Streamer spacing will be 50 to 100 m and sail lines will be spaced 450 to 1,000 m apart. The source array will be towed at approximately 6 m below the sea surface, and streamer tow depth will be 6 to 18 m. Undershooting may be undertaken over a 25 km by 3 km area around a number of platforms within the survey area (up to ten platforms depending on client requirements). During undershooting, a secondary vessel with a similar seismic source will be positioned parallel to the main survey vessel. Each source will fire every 50 m, alternating between the two source vessels, so there is still 12.5 m between shot points, i.e. the vessels will not be firing simultaneously. Hence the amount of sound being produced is the same as for conventional data acquisition. Each undershoot will take between 18 and 54 hours. The commencement date of the Gippsland MSS is yet to be decided. The duration of the activity is a maximum of 6.5 months and will be conducted between early March 2019 and end of July 2020, with avoidance of the period from beginning of August to the end of December. The 6.5 month duration is a conservative estimate and allows for some downtime due to weather, avoiding conflicts with other users and marine megafauna, and maintenance.