Map of Temporary Geophysical Survey Restricted Access Area (November 2024)
A new round of marine geophysical surveys commenced this month for Westport, a crucial step in planning for the proposed port facilitates in Kwinana. The surveys will gather necessary information about Cockburn Sound, building on data collected during the geophysical surveys completed last year.
Geophysical surveys will generate spatial maps of the seafloor and sections of the sub-seafloor within the footprint of the proposed port facilities in Cockburn Sound and up through Gage Roads, where the proposed navigation channel will traverse. Information gathered can help us better understand:
- Topography
- Benthic habitat
- Geology and geological structures
- Magnetic and density properties
A better understanding of the seafloor and what lies beneath it will allow Westport to progress more detailed design and planning activities, as well as provide input to Westport’s State and Commonwealth environmental impact assessments.
Geophysical surveys help plan marine infrastructure projects but can also lead to interesting and unexpected finds, like the sunken sailboat found nearly two kilometres off the coast of Naval Base beach in 2023 which was never previously recorded or reported.
Some geophysical surveys can cause underwater noise above levels recommended for divers and swimmers, so best practice processes are in place to limit human interactions with survey vessels and equipment. Surveys will also implement processes to manage interactions with marine fauna and minimise any potential disturbance.
Diving and swimming restrictions at Naval Base “Horse Beach” in Kwinana Industrial Area
Naval Base beach, accessed via Riseley Road and Barter Road in the Kwinana Industrial Area, known as the Naval Base horse beach, is within a buffer zone for the geophysical surveys.
Underwater (submerged) activities at Naval Base beach are prohibited during day light hours Monday – Saturday between Monday 4 to Saturday 16 November 2024 (inclusive). Underwater activities prohibited during this time include:
- Swimming
- Snorkelling
- Diving
There are no restrictions to shallow water horse-riding activities such as walking horses in the water. There are no restrictions to above surface activities like boating, sailing, kayaking etc.
There are no restrictions or beach closures at public beaches in Cockburn Sound, such as Challenger Beach and East Rockingham beaches.
FAQs
What are geophysical surveys?
Geophysical surveys are a non-intrusive method of mapping the characteristics of the seafloor and sub-seafloor. Some of the surveys being used work by emitting a sound through the water and using equipment to record how this sound is refracted on and through the seafloor. Other surveys use magnetometers and gravimeters to measure changes in the magnetic and density properties of the seafloor.
What can I expect to see during the surveys?
During geophysical survey acquisition, a nine-metre boat will be moving slowly in straight passes along the water.
Vessels will have a crew of up to four people including a coxswain, two geophysicists and a marine mammal observer.
When will the surveys be completed?
The surveys will commence in October 2024 and are expected to be completed by late December 2024, with a contingency period extending to January 2025.
How are interactions with marine life being managed?
A range of strategies have been put in place to manage interactions with marine fauna and minimise any potential disturbance. An environmental management plan was developed, and field testing of survey equipment noise was undertaken to confirm planning assumptions.
Strategies include using a single seismic source powered down to generate only enough sound to survey up to 40m below the seafloor and using a soft-start procedure where equipment will be powered on over a 30-minute period.
Geophysical surveys comply with the Environmental Protection and Biodiversity Conservation Act, Policy Statement 2.1 – Interaction between offshore seismic exploration and whales.
All surveys generating sound will have a certified marine mammal observer on board vessels to look out for marine mammals and if any are spotted, the surveys will stop until they have moved on.
More information
If you have questions or would like to discuss this information, please contact us on 1800 875 000 or at enquiries@westport.wa.gov.au.
