MYUNA SURVEY PROGRAMME
Frequently asked questions
What is a seismic survey?
A seismic survey is a form of geotechnical profiling.
Centennial’s Myuna Colliery is planning to conduct profiling of the lake floor. The sub-bottom profiling survey helps to map what the bottom of the lake looks like to determine the distance between mine workings and the lake floor.
The lake sub-bottom profiling is a similar method to what is used in the Swansea Channel dredging programme.
Are you using seismic airgun blasting?
No. Seismic airgun blasting, as claimed by Save Our Coast is NOT being used by Centennial.
What are sub-bottom profiling or hydrographic surveys?
Sub-bottom profiling or hydrographic surveys are standard geotechnical survey techniques used worldwide and are used in Lake Macquarie.
NSW Maritime (Transport for NSW) use a similar survey method to monitor how the changing lakebed impacts on boat navigation in Swansea Channel. It is used in Newcastle and Sydney harbours to assess water depth for dredging.
Similar technologies are also used by marine scientists in sensitive marine environments, such as the Great Barrier Reef, to develop maps used to model ocean currents, storm surge inundation and better understand ecosystem and biodiversity patterns on the seabed. These types of maps are widely used across all marine environments.
Sub-bottom profiling is a low impact survey method which uses a small boat towing survey equipment called a Sparker. Sound pulses bounce off the lake floor to help map the topography and composition of the lake floor.
Does sub-bottom profiling impact on the environment or sea life?
No. To undertake a shallow marine survey, equipment is towed behind a boat and is used to map a detailed profile of the lake-floor and sediment. The technology proposed is similar to a sonar depth finder on a boat.
This survey work has no material environmental impacts below the surface on marine life.
What additional precautions will you take?
A visual observation for marine mammals and sea turtles is undertaken prior to any work commencing in the area, and if survey work is already underway and a marine mammals and/or sea turtles are detected the Sparker is suspended.
Why is Centennial doing the survey?
Centennial’s Myuna is conducting a survey programme to accurately map the lake floor to maintain the ongoing safety of our mineworkers and to better understand the strata above our mine workings to provide a safe workplace for our people.
Centennial’s Myuna Colliery has been mining under Lake Macquarie for 40 years. To do this safely, Myuna needs to maintain a safe distance between the bottom of the lake and mine workings.
The survey was delayed until after the summer school holidays to reduce the inconvenience to water users.
Who did you notify?
A number of methods were used to notify stakeholders and the community of the upcoming survey. These included letters to community groups (regular lake users), Lake Macquarie City Council and an advertisement in the Lakes Mail in January.
These activities were proactively undertaken by Centennial to inform stakeholders and the community of the work and were part of our normal communications with our community.
Why was there a lack of consultation?
The survey is an integral part of understanding mining conditions, with ALL planned activities permitted under current mining approvals and landowner consent (Crown Lands) obtained.
While not a requirement, notifications were published in the Lakes Mail and information provided to the Myuna Community Consultative Committee, Lake Macquarie City Council and local community groups which is part of our normal communications with our community.
We understand the words used to describe the survey have caused some confusion and angst in the community and apologise for the concerns raised. We will endeavour to better describe planned works and more clearly explain these plans to stakeholders and community members going forward.
Why does the Review of Environmental Factors (REF) have conflicting information and list a different survey methodology?
The method for surveying the lakebed was changed making the seismic airgun blasting part of the document redundant.
Originally, a small airgun blasting technique was proposed, (much smaller scale than offshore methods of seismic blasting). However, after consideration, Myuna determined that the sub-bottom profiling method now being proposed is both safer and has NO material impacts below the surface on marine life.
Will the survey impact on fish breeding areas?
No. The survey will not impact fish habitats including sea grass areas.
The Lake is too sensitive for this type of survey
The sub-bottom profiling survey method proposed by Centennial’s Myuna Colliery is being used because it is a low impact method of understanding the lakebed.
It is a standard geotechnical survey technique used in waterways like Lake Macquarie, Newcastle harbour and Sydney harbour to assess water depth for dredging and monitoring safe maritime navigation.
Seismic airgun blasting – blasts of air through the water and into the bottom of the water sources (ocean, lake)
Sparker survey - is a low impact pulse generated by an electric spark
Sub-bottom profiling – a type of sonar technology used to image sub-surface features in an aquatic environment
Hydrographic survey – produces detailed plans of seabeds, harbours and waterways
How do I keep up to date on the work?
To contact the community liaison team, Phone: 02 4970 0263
4 February 2020
Myuna Survey Fact Sheet - click here.