Establish a 2/10 MW+ pilot project in the Darwin area supported by a tropical tidal research and testing facility, as the core components of a technology and industry development and commercialisation accelerator strategy which will enable the construction of a commercial-scale tidal power station of initially 30-50 MW by 2030 and subsequently drive the development of the full field capacity of over 450 MW by 2050 as energy storage and transfer technology develops.
The Clarence Strait Tidal Energy Project is to be located in the deep water channels of the Clarence Strait. Clarence Strait is a narrow body of water in the vicinity of the Vernon Islands, approximately 50 km north of Darwin in Australia’s Northern Territory and south of Melville Island, Tiwi Islands. It links the Beagle Gulf in the west with the Van Diemen Gulf in the east.
Tenax Energy submitted an EPBC referral for the Clarence Strait resource. The project has been subsequently classified as a Controlled Action to be assessed by the Northern Territory under a bilateral agreement with the Commonwealth. A Notice Of Intent has been submitted and a Licence to Occupy and Guidelines for the preparation of the EIS have thence been issued.
Complete environmental monitoring and establish a 2/10 MW+ test centre as a pilot project between 2020 and 2025. Construction of a commercial-scale tidal power station of initially 30-50 MW by 2030 and subsequently full field capacity of over 450 MW by 2050.
Key Environmental Issues
To extend the current research programs located in temperate climates into tropical conditions more typically found in Asia Pacific and equatorial countries within a dual research and commercial framework.
On the 18 December 2008 the Proponent submitted a Notice of Intent for the Project for assessment under the Northern Territory (NT) Environmental Assessment Act 1982 (EA Act). On 12 September 2009 the Northern Territory Minister for Natural Resources, Environment and Heritage (the Minister) determined that the Project required formal assessment under the EA Act at the level of an Environmental Impact Statement (EIS). Issues of concern contributing to this decision included:
- The technology is relatively new and environmental impacts are largely unknown or potentially significant;
- Potential impacts to marine species including coral reef communities;
- A number of rare and threatened species and listed migratory species and communities occur in the proposal’s impact area;
- The area provides important feeding grounds for sea turtles and dugong and consequently may be important to the traditional owners of the region;
- Disturbance of seabed impacting the erosion, transportation and deposition of sediments;
- Potential impacts to recreational and tourism activities in the area;
- Potential impacts to local and international shipping needs in the area;
- Potential disturbance to maritime heritage and Aboriginal cultural heritage; and EIS Guidelines – July 2013 Clarence Strait Tidal Energy Project – Tenax Energy 4
- Potential impacts to water quality from material inputs such as antifouling treatments.
Baseline Assessment: Clarence Strait Tidal Energy Project
|Receptor||Study Description||Design and Methods||Results||Status|
|Birds, Fish, Reptiles||Describe the extent and behavior of vertebrate marine species in and around the project in particular sea turtles, dugongs, bird species, fish species (e.g. Narrow-barred Spanish mackerel, Scomberomorus commerson, sharks and rays) and cetaceans (e.g. Indo-Pacific humpback dolphins Sousa chinensis, Australian snubfin Oraella heinsohni).||NA||NA||Planned|
|Physical Environment||Provide maps and interpret the bathymetry of the turbine project area and along the cable route to identify any seabed features of significance.||NA||NA||Planned|
|Physical Environment, Sediment Transport||Discuss the soil/sediment types and land units within the onshore project footprint including actual and potential acid sulphate soils and existing levels of erosion and other disturbances.||NA||NA||Planned|
|Physical Environment, Water Quality||Describe water quality of marine waters including temporal and spatial variations.||NA||NA||Planned|
|Human Dimensions, Environmental Impact Assessment, Legal & Policy||Describe floral & faunal species (including exotic/pest species) and biological communities including those of local, regional and national significance and listed migratory species that are found within and around the project area (including the wider area of Tiwi Islands, Shoal Bay and Van Dieman Gulf).||NA||NA||Planned|
|Physical Environment||Describe in detail, species’ important habitats (including for breeding, foraging and migration paths), including maps of regional distribution of suitable habitat, and of habitat within the proposed development area that clearly identifies areas to be disturbed from development infrastructure.||NA||NA||Planned|
|Bats, Physical Environment, Terrestrial Mammals||Describe and map native terrestrial and inter-tidal flora and fauna for the proposed onshore cable route and infrastructure.||NA||NA||Planned|
|Human Dimensions, Navigation||Describe the existing and projected maritime traffic use of the proposed project area.||NA||NA||Planned|
|Human Dimensions||Describe the isolated danger or safety zones required to adequately mark and protect marine turbines and cable routes in the project area.||Consult with the Marine Safety Branch to determine device marking requirements.||NA||Planned|
|Human Dimensions, Social & Economic Data||Identification of importance and vulnerability of features identified.||Conduct a detailed, physical maritime survey (eg remote sensing and ground truthing). Conduct an archaeological/heritage survey in the onshore area of the project.||NA||Planned|
|Human Dimensions||Detail all chemicals, including fuels, to be stored and/or used on the project site. Outline the proposed methods for transportation, storage and use of these substances.||NA||NA||Planned|
|Marine Mammals||Assessing physical interaction risk of tidal turbines.||Literature review for notice of intent.||The turbines have been designed to minimise any physical interaction with marine species as there is a 5 m gap in the centre of the turbine, the tips are enclosed within the outer rim and the turbine spins slowly (up to 10 RPM). There is a risk of encounters between marine biota and turbine blades. Encounters only lead to collisions when the animal does not take appropriate evasive action. The behavioural reactions of fish and mammals to marine turbines requires further assessment – it will depend on the sensory systems and agility of the species at risk; the visual, acoustic or other environmental signatures of the device; and background conditions (Wilson et al, 2007). Appropriate mitigation options will depend on the specific design, species at risk and local environment. It is reasonable to expect that species that can negotiate rapid currents are highly agile and readily able to avoid obstacles. ||Completed|
|Marine Mammals||Understanding acoustic interference and impact of device noise.||Literature review for notice of intent.||The operation of the turbines is predicted to create noise, mainly moving water noise and mechanical noise. The levels of anthropogenic noise produced by similar tidal stream devices has been found to exceed background noise in areas of low current speed, however “tidal devices will necessarily be sited in locations with strong tidal flows, and the ambient noise associated with these currents (e.g. sediment transport noise) could be significant, reducing the impact of the device noise” (Richards et al, 2007). Further, to minimise noise from the device the turbines have only one moving part, and as the turbines will spin relatively slowly (up to a maximum of 10 RPM), it is expected that noise will be of a low level and far less than boat propellers. |
Noise during construction is expected to be minimal and temporary, and therefore is unlikely to impact on marine species.
|Invertebrates||Impacts of cables on benthic habitat.||Baseline study to be conducted.||The corresponding cable corridor will affect an area of approximately 2.3 ha (refer to Section 3.2.2). Baseline studies will be conducted for the entire project area to determine the location of significant benthic habitat. The individual turbines will then be sited so as to avoid any areas of significant benthic habitat.||Planned|
|Physical Environment||Impacts of gravity base on seabed.||Literature review for notice of intent.||The installation of the gravity base will result in disturbance of the seabed. The physical footprint of each individual turbine is limited to the footprint of the four pylons (approximately 7 m2 ). Based on this area, 456 proposed turbines will have a direct physical footprint of approximately 3192 m2 . (0.32 ha) The weight of the gravity base and turbine is likely to disturb the seabed by smothering epibenthic biota immediately beneath the pylons of the gravity base.||Planned|
|Human Dimensions||Understanding of cultural impacts.||Cultural review.||Aboriginal Cultural Heritage: A native title claim is active over all Vernon Islands from the Larrakia and Jampalampi Tiwi Groups; however this claim is to the low water mark and as such, the turbine area and corresponding cables are not within this claim. |
Non Aboriginal Cultural Heritage: Shipwrecks (including a known submarine wreck at the western entrance of the Clarence Strait) (Lewis, 1997) are presumed to occur within the vicinity for the preferred location for the proposed development. A detailed survey to determine the location of any of these wrecks within the proposed development area should be undertaken as the precise locations of the shipwrecks are not readily available on either the Northern Territory Government or the Commonwealth Government historic shipwrecks database websites.
Post-Installation Monitoring: Clarence Strait Tidal Energy Project
|Stressor||Receptor||Study Description||Design and Methods||Results||Status|
|Collision||Birds, Fish, Marine Mammals||Discuss measures to minimize identified impacts on species.||NA||NA||Not yet planned|
|Habitat Change||Invertebrates||Survey invertebrates and biofouling. Detail use of responsible antifoulant compounds, or other antifoulant methods such as smooth surface or regular removal/cleaning of devices.||NA||NA||Not yet planned|
|Changes in Flow||Physical Environment, Sediment Transport||Conduct a coastal erosion risk assessment of the shore crossing and any on-shore infrastructure.||NA||NA||Not yet planned|
|Human Dimensions, Social & Economic Data||Detail measures to mitigate impacts to any historic and cultural features at risk from the project.||NA||NA||Not yet planned|
|Human Dimensions, Navigation||Describe measures to minimize the impacts on local and international shipping users.||NA||NA||Not yet planned|