"In addition, a single validation monitoring during early operations is all that is required to characterize the low predicted levels of magnetic and electric fields, and thermal fields generated by the cables" (BPL 2.2.2).
The single validation monitoring described above would be a complete waste of time - the data would be insignificant without a baseline.
After consultation with AGSO I would recommend the following magnetic field monitoring procedure:
Airborne magnetic surveys should be conducted using a magnetometer. Traverse lines should be at right angles to the cable. A baseline survey should be conducted in the pre-construction phase. The follow up surveys have to be along the same traverses - this is fairly easy these days to a reasonable degree of accuracy thanks to real time differential GPS navigation.
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I fully support the Panel’s Draft Recommendations 8 and 9, concerning the implementation of a Bass Strait Environmental Review Committee as well as the modifications to the Strategic Environmental Management Plan to incorporate an extensive monitoring and research program to investigate the impacts of magnetic fields on cetaceans.
A proviso should be included in the strategic EMP and in Basslink’s commitments to the effect that:
Should the magnetic fields be significantly larger than predicted, or should there be reason for concern about magnetic field impacts on cetaceans, then the cable should be shut down until such time as the situation is rectified.
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Precautionary Principle
I fully support the following approach, regarding potential impacts of magnetic fields on cetaceans. A change of technology to an IRC conductor or twinned bipolar configuration would be the best way to mitigate magnetic field impacts on cetaceans.
"A number of unresolved concerns with regards to impacts on marine fauna are expected to remain in the foreseeable future. Underlying causes associated with monopole technology can only partly be mitigated by actions such as choice of trajectory and depth of burial. In these instances the Precautionary Principle should be applied, and the potential impacts should be weighted against assumed benefits and economic considerations" (Brown and Root Report, section 10.4.4).
As far as the safety of cetaceans is concerned, the proposed ‘monopole with metallic return’ technology is not considered acceptable due to potential residual magnetic field impacts.
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Heezen, B.C. (1957). Whales entangled in deep sea cables. Deep-Sea Research 4:105-115
Kirschvink, J.L., Dizon, A.E. and Westphal, J.A. (1986). Evidence from strandings for geomagnetic sensitivity in cetaceans. J. Exp. Biol. 120: 1-24.
Klinowska, M. (1985). Cetacean stranding sites relate to geomagnetic topography. Aquatic Mammals 11: 27-32.
Koops, F.B.J. (2000). Electric and Magnetic Fields in consequence of undersea power cables. In: Effects of Electromagnetic Fields on the Living Environment. Proceedings International Seminar on Effects of Electromagnetic Fields on the Living Environment Ismaning, Germany October 4 and 5, 1999. Edited by Matthes R., Bernhardt J.H., and Repacholi, M.H., International Commission on Non-Ionizing Radiation Protection, 2000, pp. 189-210.
Koschinski, S. (2002). Current knowledge on harbour porpoises (Phocoena phocoena) in the Baltic Sea. Opelia 55(3):167-197.
Nicol, D.J. (1991). The Tasmanian Stranding Record: A review of the cetacean strandings in Tasmanian waters and an examination of possible causes. University of Tasmania, Unpublished Thesis.
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Integrated Return Conductor (IRC) Technology
From: <Georg.Balog@nexans.com>
To: <antareon@...
Cc: <Bjorn.Sisselberg@nexans.com>
Sent: Wednesday, April 17, 2002 5:56 PM
Subject: HVDC Cables with metallic return system
Dear Antara May
We have introduced a new type of HVDC cable, where the return conductor is integrated into the cable itself, for monopolar operation. In this design the return conductor is laid co-axially around the cable core and insulated from the surrounding by a plastic sheath. As the current in the return conductor is identical to the current in the center conductor, but flows in the opposite direction, the magnetic fields generated by the two currents cancel each other out. This design was implemented on the Moyle, (Northern Ireland -Scotland) project, put into operation as per December 1 2001. This design will of course also do away with the need for the electrode systems. At one end the return conductor is earthed to ensure that the system potential is not floating with regard to earth. This potential earthing does not conduct any current in operation. The length of the Moyle cables is 63 km.
The IRC type of cable is a metallic return that is integrated into the main cable. The advantages are as follows:
1. No outer magnetic field, as described above. Even bundled, the separate HVDC and metallic return cables have a small but definite magnetic field.
2. Weighs less than separate HVDC and metallic return cables.
3. Circular design, can be handled as a normal circular cable, i.e. there is no need for two separate laying campaigns or to bundle two dissimilar cables.
4. It cost less to protect one cable than two cables.
5. As the copper cross-section is larger in the IRC cable than for the two separate cables, the losses are lower.
6. The converter system for monopolar transmission cost appreciably less than the bi-polar converters for the same power.
In most other regards the two types of metallic return has the same properties, as none of them needs a electrode system.
As electrode systems are costly and difficult to get acceptance for because of stray currents leading to corrosion and because of environmental concerns, short route length crossings, up to approximately 150 - 300 km, will be advantageous with metallic return system.
The limits of cables with IRC:
1. We have developed the HVDC cable type to 500 kV level and certified it for 800 MW power transmission capacity at 500 m laying depth according to the CIGRE recommendations. Based on this we expect to be able to supply 1000 MW cable with IRC. The Moyle cable is 250 kV, 250 MW.
2. The IRC system in itself has no length limitation. However, as the return conductor is insulated there will be a standing voltage on the cable that has a maximum at the un-earthed end. The Moyle type of IRC insulation is viable to approximately 200 km length, and for longer lengths it requires a rapidly increasing IRC cross-section, so in it´s present form it is not viable for lengths above 300 km. However, with further development the above limits may be removed.
For large power transmission, 1000 MW and above and for some type of transmission system requiring it, the bi-polar system is the only alternative. The Voltage Source Converter system from ABB requires bi-polar transmission and has at present maximum voltage 150 kV and transmission capacity 330 MW. When the two cables are laid close together or bundled there will be a small magnetic field, just as from bundled HVDC and metallic return cables. We have patented, but not yet developed, a concept with a coaxial bi-polar cable where the two conductors and insulations were integrated. This design would eliminate the external magnetic field just as in the IRC. However, this concept is not viable for higher voltages as the voltage between the center conductor and the second conductor is twice the nominal voltage to earth requiring large insulation thickness.
In case of large transmission capacities two cables are needed. To reduce the risk of loosing all transmission capacity at once these cables are usually spaced 500 to 1000 m apart and electrodes are established so one of the cables may transmit until the other pole is repaired. Of course for short routes the use of two cable with IRC may be advantegeous instead of electrodes.
I hope this gives you a feeling for the possibilities. If you have questions please contact Nexans Norway for an eventual study.
With regards
Georg Balog
Competence Centre Manager
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From: <Domenico.Gerace@nexans.com>
To: <antareon@...
Cc: <Georg.Balog@nexans.com>; <Kjell.Bjorlow-Larsen@nexans.com>; <Jan.Stensrud@nexans.com>
Sent: Wednesday, April 24, 2002 4:00 PM
Subject: Bass link - HVDC cable with integrated return conductor
After studying the technical solution with the above cable design, Nexans confirms that it could be applied to the project in question. Nexans has however no knowledge of the economics that currently govern the proposed conventional solution with a separate return conductor for the project in question.
We apologise for the late answer but hope to have been of assistance.
Regards,
Domeni Gerace
Export Sales Manager
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Information on the NorNed Cable, supplied by KEMA:
(KEMA is the Dutch consulting firm employed by the proponents of NorNed – their equivalent of NSR)
The NorNed cable is a 400 kV, 600 MW bipolar cable. It has two conductors, one for the energy current and one for the return current, together in one cable. It is a cable connection without sea electrodes. The magnetic field from the energy current is compensated by the magnetic field of the return current. The compensation depends on the distance between the two conductors. In the NorNed cable this distance is about 9 cm. On the seabed, about 1 m above the buried cable, the magnetic field will be 28,7 µT and 3 m above the seabed 1,8 µT. The electric field of the cable will be screened by the metal sheaths of the cable, but water moving through a magnetic field will generate an electric field. The mean natural electric field in the North Sea by water currents through the geomagnetic field is 10 µV/m with maximum 25 to 35 µV/m in strong tide currents. The extra electric field by water currents through the magnetic field above the NorNed cable will be on the seabed 8 µV/m, on 1 m above the seabed 2 µV/m and on 3 m above the seabed 0,5 µV/m. If the water currents through Bass Strait are stronger than in the North Sea, the electric field strength near the cable will be proportionally more. The total of the natural electric field and the electric field by the cable depends on the direction of the natural and artificial magnetic field and the direction of the water currents. Effects on sea animals, movements of sharks and whales are not to be expected. Any possible effect on these animals close near the cable will be disappear on a distance of some metres from the cable.
On the surface of the seabed the heat is released to the water and is too low to give a discernible rise in water temperature above the seabed. So the heat production has no effect on the epifauna, the benthic fauna on the seabed. Attraction of fish to the cable by a temperature increase of the seawater above the cable is not to be expected. Most benthic infauna lives in the top layer up to 30 cm depth. The heat in the seabed depends on the thermal resistance of the seabed, depending on the composition of the seabed. In a sandy seabed the temperature increase on 30 cm depth will be no more than 1.2 K and in a muddy seabed about 3 K.
The distance between the main cable and the return cable of the cable through Bass Strait is possibly some more than the 9 cm of the NorNed cable. With some more distance between the main cable and the return cable, the magnetic field will be a little more than near the NorNed cable, but I think the difference will be small.
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KOSCHINSKI, SVEN.
OPHELIA 55(3):167-197. 2002.
Current knowledge on harbour porpoises (Phocoena phocoena) in the Baltic Sea.
*D-24326, Nehmten-Sepel, Germany.
Abstract:
Concern has been raised about the long-term viability of the harbour porpoise population in the Baltic Sea. By-catch at possibly unsustainable levels, contaminants, overfishing of prey species and disturbance have been identified as possible threats. This literature study summarises the current knowledge about harbour porpoises in the Baltic Sea and, on the basis of reviewed material, tries to identify critical remaining uncertainties and suggests management needs. Information on porpoise demography like distribution, abundance, migration, population structure, and factors affecting survival are presented.
The historic range of the harbour porpoise extended into the north-eastern parts of the Baltic Sea. During the second half of the 20th century, numbers of harbour porpoises have declined and the distribution range narrowed. Currently there is a considerable difference in abundance in the Kattegat and Belt Sea (0.73-0.99 animals km-2) as opposed to the Baltic Proper (<0.01 animals km-2). Although recent orphometric, genetic and contamination studies of harbour porpoises in the Baltic Sea are somewhat inconsistent with respect to population structure, the existence of a distinct Baltic subpopulation appears to be a valid concept. Migrational patterns of Baltic Sea animals are still ambiguous. In historic times large numbers of harbour porpoises were hunted in the Danish straits during winter and spring. Therefore it was often concluded that porpoises escaped from ice cover in the eastern Baltic Sea in the winter and re-colonised the Baltic Proper in spring. Recent observations indicate that migration behaviour is much more complex and diffuse. There seems to be a tendency of animals from the Kattegat to migrate into the North Sea during winter. But also animals remaining in the western Baltic or Baltic Proper have been described. Available nutritional studies suggest that harbour porpoises take a variety of different prey.
Herring, sprat and cod are their most important prey items. Sexual maturity is attained at an age of 3-4 years. A larger proportion of females give birth to one calf every year (pregnancy rates were reported between 0.61 and 0.84). The average life span of harbour porpoises in the Baltic Sea is unknown. From existing data, a maximum age of 22 to 23 years seems to be a realistic assumption. However, a high mortality in the first years of age and a proportion of less than 5% of the animals living beyond 12 years have a significant impact on the potential for increase of the stocks. It is assumed that shallow areas play an important role for this species with respect to calving and nursing. A variety of studies report heavy attacks from parasites such as Anisakis simplex, Tonyurus convolutus, Stenurus minor, Halocercus invaginatus or Pseudalisus inflexus. However, when compared to samples from Greenland these can be regarded as normal infestations. Environmental contaminants most likely affect the long-term viability of Baltic Sea harbour porpoise stocks and might have been a major cause for the decline of Baltic Sea harbour porpoise stocks between the 1940s and the 1970s. Since then concentrations of PCBs and other organochlorine contaminants have declined. To date, the most important threat to Baltic Sea harbour porpoises is by-catch. Noise pollution has the potential to increasingly become a major threat due to the development of new activities in the Baltic Sea (offshore-windpower plants, fast ferries, etc.). This study lists a number of life history variables for which data is urgently needed. On the basis of the currently available knowledge, an effective management strategy must include political and technical means of mitigating threatening activities such as by-catch, disturbance to critical habitat, disposal of contaminants and over-fishing. In this respect it is important to establish marine protected areas and time- and area closures for certain fisheries which are likely to be unsustainable, to establish mandatory fishery observer programmes and to compile appropriate fisheries statistics.
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Recommendations for Researching / Monitoring the Potential Impacts of Magnetic Fields on Cetaceans
1. INTRODUCTION:
Any residual impacts of a development that are considered acceptable on the basis of over-riding public interest should be monitored accordingly. This is especially important if there exists any degree of uncertainty as to both the effects of a development on the environment and the significance that any impacts may have on protected species, habitats or ecology.
The precautionary principle is itself a fundamental component of Ecologically Sustainable Development, a principle officially adopted by the Australian government in the National Strategy for Ecologically Sustainable Development in 1992. It is also a principle embodied by the National Oceans Policy, which is responsible for the development of strategic regional marine plans, such as the South-East Regional Marine Plan, which covers Bass Strait.
The EPBC has most recently translated these requirements into Commonwealth law (section 3A). However, the precautionary principle (section 3A(b)) is only one of the fundamentals of Ecologically Sustainable Development. The Act also requires decision-makers to give regard to conservation of biological diversity and ecological integrity (section 3A(d)). These latter considerations are particularly important in the context of the National Oceans Policy and the forthcoming South-east Regional Marine Plan. Under these management regimes, authorities are encouraged to consider potential cumulative impacts of development.
At present Basslink's preferred method of HVDC cable construction is one which is considered to have the potential for impacting on the surrounding marine environment There is a strong case for using different technology, which is likely to have a less detrimental effect on marine wildlife. If, after mitigation measures are in place, there is any doubt as to whether there may be residual impacts from the technology employed, the situation with respect to cetaceans should be monitored. Cetaceans are at the top of the marine food chain and are indicators of the health of the marine environment. Being air breathers which need to surface, they are relatively easily detected compared to other likely affected groups such as sharks. In addition, they are poorly known in the south-east marine region and worthy of further scientific attention.
The aims of this monitoring programme would be:
(a) to establish whether or not there is an impact on cetaceans and to make recommendations for remedial work as appropriate - if this is a condition of a Section 238 (EPBC Act) permit to interfere with [any] cetaceans or the project's approval under Part 9 of the EPBC Act;
(b) to publish the results of the study in a scientific and peer-reviewed journal so that the information can be used to better inform the development process for HVDC cables in future, both in Australian and elsewhere in the world;
(c) to contribute data on the distribution and abundance of cetaceans in the Bass Strait for the benefit of regional management of South-east Australian waters under National Oceans Policy and Environment Australia's National Cetacean Sightings Database.
2. METHODS:
2.1 INTRODUCTION
Various methods are suggested as relevant to this study with the following objectives in decreasing order of priority:
(a) to establish whether cetaceans demonstrate a change in behaviour as they approach the location of the cable or change their swim direction in response to the cable;
(b) to establish whether cetaceans occur in significant numbers in the region of the cable development (with particular reference to species listed as threatened and / or migratory under the EPBC Act - most specifically Humpback Whale, Southern Right Whale and Blue Whale);
(c) to establish whether cetaceans occur at a greater / lesser than expected density in proximity to the cable.
These surveys will need to be comparative both on a temporal and spatial scale. A baseline survey prior to development is essential in order to identify the likely numbers of cetaceans passing through the Tasmanian Island chain. This will enable comparison of data collected during the development and operational phase of Basslink. Other studies will aim to assess longer term trends in abundance and distribution of cetaceans on a spatial scale by looking at both behavioural and population effects.
Surveys should be undertaken during October – December, as this is the period of southward peak humpback whale migration, the period during which southern right whales may still be encountered along the coast in Bass Strait, and the period when blue whales are likely to be moving into the area. This timing will increase the cost-effectiveness of the survey by maximising the chance of encountering cetaceans.
Surveys should also be undertaken employing competent observers using standard and statistically robust methods. This is particularly important in terms of behavioural studies. Surveys of cetacean distribution and relative abundance alone will not address the issue of ‘interference’, which is the fundamental consideration of the monitoring objectives.
Long-term monitoring should maximise the chance of obtaining statistically significant trends in the data. For example, it is possible that studies could reveal a short term change in behaviour followed by a period of habituation, the net conclusion being that there is no impact despite a change in behaviour in the first year. Equally, a natural fluctuation in abundance one year may bias the result of a short-term study making it impossible to draw reliable conclusions. In addition to identifying trends, several independent annual samples may be cumulatively analysed creating a larger data set each year. This approach is more statistically valid than collecting all the data in a single year as it allows for replication of methods.
In conclusion, it is recommended that the period for long-term monitoring should be no less than ten years.
2.2 LAND-BASED SURVEYS
Land-based methods have been successfully used to survey cetaceans up to a distance of about 18km in a number of studies. The Basslink cable would be routed to the west side of the Hogan Island group. It may be possible to position observers on Hogan Is. during periods of presumed peak whale migration (a period of about one month each year). Observers can track the movement of whales through the Bass Strait and across the cable route from a suitable vantage point using compass and theodolite. Ideally, an elevated vantage point is preferred to enhance the range of visibility. This is considered a cost-effective method of survey which will help indicate the numbers of animals passing across the cable route and enable behavioural observations to be undertaken consistent with the primary objective of the study. The simplest method of determining changes in behaviour would be to identify changes in swim direction and swim speed. Pre and post-construction monitoring would be essential. Examples of where such methods have been used in practice include Malme and Miles (1985); Würsig et al. (1994).
2.3 AERIAL SURVEYS / BOAT-BASED SURVEYS
A series of aerial surveys would be required to determine the extent of cetacean movement through areas beyond the range of land-based observers. It is suggested that a few aerial surveys are necessary, perhaps focusing in a north-south band covering the Basslink cable and some distance to either side (e.g. 4 in total during the period of presumed peak whale migration) but they are not to be depended on to meet the objectives. Aerial surveys are cost-effective for covering large areas, but can only provide a brief snapshot of cetacean distribution. They are not adequate platforms on which to determine precise behaviour. However, aerial surveys may be able to give an indication of the gross behaviour of cetaceans relative to Basslink, i.e. are they heading towards it/away from it/along it? Do they actually cross the cable?
It may be prudent to mount additional vessel based surveys to collect more specific behavioural data on a number of animals. This could be achieved over a relatively short period e.g. one month during presumed peak whale migration.
2.4 PASSIVE ACOUSTIC SURVEYS
Passive acoustic monitoring using sonobuoys has been used as a method of tracking cetaceans in Goold (1996) but with some limitations. It may be possible to utilise similar methods to determine potential impacts on species such as Common Dolphin, which are thought to occur in large numbers in the Bass Strait at certain times of the year. Passive acoustic monitoring is effective during darkness and at other times of reduced visibility, and may detect significantly more whales than visual surveys (e.g. Dawbin and Gill, 1991). It is an effective method of assessing the presence/absence of species such as blue, fin and humpback whales (e.g. Clapham and Mattila, 1990; McDonald and Fox, 1999; Stafford et al., 1999; McCauley et al., 2001), and has also been used to track movements of individual blue and fin whales (McDonald et al., 1995).
REFERENCES
Clapham, P.J and D.K.Mattila. 1990. Humpback whale songs as indicators of migration routes. Mar. Mam. Sci. 6: 155-160.
Dawbin, W.H. and P.C. Gill. 1991. Humpback whale survey along the west coast of Australia: a comparison of visual and acoustic observations. Mem. Qld Mus. 30(2): 255-7.
Goold, J.C. (1996) Acoustic Assessment of Populations of Common Dolphin Delphinus delphis in Conjunction with Seismic Surveying. J. Mar. Biol. Ass. UK. 76, 811 - 820.
Malme, C.I. & Miles, P.R. (1985) Behavioural responses of marine mammals (gray whales) to seismic discharges p. 253 - 280 In. Proc. Workshop on Effects of Explosives Use in the Marine Environment, Jan. 1985, Halifax, N.S. Tech. Rep. 5 Can. Oil and Gas Lands Admin. Environ. Prot. Branch, Ottawa, Ont. 398p.
McCauley, R.D., C. Jenner, J.L. Bannister, C.L.K. Burton, D.H.Cato and A Duncan. 2001. Blue whale calling in the Rottnest trench – 2000, Western Australia. Project CMST 241, Report R2001-6, Centre for Marine Science and Technology, Curtin University, Perth.
McDonald, M.A., J.A. Hildebrand and S.C. Webb. 1995. Blue and fin whales observed on a seafloor array in the northeast Pacific. J.Acoust. Soc. Am. 98: 712-721.
McDonald, M.A. and C.G. Fox. 1999. Passive acoustic methods applied to fin whale population density estimation. J.Acoust. Soc. Am. 105: 2643-2651.
Stafford, K.M., S.L. Nieukirk and C.G. Fox. 1999. Low-frequency whale sounds recorded on hydrophones moored in the eastern tropical Pacific. J.Acoust. Soc. Am. 106: 3687-3698.
Würsig, B., F. Cipriano and M. Würsig. 1991. Dolphin movement patterns: information from radio and theodolite tracking studies. Pages 79-112 in K. Pryor and K. S. Norris, ed. Dolphin Societies-discoveries and puzzles. University of California Press, Los Angeles, CA.