The US Department of Energy and US Department of the Interior, Bureau of Ocean Energy Management commissioned this study to address the limited scientific data on the impacts of high voltage direct current cables on aquatic biota, in particular migratory species within the San Francisco Bay. The study was conducted in several stages as described in three separate technical manuscripts which capture the methods, findings and recommendations.
This report describes research sponsored by The Department of Energy and the Bureau of Ocean Energy Management under award number: DE-EE0006382.
San Francisco Bay, California, USA
Empirical evidence exists that marine animals perceive and orient to local distortions in the earth’s main geomagnetic field magnetic field. The electromagnetic fields generated by the cables that carry electricity from hydrokinetic energy sources to shore-based power stations may produce similar local distortions in the earth’s main field. Concern exists that animals that migrate along the continental shelves might orient to the EMF from the cables, and move either inshore or offshore away from their normal path. The Trans Bay Cable (TBC) is a ±200-kilovolt (kV), 400 MW 85-km long High Voltage Direct Current (DC) buried transmission line linking Pittsburg, CA with San Francisco, CA (SF) through the San Francisco Bay. The study addresses the following specific questions based on measurements and projections of the EMF produced by an existing marine cable, the Trans Bay Cable, in San Francisco Bay.
- Does the presence of EMF from an operating power cable alter the behavior and path of bony fishes and sharks along a migratory corridor?
- Does the EMF from an operating power cable guide migratory movements or pose an obstacle to movement?
To meet the main study objectives several activities needed to be carried out: 1) modeling of the magnetic fields produced by the Trans Bay Cable, 2) assessing the migratory impacts on Chinook salmon smolts (Oncorhynchus tshawytscha) and green sturgeon (Acipenser medirostris) as a result of local magnetic field distortions produced by bridge structures and 3) analyzing behavioral responses by migratory Chinook salmon and green sturgeon to a high-voltage power cable.
Based on the work carried out in this study, we provide the following conclusions:
- The mean values of twist angle, Q, cable depth, a, and load current, I, derived from the regressions appear to bear a consistency with what one could expect from direct observation of these parameters. Calculations of magnetic fields for assessment of marine life can be performed; however, local anomalies in the fields resulting from submerged structures require validation of such calculations through collection of ambient DC magnetic field data.
- The large anomalies produced by the bridges that run perpendicular to these migration routes do not appear to present a strong barrier to the natural seasonal movement patterns of salmonid smolts and adult green sturgeon.
- Chinook salmon smolts may be attracted to the activated cable based on analysis of cable crossing, mis-directions, and first presence at the array data, however, the cable activation does not appear to change the proportion of smolts that successfully migrate through the San Francisco Bay. Cable activation has different impacts on inbound and outbound migrating adult green sturgeon: travel time was increased for outbound migrations but decreased for inbound migrations. However, cable activation did not appear to impact the success of either migration type in this species.
Kavet, R.; Wyman, M.; Klimley, A.; Vergara, X. (2016). Assessment of Potential Impact of Electromagnetic Fields from Undersea Cable on Migratory Fish Behavior. Report by Electric Power Research Institute (EPRI). pp 87.