Offshore Wind Power Projects in the Great Lakes - Ministry of ...

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Offshore wind power projects in the Great Lakes: Background and science considerations for fish and fish habitat 5.5 Assessing the potential impacts of electromagnetic fields on fish The potential impacts of EMFs from submarine power cables on fish behaviour and physiology are poorly understood, especially in a Great Lakes setting. In order to fully understand or predict the effect that emissions from submarine turbine cables will have on aquatic species, a valuable piece of information is the nature and strength of the electric and magnetic fields associated with the specific type of electrical transmission cabling to be employed at a given offshore wind power installation. While electrical engineering models can be used to simulate or predict field strengths and their attenuation with distance from the cabling, direct EMF measurements should ideally be made in the field at varying distances from the cable, and across the full range of voltages and amperages expected to be carried by the cables across their operational lifetime, and as additional turbine units come online (U.S. Department of Energy 2009). Measurements should be conducted not only along the length of the cable running to shore (where burial might occur to greater depths in some areas and alter EMF strength) but also within the inter-turbine array. It has recently been recognized that significant EMF interaction can occur between cables lying within close proximity to each other within an offshore wind power project, such as would occur at offshore substation connection points (Gill et al. 2005). The potential for additive effects from overlapping EMFs is difficult to predict based on modelling alone and would need to be analyzed through site-specific measurements of the resultant field strengths of multiple closely arrayed cables. Once measurements of EMF strengths are made in the field, they can be compared to the reported electro- or magneto-sensitivity of different fish or benthic organisms likely to be found within or travelling through the proposed project area. In this way, the likelihood that EMFs from submarine cables could be detected by and potentially alter the movement or migration of local fish species could be evaluated and best management practices put in place to reduce any anticipated interference. Beyond this, seasonal baseline or pre-construction fish community surveys throughout the project area and along the proposed cable route would be needed to establish whether EMF-sensitive species inhabit or move throughout the area. In order to definitively determine whether these species will be affected by EMFs from the submarine power cables, however, field studies assessing the behavioural response of fish to the electric and magnetic fields from the cables during wind turbine operation are necessary. The behavioural response of local fish to EMFs could be elucidated by observing the reaction of individuals as Aquatic Research and Development Section 64
Offshore wind power projects in the Great Lakes: Background and science considerations for fish and fish habitat they approach the cables, by comparing the abundance and distribution of species in the vicinity of cables to their abundance and distribution in nearby control areas, or by conducting gradient analyses of how fish biomass and distribution vary as a function of distance to the cables. However, even with these types of targeted analyses, it will be difficult to isolate the effects of EMFs from operational noise effects. Addressing this challenge is discussed in more detail in the research needs section below. 5.6 Monitoring effects of local changes in water quality As highlighted in our earlier report (Nienhuis & Dunlop 2011), there are a number of ways in which the installation of offshore wind power projects in the Great Lakes could impact local water quality, with potential consequences to fish and other aquatic organisms. Correspondingly, in order to assess the significance of these effects and determine whether preventative or mitigation measures are required for certain activities, monitoring would be warranted. However, most water quality impacts are expected to arise over the short-term during the construction phase, with increases in turbidity and potential sediment contaminant release being most probable during dredging or drilling operations. For this reason, effects monitoring for local changes in water quality should be intensively targeted around the specific operation of concern. To quantify the impact of these activities on local water quality, baseline measurements are first needed of relevant chemical (i.e. dissolved oxygen, nutrient and contaminant concentrations) and physical parameters (i.e. light penetration depth, secchi depth, and suspended solid concentrations) at various water column depths within the predicted area of impact, following standardized sample collection and analysis protocols. Having established background water quality conditions, comparisons can then be made with measured conditions during and after those construction activities resulting in sediment disturbance. Measured changes in water quality parameters could then be related to any observed differences in fish abundance or behaviour, presuming that fish surveys are conducted concurrently alongside water quality assessments. This was done at the Lillgrund offshore wind power project in Sweden, where investigators conducted trawling surveys following a BACI experimental design to assess the immediate, short- and long-term effects of dredging-related turbidity on the abundance of small fish in the area (Hammar et al. 2008). Aquatic Research and Development Section 65
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