Review of Cabling Techniques and Environmental Effects Applicable

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Review of Cabling Techniques and Environmental Effects Applicable to the Offshore Wind Farm Industry – Technical Report level. The main potential impact is the disruption of the sensory cues for feeding in benthic dwellers in and around the wind farm area. This is general for all species of benthic dwelling elasmobranchii that feed diurnally and nocturnally. EMF could have two possible effects on the behaviour of elasmobranchii. Firstly, resident elasmobranchii could be deterred from feeding in and around the area within the wind farm footprint and where cables are buried. The second impact could be one of attraction of elasmobranchii to the footprint of the wind farm potentially causing an unnatural clustering effect in the area. There are, therefore, potentially significant effects on fisheries interests but to date there has been no evidence to indicate the likelihood and/or magnitude of these. The research undertaken by COWRIE, under laboratory conditions only has been insufficient to determine the precise extent of detection for many marine species; the behavioural response within the zone of detection and therefore the likely impacts on fisheries resources due to EMF from sub-sea cables (COWRIE 2005). For the Thanet Offshore Wind Farm site, English Nature stated that (given current levels of ecological understanding) there will not be a significant impact to the populations of elasmobranchii that are resident within the wind farm footprint and cable export route but English Nature’s advice is provided in the light of current information that is available (English Nature, 2006). Additional research work on electromagnetic field effects is due to be carried out under the auspices of COWRIE, which will entail “in the field” research. It is likely therefore that developers will be asked to commit to take on board the most up to date information on electromagnetic field effects, thereby making necessary and reasonable adaptations during the construction, operation and monitoring of wind farm developments. 5.4.2 MITIGATION MEASURES In terms of the natural fish resource, general mitigation measures should seek to do the following: ● ● ● 120 Avoid spawning and nursery habitats. Such information should be available from published sources or previous surveys. If this is not available then a series of dedicated surveys should be commissioned as part of the wider EIA, in discussions with Cefas; Avoid sensitive spawning times for substrate spawning species where possible (exact periods will be site specific and require evidence); Impacts from noise may be mitigated by timing construction to avoid sensitive feeding, spawning and nursery area/times of the year;
● ● Potential impacts and mitigration measures Use techniques which minimise re-suspension of sediment in areas where biotopes sensitive to smothering are present and where sediment is found to have elevated levels of pollutants; and To minimise pollution risk the laying of the cable should be undertaken in accordance with an Environmental Management Plan and general environmental good practice on site (e.g. CIRIA Marine Construction Site Guide). 5.5 Commercial Fisheries Impacts to commercial fisheries may result from effects to the targeted fisheries resource or due to alterations to fishing practices as a consequence of cablelaying operations. This section details the impacts of cables and cable installation relating to commercial fisheries over and above those identified in the natural fisheries section (Section 5.4). Commercial fishing activity can be broadly divided into two approaches: mobile gear (where the nets or lines are towed by vessels) and static gear (where nets, lines or pots are left in the environment for a period of time) 1 (Table 5.1). The vessels used for these various methods may have some degree of specialism. Table 5.1: Commercial fishing gear: mobile gear and static gear Mobile Gear Vessels Static Gear Vessels Beam trawler Drift netter Seine netter Gill netter Trawlers (e.g. demersal, freezer, pair) Long liner Dredgers (e.g. scallops, cockles) Potter/whelker Rod and line Both mobile and static gear vessels have the potential to be impacted by cable installation. The main effects of cable laying on commercial fishing activity, of potential significance are: ● ● ● Restricted access to fishing grounds; Temporary fish stock displacement; and Snagging of fishing gear. Each type of impact can lead to reduced returns and/or increased costs that result in reduced profitability for the sector. However, the actual significance of the effect would be highly site specific and dependant upon the duration of the installation process. 1 A variation on static netting gear can involve nets being set, but not anchored, enabling them to drift in the current: drift netting. 121
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REVIEW OF CABLING TECHNIQUES AND EN
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Review of Cabling Techniques and En
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Abbreviations AIS Automatic Identif
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TTS Temporary Threshold Shift TWA T
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