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 5.7.3 MITIGATION MEASURES For installation works in the intertidal zone, the approach to appropriate mitigation will be determined by the sensitivity of the habitat. If installation is to take place within an area of importance to birds, such as an SPA, it will be necessary to ensure that the measures proposed are sufficient to avoid an adverse effect on the integrity of the designated site. In such circumstances, it will be necessary to agree mitigation with the relevant nature conservation body as part of the EIA process. In many cases the SPA will be designated for supporting over wintering assemblages of waders and waterfowl. Restrictions may be placed upon works occurring during the over wintering period (1 st October to 15 th April in any one year) or other sensitive times for specific species (e.g. breeding periods for Annex I birds, such as little tern). Offshore, practical implementation of mitigation measures aimed at minimising impacts on birds is extremely difficult. In particularly sensitive areas, such as shallow sandbanks, avoiding key times of year in terms of peak numbers of birds feeding over known areas of the cable route would ensure that significant disturbance is avoided. However, such an approach is likely to be difficult to achieve, unless there is reliable and robust information on the locations and seasonality of important prey resources in the study area. Also, given the transitory and temporary nature of the installation, the effect upon birds, at sea is unlikely to be significant. Examples of operational restrictions that have been placed on offshore wind farms through the FEPA licences in order to minimise the impacts on birds, include: ● 130 Kentish Flats “The Licence Holder must ensure that if cable installation occurs between October and April inclusive (the over-wintering season for several wader species) the beach installation, including trenching and cable laying, avoids the sensitive period 2 hours either side of high water. The Licence Holder should also investigate putting in place acoustic shielding around all construction activities on the beach and at the adjacent construction compound in Hampton Pier car park to further minimise any potential disturbance.”
● Barrow Potential impacts and mitigration measures “As there are internationally important numbers of common scoter in the vicinity of the wind farm, the Licence Holder must ensure that works are undertaken in the months of March to October (inclusive) so as to minimise disturbance to over-wintering birds. Any specific requirement for works outside these times shall only take place after written approval from the Licensing Authority (following consultation with CEFAS and English Nature). In so far as is practicable, the majority of the piling or drilling works shall only be undertaken during the months of April to June.” Where technically and economically feasible, effective mitigation could be applied through the final choice of the cable installation technique. For example, the use of horizontal directional drilling (as opposed to ploughing and trenching) would reduce the area of intertidal impacted and involves shorter periods of human presence in areas sensitive to disturbance. 5.8 Shipping and Navigation A maritime traffic survey, navigation assessment and a Navigation Risk Assessment will be required for the offshore wind farm development, in accordance with the requirements of the Maritime and Coastguard Agency’s (MCA) Marine Guidance Note MGN 275(M) 6 . Information from this work can be used to identify and evaluate potential impacts regarding the cable installation. A Guidance Document is also available on the ‘Assessment of the Impact of Offshore Wind Farms: Methodology for Assessing the Marine Navigational Safety Risk of Offshore Wind Farms’ (DTI, 2005a). The purpose of the guidance document is to provide a template to be used by developers in preparing their navigational risk assessments, and to assist Government Departments in the assessment of these. The key impact associated with cable installation activities will be: ● Increased risk of collision by existing navigational users in the cable installation area. POTENTIALLY SIGNIFICANT EFFECTS Collision risk Due to the increase in the number of vessels and movement of the vessels involved in cable deployment and burial, there will be some temporary and minor disruption to navigation. There are a number of particular factors which 6 Proposed UK Offshore Renewable Energy Installations (OREI) – Guidance on Navigational Safety Issues 131
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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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3 Cable types and 18 installation t
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Page 82 and 83: 4 Physical change 4.1 Introduction
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Review of Cabling Techniques and Environmental Effects Applicable

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