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 will affect collision risk for vessels undertaking cable installation (or maintenance) which can be summarised as follows: ● ● ● 132 The navigation (i.e. direction and manoeuvrability) of cable installation vessels is restricted by the cable and any burial equipment operated from the vessel. Laying speed is slow (anywhere between 100m/hr to 1000m/hr), and the heading of the cable installation vessel may well be set to minimise environmental forces from wind and current. The cable installation vessel is likely to be operating subsea equipment, and may be moored by anchors which will be deployed some hundreds of metres from the vessel. All these factors may not be anticipated by passing navigational traffic. Although Notice to Mariners are issued via the Marine Coastguard Agency they do not always get received by all intended recipients. For example, during the installation of power cables across the Solent in the late 1990’s a power boat race came very close to the mooring wires of the main cable installation barge (Bomel Ltd., pers. comm.); Cable installation vessels will always display cable laying signals to warn passing traffic. Similarly, radio navigation warnings will be requested and broadcast in addition to advance notification of works in a notice to Mariners and Kingfisher bulletins and Kingfisher Information charts; and Cable layers are typically supported by various vessels including anchor handlers, dive support vessels, ROV vessels and personnel launches. The activity of such vessels should be under the control of the operations superintendent of the main installation vessel to ensure coordination. The effects on shipping and navigation will be described within the project’s navigation risk report, and possible risk mitigation measures suggested. As part of the project’s required Navigational Risk Assessment, the DTI (now BERR) guidance (2005a) advocates implementation of a proposed Marine Navigational Safety Goal which should be managed through the life of the offshore installation. This includes a list of measures that serve to reduce risk to that which is “as low as reasonably practical” and that ensures “relevant good practice risk controls are in place”. The development of Emergency Response Plans for each site is also recommended as part of the guidance such that the lines of responsibility and reporting are clear and predefined, to minimise any potential risks to human life and the environment (DTI, 2005a). 5.8.2 MITIGATION MEASURES Vessels associated with cable installation works may lead to some temporary minor disruption to regular traffic and navigation; however the degree of these effects will be site specific and can be minimised through planning and liaison with appropriate regulators and other sea users. Best practice mitigation
Potential impacts and mitigration measures measures (as also cited above) relevant to construction and maintenance activity include: ● ● ● ● ● ● ● Circulation of information to vessel operations prior to operations; General notices via Navtex, Notices to Mariners and Admiralty Charts; Workshops to discuss navigational issues during construction; Use of guard vessels during construction; Monitoring of shipping during construction; Development of Emergency Response Plans; and Measures to advocated by BERR’s proposed Marine Navigational Safety Goal. Other guidance for ship collision avoidance also exists (UKOOA, 2003) and good practice guidelines should be followed whenever it is intended to anchor or locate a vessel within two kilometres of cables, pipelines and other subsea installations (UKOOA, 2002). It should be noted that Safety Zones as defined under the Energy Act 2004, which serve to protect safety of life around offshore installations, only apply to the offshore wind farm structures and not the associated vessels. Exclusion areas around installation vessels cannot therefore be enforced under these provisions. Guidance in ICPC (1996), cautions fishermen to keep at least one nautical mile away from a cable laying vessel and that fishing gear should never be operated astern of such a vessel for risk of engaging with a plough which will typically be operating three times the water depth away from the stern of the main cable installation vessel. 5.9 Seascape and Visual Character BERR has produced guidance on the assessment of seascape and visual impacts of offshore wind farms (DTI, 2005b) This guidance makes recommendations on how to assess and deal with the seascape and visual impact assessment element of an EIA for an offshore wind farm development. Seascape and visual impacts related to the cable installation activities and not considered to be potentially significant, will be limited to: ● ● ● Presence of the cable installation vessel and support vessels; Associated activity including plant and people present in the intertidal area; and Possible sea surface aesthetic effects from any sediment plume generated as part of the installation, particularly where chalk is disturbed. 133
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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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4 Physical change 4.1 Introduction
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Page 140 and 141: 6 Good practice measures This secti
Page 142 and 143: 7 Gaps in understanding Research fo
Page 144 and 145: References Introduction Sinden, G.
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Page 164: Printed in UK on recycled paper. De
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