Review of Cabling Techniques and Environmental Effects Applicable

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:
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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