Review of Cabling Techniques and Environmental Effects Applicable
Review of Cabling Techniques and Environmental Effects Applicable
Review of Cabling Techniques and Environmental Effects Applicable
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<strong>Review</strong> <strong>of</strong> <strong>Cabling</strong> <strong>Techniques</strong> <strong>and</strong> <strong>Environmental</strong> <strong>Effects</strong> <strong>Applicable</strong> to the Offshore Wind<br />
Farm Industry – Technical Report<br />
Wind Farm Cable Route Soil Conditions Burial Depth <strong>and</strong><br />
Method<br />
Scroby<br />
S<strong>and</strong>s<br />
76<br />
Export Cables Mostly s<strong>and</strong>s<br />
along the export<br />
cable route.<br />
Inter-Array<br />
Cables<br />
Mostly s<strong>and</strong>s<br />
along the interarray<br />
cable route.<br />
Burial was undertaken<br />
using a Sea Stallion<br />
plough which had been<br />
modified to achieve a<br />
target depth <strong>of</strong> burial <strong>of</strong><br />
3m.<br />
Burial was undertaken<br />
using a Sea Stallion<br />
plough which had been<br />
modified to achieve a<br />
target depth <strong>of</strong> burial <strong>of</strong><br />
3m.<br />
Kentish Flats Export Cables - The export cables were<br />
buried using the Global<br />
Marine owned Hi-Plough.<br />
Inter-Array<br />
Cables<br />
- The inter-array cables<br />
were buried using the<br />
Global Marine Otter<br />
tracked vehicle in jetting<br />
mode.<br />
Feedback Information<br />
(where available)<br />
It is understood that all three<br />
export cables were generally<br />
buried to the target depth <strong>of</strong><br />
burial <strong>of</strong> 3m <strong>and</strong> this deep<br />
burial requirement was a<br />
permit requirement based<br />
on EMF <strong>and</strong> its effect on<br />
migratory fish as well as<br />
concerns with mobile s<strong>and</strong>s.<br />
The second export cable<br />
had to be cut during the<br />
installation due to adverse<br />
weather, an <strong>of</strong>fshore joint was<br />
subsequently introduced <strong>and</strong><br />
the repair splice buried with<br />
post lay burial techniques.<br />
It is understood that some<br />
inter-array cables have become<br />
exposed as a consequence<br />
<strong>of</strong> scour around the base <strong>of</strong><br />
the <strong>of</strong>fshore structures. It is<br />
also believed that remedial<br />
rock dumping has been<br />
undertaken but the results <strong>of</strong><br />
this subsequent intervention<br />
are unknown.<br />
The Hi-Plough was fitted with<br />
jetting equipment to reduce<br />
tow forces during installation.<br />
However, the jetting system<br />
was not utilised, partly owing<br />
to concerns with respect to<br />
suspended sediments affecting<br />
local shell fish beds <strong>and</strong> fish<br />
spawning grounds. Sediment<br />
load downstream <strong>of</strong> plough<br />
operations was monitored <strong>and</strong><br />
the limits imposed by CEFAS<br />
for increase in sediment load<br />
over background levels were<br />
not breached at any time<br />
during operations.<br />
Difficulties in burial operation<br />
were encountered where<br />
the cable installation had<br />
crossed spud depressions<br />
from the main installation<br />
vessel – Mayflower Resolution.<br />
Generally the work appears<br />
to have been successfully<br />
completed without any major<br />
incidents.