Review of Cabling Techniques and Environmental Effects Applicable

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