ENVIRONMENTAL STATEMENT BARDOLINO DEVELOPMENT

Bardolino Development Environmental Statement
6.2 THE PHYSICAL PRESENCE OF THE DRILLING RIG AND SUPPORT
VESSELS (INCLUDING ANCHORING OF THE DRILLING RIG)
6.2.1 Likely magnitude and duration
Shell proposes to drill the Bardolino development well with Transocean’s semi-submersible
drilling rig, the Arctic IV. The presence of the semi-submersible rig and support vessels
during the drilling operations might result in some interference with commercial fishing or
shipping in the area adjacent to the Bardolino location. A temporary safety exclusion zone
with a radius of 500m centred on the semi-submersible drilling rig would be established for
the duration of drilling operations, a period of 3 months. This would exclude commercial and
fishing vessels from an area of approximately 0.8 km 2 .
The semi-submersible drilling rig would be positioned over the drilling location with the aid of
the three AHTVs, and would maintain its station by eight anchors in a pre-determined ‘anchor
pattern’. In such a system, the anchors are attached to the drilling rig with a chain and cable
combination; for each anchor line approximately 300m of chain would be in contact with the
seabed, providing additional holding power. The use of anchors to position and moor the
semi-submersible drilling rig would result in the physical disturbance of seabed sediments and
benthic fauna in localised areas around the anchors (chains and wires) during deployment
and retrieval.
Depending on the nature of the seabed, anchors can create mounds up to 1 m high, and
anchor chains lying on, and sweeping over, the sediments can create gouges and scour
marks. Anchor mounds can form on clayey sediments, and because of the stiffness of clay
they have the potential to become long-lived seabed features that may represent obstructions
to mobile fishing gear deployed on the seabed. The anchoring conditions survey undertaken
for the Bardolino well location indicated that seabed sediments comprise a veneer of sand
with outcrops of clay (Gardline Geosurvey Limited, 2007). The shallow soils comprise soft
to firm slightly sandy clay with occasional gravel, ranging from 25 m thickness in the west to
being locally absent in the east (Gardline Geosurvey Limited, 2007). It is possible that
persistent anchor mounds would be created on this type of sandy clay sediment.
6.2.2 Impact on sensitive receptors and proposed or designated sites
The presence of the semi-submersible drilling rig at the Bardolino location would result in a
temporary loss of access to fishing grounds and a temporary inconvenience to commercial
shipping in the area. The overall relative value of fisheries in the Bardolino development area
is classified as “very low” to “low” for ICES rectangles 44F1 and 43F1 (SEERAD, 2008b)
(Section 4.5.1). The relative fishing effort for demersal species, pelagic species, Nephrops
and shrimp and shellfish is “very low” (SEERAD, 2008b). Demersal pair and otter trawling
has dominated fishing effort in the Bardolino area between 2002 and 2006, with fishing
activity occurring throughout the year (Section 4.5.1). The potential disturbance to
commercial fishing from the drilling programme would be of a small-scale and would be very
unlikely to impact on the economic value of the overall fishing activity in this area. The timing
and nature of operations would be notified to other users of the sea and a dedicated guard
vessel would be on location at Bardolino to ensure that all traffic was aware of the presence
of the drilling rig.
The distribution and abundance of benthic organisms in the North Sea is determined largely
by latitude, water depth and sediment type. Results from biological surveys carried out in the
general vicinity of the Bardolino development show that the infauna is typically dominated by
polychaete worms, while epibenthic species include the shrimp Crangon allmanni and the
hermit crab Anapagurus laevis (Section 4.4.2). The macrofaunal communities of the
proposed development area are largely homogenous and typical of sandy sediments in the
central North Sea. No sensitive, rare or threatened benthic communities are known to exist in
the vicinity of Bardolino.
Anchor mounds and scours have the potential to cause disruption to benthic communities.
The deployment and retrieval of anchors from the semi-submersible drilling rig would cause
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