This environmental impact assessment for Kriegers flak ... - Vattenfall

12.4 Fauna
The occurrence of invertebrate benthic fauna is described
in Chapter 11.6.1.
12.4.1 Invertebrate benthic fauna
12.4.1.1 Impact
The wind farm may cause negative impact on the
benthic fauna as part of the seabed is occupied by the
turbines, due to changed sedimentation and due to
spills and pollution.
a) Occupied seabed/secondary hard structure
The foundations of the turbines occupy about 0,008 %
of the total area of the wind farm and this space will
disappear for the benthic fauna. In addition, the area
occupied by the transformer stations and the temporary
disturbance when laying the cables in the wind farm
area is also taken, but the occupied area is a negligible
part of the total area. The direct loss of seabed due
to permanent installations will, with high probability
therefore, not be of importance for the macrozoobentos
present in the area.
Each foundation will also form a secondary, new
hard structure with an area of between 400 and 900
m2, which is ten to twenty times larger than the lost
hard seabed, albeit with a different spread of depth.
The secondary hard surfaces will probably compensate
for the loss of hard seabed.
b) Clouding and changed sedimentation
Due to work with the foundations, clouding and
temporary increased sedimentation may occur during
the construction and dismantling phases, and due to
changed ß owing conditions the same may occur during
the operational phase. The worst problems are estimated
to occur during the construction and dismantling
phases.
The marine seabed fauna can, within a limited area,
be subjected to increased sedimentation through over
layering of sediments. This could result in reduced
growth, reduced survival or direct death. Certain
species can penetrate up to 90 cm thick layers of sand
whilst other species cannot even survive an over layering
of a few centimetres.
CONSEQUENSES OF THE WIND FARM 123
Indirect consequences may also occur due to reduced
occurrence of food due to reduced survival of
marine algae.
Adhesive fauna are dependent on water transport for
nourishment and for these animals, an increase of sediment
in the water may have a negative impact as in and
outß ow openings may become blocked.
Mobile fauna may also be subjected to clouding.
Stationary or semi stationary species (for example sedentary
polycheats) are more sensitive than those that
can move (nekton, for example crayÞ sh).
During the operational phase, changed water ß owing
patterns in the areas immediately behind the wind
turbines, may lead to locally changed sedimentation
conditions, which possibly may lead to changes in the
local habitat.
c) Spills and pollution
Minor leakages should not cause any important negative
impact on benthic fauna, but large volumes of oil
or other hazardous substances could cause great damage.
The risk of spills and leakage is considered as very
low (see Chapter 5.7.2.3). Also, the risk of collisions
causing oil spill has been deemed as very low (see
Chapter 12.8.2).
Summary of impact on benthic fauna.
In summary it may be noted that sediment and sedimentation
may cause negative impact for benthic fauna
in the immediate vicinity when the foundations are
laid/dismantled. This impact is limited in time. Larger
spills and pollution would cause great damage but the
risk thereof is considered small.
12.4.1.2 Mitigating measures
Areas with a high concentration of macrozoobentos
should, if possible, be avoided.
By using a hose to suck-up free sediments during the
construction phase, sediment spreading will be minimised.
Special containers will be present on the wind
turbines to prevent oil spills (see 5.7.2.3) and the collision
avoiding measures recommended by SSPA will be
proposed by Sweden Offshore. Decision in this matter
will be made in consultation with affected authorities.