Greening Blue Energy - BioTools For Business

Marine impacts
Foundation Types (continued)
Floating and Platforms
Preparation – Assembled onshore, and are fixed
to the seabed with large anchors (e.g. “embedded
anchors”).
Suction Bucket foundations
Design - The suction or bucket foundation is a
concept used in the oil and gas industry where a
bucket foundation is pressed to the seabed and
suction is generated to keep it in place.
Use - Information on this technology is currently
limited.
Depth – not assessed
Preparation – No need for pile driving, and is
less complex than jacket/tripod. This type seems
most suitable in clay and sandy seabeds, as firmer
substrates require larger pressure differences.
ISSUES THAT REQUIRE SPECIAL ATTENTION
Threat: Piling noise/construction activities
The construction phase of wind farms will inevitably
generate noise from seabed preparation (e.g.
levelling, which could include the use of explosives),
installation of foundations, and boat traffic.
In particular, pile driving for monopiles, tripod and
jacket foundations causes acute noise disturbance.
Subsequent effects depend on a number of factors,
such as seabed topography and composition, diameter
of the piles, ambient sound, and the marine
species under consideration.
Generally, noise impacts should be localised and
temporary. However, noise generated during piling
may kill or injure fish, mammals, and sea turtles, or
cause them to abandon an area tens of kilometres
from the construction site. Species relocation could
severely affect spawning and nursery habitats if
appropriate seasonal prohibitions are not used. Sea
turtles may be particularly sensitive to even temporary
habitat losses, as they seem highly inflexible in
their spatial distribution patterns.
Annexe 1 – see Sections 7.1-7.4 for more details
Mitigation options
• Habitat use and migration patterns of sensitive
species need to be considered in terms of timing
of construction of wind farms. Seasons when
sensitive species congregate during key life
18 GREENING BLUE ENERGY - Identifying and managing biodiversity risks and opportunities of offshore renewable energy
stages should be avoided during construction
(and decommissioning,e.g. spring and early
summer is the main reproductive season for
many species in temperate regions).
• To avoid injuries from acute sound pulses, the
use of ‘pingers’ to scare away porpoises and
dolphins before construction activities start has
been suggested and has also been used during
wind farm construction.
• A standard approach is to gradually increase
the strength of the pile-driving hammer to
give mammals, larger fish and sea turtles a
chance to move from the area before maximum
sound generation levels are reached. It should
be noted, however, that this method is not
uncontroversial as it may lead to gradual
habituation and even attraction to the initially
week sounds.
• Another method is to surround the pile driving
area with a curtain of bubbles or wrap the
piles in sound dampening material. Bubble
protection can reduce the sound volume by
3-5 dB, i.e. half of the sound intensity, but the
method is dependent on calm waters and weak
currents.