That is how Hydrotechnik Lübeck came to be involved. The experts from the Hanseatic town on the river Trave were already
waiting in the port of Havneby with their vessel, Noortruck, in accordance with the noise mitigation concept previously drawn up.
"After receiving a call from the Installation Manager, we cast off
immediately and sailed to the construction site", Cay Grunau recalls. An additional big bubble curtain was then activated on every
site where a monopile was to be driven, always in close consultation with the Master of the Svanen. "We lay a 380 métré long hose
on the sea bed from our vessel using a large winch", says Grunau
as he explains the procedure which must not interfère with the
installation work. "The hose has a diameter of ten centimètres
and is perforated with many holes from which air is blown into
the seawater at a pressure of 10 bar. Using this high-pressure
hose, we then generate the bubble curtain around the installation
vessel."
It takes one hour at the most to préparé the hose, and then the
pile-driving work can begin. This additional noise mitigation
method did indeed achieve great success as in combination with
the Noise Mitigation Screen from Ballast Nedam, the bubble curtain company succeeded in reducing noise émissions below the
threshold at a distance of around 45 métrés. But success cornes
at a price: the whole noise mitigation concept costs an amount
in the double-digit millions. "Butendiek delivered valuable pioneering work for the worldwide offshore industry", says Managing
Oirector Grunau who gave a présentation on the technical capabilities of the bubble curtain in wpd's offices in Bremen in 2010
and is now delighted with the resuit. "Is there anything nicer than
to work on and under the water and at the same time to make
a contribution towards protecting animal life?" asks the experienced hydraulic engineerwith a satisfied expression.
Like Grunau, ail those involved in the end expressed their satisfaction with the noise results achieved which were often no more
than 156 dB at a distance of 750 métrés from the pile-driving
action and for ramming at one location even went no higher than
150 dB.
101
waiting in the port of Havneby with their vessel, Noortruck, in accordance with the noise mitigation concept previously drawn up.
"After receiving a call from the Installation Manager, we cast off
immediately and sailed to the construction site", Cay Grunau recalls. An additional big bubble curtain was then activated on every
site where a monopile was to be driven, always in close consultation with the Master of the Svanen. "We lay a 380 métré long hose
on the sea bed from our vessel using a large winch", says Grunau
as he explains the procedure which must not interfère with the
installation work. "The hose has a diameter of ten centimètres
and is perforated with many holes from which air is blown into
the seawater at a pressure of 10 bar. Using this high-pressure
hose, we then generate the bubble curtain around the installation
vessel."
It takes one hour at the most to préparé the hose, and then the
pile-driving work can begin. This additional noise mitigation
method did indeed achieve great success as in combination with
the Noise Mitigation Screen from Ballast Nedam, the bubble curtain company succeeded in reducing noise émissions below the
threshold at a distance of around 45 métrés. But success cornes
at a price: the whole noise mitigation concept costs an amount
in the double-digit millions. "Butendiek delivered valuable pioneering work for the worldwide offshore industry", says Managing
Oirector Grunau who gave a présentation on the technical capabilities of the bubble curtain in wpd's offices in Bremen in 2010
and is now delighted with the resuit. "Is there anything nicer than
to work on and under the water and at the same time to make
a contribution towards protecting animal life?" asks the experienced hydraulic engineerwith a satisfied expression.
Like Grunau, ail those involved in the end expressed their satisfaction with the noise results achieved which were often no more
than 156 dB at a distance of 750 métrés from the pile-driving
action and for ramming at one location even went no higher than
150 dB.
101