Every construction requires a proper foundation. This was first
and foremost the responsibility of Dutch company Ballast Nedam Offshore, which was given the order for ail works on the
structures below sea level. "We are seamen and we are very familiar with activities at sea", says Hylke van Lieshout, who was
responsible for the Butendiek project at Ballast Nedam Offshore.
"We were already making calculations based on the geological data in compliance with Siemens' 3.6 mégawatt offshore
System at a very early stage in the summer of 2011 when no
contract had even been signed yet. These data enabled us to
further optimise the foundation design of the monopiles", the
Project manager recounts. "In the end we designed two types of
monopiles, one with a diameter of 6.5 métrés and one with
6 métrés", explains Lieshout. "But every monopile is unique because every single location requires a different length."
The Outchman reveals his satisfaction with the work of EEW who
realised the predefined designs for the monopiles in Rostock and
Lubmin as well as for the transition pièces. "They did a good job."
In addition, Ballast Nedam had well-organised logistical processes, which helped to bring the components from their places of
manufacture to the construction site on time. Three barges were
used to transport the transition pièces in upright position whilst
horizontal transportation of the monopiles relied on several cargo vessels. Just in time. "If not, we lose a lot of money as a contractor."
Around 306 employées of Ballast Nedam worked on the foundations round the clock during the construction phase. They were
in constant communication with Tim Kühl and Jôrn Stellamanns,
who were responsible for this part of the project on behalf of
wpd offshore solutions. Noise réduction during pile-driving was
also a very important factor for the foundation work. Therefore, a
double-walled Steel casing was used and placed on the sea bed,
enclosing the monopile. "We had already used this technique,
which was developed by the manufacturer IHC-Merwede in a previous offshore wind farm project. Accordingly we had been able
to already gain considérable expérience, which we further refined
and successfully implemented on the Butendiek construction
site", says Lieshout. In the end, the IHC screen combined with the
big bubble curtain, which was used as a further noise mitigation
method, were the deciding factors in meeting the so far strictest
noise levels set by the approval authority. In most cases, noise
levels during piling operations did not exceed the threshold set by
the Fédérai Maritime and Hydrographie Agency of Germany. "My
staff and I are very proud of what we achieved in the Butendiek
project", says Lieshout.
In view of the complex matrix, the Ballast Nedam crew hâve
indeed every right to be proud of their work. As can ail others, by
the way, who worked at sea to successfully réalisé this project.
Prior to the start of pile-driving in begin of April 201A the first
layer of scour protection was put in place starting from March. A
layer of stones, 30 métrés in diameter, was laid at each of the 80
locations and raised to a height of up to one métré. The stones
were loaded in Norway by the fallpipe vessel Simon Stevin. The
second layer, with considerably larger and heavier stones, was
unloaded around the monopile and onto the cables. The stones,
weighting from AO to 200 kilos, were put in place by the smaller,
more agile rock dumping vessel Tiger as well as the Simon Stevin. Ballast Nedam ordered 130,000 tons of stones in total, which
were placed at the 80 monopile locations.
22
and foremost the responsibility of Dutch company Ballast Nedam Offshore, which was given the order for ail works on the
structures below sea level. "We are seamen and we are very familiar with activities at sea", says Hylke van Lieshout, who was
responsible for the Butendiek project at Ballast Nedam Offshore.
"We were already making calculations based on the geological data in compliance with Siemens' 3.6 mégawatt offshore
System at a very early stage in the summer of 2011 when no
contract had even been signed yet. These data enabled us to
further optimise the foundation design of the monopiles", the
Project manager recounts. "In the end we designed two types of
monopiles, one with a diameter of 6.5 métrés and one with
6 métrés", explains Lieshout. "But every monopile is unique because every single location requires a different length."
The Outchman reveals his satisfaction with the work of EEW who
realised the predefined designs for the monopiles in Rostock and
Lubmin as well as for the transition pièces. "They did a good job."
In addition, Ballast Nedam had well-organised logistical processes, which helped to bring the components from their places of
manufacture to the construction site on time. Three barges were
used to transport the transition pièces in upright position whilst
horizontal transportation of the monopiles relied on several cargo vessels. Just in time. "If not, we lose a lot of money as a contractor."
Around 306 employées of Ballast Nedam worked on the foundations round the clock during the construction phase. They were
in constant communication with Tim Kühl and Jôrn Stellamanns,
who were responsible for this part of the project on behalf of
wpd offshore solutions. Noise réduction during pile-driving was
also a very important factor for the foundation work. Therefore, a
double-walled Steel casing was used and placed on the sea bed,
enclosing the monopile. "We had already used this technique,
which was developed by the manufacturer IHC-Merwede in a previous offshore wind farm project. Accordingly we had been able
to already gain considérable expérience, which we further refined
and successfully implemented on the Butendiek construction
site", says Lieshout. In the end, the IHC screen combined with the
big bubble curtain, which was used as a further noise mitigation
method, were the deciding factors in meeting the so far strictest
noise levels set by the approval authority. In most cases, noise
levels during piling operations did not exceed the threshold set by
the Fédérai Maritime and Hydrographie Agency of Germany. "My
staff and I are very proud of what we achieved in the Butendiek
project", says Lieshout.
In view of the complex matrix, the Ballast Nedam crew hâve
indeed every right to be proud of their work. As can ail others, by
the way, who worked at sea to successfully réalisé this project.
Prior to the start of pile-driving in begin of April 201A the first
layer of scour protection was put in place starting from March. A
layer of stones, 30 métrés in diameter, was laid at each of the 80
locations and raised to a height of up to one métré. The stones
were loaded in Norway by the fallpipe vessel Simon Stevin. The
second layer, with considerably larger and heavier stones, was
unloaded around the monopile and onto the cables. The stones,
weighting from AO to 200 kilos, were put in place by the smaller,
more agile rock dumping vessel Tiger as well as the Simon Stevin. Ballast Nedam ordered 130,000 tons of stones in total, which
were placed at the 80 monopile locations.
22