WPNL 202202

Wind Farm in Focus
transported to the port of Kampen, a journey of one and a half to
two hours. Two pontoons were used to keep the momentum going.
And while the components were being prepared for transport, a
team was already on its way to the next wind turbine to make
preparations.
In total, 11 people were working on the water every day. Engineers
from Iver, two seamen from Wagenborg who secured the cargo on
the auxiliary pontoons, the engineers on the cranes, a skipper on
the tugboat and one on the Multicat, and finally a specialist cutter.
The latter cut the monopile. Cuperus: ‘We would have preferred to
remove the entire monopile foundation, but the specifications stated
that they had to be cut two metres below the bottom level of the
IJsselmeer.’ Faber adds: ‘This has to do with the stability function
of the dike. The Water Authority was also concerned about potential
rising seepage water due to leakage.
In the first phase of the project, the monopiles that still protruded
about 150 cm above the water surface were cut with a cutting torch
to 80 cm above the water surface. With a diameter of 3.5 metres
and an edge thickness of 3.5 cm, this process took an average of 45
minutes. The last wind turbine was removed in May. This first phase
proceeded to Iver’s complete satisfaction and without any delays.
Faber: ‘We had a lot of wind in the first week, which meant that we
could only dismantle three wind turbines. After that, we removed an
average of five wind turbines per week. The weather conditions were
great. In the end, we finished ahead of schedule.’
Processing materials
The components were transported over water to Kampen and
immediately sorted and processed on arrival. The cables and
control boxes were removed and the metals separated. The bare
steel towers and hub remained and were immediately scrapped at
the company Hoeben in Kampen. The nacelle and control boxes
were kept. Cuperus explains: ‘This is because we think there is still
a market for spare and overhaul parts and that demand will remain
for some time. Energy prices are high so now it’s attractive to keep
wind turbines that qualify for an extended lifespan operating
longer.’
The blades went to Vattenfall as agreed. Cuperus: ‘We ourselves
also offered to process these blades sustainably. Via Germany, where
these glass fibre reinforced plastics are processed as an energy
substitute and the residue as a building material for cement. We also
used this recycling method in an earlier project with the blades of
the Landtong Wind Farm. This seems to be the only method
available on a large scale at the moment.’ However, he understands
that Vattenfall wants to go a step further and challenge the market
for better applications where rotor blades can be recycled to a
higher standard. Iver was therefore only responsible for cutting the
blades into small pieces (pre-treatment) so that they could be
transported more efficiently and with fewer emissions.
Removal of monopiles
The removal of the remaining monopile sections was somewhat
exciting for both men. After all, the piles were still some 21 metres
into the ground and had to be cut off at 2 metres below the bottom
of the IJsselmeer. Cuperus: ‘We had obviously never done that on
land before. The question was therefore, how could we efficiently
cut the steel tubular piles at this depth?’
In the end, the decision was made to cut the piles from the inside.
Faber explains the process. The combined pontoon was split for this
purpose: the one with the large crane was removed, while the other
remained behind with the small crane. The piles were then dredged
to 2.5 metres below ground level. Cuperus: ‘It was important that
this work was carried out meticulously without clay adhering to the
inside of the pile. This was to prevent the cutting tool’s cutting
heads from getting stuck during the firing process.’
After the dredging of all monopiles was completed, the cutting of
the piles was started. Iver used the offshore cutting tool of TMS
from Werkendam. A winch was used to bring the tool to the right
depth, after which the lifting frame of the tool was fixed to the pile
with clamping blocks. The tool has two cutting heads and a scraper
to clean the surface to be cut. Both cutting heads rotate 185 degrees
and can thus cut the entire diameter of the pile. Underwater
cameras monitored the quality of the burn-off. The entire cutting
process was controlled and monitored from a control unit on deck
in a container. After cutting the monopile, it was lifted out of the
water with the cutting tool’s lifting frame. The monopiles were then
transported in two batches on a pontoon to Kampen. The removal
of the monopiles took only 2 weeks in total.
After removing the monopiles, the IJsselmeer lakebed was fully
restored by filling and dumping sediment. A sonar survey was
conducted to check whether the bed had been properly restored.
Repair work also had to be carried out on the dike itself. A support
remained when removing the footbridge at each wind turbine.
These had to be removed and the dike was then repaired with
basalt blocks, set by an experienced company.
© Iver
Extensive preparation
A wind turbine dismantling project is sometimes underestimated.
The complexity increases. In reality the work is similar to the
construction process but in reverse. Not everyone realises that it
involves a considerable preliminary process, says Cuperus. That was
certainly the case with the dismantling of the Irene Vorrink Wind
Farm, as it is part of the larger repowering project Windplanblauw
and has a complex maritime character.
For example, Iver’s activities took place in an area where regular
shipping and various other parties and contractors were also
working, including Ballast Nedam who were preparing the
construction of the foundations for the new wind farm further out
in the IJsselmeerand also the fishermen using fishing pots. This
involved a lot more coordination and fine-tuning, with the Marine
Coordinator of Windplanplan having to be informed on a daily
basis.
Necessary permits and notifications were also required for this
specific location. For the dismantling activities, Iver applied for a
permit from both the Zuiderzeeland Water Authority and the
municipality. As the competent authority, the Water Authority is not
only responsible for the dike but also for the first few metres in the
water. Rijkswaterstaat is also closely involved in this process because
of the use of the IJsselmeer. Such a permit process with a complex
project requires the necessary preparations, coordination and a long
lead time.
Iver has therefore drawn up an extensive project plan for this
project. Both focused on the execution method as well as the safety
measures. In addition, an ecological work protocol was drawn up
describing management methods to prevent, for example, birds
from breeding in the work area. Iver mowed strips of grass on the
dike to prevent this. The work area was checked weekly by an expert
for breeding birds and the presence of nests.
‘We took advise on the height at which to cut the piles so that a
cormorant could still escape at any time’, adds Faber.
Cuperus: ‘When you map out the preliminary process well and
make good mutual agreements, the work can proceed smoothly and
according to plan. We started on 4 April and our work proceeded
without incident or any need for intervention by the authorities or
the client.’
End of era
For Iver, the Irene Vorrink project is now complete and delivered,
although the company will continue to dismantle more wind
turbines in the region for Windplanblauw in the coming years. The
men look back on the project with pride. Never before has Iver
dismantled a wind farm with 28 wind turbines in such a complex
environment. For a number of mechanics, however, this has been
an extra special project, says Faber: ‘As a company, we have been
involved in this wind farm for years: from construction, to carrying
out maintenance for years, to dismantling.’ Cuperus: ‘A mechanic
from Iver was involved in the installation of the wind turbines in
1995 and still has photos of it. Now 27 years later (still working as a
mechanic for Iver), he and the Iver team were commissioned to
dismantle the wind turbines, for him the circle is complete.’
Anyone driving by now sees only a dike, like many other dikes in
the Netherlands. But that is only temporary. If you pay close
attention, you will see the activities that are taking place for the new
wind farm to be constructed in the IJsselmeer. Admittedly, this
wind farm will be located further out in the water from the dike,
but the new wind turbines will still be visible from the A6. •
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