Giant wind farm putting down its concrete roots
Credit: By Kate Helyer, www.thisisdevon.co.uk 27 January 2011 ~~
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Thousands of tonnes of concrete are being transported to the fields of Fullabrook, as one of the biggest wind farm developments in the country gets under way.
The wind farm, which is due for completion in the autumn, will comprise 22 turbines, each 110m tall.
Before that, though, an immense amount of work is beginning to make its mark on the landscape.
The Journal was given permission to visit the site this week.
At first glance, there did not seem to be much more than a series of enormous holes in the ground, but after a guided tour with ESBI site manager Shay Shanley the full picture emerged.
Construction traffic needs to be able to travel around the huge site so at the end of last year 10km of access tracks were laid.
Shay said that after the build is completed, these will be covered with topsoil so that farm animals can continue to graze the land.
“But the footprint will still be there to allow engineers access, for maintenance,” he said.
The sheep, now fenced away from the main building work, but still able to keep a watchful eye on proceedings, seemed unconcerned by all the commotion.
As we drove along the track, locally hired cranes from KAS could be spotted, dotted around the site, at the location of each hole.
During our visit on Monday they were on the sixth “bottom pour”.
Each of the 22 holes has been excavated and filled with a circular network of reinforcing steel – 45 tonnes of steel go into each base.
It looks like a giant upturned sieve, with a second circle of protruding steel posts, standing vertically in the centre.
First, the “sieve” is filled with concrete – the bottom pour.
It takes an entire day and 46 truckloads of concrete to complete one bottom pour.
Later, each “top pour” will take ten truck loads of concrete. So that is 56 truckloads of concrete for each base – 1,232 truckloads in all.
That’s almost 10,000cu m of concrete – enough to fill four Olympic swimming pools.
The concrete is 70 per cent ground granulated blast furnace slag – recycled material from power stations – which, while considered “green”, means a longer setting time.
“We wait a couple of weeks before adding the top pour. In the old days ordinary concrete would have set in a couple of days,” said Shay.
Core temperatures are carefully monitored and the developers wait until the temperatures have settled before moving on to the next stage.
Next, a huge “can” is dropped into place over the vertical steel posts still protruding from the now covered “sieve”.
This cylinder is then filled with concrete, almost to the brim. This is the top pour.
Once set, this will become the base to which the turbine tower is bolted. Nothing but the brim of this base work, will be visible above ground once complete.
Shay is very aware of the amount of damage to local roads, particularly as lorries access the site from Hore Down Gate.
“We have an inspector who comes out regularly from North Devon Council and we will reinstate the roads where they have been damaged, when he tells us they have worn out,” he said.
The Journal is following development of the site and will report on the next stage in development, when the giant sections of turbines begin to arrive in the spring.
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