Wrecking the Sea Bed with Offshore Wind (Part 3)


This is the third in a series of posts about the damage done to the sea floor by offshore "Wind Parks". Data has been taken from the proposed Navitus bay wind park consultation documents (Available On This Link) which are also available on a DVD. The main files are:
PEI3_Ch2_NavitusBayWindParkProject.pdf  ( Link HERE )
PEI3_Ch5_PhysicalProcesses.pdf  ( Link HERE )
PEI3_Ch_10_fishandshellfishecology.pdf ( Link HERE )

Foundations and Waste

While the sea bed is being dug up with hundreds of miles of cable trenching (see last post), the average offshore wind park will also be gouging out the seabed for the foundations for the turbines themselves. 

Take a single gravity base turbine. 
PEI3_Ch5_PhysicalProcesses.pdf  

The concept appears to be that the sea bed is variously excavated, levelled and generally dug over and the 7600 Tonnes of spoil from these operations is shipped to the surface. The gravity base structure is then built on top of part of the excavated area. The final coup-de-grace to the area is then executed by rapidly dumping the spoil in the vicinity of the turbine base.

Over a period of a few minutes, directly below the spoil barge, a devils rain of 4800 tonnes of boulders, stones and gravel smash into the sea bed destroying everything in its path. As the waste piles up it will collapse and spread out, cascading outward like magma from a volcano. The area of destruction is likely to be well over 100 meters wide. 

Within this area everything dies. 

Flora, fauna, starfish, crabs, everything. It is unlikely that even fast swimming fish would escape the devils rain but even if they did, they are not going to live for long. Nature does not favour creatures evicted from their immediate habitat. Survival would be the exception rather than the rule.

That accounts for 4800 tonnes of the spoil. Then we have the remaining 2800 tonnes of mud and fine sand to consider.

The sea acts like a filter. The large rubble in the spoil falls directly to the sea bed leaving the smaller particles in suspension. The rate these fall to the sea bed is dictated by their size. A large opaque bloom of debris will spread out from the dump site flowing along with tidal direction. It will (mostly) sink as it travels. While some of this debris will remain in suspension for days, most will smear out a suffocating coat of mud over the sea bed extending out hundreds of meters from the dump site. Assuming a suffocation depth of 10cms and that 500 tonnes of the particulate matter is fine enough to remain in suspension, the remaining 2300 tonnes has the capability to extend the destroyed area by another 10,000 square meters.

So this single turbine has the potential to destroy an area of sea-bed equal to the excavated area (para 5.155) plus the area of the dump site and a further area suffocated by mud

2000 square meter excavated area
7500 square meters destroyed by large spoil
10000 square meters suffocated by mud

Thats not far short of 20,000 square meters of sea bed totally destroyed and left devoid of life - a ring of death with a diameter of over 150 meters.

From the documentation Navitus optimistically report that the environmental damage will take around 5 years to heal.

Really?

While this may be true for the mud polluted areas, it is difficult to see how areas covered with large amounts of immovable rock, shingle and boulders, piled haphazardly on the what was the sea bed will recover. You have dumped what amounts to 7600 tonnes of (at best) sub-soil on what was the sea bed.

Ask any gardener how well plants grow in mining spoil. Ask the older people in the valleys of South Wales how well vegetation grew on the spoil heaps that were imposed on them.

Truly, life is tenacious. It will in some form return to the devastated areas. But the likelyhood is that the balance of flora and fauna will at least be different and more likely to be diminished and enfeebled.

All of the above is for a single turbine. Navitus plan to build 213 of these things. 

The seabed “preparation” will be done at 3 day intervals. Every 15 working days another 100,000 square meters of sea bed will have been destroyed. This will go on for four years.

Even on their own reckoning, by the time they have trashed this 1000 Acres of sea-bed none of it will have had time to recover.

Now add this 1000 Acres of devastation to the 1000 acres of ruin brought about by the cable laying and the cable rock armour.

All this for a pitifully inadaquate, intermittent and massively expensive power generation technology.

Ruin upon ruin. 

But it does not stop there. Next I will look at the scale of the total amount of spoil produced and also some of the less desirable elements within that spoil that will be released into the marine environment.



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