Wrecking the Sea Bed with Offshore Wind (Part 4)


This is the fourth 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_9_benthicecology.pdf (Link HERE)
PEI3_Ch_10_fishandshellfishecology.pdf ( Link HERE )

Foundations and Waste - adding it up


Yesterday I looked at the devastation wrought on the sea bed by a single gravity base turbine. In that scenario the spoil from the foundation excavations were dumped nearby.

There is an alternative to this. Instead of dumping the spoil on site it can be dumped elsewhere. Maybe at a nominated disposal site within the Solent itself.

Of course, for a single turbine, the disposal of several thousand tonnes of seabed spoil, whether locally or to a waste dump is unlikely to cause significant problems to the area as a whole. When regarded as a single entity, the waste issues caused by an individual turbine (while lamentable) are negligible within the bigger picture. 

The problems come when you add it all up.

Potentially, for the 213 turbines plus three substations a met mast and other assorted sea bed scrapings, the amount of displaced spoil comes in at well over one and half million tonnes. Even if they end up with a significant number of turbines that use foundation techniques that generate less spoil it is highly unlikely that the amount of seabed spoil will ever be less than about 1.2 million tonnes.

Remember this all gets excavated fairly rapidly over a four year period.

So how much is 1.6 million tonnes of sea-bed?

It has a volume of about 860,000 cubic meters. To give an idea of how much that is, let us build a solid cone of spoil sitting in Bournemouth Square. The base of this cone needs to be 100 meters across (325 ft). Now imagine building your cone upwards.

Do you remember from earlier how a 100m wide cone of rock debris (used to armour the cables) reached  beyond the height of Westminster Abbey?

Well, for this mountain of sea-bed spoil, that's kids stuff.

As you keep building it upward don't look back as you go past the height of Big Ben (96m - 300ft.) Keep going past the height of the London Eye (135m – 443ft).

You've got a helluva long way to go yet.

Keep going until you reach the height of the Shard in London (London's highest building 310m – 1017 feet). Take a quick breather if you like, but you are not there yet.

Keep on building up beyond the Eiffel Tower (324m) – but keep going.

You end up running out of spoil 40m short of the top of the Empire State Building in New York. The final height of your 100m wide solid cone of seabed spoil will be 344m - 1128 ft.

Now remember, if you plan dumping this mountain somewhere other than by your turbines, you will need to find a way of bringing it all back again during decommissioning. It will be needed to fill those craters left when you dig out the foundations of the defunct turbines. Or is there some other plan (if any) for this eventuality?

From the environmental assessments that form part of the Navitus documents, it appears that the disposal of this mountain of spoil will have a “negligible” affect on the environment. In fact “negligible” is a much used word in this documentation. It vies with “imperceptible” for popularity.

A Little Parallelism for you.

If I go to an ancient Oak forest and cut down and dig up an old Oak, the effect on the rest of the forest is probably “negligible”. The trashed area will no doubt recover in a few years. Then lets say, three days later, I do the same thing again. This is a large forest so again the effect is negligible. Then I do it again and again. I keep going for four years. Each Oak cut down makes a negligible change to the forest. But at the end of our four years of "negligible" destruction, we end up with a scene of desolation. A brutalised and trashed environment that will take, as a whole, very many years to recover (if at all).

I hope you can see the parallel with building an offshore wind park.

I was going to deal with heavy metal pollution and methane release from the spoil as well today but this post is too long already. That will come on another day. Sadly there is so much wrong with offshore Wind (and  Navitus Bay in particular) that I'm going to be at this for some time.

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