Wrecking the Sea Bed with Offshore Wind Part 5

This is the fifth and last 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 )

I hope I have shown in the first four posts (using the Navitus' own documentation) that the small power plant that would be Navitus Bay Offshore Wind park will involve massive damage to the seabed.

Just to summarise from previous posts: 

The foundations will  involve ripping up around one and a half million tonnes of seabed. This damage coupled with disposal of the spoil will wreck around 1000 acres of sea bed - or around a total of 4 square kilometers.  

Several hundred miles of undersea cabling will involve trenching, ploughing and jetting into the sea-floor. The debris will spray out, burying everything within a 5 -20 meter wide corridor. Though a plume of finer debris will extend much further. So another 1000 acres (or another four square kilometers) of sea bed will be trashed. 

On top of this cabling sea bed disturbance, there will be dumped  over a third of a million tonnes of rock debris to protect the cables from being accidentally trawled up.

But it does not stop there. There is even more rock debris required. This rock is known as anti-scour.

Anti Scour

The Navitus Wind Park (like any other offshore wind farm) will need thousands of tonnes of imported rock piled around the bases of turbines to prevent the foundations being undermined by scouring. 

This anti-scour rock debris will essentially form a foreign and unnatural marine environment around about 30% of the turbines. Typically, each anti-scour ring will measure  25 meters in diameter and be 2 meters thick. (para 2.70)

A ring that size will account for about 1000 tonnes of rock debris per turbine or around 70,000 tonnes in total for the proposed 30% of turbines (para 2.68) that will need the anti-scour.

In addition to this there is additional anti-scour to cover the cable entry points (this is in addition to the rock used for cable protection described in a previous post). This will be needed on an unspecified proportion of turbines requiring anti-scour (para 2.71). Assuming 40 turbines need this and it will be as thick as the anti-scour itself then this will be another 30,000 tonnes of rock debris.

In total the anti-scour alone will involve importing another one hundred thousand tonnes of foreign rock and dumping it into the marine environment directly off the World Heritage Jurassic Coast.

The suffocation of the natural environment around these turbines by building what are essentially artificial and foreign habitats will no doubt, over time, also import foreign wildlife into the area (as has happened elsewhere - para 9.121). With the excavation and  dumped spoil, this anti-scour will inevitably skew the current balance of the existing wildlife within the turbine area. No doubt some species will prosper. But others may collapse as they struggle to compete in what is to them an artificial and chaotically changed environment. Sadly though it does not end there.

Effect on Tidal Flows

Although the potential gains from this scheme are pitifully poor, it will still be a huge artificial structure. In fact a structure so enormous and so intrusive on the natural environment that it will actually slow down the tidal flow rate by 7% within the turbine area and cause a flow speed increase outside. In an area already suffering from considerable marine coastal erosion, having a structure that speeds up tidal flows north (i.e. landward) of this structure would appear to be careless - to say the least. (para 5.325)

Finally I'll point out that this thing is so big and intrusive on the natural environment it could actually cause a change of tidal phase where the peak rate of flow may be retarded by a full 10 minutes (para 5.325).

Finally I would like to bring up a topic nobody is talking about although I suspect it is a topic many involved with this project are fully aware of.

Sea-bed Methane Release

Coastal sediments can potentially hold large quantities of Methane ( see paper Reindl & Bolalek link - Here ) & ( paper Mascharka, Montross, & Pierrehumbert link - Here )

Whenever you disturb ancient coastal sediments you are guaranteed to release trapped seabed Methane. Large Dredgers (as an example) are usually fitted with methane extraction and venting equipment to prevent the risk of explosion (See The Art of Dredging - Here ). But here the problem is not so much tied up with an explosion risk as to the fact that methane is a green house gas 20 times as potent as CO2. 

It would be high farce for this monstrosity to be built only to do more damage to the atmosphere than it is optimistically slated to offset. It is difficult to see how that trenching and ploughing an area equating to 1000 acres then excavating a million and a half tonnes of seabed can do anything but release copious quantities of trapped coastal seabed methane. 

Somehow this possibility appears to have been missed out of the Navitus documentation altogether.

So finally - What Exactly will be the Environmental Gain?

Sadly the pillage and destruction described here are just the tip of the ice-berg. 

In these few posts I have dealt solely with a sub-set of the sea-bed damage caused by offshore wind farms. Nobody seems to have publicly paid much attention to this, although to be fair English Heritage has raised the alarm (table 9.2). Perhaps the surface calamities threatened by these offshore projects are so awful they push other unseen destruction to the back of people's minds.

A very good site detailing other major problems with offshore wind (particularly Navitus) is on this link - Challenge Navitus - Here 

Most of all though, let us just remember that all this destruction and upset to a fragile and internationally recognised coastal region is to provide a SMALL intermittent power supply of typical daily output of 250 MWe or less.

Even then, simply to be viable, this offshore wind farm will have to be paid around three times the typical electricity wholesale cost.

If we leave aside the quasi-religious zeal, the vacuous fashionability and the endemic greed that drives this foolishness, can anyone really give a good reason to desecrate this coast (or any other) for so little gain? 


Rick Kargaard said...

I read your posts on offshore wind with interest. I am niether an advocate or opponent of wind power but I do share many of your concerns with offshore installations. I don't really believe they are necessary as many onshore sites are available or there are other alternatives. Some exceptions might be for countries like Denmark with tiny land bases and a dependence on imported fuel.
I hope your blog get's some notice

BilloTheWisp said...

Sadly, while onshore turbines are undoubtably easier to maintain they are less able to generate power and also in most cases (certainly in the UK) have a severe impact on local communities.

Except for niche applications wind power (either onshore or offshore) is unsuited to large scale energy production.

Onshore as well as offshore wind is locked into and driven by a subsidy regime. It is essentially otherwise unviable.

The turbines (even onshore) are too expensive (both to buy and to maintain) compared to the amount of energy they produce.