The London Array - Rock Berms - a fresh warning - Kentish Flats and Princes Channel

[Tiller Girl]

I have received a nice email from Dong Energy regarding their Rock Berms at the locations where the London Array cables cross over the Kentish Flats Wind Farm cables (on the Kentish Flats) and where the London Array cables cross over the BritNed power cable just west of the Princes South port hand buoy. Both locations have, of course, been marked by new buoyage certainly for over a year, if not two.

The point of the email is that London Array vessels have noticed leisure craft apparently ignoring the buoyage and they are trying to bring renewed attention to the dangers. Many here will recall that the crossing point on the Kentish Flats is 0.9 LAT and in consequence is marked by three special buoys and a south cardinal. That just outside the Princes Channel is 4m LAT and is marked by the north cardinal buoy BRIT N.

I am sure many if not most if not all forumites here are aware of these berms but there is no harm in an additional warning. There is a chartlet (the bottom one) on my downloads page at http://www.crossingthethamesestuary.com/page29.html. The coordinates if they help are:

Kentish Flats/London array cable crossings have marker buoys at the following locations:

51° 25.56N 001° 06.45E (KFSM1)
51° 25.00N 001° 06.44E (KFSM2)
51° 24.86N 001° 05.77E (KFSM3)
51° 25.41N 001° 05.69E (KFSM4)

2. BritNed cable crossing (51° 28'.583N, 001° 17'.417E).

At this crossing the seabed level varies from -6.5m LAT to -9m LAT. Due to the newly installed rock berm the depth in some areas is now -4m LAT.

A North Cardinal Buoy has been installed in the following position: - Named BRIT NORTH
51°28.718N 001° 17.50E North Cardinal exhibiting Q light characteristic

 

[FulmarJeddo]

This has probably come about as there is an exposed new cable from the Kentish Flats extension and there has been a guard vessel on duty for some weeks now. On Saturday they seemed to be getting a little exasperated warning approaching craft to avoid it. There seemed to be a lot of Dutch boats heading that way. One that I heard challenged on the radio seemed to be aware of the yellow buoys marking it and intended to alter course when he reached there. I wondered which route he was taking as the berm isn't really on any of the through routes. I did wonder if he wasn't aware of the changes and heading for the old Hook Spit and East Last buoys rather than Copperas.

As this new cable follows the route of the original cables, from the Kentish Flats to Hernebay, I wonder if it goes over the existing berm and will have another pile of rocks on top, further reducing the 0.9m depth and making an island or runs alongside the existing berm that will mean the berm will become larger.

 

[Tiller Girl]

I am sure you are right about the source of the information. One of my routes which uses the Queen's Channel to go from Swale to North Foreland (I was asked to include it by some Kent based readers) does go just south of the four buoys so I might have some responsibility in this matter. However, in my defence I do mention the need to avoid this berm and the route clearly clears the buoys to the south. Hopefully any additions will be alongside the existing and thus just extend the shallow bit within the marked area; in fact surely they will as the London Array goes over the top of the Kentish Flats cable and it would surely be a bit daft to add the new KF cable over the top of that sort of pat-a-cake style. But then what do I know? Looking at AIS now, the Bianca is there as Guard Ship pretty much on the spot.

 

[Cantata]

In my talks over the past few years I have described the KF/LA cable crossings dilemma and jokingly suggested that the pile could become quite high.
However my reading of the notices regarding the new KF export cables was that they don't run straight over the same pile, although the new crossing points should still be within the existing buoyed area. They were going to protect the cables with 'concrete mattresses' this time, which I presume are less altitudinous than rock berms.
The buoyed area is indeed not on a direct route and I'm surprised that there are still skippers out there who don't know about it. Or perhaps I'm not. It's blee*in obvious anyway when you get there that there are buoys round something and perhaps it would be a good idea to go round them. Except in poor viz I suppose. Hey ho.

 

[bluerm166]

Well,I hope this is a reminder not only to sailors but particularly to the developers of the Kentish Flats and the London Array of their joint ommission in failing to cater for this crossing in the design stage.It doesn't surprise me that parking a shallow underwater obstruction some half a mile square bang on what was formerly a pretty direct route out of the Four Fathoms Channel on the Overland route to the Copperas channel ,as marked on the charts,would cause problems to those who those unfamiliar with the area - particularly as the three smaller buoys are difficult to spot in a sea state (even when you know they are there) and being so far apart are not associated with the same extensive hazard.It seems very natural that boats will pass close to the cardinal and that should they err in passing well north of it they find no help in the buoyage.I would have thought that the addition of at least two further intermediate buoys on each leg of the 'square would not be unreasonable.Buoys large enough to spot at a distance would be a great improvement.

 

[Cantata]

In the beginning it was worse than that. The LA developers used the 'lob it out and see if anyone notices' technique. So they did indeed describe the cable crossing that they would create, but nobody noticed.
Then one day they issued an NtM saying they had dumped these rocks and the least depth was 0.9m. We sat up and took notice. While still wondering what action to take, the next day a fisherman at Whitstable told me "0.9m be blowed, it's awash".
So we wrote pronto to Trinity House in the first instance, copied to the RYA-SE. We never actually heard what went on, but presumably sh*t hit fan.
Shortly afterwards, LA were made to buoy the area, which they initially did with four lit yellows. A local (a forumite) then pointed out that if you arrived in the area in poor viz and saw a yellow buoy it would be useful to know which way to turn, hence the southernmost was swapped for a cardinal.