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Home / Notice to Mariners / Navigational Information Thames Estuary Windfarms 2021
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Home / Notice to Mariners / Navigational Information Thames Estuary Windfarms 2021

Navigational Information Thames Estuary Windfarms 2021

Plans this Season

I regret my schedule so far this season has slipped but I am now afloat and I hope to be about in the Estuary very soon. Unfortunately because of the late launch (all my fault on account of the lock-down and fitting all the new kit) I have missed undertaking the re-survey of the SW Sunk. Today is the last suitable tide on Spring Tides and I need to finish off some calibrations before I could start. So the plan is for the next Spring Tides between 25th and 29th May. I have not heard of any reports so far this year so whilst I expect the SW Sunk to still be in the same place, it cannot be guaranteed. So using the Little Sunk crossing might be more reassuring. The Little Sunk is a very stable plateau of sand and over recent years has little changed.

Most of you will know that I monitor weekly Notices to Mariners and I can report there has been no Admiralty Notices that has affected any of the routes. However there are two 'Local' Notices that merit attention. The first affects the London Array Wind Farm and Foulger's Gat; the second, the Wallet, the Rough shoals and the Sunk Precautionary Area.

Foulger's Gat: The London Array Wind Farm started a six monthly programme of maintenance involving some extensive diving and 'roping' turbines for work aloft. This involves a series of temporary exclusion zones and when the works affect turbines on the border of Foulger's Gat and the 'dogleg' we will need more caution and indeed where two turbines adjacent are both being attended, the Gat might be difficult to use. You will know there is a standard permanent 50m radius advisory caution zone is established around each wind turbine and offshore sub-station platforms. During the 6 month programme the following additional exclusion zones will apply:

A 100m exclusion zone will be in place during rope access operations.

A 250m exclusion zone will be in place when dive support vessel moorings are deployed at WTG's.

A 500m exclusion zone will be in place during dive operations.

To see the full Notices to Mariners go to:, select the 'Local Authority' List and you will see a synopsis and buttons for the download. This image below shows in magenta those turbines that will be affected.

I have asked the London Array if we could be forewarned before those turbines bordering the Gat and dogleg were selected but they have told me that as local conditions will dictate the choices for the locations at short notice. So we are told that daily warnings will be broadcast on VHF Ch 16. We should also call up any London Array vessel irrespective of the absence of any Ch16 broadcast prior to entering the Wind Farm.

North Falls Offshore Windfarm; Geophysical and environmental site investigations

Site investigations will affect the Wallet, the Rough Shoals and the Sunk Precautionary Area but will only last for 8 to 9 weeks.

North Falls Offshore Farm Limited has contracted Fugro GB Marine Limited (Fugro) to carry out a geophysical and environmental site investigation in the North Sea for the proposed North Falls Offshore Wind Farm (NFOW) site.

The North Falls Offshore Wind Farm site is located to the east of Felixstowe and bordering the Greater Gabbard and Galloper existing wind farms.

The geophysical operations at the North Falls site are expected to be carried out from the Fugro Mercator from 10th May 2021 for approximately 8-9 weeks. Fugro Mercator will be conducting operations across the Main Array and Export Cable Route areas >10m LAT. Please note that the exact start and finish date will be dependent on the prevailing weather conditions and work progress.

As the Fugro Mercator will be towing survey equipment the vessel will require large turning circles and will be restricted in her ability to manoeuvre. All vessels operating within this area are requested to keep their distance, maintaining at least the 1,000m safety zone around the survey vessel, and pass at minimum speed to reduce vessel wash.

If you go to the same 'Local Authority' List on: you can see and download a chartlet showing the locations of the works. Like the London Array no dates for detailed locations are available but using AIS if available might well be useful forewarning.

I would suggest you use the Notices to Mariners page prior to a passage as the latest available information will be added every Monday evening.

Plans for the Season

The SW Sunk swatch will be completed first, probably the Middle Sunk next. I will also do the Spitway and Ray Sand and possible the Little Sunk.

I hope your plans can be achieved this year. By all means email me if you have any questions.

Happy sailing


Last updated 07:50 on 17 May 2021

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