Notices to Mariners - Week 3

[tillergirl]

UKHO Permanent/Temporary/Preliminary Notices
Just the 1 this week

FRANCE - North Coast - Automatic Identification System. - Temporary notice advising that the south cardinal buoy ‘DY2’ in the Dyck Oriental channel (offshore north of Dunkerque) has its AIS temporarily removed.
Local
1. Gravesend Reach to Northfleet Hope - Dredging Operations - On or around 8th January 2025, the vessel AQUADELTA will commence water injection dredging operations at the entrance to Tilbury Dock & Tilbury CMAT. Works are expected to take no longer than 5
working days. Dredging activities from the vessel AQUADELTA will only take place on ebb tides at the locations indicated. See the image at: Notices to Mariners. Requirements to proceed with caution or at slow speed will be made in accordance with the procedure set out in the Port of London Authority’s Port Information Guide, under ‘London VTS’, ‘Section 4’. International Code Flags ‘Romeo Yankee (RY)’ will be displayed accordingly.
2. Dredging Works at Shotley Marina - Mariners are advised that dredging works will be taking place at Shotley Marina from 06 January 2025 for approx. 5 weeks. Works will take place Monday to Friday between 08:00 and 16:00. Contact Shotley Marina (VHF Ch.80) for further information.
3. Surveyed Depths – Harwich International Port and approaches – Update 1 - recent surveys have identified the following depths in the approaches:
• Area dredged to 8m (not including berths): Minimum depth – 8.0m below chart datum
• Area dredged to 9m (not including berths): Minimum depth - 8.9m below chart datum
See survey chart extracts for further information and berth depths. Go to the above quoted webpage and select the local list. For further information contact the Harbour Master Team at Harwich Haven Authority (+44 1255 243030).
4. Surveyed Depths – Harwich Deep Water Channel – Update 6 - the latest hydrographic surveys showing depths in the Harwich Deep Water Channel. The minimum available depth of water on the centreline is approx. 15.9m below chart datum in the area of Number 1 Buoy, with the channel predominately at 16.0m BCD or greater. There are shallower sections including sand waves on the centreline and towards the channel edges Contact Harwich VTS or Haven Pilots for further information. This local notice to mariners is cumulative and replaces notice 62-2024 which is now withdrawn.
5. Surveyed Depths – Harwich Harbour – Update 12 - the latest hydrographic surveys showing depths in Harwich Harbour. The controlling depth for deep draught vessels navigating within the harbour area should currently be taken as 15.4m below chart datum, plus height of tide. The minimum depths below chart datum (not including inside berth boxes) are:
• 15.3m - spot soundings between the Shotley Spit Buoy and Babergh Buoy
• 15.5m - spot soundings between the Grisle Buoy and Shotley Spit Buoy
• 15.4m - spot soundings between the Fort Buoy and Grisle Buoy
See survey chart extracts at the above quoted webpage for further information. Subject to availability of a suitable tidal window, vessels up to 17.0m maximum draught may be accepted. Contact Harwich VTS or Haven Pilots for further information.
6. River Medway – Gillingham Marina to Hoo Marina - Hydrographic Survey of Gas Pipeline - ‘Northern Divers’ will be conducting a hydrographic and “walk-over” survey of the River Medway between Gillingham Marina and Hoo Marina. The survey will be concentrated over the sub-sea gas pipeline running between the two locations. (See local list on the webpage quoted above). Survey work will commence 14/01/2025 and is expected to be completed by 17/01/2025. Multiple survey runs will be performed at slow speed over the low water periods using a RIB Callsign “Northern Divers Sea Rover” who will be monitoring VHF Channel 74 at all times. All work will be completed from the surface and across the mudflats during multiple low water periods, NO diving will be undertaken. Please be advised that during survey operations the vessel will be restricted in it’s ability to manoeuvre and other vessels are requested to be mindful of the nature of the works, reduce their wash when passing, maintain an appropriate safe distance and monitor VHF Channel 74 at all times. Admiralty Charts : 1835 & 2482 refer. Further information may be obtained from Medway VTS on VHF Channel 74, call sign “Medway VTS” or telephone 0151 949 6148 or 0151 949 6650 (Recorded Lines).
7. MDL Woolverstone Dredging - that dredging works will be conducted at MDL Woolverstone from Thursday 9th January for a period of 6 weeks. The works will be undertaken by the vessel CH Horn. The vessel will dump the spoil at the River Orwell disposal site TH 034.
The CH Horn will maintain a listening watch on VHF CH68 at all times. Mariners requiring more information should contact ONS on VHF CH68.

That's it.

 

[Lucky Duck]

Good to see they are dredging the basin at Shotley as I understand they weren’t accepting visitors during last September’s neaps due to worries about the water level dropping

 

[spray]

A neighbouring berth holder tried to lock out during dredging and despite giving plenty of notice the delay to exit was too long for his trip, so he cancelled . This dredging will go on for about 6 weeks and I for one of many are disappointed with the management for not giving us much notice of the disruption and making it easier to transit the work in progress. 6 weeks out of 52 at the marina’s berthing fees is significant.

 

[Daydream believer]

A neighbouring berth holder tried to lock out during dredging and despite giving plenty of notice the delay to exit was too long for his trip, so he cancelled . This dredging will go on for about 6 weeks and I for one of many are disappointed with the management for not giving us much notice of the disruption and making it easier to transit the work in progress. 6 weeks out of 52 at the marina’s berthing fees is significant.

So you expect to go in & out of the marina every day for 6 weeks this time of the year do you?
Try looking at it this way
1 day in 365. Might make your neighbour feel better.

 

[spray]

Good to see they are dredging the basin at Shotley as I understand they weren’t accepting visitors during last September’s neaps due to worries about the water level dropping

So you expect to go in & out of the marina every day for 6 weeks this time of the year do you?
Try looking at it this way
1 day in 365. Might make your neighbour feel better.

Well it will be much more than 1in 365and some of us like to use our boats frequently during the winter months, the waters are not over crowded and engines don’t like sitting idle. Presumably you keep your boat ashore during winter.

 

[shanemax]

As Shotley marina is lock controlled any dredging required must be mud washing off the land due to rain ???

 

[Snowgoose-1]

River Orwell disposal site TH 034.

Thanks as always for your efforts.
Any idea where the disposal site is on the Orwell ?
I have looked online without success. I have a feeling that it is on the south side between
Levington and Shotley marinas.
Thanks.

 

[PeterBoater]

As Shotley marina is lock controlled any dredging required must be mud washing off the land due to rain ???

No, it's silt that comes in during freeflow. The webcam shows the fishing boats moved to the fuel pontoon to get in and out.

 

[tillergirl]

River Orwell disposal site TH 034.

Thanks as always for your efforts.
Any idea where the disposal site is on the Orwell ?
I have looked online without success. I have a feeling that it is on the south side between
Levington and Shotley marinas.
Thanks.

These are the HHA disposal sites


I don't know whether one is the same as the TH034 site. There are a couple of sites around the Roughs but I would be surprised if the Marina spoils went 'outside'.

 

[Egret]

The whole question of silting/sand movement/reducing depths would be worthy of another thread. So much silt build up now everywhere. Redepositing it locally it will just come back. Maybe need to find a way of turning it into something that can be sold and re-used. Some salt marsh restoration but not much. The silt must come from the land initially. Colchester silted up very quickly once ships stopped visiting in '88. There was thought to do some dredging and promote leisure use but spoil would have to be taken to 'out beyond the Thames estuary area' so uneconomic as couldn't dredge on high tide get out and back to be ready to dredge again on the next high tide. Tests indicated that the silt was nearly all inorganic so off fields originally probably, very little organic so not as much shell/worm bodies and not as much contaminants in the silt as might have been expected. (In other places and times it may be different). Would be interesting if someone put a tracker in the deposits to see in which direction the silt travels - maybe into the deep water channel then off to the Roughs that way. Hopefully not towards Manningtree. BGS Geology sea bed map is interesting - silt/mud deposits mainly near rivers.
Edit -Note that the map above #9 is for ';sediment replacement'; - perhaps there is reason for the sediment to be placed there for biodiversity or to keep the little creatures in the silt within the river - someone might know. We know about longshore drift but would be interesting if anyone knows of studies of silt migration in the public domain.

 

[Daydream believer]

Would silt carried in suspension, by the tide have any bodies in it? It would seem to be inorganic- would it not? It is not like material dragged along the sea bed, as one gets when a sand bank moves. That drags shells worms & other bodies along with it.
Or am I totaly wrong on that?

 

[Malish]

Most dredging disposal sites are within the river system, few are on land these days, all controlled by environmental regulations. In many instances 'dredging' is achieved by disrupting the sediment and putting it into suspension within (ideally) a falling tide, so it is more like dispersal then removal. The sediment itself comes from various sources: down river, from land drains, from coastal erosion (e.g. the London Clay cliffs on Sheppey or erosion of salt marshes) and yes, there is a significant organic component too. Silts and clays remain in suspension until water is very slow moving or until they flocculate (stick together to form larger entities; which also happens when they move from fresh to salty water). The turn of the tide is the clssic time when some sedimentation occurs but at least some material will return to the (wider) area that it came from. Clays tend to remain stationary once they are settled and not resuspend without an energy input (think how sticky a mud is compared to a sand). In many cases the relevant authorities are simply moving this material around or expelling it from a location for their local benefit. Sometimes areas are identified for sediment recharge where there is then a more proactive identification of an area which is suffering erosion and which need replenshment and this can be incoporated into derdging plans and seen as a positive benefit; most of the time the sediments simply accumulates somwhere else...