Clearing mud from marinas - progress ?

[sarabande]

I read that the Environment Agency (blessings upn them ) have given permission for mud in the rivers on the Somerset Levels to be squirted into the outgoing flow and carried out to sea.


What about Watchet, Brighton and other marinas affected by sedimentation ? Why can't this process be used for what are very minor quantities of mud, which under natural conditions would be swooshed out to sea any way ?


http://www.bbc.co.uk/news/uk-england-somerset-37999016

http://www.somersetlive.co.uk/somer...r-bridgwater/story-29906414-detail/story.html

 

[sailorman]

The Orwell dredging has to stay within the bounds of the river & squirted up into the shallows.

 

[prv]

What about Watchet, Brighton and other marinas affected by sedimentation ? Why can't this process be used for what are very minor quantities of mud, which under natural conditions would be swooshed out to sea any way ?

Is there much flow through Brighton for it to be swept out by once stirred up?

Pete

 

[[70521]]

Just wait until the tide turns and the mud comes back up the river.

 

[EdWingfield]

What nasties are in the mud?

 

[sailorman]

What nasties are in the mud?

Fertilizer & crop spray run-off

 

[EdWingfield]

I don't know about fertiliser and crop spray. My local marina has heavy metal (antimony I think)

 

[ghostlymoron]

Dredging can often can unforeseen consequences. My mooring is in Mochras Lagoon, Wales, last year they dredged the harbour at the adjacent Shell Island harbour and dumped the spoil out to sea a bit. The channel through the lagoon moved north several metres so I had to relocate to a spot about 30 metres from it. This year, the channel has followed me north and I'm again right on the edge so I'll have to move again. It is thought that last year's movement was caused by the dredging.

 

[Yngmar]

Brightons new cutter suction dredger "Doris" has finally arrived some time ago. And a mud pipeline has been laid under the pontoons, all the way to the east breakwater, through it, and to a marker buoy well outside the marina. Unfortunately the whole contraption doesn't seem to work right yet (only cost a million or so though), so it hasn't been seen dredging much at all, and apparently is now being winterised until spring. Oddly enough, a new marina manager has just been announced. Hmm! So berths are still not dredged and there is nowhere except maybe the visitor pontoons for a 2m draft keel to not run aground at low water springs. No discounts are given on account of lack of water under your berth (I asked).

The main channel to the fuel pontoon is passable (and the workboats on the wall are gone), and the entrance is dredged, although much narrower than it used to be, so stay well within the markers or you may suffer the fate of a dutch boat that entered in rough conditions, got picked up by a wave, surfed a bit and was ungently deposited on a piece of shallow ground. After emergency liftout the keel was found to be wobbling, so the cruise was over, the mast unstepped, both loaded on a truck and carted back to a dutch boatyard for repairs. :dejection:

 

[Mandarin331]

This type of dredging can be very effective in the right circumstances, ie mud type, tidal flow etc, Brightlingsea harbour dregded the marina this way last winter and are now starting in the main channel. It needs very careful assessment before and during to ensure the mud is going where expected.

Strange that Brighton have stopped for the winter, that's when Marinas normally do all the dredging.

 

[Yngmar]

Strange that Brighton have stopped for the winter, that's when Marinas normally do all the dredging.

Apparently the part of the mud pipeline outside the breakwater gets retrieved for winter (it's held on the seafloor by large concrete mooring blocks) due to concerns about wave damage. I was told this is all a brand new concept and there is some learning curve. It certainly looked like there was one when the pipeline was installed

 

[Seajet]

Chichester Harbour has a dredger on the entrance every so often - God knows they should be able to fund it with 10,000 people paying handsome dues - but I wouldn't fancy even a small ship's chances on the bar over winter.

Seeing as the council dump sand & shingle etc on the beach right beside the entrance, it doesn't take a genius to see why the depth keeps shoaling...

 

[johnalison]

We found half of Brighton closed for dredging a few years ago. We were told that it had to be done in the summer because they weren't allowed to do it in winter because of juvenile bass or summat.

 

[Boo2]

Apparently the part of the mud pipeline outside the breakwater gets retrieved for winter (it's held on the seafloor by large concrete mooring blocks) due to concerns about wave damage. I was told this is all a brand new concept and there is some learning curve. It certainly looked like there was one when the pipeline was installed

How do they get the mud from the dredger to the pipeline ?

Boo2

 

[Triassic]

Fertilizer & crop spray run-off

Aren't you the lucky one..... I just wish our local mud was half as nice as that!

 

[Yngmar]

How do they get the mud from the dredger to the pipeline ?

Boo2

There's a rigid pipeline running the length of the marina under the northernmost pontoons (by the wall), which a "soft" kind of really big firehose connects to and the other end goes to the dredger, which pumps the mud through this rather long run. Supposedly. Whenever the dredger changes its working area, that stuff is relaid (and the rigid pipe can be split/teed into at different parts), and obviously some boats cleared out of the way too. Right now you can see the soft part run along the east side of the west jetty, held up with a few orange mooring buoys. It ends somewhere near the visitors pontoons in front of the office.