What a way to wake up. 150m dredger right beside us.

[Franziska]

Hi,

I am not sure where to post this, but it may spin into a safety discussion, hence I put it here.

We are currently at anchor in a designated anchor area in Leixoes Port (Oporto, Portugal).
A Dutch company is dredging the harbour with a number of vessels, amongst them some of the biggest of their kind in the world.
The anchor area is not cordoned off and noone came to ask any of the yachts to move.

This morning the 150m long hopper suction dredger woke us up, working not even 50m. 2x 1.20m suction pipes make for an infernalic sound :-)
We did not feel threatened, because we saw the green giants moving about very gently yesterday, but, the sheer size and sound give you some pause.

Do we have anyone here who has been professionally involved in dredging who can explain how they avoid sucking up chain, anchor or anything unwanted and the procedures they would follow if they did?

[Manateeman]

Are you concerned they will suck up your anchor ?

[Franziska]

I was pondering of what might happen if they did, they were really really close.

But it looked like they were also very professional, careful and under control despite the size.
Impressive manouvering for a vessel of that size.

[Franziska]

Originally Posted by Manateeman

Are you concerned they will suck up your anchor ?

Btw.
No Manatees or friends threatened, it's a big & busy commercial harbour.

He's still doing his business at 22.40 hours right now [emoji4] Guess 24h/7day/365days nonstop operation...

[JPA Cate]

@Franziska,

Well, from that, I guess the noise of sucking up all that loose sediment will drive you from the anchorage, soon. FWIW, (which may be next to zero!), I would think that since it is designed for the soft sediment sucking, it won't suck up an anchor and chain. But I'm no dredger, either. I'd go find another harbor in Portugal where that won't be a problem.

I wouldn't have liked to wake up that way, either. Compared to the big guys, our little boats are fragile. We approach docks with caution. I've never had a dock approach me!

Joking aside, why don't you go over there by dinghy and have a chat with the dredger crew? You could learn the answers to your questions from them; plus I'm sure it will be interesting. Take over a thermos of fresh coffee and some of those nice Portuguese donuts, "malasadas". I betcha you'd be welcome. In general, in ports all over, I've found those professional people respond well to friendly, interested-in-their-work yachties.

Ann

[carlosproa]

At least you are not the monohull in the right foregrounds

[GILow]

It all depends on what sort of dredging they are doing. Around here it’s the plain suction type (according to dredge guys I spoke to) but there are all sorts of systems including some that look a bit like those giant coal excavators. The latter sort would worry me, but I’d bet the operators would be more worried, considering the cost of the machinery. If they are working close to you I would trust they are on top of the risks.

Either way, I bet the water around you is far from crystal clear now.

It goes to crap when they dredge here in Adelaide, takes a good month or so to clear after they’ve finished. A few fellow cruisers who are wintering here were startled by how clear the water was a while back. I realised they’d arrived mid way through the dredging cycle and didn’t realise the horrible cloudy water was not the norm.

[RaymondR]

If it's a river port it is probably one of the pure suction dredges clearing out silt. If it's a deepening or extension it could be one of the ones with the rotating excavator on the end of the suction pipe. If it's a Dutch company they are probably pretty professional. There will more than likely be a shore based temporary office you could make inquiries at rather than approach the dredge in your dingy. They can be a bit touchy in these days of green activists etc.

[El Pinguino]

Originally Posted by Franziska

Hi,

I am not sure where to post this, but it may spin into a safety discussion, hence I put it here.

We are currently at anchor in a designated anchor area in Leixoes Port (Oporto, Portugal).
A Dutch company is dredging the harbour with a number of vessels, amongst them some of the biggest of their kind in the world.
The anchor area is not cordoned off and noone came to ask any of the yachts to move.

This morning the 150m long hopper suction dredger woke us up, working not even 50m. 2x 1.20m suction pipes make for an infernalic sound :-)
We did not feel threatened, because we saw the green giants moving about very gently yesterday, but, the sheer size and sound give you some pause.

Do we have anyone here who has been professionally involved in dredging who can explain how they avoid sucking up chain, anchor or anything unwanted and the procedures they would follow if they did?
Attachment 263503Attachment 263504

If you look at your second photo the actual dredging bit on that green dredger is on her starboard side so some distance even from the mono under her quarter.

Not a big risk in Portugal but further north they don't worry about yacht anchors so much as unexploded ordnance from WW2 - that really does get their attention Dredger working on waterway unearths unexploded ordnance from WWII - Poland at Sea - maritime economy portal

5.4 ton Tallboy?? -- Eeeeek!!!

[Franziska]

Thanks for the comments.

Got some new photos. One shows "Nile River" (https://www.deme-group.com/technologies/nile-river) the 150m "trailing suction hopper dredger" which was next to us with their suction pipes lifted.

The other one shows the cutting heads "Spartacus" (https://spartacus.deme-group.com/) which is the biggest of its kind on earth at the moment, is using at the harbour entrance.

I also talked with a guy on the survey boat, he said, not very reassuring, the big dredge would not notice if it would swallow a yacht anchor. Still, there is an emergency stop and I am pretty sure the guy on the dredger looks closely if one of the yachts suddenly starts moving very quickly towards him.
They deepened the harbour here from 9-11m previously to 16-18m now. Which took them about a year and is coming to an end now.

It's a commercial seaport, with a marina inside, and luckily for us, a yacht anchorage as well. We don't like marinas [emoji4]
Perfect location to visit the Unesco world heritage city of Porto.
The other anchorage on the river Douros entrance is very small, the marina over there very expensive.
There have been a few occasions when yachts could anchor a bit upriver but officials only tolerate that occasionally and could fine if they enforce it.
Btw. you can NOT sail past the Ponte Luis 1 in Porto if your mast is close to 10m or taller.

[AKA-None]

Well we had one in the shipyard once that hit sugar sand and packed all the pipe solid

It required disconnecting all the pipes and basically chiseling the sand out like concrete

Lots of suction and lots of material moved in short time

Heavy stout boats, everything was overbuilt compared to anything else I’d ever worked on

[Franziska]

Originally Posted by AKA-None

Well we had one in the shipyard once that hit sugar sand and packed all the pipe solid

It required disconnecting all the pipes and basically chiseling the sand out like concrete

Lots of suction and lots of material moved in short time

Heavy stout boats, everything was overbuilt compared to anything else I’d ever worked on

What is "sugar sand"?

[AKA-None]

Originally Posted by Franziska

What is "sugar sand"?

Fine grained similar sized sand grains held in suspension

The dredge picks it up and ends up pulling all the water out which causes it to pack tightly like cement

Pump stops and bob’s your uncle

[Franziska]

Originally Posted by AKA-None

Fine grained similar sized sand grains held in suspension

The dredge picks it up and ends up pulling all the water out which causes it to pack tightly like cement

Pump stops and bob’s your uncle

Wow. Nature amazes once more.

[AKA-None]

Originally Posted by Franziska

Wow. Nature amazes once more.

Nor more so when I saw the inside of that system Al plugged solid

I had to ask the dredge crew and they enlightened me