Dredging of tidal pool any ideas

[nashwen]

Hi
I have made a couple of attempts to empty the sediment from a large tidal pool, about 20ft in diameter and about 15ft deep until I hit the sand and gravel which must be at least 6ft deep at the bottom. I have emptied the pool of water, but I have not been able to suck up the sand and gravel with any real success. My last attempt was with a 3' trash pump but this would continually block up with the gravel, which is up to about 4' in diameter. Ideally I need something that can suck up through a 4' soil pipe or something. There is about a 1k walk to the site with a 200ft scramble down to the bay. By bout is easier but there is a 13m tide here and very few days when the water is calm enough to get a small bout over the pool. I have a 5.5m rib. The pool is flooded by the tide for about 5hrs per day. Any ideas or advise would be most appretiated.

 

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[KevGA]

Not to get all crunchy on you, but do you have any idea what you are doing to the habitat by draining, digging and dredging? Tidal pools are rich in sea life and an important part of the ecosystem at the shoreline. By damaging the area you run a real risk of causing permanent damage that could have much farther reaching effects. My wife is finishing her studies as a marine biologist and did a research dissertation on tidal pool effects; I was amazed at how fragile an ecosystem it is.

K, 'nuff of the crunchy lecture. Just out of curiosity, what are you hoping to find?

 

[nashwen]

Not much marine life in this particular pool its caught by a large swell that keeps it free of seaweed etc, but I agree the ecosystem is an important issue.
The pools has been used as a swim/dive pool for many years, theres also been many ship wrecks in the small bay over the years (the swell naturally collects things at this end of the bay) and a lot of activity in the area during the bronze age. My thinking is anything heavy over the last 4000 years that has survived will still be there in the sediment/gravel.
The venturi system sounds good, whats the maximum lift on this sort of thing? could it be powered by a 3" pump 1200 litres a minute?

 

[KevGA]

Sounds like a great spot, definately the best of both worlds. Good luck and keep us posted!

 

[nashwen]

Think I'll have to look for a larger pump then, a lot of gravel (several ton) needs to be sucked straight through and sorted/screened above water level if this is reasonably feasible. I'll try and post a pic of the pool etc to give full impression of scale.

 

[gsmeiers]

nashwen,

Do you have any update to this story? Did you find anything?

Garrett

 

[nashwen]

Hi Garrett
Thanks for the interest no news yet though. In the process of making a Venturi suction pump. Will have to suck several cubic meters of sand gravel and stones up about 25ft to water level and then a further 2-3ft to sort it. Any other ideas would be appreciated.

How do set a picture on this forum, I can give a better example of the problem then.

thanks

Nashwen

 

[Floater]

Nashwen the easiist way to post a picture is to get the photo and save it ot your desktop under whatever name you want in the JPG format. It must be less than 128 KB. Then when you post just scroll to the bottom of where you are typing and hit the browse button. Then chose your desktop from the list then choose the file you saved and hit the open button. Done. then hit post and it will appear. Sounds like a great project. You are going to need a site about 10 meters x 10 metes to pump all this sediment to just to get it out. Are you going to check it with a metal detector or are you trying to visually classify and sift for the items? What type of items do you think are in there.?

 

[nashwen]

Hi Floater
How would I reduce the picture to 128KB ?

I plan to suck up the gravel and sand etc at high tide and grade at the side of a boat through a mesh retaining anything the size of a ring or larger. I'd also get a 2nd chance to scan everything with a detector at low tide.

 

[Floater]

So you have about four hours each time to dig sift and scan. HMMM sounds ambitious. Not sure what program you use to bring up the photos on your computer but if you have photo shop bring up the picture. then at the top go to Image click and then click image size. Thenreduce the photo to about 6 inches x 7 inches and that should put it in to about the right range for uploading. Before you do any of this just right click on the photo and click properties to see what the file size is to start with. The reduction is exponential so it doesn't mean you have to reduce the image in half if its a large file. . Let me know what program you have. Or you can do the same thing in paint just a little different procedure. Paint is on all computers with a windows operating system.HH Hey what country are you in?

 

[Floater]

Sorry I miss read about the low tide. I see what you mean. At low tide you will be able to scan the pool itself. Im a little slow sometimes. LOL

 

[nashwen]

can't seem to get these damn photo's downloaded ! Any way I don't intend digging, shifting and scanning, I hope to (this is where I'm looking for advice) use some kind of a suction pump to suck up all the gravel, is this feasible with a venturi type suction pump, then on the surface I have a large grader fitted to my boat which will sieve the gravel and sand keeping back any thing the size of a ring or larger.
As for finds, don't want to give too much away on the net but basically it's as per my 2nd post.
At the moment I'm sorting out the piping etc for a venturi type lift, just hope this will move the amounts I'm thinking of.
Will post pictures when I'm able.