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kaveman
20:56:17 Tue
Feb 10 2009

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Dredging w/Hydraulic Excavator

This was prompted by an earlier thread that was getting a little off-topic. Give me half an hour or so to upload all the story.

Anyway, purely theoretical at this point, but I felt like doodling with the computer a little today, so here goes,....

First, we clear the vegetation from the area we want to mine.



The mining plan is to dig a series of ponds that we can dredge outside of the active waterway. We start by removing the top layer of material from the holes, flooding the holes, and using a suction dredge to mine the lower layer of gravel and clean bedrock.
[8 edits; Last edit by kaveman at 21:59:18 Tue Feb 10 2009]

  
kaveman
20:58:44 Tue
Feb 10 2009

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Re: Dredging w/Hydraulic Excavator

We bring in the excavator and starting from south to north, we dig a series of shallow ponds 15' wide by 30' long, leaving narrow dikes between the ponds. We backcast the spoil behind the excavator and leave that material for later processing.



Working south, we extend the ponds to full width of 30'x30' and continue to backcast the excavated material.



Then we shut the excavator down and pump water into the holes to create the dredging ponds,..........and bring in the dredge. The dredge is floated in the center pond and the hoses(in this case a twin 6")are crossed over the dike into the south pond. The idea here is to keep the water in the south pond clear enough for dredging while the muddy tailing water dumps into the center pond and filters back through the dike.

[3 edits; Last edit by kaveman at 21:33:36 Tue Feb 10 2009]

  
kaveman
21:11:29 Tue
Feb 10 2009

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Re: Dredging w/Hydraulic Excavator

Once the south pond is dredged of all material and the bedrock cracks cleaned of any gold, the dredge is swapped around to the south pond and the hoses go into the center pond. The dredge tailings from the south pond are the first to go, then the bottom material from the center pond and the cleaning of the bedrock.



Once the center pond is completely dredged, the nozzles can take down the dike between the ponds and clean the bedrock under it.



Then the dredge is moved forward again and the hoses dropped into the north pond where the process repeats.



Eventually we end up with a 30'x90' pond with clean bedrock and nothing but dredge tailings in it. Time to remove the dredge and bring in the gravel plant to run the spoil pile and backfill the hole.


[3 edits; Last edit by kaveman at 21:43:57 Tue Feb 10 2009]

  
kaveman
21:22:29 Tue
Feb 10 2009

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Re: Dredging w/Hydraulic Excavator

Now it's just a matter of walking the excavator and gravel plant up along the pond as we feed the gravel in and discharge oversize and tailings into the pond.






Once all the material has been processed, we bring in the dozer to grade the tails and prepare the ground for replanting. The process can continue in another location or ponds can be added to the chain.

[1 edits; Last edit by kaveman at 21:50:01 Tue Feb 10 2009]

  
Walt_Anchorage
22:35:33 Tue
Feb 10 2009

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Re: Dredging w/Hydraulic Excavator

Seems like a good idea but I have a couple questions. First, after you finish dredging the south pond and move the suction hoses to the middle pond arenít you going to be reprocessing the same material you just took out of the south pond (or did I miss a step)? Second is will the water filter through the dike fast enough to replenish the water your dredge will be rremoving?



---
MY Web Sites:
rubyalaska.info
alaskagoldrush.info
swiftcreekmine.com
 
 
kaveman
23:02:21 Tue
Feb 10 2009

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Re: Dredging w/Hydraulic Excavator

Quote: Walt_Anchorage at 22:35:33 Tue Feb 10 2009

Seems like a good idea but I have a couple questions. First, after you finish dredging the south pond and move the suction hoses to the middle pond arenít you going to be reprocessing the same material you just took out of the south pond (or did I miss a step)? Second is will the water filter through the dike fast enough to replenish the water your dredge will be rremoving?


Exactly right,..........we will need to reprocess the tailings from the south hole in order to clear them from the center hole. My experience with dredging tailings is that they go through the dredge at a pretty good rate since they're loose and there are no oversize rocks to contend with. It takes about 1/10 the time to move the material the second time, so it's work we'll just plan to do. I've got a lot of experience dredging my own tailings,................I always seem to put them in the wrong place.

I'm expecting Dredger to post some info on filters for the dikes, but my guess is that either it'll soak through quickly enough to not overtop the ponds(unlikely), or I'll take a bite out of the dike with the hoe and replace it with loose gravel(most likely because I want the dredge hose going through the dike rather than over it), or, possibly we'll keep a steady flow of fresh water coming into the dredge pond to make up for the unavoidable seepage to the rest of the bar. We've got a 15HP pump supplying a 3" hose at 4-500gpm for intial filling of the ponds, assuming groundwater won't be enough in any particular area.

Yes, good questions. We've been thinking about both of them. Now that Dredger tells me that the dredge pond will remain clear enough to dredge, I'm wondering what it's going to be like when we start dredging the center pond(which acted as a tailing pond for the south pond). Will a day or two of settling be enough, and will we need to worry about kicking the silt back up? If nothing else, we may just have to dredge blind until we get the tailings crossed back over to the south pond. Poor visibility isn't that much of a concern while moving tailings, but it becomes a major concern when moving boulders and cobbles and cleaning bedrock. Hopefully we'll be back in clean water by that time.

  
kaveman
23:11:13 Tue
Feb 10 2009

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Re: Dredging w/Hydraulic Excavator

geowizard,...............I refer to it as 'dredging' because we'll be in full dive gear and we'll be operating a suction dredge, but you're right,.............it really isn't dredging. It certainly won't require a dredge permit, since dredging can only be done in the active waterway and obviously the excavator has no business being there! Underwater highbanking, maybe? It's really just an elaborate, mechanized version of suction high banking.

Our goal is to get a fairly large bulk sample from ground 5-10' deep where the majority of the gold is expected to be on or 'in' the bedrock.

The little dance posted above is my idea of how to get the material dug, piled, dredged, processed and returned with the absolute minimum of handling and machinery movement, taking into account the reach of the hoe and considering that the processing plant needs to be tethered to the river by that 3" line. Whether it'll go as smoothly as I plan I have my doubts, but at least I tried.
[2 edits; Last edit by kaveman at 02:28:16 Wed Feb 11 2009]

  
pitchak
02:06:00 Wed
Feb 11 2009

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Re: Dredging w/Hydraulic Excavator

Been doing that for a couple years now.The top material goes through my big high-banker fed by the mini-excavator.The bedrock we flood by diverting what we need from the creek and clean the bedrock.The bedrock is mostly broken up already by the teeth of the mini.Kinda slow going with a 3 inch dredge,but we get all the gold.We recover lots of nuggets in an area not known for nuggets.Up to 3/4 oz. nuggets.And it's all still considered recreational by DNR.

  
Heavens_Pavement
06:36:31 Wed
Feb 11 2009

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Re: Dredging w/Hydraulic Excavator

@ pitchak what permits did need?
got any pictures of your setup?, sounds cool :smile:

  
pitchak
22:40:58 Wed
Feb 11 2009

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Re: Dredging w/Hydraulic Excavator

Sorry,I don't have pictures.
It's a long story about the permits.I have to get ALL the permits known to man.NOT for the mining,but to keep a shed and outhouse that were on the claims when we got them.LOL.
What I do with my tailings is scoop them out of my way with the ex.My ops too small to handle them again.Water leaves plant and goes thru 500 ft of old tailings with no sediment ever reaching creek.DEC and EPA are happy with how I do things.The Grayling are safe in Deadwood.I could use a bigger dredge,but that would mean more gold,more money,which would mean I would have to get ANOTHER permit to spend it all.

  
vortxrex
00:18:52 Thu
Feb 12 2009

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Re: Dredging w/Hydraulic Excavator

Hello all, Great posting on getting the dredge out into the gravel :smile: Kaveman, how good are you at dredging w/ zero visibility? I know you have all your tailings dumping into another pond (like Dredger showed in an earlier post), BUT you are still going to have some serious visibility problems in the forward hole where you are working IMO.

How much oversize material is there? if you can get a large enough through the nozzle it will be workable, but if there is a lot of oversize it will make 'dredging blind' a challenge.

Trev Alty from NZ had some type of mesh net that he was using to control silt in stagnant water... That might be something to look at?

I like what you & dredger are up to & wish you both the best of luck w/ your operations, but In my experience the Hydraulic Elevator type set-ups have a lot more advantages.

Dave Frank


  
dredger
01:07:04 Thu
Feb 12 2009

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Re: Dredging w/Hydraulic Excavator

Hey kaveman,

Looks great mate, I have a diagrams started but your pics are great,

I am in a hurry so some points of my interest, are,

I plan my sites so that I only disturb one small area at a time, not the hole or large area, I also make it clear to the Authorities in my planning applications that if anything goes wrong, only a ""very small "" area is at little or NO risk, and I also ask for and " get " large reduction in Rehab Bonds, also get gold in ya pocket quicker, also i suggest it is easier on your body if you can be digging for short periods and dredging for short periods, rather then having to dredging continuously long periods,do a hole or area in a few days,

Also, when ever the inspector arrives, I point out the rehab areas, in different stages/time periods of rehab, and stress there is minimum envo FOOT PRINT,

Also you mention a gravel processing unit, for the old tailing's, arrrr, where do I start , ok, as you know this or most gravel processing units / trammels or vibrating screens sluices ect ( and even a good dredge ) cost money to first " have" and two "run" , and process "slowly " , so , I suggest using " only the excavator " , and small water filled holes on bedrock level, to concentrate the heavies from the larger tailing's piles in the bottom of a dredge hole, sort of move the dredge hole to the best source of material, or at least easy reach of the excavator, then use the dredge to process the concentrated heavies in the hole at bedrock level , ??. 2 x 6" nozzle, would work /process well, and the excavator could even remove the tailing's from behind the dredge as the divers dredge,

The reason for suggesting this is it was my experience when digging a dredge and tailing's pond was that I consciously tried to shack or drop the or all gold through the overburden and on to the bedrock, testing the material from the work hole was easily done by allowing lots of people over the years to process /pan/sluice as much as they liked, :confused:, they never found gold in the wormhole overburden , only in the tailing's dam over burden or dam walls,

Another experience of mine was inspecting the first skid mounted tromel in NZ , processing bench placer, there was a problem with silted water escaping from dams on a hill into a creek, 1/2 a mile ( very silty material compared to Auss rivers, ), the prob was solved with more dams which slowed the flow, with that in mind I note that the dirt in your pic is much browner or darker in colour, I am not sure what the above means but it is stuck in my mind, because it will effect " the filterability " of the materials used in the dam/ filter wall, I think the "washed tailings overburben " could be more suitable for dam / filter walls,

:confused:, if you can follow that, haha.

Anyway , that was witten yesterday, and not posted, so I will post it and start another,


  
kaveman
02:23:36 Thu
Feb 12 2009

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Re: Dredging w/Hydraulic Excavator

First thing,...........my ground is going to be fairly clean wash with sand and gravel and lots of large rocks. I expect boulders of several feet diameter to be fairly common. I'm going to take out as much as I can with the hoe and just leave the packed bedrock valleys for the dredge, but my bedrock is highly convoluted and there will be lots of places I can't get into with a 42" bucket. There are boulders in the area approaching car-size and I'm sure we'll see a few. We may have to settle for just rolling them out of the way. I don't mind dredging without visibility, but previous work in this area showed that a large amount of gold was deep down in the bedrock cracks and we'll need to see in order to work the cracks. Here's a pic of the blown bedrock at the river's edge. I expect that the bedrock under the bar will look about the same.



I don't know that the hydraulic elevator will work for us. It's going to be suction nozzles, blaster hoses, air chisels and prybars. Years ago a friend dredged this area and got great gold. He mentioned that he'd done his best blasting with a 2" firehose and cleaning a long bedrock crack with his 8" dredge. He figured he'd done about all he could do, but we'd been working a little harder and getting good gold out of cracks with an air chisel, so he tried the chisel on the 'cleaned' crack the next day. He pulled five more ounces out that day, and never used the dredge other than for diving/chisel air and sucking up the chips. There's no way to really clean these cracks without working underwater.

dredger,.................the nice dark dirt in the background pic used in the diagrams posted above probably doesn't have much gold in it. That pic is from Central Park in New York City. :devil:

I didn't do that to try and fool anyone,.............I was just trying to find an aerial view that I could use as an example that had pretty good resolution, and I figured Central Park probably had the best Google Earth coverage. Central Park was nothing but full tree coverage and baseball diamonds, but I found this one little corner where they'd obviously been tearing up, so that's the spot I used for background. Here's an shot of my actual sticks and stones,......



We're going to keep the site as clean and tidy as we can, but I can't think of a way to get anything done without at least two holes, and three works much better. The gravel plant is already onsite and should be able to handle 20yd/hr+/-. That'll work out to a long three days to run all the material removed from the three holes, depending on exactly how deep we are to bedrock. I'm guessing we'll dig a day or two, dredge for 2-3 days, and process gravel for another three. I think the digging, dredging, and processing will need to be done in separate stages rather than all mixed up. If I have to get into the dive gear, I'd just as soon stay in the dive gear until all the underwater work is done.

I agree that the washed tailing would make the best filter, but I don't think we'll have any washed tailings to work with until after the dredging has started. I will have the hoe sitting there for tailing removal/dam building if it becomes necessary.

I may have posted this one before. It's the only pic I've got of the hoe with some real material in it,..........digging a test hole last year just to feed our curiosity. All we did with that gravel was pan a bit before dragging it back into the pit. Really wet in the spring when this pic was taken. Bone dry later in the summer.



[1 edits; Last edit by kaveman at 02:28:07 Thu Feb 12 2009]

  
keninla
03:57:28 Thu
Feb 12 2009

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Re: Dredging w/Hydraulic Excavator

Kaveman,

It looks to me like dredging will be kind of slow going with all that oversize that you will have to move. ???

If the bedrock is so uneven then I would think that many boulders would be in places that are not easily reached by the excavator.

also, If I remember correctly you are on the Klamath river - right??

Ken

  
dredger
04:45:28 Thu
Feb 12 2009

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Re: Dredging w/Hydraulic Excavator

Hey vortex,

mate, thanks for the good wishes, I have always admired your great stuff, I only wish you would get yourself one of these,:smile:.
,

Save ya back heaps, :devil: Ps, actually i wish everyone with a dredge would get one, :devil:

Hey kaveman,

First , I have a few drawings partly done, ( but I am not happy with them,:confused: , plus i like your pics, plus I have a few things on my mind, and of course not much time, plus I will do a drawing to hopefully explain a concept in concentrating the cons previously mentioned,

I have read today's great posts,

The Grayling are safe in Deadwood. DEC and EPA are happy with how I do things.

I agree with pitchak, 1990 ----, I found the Authorities did not have any problem if the work is carry out " out of the river flow ", which has " no "effect on living things in the river, fish/ micro bacteria /fungi ect,

"I'm expecting Dredger to post some info on filters for the dikes",

Ok, just had an idea on showing /hopefully explaining points of interest ,


1. is the clean water inlet to the hole, I usually start the inlet trench about 6' from the flowing river, then I dig the work hole and tailing's trench ect , then I will build a rock wall " dam "by hand and lay canvas strip to stop most water flow, this backs up and quickly water starts to flow into the inlet trench, I can quickly adjust the water flow into the work hole,
2. is the flowing water entering the hole so as to cause a "swirling action in the hole",
3. is the normal dredging water height,
4. is the normal tailing's dam water height , which also means the tail of the sluices is about 2-3" under water level,
( judging by the shadow it is after lunch and I still had to adjust the flow gate in the river dam, ).and looking at the sluice water height I guess the pumps are warming up , and I am taking the pic), If at any time like every 2-3 days the tailing's dam water level was getting "clogged up " i would idle the dredge , and move the excavator, and "sweep the insides of the tailing's dam/ filter walls, NOT INSIDE THE TRENCH, JUST THE WALLS ABOVE GRAVEL LEVEL, ( couple of feet deep in water,dam walls about 3' high, because all the filtering is done " through the walls" ,
5. is both sides of the sluice header box which are usually over flowing or dribbling water from the work hole into the tailing's dam,
6, is one of 2 Honda 13"s
7, is 2 of the 2 , 4' long stainless foot valves,
8. is opps, the direct of the
outlet of the work hole, ( not really much water exits the hole when the dredge in full run mode, basically the water river water enters the trench, along the trench, and up the nozzle, and that is super clear water,
9. is a green shade cloth to divert floating grass ect off the foot valve area, ( works very well , the dirty water has no real wear characteristics, )
10. is where the work hole dribbles , if it starts to over flow I either adjust the gate in the river dam, or place rocks and strips of canvas and raise the water in the work hole,and stop any over flow, ( the old guy was complaining about his boots getting muddy, )

Please note, it was my intention, fact is , it is my intention to dredge the the tailing's or silt trench next, ( cause I only got half the gold on that bend that time ),

Ok another pic, back asap, dredger,

  
dredger
07:07:17 Thu
Feb 12 2009

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hey kaveman,

mate, I was wondering why I was getting a wiff of red socks in Alaska brown dirt,, haha, ( joke),

That's my kinda river gravels, excellent, I hope there is good fall in the river gravels and the bedrock over the length of the ( I suggest ) two holes, perhaps 70-80 feet, in length x say 30 feet wide at the work hole, and x 10 feet for the disturbance from the silt trench and dam/filter walls, do keep the site as small as poss, and I always try to return or rehab to original contours, Actually almost picture perfect contours, but I don't have old large tailing's mounds to process either,

As to the rock bed, I would be like a pig in mud, I would first build pad to work from, then I would slip off my bucket, and on with my ripper tyne, and have a little nudge around the crevices, while pushing the larger rocks to the perimeter of the site, bring a pump and hose to wash the rock and stack them as dam walls around the perimeter of the proposed site, and fill that with water from your auzillary motor/pump, small dredge, and small hydraulic jack hammers running off the excavator, :smile:,

Sorry gotta run, I will the other pics asap, back asap,

  
kaveman
03:36:07 Fri
Feb 13 2009

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Re: Dredging w/Hydraulic Excavator

Yes, that's right, we're on the Klamath. I do expect that there will be plenty of large rocks jammed into the bedrock valleys. It won't be much different than standard river mining except that we'll have the excavator standing by for any heavy lifting and the top several feet of overburden will be gone.. Gotta be easier than winching! Wish I had a ripper, but this year we'll have to get along without it.

Dredger, I'd love to see all the pics you can dig up. We won't have a natural flow of water from the river to fill the holes, but I've got plenty of pump to get it done. Suspect we'll be pumping every morning to refill what seeps out during the night(at least in the spot we intend to start). Up against the hillside(away from the river)we'll have plenty of natural seepage at least in the early part of the season, but that'll wait until next year at the earliest.
[1 edits; Last edit by kaveman at 04:34:49 Fri Feb 13 2009]

  
dredger
03:57:03 Fri
Feb 13 2009

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Re: Dredging w/Hydraulic Excavator

ok, I spoke to a good friend a while ago, who told me about using high pressure cleaners on above type bedrock, i said i would think of a idea and post it, and the idea came last night , ( better late then never, ).

Petrol powered Hy pressure water blaster, and wet dry petrol powered cyclonic type vacuum gravel recovererr.
------------------------------
Very good suction, even a 8 hp 2" suction hose would be very effective, please consider how often you get a blockage in the vacuum cleaner. :devil:,

Next is high view of the work hole,,
-----------------------------
Sorry this pic was to small to add no's,

Next is another view of the dredge running, please note the tailing's hole and work-hole are full, which is the normal operating water height, please note ,the old guy is still standing there, ( bless his cotton socks, ),

testing back with one more, asap.

  
dredger
04:29:34 Fri
Feb 13 2009

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Re: Dredging w/Hydraulic Excavator

Ps, some comment on the pic taken high above the site,

The blackened tree ( right bottom corner of pic ), shows a lightening strike, at which time there was a diver in the water, he stated he was "knocked out " for a short time, but continued dredging,

Hose /sluice motors are clearly visible, A marks or shows inlet trench to hole, B is overflow from hole, please note , just left of C , ( out of the pic, ) there is a large tree on river bed, just this side of the pumps, please note for later reference,,

The 6' x 4' trailer, with a blue drum, carries the engine and pump frame, and the bluy green canvas box is the trailer cover,

Other yellow trailer is for the sluice, both trailers are loaded/ using the excavator as a crane, all machinery can be removed from site in 12 minutes, in times of flash flooding,

Far side of the hose is shallow bed rock , about 4 ' deep overburden, this side of the hose , show a deep gully cut deep into bedrock bottom, 15-20' deep, ( running length ways), ,

  
dredger
23:30:31 Fri
Feb 13 2009

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Re: Dredging w/Hydraulic Excavator

hey kaveman,

"""""""""Dredger, I'd love to see all the pics you can dig up. We won't have a natural flow of water from the river to fill the holes, but I've got plenty of pump to get it done. Suspect we'll be pumping every morning to refill what seeps out during the night(at least in the spot we intend to start). Up against the hillside(away from the river)we'll have plenty of natural seepage at least in the early part of the season, but that'll wait until next year at the earliest.
I have a few more pics, perhaps we should start another thread before these pics get hard to load, ??. dredging wHydraulic Excavator ,PART 2. ????>
nice info in ya post mate, ( AND A GREAT PIC OF YA EXCAVATOR TOO, yAHOO.I hope we see a few dredge/ excavator operations open up on the Klamath, slope/ angle bedrock/ hillside is good, I would also suggest there is "perhaps" a way you might only have to pump say three work holes of water across and up to where you actually want to work, then because you filter that water so well you could recycle the water from canvas lined clean water holding dams ?? level / below /above with your work hole, ??. I would also go further and suggest, it is possible that a dirty water ( not including overburden/gravel / rocks from the sluice, just fresh dirty water, ),, dam wall/filter could be constructed in front or up-hill of the work dredge hole, no worries, and have as little sepage as poss, ???>
This next pic, is really the heart of the filtration dam /filter /wall concept, , i was just getting ready to back fill the tailing dam when I remember to take pics,
,
testing, back asap.


  
dredger
00:45:39 Sat
Feb 14 2009

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Re: Dredging w/Hydraulic Excavator

ok, to let you see how far or long the tailing /filtration wall is please note in this pic,
1, is the motors and pumps,
2, is the foot valve sun-shade green cloth,
4, is where I had already started to drag the wall back into the trench, back filling, I only managed a few yds before I realized i needed to take pics, you can see the shallow trench about a yd deep x a yd wide, just enough material from the trench to pile up the filtration wall,
6, and 8, Please note, all the way along the grassy bank at the waters edge the vegetation is super clean, no sign of built up silt caused by dirty water escaping though the filter wall , also please note, that from what I saw , "most if not all dirty water " was filtered through the lower 1-1 1/2 feet of the dam wall,and flows out of the wall and back into the river flow,super clean that flowing clean water is about 3-4" deep, full length of the wall to the river flow, basically I would suggest the heavier silt materials leaving the sluice stayed and moved along in the lower depths of trench, this of course would block or clog water trying to filter though the " trench"" sides " , only through the upper dam/filter walls,
7, is a silt "plume " (moving down the flow )caused " ( by me stirring some mud well above the site with a shovel,) this is done to show the yellow ( light brown dirty water moving down stream and to compare with no3 area,
3, is the strip of water along the vegetation, 3-4' , please note this strip or area is also as clean as, no silty yellow residue left on the rocks,
5, is the tree I mention is previous post,
2 , is the river rock wall dam built to back the flow up, which supplied water to inlet trench, built by hand, easy,

I have a few more pics and suggestions on rehab, and the benefits in keeping the area of disturbance to a minimum, this is a very good thing, environmentally speaking, No EIS, required, and only minimum enviro BONDS,

sorry gotta run,back asap. dredger,

  
dredger
01:38:30 Tue
Feb 17 2009

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Re: Dredging w/Hydraulic Excavator

hey kaveman,

Sorry been bussy as, and computer probs, too, still too slow, ( like me ) ,I will start a new thread, for more pics, asap.

  
kaveman
04:32:11 Mon
Dec 14 2009

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Re: Dredging w/Hydraulic Excavator

vortxrex makes mention of a fabric curtain used by TrevNZ. I rmember seeing the picture Trev posted, but evidently I didn't save it and can't find it with a search. Any chance anyone has the pic saved? I think the curtain might be an all around better deal than leaving dikes beween the ponds.

Jim, if you could work your search magic, I'm pretty sure it was posted in one of Trev's suitcase dredge threads.

  
Greg_in_BC
17:23:40 Mon
Dec 14 2009

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Re: Dredging w/Hydraulic Excavator

Love the discussion gents!

The material that I remember Trev referring to is the ground fabric used for landscaping. Has small holes in it so the water can get through but is slowed down. I think a couple curtains would slow things down a lot as the water flow/pressure between them would be reduced.

Might need to use a pressure wand now and then to wash the slime off the upstream side and open up the pores again.
[2 edits; Last edit by Greg_in_BC at 17:26:19 Mon Dec 14 2009]

  
dredger
01:25:38 Fri
Dec 18 2009

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Re: Dredging w/Hydraulic Excavator

Love the discussion gents!
Me too. but my computer is stuffed , I plan a new one and camera asap, too bussy with immediate project,
Merry Christmas and Happy New Year to all..

More blar blar, for the new guys, http://bb.bbboy.net/alaskagoldforum-viewthread?forum=2&thread=506&postnum=60.

back asap, dredger.
[1 edits; Last edit by dredger at 02:05:49 Fri Dec 18 2009]

  
kaveman
04:26:27 Fri
Dec 18 2009

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Re: Dredging w/Hydraulic Excavator

In case anyone's interested, I went with a two pronged approach on the fabric silt dam,...........

Primary fabric is going to be a woven poly tarp. Two 20'x20' tarps are on the way. Basically going to weight the bottom grommets and throw them over a line and tie them in with zip ties. Should give me a double thickness of about 70% shade and make a wall 40' long by 10' high. You can probably see the tarps her, at least for awhile,.......
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330348961469&ssPageName=STRK:MEWNX:IT

The weed control fabric looked a little frail for continuous use(actually, it looked a lot frail), but would probably be a better bet for a single and simple setup in a dredging operation. Cheaper and easier to handle(maybe?). Problem is the sizes available. I bought this roll for backup to the tarps,........
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330383086085&ssPageName=STRK:MEWNX:IT
If need be, I will stitch it in between the double layer of poly and get near 100% filtration. It'll be more cumbersome to store and handle, but it should get strength and protection from the poly tarp. I don't expect I'll need it, but I'll have it available if I do. I'll use it for weed control around the trees I plant for reclamation if nothing else.

This was the only roll I could find at 4' width. Most everything else is 3' and more lightly built. 12.5' rolls are available on ebay, but were around 450' long and $450,....................way more than needed. I almost went with this stuff which is probably perfect, but the tarps doubled my layers and were just a bit cheaper and had the advantage of easy setup being simply draped over a line,...................
http://www.growerssupply.com/farm/supplies/prod1;gs1_shade_houses_shade_cloth-gs1_sunblocker_bulk_shade_cloth_1;pg107761.html

I've used this shadecloth in 80% for canopy over the dredge, and it's the same stuff they use for tarping over loaded trucks. Very tough and it doesn't unravel.

More I think about it, the more I like getting away from the dikes and just using the silt curtain,............assuming it works! Can't see how the dikes could be less than ten feet thick without posing a collapse hazzard and sooner or later they'd need to be removed and dredged to clean the bedrock below and that process would be silted out for sure. At least the curtain doesn't cover any ground and can be easily moved from place to place. Hopefully.

  
Greg_in_BC
16:12:33 Fri
Dec 18 2009

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Re: Dredging w/Hydraulic Excavator

Kaveman, there is a more commercial material that is used for road construction etc up here - especially on soft ground to keep the road bed stable. It is like the lightweight landscape fabric but much heavier and can be found in very large rolls and sizes.

It is referred to generally as geotech fabric and there are many varieties. Check out a simple search Geotech fabric and you migt find something in your area.

It is also used by enviro guys for slope stability control, and drainage control to keep from scouring areas and slow the flow.

If you contact some road builder or construction they may have some end pieces to get rid of?

Good luck in your search and looking forward to see your operation progress.

I like the idea of working the hole forward and using the curtains. As you say the other way you would have to come back and work the dikes left behind (plus some of the tails (how long for them to stabilize?) to get the remainder of the bedrock.

Added: just noticed that this company list the water flow through rate in GPM/ sq ft. and they actually list a
turbidity/silt curtain

You might be on the right track with different permeability levels as you go from the high solids content side to the working side. Larger to smaller. Kind of like a screen plant works better if you screen down progressively. Each curtain will have less solids to deal with and less water pressure flow through. Might have to brush them off or water wand them off now and then to open the pores again.
[4 edits; Last edit by Greg_in_BC at 16:45:51 Fri Dec 18 2009]

  
kaveman
17:12:35 Fri
Dec 18 2009

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Re: Dredging w/Hydraulic Excavator

Thanks for the links Greg. I found the silt fence on ebay, but all rolls were either 2' or 3' max height. I'll bet the 12.5' roll I found was for roadbed, but that was the roll that came in a 450' length. I think it came up in a search for landscape fabric. I'd have been happy to pay $1/ft for the 30-40' I think I might need, but 450' was a little too much. Coulda still put it down under the gravel in the drive that I'll probably be trucking in next spring tho,................

That stuff shows a flow rate of roughly 4gal/min/sq', and the tarps I'm using if anything will be more porous, so my curtain should start off well over 1200gpm. That's not counting any of the natural seepage coming in from the sides. Probably will have to de-slime the thing from time to time, but I think it's all a'gonna work.

The dredge will likely be discharging tails away from the curtain, so all it should have to deal with is the suspended silt. I'm used to dredging in the Klamath, which might have 10' visibility on a good day. I won't be surprised if the ponds run better than that.


  
Greg_in_BC
04:57:26 Sat
Dec 19 2009

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Re: Dredging w/Hydraulic Excavator

Kaveman, I wonder if you will need to have the entire curtain area to allow flow through water. You may have enough flow back by only allowing a smaller portion to flow back. That would allow the water to settle more in the rest of the pond area.

You could even have the exposed flow through areas offset from each other (separate the curtains with a foot or so to allow settling as well?) so the water has to move back and forth or ??

Lots of options for experimenting with, will definitely be interested to see what works and adjust for best results.

I know what you mean about the Klamath, we had near zero vis with a current sand storm in 40' of water in '90. Tough working. Dredging by brail and constantly checking for 'hangers'.
[1 edits; Last edit by Greg_in_BC at 04:58:19 Sat Dec 19 2009]

  
cash2u
20:40:30 Sat
Dec 19 2009

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Re: Dredging w/Hydraulic Excavator

You might consider what we do: get or build an oversize bucket and cut holes in it just smaller than the suction nozzle on your dredge. Only dig what you cannot use. the fewer times you handle the material the more you make. To get started you really do not need to see to dredge what is left. We use bails of straw to clean the water when necessary.

  

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