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Hydraulic Gravel Questions


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I've been visiting some friend's claims which are on rivers where hydraulic mining activity happened in the past, so there are large gravel bars in the canyons left over from the mining activity of 150 years ago. I've got some questions hopefully somebody who understands mining history can answer:

1. The gravel banks are maybe 50 feet high, and when I climb to the top of them and walk toward the point where the edge of the gravel table top meets the hillside, I see hand stacked trenches which are maybe 5 feet deep, 3 feet wide and maybe 100 feet long. All the rocks on the sides of them are hand stacked. The trenches travel parallel to the flow of the river, but up on the top of the gravel bar, and then never end near the water. What are they? Did they somehow divert water (no evidence of a ditch) to try to rework the tailings and only dug down 5 feet and worked backwards as they were washing the gravel? It has me perplexed.

2. On one portion of the river, up on the gravel bank, near the hillside there is a huge pile of water rounded rocks. Not rocks which look like they were pulled from the river as it is too far away from the present river course, but still within the confines of the gravel in the river channel. Also the rocks are huge, maybe 4-8 feet in diameter in a 60 foot high pile. It may look like there might have been some sort of derrick there as it would have been impossible to get some of those big rocks so high without some sort of mechanical device. There is an overgrown depression on the bank side of the river bed, so it may appear that the rocks may have come out of it. I didn't get close enough to determine if there was some sort of trench leaving that location, as I was just walking down the river.

Anybody got any ideas?

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This site has a great .pdf on hydraulic mining from 1942, comes in at 76 pages. Pretty incredible document.

https://docs.google....ulletin_015.pdf

I've also seen a modern, published study of a 19th century hydraulic operation where all the hand-stacked collection channels were mapped and studied in the context of chronology. If I can find the article, I will post.

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Diversion was the game a the day and almost all rivers in kalif,moved,robbed,raped and pillaged as all we get are the crumbs from their plate a plenty --oh to have been born in dayz of old---with todays knowledge-John

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Along side the stream on my claim are pretty large piles of rocks aprox 50' wide, 150' long and about 20 to 30' high. My understanding is that they are from the Chineese miners. They used a derik of sorts to lift the rocks onto the pile. The area they pulled the rocks from is now bedrock covered with about 3' of overburden. I am finding what I call "New Gold" in pockets of the bedrock.

There are also a few diversion channels that they used to divert the water in order to work the bedrock.

I haven't found any evidance of hydrolic mining though.

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I will guess that the scenario you have in no. 1 were exploratory trenches. The may have hauled the dirt down to the river for processing, not uncommon.

In the second secnario that may have been where a tributary of the main ancient waterway and the tributary came together.

Just my two cents, but a few pictures may clear it up....

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I finally got a photograph of the ditches I see on top of the riverside tailing piles. Does anybody have any idea what they were doing with these ditches? They are all sorts of different lengths and about the same width. This ditch is right up against the hilliside on top of a 30 foot tall hydraulic tailing pile on the side of a river.

post-26017-0-50568300-1345525288_thumb.j

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I've seen numerous channels like that in SoCal @ hydraulic operations from the 1860s-mid 1870s. Down here, those hand-built rock walls were for diverting water and/or gravel material to the flumes (sometimes those channels WERE the flumes). Panning material from them resulted in very little micro-gold for me (although who knows how deep is bedrock). An old oven still remains for burning off the mercury from the amalgam. Detected around it but found no gold. An entire mountainside can be covered in these tailings and channels, with 100-150 yr old overgrowth including nice oaks. Lots of trash too.

Have you dug and sampled your channels?

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Mobius- no sampling yet, just curious what they were. They weren't flumes as they only go a short distance. The bedrock at this location could possibly be at the bottom of the trench, as in some cases the bedrock comes up quite a ways up from the creek (I don't remember how deep the bedrock was at this location). What I don't understand is why make the trench so narrow? It is barely wide enough to move around in. Why not throw the rocks quite a ways further out? After all the trench is on top of a 30 foot high gravel bar- so the rocks they would have thrown out would have rolled away from the trench.

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Thats probably their water ditch, since its on the top of the workings. Everything below would have been ground sluiced.

Ususally they brought the water in from upriver and parts of the ditch could have possibly been flumed, so there is not so much evidence left.

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Wes- it isn't a water ditch- it is only 40 feet long. I'm usually pretty good at figuring out old ditches and flumes as there are a lot of them around here. These trenches were somehow used for working the gravel- I just need to figure out what they did. I cannot make sense of why they made such a narrow trench. The bench where the trench is located is gravel and the sides of the ditch are stacked rock, so they obviously did something with the gravel (washed it) and used the left over rocks to stack. I just don't see why they only made a trench 2 feet wide. If I were to go to the trouble, I would make a trench 4 feet wide, so I could move around while I was in it.

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I still think they are exploration trenches. Saw those in Brazil also..... some were only 2' wide and 10' deep. As you know, If you throw rocks all day you get sore arms, but if you pick them out and only move them an arms reach it's much easier. Just my :twocents:

Another possibility was they were used to capture rain water so water was available way above the creek for panning or rocker box ? ? ? ?

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El D....nailed it....here the slaves would dig a trench no more than 2' wide and 10-12 inches deep and they weren't

short runs either....most of these go half or completely circle a mountain....in many areas they built an outlet and

lined it with rocks so they rain water would run to a much larger catch basin down below....

Since Bill Southern didn't sell metal detector to slaves back then, they threw away many gold bearing gravels....

most of the trenches here are clogged with trees and brush also hornets but when I find one clean enough to

work I normally find gold.....

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E.D. - doubt it was a rain ditch as it is only 30 feet away from the river (and maybe 20 feet above it). So it sounds like an exploratory ditch. Anyone have any idea how they mined it? I assume they would shovel down, run the gravel through a sluice and stack the rocks? By virtue that the ditch is 40 or 50 feet long, I would assume that they were finding gold (or maybe they just liked digging long ditches?) I will run a metal detector down the center and maybe dismantle one of the walls and sample the gravel on the bedrock outside of the ditch to see how it looks.

It possibly occurred to me that since the ditch is up against the hillside, perhaps they started with a ditch close to the river and then filled it in with another ditch dug just up the hill, and perhaps what I am seeing is the end result of multitudes of ditches working their way up the hill. In short, perhaps the whole area has been worked and worked again. I'll let you guys know what I find out

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Here's my take on it. They used the short ditches to collect the runoff from water cannons aimed above the ditches. The ditch took some 30-40 feet of runoff, then channeled that into a single drainage. That would have been easier to aim towards multiple long tom sluices then water seeking its own path down the hill. It would include less material from below the ditches. That way you could crudely control how much of the hillside you were working at a given time. If there were a bench deposit above, you could shoot for that and by careful aim of the water cannon and placement of your ditch, you could work a fairly specific layer, and ignore material from low-paying ground.

I suppose you might see areas where more material was taken at some height or layer than from others, presumably from somewhere above the ditches that might help prove my crazy theory.

Or could it be a bunch of individual claims that ran across the creek and up one or both sides of the draw? That's how it was in Deadwood Gulch before all the discovery claims got absorbed into the big operations. Might be everyone had to build a mini-ditch to collect runoff for their own one or two-man operation.

-Ed

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