I'd like to set up a system that uses rain to clean up gravel on our property. We have a few areas with gravel (pink shale as it's called around here) seams that are about half gravel, half silty soil.

I can use the gravel for road repair, paths, foundation trenches, etc... so I'd be happy with as much as can be cleaned. Not all the uses require clean gravel, but I can use the soil to improve grow beds, too.

My initial thoughts are along the lines of tarps on an incline to let the rain wash gravel/soil that is shoveled on to it. A basin could be formed at the bottom to catch the washed soil.

I don't think the tarp would hold up well when used this way though. Maybe some old corrugated roofing panels?

Any thoughts on a better way to design a system that would last for many years would be appreciated.

I don't see how a trap would be tough enough.... but

How about a trough much like you would see old gold miners using - called a recirculating sluice?
It does use running water, but if you would design your system to capture and reuse the same water it would work really well.

The general idea is to have a screen tray with holes just smaller than your gravel but larger than everything else. A large container or tub under it to catch your water/mud. Allow this water/mud to settle and you can suck off the water using a small cheap pond pump into another holding tub, tank or barrel. At this point you would have clean gravel on your tray, reusable water pulled off, and wet silty soil in the bottom of your tub ready to be scooped out. Of course this basic idea can be refined even more, and most of the parts can be from other re-cycled materials.

With this set up you can clean as much gravel as you need and recover both the water and soil for secondary uses.

Think mining for gold

Hope this helps

I know having it on corrugated roofing at an incline does not work. I had some pea gravel on top of galvanized corrugated roofing for almost 2 years at a decent incline, but 2 inches down was silty dirty gravel when I went to move it. My best off-hand thought for cleaning would be a rotating tube of screen that would turn with a motor--you could use a hose or just let it rain to rinse it, but it would be a batch at a time, maybe one tractor bucket full?

Thanks Jami - I like the recirculating sluice approach. If we end up needing to use power to pump water, I will probably go with this approach. I've seen some interesting videos of folks using a similar recirculating setup to drill shallow wells with a hose and drill bit attachment.

Thanks Gary - we have a hand-powered rotary sifter that my son made last year. It works pretty well for sifting gravel to separate the soil when the material is fairly dry, otherwise it keeps a lot of our clay-based soil attached to the gravel. Maybe my son will finish the pedal-power adapter for it this year
Here is a link with pictures of the project:
http://wellheeledhills.wordpress.com/2011/03/23/rotary-sifter/

It's too bad the corrugated roofing didn't work out for you... I'm pretty sure I can scrounge up a fair bit of it.

That was an awesome sifter! What size screen did you use to make potting soil with it? Pedal power(or electric for me since I usually work alone) would be a must. Now I must have one--another spring project on the horizon. Even more work to do...but fun. Thanks!

Thanks Gary, I'll pass along the kind words to my son. He's still pretty proud of it

I believe half inch hardware cloth was used for the screening. The pedal power adaptation will be a big help, I'm hoping we get it done this spring, too.

Yea, that is a great sieve - homeschooling is wonderful.

Well done!

This is something I gleaned from one of my posts in green building ------------------ POWER SCREENER------------I've invented a dead simple power screener. I'm sure this has been invented before but it worked so well I'm going to tell you about it anyway.----------- I needed to screen rocks out of some reasonably dry dirt. I had a big screen about 4 ft. in all dimensions. I found that it worked reasonably well when used on a slope with only gravity powering it but I wanted to make it process material quickly and to break up lumps.

I mounted an electric drill to the top of the screen. I used duct tape to attach a bolt to the side of a drill bit so that it was seriously out of balance. With the trigger locked in the "on" position, the drill vibrated wildly and transferred that energy to the screen.

No doubt this is hard on electrical equipment. But there are plenty of old drills and skill saws which have no value. Any of these items may be altered so that they shake a great deal. They could be used for processing earthen plasters, for soil sifting, etc.

Dale Hodgins wrote:This is something I gleaned from one of my posts in green building ------------------ POWER SCREENER------------I've invented a dead simple power screener. I'm sure this has been invented before but it worked so well I'm going to tell you about it anyway.----------- I needed to screen rocks out of some reasonably dry dirt. I had a big screen about 4 ft. in all dimensions. I found that it worked reasonably well when used on a slope with only gravity powering it but I wanted to make it process material quickly and to break up lumps.

I mounted an electric drill to the top of the screen. I used duct tape to attach a bolt to the side of a drill bit so that it was seriously out of balance. With the trigger locked in the "on" position, the drill vibrated wildly and transferred that energy to the screen.

No doubt this is hard on electrical equipment. But there are plenty of old drills and skill saws which have no value. Any of these items may be altered so that they shake a great deal. They could be used for processing earthen plasters, for soil sifting, etc.

We gotta do a project together sometime, Dale. You have a machine for everything.

There are two options for washing gravel that come to mind for me, for non-powered sites especially.

The first is the way a creek bed washes gravel into bars naturally. It does seem to take a lot of water flow. If you want to set up a passive landscape that can do this gradually over years, I've read about discreet gold-mining sluices that were simply made with bars of rock or timber across an existing stream. The water washes the lighter particles away over time, but heavy gold or gravel stays behind. If you don't want to pump water, you can use an existing water element like a roofline or gutterspout; I've noticed that roof driplines often expose gravel by washing away the dirt. To collect the dirt as well, set up a settling pond or pit somewhere downhill.

The second is a method I learned at Cob Cottage Co, which is more portable and works well on sites without power or running water.
Set up a screen at a sharp angle (leaning against a sawhorse e.g.), facing the source of dirt, or downhill if possible. Put a tarp behind/under the screen to collect fines, and one in front to collect gravel. Shovel the pile at the screen, one shovel-ful at a time. All the material should either go through in the instant it lands from being tossed, or shortly thereafter as it slides down the screen. Large stuff bounces or rolls easily off the front. If you get a lot of dirt in with the gravel in front, the angle may be too steep, or your pile is 'full'. I just keep shoveling until the pile underneath reaches the height of the screen; then I have to tip the screen forward and collect the piles, or move the screen to a clear space. It is not necessary to be super-picky about forcing particles through the screen; choose a larger screen size like 1/2 inch, and you will get mostly 1/4"-minus in the sifted stuff, and some of the small stuff in with your gravel but not much.

If it is necessary to break up chunks of clay, they can be soaked in water until soggy. Silty or sandy soils will generally loosen up nicely when dry. Tilling, or harrowing (dragging chains or driving over the material when it is in loose, plowed chunks) will help separate clods in larger quantities.

I suppose you could mechanize it somehow. A rock yard would drop crushed material from a conveyor or something, onto a long tilted screen (or moving screen-belt) raised high enough to allow for a large piles below, with a series of screen sizes to separate different products.
If you don't have a conveyor, you could use those corrugated panels you were excited about to make a slide or chute. I'm imagining a corrugated slope you slowly dump dirt onto from a tractor-bucket uphill, maybe with some bars or teeth to stop big chunks. The pile slides down into a rolling stream of dirt, that is directed toward the tilted screen on the downhill side.

Even a simple process of piling dirt into piles seems to concentrate the big rocks around the edges where they roll off, leaving dirt and little rocks at the top. Anything that gets it moving could work.

Whenever I try separating rocks from the garden, Ernie reminds me that the plants don't care - in fact, they like it fine with their roots in the gravel. But I like the separated gravel for drainage, and the plants don't seem to mind the rock-free soil particularly.

-Erica

Interesting thoughts, I appreciate the ideas. It gets me thinking about ways to use the resources we have to work with.

I've got some height to work with. The gravel seam that i want to use has been bitten in to in the past by heavy equipment, so it is easy to stand up on the upper level and there is ~6-8 feet of drop down to the gravel hill to a flat area.

There is running water down the hill several hundred feet in the form of a seasonal creek, but I don't want to mess with it at all. I also have access to a well and pump from a generator, but I'd rather avoid using power for this task so that it's something that is just powered naturally over the years.

There is seasonal run-off from the county road ditch that borders our property and enters our land via a culvert about 500' from the gravel seam. There is some elevation bumps in between the culvert and the gravel, so it may just be best to use that water in other ways rather than try and pipe it or route it over for this purpose. It is tempting though.

Right now, I am thinking about making a gabion type basket (U-shaped) that butts up against the gravel slope. Maybe about 4' wide and tall and about 8' long. I could rake/shovel/push the dirty gravel in to the basket from above and unload the cleaned gravel from the opposite end. If I prop up the basket using logs/pallets, I can set up a collection system underneath using tarps or a catch for the washed soil.

If the cold season rains don't wash enough of the soil off the gravel (probably not unless we get more really hard storms like these past ones), I am thinking of using some tarps or sheeting to direct some run-off over the top of the basket to amplify the rainfall. Maybe funnel the run-off in to a wide pipe with a cap and holes drilled out for a really big "shower" effect.

More thinking to do...