I have no idea what to call this plan. Hugeltrench, gray water channels, tree water and feed, zai pit worm nest soil improvement system? That's a bit unwieldy to say. My working name for them is mulch drains, although that's inaccurate, they are on contour, not draining.
I'm wondering if I am making any bad mistakes in my plans, before I start moving dirt.
The concept is easy: when terracing my land, I plan to run the ditch witch through the soil, fill the trenches with rocks, then branches and top with any mulch I can get my hands on. That will give the gray water a place to flow deep in the soil for the trees, and stuff to rot to make zai pit type places where worms will be able to live and start working their way further into the dirt, to improve the soil in the area.
The details: The full soil layout is here Gardens In My Mind if anyone wants to look. This picture is an overview of the property plan:
The terraces are only going to be 3-5 foot tall, sloped dirt. There's not a lot of slope, but enough to make the water flow right off and it's difficult to work on the slope with equipment, carts, or my health issues. This pic shows from left to right, terrace, swale, mulch drains, tree roots, terrace, swale.
The fill and probable cut looks like this, with the primary lines (on contour or very lightly sloped) having rocks in them as well as branches and mulch, the 90 degrees off contour secondary lines a bit shallower, and having only the branches and mulch. I'm planning to put the house gray water lines to the rock trenches. The tree roots will get there, and take all the water they want, but I think, considering how it works in nature, that the water will continue to flow through the rocks even after the roots start drinking. Won't be a solid X number of feet per minute flow, more a continual seepage saturation channel through there.
Layout on the land, primary channels in gold, secondary channels in pink. Purple is my paths, blue is water ponding areas, brown lines are terraces/dams.
So, does anyone see any obvious problems with this plan? Other than I need a hell of a lot of mulch fill, branches and rocks, still not sure how I'll manage all of that. The land currently grows 5 foot deep pasture grass, and it makes a LOT of clippings to shove in there. Wood debris is all around here, people dump or burn it all the time, manpower to get it back to my place is the primary problem there.
Hey Pearl, which way does the slope run?
Downward from South to North?
I read somewhere that its best to discharge greywater on the surface, and let the it percolate downward through the soil, you might want to do that before it gets into the ditch, to head off anaerobic conditions.
I've been living with super low tech greywater systems for some 25 years, and am a huge fan of the Oasis Designs website, book, and anything by Art Ludwig. My experience is all with exactly one system so I don't know much about what happens or is needed with other systems.
Here are my random thoughts.
1) Why put stones in the trenches? After a few months they'll be sunk into dense rich, maybe anaerobic ground and won't be doing anything. They'll just be stones embedded in your soil. If you only use wood chips and larger chunks, they'll do whatever it is stones would do, and eventually rot down and contribute to the organic matter, and you can add more wood chunks.
2) In my experience, household greywater doesn't cover a lot of area. A lot of it soaks in right at the point where it hits the ground, and it flows to a distance of 30 feet or more only a couple of times a week at most, when large batches of water come out. So that means I think your map is over-ambitious. Here's what I've been wanting to do but haven't yet: If you can have a short fat flexible pipe at the outlet, then move the output between two or three different canals every few days it might be helpful. The soil at the outlet might not remain continuously soggy and go black and anaerobic. And different areas would get their water on different days. Or Art Ludwig suggests a branched drain system that you can operate with valves for the same purpose.
3) Roots, especially of certain trees (willows and poplars are the worry around here) are aggressive about getting into pipes and blocking them. So make sure there's at least a small drop off where the water outlets to daylight, so fine roots can't jump up to the pipe. If I attach a flexible pipe to my outlet, I'll want to be able to ensure that roots can't sneak in at the joint (because they will try if it is covered or touching the soil).
4) I looooove using greywater! My toilet is a dry composter so all the dirty outlet water of my house is good for greywater (and the school I lived at for 20+ years). At the school we couldn't control the "products" that our 25 - 100 resident teenagers were using. At my house I use commercial soap, shampoo, laundry detergent, and I think (believe, hope?) that the surface greywater canal can digest those. Importantly in both locations the water supply is abundant and we were not being stingy with it, so the greywater is not too concentrated.
The willow trees at the school love the greywater despite the unknown products, and those closest to the greywater outlet are by far the biggest trees at the school. Some fruit trees further down along the greywater system at the school seem to love it too, but they also get clean canal water from time to time, not only greywater. Years ago there was a self-seeded apricot right near the greywater outlet, and it was the biggest fruit tree in our campus. I was excited one spring when it bloomed earlier and much much more than the other little apricots -- maybe we'd get our first fruit! But after the blooms, the leaves never came out and it just stood there, dead and forlorn. So I've decided that closest to the outlet is best for things like willows, poplars and mint that love water and even waterlogging, and keep the more normal plants like fruit trees further along the canal so they can dry out between flushes of greywater. Though that also means I have to be more vigilant about roots getting into the pipe.
Works at a residential alternative high school in the Himalayas SECMOL.org . "Back home" is Cape Cod, E Coast USA.
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