Once more onwards to adventure! Now the thinking parts have thought, and give way to the working parts working. To begin, I'll need to create deep enough trenches to lay in lots of rotwood and soil, without creating huge barrow-mounds in my front yard which I would then have to explain to my landlord.
Step one, then, is easy : DIG. Thankfully, I like to dig, and the soil isn't very hard. The scrap of plywood you can see serves as a stable place for me to stand. I'll be digging down a total of about 18 inches, although it will shallower towards the stone wall at the bottom. That will still leave me with hugelkultur mounds which, due to gravity, may want to fall over into the roses lining the driveway, so I'll need some sort of low retaining wall. The remains of an old aboveground pool I found in the garage will furnish a bunch of regular, strong, enamel-coated hollow metal pipes which would be great anchors for a long low wall, which in turn will be made out of untreated fir 2x10x12 pieces of lumber. In retrospect, I could have made the entire wall out of nothing but free scrap 2x3s. It turned out fine, however, because I ended up using most of the fir I'd purchased for other projects, rather than building the much-larger-than-actually-needed retaining wall I initially envisioned, which would have been about 3' tall and a real pain in the neck to put together.
The lumberyard in whose dumpsters I am privileged to root around provides a lot of heavy plastic wrapping, the kind used to secure things like appliances and piles of boards to their shipping pallets. The biggest issue facing the fir I'll be using as a retaining wall is the constant contact with the ground, since I'll in fact be partially burying it to prevent soil and water from flowing underneath it. In an attempt to slow the decomposition this would bring, I'm wrapping the fir board in some of the plastic. This of course also means any moisture that does get in will be held in, rather than being able to evaporate, but I'm guessing that will be a much more minor issue than the pooling water and wet soil it would otherwise contact. The driveway performs admirably as a staging and assembly area for this assembly.
The plastic-wrapped board gets snugged down into the extra-trenched socket I've dug for it, and the metal poles will be driven in behind it, pinning it between the deep-rooted poles and the heavy cement lip of the retaining wall. This also may help with slowing rot of the border, as it means that the water trying to pile up against the board will be able to flow under it and down the inside of the wall.
You can see the board in place, with one of the scavenged swimming pool support poles hammered into the ground behind it (the white pole with the black top.) This photo also gives a good sense of the lay of the yard, the steepness of the hillside, and the extent to which I'm digging into the top layer of organic matter. You also see the constraints I'm working with - the stone retaining wall, the cedar tree, the sprawling rose bush, and the cement steps. I'm seeing what kind of abundance I can coax out of the small patch they border.
This shows both the poles and scrap timber I sledgehammered into the dirt to pinch the retaining board between posts and the wall's inside edge. You can see that my retaining wall is discontinuous; look near the hammer handle and you can see that the stone retaining wall has begun to shift with its century of New England weather, so my wall has to follow it. This is also why I didn't just run the posts in front of the wooden retaining wall and let the dirt push against the other side - I want to minimize further direct pressure on the stones of the wall, which are already bulging.
An evening shot, with my flashless cameraphone. The weird ghostly-looking stuff at left is scrap cardboard (white patches on the cardboard reflect a great deal more incident light, and show up neon-glowy.) Nothing waxed, or still with tape on it; the torn pieces of cardboard provide a base layer of water sponging, a future mat of worm-penetrable, fungus-penetrable sogginess, and an easy meal for cellulose-chewing soil bacteria. Also, it's a nice way to upcycle boxes that are too beaten up for re-use. If you look closely, you can also see that I've laid down boards and backing poles all the way to the corner of the retaining wall. Tomorrow, we start with the rotting stuff.