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lost mouse ball
Thursday, September 25 2008
Yesterday I'd stabilized the newly-laid drainage pipe with a few strategically-placed piles of rock in the ditch. The ditch and pipe ended up being just under sixty feet in length. I'd confirmed that water put in the greenhouse end of the pipe flowed out the other end, but I wasn't sure if there were a few low spots in it (particularly in the lower half, where the pipe lies nearly level) where debris might collect. So on a whim I tried rolling the rubberized steel ball from an old computer mouse into the top end of the pipe. Suffice it to say, that ball is still in the pipe somewhere, and no amount of water would flush it out. Of course, if there was ever enough debris in the pipe to impede flow, water pressure would force it out.
By some point in the day, I'd managed to completely bury the pipe beneath loose rock. I mostly used fragments of shale for this, since this is about the only use one can make of broken shale. It's important to note that this drainage pipe is not perforated and I could have simply buried it in clay. But I wanted water to be able to flow on the outside of the pipe as well as on the inside, allowing water to drain down the ditch at the lowest level possible. Water draining this way is likely to be absorbed into the surrounding bedrock layers, leaving the drainage pipe completely dry in all but the rainiest of seasons.
Later I built up a layer of fist-sized sandstone river rocks in the fifteen feet of ditch nearest the greenhouse. The ditch here was well over three feet deep, and I wanted to use some of that subterranean space as a thermal mass for the greenhouse. The idea is to blow solar-heated air through a pile of stones when the sun is out, and then recoup that heat later after the sun goes down by circulating air again. To ensure that air would circulate to the end of this pile, I ran a ten foot section of four inch pipe along the top of the pile. Eventually there will be two four inch ducts going through the foundation wall to carry air to and from this mass of buried rock. Unfortunately, the top of my buried mass ended up being only about six inches below the surface of the ground (well above the frost line), so I had to lay down a thick carpet of styrofoam just beneath the topsoil layer. Between the styrofoam and the topsoil, I put down a layer of cardboard and ratty old plywood to keep soil from filtering into the voids of the rock pile beneath. The cardboard and plywood will rot quickly beneath the soil, but it should give the soil above it a chance to stabilize (and perhaps become innervated by roots) first.
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