pressurized water in the cracks
Saturday, October 25 2008
I knew it was going to be a rainy day, but it's been months since I've experienced the kind of rain that would keep me from working outdoors on a project as engaging as the greenhouse. The rain was coming down as a light drizzle when I handtrucked a bag of mortar and three concrete blocks down to the site using the ramp provided by Dug Hill Road. I'd only laid six blocks by the time a strong shower swept through. Though temperatures were warmer than can normally be expected at this time of the year (in the low 60s), there are few experiences as miserable as standing in an autumnal downpour. Normally a little rain is good for curing mortar, but this was falling powerfully enough to risk eroding it away, so I covered the new blocks in empty concrete sacks.
Meanwhile Gretchen was doing one of her weekend kitchen marathons, testing recipes for Thanksgiving and doing preliminary work on assembling someone's birthday cake. She needed some supplies, and since I can always justify an errand to town to get more concrete blocks, I drove into town to fetch them. I took the four door, which would allow me to haul a heavier payload even if I brought along the dogs (which I did). This time I managed to haul 13 concrete blocks along with 80 pounds of mortar and 80 pounds of concrete. The four-door is a surprisingly spacious container for transporting blocks, even with the backseat reserved entirely for dogs.
While I was out, the showers grew in intensity, eventually ramping up to a fierce continual downpour punctuated every twenty minutes or so by a bright flash of lightning followed by peculiar-sounding thunder.
Back home, I was curious to see how my greenhouse drainage system was handling all the runoff. Darkness had descended, so I went down to the site with a flashlight in addition to an umbrella. I found four inches of water pooled up in the lowest third of the excavation. Water had backed up behind the drain (into which I'd stuck a metal can to keep out debris) and had risen to the level where it was now draining from a second pipe that perforates the footer to the ring drainage, a pipe I'd installed as a possible air supply for a composting toilet. Hoping to drain the greenhouse like a bathtub, I reached into the drain pipe to remove the can, but the pressure of the water behind it made this impossible.
More troubling than the pooling water was a visible artesian spring spurting from the shale bedrock near the footer of the south wall a couple feet from the uphill (west) edge of the excavation. It had enough force to form a dome of turbulence over a quarter inch above the surface of the pool it was creating. I'd thought that by digging down to bedrock and ensuring that the surface of the bedrock sloped away from the center of the greenhouse all the way around, and by ringing the excavation with perforated drainage pipes, I'd keep all ground water out. I certainly hadn't considered pressurized water in the hairline fractures of the bedrock! I probably could have intercepted those temporary springs if I'd been willing to chip a deep trench into the bedrock along the uphill side of the excavation, but that bedrock had been smooth and perfect and had naturally sloped away from the center of the greenhouse, so I'd thought I was safe to leave it alone. One possible solution to this problem would be to use a masonry drill to puncture a series of holes in the bedrock just uphill from the greenhouse, allowing pressurized water an artesian escape path closer to its uphill source.
There are several dozen square feet of the greenhouse floor where the shale bedrock is still covered by a thin layer of soil I'd never gotten around to removing. Tonight this soil seemed especially soft, so I dug into the center of the softness and discovered a second artesian spring, one that had presumably been corked up by the weight of several feet of soil until I'd removed all but a couple inches of it.
These springs shouldn't be too difficult to manage; I can construct a series of shallow trenches in the greenhouse floor to gather the water and direct it into the drainage system. I can even bury pipes in the bedrock and cover them with a proper bluestone surface.
The happiest moment of the entire day came when I went down to the end of my sixty foot drainage pipe and watched it doing its job. A stream of water as thick of my arm (and nearly as long) was gushing forcefully from it, carrying away the runoff that would otherwise be making my greenhouse into a swimming pool.
This evening Gretchen and I watched Young at Heart, a documentary of a program organizing a group of elderly people into a chorus specializing in the singing of rock and roll (everything from James Brown to Sonic Youth). As I watched, I realized that the key to the success of this chorus (in addition to the heartwarming and cognitively-dissonant spectacle of old people rocking out) is the the masterful arrangement of songs. The arrangements take advantage of the respective talents of the members, some of whom can sing and others who do everything strictly spoken-word. We've all heard "We Are the World" and are aware that pop music can be performed as a kind of relay race, but some of these arrangements were actually better than the original. I thought, for example, that their version of Sonic Youth's "Schizophrenia" was much improved over the original.
Of course, whenever someone makes a documentary featuring over a dozen octogenarians, there are bound to be a few fatalities along the way. Then again, that too is in the spirit of rock and roll, where death is an ever-present sidekick no matter how young the performers are.
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