Sunday, January 27, 2013

Another Reason to Love a Snowy Day

Raise your hand if you grew up in a house with a septic tank and drainfield instead of being on a community sewer system. My hand is up.

I remember conserving water so we wouldn't have to have the tank pumped as often. I remember an occasional problem with the drainfield. But I don't remember the drainfield freezing.

Peter Leschak, a northern Minnesota writer, had a commentary in today's Star Tribune that points out one of the many unlooked-for consequences of climate change: As Minnesota becomes both warmer and dryer, we no longer have reliable snow cover, which means the ground freezes farther down.

The septic tanks commonly used for rural homes hold a thousand gallons; the typical household produces 150 gallons of waste water and sewage per day. Clearly, it doesn't all stay in the tank. Leschak explains that the liquid parts flow out of the tank into the drainfield through shallowly laid, perforated pipe. It has to be shallow to allow for the presence of the soil bacteria that treat it.

Minnesota, but especially northern Minnesota, used to have reliable snow cover of a foot or more. It would snow several feet in December, and that snow would stay until March, when we usually would get another foot or two. (The average annual snowfall in the Twin Cities is about 48 inches; up north it varies from 24 to 70 inches, depending on whether you're talking about the dryer northwest or the wetter northeast.) Leschak said that at least six inches are needed to protect a drainfield.

The winters of the past ten years, however, have been more likely to be much less snowy than that, if not snowless altogether. Leschak's drainfield first froze in 1990. He then had a decade of peace, but since 2002 it's frozen half the years.

What are the results of a frozen drainfield? Sewage backing up into your basement.

Options to deal with the problem include extreme water conservation, getting the tank pumped constantly ($185 a pop), or paying to heat your drainfield. And this is the extra ironic part:

For around $1,400 you can purchase a unit -- "easy to install" -- that will force heated air through your entire septic system. I checked it out and determined that, given our rural electric rates, running the unit the entire winter (which is what you'd have to do) would demand about 3,000 kilowatt hours, the equivalent of seven months of our regular electricity consumption...

The math didn't work for me, but more crucial was the plain absurdity of heating our poop.

Think of it: In order to prevent a drainfield freeze-up caused by milder winters, we'd increase our carbon footprint and thus accelerate, however modestly, the climatic warming that's the root of the problem in the first place. I'm unsure whether the appropriate response to this is laughter or tears.
And now we all shake our heads. One more unpredicted consequence of climate change.

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