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Permafrost
Tue Apr 19, 2005
Listen in RealAudio 
Many contractors wait until spring to dig into thawed soil to lay a foundation. Builders in Alaska, particularly northern Alaska, donıt have that luxury. Thatıs because more than 80% of the subsoil is permanently frozen.
Hi, I'm Bryan Yeaton and this is The Weather Notebook.
This frozen barrier is called permafrost. As Amy Mayer reports today, builders have found creative answers to frosty challenge.
First, a definition, from geotechnical engineer Steve Adamcsak.
SA: Permafrost by definition is ground that remains frozen for two consecutive winters and an intervening summer.
You take soil samples to see if you've got it. A drill rig sends samplers through a hollow-stem auger into the ground.
If there is permafrost, your heated building will sag as the ground melts under it. Unless you build accordingly. So you keep the ground frozen, you thaw it before you build or you build so that as the ground melts you can adjust your house.
SA: That means every spring and fall you may have to get out there and relevel your structure.
Professor Rich Seifert teaches a cold climate home building class. He says none of these options is ideal because permafrost is unpredictable. SA: It's the Forrest Gump soil you never know what yer goin' to get.
Seifert advises against building on it. Though the land can be cheap...
SA: you pay a lot for water you pay a lot for sewage disposal and you may have problematic conditions with the deterioration of the permafrost on the house. So... And you may have financing problems. So all these things matter.
With permafrost under my cabin, I'm Amy Mayer.
The Weather Notebook is a production of the Mount Washington Observatory. Our program is supported in part by the National Science Foundation and Subaru of America.
Today's Links
What is permafrost?
http://sts.gsc.nrcan.gc.ca/permafrost/whatis.htm
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