Monday, June 15, 2009

landfill drilling

I enjoy drilling in landfills because it allows me to be an amateur archaeologist. Date this layer by the newspaper fragments that come up in the split spoon! Name that engine part/common household appliance!

The problem, though, is the methane that builds up. If you’re doing environmental work, you may be working on old landfills that don’t have vents to release methane. And even modern landfills don’t necessarily have perfect venting systems.

The instrument you tend to use on a landfill to detect methane and other unpleasant organic compounds is a flame ionization detector (FID). Here’s the thing to remember: the FID needs a certain oxygen level to work. Otherwise, the flame goes out.

If you’re working on a landfill and you get busy collecting samples and whatnot, you may not have your eyes on the FID at all times to see if the gas concentrations are going up. If the FID flame goes out, do not stand around trying to re-start it, muttering about stupid finicky instruments, while your driller blithely continues. Chances are, if the flame goes out at a landfill, you’ve got too much methane. You need to back off. Otherwise, you end up with the following phone call:

Geologist: “I can’t get this damn FID to work. Do you have a replacement?”

Team Leader: “do you mean that the flame keeps going out? Because if it is, you need to-“

Geologist: “SHIT! We’ve started a brush fire!”

…did I mention that methane burns with an invisible flame? Not good.

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