How to Make a Methane Burrito

A peek at the installation of a methane-mitigation system

Comments (0) By Howard Blume Wednesday, May 2 2001

Photos by Slobodan Dimitrov

A worker tapes a woven, fabric skin - filled with gravel - around a venting pipe that will sit in a trench beneath a new house in a Riverside County subdivision. This is your basic methane burrito. The trenches snake under where the living room, the bathroom and the garage will be. Methane from underground will enter the pipe before reaching the bottom of the house. The pipe will then siphon the methane away.

After the trenches are filled in, workers create two layers of barriers as an added protection against methane entering the house. The two workers pictured are stepping on the first barrier, which is called Liquid Boot. It is a spray-on material that dries quickly. Above that, the workers are spreading a prefabricated sheet of high-density polyethylene.

The smoke test. Now the workers get to see if their system is working. They inject smoke underneath to test whether the barrier is properly sealed. If all goes well, the smoke exits from the vertical pipe. If not, smoke will visibly leak through the barrier. So far so good. The vertical pipe will eventually lead to the roof, where methane will vent harmlessly into the atmosphere.

A vent-and-barrier system with utility pipes poking out, soon to be hidden from view by concrete and another suburban house, like any other, except for the tell-tale black piping poking above the roof.

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