A tree did it

  • Cartoon of tree pulling the plug

    Diane Sylvain ?
  On July 2, a blackout in the West left 2 million people without electricity. The culprit, it turns out, was a cottonwood tree in southeastern Idaho. Or perhaps it was the maintenance folks who allowed this lone tree to grow so close to a power line that electricity jumped to it. When this "flashover" occurred on what was a swelteringly hot day, line after line tripped out, says Corry Alsberg, who speaks for the Western Systems Coordinating Council. Lots of electricity was moving around power lines that day, she says, and the unusual conditions probably won't be duplicated.

On Aug. 10, however, the West's power grid failed again. This time 4 million people lost electricity for everything from air conditioners to traffic lights, mostly in California. Alsberg says the culprit was "random multiple transmission line outages, most likely from overloaded, sagging powerlines." There was also another flashover to a tree, she adds, "but no, this is not a trend." The council is a voluntary group that promotes electricity reliability in 14 Western states plus parts of Canada and Mexico.

*Betsy Marston

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