Which poses a problem when those forests are on fire.
But suggestions that the Interstate 90 fires threaten to plunge the Pacific Northwest into darkness and could produce blackouts as far away as California are greatly exaggerated, a Bonneville Power Administration official said Wednesday afternoon.
Hansen's assurances were proved true Wednesday night, when the 3,000-acre Tarkio fire overtook the Garrison-Taft power lines west of Alberton. The lines tripped and were taken off the grid, and electricity was routed on other lines.
The Garrison-Taft lines carry power originating in Colstrip. The lines have different names between substations, and the Garrison-Taft line runs for about 100 miles between a substation near Garrison and another southwest of Thompson Falls, according to Hansen.
There are actually two 500-kilovolt lines traveling on the single set of towers. The lines are but a tiny part of a massive grid that carries electricity across the United States. But Garrison-Taft's capacity of 2,200 megawatts is huge, capable of providing nearly enough electricity to power two cities the size of Seattle.
While the lines themselves generally run above treetop level, wildfires can damage transformers or towers and take the lines out.
The BPA will shut down lines on its own if firefighters must move too close to it.
Both water and smoke are conductors, and electricity can arc from the lines to the ground. (The Tarkio fire's rapid approach Wednesday night, in fact, caused the lines to arc and shut off.)
"If that amount of power, instead of running down the line, runs to wherever it arced to - say, to someone standing underneath with a hose - they won't be there anymore," Hansen said. "If the fire gets too close, we'd take out the line for the protection of firefighters."
The Garrison-Taft line is part of 15,000 miles of lines the BPA has in the Pacific Northwest.
"There's a lot of redundancy built into the system," Hansen said.
The power from Colstrip could be rerouted over other lines or power could be carried into the system from a source other than Colstrip, if the Garrison-Taft line goes down, Hansen said.
There are several reasons the lines are only carrying 500 megawatts right now, far below the 2,200-megawatt capacity.
"A lot of the power generated by Colstrip could be being used by Montanans themselves," Hansen said. "And a lot depends on the weather. It's cooled down over here, so demand is down."
Firefighters worked throughout the day to prevent the Tarkio fire from reaching the south slope of a mountain that leads up to the power lines, which run along the ridge.
"South-facing slopes are the ones that get the sun all day long," said Mike Cole, a fire information officer on the I-90 fires. "They have longer to heat up and dry out quicker than north-facing slopes."
Firefighters controlled one fire that had spotted on the south slope Wednesday and were searching to make sure no others had started, Cole said. But high winds overwhelmed all efforts at control shortly before 7 p.m.
Reporter Vince Devlin can be reached at 523-5260 or at vdevlin@missoulian.com.
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