Could a cell phone really trigger an explosion on Hwy 43?

Could a cell phone really trigger an explosion on Hwy 43? »Play Video
A sign approaching the Sellwood Bridge warning motorists to turn off their cell phones as crews use explosives during excavation work.

PORTLAND, Ore. - Crews working on the Sellwood Bridge project will begin blasting rocks Wednesday night and that might jolt some folks who live nearby.

For drivers approaching the bridge, an orange sign might catch your attention. It reads: “Turn off 2-way radio and cell phone.”

That had us here at KATU scratching our heads. Could a cell phone accidentally trigger an explosion?

Turns out no, it can’t. County spokesman Mike Pullen said there is no risk that a cell phone or two-way radio could set off an explosion. Still, he said the signs are required under an antiquated state law that has not been updated to keep pace with safety advances.

At one time in the past there was slight concern the electric blasting caps might be triggered by a cell signal, but new microprocessor technology has all but eliminated that chance, Pullen said.

The blasting is part of the process to excavate the hill on the west side of Highway 43. Project managers say blasting is the only safe way to remove the rocks that are underground.

"They drill through dirt and then into the rock," said Pullen. "So there's not a whole lot of debris that we expect to be flying onto the highway. But we do close the highway and bridge for five to 20 minutes at the time of the blast."

You can expect two or three explosions a night (between 9 p.m. and 3 a.m.), three nights a week for the next month.

Why is this being done at night? The answer is simple - so it won't impact daytime traffic.

Crews will sound a siren leading up to each blast and the noise from that will be louder than the actual explosion.