'Arc Flash' Likely Behind Explosion At Priest Rapids Dam

Oct 9, 2015

A surgeon at Harborview Medical Center in Seattle said the serious burns to five electricians and dam operators injured in Thursday’s explosion at Priest Rapids Dam in central Washington are consistent with "arc flash."

Pacific Northwest National Lab's chief electrical engineer Jeff Dagle explained an arc flash results from a short circuit involving high-voltage electricity.

"That current generates a tremendous amount of heat and that heat creates a plasma -- high temperatures and expanding gases,” Dagle explained.

Dagle said lightning is the same type of phenomenon.

The Grant County Public Utility District said the explosion happened in the dam's powerhouse. Two dam workers remain in intensive care with "large burns" at Harborview. Three more are getting care for less severe burns.

The men were airlifted to Seattle following the explosion at the hydropower dam on the Columbia River in central Washington.

Circuit breakers are designed to minimize arc flash and a failure with those may now be a focus of the accident investigation.

The PUD said damage from the explosion was limited to one generating unit. The rest of Priest Rapids Dam continues to operate and there is no threat to downstream communities.

KUOW's Liz Jones contributed to this report.