Fifty years ago, a mathematical mistake was made designing the Wanapum Dam near Vantage.
An engineer miscalculated the amount of concrete and steel needed to hold back the Columbia River.
Last February, one of the dam’s spillways cracked because it simply wasn’t strong enough. Now steel rods are going to be used to reinforce all 13 spillways.
The mistake will cost the Grant County Public Utility District $61 million. Gov. Jay Inslee was asked about the mistake Wednesday as he toured the damaged dam.
“It appears to be literally one individual who made the mistake, who’s no longer with us and hopefully this is going to be fixed,” Inslee said.
The utility district will now check its second dam at Priest Rapids, even though it has a different design, to make sure there were no mistakes made in that project.
“Absolutely, without a doubt, we’re going to be rechecking the math,” said PUD spokesman Thomas Stredwick.
There are 11 Columbia River dams in Washington. KIRO Seven called all the operators. The Chelan PUD said its spillways at Rock Island and Rocky Reach were anchored right into bedrock, unlike the dam at Wanapum.
The Douglas County PUD also said its spillways at Wells Dam are substantially different. Federal agencies operating the other dams aren't worried. They claim to have robust and active dam safety programs requiring regular inspections.
“I’m unaware of reasons to believe there would be a systemic problem throughout our dam system. That would be surprising to me. Nonetheless, I’m going to ask some engineers to make sure that’s the case,” Inslee said.
After the crack was discovered in the Wanapum Dam, the reservoir behind the dam was lowered by 30 feet to ease pressure on the structure.
Thirty-seven miles of river shoreline were closed to the public. The reservoir will remain closed all summer. There will be no boating, fishing or swimming in the Wanapum Reservoir.
KIRO
