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Why The Army Corps Says A Proposal To Prevent Floods In Boise Is Not Cost Effective

Flickr Creative Commons
Historical picture of the building of Arrowrock Dam.

The Army Corps of Engineers Wednesday told the Idaho Department of Water Resources it could not recommend raising the height of Arrowrock Dam on the Boise River. The announcement was a disappointment to the state and the Corps.

The water resources board thought raising the height of the hundred-year-old dam would be the best way to reduce flood risk and increase water storage in the Treasure Valley. So it commissioned the Army Corps to study it. After a seven-year study costing nearly $3 million, the Corps agreed.

But Lieutenant Colonel Timothy Vale, who leads the Army Corps division that covers Idaho, told the board that even though it was the best way, it wasn’t cost effective enough to justify. That’s despite his report that a major flood could do billions of dollars of damage in the Treasure Valley.

“The Treasure Valley has the highest flood risk in my entire area of operations that I’m responsible for,” Vale says. “The Treasure Valley keeps me up at night. At this point in time we just can’t state emphatically that the benefits will exceed the costs on this project. And we owe that to the tax payer.”

Water resources board chair Roger Chase says he and his fellow members were disappointed.

“We were hoping for it,” Chase says. “You know the odds of building a new dam or raising a dam are always very slim. If we don’t come up with another study, this project will just be considered dead. It’ll go off the charts.”

Chase says the board will likely ask the Army Corps to do another study taking other factors into account in hopes of eventually getting the OK to make the dam improvements. The board paid $1.2 million, less than half, of the original study price tag. Chase says he doesn’t know how much another study would cost but thinks it would be less than the first. Meantime the board is considering another study on increasing the height of Anderson Ranch Dam.

Not everyone was disappointed with the Corps’ announcement. Marie Callaway Kellner with the Idaho Conservation League called it great news for the Boise River.

“Hopefully the ACOE’s analysis will provide the Water Resource Board and all Treasure Valley stakeholders with the impetus to identify ways we can be more resourceful and flexible in managing in the water we already have flowing through our valley,” Kellner says. 

Find Adam Cotterell on Twitter @cotterelladam

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