Designed Deluge

After much ado, PacifiCorp’s Condit Dam is scheduled to be breached at noon, pacific standard time, today.  Of note is the design for how that will occur:

The method for dam removal involves clearing sediment and debris immediately upstream from the tunnel and then drilling and blasting a 13-foot by 18-foot drain tunnel in the base of the dam [visible near the bottom of the image above] to within a few feet of the dam’s face. During the month of October, sediment and debris immediately upstream from the dam will be cleared to form a pathway and then the remainder of the tunnel will be blasted to drain the reservoir and flush impounded sediments out of the reservoir as rapidly as possible. Following the final tunnel blast, the drain tunnel will discharge at a rate of about 10,000 cubic feet-per-second – approximately 25 percent of the estimated peak discharge during the February 1996 flood event on the White Salmon River. This will drain the reservoir in approximately six hours. Rapid draining of the reservoir is expected to mobilize much of the estimated 2.4-million cubic yards of sediment that has accumulated behind the dam since its construction. Previous modeling has indicated that between 1.6 million to 2.2-million cubic yards of sediment will be discharged into the White Salmon River immediately following dam removal.”

(top image source)

3 comments

  1. Sounds pretty amazing! I wish I could watch that. I guess they’re trying to remove the dam when the reservoir is at its lowest.

  2. Or maybe not. “…the concussive force of the blast will be strong enough to make your ears bleed if you’re close enough to watch it in person.”

  3. Agreed, it would be fun to watch but i feel like the plan is very poorly thought out. Sounds like just a cheap way to get rid of a dam that can stay in operation if certain (costly) measures were taken.

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