Engineers Working On Substantial Crack In Wanapum Dam Spillway (Columbia River)

[hatrack]

n central Washington state, teams of engineers are scrambling to figure out what’s gone wrong with part of the Wanapum Dam’s spillway structure. The problem with the dam is on a structure called the ogee, a big piece of concrete that is anchored to the bottom of the river. It has a big curve on the top where the water flows over it.

It’s like a river speed bump. When the spillway gate is lifted, the water flows through from the upriver side of the dam to the downriver side over this ogee. This is how dam operators let extra water through the dam that’s not needed for power production.

But the ogee is cracked all the way across its upstream face, underwater. The dam operators and engineers aren’t sure how deep the crack goes back into the massive concrete hump, but that’s what they are trying to figure out.

“Right now the main focus is that particular area," says Chuck Berrie, who helps manage the dam for the Grant County Public Utility District. "But we are going to do a complete and thorough evaluation of the structure before we’re through.”

EDIT

http://nwnewsnetwork.org/post/outside-experts-weigh-columbia-rivers-damaged-wanapum-dam

[dixiegrrrrl]

1. UPDATE:Emergency downgraded at Wanapum Dam

SPOKANE, Wash. (AP) - The crack in a spillway pier at the Wanapum Dam has been downgraded to a "non-failure emergency," meaning the pier is no longer considered at risk of collapsing, the Grant County Public Utility District said Wednesday.

The downgrade is the result of engineering surveys conducted Monday and Tuesday that show the fractured area found on one of the dam's spillways was continuing to stabilize, the PUD said in a press release.
http://www.komonews.com/news/local/Emergency-downgraded-at-Wanapum-Dam-248609351.html

[Nihil]

2. Still a major problem but they've reduced the pressure on the damaged bit.

i.e., no longer an "imminent emergency" but 'merely' a "serious problem" ...


From the OP article:
>> Still, what’s troubling to experts on dams and concrete structures is that
>> the ogee is not only cracked, it has slipped a little.

>> And what’s caused the mighty crack in the Wanapum Dam is the big question.

>> What troubles Osteraas, is that the dam failed with no clear cause.
>> It's what disaster experts call a sunny day scenario.
>> “When things just fail in the normal course of events, under loads and forces
>> that we thought were in the safe region"


From the update:
> The crack has closed and a section of the spillway pier that had shifted has
> nearly returned to full alignment, the PUD said. That's the result of the utility
> lowering the water level by 26 feet in the reservoir behind the dam, reducing
> pressure on the damaged spillway, the PUD said.

> Officials are still trying to determine what caused the crack and have not developed
> a plan for repairing the damage,

> The reservoir level will remain at 26 feet below normal for the foreseeable future


Again from the OP:
>> Right now, the mighty Columbia River is at its low winter levels.
>> But soon spring snowmelt will swell the downstream river flows and
>> sensitive salmon runs will be making their way up stream.


Something to keep an eye on ...