Thursday, June 30, 2011

Raw Footage of Fort Calhoun Nuke Plant Fly-by from AP


Anonymous said...

Robbie001 sez:

This article seems to have been removed from the news after 12 hours. Here's the tantalizing Google description.

"Nuke query: What if dam breaks?
Omaha World-Herald - 12 hours ago
The Fort Calhoun reactor, taken off-line for maintenance in early April, ... We're constantly asking questions of (Fort Calhoun and Cooper) and of ..."

Unfortunately this is what you find when you click on the link.

"The article requested can not be found! Please refresh your browser or go back. (OW,20110630,NEWS01,110639977,AR)".

I found the story after a little looking apparently they are going to shutdown the Big Bend Dam today to look for erosion problems but every thing is "OK". The Army Corps of Engineers claims the entire dam system has operated at these levels "several" times before but they don't name the occurrences or their duration. I think it is BS because we didn't hear any problems from Fort Calhoun in the last biblical flood of 1993.

From what I understand the flooding is unprecedented in the history of the dam system according to the Wiki on the flood the Gavins Point Dam began releasing a record of 150,000 cubic feet (4,200 m3) of water per second on June 14, 2011—about twice the previous record release in 1997." (it has since been increased to 160,000 cubic feet)
"The Corps in attempting to juggle the control of the release with the fact that all reservoirs are 100 percent or more of capacity -with the exception of the Fort Randall Dam- has doubled the record release of water in the river's five North Dakota and South Dakota dams"

"On Friday, the corps plans to interrupt spillway releases for several hours at Big Bend Dam so it can check there for possible erosion, he said.

“None of the erosion issues are dam safety concerns,” he said. The dams “are performing really well, just like we designed them ... they have performed to these levels several times before.”

Anonymous said...

Robbie001 sez:

This article point to a lot of upstream sediment transport at the Big Bend Dam they're having problems with the downstream water filtration intake. Sediments increase the abrasive effects of turbulent fast moving water. This could increase the scouring effect and promote spillway undercutting in the weeks to come. It will be telling if they don't resume operation at the same volume that may point to reduced confidence in the structure.

FORT THOMPSON — The U.S. Army Corps of Engineers will close the spillway gates at Big Bend Dam today to inspect how the water has affected the structure.

Typical Failure Modes for Dam Spillways:

Downstream erosion of soil or foundation material at the outlet end of a spillway or outlet pipe and eventually undercutting, which results from turbulent flow, can also be a cause
for spillway failure. Installation of aprons or cutoffs in these areas can help prevent this
situation. Failures could ultimately result from loss of support for either a concrete apron, abutment wall, and outlet pipe header due to undercutting.

According to the Army Corps of Engineers everything is OK let's see if they go back to 150,000 cf/s as a release volume.

"Fort Thompson, S. D.—The July 1 inspection of the spillway structure at Big Bend Dam revealed no significant concerns, said John Bertino, Chief of Engineering with the U.S. Army Corps of Engineers, Omaha District".

"Big Bend Dam, South Dakota. The Missouri is flowing through the emergency spillway at Big Bend Dam. The water shooting through the spillway gates is moving so fast and with such erosive power that it is back-cutting toward the earthen dam itself. Left unchecked, the water could threaten the structural integrity of the dam. Although at present, that scenario is highly unlikely. Nonetheless, the Army is concerned about the erosion. To address the issue, a dump truck hauled large blocks of quarried stone to the trouble spot. The Army plans on dropping the rock atop the eroded bank sections to halt the back-cutting. A civilian working for the Army acknowledged that the engineers did not expect to be in this predicament when they first opened the spillway gates to the Missouri’s floodwaters. The back-cutting caught the Army by surprise. But the military is on top of the problem, with tons of pink Sioux quartzite."

arevamirpal::laprimavera said...

It's an earthen dam?? When I hear comments like "The dams “are performing really well, just like we designed them", I cringe.

Anonymous said...

Robbie001 sez:

According to the wiki it is a "rolled earth" or "embankment" dam. It looks like all the other big dams on the upper Missouri are too. Oahe and Garrison are some of the worlds largest.

"Rolled Earth Dam (Earth Fill or Earth Dam) - An embankment dam in which more than 50% of the total volume is formed of compacted fine-grained material obtained from a borrow area."

Typical Failure Modes of Embankment Dams

Anonymous said...

Robbie001 sez:

This is an interesting FaceBook page the pdf details each dams condition many of them are just a few feet from topping the spillway. Spillway "overtopping" is one of the three major dam failure modes. We better hope none of these earthen dams becomes over-saturated if any of them fail it may lead to a cascade of dominoes falling. The heavy local rains aren't helping matters it looks like it may be another month before the dams can lower their release levels.

US Army Corps of Engineers, Omaha District

Detailed Public River Report

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