"Back-cutting" erosion risks structural integrity of Big Bend Dam upstream of Fort Calhoun on Missouri

Eco In the Know reports that the force of water flowing from the U.S. Army Corps of Engineers-controlled Big Bend Dam, upstream of the inundated Fort Calhoun Nuclear Power Plant near Omaha on the historically flooded Missouri River, could put the dam at risk:

"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."

Arnie Gundersen at Fairewinds Associates has warned about the risk of an "inland tsunami" overwhelming Ft. Calhoun if an upstream dam fails.

NPR airs balanced story on flooding of Nebraska nukes

NPR's coverage of nuclear power issues -- and its lack thereof -- has left a lot to be desired for a very long time, including regarding the Fukushima Daiichi nuclear catastrophe. But a current story about the severe flooding at Fort Calhoun and Cooper nuclear power plants on the Missouri River at least contained input from a nuclear power critic, Tyson Slocum of Public Citizen, for a pleasant change. Slocum pointed out that the cozy relationship between industry and regulator undermines safety, and that nuclear establishments around the world are often very confident in their ability to handle whatever Mother Nature can throw at them -- until reality shows they can't. NPR reporter Robyn Wisch also included an Omaha Public Power District spokesman bragging about the ability of OPPD's Aqua Dam to keep sensitive areas dry -- then pointed out that that very Aqua Dam had suffered a major failure just as NRC Chairman Greg Jaczko was about to arrive for a tour of the plant. The Aqua Dam's collapse allowed floodwaters to lap up against the reactor containment, as well as auxiliary buildings housing vital -- and vulnerable -- emergency diesel generators.

KETV video of NRC Chairman's tour of flooded Ft. Calhoun nuclear power plant

Omaha's ABC t.v. affiliate has posted video interviews from U.S. Nuclear Regulatory Commission Chairman Greg Jaczko's visit to the flooded Fort Calhoun nuclear power plant on June 27th, including the Chairman's initial observations. KETV also covered Jaczko's visit to the Cooper atomic reactor, also on the swollen Missouri River, the day before. The Omaha Public Power District invited KETV's report on an exclusive tour inside the nuclear power plant, across the ad hoc catwalks that provide the only access for plant workers to the Fort Calhoun facilities -- unless they're willing to wade through waist deep water. KETV also got an exclusive seat on Jaczko's helicopter ride over the flooded Ft. Calhoun site. While NRC and OPPD officials assured the public that all was well at Ft. Calhoun, despite the failure of the Aqua Dam enabling flood waters to lap at the very base of the reactor containment and auxiliary buildings, the U.S. Army Corps of Engineers warns that heavier than expected rains this spring and early summer have already worsened the flooding, caused in large part by last winter's huge snow packs in the Rocky Mountains. The big question -- is more rain on the way?! 8 more feet of flood depth would push Fort Calhoun into uncharted territory in terms of safety risks. 

NRC's Jazcko at Ft. Calhoun: “You can have the potential for fuel to melt if you lose all of your cooling water”

It may be a truism, but it took out of the ordinary, strong questioning by Joe Jordan from Nebraska Watchdog to get the U.S. Nuclear Regulatory Commission Chairman, Greg Jaczko, to admit after a tour at the severely flooded Ft. Calhoun nuclear power plant that, although "highly unlikely...You can have the potential for fuel to melt if you lose all of your cooling water." Jaczko credited the Omaha Public Power District for "progress" against flood risks in the past two years, under NRC pressure, but Jordan asked if that progress was going to be good enough, given the still-rising waters of the historically flooded Missouri. Nebraska Watchdog posted a video of the exchange, in which Jaczko assured that NRC was on-site to make sure OPPD "does the right thing."

NRC and utilities assure "water event" protections holding, while Army Corps warns rain could worsen Missouri River flooding

The New York Times reports the latest entry in the Nukespeak dictionary: a "water event," also known as a flood. U.S. Nuclear Regulatory Commission Chairman Greg Jaczko, who visited Fort Calhoun nuclear power plant "partly to reassure the public" on Monday, said at a news conference afterwards “Sometimes visually you’ll see things at the site, see changes at the site, but those don’t always have an impact on the safety aspect of facilities.” He was referring to the accidental piercing of Ft. Calhoun's Aqua Dam by a Bobcat earth mover at around 1:25 a.m. on Sunday, June 26th, which deflated the 8 foot tall, 2,000 foot long "water balloon" anti-flood barrier, allowing two feet of flood waters to lap up against the reactor containment and auxiliarly buildings of the vital plant area. NRC and Omaha Public Power District officials assure that they have made preparations against another 7.54 feet of flood rise at the site. However, Col. Robert J. Ruch, commander of the Omaha District of the U.S. Army Corps of Engineers, in charge of a half-dozen major dams upstream on the Missouri, warned “We don’t like to give worst-case scenarios anymore because every time it rains, we get a new worst case.” At just after 10 a.m. Central time on Monday, June 27th, the National Weather Service of the National Oceanic and Atmospheric Administration changed the flooding forecast from "moderate" to major severity" for portions of the Missouri River in Iowa and Nebraska near Blair. The warning goes on:

 "THE FLOOD WARNING CONTINUES FOR THE MISSOURI RIVER NEAR BLAIR.
* AT  9:16 AM MONDAY THE STAGE WAS 32.5 FEET.
* FLOOD STAGE IS 26.5 FEET.
* MODERATE FLOODING IS OCCURRING AND MAJOR FLOODING IS FORECAST.
* FORECAST...THE RIVER WILL CONTINUE RISING TO NEAR 33.1 FEET BY
  EARLY WEDNESDAY MORNING.  ADDITIONAL RISES MAY BE POSSIBLE
  THEREAFTER.
* IMPACT...AT 33.5 FEET...WATER REACHES LEVELS NOT SEEN SINCE THE
  FLOOD OF 1952.  SIGNIFICANT FLOODING WILL BE OCCURRING FROM BLAIR
  TO FORT CALHOUN."