Preparing Hanford for a major earthquake

Preparing Hanford for a major earthquake

Credit: Bill Lascher

A docent at Richland's CREHST Museum explains the history of the Hanford Site, the area outside of Richland where the U.S. government produced plutonium for nuclear weaponry for nearly half a century.

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by Bill Lascher

NWCN.com

Posted on May 26, 2011 at 10:37 AM

Updated Tuesday, Nov 12 at 1:08 AM

Read Part 1: Research shakes up seismic knowledge near Northwest nuclear plant

Read Part 2: Seismic concerns under Hanford came long before Japan quake

Neighbors

Of course, shifting knowledge about the Yakima Fold and Thrust belt doesn't just have direct implications for the Columbia Generating Station. As separate as the Columbia Generating Station and the Hanford Site may be from a management and oversight standpoint, the fact remains that the two are inextricably linked, if for no other reason but geography.

What happens, for example, if the World War II era “Canyon" buildings where uranium was processed collapse? What if the K-basins that store fuel from Hanford's old N-Reactor leak? What if a radioactive release at Hanford hampers responders' ability to address a crisis at the Columbia Generating Station?

Eric Holdeman, an emergency management consultant who previously worked at the Washington State Division of Emergency Management, says there's a proximity challenge for the Columbia Generating Station.

“When you have hazards in proximity to one another, everybody is doing their own thing, but it would be interesting to know to what degree they've looked at their 360 degree view, not from natural hazards but technological hazards," Holdeman, who writes the “Disaster Zone" blog, said. Typically, he said, disasters like the one in Japan aren't single events, but multiple events that together cause worse problems to occur. “I've just lived long enough to know never say never.”

Even given the risk of unexpected events, there's only so much that can be done about major infrastructure.

“Once a facility like a nuclear power plant is built, it's built," Holdeman said. “You might be able to do something with the backup power, but the containment vessel is the containment vessel, it is what it is."

Ivan Wong, a board member at the Earthquake Engineering and Research Institute, says the seismic hazard in Eastern Washington has probably been underestimated.

“Seismology and geology and this whole business of earthquake hazards is not a perfect science, so as we learn more about earthquake processes and earthquake hazards we have to go back and revisit what we've done in the past," Wong said.

Each earthquake brings new information that contributes to our understanding of risks, Wong said. Regulatory agencies keep tabs on scientific developments as they evolve. Critical structures like power plants are either safe from newly discovered risks, or they're forced by regulators to retrofit, he said, and therefore the public can feel confident in their safety.

Room for new work

There are significant fears elsewhere in the Northwest.

The Cascadia Subduction Zone – which stretches approximately from Northern California to Vancouver, British Columbia – will someday, possibly soon, unleash a quake similar to the one in Japan. The Northwest is less prepared for subduction quake than was Japan or Chile, where another subduction quake struck in February, 2010, but such an event probably wouldn't cause heavy damage in the Tri-Cities.

Nevertheless the Tri-Cities aren't completely safe.

One of Washington's largest documented quakes hit in 1872. Geologists are still trying to pinpoint exactly how big it was, or where it was centered, but it's widely believed to have been a 6.8 temblor with an epicenter near the south end of Lake Chelan, perhaps as far south as the town of Entiat. That's about 100 miles from the Columbia Generating Station.

It's also unclear what sources inform Energy Northwest's assessments of the Columbia Generating Station's risks, since its probablistic safety assessments still refer to a 1994 study, long before much of the current research and data came together.

To be sure, the Columbia Generating Station based its design specifications on the far larger quake near Lake Chelan. Another significant large quake in the region was the 1936 shaker near Milton-Freewater, in Oregon. These quakes are still quite recent from a geological perspective, and the monitoring now in place at Hanford only reveals so much about the record.

In fact, there just isn't much seismic data from the region surrounding the Columbia Generating Station. The first seismic monitors were installed at Hanford in 1969. The largest quake they've ever recorded was a 3.8 (the most recent quake detected in the region was a magnitude 3.3 shaker just east of Hanford on April 29), but that doesn't mean a larger quake can't occur.

“The 20 to 30 years we've been monitoring is a very short time," says the USGS geophysicist Joan Gromberg.

In the 1970s, some of the first significant work at Hanford to support a planned Basalt Waste Isolation Project became the first detailed look at the region's tectonics. That meant working on mapping the region's faults and folds, work that continued until 1989, when the DOE abandoned the project to focus on a proposed nuclear repository at Yucca Mountain, Nevada. Afterword the only data collected was seismicity, which helps provide information about how much the ground shakes or may shake but doesn't give a sense of the long-term frequency or history of earthquakes.

When Reidel, who came to Hanford to work on the Basalt project, and Al Rohay, who managed the Hanford Seismic Assessment Program for the DOE until the task was transferred to a Hanford Contractor this month, wanted to trench Rattlesnake Mountain, a more than 3,000 foot high treeless mountain that dominates the Horizon, they couldn't secure funding. Without the DOE building anything new, there wasn't a justification to study potential faults any further.

“Out of all the industrialized countries, the U.S. has the least amount of geologic mapping done, which is kind of a sad state of affairs," Reidel said.

United States Geological Survey paleoseismologist Brian Sherrod says his and his colleagues' ability to map the state's seismic risks is limited only by the amount of resources the federal government is willing to throw their way, not by a lack of subjects to study. They just need the time, funding and other help necessary to collect and sift through data.

The more data they collect, the more geologists will be able to shift a raging debate about the Columbia Plateau and the Yakima Fold and Thrust Belt: Whether these regions thin- or thick-skinned.

Thick-skinners think that deformations in the Columbia River Basalts cut deep into the seismogenic – or earthquake producing – part of the earth's crust, and can thus cause larger earthquakes. Thin skin adherents say a structure known as a “decollement"– essentially flat faults where layers of rock slide across one another and bunch up into rises similar to the way a rug pushed across a floor might – shaped the Yakima Folds as it slid between the basalts and the crystalline basement.

Sherrod says his newly accepted paper puts forth a thick-skin model and that he and his colleagues have the data to support that hypothesis. But that doesn't mean geologists have enough data about the region.

“I have thought for a long time there is just a general lack of knowledge about active faults in Central Washington," Sherrod said. “There's a lot of room for new work."

People like Sherrod and Richard Blakely might be finding the big faults, determining how frequently earthquakes occur on them and understanding how big they can be. There's still one question they can't answer.

“When's the next big one going to be?"Sherrod says. “That's the one we always get. We just don't know.”

This story was funded in part by the Spot.Us community

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