John Ley challenges claims about the I-5 Bridge’s earthquake risk, citing low odds for a major Cascadia quake in 50 years and urging investment in multiple seismically sound bridges to reduce congestion.
Rep. John Ley suggests transportation dollars should spent wisely, ‘we can provide reasonably priced solutions that add vehicle capacity and seismic resilience’
Rep. John Ley
For Clark County Today
Administrator Greg Johnson and the Interstate Bridge Replacement Program (IBR) team regularly tell us the Interstate 5 Bridge could come down in an earthquake at any time. They’re using scare tactics regarding the Cascadia Subduction Zone (CSZ) and the potential for a magnitude 9.0 earthquake. The scare began a decade ago when the New Yorker Magazine quoted Kenneth Murphy, who directs FEMA’s Region 10. “Our operating assumption is that everything west of Interstate 5 will be toast.”
Rep. John Ley
Former Governor Jay Inslee played the scare tactic card as well, when he and then Oregon Governor Kate Brown began the current effort to replace the Interstate Bridge. “This bridge could fall down any day, with a small seismic event.” Yet the two Interstate Bridge structures did not fall down in the magnitude 6.8 Nisqually earthquake in 2001. Nor did the bridge fall down in earlier 1949 or 1965 earthquakes.
But what are the chances “the big one” will happen in the next 50 years? Presumably that’s half the expected life span of a new bridge. What do the real experts say?
The Washington Department of Transportation shows Clark County in a reduced risk zone compared to the Puget Sound and Washington coast. Zone C has the highest risk for damage. Graphic courtesy WSDOT
Erin Wirth is with the US Geological Survey and the M9 Project at the University of Washington. She believes there is approximately a 14 percent chance of a magnitude 9 earthquake happening in the next 50 years.
Nick Zentner teaches geology at Central Washington University in Ellensburg. He also echoes Wirth and other experts, predicting a 14 percent chance of “the big one” occurring in the next 50 years.
In 2013, the Cascadia Region Earthquake Workgroup (CREW) working with FEMA and the National Earthquake Hazard Reduction Program (NEHRP) published an extensive report indicating there was a 10 percent chance of the M9 CSZ quake in the next 50 years. Harold Tobin, director of the PNW Seismic Network says Oregon is “pretty boring” when it comes to earthquakes. Some other experts have predicted a 15 percent chance.
Let’s look at this another way, if there is a 10 to 15 percent chance of a magnitude 9 “full rip” of the CSZ earthquake in the next 50 years, that also means there is an 85 to 90 percent chance the big one will NOT happen in the next 50 years.
To me, that’s the most important take away. The real experts, the people with the greatest knowledge of geology and earthquakes believe there’s at least an 85 percent chance the big one won’t happen in the next 50 years. That means we have time.
We can focus on reducing traffic congestion, which is the people’s top priority while adding new bridges built to current seismic standards. The IBR’s own data shows 70 percent of citizens want saving time and reducing congestion as their first priority for transportation dollars.
We don’t need to tear down the current two historic bridges. They did just fine in the 2001 Nisqually earthquake. The odds are they’ll do fine if a smaller magnitude 7 earthquake were to happen in the next 50 years.
Portland economist Joe Cortright says it’s “a convenient excuse to demolish the existing bridges”. They don’t have a geotechnical study that supports their claims that it will collapse in a 500 year event, he added. He highlights an example in British Columbia for a 100-year old railroad bridge across the Fraser River.
A 2014 study in Japan found that closely spaced logs serving as pilings for bridges increase the degree of compaction by 106 percent. “This method is fail-safe against liquification damage” they reported. Graphic courtesy Bob Ortblad
Johnson and his team talk about the wooden pilings the current bridges are built on trying to make you believe that is a risk. Yet recent research from Japan indicates that wooden pilings can perform effectively during earthquakes, particularly in regions with soft soil.
Key findings include:
Flexibility and Damping: Wooden pilings exhibit flexibility, which allows them to absorb seismic energy and reduce the impact of ground shaking.
Soil Interaction: The performance of wooden pilings is influenced by the type of soil. They tend to perform better in softer soils, where their ability to move with the ground can mitigate damage.
Comparative Studies: Studies in Japan have compared wooden pilings to concrete and steel alternatives, often highlighting the advantages of wood in terms of cost, sustainability, and seismic resilience.
Finally, the IBR team is not designing the replacement bridge to withstand the magnitude 9 “full rip” of the Cascadia Subduction Zone. They are designing to a 500 year standard instead of the more robust 1,000 year standard, or the maximum 2,500 year standard.
Many transportation experts believe the current two bridges could be “repurposed” and serve as a local connection between Hayden Island and Vancouver. The added benefit is a much more user-friendly path for the bicyclists and pedestrians who use the bridge.
A separate bridge or an immersed tube tunnel could be built that would add vehicle capacity to the region and the I-5 corridor. The BART tunnel in San Francisco survived the 1989 earthquake and served the region in the aftermath of the collapse of part of the Bay Bridge.
In 2008, the Regional Transportation Council (RTC) published a “Visioning Study” which identified the need for two new bridges over the Columbia River; one west of I-5 and the other east of I-205. Zero planning has happened for either of these two needed transportation corridors.
The logical approach to seismic concerns would be to bring the I-205 Glenn Jackson Bridge up to modern seismic standards. This would guarantee one freeway would remain viable for regional transportation needs “if” the big one were to happen over the next hundred years. Built in 1982, its design is closest to current seismic standards.
Oregon is upgrading the I-205 Abernethy Bridge near Oregon City for seismic resilience and adding a lane for vehicle capacity, providing a legitimate north-south pathway in case of a disaster. They have no plans to fix/replace the I-5 Marquam Bridge over the Willamette River. In a major seismic event, almost all the Willamette River bridges would be damaged or destroyed.
The Oregon Department of Transportation (ODOT) has estimated that 19 of the bridges on I-5 are likely to be heavily damaged during a great subduction zone earthquake, and five are likely to collapse. “Virtually all major highways will be closed in the immediate aftermath of a quake; it will take months to open many highways — and years before mobility is fully restored,” they report.
Earthquakes in the Pacific Northwest come from a variety of sources including crustal earthquakes, deep earthquakes, and the Cascadia Subduction Zone. Graphic courtesy M9 Project
We need redundancy – multiple alternative pathways for vehicles and responders when the big one happens. Building additional bridges and corridors would reduce congestion (people’s #1 priority) while also meeting future seismic needs. Portland has a dozen bridges over the Willamette River. We need more than two bridges over the Columbia River.
Let’s spend transportation dollars wisely. We can provide reasonably priced solutions that add vehicle capacity and seismic resilience. Most importantly, let’s not give in to the fear tactics of those attempting to sell us the $7.5 billion “bridge too low” with no reduction in traffic congestion.
The people want their transportation dollars used to help them save time and reduce congestion. The $7.5 billion currently targeted for the I-5 Bridge replacement project could pay for three or more seismically sound bridges over the Columbia River adding significantly to mobility needs in the region.