The Oregon Department of Transportation (ODOT) published a report in 2014: Oregon Highways Seismic PLUS Report. The map shown here is one of many in the report that illustrate how large sections of western Oregon may be isolated for several years due to the failure of thousands of obsolete bridges and overpasses, as well as landslides and culverts. ODOT has developed a 50-year plan for seismically retrofitting or replacing these vulnerable transportation links, and estimates that the program will cost about $5 billion, or $100 million a year.
Cascadia Prepared advocates a much more aggressive program, in view of our analysis of CSZ quake intervals over the past 6,000 years. We also believe ODOT and local emergency managers should place a higher priority on lower-cost stopgap solutions, rather than the extremely expensive retrofitting and construction options. The solutions we recommend can emerge from an analysis of each “island” that might be formed as a result of CSZ quake damage. (“Island” is the term we use to describe an area whose links to adjoining areas are broken by road blockages, so that most traffic, including emergency vehicles, repair trucks, and passenger cars, are stranded there.) We believe it should be possible to identify fairly simple shortcuts around these blockages if preparations are made in advance. Examples of these shortcuts include:
- a rough gravel exit ramp from a limited-access highway to a road that crosses via an overpass that could fail in the quake, with a simple gate at each end to prevent usage except in emergency
- similarly, a rough graveled connection between a limited-access highway and a nearby frontage road
- nearby storage of materials needed to construct or place a temporary bridge over a waterway, where the existing bridge is likely to fail
These projects will require analysis and planning, involving government officials and affected landowners, but will be much less costly than regular bridge construction and rehab projects, with their lengthy and complex planning and contracting processes.
We need to remember that tens or hundreds of thousands of travelers will be stranded throughout the region on the new islands that will temporarily form, and unless we think ahead, there could be devastating conflicts between them and local residents.