(Portland, OR) -- Every five years, Multnomah County produces a Hazard Mitigation report. It assesses potential risks during a major disaster, like a magnitude nine Cascadia subduction zone earthquake. Liquid fuel storage tanks along the Willamette and Columbia Rivers have been a major concern. Now, they're adding airborne gasses to the list. They don't know how much of a risk those tanks pose. The listing in the report will allow the county to apply for federal grants to study the problem and determine solutions.