As the community re-initiates the conversations about a replacement for the I-5 Bridge, I would like to suggest that we might consider starting this large, complicated engineering process from a blank sheet of paper and re-examine both the project requirements and approach. Are we trying to replace the current I-5 Bridge or find additional ways to augment the capacity for vehicles to cross the river? If a seismically sound alternative were found, is it necessary to remove the current I-5 Bridge? Is there a technology that could be used to cross the Columbia River and bypass I-5 chokepoints farther south?
Tunneling might be a solution. Tunnels minimize land use and are seismically secure. Tunneling under the river avoids the bridge height dilemma created by the fact that the I-5 corridor is a lowland-to-lowland crossing with a need to provide large shipping clearance. If we build a tunnel under the Columbia River, a tunnel could be used to create a bypass around the chokepoints in Portland.
By the way, the tunneling machine being used for the Seattle viaduct project is going to free up in 2019. The project had a rough start but is now sailing forward. By potentially leveraging that project’s experience and equipment, we may actually come up with an alternative that will make long-term sense. Tunneling may not be the least-expensive solution but it might provide the region with an approach to create a comprehensive north-to-south express solution that we all envision.
