The US Coast Guard has approved the design for the Interstate 5 bridge replacement over the Columbia River between Vancouver, Washington, and Portland, Oregon.
The new structure will be a fixed-span bridge with 4.9m vertical navigation clearance. The approval is a response to a navigation impact report submitted in October.
This approval will allow the Interstate Bridge Replacement Program (IBR) to finalise costs and work out a schedule. It can also select a design and a construction contractor.
IBR aims to replace two steel through-truss bridges that date from 1917 and 1958. Each also has a vertical draw lift span for shipping traffic.
The existing crossing rests on timber piles in soils that have been identified as vulnerable to liquefaction during an earthquake. IBR has said that a Cascadia Subduction Zone Earthquake would cause a catastrophic failure of the crossing. The new bridge project will feature mitigations such as soil stabilisation.
Last year, IBR sent residents postcards to collect data about journeys for use in calculating tolls (link opens in new tab).
