Design Options

There are severe height limitations at the I5 site:

The drawbridge (bascule) option is being ignored because of claims that they are forbidden on interstate highways. Here are some drawbridges on interstate highways.

The last CRC proposal was for a bridge of a design that had never been built before (see IRP below). A bridge review team determined that to build such a design would require extensive, expensive engineering work because of the uncertainties in new design.

Independent Review Panel report

The Independent Review Panel report shows what was wrong with the CRC project.  Here is the brief description of why the chosen bridge design is flawed (from page 12:

Since the publication of the Draft EIS the LPA has been modified considerably. Most significant is the change in structure type for the main bridges across the Columbia River. This change from a closed box segmental design to the open-web Stacked Transit/Highway Bridge (STHB) approach is substantial. It reflects a departure from a standard structure type used across the nation to one that has never been built anywhere in the world, requiring extensive testing and engineering to determine viability.

The STHB accommodates light rail transit within one of the bridges and the open-web design eliminates the confined attributes of segmental box configuration. The IRP determined several key things about the open-web

STHB including:

 No Cost Estimate Validation Process (CEVP) has been done

on the current design. Past CEVP efforts were conducted on

a version of the bridge no longer under consideration.

 The earlier Constructability Workshop reviewed a previous

version of the bridge as well.

 Current cost estimates are for a previous bridge type and may

not reflect the actual cost of the STHB.

 FHWA and others will require substantial testing and

evaluation of the open-web STHB prior to final approval.