The bridge needs to be built down river to cross over and come out approximately at Kalama, another alternative to bypass from going through downtown Portland.
The cost of securing property for doing the I-5 corridor through Portland is prohibitive, plus the years of construction disruption would be too costly on the general public without first building an alternative route around Portland.
The Oregon Dump Truck Association proposed this back in 1995. It was just laughed at then but is very practical today.
Larry Morrison, Tualatin, Oregon