https://www.clarkcountytoday.com/news/ib...aging-the-project-to-replace-i-5-bridge/
This doesn't bode well for cost control. Also, 15 years?!
The article also has an interesting breakdown of component cost. One of the problems with mega-projects like this is that they end up getting stuffed full of components that, on their own, would never pass a benefit-cost analysis. For example:
$550-$850 million to rebuild the Mill Plain interchange. The new interchange will be exactly the same as the current interchange. The only difference is the bridge will be wider, allowing a future 10-lane configuration. The present bridge would support 8 lanes. Even if it were to be granted that we want a 10-lane width here, that's only useful capacity if it feeds into a widened I-5 in North and downtown Portland. That's decades and billions of dollars away, at the very least. It would make far more sense to replace this bridge when it reaches the end of its service life in 40 years (it was built in the 80s). This scope amounts to paying nearly $1 billion (potentially) for 20-ft shoulders instead of 8-ft shoulders at a single bridge.
$180-$270 million for "Washington North". This section of highway is already wide enough for 10 lanes. The scope is entirely about braiding the 4th Plain exit ramp with the SR500 onramp. Granted, the exits are a bit close. But this is just a huge cost for a very minor benefit. If it really is a concern, removing the 4th Plain interchange--there are interchanges within 3/4 miles in each direction--would accomplish the same goal at a fraction of the cost.
$240-$360 million for rebuilding the Marine Dr. interchange. I'm sure just looking at this interchange gives a traffic engineer an aneurysm. But it's a functional interchange, and the bridge is only 40 years old. Rebuilding this interchange, at this cost, would never be considered if it were an independent project.
I could go on. Replacing the Portland Harbor bridge, rebuilding I-5 for miles in each direction. All told, I think half the project cost is going to interchange improvements with very questionable benefit-cost ratios and extra-wide shoulders that
might be useful in 40 years. I get the case for building bridges with some extra length/width. It's a small extra cost for future flexibility. But this mindset of replacing a bunch of other bridges and infrastructure decades before it's due just so the extra space can sit empty for decades makes no sense.