So much of it is what it is because of the existing narrowness of the ROW and all the water management and land acquisition considerations. The retaining wall and ROW width design work was such a huge chunk of the design costs that cure would be worse than disease with wholesale change orders. And physically impossible to change in a lot of places because of the constraints. The measurements are catalogued. You can even corroborate a lot of them yourself by taking one of those laser tape measures down to track level. On vast majority of the route the walls must be there to achieve minimum width...full-stop.
So I think Ayup's slide, like a lot of the slides in that presentation, presents something visually provocative without a lot of details to back it up. The types of retaining wall changes that can be done at actual savings would be small, discrete sections where a very surgical tweak sidesteps most of the change order penalties. Same sort of things we were talking about with station mods that are minimal-impact vs. those that fight a losing battle. Previous contractors weren't looking for the small surgical tweaks, and these guys think they can maybe tease a couple spots out for non-invasive reshaping.
Emphasis on "maybe" and "couple spots". It will not be dramatic because minimum width is what it is and so much of the ROW ain't. Temper expectations accordingly. As I said in my last post, it is improbable to impossible with the short time frame these contractors are being given that the state seriously thinks most of that $1B can come off the books due to pure civil engineering "redesign". Or that a reputable contractor would stake their reputation to such a short timeframe. So either they're lying to an improbably severe degree, or they are virtually certain that a majority of that $1B comes off from re-estimate of existing design and leaves the remainder within range of those discrete...surgical...non-invasive tweaks that do not incur all the substantial overhead of a major re-design.
The timeframe and presence of these contractors within that timeframe...does not compute at all unless they believe that.