https://www.codot.gov/news/2022/august/bridge-replacement-otero-county
Interesting quote: "Beginning the week of Sept. 19, assembly of the structures will begin at the project site. Aluminum box culverts were selected for the project over concrete box culverts as they can be fabricated in a shorter timeframe, are light weight and are able to be fully assembled on the roadway shoulder and lifted into place once the existing bridge is removed."
If CDOT is doing this, I have to think that CDOT is planning on turning over US 350 from the Pinon Canyon Maneuver Site entrance to LaJunta to Otero and Las Animas Counties once this is done. It is hard to justify having US 350 be a thru truck bypass if CDOT is going to, in effect, downgrade the road. Even if, in theory, the aluminium culverts are believed to be at least as strong as the timber bridges that are being replaced.
As we saw earlier this week with the I-10 detour lanes east of Desert Center, those aluminum culverts aren't enough to prevent a moderate monsoon flash flood. So much so, that Caltrans is using concrete box culverts to replace what was destroyed in that flood.
Alternatively, they could just be cheapskates!