> Two piers were built in the 1940s, side by side

As far as I can tell, only one pier was built (using stainless steel rebar) and the presentation is comparing it to a hypothetical alternative as a theoretical exercise: "What if the Progreso Pier was built using carbon steel rebar?"

I think that was the prior pier maybe in the picture? The main pier only has one - it’s massive and goes forever. Pretty beefy construction too given that it takes a lot of heavy trucks.

Progreso - great pier and a great kiteboarding spot.