JKB, I believe those aluminum ones have rubber seals.
I believe it is sealed somehow, but never paid much attention, as that is not the part of the dam I was dealing with.
I do have some CAD files from the PE firm who noodled this up. It only shows concrete and iron for that part and very little on the aluminum stop log's. I wish I took a close up picture when I was there, because I thought it was pretty neat. I do have all the mechanical details of the hydraulic side tho.
That's that 8400 acre lake up north I'm messing with on occasion.
