Couple of years ago I lost the tailgate of my small trailer on the the the Pilchuck river bridge near where I live. i spotted what looked like an iron plate in the water. Last week I convinced my son to wade in since the water is low. There were 2 plates, 1" thick and about 20"x14" with hand hold cut outs . Maybe 120# or so. It took both of us with much difficulty to pull it up with a rope 20' from the water up to the bridge. I'll get the other some time, he wouldn't go back down for the other one (water too cold, iron too heavy), it's not going anywhere. I plan to make tools, swages and such.