This is a picture of a culvert on an old logging railway grade that has been re-activated for trucks. It appears to be an old boiler or some such thing. My guide was telling me these types of structures are quite common on the old Bloedel, Stewart & Welch r/w south of Port Alberni, BC.
One of my uncles used an old water tank for a culvert. It was more handy at the time than buying the usual culvert. Logs have been traveling over it to the mills for over 40 years now. They have also used two or three logs in a stream bed and then built a road over them letting the water flow through the gaps between the logs. I doubt it would be an acceptable practice today. One of those examples still in use after 40 years too.