I maintain 50 miles of rural roads. Have no idea how many culverts are involved, never tried to count them, over 100 I'm sure. I've used plastic since 1992. I'm talking about dual wall plastic, corrugated outside, smooth inside. In sizes from 12" up to 48". My provider builds 20' or 30' with bell/o-ring ends so they slip together without needing a band.
Only time I use galvanized steel is if I get into very large size above 48". Then it's more cost effective to use steel.
I have zero complaints regarding plastic.
Their lifespan is beyond my imagination. They are a lot less likely to wash out. I've not replaced any for that reason. Originally rumor had it that varmits would eat thru them, but I've never saw that.
Very easy to handle. Usually I'm working by myself. With a 36", if you have to put two pieces together you'll probably hafta throw some dirt on the first piece to hold it and then use your hoe to push the second one on. For smaller pipe I can usually slip them together by hand.
Up until two years ago I'd never had one burn out. I bragged about that to a local farmer a couple years ago and then lost one due to fire. We have a lot of idle farm land here, Conservation Reserve Program. One method of maintenance is to burn it off. This one had a thick layer of waterway grass that ran right up against one end. Got the plastic started burning and then used it as a chimney and burned out the entire culvert, 40' of 18". All that was left was small piles of melted molten plastic.
If you go plastic, you'll never go back!!!! Good luck with your project!!!
