Wouldn't water get trapped between the new plastic culvert and the existing one? Could you ever get the seal strong enough to prevent that?
I am a complete novice in such matters, so i can't answer.
But I wonder if it would even matter though?
Is this a culvert drain for a pond or a culvert one drives over...ect?
Before placing the new black plastic culvert....
Maybe you could drill holes in galvanized bottom to let any water seep out.
Others can answer this better than me.
