Okay, thanks for the info. There will be more than 3ft. of cover. The pipe will be galvanized steel and sitting directly on bedrock. So I will look for a road base material.
I am installing a culvert pipe to get across a subdivision drainage ditch. The subdivision has specified the culvert pipe diameter as 500mm. What type and how much cover should I put over this pipe? It was suggested to me to use a granualar A type gravel, and then compact it after. Does this...