The answer to all of your questions can be found by visiting the following links. Please check your State Standards. For the State of California please refer to the following reference.
State of California Highway Design Manuals...
I did not know what the coefficient "K" stands for. If it refers to roughness coefficient than in terms of Manning's coefficient for roughness "n" the materials are considered equal. Therefore, there is no advantage of one material over the other.If you lined the DIP it would be better...
I have another option for you. On many embankments with 2 to 1 slopes, 20 to 30 feet high. The down drains have a conventional CMP "T" fitting attached to the end of the pipe. You could use this concept with a 36" by 36" x 36" T and attach a 36 inch flared and section to each side outlet to...
