AutoCAD Civil 3D

[#1]

Am calculating side fill volume for a trunk road, in our design we are providing a 1:2 V:H embankment slope when the road embankment is higher than 2meters and put a side fill (top soil )ontop of the embankment slopes at a slope of 1:4 as showm in the attached photo, am looking for a beter/easier way to calculate the volume of side fill, curently what i do is to create two corridors one at a slope of 1:2 and the other at a slope of 1:4 and calculate the difference btn two surfaces but this method is tideous and time consuming.

Any help is appreciated.