I just read your description reg box culvert, head wall etc.
Professionally I'm a transportation CAD engineer and completed many NHAI project till yet.
I'm working Box culvert, pipe culvert, slab culvert, MNBR, VUP, Airport heavy Structure for loading Aircrafts.
GAD Drawing / Detailed drawing / Fabrication Drawing
Required a site input like. invert level, ground level, FRL etc.