[cabmandone]

A 160 to 250 class is overkill for his project. A 14,000 to 18,000 lb machine (60-85 class) would more than do the job.

BTW Steve, when mowing the grass that acts as a filter strip, mow it taller. On my filter strip I was told to mow it no shorter than 6". In my area it was recommended to plant a certain type of grass (I don't recall what) when I finished sloping the banks. There's a guy around here (Liebrecht Manufacturing) that built a waterway ditcher that dresses waterways. It's not their pull behind but a fully self contained unit that actually drives in the ditch and resurfaces it.