I need to trench for sprinklers. The area is VERY sandy, amounting to sand
dunes, but with occasional rocks, big rocks, and rocks the size of
Cleveland.

I only need it to be 18" deep or so, and it will be about 800 feet or so.

What is the trenching rate for a Ditch Witch in sandy soil? I know
everything won't go perfectly, but think the sandy soil will be fast in most
areas, and I do have a couple of filled areas where it may be gravel and
small rocks.

I've never used one of these. Any hints or caveats?

Steve