On Tue, 25 Oct 2016 16:31:33 -0700, Oren wrote:

You mention a "big hollow" to fill. Perhaps consider taking dirty
fill, like broken concrete or even broken pavement and the later
taking on clean fill to finish off the top. If not building a house
foundation, the dirty fill could help you fill the space.

The "dirty fill" would add possibly pavement companies, demolition
companies, etc.

Finish the top off will clean fill. Tree Arborist can also give free
wood chip fill if they are local, instead of taking it to a dump.

Thanks. I thought about using crud at the bottom, but if I can get "the good
stuff", I don't see why I'd want chunks of concrete even if they're covered
by a layer of good stuff.

But if I did go for the cruddy stuff, what do you call that officially?
Is it called "dirty fill" as you quoted?

Or does it have a different name?