Actual shop "garage" build.

[Bernica]

Permits slow? I hear that!!
We are on a septic system and they put you through the ringer on that one here, even building a garage. Been over a year now waiting for a permit.

Looks like those piles of dirt and gravel will be to fill the bathtub you built, right? When you get to final grade, do the vapor barrier, then sand, then another layer of vapor barrier. Don't cheap out on the reinforcing steel either. No mesh, use actual rebar somewhere around 12" or 16" on center each way There is also an ad mix for concrete called Fibermesh that gives you even more strength..
All IMHO and that's my 2c