Question re: soil prep before sod install
I don't know too much about gardening, but we're about to install some new sod in our backyard and I have a couple of questions:
We will need to fill in about 4-5 inches of soil to get a 100 sf patch of dirt level with the rest of the yard where there is already some grass. I live in Los Angeles and am trying to find some healthy soil with no contaminants (i.e. heavy metals). It seems like good topsoil is relatively easy to find, but from what I gather I shouldn't just add topsoil and then sod, without having some amendment. That said, I prefer not to have to amend the topsoil and do a lot of mixing. Rather, I want to get a pre-made blend that I can just add and then place the sod on top of that.
I read some other posts online that even the "organic" pre-mixed soils that you can buy at nurseries have all sorts of junk (i.e. construction debris, etc) in them which doesn't sound so great. I just want something safe and easy to use. I've also read that some places use sewage sludge even though they are called "organic." Sounds kind of scary, although perhaps it's nothing to worry about.
Does anyone have a suggestion for a good source/brand for soil in the LA or Southern California area (I don't mind driving an hour to get the good stuff)? Is there a recommendation for a pre-made formulation that would work for this application (i.e. a 50-50 compost/soil blend, or 70/30 or something else that's formulated for this application)? It seems like most people will just go to Home Depot and pick up whatever's there, but I figure I'd rather get the best option available for the lawn.
Thanks in advance for your help!