How do I prep my yard for 18" of new soil to replace what washed away? I'd like to add grass seed, too.

Question

The soil washed away into the neighbor's back yard when the water main broke and the ground is now very slanted. There are some weeds. It's about 105 degrees here now.

Answer 1

there are a lot of variables to answer your question.

If you want soil drainage, start off with an initial fill of pea gravel or sharp sand (this is used for stucco), and bring it up to within 1-2 inches below grade (the desired height of the lawn).  

on top of that, after placing/plumbing any sprinkler system heads, pipe, manifolds, valves, add some top soil (usually dirt mixed with compost or manure, purchased from a rock yard or garden center in bulk (by the dump truck load)).  

water, then rake the area with a gravel rake, using the tines to texture the surface, to which you will seed your grass, or apply sod.

I don't know your area, but if in the desert, Emerald Carpet is a nice low growing fine fescue grass seed, somewhat heat tolerant.  doesn't grow really tall, and cuts down mowing chores.  also, sow some white clover seed (NO DICHONDRA) in with the grass seed.  this is very heat tolerant, not prone to brownout or burns, and improves the soil in general.  Sow the seed in with mulch/dirt blend (ammend, or other Kellogg fine grind product) or cow manure (strongest nasal decongestant you can get without a prescription).  water 4 times a day until grass is established.

Once established, sow more soil ammendments, cow manure, mulch, and/or triple balanced chemical fertilizer (15-15-15), as well as some red worms (earthworms).  The idea here is to build an organic base over a 2-3 year period, about 3 inches thick, that will help your grass, and also serve as a reserve sponge to soak up and store water reserves for your lawn's future use throughout the day.

If you can wait for seeding the lawn, wait until the temp drops to 90.  if not, roll sod may be the better choice to initiate a lawn during high temp days.

Answer 2

there is no prep work to be done prior to getting the soil after you get the soil is when the work begins

Answer 3

You don't plant the grass until the soil has been replaced.  18" is a good depth for improving the soil.  Manure, leaves, non-wood compost would all be great to till into the new soil. I got horse manure from a local stable for free to add to my soil.  But you can get good steer manure from the nursery.  Just plan that the soil will settle some after a few years.  Once you plant the grass...if seed...you will need to keep the surface wet for about two weeks so you may want to wait for it to cool off or you will be standing there with a hose all day(and at 105 you should wake up and feed the lawn water at night).  ...if turf...You will not need to water as often but be sure to water deep to get the roots into the new soil.