lawn experiment: deep soil

I would like somebody with shallow soil to mark out a seven foot by seven foot section of their yard, dig two feet deep, and fill the space with logs and branches and dirt and whatever compostables they can find.  Finishing up with a four inch layer of dirt.    This should probably be mounded pretty good, because this area is gonna sink as the compostables compost.

Then, plant tall fescue. 

After the tall fescue is established, stop watering the whole lawn. 

Grass will normally go dormant in the summer, but I suspect that the tall fescue stay green all summer long (if mowed high) the second summer. 

*sigh*, I wish I had the digging equipment and amount of compostables to try this experiment...

How high do you suppose you'd need to mound the compostables mix before putting the finishing 4" of dirt?  Mound it to ground level?  A few inches?  A foot?  I guess I'd be trying not to have a small swimming pool after it shrinks...

-Jeremy

I think the mound should be slightly above grade before adding the topsoil.

I think it will sink over the years, but the question is:  how much will it sink?  And, if you did your whole yard this way, who cares if it sinks.  And if you leave your clippings (and there are lots of clippings) then wouldn't the top sorta smooth out over time all by itself?