I live on Long Island and had cesspools replaced in early March 2012. We have had a few major rains this spring and summer and it looks like MAJOR ground settling is slowing down.

I need to add several yards of new top soil to refill and regrade my lawn then reseed. Question is is it preferable to do this in the fall (September/ October) or the spring?

I am asking for 2 reasons: Do I wait longer for further settling (minimal over the last 2 months) versus giving the new topsoil time itself to settle and let the new grass start.

ALSO I have a preponderance of weeds in the dirt where there is no grass. DO I have to use a grass/ weed killer before adding topsoil??

Much appreciate any input!!

Thanks :)