the building site I'm looking to landscape has, I assume, reasonable topsoil on already; it's certainly well covered with grass, brambles and other vegetation. There is quite bit of work to do with levels, a terracing to install, hardcore to be laid for driveway and paths etc. I assume that I should set about scraping the soil into a pile, set the levels and terraces, then put the soil back.. but what do I do with all the crappy grass, weeds, brambles etc that is on there currently? Do I have to treat it with something chemically to kill it all off/rotavate it first or will being ripped up into a pile for a few months kill most of the flora off?