The original article by Dom Marsh doesn't seem to be available online, but it recounts how the Cornerstone Housing Co-op in Leeds, UK, hired a digger to build these raised beds - using huge amounts of biomass like logs, brash, and grass and leaves buried in 4 «x18» trenches - and then
piling subsoil and topsoil back ontop.
Otherwise we wouldn't have such things as coal, or soil ending up as
subsoil and
piling tons and tons of the stuff
piling up above archaeological sites Worldwide would we?